slindal

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Studies of J/ψ production at forward rapidity in Pb–Pb collisions at √sNN−−− = 5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2020:41, s. 1–30. doi: 10.1007/JHEP02(2020)041. Fulltekst i vitenarkiv Vis sammendrag

  The inclusive J/ψ production in Pb–Pb collisions at the center-of-mass energy per nucleon pair √sNN = 5.02 TeV, measured with the ALICE detector at the CERN LHC, is reported. The J/ψ meson is reconstructed via the dimuon decay channel at forward rapidity (2.5 < y < 4) down to zero transverse momentum. The suppression of the J/ψ yield in Pb–Pb collisions with respect to binary-scaled pp collisions is quantified by the nuclear modification factor (RAA). The RAA at √sNN = 5.02 TeV is presented and compared with previous measurements at √sNN = 2.76 TeV as a function of the centrality of the collision, and of the J/ψ transverse momentum and rapidity. The inclusive J/ψ RAA shows a suppression increasing toward higher transverse momentum, with a steeper dependence for central collisions. The modification of the J/ψ average transverse momentum and average squared transverse momentum is also studied. Comparisons with the results of models based on a transport equation and on statistical hadronization are carried out.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Global polarization of Λ Λ hyperons in Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV. Physical Review C. ISSN 2469-9985. 101(4), s. 1–14. doi: 10.1103/PhysRevC.101.044611. Fulltekst i vitenarkiv Vis sammendrag

  The global polarization of the and hyperons is measured for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon’s transverse momentum (pT ) for the range of centrality 5–50%, 0.5 < pT < 5 GeV/c, and rapidity |y| < 0.5. The hyperon global polarization averaged for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV is found to be consistent with zero, PH (%) ≈ 0.01 ± 0.06 (stat.) ± 0.03 (syst.) in the collision centrality range 15–50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). K∗(892)0 and φ(1020) production at midrapidity in pp collisions at √s=8 TeV. Physical Review C. ISSN 2469-9985. 102:024912(2), s. 1–15. doi: 10.1103/PhysRevC.102.024912. Fulltekst i vitenarkiv Vis sammendrag

  The production of K∗(892)0 and φ(1020) in pp collisions at √s = 8 TeV was measured by using Run 1 data collected by the ALICE collaboration at the CERN Large Hadron Collider (LHC). The pT-differential yields d2N/dyd pT in the range 0 < pT < 20 GeV/c for K∗0 and 0.4 < pT < 16 GeV/c for φ have been measured at midrapidity, |y| < 0.5. Moreover, improved measurements of the K∗0 (892) and φ(1020) at √s = 7 TeV are presented. The collision energy dependence of pT distributions, pT-integrated yields, and particle ratios in inelastic pp collisions are examined. The results are also compared with different collision systems. The values of the particle ratios are found to be similar to those measured at other LHC energies. In pp collisions a hardening of the particle spectra is observed with increasing energy, but at the same time it is also observed that the relative particle abundances are independent of the collision energy. The pT-differential yields of K∗0 and φ in pp collisions at √s = 8 TeV are compared with the expectations of different Monte Carlo event generators.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Measurement of electrons from heavy-flavour hadron decays as a function of multiplicity in p-Pb collisions at √sNN−−− = 5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2020:77(2), s. 1–32. doi: 10.1007/JHEP02(2020)077. Fulltekst i vitenarkiv Vis sammendrag

  The multiplicity dependence of electron production from heavy-flavour hadron decays as a function of transverse momentum was measured in p-Pb collisions at √sNN = 5.02 TeV using the ALICE detector at the LHC. The measurement was performed in the centre-of-mass rapidity interval −1.07 < ycms< 0.14 and transverse momentum interval 2 < pT< 16 GeV/c. The multiplicity dependence of the production of electrons from heavy-flavour hadron decays was studied by comparing the pT spectra measured for different multiplicity classes with those measured in pp collisions (QpPb) and in peripheral p-Pb collisions (Qcp). The QpPb results obtained are consistent with unity within uncertainties in the measured pT interval and event classes. This indicates that heavy-flavour decay electron production is consistent with binary scaling and independent of the geometry of the collision system. Additionally, the results suggest that cold nuclear matter effects are negligible within uncertainties, in the production of heavy-flavour decay electrons at midrapidity in p-Pb collisions.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 52 forfattere av denne artikkelen] (2020). Measurement of Λ (1520) production in pp collisions at √s=7 TeV and p–Pb collisions at √sNN=5.02 TeV. European Physical Journal C. ISSN 1434-6044. 80(2), s. 1–19. doi: 10.1140/epjc/s10052-020-7687-2. Fulltekst i vitenarkiv Vis sammendrag

  The production of the Λ(1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at √s=7 TeV and in p–Pb collisions at √sNN=5.02 TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ(1520) →pK− and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, K0S, p, Λ) describes the shape of the Λ(1520) transverse momentum distribution up to 3.5 GeV/c in p–Pb collisions. In the framework of this model, this observation suggests that the Λ(1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ(1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the Λ(1520) yield.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Production of charged pions, kaons, and (anti-)protons in Pb-Pb and inelastic pp collisions at √sNN=5.02 TeV. Physical Review C. ISSN 2469-9985. 101:044907(4), s. 1–27. doi: 10.1103/PHYSREVC.101.044907. Fulltekst i vitenarkiv Vis sammendrag

  Midrapidity production of π±, K±, and (¯p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √sNN=5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum (pT) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0–90%. The comparison of the pT-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √sNN=2.76 TeV show no significant energy dependence. Blast-wave fits of the pT spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π, K/π) as a function of pT show pronounced maxima at pT≈3 GeV/c in central Pb-Pb collisions. At high pT, particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √sNN=2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high pT and compatible with measurements at √sNN=2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Scattering studies with low-energy kaon-proton femtoscopy in proton-proton collisions at the LHC. Physical Review Letters. ISSN 0031-9007. 124(9), s. 1–13. doi: 10.1103/PhysRevLett.124.092301. Fulltekst i vitenarkiv Vis sammendrag

  The study of the strength and behavior of the antikaon-nucleon (¯KN) interaction constitutes one of the key focuses of the strangeness sector in low-energy quantum chromodynamics (QCD). In this Letter a unique high-precision measurement of the strong interaction between kaons and protons, close and above the kinematic threshold, is presented. The femtoscopic measurements of the correlation function at low pair-frame relative momentum of (K+p⊕K−¯p) and (K−p⊕K+¯p) pairs measured in pp collisions at √s=5, 7, and 13 TeV are reported. A structure observed around a relative momentum of 58 MeV/c in the measured correlation function of (K−p⊕K+¯p) with a significance of 4.4σ constitutes the first experimental evidence for the opening of the (¯K0n⊕K0¯n) isospin breaking channel due to the mass difference between charged and neutral kaons. The measured correlation functions have been compared to Jülich and Kyoto models in addition to the Coulomb potential. The high-precision data at low relative momenta presented in this work prove femtoscopy to be a powerful complementary tool to scattering experiments and provide new constraints above the ¯KN threshold for low-energy QCD chiral models.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Exploration of jet substructure using iterative declustering in pp and Pb–Pb collisions at LHC energies. Physics Letters B. ISSN 0370-2693. 802:135227, s. 1–12. doi: 10.1016/j.physletb.2020.135227. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at √s = 7 TeV and central Pb–Pb collisions at √sNN = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the zg, and its dependence on the opening angle, in both pp and Pb–Pb collisions. We also present the measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb–Pb collisions, we observe a suppression of symmetric splittings at large opening angles and an enhancement of splittings at small opening angles relative to pp collisions, with no significant modification of the number of splittings. The results are compared to predictions from various Monte Carlo event generators to test the role of important concepts in the evolution of the jet in the medium such as colour coherence.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Measurement of strange baryon–antibaryon interactions with femtoscopic correlations. Physics Letters B. ISSN 0370-2693. 802:135223, s. 1–14. doi: 10.1016/j.physletb.2020.135223. Fulltekst i vitenarkiv Vis sammendrag

  Two-particle correlation functions were measured for pp, p, p, and pairs in Pb–Pb collisions at √sNN = 2.76 TeV and √sNN = 5.02 TeV recorded by the ALICE detector. From a simultaneous fit to all obtained correlation functions, real and imaginary components of the scattering lengths, as well as the effective ranges, were extracted for combined p and p pairs and, for the first time, for pairs. Effective averaged scattering parameters for heavier baryon–antibaryon pairs, not measured directly, are also provided. The results reveal similarly strong interaction between measured baryon–antibaryon pairs, suggesting that they all annihilate in the same manner at the same pair relative momentum k∗. Moreover, the reported significant non-zero imaginary part and negative real part of the scattering length provide motivation for future baryon–antibaryon bound state searches.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at √sNN=5.02 TeV. Physics Letters B. ISSN 0370-2693. 800:135043, s. 1–13. doi: 10.1016/j.physletb.2019.135043. Fulltekst i vitenarkiv Vis sammendrag

  The measurement of the deuteron and anti-deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-offlight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Multiplicity dependence of (multi-)strange hadron production in proton-proton collisions at √s = 13 TeV. European Physical Journal C. ISSN 1434-6044. 80:167, s. 1–26. doi: 10.1140/epjc/s10052-020-7673-8. Fulltekst i vitenarkiv Vis sammendrag

  The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity (|y|<0.5) are measured in proton-proton collisions at s√ = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of K0S, Λ, Ξ, and Ω increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb–Pb collisions at √sNN=5.02 TeV. Physics Letters B. ISSN 0370-2693. 804:135377, s. 1–15. doi: 10.1016/j.physletb.2020.135377. Fulltekst i vitenarkiv Vis sammendrag

  The differential invariant yield as a function of transverse momentum (pT) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0–10%), semi-central (30–50%) and peripheral (60–80%) lead–lead (Pb–Pb) collisions at √sNN = 5.02 TeV in the pT intervals 0.5–26 GeV/c (0–10% and 30–50%) and 0.5–10 GeV/c (60–80%). The production cross section in proton–proton (pp) collisions at √s = 5.02 TeV was measured as well in 0.5 < pT < 10 GeV/c and it lies close to the upper band of perturbative QCD calculation uncertainties up to pT = 5 GeV/c and close to the mean value for larger pT. The modification of the electron yield with respect to what is expected for an incoherent superposition of nucleon–nucleon collisions is evaluated by measuring the nuclear modification factor RAA. The measurement of the RAA in different centrality classes allows in-medium energy loss of charm and beauty quarks to be investigated. The RAA shows a suppression with respect to unity at intermediate pT, which increases while moving towards more central collisions. Moreover, the measured RAA is sensitive to the modification of the parton distribution functions (PDF) in nuclei, like nuclear shadowing, which causes a suppression of the heavy-quark production at low pT in heavy-ion collisions at LHC.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2020). Measurement of the (anti-)3He elliptic flow in Pb–Pb collisions at √sNN=5.02 TeV. Physics Letters B. ISSN 0370-2693. 805:135414, s. 1–14. doi: 10.1016/j.physletb.2020.135414. Fulltekst i vitenarkiv Vis sammendrag

  The elliptic flow (v2) of (anti-)3He is measured in Pb–Pb collisions at √sNN = 5.02 TeV in the transversemomentum (pT) range of 2–6 GeV/c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low pT, as expected from relativistic hydrodynamics. The violation of the scaling of v2 with the number of constituent quarks at low pT, already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-)3He. The elliptic flow of (anti-)3He is underestimated by the Blast-Wave model and overestimated by a simple coalescence approach based on nucleon scaling. The elliptic flow of (anti-)3He measured in the centrality classes 0–20% and 20–40% is well described by a more sophisticated coalescence model where the phasespace distributions of protons and neutrons are generated using the iEBE-VISHNU hybrid model with AMPT initial conditions.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Direct photon elliptic flow in Pb–Pb collisions at √sNN=2.76 TeV. Physics Letters B. ISSN 0370-2693. 789, s. 308–322. doi: 10.1016/j.physletb.2018.11.039. Fulltekst i vitenarkiv Vis sammendrag

  The elliptic flow of inclusive and direct photons was measured at mid-rapidity in two centrality classes 0–20% and 20–40% in Pb–Pb collisions at TeV by ALICE. Photons were detected with the highly segmented electromagnetic calorimeter PHOS and via conversions in the detector material with the pairs reconstructed in the central tracking system. The results of the two methods were combined and the direct-photon elliptic flow was extracted in the transverse momentum range . A comparison to RHIC data shows a similar magnitude of the measured direct-photon elliptic flow. Hydrodynamic and transport model calculations are systematically lower than the data, but are found to be compatible.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe–Xe collisions at √sNN=5.44 TeV. Physics Letters B. ISSN 0370-2693. 790, s. 35–48. doi: 10.1016/j.physletb.2018.12.048. Fulltekst i vitenarkiv Vis sammendrag

  In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, dNch/dη, and total charged-particle multiplicity, Ntot ch , in Xe–Xe collisions at a centre-of-mass energy per nucleon–nucleon pair of √sNN =5.44 TeV. The measurements are performed as a function of collision centrality over a wide pseudorapidity range of −3.5 < η < 5. The values of dNch/dη at mid-rapidity and Ntot ch for central collisions, normalised to the number of nucleons participating in the collision (Npart) as a function of √sNN follow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of Npart, and up to the 5% most central collisions the trends are the same as the ones observed in Pb–Pb at a similar energy. For more central collisions, the Xe–Xe scaled multiplicities exceed those in Pb–Pb for a similar Npart. The results are compared to phenomenological models and theoretical calculations based on different mechanisms for particle production in nuclear collisions. All considered models describe the data reasonably well within 15%.

• Acharya, Shreyasi; Adamová, Dagmar; Adler, A.; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Charged jet cross section and fragmentation in proton-proton collisions at √s=7  TeV. Physical Review D. ISSN 2470-0010. 99:012016(1), s. 1–16. doi: 10.1103/PhysRevD.99.012016. Fulltekst i vitenarkiv Vis sammendrag

  We report the differential charged jet cross section and jet fragmentation distributions measured with the ALICE detector in proton-proton collisions at a center-of-mass energy √s=7  TeV. Jets with pseudorapidity|η|<0.5 are reconstructed from charged particles using the anti-kT jet-finding algorithm with a resolution parameter R=0.4. The jet cross section is measured in the transverse momentum interval 5≤pch jetT<100  GeV/c. Jet fragmentation is studied measuring the scaled transverse momentum spectra of the charged constituents of jets in four intervals of jet transverse momentum between 5 and 30  GeV/c. The measurements are compared to calculations from the pythia model as well as next-to-leading-order perturbative QCD calculations with powheg+pythia8. The charged jet cross section is well described by powheg for the entire measured range of pch jetT. For pch jetT>40  GeV/c, the pythia calculations also agree with the measured charged jet cross section. pythia6 simulations describe the fragmentation distributions to 15%. Larger discrepancies are observed for pythia8.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Dielectron and heavy-quark production in inelastic and high-multiplicity proton–proton collisions at √s=13 TeV. Physics Letters B. ISSN 0370-2693. 788, s. 505–518. doi: 10.1016/j.physletb.2018.11.009. Fulltekst i vitenarkiv Vis sammendrag

  The measurement of dielectron production is presented as a function of invariant mass and transverse momentum () at midrapidity () in proton–proton (pp) collisions at a centre-of-mass energy of TeV. The contributions from light-hadron decays are calculated from their measured cross sections in pp collisions at TeV or 13 TeV. The remaining continuum stems from correlated semileptonic decays of heavy-flavour hadrons. Fitting the data with templates from two different MC event generators, PYTHIA and POWHEG, the charm and beauty cross sections at midrapidity are extracted for the first time at this collision energy: and using PYTHIA simulations and and for POWHEG. These values, whose uncertainties are fully correlated between the two generators, are consistent with extrapolations from lower energies. The different results obtained with POWHEG and PYTHIA imply different kinematic correlations of the heavy-quark pairs in these two generators. Furthermore, comparisons of dielectron spectra in inelastic events and in events collected with a trigger on high charged-particle multiplicities are presented in various intervals. The differences are consistent with the already measured scaling of light-hadron and open-charm production at high charged-particle multiplicity as a function of . Upper limits for the contribution of virtual direct photons are extracted at 90% confidence level and found to be in agreement with pQCD calculations.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of charged jet cross section in pp collisions at √s=5.02  TeV. Physical Review D. ISSN 2470-0010. 100:092004(9), s. 1–22. doi: 10.1103/PhysRevD.100.092004. Fulltekst i vitenarkiv Vis sammendrag

  The cross section of jets reconstructed from charged particles is measured in the transverse momentum range of 5 < p T < 100     GeV / c in p p collisions at the center-of-mass energy of √ s = 5.02     TeV with the ALICE detector. The jets are reconstructed using the anti- k T algorithm with resolution parameters R = 0.2 , 0.3, 0.4, and 0.6 in the pseudorapidity range | η | < 0.9 − R . The charged jet cross sections are compared with the leading-order (LO) and to next-to-leading-order (NLO) perturbative quantum chromodynamics (pQCD) calculations. It is found that the NLO calculations agree better with the measurements. The cross section ratios for different resolution parameters are also measured. These ratios increase from low p T to high p T and saturate at high p T , indicating that jet collimation is larger at high p T than at low p T . These results provide a precision test of pQCD predictions and serve as a baseline for the measurement in Pb-Pb collisions at the same energy to quantify the effects of the hot and dense medium created in heavy-ion collisions at the LHC.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of Υ(1S) elliptic flow at forward rapidity in Pb-Pb collisions at √sNN=5.02  TeV. Physical Review Letters. ISSN 0031-9007. 123:192301(19), s. 1–13. doi: 10.1103/PhysRevLett.123.192301. Fulltekst i vitenarkiv Vis sammendrag

  The first measurement of the Υ ( 1 S ) elliptic flow coefficient ( v 2 ) is performed at forward rapidity ( 2.5 < y < 4 ) in Pb–Pb collisions at √ s NN = 5.02 TeV with the ALICE detector at the LHC. The results are obtained with the scalar product method and are reported as a function of transverse momentum ( p T ) up to 15 GeV / c in the 5%–60% centrality interval. The measured Υ ( 1 S ) v 2 is consistent with 0 and with the small positive values predicted by transport models within uncertainties. The v 2 coefficient in 2 < p T < 15 GeV / c is lower than that of inclusive J / ψ mesons in the same p T interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with a scenario in which the Υ ( 1 S ) production in Pb–Pb collisions at LHC energies is dominated by dissociation limited to the early stage of the collision, whereas in the J / ψ case there is substantial experimental evidence of an additional regeneration component.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of the inclusive isolated photon production cross section in p p collisions at √s=7 TeV. European Physical Journal C. ISSN 1434-6044. 79:896, s. 1–20. doi: 10.1140/epjc/s10052-019-7389-9. Fulltekst i vitenarkiv Vis sammendrag

  The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of s√= 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of |η|<0.27 in pseudorapidity and a transverse momentum range of 10<pγT<60 GeV/c. The result extends the pT coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller pT. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A. & Adolfsson, Jonatan [Vis alle 51 forfattere av denne artikkelen] (2019). Jet fragmentation transverse momentum measurements from di-hadron correlations in s√=7 TeV pp and √sNN=5.02 TeV p–Pb collisions. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:169, s. 1–24. doi: 10.1007/JHEP03(2019)169. Fulltekst i vitenarkiv Vis sammendrag

  The transverse structure of jets was studied via jet fragmentation transverse momentum (jT) distributions, obtained using two-particle correlations in proton-proton and proton-lead collisions, measured with the ALICE experiment at the LHC. The highest transverse momentum particle in each event is used as the trigger particle and the region 3 < pTt < 15GeV/c is explored in this study. The measured distributions show a clear narrow Gaussian component and a wide non-Gaussian one. Based on Pythia simulations, the narrow component can be related to non-perturbative hadronization and the wide component to quantum chromodynamical splitting. The width of the narrow component shows a weak dependence on the transverse momentum of the trigger particle, in agreement with the expectation of universality of the hadronization process. On the other hand, the width of the wide component shows a rising trend suggesting increased branching for higher transverse momentum. The results obtained in pp collisions at √s=7 TeV and in p–Pb collisions at √sNN=5.02 TeV are compatible within uncertainties and hence no significant cold nuclear matter effects are observed. The results are compared to previous measurements from CCOR and PHENIX as well as to Pythia 8 and Herwig 7 simulations.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Event-shape engineering for the D-meson elliptic flow in mid-central Pb-Pb collisions at √sNN=5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:150, s. 1–36. doi: 10.1007/JHEP02(2019)150. Fulltekst i vitenarkiv Vis sammendrag

  The production yield of prompt D mesons and their elliptic flow coefficient v2 were measured with the Event-Shape Engineering (ESE) technique applied to mid-central (10–30% and 30–50% centrality classes) Pb-Pb collisions at the centre-of-mass energy per nucleon pair √sNN=5.02 TeV, with the ALICE detector at the LHC. The ESE technique allows the classification of events, belonging to the same centrality, according to the azimuthal anisotropy of soft particle production in the collision. The reported measurements give the opportunity to investigate the dynamics of charm quarks in the Quark-Gluon Plasma and provide information on their participation in the collective expansion of the medium. D mesons were reconstructed via their hadronic decays at mid-rapidity, |η| < 0.8, in the transverse momentum interval 1 < pT < 24 GeV/c. The v2 coefficient is found to be sensitive to the event-shape selection confirming a correlation between the D-meson azimuthal anisotropy and the collective expansion of the bulk matter, while the per-event D-meson yields do not show any significant modification within the current uncertainties.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2019). Relative particle yield fluctuations in Pb--Pb collisions at √sNN=2.76 TeV. European Physical Journal C. ISSN 1434-6044. 79:236(3), s. 1–14. doi: 10.1140/epjc/s10052-019-6711-x. Fulltekst i vitenarkiv Vis sammendrag

  First results on K/π, p/π and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in Pb--Pb collisions at sNN−−−√=2.76 TeV. The observable νdyn, which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for p/π show a change of sign in νdyn from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and νdyn exhibits a change in sign for p/π and K/p.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2019). Azimuthal Anisotropy of Heavy-Flavor Decay Electrons in p-Pb Collisions at √sNN=5.02  TeV. Physical Review Letters. ISSN 0031-9007. 122:072301(7), s. 1–13. doi: 10.1103/PhysRevLett.122.072301. Fulltekst i vitenarkiv Vis sammendrag

  Angular correlations between heavy-flavor decay electrons and charged particles at midrapidity ( | η | < 0.8 ) are measured in p -Pb collisions at √ s N N = 5.02     TeV . The analysis is carried out for the 0%–20% (high) and 60%–100% (low) multiplicity ranges. The jet contribution in the correlation distribution from high-multiplicity events is removed by subtracting the distribution from low-multiplicity events. An azimuthal modulation remains after removing the jet contribution, similar to previous observations in two-particle angular correlation measurements for light-flavor hadrons. A Fourier decomposition of the modulation results in a positive second-order coefficient ( v 2 ) for heavy-flavor decay electrons in the transverse momentum interval 1.5 < p T < 4     GeV / c in high-multiplicity events, with a significance larger than 5 σ . The results are compared with those of charged particles at midrapidity and those of inclusive muons at forward rapidity. The v 2 measurement of open heavy-flavor particles at midrapidity in small collision systems could provide crucial information to help interpret the anisotropies observed in such systems.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Production of muons from heavy-flavour hadron decays in pp collisions at √s = 5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:8(9), s. 1–27. doi: 10.1007/JHEP09(2019)008. Fulltekst i vitenarkiv Vis sammendrag

  Production cross sections of muons from semi-leptonic decays of charm and beauty hadrons were measured at forward rapidity (2.5 < y < 4) in proton-proton (pp) collisions at a centre-of-mass energy s√ = 5.02 TeV with the ALICE detector at the CERN LHC. The results were obtained in an extended transverse momentum interval, 2 < pT< 20 GeV/c, and with an improved precision compared to previous measurements performed in the same rapidity interval at centre-of-mass energies s√ = 2.76 and 7 TeV. The pT- and y-differential production cross sections as well as the pT-differential production cross section ratios between different centre-of-mass energies and different rapidity intervals are described, within experimental and theoretical uncertainties, by predictions based on perturbative QCD.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Inclusive J/ψ production at mid-rapidity in pp collisions at √s = 5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:84, s. 1–26. doi: 10.1007/JHEP10(2019)084. Fulltekst i vitenarkiv Vis sammendrag

  Inclusive J/ψ production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of √ s = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity (|y| < 0.9) in the dielectron decay channel down to zero transverse momentum pT, using a data sample corresponding to an integrated luminosity of Lint = 19.4 ± 0.4 nb−1 . The measured pT-integrated inclusive J/ψ production cross section is dσ/dy = 5.64 ± 0.22(stat.) ± 0.33(syst.) ± 0.12(lumi.) µb. The pT-differential cross section d2σ/dpTdy is measured in the pT range 0–10 GeV/c and compared with state-ofthe-art QCD calculations. The J/ψ hpTi and hp 2 T i are extracted and compared with results obtained at other collision energies.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). First observation of an attractive interaction between a proton and a cascade baryon. Physical Review Letters. ISSN 0031-9007. 123:112002(11), s. 1–13. doi: 10.1103/PhysRevLett.123.112002. Fulltekst i vitenarkiv Vis sammendrag

  This Letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle correlations of combined p-Ξ− ⊕ p¯-Ξ¯ þ pairs measured in p-Pb collisions at √sNN p ¼ 5.02 TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a standard deviation in the range [3.6, 5.3] is found. Since the measured p-Ξ− ⊕ p¯-Ξ¯ þ correlation is significantly enhanced with respect to the Coulomb prediction, the presence of an additional, strong, attractive interaction is evident. The data are compatible with recent lattice calculations by the HAL-QCD Collaboration, with a standard deviation in the range [1.8, 3.7]. The lattice potential predicts a shallow repulsive Ξ− interaction within pure neutron matter and this implies stiffer equations of state for neutron-rich matter including hyperons. Implications of the strong interaction for the modeling of neutron stars are discussed.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). 3Λh and 3‾Λ‾h lifetime measurement in Pb–Pb collisions at √sNN = 5.02 TeV via two-body decay. Physics Letters B. ISSN 0370-2693. 797:134905, s. 1–12. doi: 10.1016/j.physletb.2019.134905. Fulltekst i vitenarkiv Vis sammendrag

  An improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb–Pb collisions at sNN=5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the dN/d(ct) spectrum. The measured value, τ=242−38+34 (stat.) ± 17 (syst.) ps, is compatible with representative theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander & Adolfsson, Jonatan [Vis alle 51 forfattere av denne artikkelen] (2019). Calibration of the photon spectrometer PHOS of the ALICE experiment. Journal of Instrumentation (JINST). 14(5), s. 1–31. doi: 10.1088/1748-0221/14/05/P05025. Fulltekst i vitenarkiv Vis sammendrag

  The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at √ s = 13 TeV. After applying all corrections, the achieved mass resolutions for π 0 and η mesons for pT > 1.7 GeV/c are σ π 0 m = 4.56 ± 0.03 MeV/c 2 and σ η m = 15.3 ± 1.0 MeV/c 2 , respectively.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). One-dimensional charged kaon femtoscopy in p-Pb collisions at √sNN = 5.02 TeV. Physical Review C. ISSN 2469-9985. 100:024002(2), s. 1–15. doi: 10.1103/PhysRevC.100.024002. Fulltekst i vitenarkiv Vis sammendrag

  The correlations of identical charged kaons were measured in p-Pb collisions at √sNN = 5.02 TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths were extracted from one-dimensional kaon correlation functions and were compared with those obtained in pp and Pb-Pb collisions at √s = 7 TeV and √sNN = 2.76 TeV, respectively. The presented results also complement the identical-pion femtoscopic data published by the ALICE collaboration. The extracted radii increase with increasing chargedparticle multiplicity and decrease with increasing pair transverse momentum. At comparable multiplicities, the radii measured in p-Pb collisions are found to be close to those observed in pp collisions. The obtained femtoscopic parameters are reproduced by the EPOS 3 hadronic interaction model and disfavor models with large initial size or strong collective expansion at low multiplicities.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Coherent J/ψ photoproduction at forward rapidity in ultra-peripheral Pb–Pb collisions at √sNN = 5.02 TeV. Physics Letters B. ISSN 0370-2693. 798:134926, s. 1–14. doi: 10.1016/j.physletb.2019.134926. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE collaboration performed the first rapidity-differential measurement of coherent J/ψ photoproduction in ultra-peripheral Pb–Pb collisions at a center-of-mass energy √sNN = 5.02 TeV. The J/ψ is detected via its dimuon decay in the forward rapidity region (−4.0 < y < −2.5) for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 750 μb−1. The cross section for coherent J/ψ production is presented in six rapidity bins. The results are compared with theoretical models for coherent J/ψ photoproduction. These comparisons indicate that gluon shadowing effects play a role in the photoproduction process. The ratio of ψ to J/ψ coherent photoproduction cross sections was measured and found to be consistent with that measured for photoproduction off protons.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of the production of charm jets tagged with D0 mesons in pp collisions at √s = 7 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:133, s. 1–34. doi: 10.1007/JHEP08(2019)133. Fulltekst i vitenarkiv Vis sammendrag

  The production of charm jets in proton-proton collisions at a center-of-mass energy of s√=7 TeV was measured with the ALICE detector at the CERN Large Hadron Collider. The measurement is based on a data sample corresponding to a total integrated luminosity of 6.23 nb−1, collected using a minimum-bias trigger. Charm jets are identified by the presence of a D0 meson among their constituents. The D0 mesons are reconstructed from their hadronic decay D0 →K−π+. The D0-meson tagged jets are reconstructed using tracks of charged particles (track-based jets) with the anti-kT algorithm in the jet transverse momentum range 5<pchT,jet< 30 GeV/c and pseudorapidity |ηjet| < 0.5. The fraction of charged jets containing a D0-meson increases with pchT,jet from 0.042 ± 0.004 (stat) ± 0.006 (syst) to 0.080 ± 0.009 (stat) ± 0.008 (syst). The distribution of D0-meson tagged jets as a function of the jet momentum fraction carried by the D0 meson in the direction of the jet axis (zch∥) is reported for two ranges of jet transverse momenta, 5<pchT,jet< 15 GeV/c and 15<pchT,jet< 30 GeV/c in the intervals 0.2<zch∥∥<1.0 and 0.4<zch∥∥<1.0, respectively. The data are compared with results from Monte Carlo event generators (PYTHIA 6, PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum Chromodynamics calculation, obtained with the POWHEG method and interfaced with PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation and underlying event.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of jet radial profiles in Pb–Pb collisions at √sNN = 2.76 TeV. Physics Letters B. ISSN 0370-2693. 796, s. 204–219. doi: 10.1016/j.physletb.2019.07.020. Fulltekst i vitenarkiv Vis sammendrag

  The jet radial structure and particle transverse momentum (pT) composition within jets are presented in centrality-selected Pb–Pb collisions at √sNN = 2.76 TeV. Track-based jets, which are also called charged jets, were reconstructed with a resolution parameter of R = 0.3 at midrapidity |ηch jet| < 0.6 for transverse momenta pT, ch jet = 30–120 GeV/c. Jet–hadron correlations in relative azimuth and pseudorapidity space ( ϕ, η) are measured to study the distribution of the associated particles around the jet axis for different pT,assoc-ranges between 1 and 20 GeV/c. The data in Pb–Pb collisions are compared to reference distributions for pp collisions, obtained using embedded PYTHIA simulations. The number of high-pT associate particles (4 < pT,assoc < 20 GeV/c) in Pb–Pb collisions is found to be suppressed compared to the reference by 30 to 10%, depending on centrality. The radial particle distribution relative to the jet axis shows a moderate modification in Pb–Pb collisions with respect to PYTHIA. High-pT associate particles are slightly more collimated in Pb–Pb collisions compared to the reference, while low-pT associate particles tend to be broadened. The results, which are presented for the first time down to pT, ch jet = 30 GeV/c in Pb–Pb collisions, are compatible with both previous jet–hadron-related measurements from the CMS Collaboration and jet shape measurements from the ALICE Collaboration at higher pT, and add further support for the established picture of in-medium parton energy loss.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Investigations of anisotropic flow using multiparticle azimuthal correlations in pp, p−Pb, Xe-Xe, and Pb-Pb collisions at the LHC. Physical Review Letters. ISSN 0031-9007. 123:142301(14), s. 1–13. doi: 10.1103/PhysRevLett.123.142301. Fulltekst i vitenarkiv Vis sammendrag

  Measurements of anisotropic flow coefficients ( v n ) and their cross-correlations using two- and multiparticle cumulant methods are reported in collisions of p p at √ s = 13 TeV , p − Pb at a center-of-mass energy per nucleon pair √ s NN = 5.02 TeV , Xe-Xe at √ s NN = 5.44 TeV , and Pb-Pb at √ s NN = 5.02 TeV recorded with the ALICE detector. The multiplicity dependence of v n is studied in a very wide range from 20 to 3000 particles produced in the midrapidity region | η | < 0.8 for the transverse momentum range 0.2 < p T < 3.0 GeV / c . An ordering of the coefficients v 2 > v 3 > v 4 is found in p p and p − Pb collisions, similar to that seen in large collision systems, while a weak v 2 multiplicity dependence is observed relative to nucleus-nucleus collisions in the same multiplicity range. Using a novel subevent method, v 2 measured with four-particle cumulants is found to be compatible with that from six-particle cumulants in p p and p − Pb collisions. The magnitude of the correlation between v 2 n and v 2 m , evaluated with the symmetric cumulants SC ( m , n ) is observed to be positive at all multiplicities for v 2 and v 4 , while for v 2 and v 3 it is negative and changes sign for multiplicities below 100, which may indicate a different v n fluctuation pattern in this multiplicity range. The observed long-range multiparticle azimuthal correlations in high multiplicity p p and p − Pb collisions can neither be described by pythia 8 nor by impact-parameter-Glasma, music, and ultrarelativistic quantum molecular dynamics model calculations, and hence, provide new insights into the understanding of collective effects in small collision systems.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Event-shape and multiplicity dependence of freeze-out radii in pp collisions at √s = 7 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:108, s. 1–22. doi: 10.1007/JHEP09(2019)108. Fulltekst i vitenarkiv Vis sammendrag

  Two-particle correlations in high-energy collision experiments enable the extraction of particle source radii by using the Bose-Einstein enhancement of pion production at low relative momentum q ∝ 1/R. It was previously observed that in pp collisions at √ s = 7 TeV the average pair transverse momentum kT range of such analyses is limited due to large background correlations which were attributed to mini-jet phenomena. To investigate this further, an event-shape dependent analysis of Bose-Einstein correlations for pion pairs is performed in this work. By categorizing the events by their transverse sphericity ST into spherical (ST > 0.7) and jet-like (ST < 0.3) events a method was developed that allows for the determination of source radii for much larger values of kT for the first time. Spherical events demonstrate little or no background correlations while jet-like events are dominated by them. This observation agrees with the hypothesis of a mini-jet origin of the non-femtoscopic background correlations and gives new insight into the physics interpretation of the kT dependence of the radii. The emission source size in spherical events shows a substantially diminished kT dependence, while jet-like events show indications of a negative trend with respect to kT in the highest multiplicity events. Regarding the emission source shape, the correlation functions for both event sphericity classes show good agreement with an exponential shape, rather than a Gaussian one.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Production of the ρ(770)0 meson in pp and Pb-Pb collisions at √sNN = 2.76 TeV. Physical Review C. ISSN 2469-9985. 99:064901(6), s. 1–20. doi: 10.1103/PhysRevC.99.064901. Fulltekst i vitenarkiv Vis sammendrag

  The production of the ρ ( 770 ) 0 meson has been measured at midrapidity ( | y | < 0.5 ) in p p and centrality differential Pb-Pb collisions at √ s N N = 2.76 TeV with the ALICE detector at the Large Hadron Collider. The particles have been reconstructed in the ρ ( 770 ) 0 → π + π − decay channel in the transverse-momentum ( p T ) range 0.5–11 GeV / c . A centrality-dependent suppression of the ratio of the integrated yields 2 ρ ( 770 ) 0 / ( π + + π − ) is observed. The ratio decreases by ∼ 40 % from p p to central Pb-Pb collisions. A study of the p T -differential 2 ρ ( 770 ) 0 / ( π + + π − ) ratio reveals that the suppression occurs at low transverse momenta, p T < 2 GeV / c . At higher momentum, particle ratios measured in heavy-ion and p p collisions are consistent. The observed suppression is very similar to that previously measured for the K ∗ ( 892 ) 0 / K ratio and is consistent with EPOS3 predictions that may imply that rescattering in the hadronic phase is a dominant mechanism for the observed suppression.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Alexander; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Charged-particle production as a function of multiplicity and transverse spherocity in pp collisions at √s=5.02 and 13 TeV. European Physical Journal C. ISSN 1434-6044. 79:857(10), s. 1–22. doi: 10.1140/epjc/s10052-019-7350-y. Fulltekst i vitenarkiv Vis sammendrag

  We present a study of the inclusive chargedparticle transverse momentum (pT) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity, dNch/dη, in pp collisions at √s = 5.02 and 13 TeV covering the kinematic range |η| < 0.8 and 0.15 < pT < 20 GeV/c. The results are presented for events with at least one charged particle in |η| < 1 (INEL > 0). The pT spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The pT spectra normalized to that for INEL > 0 show little energy dependence. Moreover, the high-pT yields of charged particles increase faster than the charged-particle multiplicity density. The average pT as a function of multiplicity and transverse spherocity is reported for pp collisions at √s = 13 TeV. For low- (high-) spherocity events, corresponding to jet-like (isotropic) events, the average pT is higher (smaller) than that measured in INEL > 0 pp collisions. Within uncertainties, the functional form of pT (Nch) is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average pT in jet-like events.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2019). p−p, p−Λ, and Λ−Λ correlations studied via femtoscopy in pp reactions at √s=7 TeV. Physical Review C. ISSN 2469-9985. 99:024001(2). doi: 10.1103/PhysRevC.99.024001. Fulltekst i vitenarkiv Vis sammendrag

  We report on the first femtoscopic measurement of baryon pairs, such as p − p , p − Λ , and Λ − Λ , measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at √ s = 7 TeV . This study demonstrates the feasibility of such measurements in p p collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p − p , p − Λ , and Λ − Λ correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems: Correlation Analysis Tool using the Schrödinger equation (CATS). Within the assumption that in p p collisions the three particle pairs originate from a common source, its radius is found to be equal to r 0 = 1.125 ± 0.018 ( stat ) + 0.058 − 0.035 ( syst ) fm. The sensitivity of the measured p − Λ correlation is tested against different scattering parameters, which are defined by the interaction among the two particles, but the statistics is not sufficient yet to discriminate among different models. The measurement of the Λ − Λ correlation function constrains the phase space spanned by the effective range and scattering length of the strong interaction. Discrepancies between the measured scattering parameters and the resulting correlation functions at LHC and RHIC energies are discussed in the context of various models.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measuring K0SK± interactions using pp collisions at √s=7 TeV. Physics Letters B. ISSN 0370-2693. 790, s. 22–34. doi: 10.1016/j.physletb.2018.12.033. Fulltekst i vitenarkiv Vis sammendrag

  We present the first measurements of femtoscopic correlations between the and particles in pp collisions at TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding solely via the resonance. The extracted kaon source radius and correlation strength parameters for are found to be equal within the experimental uncertainties to those for . Results of the present study are compared with those from identical-kaon femtoscopic studies also performed with pp collisions at TeV by ALICE and with a measurement in Pb–Pb collisions at TeV. Combined with the Pb–Pb results, our pp analysis is found to be compatible with the interpretation of the having a tetraquark structure instead of that of a diquark.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A. & Adolfsson, Jonatan [Vis alle 51 forfattere av denne artikkelen] (2019). Charged-particle pseudorapidity density at mid-rapidity in p–Pb collisions at √sNN = 8.16 TeV. European Physical Journal C. ISSN 1434-6044. 79:307(4), s. 1–17. doi: 10.1140/epjc/s10052-019-6801-9. Fulltekst i vitenarkiv Vis sammendrag

  The pseudorapidity density of charged particles, dNch/dη , in p–Pb collisions has been measured at a centre-of-mass energy per nucleon–nucleon pair of sNN−−−√ = 8.16 TeV at mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, |η|<1.8 . The dNch/dη value is 19.1±0.7 at |η|<0.5 . This quantity divided by ⟨Npart⟩ / 2 is 4.73±0.20 , where ⟨Npart⟩ is the average number of participating nucleons, is 9.5% higher than the corresponding value for p–Pb collisions at sNN−−−√ = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the dNch/dη distribution. Saturation-based models reproduce the distributions well for η>−1.3 . The dNch/dη is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p–Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adam, Jaroslav; Adamová, Dagmar; Adler, A. & Adolfsson, Jonatan [Vis alle 51 forfattere av denne artikkelen] (2019). Energy dependence of exclusive J/ψ photoproduction off protons in ultra-peripheral p–Pb collisions at √sNN = 5.02 TeV. European Physical Journal C. ISSN 1434-6044. 79:402(5), s. 1–18. doi: 10.1140/epjc/s10052-019-6816-2. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of J/ψ vector mesons off proton targets in ultra–peripheral p–Pb collisions at a centre-of-mass energy per nucleon pair sNN=√5.02 TeV. The e + e − and μ+μ− decay channels are used to measure the cross section as a function of the rapidity of the J/ψ in the range −2.5<y<2.7 , corresponding to an energy in the γ p centre-of-mass in the interval 40<Wγp<550 GeV. The measurements, which are consistent with a power law dependence of the exclusive J/ψ photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Study of J/ψ azimuthal anisotropy at forward rapidity in Pb-Pb collisions at √sNN=5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:12(2), s. 1–30. doi: 10.1007/JHEP02(2019)012. Fulltekst i vitenarkiv Vis sammendrag

  The second (v2) and third (v3) flow harmonic coefficients of J/ψ mesons are measured at forward rapidity (2.5 < y < 4.0) in Pb-Pb collisions at √ sNN = 5.02 TeV with the ALICE detector at the LHC. Results are obtained with the scalar product method and reported as a function of transverse momentum, pT, for various collision centralities. A positive value of J/ψ v3 is observed with 3.7σ significance. The measurements, compared to those of prompt D0 mesons and charged particles at mid-rapidity, indicate an ordering with vn(J/ψ) < vn(D0 ) < vn(h±) (n = 2, 3) at low and intermediate pT up to 6 GeV/c and a convergence with v2(J/ψ) ≈ v2(D0 ) ≈ v2(h±) at high pT above 6–8 GeV/c. In semicentral collisions (5–40% and 10–50% centrality intervals) at intermediate pT between 2 and 6 GeV/c, the ratio v3/v2 of J/ψ mesons is found to be significantly lower (4.6σ) with respect to that of charged particles. In addition, the comparison to the prompt D0 -meson ratio in the same pT interval suggests an ordering similar to that of the v2 and v3 coefficients. The J/ψ v2 coefficient is further studied using the Event Shape Engineering technique. The obtained results are found to be compatible with the expected variations of the eccentricity of the initial-state geometry.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of dielectron production in central Pb-Pb collisions at √sNN=2.76 TeV. Physical Review C. ISSN 2469-9985. 99:024002(2), s. 1–23. doi: 10.1103/PhysRevC.99.024002. Fulltekst i vitenarkiv Vis sammendrag

  The first measurement of dielectron (e+e−) production in central (0–10%) Pb–Pb collisions at √sNN=2.76TeV at the LHC is presented. The dielectron invariant-mass spectrum is compared to the expected contributions from hadron decays in the invariant-mass range 0<mee<3.5GeV/c2. The ratio of data and the cocktail of hadronic contributions without vacuum ρ0 is measured in the invariant-mass range 0.15<mee<0.7GeV/c2, where an excess of dielectrons is observed in other experiments, and its value is 1.40±0.28(stat.)±0.08(syst.)±0.27(cocktail). The dielectron spectrum measured in the invariant mass range 0<mee<1GeV/c2 is consistent with the predictions from two theoretical model calculations that include thermal dielectron production from both partonic and hadronic phases with in-medium broadened ρ0 meson. The fraction of direct virtual photons over inclusive virtual photons is extracted for dielectron pairs with invariant mass 0.1<mee<0.3GeV/c2 and in the transverse-momentum intervals 1<pT,ee<2GeV/c and 2<pT,ee<4GeV/c. The measured fraction of virtual direct photons is consistent with the measurement of real direct photons by ALICE and with the expectations from previous dielectron measurements at RHIC within the experimental uncertainties.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 50 forfattere av denne artikkelen] (2019). Multiplicity dependence of light-flavor hadron production in pp collisions at √s=7 TeV. Physical Review C. ISSN 2469-9985. 99:024906(2), s. 1–30. doi: 10.1103/PhysRevC.99.024906. Fulltekst i vitenarkiv Vis sammendrag

  Comprehensive results on the production of unidentified charged particles, π±, K±, K0S, K∗(892)0, p, ¯p, ϕ (1020), Λ, ¯¯¯Λ, Ξ−, ¯¯¯Ξ+, Ω−, and ¯¯¯Ω+ hadrons in proton-proton (pp) collisions at √s=7 TeV at midrapidity (|y|<0.5) as a function of charged-particle multiplicity density are presented. In order to avoid autocorrelation biases, the actual transverse momentum (pT) spectra of the particles under study and the event activity are measured in different rapidity windows. In the highest multiplicity class, the charged-particle density reaches about 3.5 times the value measured in inelastic collisions. While the yield of protons normalized to pions remains approximately constant as a function of multiplicity, the corresponding ratios of strange hadrons to pions show a significant enhancement that increases with increasing strangeness content. Furthermore, all identified particle-to-pion ratios are shown to depend solely on charged-particle multiplicity density, regardless of system type and collision energy. The evolution of the spectral shapes with multiplicity and hadron mass shows patterns that are similar to those observed in p-Pb and Pb-Pb collisions at Large Hadron Collider energies. The obtained pT distributions and yields are compared to expectations from QCD-based ppevent generators as well as to predictions from thermal and hydrodynamic models. These comparisons indicate that traces of a collective, equilibrated system are already present in high-multiplicity ppcollisions.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Direct photon production at low transverse momentum in proton-proton collisions at √s=2.76 and 8 TeV. Physical Review C. ISSN 2469-9985. 99:024912(2), s. 1–19. doi: 10.1103/PhysRevC.99.024912. Fulltekst i vitenarkiv Vis sammendrag

  Measurements of inclusive and direct photon production at midrapidity in pp collisions at √s = 2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.4 < pT < 10 GeV/c and 0.3 < pT < 16 GeV/c, respectively. Photons are detected with the electromagnetic calorimeter (EMCal) and via reconstruction of e+e− pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping pT interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio Rγ , which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio Rγ , as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full pT range, Rγ for pT > 7 GeV/c is at least one σ above unity and consistent with expectations from next-to-leading order pQCD calculations.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of D0, D+, D∗+ and D+s production in pp collisions at √S = 5.02 TeV with ALICE. European Physical Journal C. ISSN 1434-6044. 79:388(5), s. 1–25. doi: 10.1140/epjc/s10052-019-6873-6. Fulltekst i vitenarkiv Vis sammendrag

  The measurements of the production of prompt D0, D+, D∗+, and D+s mesons in proton–proton (pp) collisions at s√=5.02 TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity (|y|<0.5) via their hadronic decay channels D0→K−π+, D+→K−π+π+, D∗+→D0π+→K−π+π+, D+s→ϕπ+→K+K−π+, and their charge conjugates. The production cross sections were measured in the transverse momentum interval 0<pT<36 GeV/c for D0, 1<pT<36 GeV/c for D+ and D∗+, and in 2<pT<24 GeV/c for D+s mesons. Thanks to the higher integrated luminosity, an analysis in finer pT bins with respect to the previous measurements at s√=7 TeV was performed, allowing for a more detailed description of the cross-section pT shape. The measured pT-differential production cross sections are compared to the results at s√=7 TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at s√=5.02 TeV. This measurement will allow for a more accurate determination of the nuclear modification factor in p–Pb and Pb–Pb collisions performed at the same nucleon–nucleon centre-of-mass energy.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Analysis of the apparent nuclear modification in peripheral Pb–Pb collisions at 5.02 TeV. Physics Letters B. ISSN 0370-2693. 793, s. 420–432. doi: 10.1016/j.physletb.2019.04.047. Fulltekst i vitenarkiv Vis sammendrag

  Charged-particle spectra at midrapidity are measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair √sNN = 5.02 TeV and presented in centrality classes ranging from most central (0–5%) to most peripheral (95–100%) collisions. Possible medium effects are quantified using the nuclear modification factor (RAA) by comparing the measured spectra with those from proton–proton collisions, scaled by the number of independent nucleon–nucleon collisions obtained from a Glauber model. At large transverse momenta (8 < pT < 20 GeV/c), the average RAA is found to increase from about 0.15 in 0–5% central to a maximum value of about 0.8 in 75–85% peripheral collisions, beyond which it falls off strongly to below 0.2 for the most peripheral collisions. Furthermore, RAA initially exhibits a positive slope as a function of pT in the 8–20 GeV/c interval, while for collisions beyond the 80% class the slope is negative. To reduce uncertainties related to event selection and normalization, we also provide the ratio of RAA in adjacent centrality intervals. Our results in peripheral collisions are consistent with a PYTHIA-based model without nuclear modification, demonstrating that biases caused by the event selection and collision geometry can lead to the apparent suppression in peripheral collisions. This explains the unintuitive observation that RAA is below unity in peripheral Pb–Pb, but equal to unity in minimum-bias p–Pb collisions despite similar charged-particle multiplicities.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). ϒ suppression at forward rapidity in Pb–Pb collisions at √sNN=5.02 TeV. Physics Letters B. ISSN 0370-2693. 790, s. 89–101. doi: 10.1016/j.physletb.2018.11.067. Fulltekst i vitenarkiv Vis sammendrag

  Inclusive ϒ(1S) and ϒ(2S) production have been measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair √sNN = 5.02 TeV, using the ALICE detector at the CERN LHC. The ϒ mesons are reconstructed in the centre-of-mass rapidity interval 2.5 < y < 4 and in the transverse-momentum range pT < 15 GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S) nuclear modification factor RAA as a function of collision centrality, transverse momentum and rapidity. The ϒ(1S) and ϒ(2S) RAA, integrated over the centrality range 0–90%, are 0.37±0.02(stat) ± 0.03(syst) and 0.10 ± 0.04(stat) ± 0.02(syst), respectively, leading to a ratio Rϒ(2S)AA /Rϒ(1S)AA of 0.28±0.12(stat)±0.06(syst). The observed ϒ(1S) suppression increases with the centrality of the collision and no significant variation is observed as a function of transverse momentum and rapidity.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2019). Suppression of Λ(1520) resonance production in central Pb-Pb collisions at √sNN=2.76 TeV. Physical Review C. ISSN 2469-9985. 99:024905(2), s. 1–12. doi: 10.1103/PhysRevC.99.024905. Fulltekst i vitenarkiv Vis sammendrag

  The production yield of the Λ (1520) baryon resonance is measured at midrapidity in Pb-Pb collisions at √sNN = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is performed in the Λ (1520) → pK − (and charge conjugate) hadronic decay channel as a function of the transverse momentum (pT) and collision centrality. The ratio of the pT -integrated production of Λ (1520) baryons relative to Λ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first 3 σ evidence of Λ (1520) suppression within a single collision system. The measured Λ (1520) / Λ ratio in central collisions is smaller than the value predicted by the statistical hadronization model calculations. The shape of the measured p T distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A. & Adolfsson, Jonatan [Vis alle 51 forfattere av denne artikkelen] (2019). Multiplicity dependence of (anti-)deuteron production in pp collisions at √s=7 TeV. Physics Letters B. ISSN 0370-2693. 794, s. 50–63. doi: 10.1016/j.physletb.2019.05.028. Fulltekst i vitenarkiv Vis sammendrag

  Abstract In this letter, the production of deuterons and anti-deuterons in pp collisions at TeV is studied as a function of the charged-particle multiplicity density at mid-rapidity with the ALICE detector at the LHC. Production yields are measured at mid-rapidity in five multiplicity classes and as a function of the deuteron transverse momentum (). The measurements are discussed in the context of hadron–coalescence models. The coalescence parameter , extracted from the measured spectra of (anti-)deuterons and primary (anti-)protons, exhibits no significant -dependence for , in agreement with the expectations of a simple coalescence picture. At fixed transverse momentum per nucleon, the parameter is found to decrease smoothly from low multiplicity pp to Pb–Pb collisions, in qualitative agreement with more elaborate coalescence models. The measured mean transverse momentum of (anti-)deuterons in pp is not reproduced by the Blast-Wave model calculations that simultaneously describe pion, kaon and proton spectra, in contrast to central Pb–Pb collisions. The ratio between the -integrated yield of deuterons to protons, d/p, is found to increase with the charged-particle multiplicity, as observed in inelastic pp collisions at different centre-of-mass energies. The d/p ratios are reported in a wide range, from the lowest to the highest multiplicity values measured in pp collisions at the LHC.

• Pandey, Ashutosh Kumar; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Pion-kaon femtoscopy in Pb–Pb collisions at √sNN=2.76TeV measured with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 351–354. doi: 10.1016/j.nuclphysa.2018.10.048. Fulltekst i vitenarkiv Vis sammendrag

  Femtoscopic correlations between charged pions and kaons for different charge combinations are measured in Pb−Pb collisions at √sNN = 2.76 TeV with ALICE at the LHC. The three-dimensional pion-kaon (π − K) correlation functions and double ratios in the out-side-long pair rest frame are studied in different centrality bins. The π − K femtoscopic source size parameter (Rout) and emission asymmetry (μout) are extracted. It is observed that the average source size of the system and the emission asymmetry between pions and kaons increase from peripheral to central events.

• Sas, Mike; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Direct photon elliptic flow in Pb–Pb collisions at √sNN=2.76 TeV. Nuclear Physics A. ISSN 0375-9474. 982, s. 195–197. doi: 10.1016/j.nuclphysa.2018.10.065. Fulltekst i vitenarkiv Vis sammendrag

  The elliptic flow of inclusive and direct photons was measured by ALICE for central and semi-central Pb–Pb collisionsat√sNN=2.76 TeV. The photons were reconstructed using the electromagnetic calorimeter PHOS and the centraltracking system. The inclusive photon flow reconstructed with both methods are combined and used to extract thedirect photon flow, using a decay photon simulation and the direct photon excessRγ, in the transverse momentum range 0.9<pT<6.2 GeV/c. We find that the theoretical predictions generally under-predict the results.

• Kim, Beomkyu; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). ALICE results on system-size dependence of charged-particle multiplicity density in p–Pb, Pb–Pb and Xe–Xe collisions. Nuclear Physics A. ISSN 0375-9474. 982, s. 279–282. doi: 10.1016/j.nuclphysa.2018.09.060. Fulltekst i vitenarkiv Vis sammendrag

  Particle production at LHC energies involves the interplay of hard (perturbative) and soft (non-perturbative) QCD processes. Global observables, such as the charged-particle multiplicity, are related to the initial geometry and the energy density produced in the collision. They are important to characterise relativistic heavy-ion collisions and to constrain model calculations. The LHC produced Xenon–Xenon collisions for the first time in October 2017. New results on the primary charged-particle pseudorapidity density, and its pseudorapidity and centrality dependence are presented for this lighter and deformed nucleus, and compared to measurements obtained for lead ions. New results will also be presented for p-Pb collisions at the highest energy of 8.16 TeV, as part of an overview of all the measurements at LHC Run 1 and 2 energies. These studies allow us to investigate the evolution of particle production with energy and system size and to compare models based on various particle production mechanisms and different initial conditions.

• Tripathy, Sushanta; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Energy dependence of ϕ(1020) production at mid-rapidity in pp collisions with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 180–182. doi: 10.1016/j.nuclphysa.2018.09.078. Fulltekst i vitenarkiv Vis sammendrag

  Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects during the hadronization phase in heavy-ion collisions. Measurements in small collision systems provide a necessary baseline for heavy-ion data, help to tune pQCD inspired event generators and give insight into the search for the onset of collective effects. As the φ meson has a longer lifetime compared to other resonances, it is expected that its production would be much less affected by regeneration and re-scattering processes. We report on measurements of φ meson production in minimum bias pp collisions at different beam energies and as a function of charged particle multiplicity with the ALICE detector at the LHC. The results include the transverse momentum (pT) distributions of φ as well as the particle yield ratios. Finally, we have also studied the φ effective strangeness content by comparing our results to theoretical calculations.

• Ohlson, Alice; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Investigating correlated fluctuations of conserved charges with net-Λ fluctuations in Pb–Pb collisions at ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 299–302. doi: 10.1016/j.nuclphysa.2018.11.020. Fulltekst i vitenarkiv Vis sammendrag

  Event-by-event fluctuations of conserved charges – such as electric charge, strangeness, and baryon number – in ultrarelativistic heavy-ion collisions provide insight into the properties of the quark-gluon plasma and the QCD phase diagram. They can be related to the higher moments of the multiplicity distributions of identified particles, such as the Λ baryon which carries both strangeness and baryon number and is thus of particular interest. We present the first measurement of net-Λ fluctuations in Pb–Pb collisions at √sNN = 5.02 TeV as a function of centrality and the pseudorapidity acceptance of the measurement. The results are compared to expectations of the effects of global baryon number conservation as well as to predictions from the HIJING Monte Carlo event generator. In this analysis the Identity Method is applied in a novel way to account for the combinatoric background in the invariant mass distribution.

• Pan, Jinjin; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Balance functions of (un)identified hadrons in Pb–Pb, p–Pb, and pp collisions at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 315–318. doi: 10.1016/j.nuclphysa.2018.09.022. Fulltekst i vitenarkiv Vis sammendrag

  In ultrarelativistic heavy-ion collisions, correlations of particles with opposite quantum numbers provide insight into quark production mechanisms and time scales, collective motion, and re-scattering in the hadronic phase. The longitudinal and azimuthal widths of balance functions for charged kaons and charged pions are used to examine the two-wave quark production model proposed to explain quark-antiquark production within the QGP, which predicts a large increase in up and down quark pairs relative to strange quark pairs around the time of hadronization. Balance functions are also analyzed in small collision systems such as p–Pb and pp to study fragmentation effects and possible collective effects in high-multiplicity events. A comprehensive set of balance functions has been measured using the ALICE detector, including results for unidentified hadrons in Pb–Pb and p–Pb collisions at , for charged pions in Pb–Pb collisions at , p–Pb collisions at and pp collisions at , and for charged kaons in Pb–Pb collisions at . The first balance function yield results are also presented.

• Varga-Kofarago, Monika; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). The evolution of the near-side peak in two-particle number and transverse momentum correlations in Pb–Pb collisions from ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 363–366. doi: 10.1016/j.nuclphysa.2018.09.055. Fulltekst i vitenarkiv Vis sammendrag

  Two-particle number and transverse momentum correlations are powerful tools for studying the medium produced in heavy-ion collisions. Correlations in the angular separation of pairs of hadrons can provide information on the medium transport characteristics. In particular, the transverse momentum correlations are sensitive to momentum currents, and provide information about the system life time, the shear viscosity over entropy density ratio (η/s) and the system relaxation time (τπ). Furthermore, the interaction of the jets produced in the initial stages of a collision can be studied using number correlations, by observing the medium-induced modification of the near-side jet peak. Measurements of both sets of correlations from Pb–Pb collisions are reported as a function of centrality. Theoretical interpretations and results from Monte Carlo generators are then confronted with the experimental data.

• Margutti, Jacopo; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurements of anisotropic flow and flow fluctuations in Xe–Xe and Pb–Pb collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 367–370. doi: 10.1016/j.nuclphysa.2018.11.026. Fulltekst i vitenarkiv Vis sammendrag

  Anisotropic flow is a key observable to characterise the system created in heavy-ion collisions, as it is sensitive to the system’s initial state, transport properties, the equation of state and freeze-out conditions. In these proceedings we present the anisotropic flow coefficients of inclusive charged particles in Pb–Pb collisions at √sNN = 2.76 and 5.02 TeV, and in Xe–Xe collisions at √sNN = 5.44 TeV. The results are reported for a wide range of particle transverse momentum within the pseudo-rapidity range |η| < 0.8 at different collision centralities. The energy and system dependence are found to place strong constraints on the temperature dependence of η/s and the modeling of the initial state, respectively. We also present detailed studies of flow fluctuations in heavy-ion collisions, in order to precisely characterise the underlying flow probability density function. We find evidence of non-Bessel-Gaussian fluctuations and discuss the origin of this observation.

• Lorenzo, Alessandra; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). f0(980) resonance production in pp collisions with the ALICE detector at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 201–203. doi: 10.1016/j.nuclphysa.2018.09.023. Fulltekst i vitenarkiv Vis sammendrag

  We report on a preliminary study of the production of f0(980) → π+π− at mid-rapidity (|y| < 0.5) performed with the ALICE detector at the LHC in minimum bias pp collisions at the centre-of-mass energy √ s = 5.02 TeV. The f0(980) signal extraction is challenging due to the large background from correlated π+π− pairs from other resonance decays in the invariant mass window under study, as well as due to the combinatorics from uncorrelated pairs. We present the strategy for the signal extraction and first results in terms of pT-dependent production yields. The results are discussed and compared with production yields of other resonances and stable hadrons.

• Andrews, Harry Arthur; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Exploring the Phase Space of Jet Splittings at ALICE using Grooming and Recursive Techniques. Nuclear Physics A. ISSN 0375-9474. 982, s. 587–590. doi: 10.1016/j.nuclphysa.2018.09.007. Fulltekst i vitenarkiv Vis sammendrag

  Hard splittings in the evolution of a hard scattered parton may be modified by the presence of a dense strongly interacting medium. Grooming procedures can be used to isolate such hard components of a jet and allows one to focus on the two subjets resulting from a sufficiently hard partonic splitting. Measurements of the symmetry parameter (zg), angular separation (Rg) and number of splittings (nSD) of Soft Drop groomed jets are reported as measured with the ALICE Detector in pp and Pb–Pb collisions at √s= 7 TeV and √sNN= 2.76 TeV, respectively. The use of recursive splittings and their mappings to identify interesting regions of phase space in the zg − Rg plane are also discussed.

• Hosokawa, Ritsuya; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Exploring jet profiles in Pb-Pb collisions at 5.02 TeV with the ALICE detector. Nuclear Physics A. ISSN 0375-9474. 982, s. 639–642. doi: 10.1016/j.nuclphysa.2018.10.063. Fulltekst i vitenarkiv Vis sammendrag

  In this contribution, we present measurements of inclusive jet production with the ALICE detector in Pb-Pb collisions at √sNN = 5.02 TeV. Production cross sections of charged particle jets and fully reconstructed jets are measured with jet resolution parameters R = 0.2 and 0.3. To quantify the medium induced parton energy loss, jet nuclear modification factors (RAA) are measured by utilizing POWHEG+Pythia8 predictions as reference cross section in pp collisions. We also calculate the ratio of jet production cross sections for jets reconstructed with different cone radii to explore the jet radial profile in Pb-Pb collisions. The ratios of jet cross sections are compared to a pp reference predicted by POWHEG+Pythia8 and in-medium energy loss model prediction by the JEWEL Monte Carlo event generator.

• Singh, Ranbir; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Spin alignment measurements using vector mesons with ALICE detector at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 515–518. doi: 10.1016/j.nuclphysa.2018.12.004. Fulltekst i vitenarkiv Vis sammendrag

  We present new measurements related to spin alignment of K*0 vector mesons at mid-rapidity for Pb–Pb collisions at √sNN = 2.76 and 5.02 TeV. The spin alignment measurements are carried out with respect to production plane and 2nd order event plane. At low pT the spin density matrix element ρ00 for K*0 is found to have values slightly below 1/3, while it is consistent with 1/3, i.e. no spin alignment, at high pT. Similar values of ρ00 are observed with respect to both production plane and event plane. Within statistical and systematic uncertainties, ρ00 values are also found to be independent of √sNN. ρ00 also shows centrality dependence with maximum deviation from 1/3 for mid-central collisions with respect to both the kinematic planes. The measurements for K*0 in pp collisions at √s = 13 TeV and for K0S (a spin 0 hadron) in 20-40% central Pb–Pb collisions at √sNN = 2.76 TeV are consistent with no spin alignment.

• Bencédi, Gyula; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Event-shape- and multiplicity-dependent identified particle production in pp collisions at 13 TeV with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 507–510. doi: 10.1016/j.nuclphysa.2018.08.021. Fulltekst i vitenarkiv Vis sammendrag

  Multiplicity-dependent measurements of identified particle production led to the discovery of collective-like behavior in pp collisions at the LHC. Better understanding of the effects attributed to well-understood physics, like multiple hard scatterings, is required to establish whether this behaviour is truly collective in origin. Experimentally, those effects can be controlled using event shapes, like transverse spherocity, which allows the classification of pp collisions either as jetty or isotropic events. The transverse momentum (pT) spectra of light-flavor hadrons in pp collisions measured over a broad range provide important input to study particle production mechanisms in the soft and hard scattering regimes of the QCD. In this work, they are used to perform a comprehensive study as a function of the event multiplicity, collision energy, and event shapes. The proton-to-pion and kaon-to-pion particle ratios as a function of pT are also reported and the results compared to QCD-inspired models.

• Trzeciak, Barbara; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurements of heavy-flavour correlations and jets with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 579–582. doi: 10.1016/j.nuclphysa.2018.10.085. Fulltekst i vitenarkiv Vis sammendrag

  In this work, the latest heavy-flavour correlation and jet measurements at mid-rapidity with the ALICE detector in pp, p–Pb and Pb–Pb collisions from the LHC Run 2 are reported. In particular, the results of azimuthal correlation measurements of D mesons with charged particles in pp collisions at √s = 13 TeV and in p–Pb collisions at √sNN = 5.02 TeV are presented. Studies on the centrality-dependent azimuthal correlations of heavy-flavour hadron decay electrons with charged particles in Pb–Pb collisions at √sNN = 5.02 TeV are shown. In addition, measurements of D-meson tagged jet production in pp collisions at √s = 7 TeV and in p–Pb collisions at √sNN = 5.02 TeV are presented, including studies in pp collisions of the jet momentum fraction carried by the D meson. A first result on the D-meson tagged jet nuclear modification factor in central Pb–Pb collisions at √sNN = 5.02 TeV is also reported.

• Sekihata, Daiki; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Energy and system dependence of nuclear modification factors of inclusive charged particles and identified light hadrons measured in p–Pb, Xe–Xe and Pb–Pb collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 567–570. doi: 10.1016/j.nuclphysa.2018.10.052. Fulltekst i vitenarkiv Vis sammendrag

  We report recent ALICE results on primary charged particle and neutral meson production in pp, p–Pb, Pb–Pb and Xe– Xe collisions at LHC energies. In this article, measurements of the nuclear modification factors RAA of primary charged particles and of light neutral mesons in Pb–Pb, in Xe–Xe and in p–Pb collisions in a wide pT range and different centrality classes are discussed. We compare the nuclear modification factors obtained for different collision systems as a function of transverse momentum, collision centrality as well as charged particle multiplicity (dNch/dη). We also present comparison of experimental results to model calculations.

• Bellini, Francesca; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Testing the system size dependence of hydrodynamical expansion and thermal particle production with π, K, p, and ϕ in Xe–Xe and Pb–Pb collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 427–430. doi: 10.1016/j.nuclphysa.2018.09.082. Fulltekst i vitenarkiv Vis sammendrag

  We present new results on transverse momentum spectra, integrated yields, and mean transverse momenta of pions, kaons, and protons, as well as of ϕ-mesons for various centrality classes measured in Pb–Pb and Xe–Xe collisions at the LHC. This unique set of data allows us to investigate bulk particle production for very different systems at similar multiplicities. The chemical and kinetic freeze-out parameters are extracted via statistical-thermal and combined blast-wave fits to the data in heavy-ion collisions and are compared to results obtained in pp and p–Pb collisions at similar multiplicities. The evolution of collective-like effects from pp and p–Pb collisions to Xe–Xe and Pb–Pb collisions is further investigated by detailed comparisons to predictions from models.

• Mohammadi, Naghmeh; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Non-linear flow modes of identified particles in Pb–Pb collisions at √sNN=5.02TeV with the ALICE detector. Nuclear Physics A. ISSN 0375-9474. 982, s. 383–386. doi: 10.1016/j.nuclphysa.2018.09.059. Fulltekst i vitenarkiv Vis sammendrag

  The non-linear flow modes, v4,22, v5,32 and v6,33 as a function of transverse momentum (pT) have been measured for the first time in Pb–Pb collisions at √sNN = 5.02 TeV for identified particles, i.e. charged pions, kaons and (anti- )protons. These observables probe the contribution of the second and third initial anisotropy coefficients to the higher order flow harmonics. Interestingly, all the characteristic features observed in previous pT-differential as well as pTintegrated measurements (e.g. v2 and v3) for various particle species are present in these measurements, i.e. increase of magnitude with increasing centrality percentile, a mass ordering in the low pT region and a particle type grouping in the intermediate pT region. The results cover 0–1% (ultra-central collisions), 10–20% (mid-central collisions) and 40–50% (mid-peripheral collisions) centrality intervals and allow to test models that attempt to describe initial conditions and the mode-coupling of different harmonics.

• Gajdošová, Katarína; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). ALICE measurements of flow coefficients and their correlations in small (pp and p–Pb) and large (Xe–Xe and Pb–Pb) collision systems. Nuclear Physics A. ISSN 0375-9474. 982, s. 487–490. doi: 10.1016/j.nuclphysa.2018.09.006. Fulltekst i vitenarkiv Vis sammendrag

  Many observables which are used as a signature of the collective effects in heavy-ion collisions when measured in high multiplicity pp and pA interactions reveal a very similar behaviour. We will present first measurements of different order flow coefficients and their magnitude correlations for data collected by ALICE during the LHC Run 2 operation, which includes pp collisions at √ s = 13 TeV, p–Pb at √ sNN = 5.02 TeV, Xe–Xe at √ sNN = 5.44 TeV and Pb–Pb collisions at √ sNN = 5.02 TeV. Such a broad spectrum of colliding systems with different energies and wide range of multiplicity allow for detailed investigation of their collision dynamics. The measurements are based on a newly developed subevent technique, which was proven to be particularly important for studies in small systems. The results provide an important insight into the nature of collective phenomena in different collision systems.

• Pacík, Vojtech; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Elliptic flow of identified hadrons in small collisional systems measured with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 451–454. doi: 10.1016/j.nuclphysa.2018.09.020. Fulltekst i vitenarkiv Vis sammendrag

  Recent observations of long-range multi-particle azimuthal correlations in p–Pb and high multiplicity pp collisions provided new insights into collision dynamics and opened a possibility to study collective effects in these small systems. New measurement of pT-differential elliptic flow (v2) coefficient for inclusive charged hadrons as well as a variety of identified particle species in p–Pb collisions at √ sNN = 5.02 TeV recorded by ALICE during the LHC Run 2 data taking are presented. Besides high precision measurements of v2(pT) for π ± , K ± and p(p), the very first results for K ¯ 0 S , Λ(Λ¯ ) and φ are shown. In order to eliminate non-flow contamination, a pseudorapidity separation between correlated particles is applied as well as subtraction of remaining non-flow estimate based on a measurement of minimum-bias pp collisions at √ s = 13 TeV. Moreover, reported characteristic mass ordering and approximate NCQ and KET scaling of v2 allows to test various theoretical models, constrain the initial conditions, and probe the origin of collective behavior in small collision systems.

• Dubla, Andrea; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Heavy-flavour hadron decay leptons in Pb–Pb and Xe–Xe collisions at the LHC with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 651–654. doi: 10.1016/j.nuclphysa.2018.09.038. Fulltekst i vitenarkiv Vis sammendrag

  Heavy quarks, i.e. charm and beauty, are sensitive probes of the medium produced in high-energy heavy-ion collisions. They are produced in the early stage of the collision, mainly in hard partonic scattering processes, and are expected to experience the whole collision evolution interacting with the medium constituents via both elastic and inelastic processes. The nuclear modification factor (RAA) is one of the main experimental observables that allow us to investigate the interaction strength of heavy quarks with the medium. The ALICE collaboration measured the production of open heavy-flavour hadrons via their semi-leptonic decays to electrons at mid-rapidity and to muons at forward rapidity in elementary proton-proton (pp) collisions as well as p–Pb, Pb–Pb and in Xe–Xe collisions.

• Haque, Md. Rihan; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurements of the chiral magnetic effect in Pb–Pb collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 543–546. doi: 10.1016/j.nuclphysa.2018.11.008. Fulltekst i vitenarkiv Vis sammendrag

  We present the measurement of the charge-dependent 3-particle azimuthal correlation for unidentified charged particles in Pb–Pb collisions at √sNN = 5.02 TeV in ALICE. The results are compared with corresponding results from Pb– Pb collisions at √sNN = 2.76 TeV. We observe no significant difference in the charge-sensitive 3-particle correlator (γ112) between the two collision energies. Charged-dependent mixed-harmonic correlator (γ132) is also presented and compared with the predictions from a blast-wave model incorporating local charge conservation.

• Puccio, Maximiliano; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Light (anti-)nuclei production and elliptic flow at the LHC with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 447–450. doi: 10.1016/j.nuclphysa.2018.10.043. Fulltekst i vitenarkiv Vis sammendrag

  Results on the production of stable light nuclei, including deuterons, 3He, 4He and the corresponding anti-nuclei, in Pb–Pb collisions at √sNN = 2.76 TeV and √sNN = 5.02 TeV are presented and compared with theoretical predictions and with the results in small systems to provide insight into the production mechanisms of (anti-)nuclei at colliders. The experimental results are presented giving a critical view of their comparison to the expectations from coalescence and hydrodynamic models that aim at describing both the pT-spectra and the elliptic flow.

• Dillenseger, Pascal; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Quarkonium measurements in nucleus–nucleus collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 703–706. doi: 10.1016/j.nuclphysa.2018.09.024. Fulltekst i vitenarkiv Vis sammendrag

  Quarkonia, i.e. bound states of bb¯ and cc¯ quarks, are powerful observables to study the properties of nuclear matter under extreme conditions. The formation of a Quark-Gluon Plasma (QGP), which is predicted by lattice QCD calculations at high temperatures as reached at the LHC energies, has a strong influence on the production and behavior of quarkonia. The latest ALICE results on bottomonium and charmonium production in nucleus−nucleus collisions are presented. This includes measurements of the Υ(1S) and Υ(2S) nuclear modification factor (RAA) at forward rapidity and the J/ψ RAA and v2 as a function of centrality, pT and rapidity in Pb−Pb collisions at √sNN = 5.02 TeV. Also, first results from J/ψ measurements in Xe−Xe collisions at √sNN = 5.44 TeV are presented. Further on, the experimental results are compared to various calculations from theoretical models.

• Dash, Ajay Kumar; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Multiplicity dependence of strangeness and hadronic resonance production in pp and p-Pb collisions with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 467–470. doi: 10.1016/j.nuclphysa.2018.11.011. Fulltekst i vitenarkiv Vis sammendrag

  One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high mul-tiplicity pp and p–Pb collisions at√sNN=7 and 5.02 TeV, respectively. The strangeness enhancement is investigated bymeasuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strangeparticles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has beenobserved in such systems. We report the latest results on multiplicity dependence of strange and multi-strange hadronproduction in pp collisions at√s=13 TeV with ALICE. We also presented recent measurements of mesonic and bary-onic resonances in small collision systems like pp and p–Pb at√sNN=13 and 8.16 TeV, respectively. The multiplicitydependent studies in pp and p-Pb collisions have been used to investigate how the hadronic scattering processes affectmeasured resonance yields and to better understand the interplay between canonical suppression and strangeness en-hancement. The measurement of theφ(1020) meson as a function of multiplicity provides crucial constraints in thiscontext.

• Zanoli, Henrique J. C.; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Open heavy-flavour production and elliptic flow in p-Pb collisions at the LHC with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 691–694. doi: 10.1016/j.nuclphysa.2018.11.012. Fulltekst i vitenarkiv Vis sammendrag

  Measurements of open heavy flavour production in p–A collisions allow the investigation of Cold Nuclear Matter effects. In addition, they are an important tool for a complementary investigation of the long-range correlations found in small systems in the light flavour sector. In this work, production measurements of D mesons at mid-rapidity in p–Pb collisions at √ sNN = 5.02 TeV are reported. Production yields are also reported for the heavy-flavour hadron decay electrons at central rapidity at √ sNN = 5.02 and 8.16 TeV. The elliptic flow (v2) of heavy-flavour hadron decay electrons in highmultiplicity p-Pb collisions at √ sNN = 5.02 TeV is found to be positive with a significance larger than 5σ.

• Bailhache, R.; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Dielectron measurements in pp and Pb–Pb colllisions with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 779–782. doi: 10.1016/j.nuclphysa.2018.10.021. Fulltekst i vitenarkiv Vis sammendrag

  The production of low-mass dielectrons is one of the most promising tools for the investigation of chiral symmetry restoration and thermal radiation from the QGP created in heavy-ion collisions. To single out the signal characteristics of the QGP, it is crucial to understand the primordial e+e− pair production in vacuum, i.e. in inelastic proton-proton (pp) collisions. Low-mass dielectrons have been measured with ALICE at the LHC in pp collisions at √ s = 7 and 13 TeV, and in Pb–Pb collisions at √ sNN = 2.76 TeV. An overview of the results on dielectron production is presented, together with their implications for the direct-photon and heavy-quark production.

• Paul, Biswarup; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Quarkonium production in p-Pb collisions with ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 739–742. doi: 10.1016/j.nuclphysa.2018.11.024. Fulltekst i vitenarkiv Vis sammendrag

  ALICE has measured quarkonium production in p-Pb collisions at backward (−4.46 < ycms < −2.96), mid (−1.37 < ycms < 0.43) and forward (2.03 < ycms < 3.53) rapidity (y) regions down to zero transverse momentum (pT). The inclusive J/ψ production has been studied at mid-y in p-Pb interactions at √sNN = 5.02 TeV and at forward and backward y in p-Pb collisions at √sNN = 5.02 TeV and 8.16 TeV. The comparison of the J/ψ production to the one of the loosely bound ψ(2S) state is discussed, together with new results on the nuclear modification factors of the Υ(1S) and Υ(2S) states measured at forward and backward y. All the results will be compared to those obtained at lower energies and with available theoretical calculations.

• Peng, Xinye; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Non-strange and strange D-meson and charm-baryon production in heavy-ion collisions measured with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 667–670. doi: 10.1016/j.nuclphysa.2018.09.017. Fulltekst i vitenarkiv Vis sammendrag

  We present recent results on strange and non-strange D-meson production measured with ALICE in Pb–Pb collisions at the LHC. In addition, the measurements of the Λ+ c -baryon production and of the Λ+ c /D0 ratio in pp, p–Pb, and, for the first time ever, Pb–Pb collisions are reported.

• Tarhini, Mohamad; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Electroweak boson measurements in p-Pb and Pb-Pb collisions at √sNN=5.02TeV with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 783–786. doi: 10.1016/j.nuclphysa.2018.10.022. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE collaboration has measured the electroweak boson production at forward rapidity in Pb-Pb and p-Pb collisions at √sNN = 5.02 TeV. Final results on the Z0 boson production in Pb-Pb collisions are presented as a function of centrality and rapidity. Calculations based on free parton distribution functions overestimate the measurement up to 3σ. In addition, final results on W± and Z0 bosons production in p-Pb collisions at the same energy will be presented and discussed.

• Siddhanta, Sabyasachi; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Muon physics at forward rapidity with the ALICE detector upgrade. Nuclear Physics A. ISSN 0375-9474. 982, s. 947–950. doi: 10.1016/j.nuclphysa.2018.10.034. Fulltekst i vitenarkiv Vis sammendrag

  ALICE is the experiment specifically designed to study the Quark-Gluon Plasma (QGP) in heavy-ion collisions at the CERN LHC. The ALICE detector will be upgraded during the Long Shutdown 2, planned for 2019-2020, in order to cope with the maximum interaction rate of 50 kHz of Pb-Pb collisions foreseen for Runs 3 and 4. The ambitious programme of high-precision measurements, expected for muon physics after 2020, requires an upgrade of the front-end and readout electronics of the existing Muon Spectrometer. This concerns the Cathode Pad Chambers (CPC) used for tracking and the Resistive Plate Chambers (RPC) used for triggering and for muon identification. The Muon Forward Tracker (MFT), an internal tracker added in front of the front absorber of the existing Muon Spectrometer, is also part of the ALICE detector upgrade programme. It is based on an assembly of circular planes made of Monolithic Active Pixel Sensors (MAPS), covering the pseudorapidity range 2.5 < η < 3.6. The MFT will improve present measurements and enable new ones. A selection of results from physics performance studies will be presented, together with an overview of the technical aspects of the upgrade project.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2019). Two-particle differential transverse momentum and number density correlations in p−Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV at the CERN Large Hadron Collider. Physical Review C. ISSN 2469-9985. 100:044903(4), s. 1–41. doi: 10.1103/PhysRevC.100.044903. Fulltekst i vitenarkiv Vis sammendrag

  We present measurements of two-particle differential number correlation functions R 2 and transverse momentum correlation functions P 2 , obtained from p -Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV. The results are obtained by using charged particles in the pseudorapidity range | η | < 1.0 and transverse momentum range 0.2 < p T < 2.0 GeV/ c as a function of pair separation in pseudorapidity, | Δ η | , azimuthal angle Δ φ , and for several charged-particle multiplicity classes. Measurements are carried out for like-sign and unlike-sign charged-particle pairs separately and combined to obtain charge-independent and charge-dependent correlation functions. We study the evolution of the width of the near-side peak of these correlation functions with collision centrality. Additionally, we study Fourier decompositions of the correlators in Δ φ as a function of pair separation | Δ η | . Significant differences in the dependence of their harmonic coefficients on multiplicity classes are found. These differences can be exploited, in theoretical models, to obtain further insight into charged-particle production and transport in heavy-ion collisions. Moreover, an upper limit of nonflow contributions to flow coefficients v n measured in Pb-Pb collisions based on the relative strength of Fourier coefficients measured in p -Pb interactions is estimated.

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Measurement of prompt D0, D+, D*+, and D+S production in p–Pb collisions at √sNN = 5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2019:92(12), s. 1–42. doi: 10.1007/JHEP12(2019)092. Fulltekst i vitenarkiv Vis sammendrag

  The measurement of the production of prompt D0, D+, D*+, and D+S mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of sNN−−−√ = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb−1, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 < ycms< 0.04) as a function of transverse momentum (pT) in the intervals 0 < pT< 36 GeV/c for D0, 1 < pT< 36 GeV/c for D+ and D*+, and 2 < pT< 24 GeV/c for D+ mesons. For each species, the nuclear modification factor RpPb is calculated as a function of pT using a proton-proton (pp) ref- erence measured at the same collision energy. The results are compatible with unity in the whole pT range. The average of the non-strange D mesons RpPb is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The pT dependence of the D0, D+, and D*+ nuclear modification factors is also reported in the interval 1 < pT< 36 GeV/c as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the pT-differential cross sections of D0, D+, D*+, and D+S mesons are also reported. The D+S and D+ yields are compared as a function of the charged-particle multiplicity for several pT intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties.

• Gasik, P.; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Upgrade of the ALICE central barrel tracking detectors: ITS and TPC. Nuclear Physics A. ISSN 0375-9474. 982, s. 943–946. doi: 10.1016/j.nuclphysa.2018.08.022. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE Collaboration will undertake a major upgrade of the detector apparatus during the second LHC Long Shutdown LS2 (2019–2020) in view of the Runs 3 and 4 (2021–2029). The objective of the upgrade is two-fold: i) an improvement of the tracking precision and efficiency, in particular in the low-momentum range; ii) an improvement of the readout capabilities of the experiment, in order to fully exploit the luminosity for heavy ions envisaged after LS2. The first goal will be achieved by replacing the Inner Tracking System with a new tracker, composed of seven layers of silicon pixel detectors. The new tracker will be made up of about 25000 Monolithic Active Pixel Sensors with fast readout, resulting in a material thickness reduced to 0.3% (inner layers) – 1% (outer layers) of the radiation length and a granularity of 28×28μm2. The second goal will be achieved, among other measures, by replacing the readout chambers of the 90m3 Time Projection Chamber with Micro Pattern Gaseous Detectors. In particular, the new readout chambers will consist of stacks of 4 Gas Electron Multiplier foils combining different hole pitches. The upgraded detector will operate continuously without the use of a triggered gating grid. It will thus be able to record all Pb–Pb collisions at the LHC interaction rate of 50kHz.

• Behera, Nirbhay Kumar; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Higher moment fluctuations of identified particle distributions from ALICE. Nuclear Physics A. ISSN 0375-9474. 982, s. 851–854. doi: 10.1016/j.nuclphysa.2018.11.030. Fulltekst i vitenarkiv Vis sammendrag

  Cumulants of conserved charges fluctuations are regarded as a potential tool to study the criticality in the QCD phase diagram and to determine the freeze-out parameters in a model-independent way. At LHC energies, the measurements of the ratio of the net-baryon (net-proton) cumulants can be used to test the lattice QCD predictions. In this work, we present the first measurements of cumulants of the net-proton number distributions up to 4th order in Pb–Pb collisions at √sNN = 2.76 and 5.02 TeV as a function of collision centrality. We compare our cumulant ratios results with the STAR experiment net-proton results measured in the first phase of the Beam Energy Scan program at RHIC. The results can be used to obtain the chemical freeze-out parameters at LHC.

• Colocci, Manuel; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Constraining production models with light (anti-)nuclei measurements in small systems with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 895–898. doi: 10.1016/j.nuclphysa.2018.11.029. Fulltekst i vitenarkiv Vis sammendrag

  The production of deuterons and anti-deuterons in pp collisions at √s = 7 and 13 TeV has been studied as a function of charged-particle multiplicity using the ALICE detector at the LHC. The preliminary results are shown here, together with those obtained in heavy-ion collisions. They are presented by focusing the discussion on the comparison with expectations from hadron-coalescence models.

• Trogolo, Stefano; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Addressing the hypertriton lifetime puzzle with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 815–818. doi: 10.1016/j.nuclphysa.2018.11.016. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE Collaboration collected a large data sample of Pb-Pb collisions at√sNN=5.02 TeV in 2015 at the LargeHadron Collider (LHC) and the excellent particle identification (PID) capabilities allow for the detection of rarelyproduced (anti-)hypernuclei. In particular, the (anti-)hypertriton,3ΛH, which is a bound state of a proton, a neutron andaΛ, is the lightest known hypernucleus.The results on the3ΛH production are compared with the predictions from a model based on coalescence approachand from statistical-thermal models to investigate the production mechanisms in heavy-ion collisions. Emphasis willalso be put on the latest and more precise determination of the3ΛH lifetime.

• Albuquerque, D. S. D.; Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Hadronic resonances, strange and multi-strange particle production in Xe-Xe and Pb-Pb collisions with ALICE at the LHC. Nuclear Physics A. ISSN 0375-9474. 982, s. 823–826. doi: 10.1016/j.nuclphysa.2018.08.033. Fulltekst i vitenarkiv Vis sammendrag

  We present measurements of hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of √sNN = 5.44 and 5.02 TeV, respectively, by the ALICE collaboration at the LHC. Particle ratios are presented as a function of multiplicity for K0 s , Λ, Ξ−, Ξ¯ +, Ω−, Ω¯ +, ρ(770)0, K∗(892)0, φ(1020) and Λ(1520). Our results are discussed and compared with predictions of QCD-inspired event generators. Additionally, comparisons with lower energy measurements and smaller systems are also presented.

• Acharya, Shreyasi; Acosta, Fernando Torales; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A. & Adolfsson, Jonatan [Vis alle 52 forfattere av denne artikkelen] (2019). Λc+ production in Pb–Pb collisions at √sNN = 5.02 TeV. Physics Letters B. ISSN 0370-2693. 793, s. 212–223. doi: 10.1016/j.physletb.2019.04.046. Fulltekst i vitenarkiv Vis sammendrag

  A measurement of the production of prompt baryons in Pb–Pb collisions at TeV with the ALICE detector at the LHC is reported. The and were reconstructed at midrapidity () via the hadronic decay channel (and charge conjugate) in the transverse momentum and centrality intervals GeV/c and 0–80%. The ratio, which is sensitive to the charm quark hadronisation mechanisms in the medium, is measured and found to be larger than the ratio measured in minimum-bias pp collisions at TeV and in p–Pb collisions at TeV. In particular, the values in p–Pb and Pb–Pb collisions differ by about two standard deviations of the combined statistical and systematic uncertainties in the common interval covered by the measurements in the two collision systems. The ratio is also compared with model calculations including different implementations of charm quark hadronisation. The measured ratio is reproduced by models implementing a pure coalescence scenario, while adding a fragmentation contribution leads to an underestimation. The nuclear modification factor, , is also presented. The measured values of the of , and non-strange D mesons are compatible within the combined statistical and systematic uncertainties. They show, however, a hint of a hierarchy , conceivable with a contribution from coalescence mechanisms to charm hadron formation in the medium.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). Transverse momentum spectra and nuclear modification factors of charged particles in Xe–Xe collisions at √sNN=5.44 TeV. Physics Letters B. ISSN 0370-2693. 788, s. 166–179. doi: 10.1016/j.physletb.2018.10.052. Fulltekst i vitenarkiv Vis sammendrag

  Transverse momentum (pT) spectra of charged particles at mid-pseudorapidity in Xe–Xe collisions at √sNN = 5.44 TeV measured with the ALICE apparatus at the Large Hadron Collider are reported. The kinematic range 0.15 < pT < 50 GeV/c and |η| < 0.8 is covered. Results are presented in nine classes of collision centrality in the 0–80% range. For comparison, a pp reference at the collision energy of √s = 5.44 TeV is obtained by interpolating between existing pp measurements at √s = 5.02 and 7 TeV. The nuclear modification factors in central Xe–Xe collisions and Pb–Pb collisions at a similar center-ofmass energy of √sNN = 5.02 TeV, and in addition at 2.76 TeV, at analogous ranges of charged particle multiplicity density dNch/dη show a remarkable similarity at pT > 10 GeV/c. The centrality dependence of the ratio of the average transverse momentum pT in Xe–Xe collisions over Pb–Pb collision at √s = 5.02 TeV is compared to hydrodynamical model calculations

• Acharya, Shreyasi; Adamová, Dagmar; Adhya, Souvik Priyam; Adler, A.; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2019). Study of the Λ–Λ interaction with femtoscopy correlations in pp and p–Pb collisions at the LHC. Physics Letters B. ISSN 0370-2693. 797:134822, s. 1–13. doi: 10.1016/j.physletb.2019.134822. Fulltekst i vitenarkiv Vis sammendrag

  This work presents new constraints on the existence and the binding energy of a possible Λ–Λ bound state, the H-dibaryon, derived from Λ–Λ femtoscopic measurements by the ALICE collaboration. The results are obtained from a new measurement using the femtoscopy technique in pp collisions at √s = 13 TeV and p–Pb collisions at √sNN = 5.02 TeV, combined with previously published results from pp collisions at √s = 7 TeV. The Λ–Λ scattering parameter space, spanned by the inverse scattering length f_0^−1 and the effective range d_0, is constrained by comparing the measured Λ–Λ correlation function with calculations obtained within the Lednický model. The data are compatible with hypernuclei results and lattice computations, both predicting a shallow attractive interaction, and permit to test different theoretical approaches describing the Λ–Λ interaction. The region in the (f _0^−1 ,d_0) plane which would accommodate a Λ–Λ bound state is substantially restricted compared to previous studies. The binding energy of the possible Λ–Λ bound state is estimated within an effective-range expansion approach and is found to be B_ΛΛ = 3.2+1.6−2.4(stat)+1.8−1.0(syst) MeV.

• Acharya, Shreyasi; Adam, Jaroslav; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2018). Longitudinal asymmetry and its effect on pseudorapidity distributions in Pb–Pb collisions at √sNN = 2.76 TeV. Physics Letters B. ISSN 0370-2693. 781, s. 20–32. doi: 10.1016/j.physletb.2018.03.051. Fulltekst i vitenarkiv Vis sammendrag

  First results on the longitudinal asymmetry and its effect on the pseudorapidity distributions in Pb–Pb collisions at √sNN = 2.76 TeV at the Large Hadron Collider are obtained with the ALICE detector. The longitudinal asymmetry arises because of an unequal number of participating nucleons from the two colliding nuclei, and is estimated for each event by measuring the energy in the forward neutron-Zero-Degree-Calorimeters (ZNs). The effect of the longitudinal asymmetry is measured on the pseudorapidity distributions of charged particles in the regions |η|<0.9, 2.8<η<5.1 and −3.7<η<−1.7 by taking the ratio of the pseudorapidity distributions from events corresponding to different regions of asymmetry. The coefficients of a polynomial fit to the ratio characterise the effect of the asymmetry. A Monte Carlo simulation using a Glauber model for the colliding nuclei is tuned to reproduce the spectrum in the ZNs and provides a relation between the measurable longitudinal asymmetry and the shift in the rapidity (y_0) of the participant zone formed by the unequal number of participating nucleons. The dependence of the coefficient of the linear term in the polynomial expansion, c_1, on the mean value of y_0 is investigated.

• Acharya, Shreyasi; Adam, Jaroslav; Adamová, Dagmar; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2018). The ALICE Transition Radiation Detector: Construction, operation, and performance. Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002. 881(2018), s. 88–127. doi: 10.1016/j.nima.2017.09.028. Fulltekst i vitenarkiv Vis sammendrag

  The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/\(c\) in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 52 forfattere av denne artikkelen] (2018). Production of 4He and 4He in Pb–Pb collisions at √sNN = 2.76 TeV at the LHC. Nuclear Physics A. ISSN 0375-9474. 971, s. 1–20. doi: 10.1016/j.nuclphysa.2017.12.004. Fulltekst i vitenarkiv Vis sammendrag

  Results on the production of 4He and 4He nuclei in Pb&ndash;Pb collisions at &radic;sNN = 2.76 TeV in the rapidity range | y |&lt; 1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0&ndash;10% central events are found to be dN/dy4He = (0.8 &plusmn; 0.4 (stat) &plusmn; 0.3 (syst)) &times; 10&minus;6 and dN/dy4He = (1.1 &plusmn; 0.4 (stat) &plusmn; 0.2 (syst)) &times; 10&minus;6, respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (Tchem = 156 MeV) as for light hadrons. The measured ratio of 4He/4He is 1.4 &plusmn; 0.8 (stat) &plusmn; 0.5 (syst).

• Adamová, Dagmar; Aggarwal, Madan M.; Rinella, Gianluca Aglieri; Agnello, Michelangelo; Agrawal, Nikita & Ahammed, Zubayer [Vis alle 51 forfattere av denne artikkelen] (2018). J/ψ production as a function of charged-particle pseudorapidity density in p–Pb collisions at √sNN = 5.02 TeV. Physics Letters B. ISSN 0370-2693. 776, s. 91–104. doi: 10.1016/j.physletb.2017.11.008. Fulltekst i vitenarkiv Vis sammendrag

  We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dNch/dη in p–Pb collisions at √sNN=5.02 TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dNch/dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyond moderate multiplicities. In addition, the forward-to-backward nuclear modification factor ratio is also reported, showing an increasing suppression of J/ψ production at forward rapidity with respect to backward rapidity for increasing charged-particle multiplicity.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 52 forfattere av denne artikkelen] (2018). Measurements of low-pT electrons from semileptonic heavy-flavour hadron decays at mid-rapidity in pp and Pb-Pb collisions at √sN-N−=2.76 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2018:61(10), s. 1–29. doi: 10.1007/JHEP10(2018)061. Fulltekst i vitenarkiv Vis sammendrag

  Transverse-momentum (pT) differential yields of electrons from semileptonic heavy-flavour hadron decays have been measured in the most central (0–10%) and in semi-central (20–40%) Pb–Pb collisions at sNN−−−√=2.76 TeV. The corresponding production cross section in pp collisions has been measured at the same energy with substantially reduced systematic uncertainties with respect to previously published results. The modification of the yield in Pb–Pb collisions with respect to the expectation from an incoherent superposition of nucleon-nucleon collisions is quantified at mid-rapidity (|y| < 0.8) in the pT interval 0.5–3 GeV/c via the nuclear modification factor, RAA. This paper extends the pT reach of the RAA measurement towards significantly lower values with respect to a previous publication. In Pb–Pb collisions the pT-differential measurements of yields at low pT are essential to investigate the scaling of heavy-flavour production with the number of binary nucleon-nucleon collisions. Heavy-quark hadronization, a collective expansion and even initial-state effects, such as the nuclear modification of the Parton Distribution Function, are also expected to have a significant effect on the measured distribution.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adler, Clemens; Adolfsson, Jonatan & Aggarwal, Madan M. [Vis alle 51 forfattere av denne artikkelen] (2018). Medium modification of the shape of small-radius jets in central Pb-Pb collisions at √sN-N-=2.76 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 2018:139(10), s. 1–28. doi: 10.1007/JHEP10(2018)139. Fulltekst i vitenarkiv Vis sammendrag

  We present the measurement of a new set of jet shape observables for track-based jets in central Pb-Pb collisions at sNN−−−√=2.76 TeV. The set of jet shapes includes the first radial moment or angularity, g; the momentum dispersion, pTD; and the difference between the leading and sub-leading constituent track transverse momentum, LeSub. These observables provide complementary information on the jet fragmentation and can constrain different aspects of the theoretical description of jet-medium interactions. The jet shapes were measured for a small resolution parameter R = 0.2 and were fully corrected to particle level. The observed jet shape modifications indicate that in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by PYTHIA calculations, which were validated with the measurements of the jet shapes in proton-proton collisions at s√=7 TeV. The comparison of the measured distributions to templates for quark and gluon-initiated jets indicates that in-medium fragmentation resembles that of quark jets in vacuum. We further argue that the observed modifications are not consistent with a totally coherent energy loss picture where the jet loses energy as a single colour charge, suggesting that the medium resolves the jet structure at the angular scales probed by our measurements (R = 0.2). Furthermore, we observe that small-R jets can help to isolate purely energy loss effects from other effects that contribute to the modifications of the jet shower in medium such as the correlated background or medium response.

• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2018). Measurement of D0, D+, D*+ and D s + production in Pb-Pb collisions at √sN-N−=5.02 TeV. Journal of High Energy Physics (JHEP). ISSN 1126-6708. 174(10), s. 1–34. doi: 10.1007/JHEP10(2018)174. Fulltekst i vitenarkiv Vis sammendrag

  We report measurements of the production of prompt D0, D+, D*+ and D s + mesons in Pb–Pb collisions at the centre-of-mass energy per nucleon-nucleon pair sNN−−−√=5.02 TeV, in the centrality classes 0–10%, 30–50% and 60–80%. The D-meson production yields are measured at mid-rapidity (|y| < 0.5) as a function of transverse momentum (pT). The pT intervals covered in central collisions are: 1 < pT< 50 GeV/c for D0, 2 < pT< 50GeV/c for D+, 3 < pT< 50GeV/c for D*+, and 4 < pT< 16GeV/c for D s + mesons. The nuclear modification factors (RAA) for non-strange D mesons (D0, D+, D*+) show minimum values of about 0.2 for pT = 6–10 GeV/c in the most central collisions and are compatible within uncertainties with those measured at s√NN=2.76 TeV. For D s + mesons, the values of RAA are larger than those of non-strange D mesons, but compatible within uncertainties. In central collisions the average RAA of non-strange D mesons is compatible with that of charged particles for pT> 8 GeV/c, while it is larger at lower pT. The nuclear modification factors for strange and non-strange D mesons are also compared to theoretical models with different implementations of in-medium energy loss.

• Acharya, Shreyasi; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M.; Rinella, Gianluca Aglieri & Agnello, Michelangelo [Vis alle 51 forfattere av denne artikkelen] (2018). Constraints on jet quenching in p–Pb collisions at √sNN = 5.02  TeV measured by the event-activity dependence of semi-inclusive hadron-jet distributions. Physics Letters B. ISSN 0370-2693. 783, s. 95–113. doi: 10.1016/j.physletb.2018.05.059. Fulltekst i vitenarkiv Vis sammendrag

  The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p–Pb collisions at √sNN = 5.02 TeV. Jets are reconstructed from charged-particle tracks using the anti-kT algorithm with resolution parameter R = 0.2 and 0.4. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum 15 < pch T,jet < 50 GeV/c and are compared in various intervals of p–Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive observable is self-normalized and such comparisons do not require the interpretation of p–Pb event activity in terms of collision geometry, in contrast to inclusive jet observables. These measurements provide new constraints on the magnitude of jet quenching in small systems at the LHC. In p–Pb collisions with high event activity, the average medium-induced out-of-cone energy transport for jets with R = 0.4 and 15 < pch T,jet < 50 GeV/c is measured to be less than 0.4 GeV/c at 90% confidence, which is over an order of magnitude smaller than a similar measurement for central Pb–Pb collisions at √sNN = 2.76 TeV. Comparison is made to theoretical calculations of jet quenching in small systems, and to inclusive jet measurements in p–Pb collisions selected by event activity at the LHC and in d–Au collisions at RHIC.

• Acharya, Shreyasi; Adam, Jaroslav; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2018). Production of deuterons, tritons, 3He nuclei, and their antinuclei in pp collisions at √s=0.9, 2.76, and 7 TeV. Physical Review C. ISSN 2469-9985. 97:024615(2). doi: 10.1103/PhysRevC.97.024615. Fulltekst i vitenarkiv Vis sammendrag

  Invariant differential yields of deuterons and antideuterons in p p collisions at √ s = 0.9, 2.76 and 7 TeV and the yields of tritons, 3 He nuclei, and their antinuclei at √ s = 7 TeV have been measured with the ALICE detector at the CERN Large Hadron Collider. The measurements cover a wide transverse momentum ( p T ) range in the rapidity interval | y | < 0.5 , extending both the energy and the p T reach of previous measurements up to 3 GeV/ c for A = 2 and 6 GeV/ c for A = 3 . The coalescence parameters of (anti)deuterons and 3 ¯¯¯¯ He nuclei exhibit an increasing trend with p T and are found to be compatible with measurements in p A collisions at low p T and lower energies. The integrated yields decrease by a factor of about 1000 for each increase of the mass number with one (anti)nucleon. Furthermore, the deuteron-to-proton ratio is reported as a function of the average charged particle multiplicity at different center-of-mass energies.

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• Acharya, Shreyasi; Acosta, Fernando T.; Adamová, Dagmar; Adolfsson, Jonatan; Aggarwal, Madan M. & Rinella, Gianluca Aglieri [Vis alle 51 forfattere av denne artikkelen] (2019). ALICE Collaboration. Nuclear Physics A. ISSN 0375-9474. 982, s. 975–984. doi: 10.1016/S0375-9474(18)30498-6. Fulltekst i vitenarkiv

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