Publications
-
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,081 contributors for this article]
(2026).
Space-time evolution of particle emission in p–Pb collisions at √sNN = 5.02 TeV with 3D kaon femtoscopy.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2026(4).
doi:
10.1007/JHEP04(2026)113.
Full text in Research Archive
Show summary
The measurement of three-dimensional femtoscopic correlations between identical charged kaons (K±K±) produced in p–Pb collisions at center-of-mass energy per nucleon
pair √sNN = 5.02TeV with ALICE at the LHC is presented for the first time. This measurement, supplementary to those in pp and Pb–Pb collisions, allows understanding
the particle-production mechanisms at different charged-particle multiplicities and provides information on the dynamics of the source of particles created in p–Pb collisions, for which a general consensus does not yet exist. It is shown that the measured source sizes increase with charged-particle multiplicity and decrease with increasing pair transverse momentum. These trends for K±K± are similar to the ones observed earlier in identical charged-pion and K0sK0s correlations in Pb–Pb collisions at various energies and in π±π± correlations in p–Pb collisions at √sNN = 5.02TeV. At comparable multiplicity, the source sizes measured in p–Pb collisions agree within uncertainties with those observed in pp collisions, and there is an indication that they are smaller than those observed in Pb–Pb collisions. The obtained results are also compared with predictions from the hadronic interaction model EPOS 3, which tends to underestimate the source size for the most central collisions and agrees with the data for semicentral and peripheral events. Furthermore, the time of maximal emission for kaons is extracted. It turns out to be comparable with the value obtained in highly peripheral Pb–Pb collisions at the same energy, indicating that the kaon emission evolution is similar to that in p–Pb collisions.
-
Acharya, S.; Adamová, D.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L. & Agnello, M.
[Show all 1,059 contributors for this article]
(2025).
Measurement of ω meson production in pp collisions at √s = 13 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(4).
doi:
10.1007/JHEP04(2025)067.
Full text in Research Archive
Show summary
The pT-differential cross section of ω meson production in pp collisions at √s = 13TeV at midrapidity (|y| < 0.5) was measured with the ALICE detector at the LHC, covering an unprecedented transverse-momentum range of 1.6 < pT < 50 GeV/c. The meson is reconstructed via the ω → π+π−π0 decay channel. The results are compared with
various theoretical calculations: PYTHIA8.2 with the Monash 2013 tune overestimates the data by up to 50%, whereas good agreement is observed with Next-to-Leading Order (NLO)
calculations incorporating ω fragmentation using a broken SU(3) model. The ω/π0 ratio is presented and compared with theoretical calculations and the available measurements at
lower collision energies. The presented data triples the pT ranges of previously available measurements. A constant ratio of Cω/π0 = 0.578 ± 0.006 (stat.) ± 0.013 (syst.) is found
above a transverse momentum of 4 GeV/c, which is in agreement with previous findings at lower collision energies within the systematic and statistical uncertainties.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,070 contributors for this article]
(2025).
Multiplicity-dependent jet modification from di-hadron correlations in pp collisions at √s = 13 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(3).
doi:
10.1007/JHEP03(2025)194.
Full text in Research Archive
Show summary
Short-range correlations between charged particles are studied via two-particle angular correlations in pp collisions at √ s = 13 TeV. The correlation functions are measured as a function of the relative azimuthal angle ∆φ and the pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transversemomentum range 1 < pT < 8 GeV/c. Near-side (|∆φ| < 1.3) peak widths are extracted from a generalised Gaussian fitted over the correlations in full pseudorapidity separation (|∆η| < 1.8), while the per-trigger associated near-side yields are extracted for the short-range correlations (|∆η| < 1.3). Both are evaluated as a function of charged-particle multiplicity obtained by two different event activity estimators. The width of the near-side peak decreases with increasing multiplicity, and this trend is reproduced qualitatively by the Monte Carlo event generators PYTHIA 8, AMPT, and EPOS. However, the models overestimate the width in the low transverse-momentum region (pT < 3 GeV/c). The per-trigger associated near-side yield increases with increasing multiplicity. Although this trend is also captured qualitatively by the considered event generators, the yield is mostly overestimated by the models in the considered kinematic range. The measurement of the shape and yield of the short-range correlation peak can help us understand the interplay between jet fragmentation and event activity, quantify the narrowing trend of the near-side peak as a function of transverse momentum and multiplicity selections in pp collisions, and search for final-state jet modification in small collision systems.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,069 contributors for this article]
(2025).
Direct-photon production in inelastic and high-multiplicity proton–proton collisions at √s= 13 TeV.
Physics Letters B.
ISSN 0370-2693.
868.
doi:
10.1016/j.physletb.2025.139645.
Full text in Research Archive
Show summary
In this letter, we present the first measurement of direct photons at the transverse momentum of 1 < 𝑝T < 6 GeV/𝑐 at √ midrapidity |𝜂| < 0.8 in inelastic and high-multiplicity proton–proton collisions at a centre-of-mass energy of 𝑠 = 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of lightflavour neutral mesons are estimated using independent measurements in proton–proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low 𝑝T in both inelastic and high-multiplicity event classes, with a significance of 3.2𝜎 and 1.9𝜎 in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of directphoton yield with charged-particle multiplicity.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,079 contributors for this article]
(2025).
Coherent J/ψ photoproduction at midrapidity in Pb−Pb collisions at √sNN=5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
871.
doi:
10.1016/j.physletb.2025.139952.
Full text in Research Archive
Show summary
The coherent J∕𝜓 photoproduction cross section is measured for the first time at midrapidity in peripheral to semicentral Pb − Pb collisions at √𝑠NN = 5.02 TeV. The centrality differential cross section d𝜎∕d𝑦 is reported for the centrality range 40–90%, together with the doubly-differential cross section d2𝜎∕d𝑦d𝑝T, extracted in two peripheral centrality classes. The J∕𝜓 mesons are reconstructed in the dielectron channel, in the rapidity interval |𝑦| < 0.9 using the ALICE central barrel detectors. The J∕𝜓 cross section at midrapidity is statistically compatible to the earlier ALICE measurement at forward rapidity and at the same centre-of-mass energy, and shows only a mild centrality dependence over the covered range. Several sets of theoretical calculations taking into account the hadronic overlap in the collisions but ignoring possible final-state effects from a hot expanding medium are found to give a fairly good description of the current measurements within uncertainties.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,075 contributors for this article]
(2025).
First measurement of symmetric cumulants of hexagonal flow harmonics in Pb-Pb collisions at √sNN = 5.02 TeV.
Physical Review C.
ISSN 2469-9985.
112(2).
doi:
10.1103/4ltm-g1qg.
Full text in Research Archive
Show summary
Correlations between event-by-event fluctuations of anisotropic flow harmonics are measured in Pb-Pb
collisions at a center-of-mass energy per nucleon pair of 5.02 TeV, as recorded by the ALICE detector at the
LHC. This study presents correlations up to the hexagonal flow harmonic v6, which was measured for the first
time. The magnitudes of these higher-order correlations are found to vary as a function of collision centrality
and harmonic order. These measurements are compared to viscous hydrodynamic model calculations with EKRT
initial conditions and to the iEBE-VISHNU model with TRENTo initial conditions. The observed discrepancies
between the data and the model calculations vary depending on the harmonic combinations. Due to the sensitivity
of model parameters estimated with Bayesian analyses to these higher-order observables, the results presented in
this work provide new and independent constraints on the initial conditions and transport properties in theoretical
models used to describe the system created in heavy-ion collisions
-
Zurlo, N.; Zugravel, S. C.; Zhu, Y.; Zhu, J.; Zhou, Y. & Zhou, D.
[Show all 1,057 contributors for this article]
(2025).
Common femtoscopic hadron-emission source in pp collisions at the LHC.
European Physical Journal C.
ISSN 1434-6044.
85(2).
doi:
10.1140/epjc/s10052-025-13793-y.
Full text in Research Archive
Show summary
The femtoscopic study of pairs of identical pions is particularly suited to investigate the effective source function of particle emission, due to the resulting Bose–Einstein
correlation signal. In small collision systems at the LHC, pp in particular, the majority of the pions are produced in resonance decays, which significantly affect the profile and size
of the source. In this work, we explicitly model this effect in order to extract the primordial source in pp collisions at √s = 13 TeV from charged π–π correlations measured by
ALICE. We demonstrate that the assumption of a Gaussian primordial source is compatible with the data and that the effective source, resulting from modifications due to resonances, is approximately exponential, as found in previous measurements at the LHC. The universality of hadron emission in pp collisions is further investigated by applying the
same methodology to characterize the primordial source of K–p pairs. The size of the primordial source is evaluated as a function of the transverse mass (mT) of the pairs, leading to
the observation of a common scaling for both π–π and K–p , suggesting a collective effect. Further, the present results are compatible with the mT scaling of the p–p and p− primordial source measured by ALICE in high multiplicity pp collisions, providing additional evidence for the presence of a common emission source for all hadrons in small collision
systems at the LHC. This will allow the determination of the source function for any hadron–hadron pairs with high precision, granting access to the properties of the possible
final-state interaction among pairs of less abundantly produced hadrons, such as strange or charmed particles
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,067 contributors for this article]
(2025).
Multimuons in cosmic-ray events as seen in ALICE at the LHC.
Journal of Cosmology and Astroparticle Physics (JCAP).
2025(4),
p. 1–30.
doi:
10.1088/1475-7516/2025/04/009.
Full text in Research Archive
Show summary
ALICE is a large experiment at the CERN Large Hadron Collider. Located 52
meters underground, its detectors are suitable to measure muons produced by cosmic-ray
interactions in the atmosphere. In this paper, the studies of the cosmic muons registered by
ALICE during Run 2 (2015–2018) are described. The analysis is limited to multimuon events
defined as events with more than four detected muons (Nµ > 4) and in the zenith angle range
0
◦ < θ < 50◦
. The results are compared with Monte Carlo simulations using three of the
main hadronic interaction models describing the air shower development in the atmosphere:
QGSJET-II-04, EPOS-LHC, and SIBYLL 2.3d. The interval of the primary cosmic-ray energy
involved in the measured muon multiplicity distribution is about 4×1015 < Eprim < 6×1016 eV.
In this interval none of the three models is able to describe precisely the trend of the
composition of cosmic rays as the energy increases. However, QGSJET-II-04 is found to be
the only model capable of reproducing reasonably well the muon multiplicity distribution,
assuming a heavy composition of the primary cosmic rays over the whole energy range,
while SIBYLL 2.3d and EPOS-LHC underpredict the number of muons in a large interval of
multiplicity by more than 20% and 30%, respectively. The rate of high muon multiplicity
events (Nµ > 100) obtained with QGSJET-II-04 and SIBYLL 2.3d is compatible with the
data, while EPOS-LHC produces a significantly lower rate (55% of the measured rate). For
both QGSJET-II-04 and SIBYLL 2.3d, the rate is close to the data when the composition
is assumed to be dominated by heavy elements, an outcome compatible with the average
energy Eprim ∼ 1017 eV of these events. This result places significant constraints on more
exotic production mechanisms.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,074 contributors for this article]
(2025).
First Measurement of A = 4 Hypernuclei and Antihypernuclei at the LHC.
Physical Review Letters.
ISSN 0031-9007.
134(16).
doi:
10.1103/PhysRevLett.134.162301.
Full text in Research Archive
Show summary
In this Letter, the first evidence of the 4
Λ¯ He antihypernucleus is presented, along with the first
measurement at the LHC of the production of (anti)hypernuclei with mass number A ¼ 4, specifically
ðantiÞ4
ΛH and ðantiÞ4
ΛHe. In addition, the antiparticle-to-particle ratios for both hypernuclei (4
Λ¯ H¯ =4
ΛH and
4
Λ¯ He=4
ΛHe) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter
created in heavy-ion collisions. The results are obtained from a data sample of central Pb-Pb collisions,
collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of ffiffiffiffiffiffiffi
sNN p ¼ 5.02 TeV. The yields measured for the average of the charge-conjugated states are found to
be ½0.78 0.19ðstatÞ 0.17ðsystÞ × 10−6 for the ðantiÞ4
ΛH and ½1.08 0.34ðstatÞ 0.20ðsystÞ × 10−6
for the ðantiÞ4
ΛHe, and the measured antiparticle-to-particle ratios are in agreement with unity. The presence
of ðantiÞ4
ΛH and ðantiÞ4
ΛHe excited states is expected to strongly enhance the production yield of these
hypernuclei. The yield values exhibit a combined deviation of 3.3σ from the theoretical ground-state-only
expectation, while the inclusion of the excited states in the calculations leads to an agreement within 0.6σ
with the present measurements. Additionally, the measured ðantiÞ4
ΛH and ðantiÞ4
ΛHe masses are compatible
with the world-average values within the uncertainties
-
Zurlo, N.; Zugravel, S. C.; Zhu, Y.; Zhu, S.; Zhu, J. & Zhou, Y.
[Show all 1,069 contributors for this article]
(2025).
Measurements of differential two-particle number and transverse momentum correlation functions in pp collisions at √s = 13 TeV.
European Physical Journal C.
ISSN 1434-6044.
85(8).
doi:
10.1140/epjc/s10052-025-14531-0.
Full text in Research Archive
Show summary
Differential two-particle normalized cumulants (R2 ) and transverse momentum correlations (P2 ) are mea- sured as a function of the relative pseudorapidity and azimuthal angle difference (η, ϕ) of charged particle pairs in minimum bias pp collisions at √s = 13 TeV. The mea- surements use charged hadrons in the pseudorapidity region of |η| < 0.8 and the transverse momentum range 0.2 < pT < 2.0 GeV/c in order to focus on soft multiparticle interactions and to complement prior measurements of these correlation functions in p–Pb and Pb–Pb collisions. The correlation func- tions are reported for both unlike-sign and like-sign pairs and their charge-independent and charge-dependent combi- nations. Both the R2 and P2 measured in pp collisions exhibit features qualitatively similar to those observed in p–Pb and Pb–Pb collisions. The η and ϕ root mean square widths of the near-side peak of the correlation functions are evalu- ated and compared with those observed in p–Pb and Pb–Pb collisions and show smooth evolution with the multiplicity of charged particles produced in the collision. The compar- ison of the measured correlation functions with predictions from PYTHIA8 shows that this model qualitatively captures their basic structure and characteristics but feature impor- tant differences. In addition, the RCD 2 is used to determine the charge balance function of hadrons produced within the detector acceptance of the measurements. The integral of the balance function is found to be compatible with those reported by a previous measurement in Pb–Pb collisions.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,078 contributors for this article]
(2025).
First measurement of 𝐷𝑠1(1+)(2536)+ and 𝐷* 𝑠2(2+)(2573)+ production in proton-proton collisions at √𝑠 =13 TeV at the LHC.
Physical Review D.
ISSN 2470-0010.
111(11).
doi:
10.1103/PhysRevD.111.112005.
Full text in Research Archive
Show summary
The production yields of the orbitally excited charm-strange mesons Ds1ð1þÞð2536Þþ and
D
s2ð2þÞð2573Þþ were measured for the first time in proton-proton (pp) collisions at a center-of-mass
energy of ffiffi
s p ¼ 13 TeV with the ALICE experiment at the LHC. The Dþ
s1 and Dþ
s2 mesons were measured
at midrapidity (jyj < 0.5) in minimum-bias and high-multiplicity pp collisions in the transverse-momentum
interval 2 < pT < 24 GeV=c. Their production yields relative to the Dþ
s ground-state yield were found to
be compatible between minimum-bias and high-multiplicity collisions, as well as with previous
measurements in ep and eþe− collisions. The measured Dþ
s1=Dþ
s and Dþ
s2 =Dþ
s yield ratios are described
by statistical hadronization models and can be used to tune the parameters governing the production of
excited charm-strange hadrons in Monte Carlo generators, such as PYTHIA 8.
-
Zurlo, N.; Zugravel, S. C.; Zhu, Y.; Zhu, S.; Zhu, J. & Zhou, Y.
[Show all 1,078 contributors for this article]
(2025).
Measurement of the production cross section of prompt Ξc0 baryons in p–Pb collisions at √sNN=5.02 TeV.
European Physical Journal C.
ISSN 1434-6044.
85(1).
doi:
10.1140/epjc/s10052-024-13531-w.
Full text in Research Archive
Show summary
The transverse momentum (pT) differential production cross section of the promptly produced charm-strange baryon Ξ0c (and its charge conjugate Ξ0c) is measured at midrapidity via its hadronic decay into π+Ξ− in p–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision sNN√ = 5.02 TeV with the ALICE detector at the LHC. The Ξ0c nuclear modification factor (RpPb), calculated from the cross sections in pp and p–Pb collisions, is presented and compared with the RpPb of Λ+c baryons. The ratios between the pT-differential production cross section of Ξ0c baryons and those of D0 mesons and Λ+c baryons are also reported and compared with results at forward and backward rapidity from the LHCb Collaboration. The measurements of the production cross section of prompt Ξ0c baryons are compared with a model based on perturbative QCD calculations of charm-quark production cross sections, which includes only cold nuclear matter effects in p–Pb collisions, and underestimates the measurement by a factor of about 50. This discrepancy is reduced when the data is compared with a model that includes string formation beyond leading-colour approximation or in which hadronisation is implemented via quark coalescence. The pT-integrated cross section of prompt Ξ0c-baryon production at midrapidity extrapolated down to pT = 0 is also reported. These measurements offer insights and constraints for theoretical calculations of the hadronisation process. Additionally, they provide inputs for the calculation of the charm production cross section in p–Pb collisions at midrapidity.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,071 contributors for this article]
(2025).
First observation of strange baryon enhancement with effective energy in pp collisions at the LHC.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(3).
doi:
10.1007/JHEP03(2025)029.
Full text in Research Archive
Show summary
The production of (multi-)strange hadrons is measured at midrapidity in proton-proton collisions at
= 13 TeV as a function of the local charged-particle multiplicity in the pseudorapidity interval |η| < 0.5 and of the very-forward energy measured by the ALICE Zero-Degree Calorimeters. The latter provides information on the effective energy, i.e. the energy available for particle production in the collision once subtracted from the centre-of-mass energy. The yields of
,
, and
per charged-particle increase with the effective energy. In addition, this work exploits a multi-differential approach to decouple the roles of local multiplicity and effective energy in such an enhancement. The results presented in this article provide new insights into the interplay between global properties of the collision, such as the initial available energy in the event, and the locally produced final hadronic state, connected to the charged-particle multiplicity at midrapidity. Notably, a strong increase of strange baryon production with effective energy is observed for fixed charged-particle multiplicity at midrapidity. These results are discussed within the context of existing phenomenological models of hadronisation implemented in different tunes of the PYTHIA 8 event generator.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,079 contributors for this article]
(2025).
J/ψ-hadron correlations at midrapidity in pp collisions at √s = 13 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(7).
doi:
10.1007/JHEP07(2025)023.
Full text in Research Archive
Show summary
We report on the measurement of inclusive, non-prompt, and prompt J/ψ-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV . The correlations are studied at midrapidity (|y| < 0.9) in the transverse momentum ranges pT < 40 GeV/c for the J/ψ and 0.15 < pT < 10 GeV/c and |η| < 0.9 for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of Lint = 34 nb−1 and Lint = 6.9 pb−1, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of E = 4 and 9 GeV in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of Lint = 0.9 pb−1 and Lint = 8.4 pb−1, respectively. The azimuthally integrated near and away side yields of associated charged hadrons per J/ψ trigger are presented as a function of the J/ψ and associated hadron transverse momentum. The measurements are discussed in comparison to PYTHIA calculations.
-
Zurlo, N.; Zugravel, S. C.; Zhu, Y.; Zhu, S.; Zhu, J. & Zhou, Zhuo
[Show all 1,067 contributors for this article]
(2025).
System size and energy dependence of the mean transverse momentum fluctuations at the LHC.
European Physical Journal C.
ISSN 1434-6044.
85(7).
doi:
10.1140/epjc/s10052-025-14325-4.
Full text in Research Archive
Show summary
Event-by-event fluctuations of the event-wise mean transverse momentum, pT, of charged particles produced in proton–proton (pp) collisions at √ s =5.02TeV, Xe– Xe collisions at √ √ sNN = 5.44TeV, and Pb–Pb collisions at sNN = 5.02TeVare studied using the ALICE detector based on the integral correlator pTpT.The correlator strength is found to decreasemonotonically with increasing produced charged-particle multiplicity measured at midrapidity in all three systems. In Xe–Xe and Pb–Pb collisions, the multiplicity dependence of the correlator deviates significantly from a simple power-law scaling as well as from the predictions of theHIJING andAMPTmodels. The observed deviation from power-law scaling is expected from transverse radial flow in semicentral to central Xe–Xe and Pb–Pb collisions. In pp collisions, the correlation strength is also studied by classifying the events based on the transverse spherocity, S0, of the particle production at midrapidity, used as a proxy for the presence of a pronounced back-to-back jet topology. Lowspherocity (jetty) events feature a larger correlation strength than those with high spherocity (isotropic). The strength and multiplicity dependence of jetty and isotropic events are well reproduced by calculations with the PYTHIA 8 and EPOS LHC models.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,072 contributors for this article]
(2025).
Light neutral-meson production in pp collisions at √s = 13 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(8).
doi:
10.1007/JHEP08(2025)035.
Full text in Research Archive
Show summary
The momentum-differential invariant cross sections of π0 and η mesons are reported for pp collisions at √s = 13 TeV at midrapidity (|y| < 0.8). The measurement is performed in a broad transverse-momentum range of 0.2 < pT < 200 GeV/c and 0.4 < pT < 60 GeV/c for the π0 and η, respectively, extending the pT coverage of previous measurements. Transverse-mass-scaling violation of up to 60% at low transverse momentum has been observed, agreeing with measurements at lower collision energies. Transverse Bjorken x (xT) scaling of the π0 cross sections at LHC energies is fulfilled with a power-law exponent of n = 5.01 ± 0.05, consistent with values obtained for charged pions at similar collision energies. The data are compared to predictions from next-to-leading order perturbative QCD calculations, where the π0 spectrum is best described using the CT18 parton distribution function and the NNFF1.0 or BDSS fragmentation function. Expectations from PYTHIA8 and EPOS LHC overestimate the spectrum for the π0 and are not able to describe the shape and magnitude of the η spectrum. The charged-particle multiplicity dependent π0 and η pT spectra show the expected change of the spectral shape, characterized by a flatter slope with increasing multiplicity. This is demonstrated across a broad transverse-momentum range and up to events with a charged-particle multiplicity exceeding five times the mean value in minimum bias collisions. The η/π0 ratio depends on the charged-particle multiplicity for pT < 4 GeV/c. PYTHIA8 and EPOS LHC qualitatively explain this behavior with an increasing contribution from the feed-down of heavier particles to the π0 spectrum.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,070 contributors for this article]
(2025).
Studying charm hadronisation into baryons with azimuthal correlations of Λ+ c with charged particles in pp collisions at √𝑠 = 13 TeV.
Physics Letters B.
ISSN 0370-2693.
868.
doi:
10.1016/j.physletb.2025.139681.
Full text in Research Archive
Show summary
The distribution of angular correlations between prompt charm hadrons and primary charged particles in pp collisions is sensitive to the charm-quark hadronisation process. In this letter, charm-baryon correlations are measured for the first time by studying the azimuthal-angle difference between charged particles and prompt Λ+ c baryons produced in pp collisions at a centre-of-mass energy of √𝑠 = 13 TeV, with the ALICE detector. Λ+ c baryons are reconstructed at midrapidity (|𝑦| < 0.5) in the transverse-momentum interval 3 < 𝑝T < 16 GeV/𝑐, and correlated with charged particles with 𝑝T > 0.3 GeV/𝑐 and pseudorapidity |𝜂| < 0.8. For 3 < 𝑝Λ+ c ,D T < 5 GeV/𝑐, the comparison with published measurements of D-meson and charged-particle correlations in the same collision system hints at a larger number of low-momentum particles associated with Λ+ c -baryon triggers than with D-meson triggers, both in the collinear and opposite directions with respect to the trigger particle. These differences can be quantified by the comparison of the properties of the near- and away-side correlation peaks, and are not reproduced by predictions of various Monte Carlo event generators, generally underpredicting the associated particle yields at 𝑝assoc T < 1 GeV/𝑐. This tension between Λ+ c -baryon and D-meson associated peak yields could suggest a modified fragmentation of the charm quark, or a different hadronisation process, when a charm baryon is produced in the final state.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,070 contributors for this article]
(2025).
Multiplicity-dependent inclusive J/ψ production at forward rapidity in pp collisions at √s = 13 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(7).
doi:
10.1007/JHEP07(2025)238.
Full text in Research Archive
Show summary
This paper presents a study of the inclusive forward J/ψ yield as a function of forward charged-particle multiplicity in pp collisions at √s = 13TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative J/ψ yields and relative charged-particle multiplicities with respect to these quantities obtained in
inelastic collisions having at least one charged particle in the pseudorapidity range |η| < 1. The J/ψ mesons are reconstructed via their decay into μ+μ− pairs in the forward rapidity region (2.5 < y < 4). The relative multiplicity is estimated in the forward pseudorapidity range which overlaps with the J/ψ rapidity region. The results show a steeper-than-linear increase of the J/ψ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,075 contributors for this article]
(2025).
Charged-particle multiplicity distributions over a wide pseudorapidity range in p–Pb collisions at √sNN = 5.02 TeV.
European Physical Journal C.
ISSN 1434-6044.
85(8).
doi:
10.1140/epjc/s10052-025-14577-0.
Full text in Research Archive
Show summary
This paper presents the primary charged-particle multiplicity distributions in proton–lead collisions at a centre-of-mass energy per nucleon–nucleon collision of √sNN = 5.02 TeV. The distributions are reported for non-single diffractive collisions in different pseudorapidity ranges.The measurements are performed using the combined information from the Silicon Pixel Detector and the Forward Multiplicity Detector of ALICE. The multiplicity distributions are parametrised with a double negative binomial distribution function which provides satisfactory descriptions of the distributions for all the studied pseudorapidity intervals. The data are compared to models and analysed quantitatively, evaluating the first four moments (mean, standard deviation, skewness, and kurtosis). The shape evolution of the measured multiplicity distributions is studied in terms of KNO variables and it is found that none of the considered models reproduces the measurements. This paper also reports on the average charged-particle multiplicity, normalised by the average number of participating nucleon pairs, as a function of the collision energy. The multiplicity results are then compared to measurements made in proton–proton and nucleus–nucleus collisions across a wide range of collision energies.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,069 contributors for this article]
(2025).
First measurement of D*+vector meson spin alignment in Pb–Pb collisions at √sNN = 5.02TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(10).
doi:
10.1007/JHEP10(2025)094.
Full text in Research Archive
Show summary
The first measurement of prompt D∗+-meson spin alignment in ultrarelativistic heavy-ion collisions with respect to the direction orthogonal to the reaction plane is presented.
The spin alignment is quantified by measuring the element ρ00 of the diagonal spin-density matrix for prompt D∗+ mesons with 4 < pT < 30 GeV/c in two rapidity intervals, |y| < 0.3
and 0.3 < |y| < 0.8, in central (0–10%) and midcentral (30–50%) Pb–Pb collisions at √sNN = 5.02TeV. Evidence of spin alignment ρ00 > 1/3 has been found for pT > 15 GeV/c
and 0.3 < |y| < 0.8 with a significance of 3.1σ. The measured spin alignment of prompt D∗+ mesons is compared with the one of inclusive J/ψ mesons measured at forward rapidity
(2.5 < y < 4).
-
Acharya, S.; Adamová, D.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L. & Agnello, M.
[Show all 1,068 contributors for this article]
(2025).
Exclusive photoproduction of excited ρ mesons decaying to four pions in ultraperipheral Pb–Pb collisions at √sNN = 5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
872.
doi:
10.1016/j.physletb.2025.140006.
Full text in Research Archive
Show summary
The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-flavour vector mesons. The measurement of coherently photoproduced 𝜋+𝜋−𝜋+𝜋− final states in ultraperipheral Pb–Pb collisions at √ 𝑠NN = 5.02 TeV is presented for the first time. The cross section, d𝜎/d𝑦, times the branching ratio (𝜌 → 𝜋+𝜋+𝜋−𝜋−) is found to be 47.8 ± 2.3 (stat.) ± 7.7 (syst.) mb in the rapidity interval |𝑦| < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including interference with a non-resonant contribution results in the mass and width values being too far from those reported in PDG, while the production of two interfering resonances, 𝜌(1450) and 𝜌(1700), also provides a good description of the data. The values of the masses (𝑚) and widths (Γ) of the resonances extracted from the fit assuming two interfering resonances are 𝑚1 = 1385 ± 14 (stat.) ± 3 (syst.) MeV/𝑐2, Γ1 = 431 ± 36 (stat.) ± 82 (syst.) MeV/𝑐2, 𝑚2 = 1663 ± 13 (stat.) ± 22 (syst.) MeV/𝑐2 and Γ2 = 357 ± 31 (stat.) ± 49 (syst.) MeV/𝑐2, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions.
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,071 contributors for this article]
(2025).
Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at √sNN = 5.02 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(8).
doi:
10.1007/JHEP08(2025)210.
Full text in Research Archive
Show summary
Correlations among conserved quantum numbers, such as the net-electric charge, the net-baryon, and the net-strangeness in heavy-ion collisions, are crucial for exploring the
QCD phase diagram. In this paper, these correlations are investigated using net-proton number (as a proxy for the net-baryon), net-kaon number (for the net-strangeness), and
net-charged particle number in Pb-Pb collisions at √sNN = 5.02TeV with the ALICE detector. The observed correlations deviate from the Poissonian baseline, with a more pronounced
deviation at LHC energies than at RHIC. Theoretical calculations of the Thermal-FIST hadron resonance gas model, HIJING, and EPOS LHC event generators are compared with
experimental results, where a significant impact of resonance decays is observed. Thermal-FIST calculations under the grand canonical and canonical ensembles highlight significant
differences, underscoring the role of local charge conservation in explaining the data. Recent lattice QCD studies have demonstrated that the magnetic field generated by spectator protons in heavy-ion collisions affects susceptibility ratios, in particular those related to the net-electric charge and the net-baryon numbers. The experimental findings are in qualitative agreement with the expectations of lattice QCD.
-
-
-
Acharya, S.; Agarwal, A.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,072 contributors for this article]
(2025).
Exploring nuclear structure with multiparticle azimuthal correlations at the LHC.
Physics Letters B.
ISSN 0370-2693.
869.
doi:
10.1016/j.physletb.2025.139855.
Full text in Research Archive
Show summary
Details of the nuclear structure of 129Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe–Xe collisions at a centre-of-mass energy per nucleon pair √𝑠NN = 5.44 TeV with the ALICE detector at the LHC. The results are compared with
those from Pb–Pb collisions at √𝑠NN = 5.02 TeV for a baseline, given that the 208Pb nucleus exhibits a very weak deformation. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with
different values of nuclear parameters, the one using a nuclear diffuseness parameter of 𝑎0 = 0.492 and a nuclear quadrupole deformation parameter of 𝛽2 = 0.207 provides a better description of the presented flow measurements. These studies represent the first systematic exploration of nuclear structure at TeV energies, utilizing a
comprehensive set of anisotropic flow observables. The measurements serve as a critical experimental benchmark for rigorously testing the interplay between nuclear structure inputs and heavy-ion theoretical models.
-
-
Abualrob, I. J.; Acharya, S.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,068 contributors for this article]
(2025).
Study of ⟨pT⟩ and its higher moments, and extraction of the speed of sound in Pb-Pb collisions with ALICE.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(11).
doi:
10.1007/JHEP11(2025)076.
Full text in Research Archive
Show summary
Ultrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, cs. This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in with respect to the relative change in the average charged-particle density measured at mid-rapidity. This study reports the event-average of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured is found to strongly depend on the exploited centrality estimator and ranges between 0.1146±0.0028 (stat.)±0.0065 (syst.) and 0.4374±0.0006 (stat.)±0.0184 (syst.) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [pT] distribution.
-
-
-
-
-
-
Acharya, S.; Adamová, D.; Rinella, G. Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,055 contributors for this article]
(2025).
Dielectron production in central Pb-Pb collisions at √s<inf>NN</inf>= 5.02 TeV.
Physical Review C.
ISSN 2469-9985.
112(5),
p. 0549061–05490627.
doi:
10.1103/xl6m-vbqk.
Full text in Research Archive
Show summary
The first measurement of the e+e− pair production at midrapidity and low invariant mass in central Pb-Pb
collisions at √sNN = 5.02 TeV at the Large Hadron Collider is presented. The yield of e+e− pairs is compared
with a cocktail of expected hadronic decay contributions in the invariant mass (mee) and pair transverse
momentum (pT,ee) ranges mee < 3.5 GeV/c2 and pT,ee < 8 GeV/c. For 0.18 < mee < 0.5 GeV/c2 the ratio of
data to the cocktail of hadronic contributions amounts to 1.40 ± 0.11 (stat.) ± 0.23 (syst.) ± 0.16 (cocktail) and
1.42 ± 0.11 (stat.) ± 0.23 (syst.)
+0.24
−0.29 (cocktail), including or not including medium effects in the estimation
of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an
additional contribution of thermal e+e− pairs from the hadronic and partonic phases. In the intermediate-mass
range (1.2 < mee < 2.6 GeV/c2), the pair transverse impact parameter of the e+e− pairs (DCAee, where “DCA”
denotes “distance of closest approach”) is used for the first time in Pb-Pb collisions to separate displaced
dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction
point. The data are consistent with a suppression of e+e− pairs from cc and an additional prompt component.
Finally, the first direct-photon measurement in the 10% most central Pb-Pb collisions at √sNN = 5.02 TeV is
reported via the study of virtual direct photons in the transverse momentum range 1 < pT < 5 GeV/c. A model
including prompt photons, as well as photons from the preequilibrium and fluid-dynamic phases, can reproduce
the result, while being at the upper edge of the data uncertainties.
-
Peitzmann, T.; Alme, Johan; Barthel, R.; Borshchov, V.; Bosley, R. & Brink, A. van den
[Show all 24 contributors for this article]
(2025).
Ultra-high granularity electromagnetic calorimetry – Results from the EPICAL-2 prototype and perspectives for digital calorimeters.
The European Physical Journal Conferences.
ISSN 2101-6275.
320.
doi:
10.1051/epjconf/202532000024.
Full text in Research Archive
Show summary
An advanced prototype of a digital pixel calorimeter, EPICAL-2, has been constructed using ALPIDE MAPS sensors. It has been successfully tested with cosmic muons and with test beams at DESY and the CERN SPS. We will report on recent updates of performance results, with good linearity and resolution. Comparisons to detailed MC simulations are made and show good understanding of the technology. The spatial precision of event-by-event measurements of the showers allows unprecedented studies of the shower shape. The detector features two-shower separation capabilities at extremely small distances. We will also discuss the limitations of the currently used sensor technology and perspectives for future development of digital calorimetry.
-
-
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,046 contributors for this article]
(2025).
Multiplicity dependence of ϒ production at forward rapidity in pp collisions at s=13 TeV.
Nuclear Physics B.
ISSN 0550-3213.
1011.
doi:
10.1016/j.nuclphysb.2024.116786.
Full text in Research Archive
Show summary
The measurement of Υ(1S), Υ(2S), and Υ(3S) yields as a function of the charged-particle multiplicity density, d𝑁ch∕d𝜂, using the ALICE experiment at the LHC, is reported in pp collisions at √𝑠 = 13 TeV. The Υ meson yields are measured at forward rapidity (2.5 <𝑦< 4) in the dimuon decay channel, whereas the charged-particle multiplicity is dfined at central rapidity (|𝜂| < 1). Both quantities are divided by their average value in minimum bias events to compute the self-normalized quantities. The increase of the self-normalized Υ(1S), Υ(2S), and Υ(3S) yields is found to be compatible with a linear scaling with the self-normalized d𝑁ch∕d𝜂, within the uncertainties. The self-normalized yield ratios of excited-to-ground Υ states are compatible with unity within uncertainties. Similarly, the measured double ratio of the self-normalized Υ(1S) to the self-normalized J/𝜓 yields, both measured at forward rapidity, is compatible with unity for self-normalized charged-particle multiplicities beyond one. The measurements are compared with theoretical predictions incorporating initial or final state effects.
-
-
Acharya, S.; Adamová, D.; Agarwal, A.; Rinella, Rinella Aglieri; Aglietta, L. & Agnello, M.
[Show all 1,082 contributors for this article]
(2025).
Measurement of HΛ3 production in Pb–Pb collisions at s<inf>NN</inf>=5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
860.
doi:
10.1016/j.physletb.2024.139066.
Full text in Research Archive
Show summary
The first measurement of
and
differential production with respect to transverse momentum and centrality in Pb–Pb collisions at
TeV is presented. The
has been reconstructed via its two-charged-body decay channel, i.e.,
. A Blast-Wave model fit of the
-differential spectra of all nuclear species measured by the ALICE collaboration suggests that the
kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of
and
is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements.
-
-
-
-
-
-
-
-
Acharya, S.; Hernandez, R. Acosta; Adamová, D.; Adler, A.; Adolfsson, J. & Agguiaro, D.
[Show all 1,372 contributors for this article]
(2024).
ALICE upgrades during the LHC Long Shutdown 2.
Journal of Instrumentation (JINST).
19(5).
doi:
10.1088/1748-0221/19/05/P05062.
Full text in Research Archive
Show summary
A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature.
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 973 contributors for this article]
(2024).
Search for jet quenching effects in high-multiplicity pp collisions at s=13 TeV via di-jet acoplanarity.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2024(5).
doi:
10.1007/JHEP05(2024)229.
Full text in Research Archive
Show summary
The ALICE Collaboration reports a search for jet quenching effects in highmultiplicity (HM) proton-proton collisions at √ s = 13TeV, using the semi-inclusive azimuthaldifference distribution Δφ of charged-particle jets recoiling from a high transverse momentum (high-pT,trig) trigger hadron. Jet quenching may broaden the Δφ distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a pT,trig-differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. Detailed analysis of these data and simulations show that the azimuthal broadening is due to bias of the HM selection towards events with multiple jets in the final state. The identification of this bias has implications for all jet quenching searches where selection is made on the event activity.
-
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,056 contributors for this article]
(2024).
First Measurement of the |t | Dependence of Incoherent J/ψ Photonuclear Production.
Physical Review Letters.
ISSN 0031-9007.
132(16).
doi:
10.1103/PhysRevLett.132.162302.
Full text in Research Archive
Show summary
The first measurement of the cross section for incoherent photonuclear production of 𝐽/𝜓 vector mesons as a function of the Mandelstam |𝑡| variable is presented. The measurement was carried out with the ALICE detector at midrapidity, |𝑦| <0.8, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of √𝑠NN=5.02 TeV. This rapidity interval corresponds to a Bjorken-𝑥 range (0.3–1.4)×10−3. Cross sections are given in five |𝑡| intervals in the range 0.04<|𝑡|<1 GeV2 and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a |𝑡| dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data.
-
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,048 contributors for this article]
(2024).
K*(892)± resonance production in Pb-Pb collisions at sNN =5.02 TeV.
Physical Review C.
ISSN 2469-9985.
109(4).
doi:
10.1103/PhysRevC.109.044902.
Full text in Research Archive
Show summary
The production of K∗(892)± meson resonance is measured at midrapidity (|y| < 0.5) in Pb-Pb collisions at √sNN = 5.02 TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel K∗(892)± → K0Sπ±. The transverse momentum distributions are obtained for various centrality intervals in the pT range of 0.4-16 GeV/c. Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for K∗(892)0 within uncertainties. The pT-integrated yield ratio 2 K∗(892)± /(K+ + K−) in central Pb-Pb collisions shows a significant suppression at a level of 9.3σ relative to pp collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and MUSIC + SMASH simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas MUSIC + SMASH simulations tend to overpredict the particle yield ratio. These observations, along with the kinetic freeze-out temperatures extracted from the yields measured for light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which decreases with increasing collision centrality percentile. The pT-differential yield ratios 2 K∗(892)±/(K+ + K−) and 2 K∗(892)±/(π+ + π−) are presented and compared with measurements in pp collisions at√s = 5.02 TeV.Both particle ratios are found to be suppressed by up to a factor of five at pT < 2.0 GeV/c in central Pb-Pb collisions and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor (RAA) shows a smooth evolution with centrality and is found to be below unity at pT > 8 GeV/c, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,030 contributors for this article]
(2024).
Measurements of inclusive J/ψ production at midrapidity and forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
849.
doi:
10.1016/j.physletb.2024.138451.
Full text in Research Archive
Show summary
The measurements of the inclusive J∕ψ yield at midrapidity (|y| < 0.9) and forward rapidity (2.5 < y < 4) in Pb-Pb collisions at √ sNN = 5.02 TeV With the ALICE detector at the LHC are reported. The inclusive J∕ψ Production yelds and nuclear modification factors, RAA, are measured as a function of the collision centrality, J∕ψ transverse momentum (pT), and rapidity. The J∕ψ average transverse momentum and squared transverse momentum ((pT) and (p2T)) are evaluated as a function of the centrality at midrapidity. Compared to the previous Alice publications, here the entire Pb-Pb collisions dataset collected during the LHC Run 2 is used, which improves the precision of the measurements and extends the pT coverage. The pT-integrated RAA shows a hint of an increasing trend towards unity from semicentral to central collisions at midrapiditym while it is flat at forward rapidity. The pT.differential RAA shows a strong suppression at high pT with less suppression at low pT where it reaches a larger value at midrapidity compared to forward rapidity. The ratio of the pT-integrated yelds of J∕ψ to those of D0 mesons is reported for the first time for the central semicentral event classes at midrapidity. Model calculations implementing charmonium production via the coalescence of charm quarks and antiquarks during the fireball evolution (transport models) or in a statistical approach with thermal weights are in good agreement with the data at low pT. At higher pT, the data are well described by transport models and a model based on energy loss in the strongly-interacting medium produced in nuclear collisions at the LHC.
-
Acharya, S.; Adamová, D.; Agarwal, A.; Rinella, Rinella Aglieri; Aglietta, L. & Agnello, M.
[Show all 976 contributors for this article]
(2024).
Measurement of beauty-quark production in pp collisions at s = 13 TeV via non-prompt D mesons.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2024(10).
doi:
10.1007/JHEP10(2024)110.
Full text in Research Archive
Show summary
The pT-differential production cross sections of non-prompt D0, D+, and D+s mesons originating from beauty-hadron decays are measured in proton–proton collisions at a centre-of-mass energy √ s = 13TeV. The measurements are performed at midrapidity, |y| < 0.5, with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, fs/(fu+ fd), is found to be 0.114 ± 0.016 (stat.) ± 0.006 (syst.) ± 0.003 (BR) ± 0.003 (extrap.). This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centreof- mass energy is investigated by comparing the results obtained at √ s = 5.02 and 13TeV, showing a hardening of the non-prompt D-meson pT-differential production cross section at higher √ s. Finally, the bb production cross section per unit of rapidity at midrapidity is calculated from the non-prompt D0, D+, D+s , and Λ+c hadron measurements, obtaining dσ/dy = 75.2 ± 3.2 (stat.) ± 5.2 (syst.)+12.3 −3.2 (extrap.) μb.
-
-
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,046 contributors for this article]
(2024).
Femtoscopic correlations of identical charged pions and kaons in pp collisions at √s=13 TeV with event-shape selection.
Physical Review C.
ISSN 2469-9985.
109(2).
doi:
10.1103/PhysRevC.109.024915.
Full text in Research Archive
Show summary
Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the CERN Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from high-multiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE Collaboration on charged pion and kaon pairs produced in 𝑝𝑝 collisions at √𝑠=13TeV from the LHC to study possible collectivity in 𝑝𝑝 collisions. The event-shape analysis method based on transverse sphericity is used to select for spherical versus jetlike events, and the effects of this selection on the femtoscopic radii for both charged pion and kaon pairs are studied. This is the first time this selection method has been applied to charged kaon pairs. An approximate transverse-mass scaling of the radii is found in all multiplicity ranges studied when the difference in the Lorentz boost for pions and kaons is taken into account. This observation does not support the hypothesis of collective expansion of hot and dense matter that should only occur in high-multiplicity events. A possible alternate explanation of the present results is based on a scenario of common emission conditions for pions and kaons in 𝑝𝑝 collisions for the multiplicity ranges studied.
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,030 contributors for this article]
(2024).
Measurement of the radius dependence of charged-particle jet suppression in Pb–Pb collisions at s<inf>NN</inf>=5.02TeV.
Physics Letters B.
ISSN 0370-2693.
849.
doi:
10.1016/j.physletb.2023.138412.
Full text in Research Archive
Show summary
The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb–Pb collision data at a center-of-mass energy per nucleon–nucleon collision √s NN = 5.02 TeV. Charged-particle jets are reconstructed using the anti-kT algorithm with resolution parameters R = 0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and R = 0.2, 0.4, 0.6 in central (0–10%), semi-central (30–50%), and peripheral (60–80%) Pb–Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet pT ≥ 40 GeV/c at R = 0.6 in central Pb–Pb collisions. This is an important step for discriminating different models of jet quenching in the quark–gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet-quenching models with varying levels of agreement.
-
-
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,036 contributors for this article]
(2024).
ALICE luminosity determination for Pb-Pb collisions at √sNN= 5.02 TeV.
Journal of Instrumentation (JINST).
19(2).
doi:
10.1088/1748-0221/19/02/P02039.
Full text in Research Archive
Show summary
Luminosity determination within the ALICE experiment is based on the measurement, in van der Meer scans, of the cross sections for visible processes involving one or more detectors (visible cross sections). In 2015 and 2018, the Large Hadron Collider provided Pb–Pb collisions at a centre-of-mass energy per nucleon pair of √𝑠NN = 5.02 TeV. Two visible cross sections, associated with particle detection in the Zero Degree Calorimeter (ZDC) and in the V0 detector, were measured in a van der Meer scan. This article describes the experimental set-up and the analysis procedure, and presents the measurement results. The analysis involves a comprehensive study of beam-related effects and an improved fitting procedure, compared to previous ALICE studies, for the extraction of the visible cross section. The resulting uncertainty of both the ZDC-based and the V0-based luminosity measurement for the full sample is 2.5%. The inelastic cross section for hadronic interactions in Pb–Pb collisions at √𝑠NN = 5.02 TeV, obtained by efficiency correction of the V0-based visible cross section, was measured to be 7.67 ± 0.25 b, in agreement with predictions using the Glauber model.Luminosity determination within the ALICE experiment is based on the measurement, in van der Meer scans, of the cross sections for visible processes involving one or more detectors (visible cross sections). In 2015 and 2018, the Large Hadron Collider provided Pb–Pb collisions at a centre-of-mass energy per nucleon pair of √𝑠NN = 5.02 TeV. Two visible cross sections, associated with particle detection in the Zero Degree Calorimeter (ZDC) and in the V0 detector, were measured in a van der Meer scan. This article describes the experimental set-up and the analysis procedure, and presents the measurement results. The analysis involves a comprehensive study of beam-related effects and an improved fitting procedure, compared to previous ALICE studies, for the extraction of the visible cross section. The resulting uncertainty of both the ZDC-based and the V0-based luminosity measurement for the full sample is 2.5%. The inelastic cross section for hadronic interactions in Pb–Pb collisions at √𝑠NN = 5.02 TeV, obtained by efficiency correction of the V0-based visible cross section, was measured to be 7.67 ± 0.25 b, in agreement with predictions using the Glauber model.
-
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,044 contributors for this article]
(2024).
Observation of abnormal suppression of f0(980) production in p–Pb collisions at √sNN = 5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
853.
doi:
10.1016/j.physletb.2024.138665.
Full text in Research Archive
Show summary
The dependence of f0(980) production on the final-state charged-particle multiplicity in p–Pb collisions at √𝑠NN = 5.02 TeV is reported. The production of f0(980) is measured with the ALICE detector via the f0(980) → 𝜋+𝜋− decay channel in a midrapidity region of −0.5 < 𝑦 < 0. Particle yield ratios of f0(980) to 𝜋 and K∗(892)0 are found to be decreasing with increasing charged-particle multiplicity. The magnitude of the suppression of the f0(980)/𝜋 and f0(980)/K∗(892)0 yield ratios is found to be dependent on the transverse momentum 𝑝T, suggesting different mechanisms responsible for the measured effects. Furthermore, the nuclear modification factor 𝑄pPb of f0(980) is measured in various multiplicity ranges. The 𝑄pPb shows a strong suppression of the f0(980) production in the 𝑝T region up to about 4 GeV/𝑐. The results on the particle yield ratios and 𝑄pPb for f0(980) may help to understand the late hadronic phase in p–Pb collisions and the nature of the internal structure of f0(980) particle.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,024 contributors for this article]
(2024).
Search for the Chiral Magnetic Effect with charge-dependent azimuthal correlations in Xe–Xe collisions at √sNN=5.44 TeV.
Physics Letters B.
ISSN 0370-2693.
856.
doi:
10.1016/j.physletb.2024.138862.
Full text in Research Archive
Show summary
Charge-dependent two- and three-particle correlations measured in Xe–Xe collisions at √𝑠NN = 5.44 TeV are presented. Results are obtained for charged particles in the pseudorapidity range |𝜂| < 0.8 and transverse momentum interval 0.2 ≤ 𝑝T < 5.0 GeV/𝑐 for different collision centralities. The three-particle correlator 𝛾𝛼𝛽 ≡ ⟨cos(𝜑𝛼 + 𝜑𝛽 − 2Ψ2)⟩, calculated for different combinations of charge sign 𝛼 and 𝛽, is expected to be sensitive to the presence of the Chiral Magnetic Effect (CME). Its magnitude is similar to the one observed in Pb–Pb collisions in contrast to a smaller CME signal in Xe–Xe collisions than in Pb–Pb collisions predicted by Monte Carlo (MC) calculations including a magnetic field induced by the spectator protons. These observations point to a large nonCME contribution to the correlator. Furthermore, the charge dependence of 𝛾𝛼𝛽 can be described by a blast wave model calculation that incorporates background effects and by the Anomalous Viscous Fluid Dynamics model with values of the CME signal consistent with zero. The Xe–Xe and Pb–Pb results are combined with the expected CME signal dependence on the system size from the MC calculations including a magnetic field to obtain the fraction of CME contribution in 𝛾𝛼𝛽 , 𝑓CME. The CME fraction is compatible with zero for the 30% most central events in both systems and then becomes positive. This yields an upper limit of 2% (3%) and 25% (32%) at 95% (99.7%) confidence level for the CME signal contribution to 𝛾𝛼𝛽 in the 0–70% Xe–Xe and Pb–Pb collisions, respectively.
-
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,053 contributors for this article]
(2024).
Measurements of long-range two-particle correlation over a wide pseudorapidity range in p–Pb collisions at sNN = 5.02 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2024(1).
doi:
10.1007/JHEP01(2024)199.
Full text in Research Archive
Show summary
Correlations in azimuthal angle extending over a long range in pseudorapidity between particles, usually called the “ridge” phenomenon, were discovered in heavy-ion collisions, and later found in pp and p–Pb collisions. In large systems, they are thought to arise from the expansion (collective flow) of the produced particles. Extending these measurements over a wider range in pseudorapidity and final-state particle multiplicity is important to understand better the origin of these long-range correlations in small collision systems. In this Letter, measurements of the long-range correlations in p–Pb collisions at √sNN TeV are extended to a pseudorapidity gap of ∆η ~ 8 between particles using the ALICE forward multiplicity detectors. After suppressing non-flow correlations, e.g., from jet and resonance decays, the ridge structure is observed to persist up to a very large gap of ∆η ~ 8 for the first time in p–Pb collisions. This shows that the collective flow-like correlations extend over an extensive pseudorapidity range also in small collision systems such as p–Pb collisions. The pseudorapidity dependence of the second-order anisotropic flow coefficient, v2(η), is extracted from the long-range correlations. The v2(η) results are presented for a wide pseudorapidity range of –3.1 < η < 4.8 in various centrality classes in p–Pb collisions. To gain a comprehensive understanding of the source of anisotropic flow in small collision systems, the v2(η) measurements are compared with hydrodynamic and transport model calculations. The comparison suggests that the final-state interactions play a dominant role in developing the anisotropic flow in small collision systems.
-
-
Acharya, S.; Adamová, D.; Rinella, G. Aglieri; Aglietta, L.; Agnello, M. & Agrawal, N.
[Show all 1,058 contributors for this article]
(2024).
Multiplicity dependence of charged-particle intra-jet properties in pp collisions at √s = 13 TeV.
European Physical Journal C.
ISSN 1434-6044.
84(10).
doi:
10.1140/epjc/s10052-024-13228-0.
Full text in Research Archive
Show summary
The first measurement of the multiplicity dependence of intra-jet properties of leading charged-particle jets in proton–proton (pp) collisions is reported. The mean chargedparticle multiplicity and jet fragmentation distributions are measured in minimum-bias and high-multiplicity pp collisions at center-of-mass energy √s = 13 TeV using the ALICE detector. Jets are reconstructed from charged particles produced in the midrapidity region (|η| < 0.9) using the sequential recombination anti-kT algorithm with jet resolution parameters R = 0.2, 0.3, and 0.4 for the transverse momentum (pT) interval 5–110 GeV/c. The highmultiplicity events are selected by the forward V0 scintillator detectors. The mean charged-particle multiplicity inside the leading jet cone rises monotonically with increasing jet pT in qualitative agreement with previous measurements at lower energies. The distributions of jet fragmentation function variables zch and ξ ch are measured for different jet-pT intervals. Jet-pT independent fragmentation of leading jets is observed for wider jets except at high- and low-zch values. The observed “hump-backed plateau” structure in the ξ ch distribution indicates suppression of low-pT particles. In high-multiplicity events, an enhancement of the fragmentation probability of low-zch particles accompanied by a suppression of high-zch particles is observed compared to minimum-bias events. This behavior becomes more prominent for low-pT jets with larger jet radius. The results are compared with predictions of QCD-inspired event generators, PYTHIA 8 with Monash 2013 tune and EPOS LHC. It is found that PYTHIA 8 qualitatively reproduces the jet modification in high-multiplicity events except at high jet pT. These measurements provide important constraints to models of jet fragmentation.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,050 contributors for this article]
(2024).
The ALICE experiment: a journey through QCD.
European Physical Journal C.
ISSN 1434-6044.
84(8).
doi:
10.1140/epjc/s10052-024-12935-y.
Full text in Research Archive
Show summary
The ALICE experiment was proposed in 1993, to study strongly-interacting matter at extreme energy densities and temperatures. This proposal entailed a comprehensive investigation of nuclear collisions at the LHC. Its physics programme initially focused on the determination of the properties of the quark–gluon plasma (QGP), a deconfined state of quarks and gluons, created in such collisions. The ALICE physics programme has been extended to cover a broader ensemble of observables related to Quantum Chromodynamics (QCD), the theory of strong interactions. The experiment has studied Pb–Pb, Xe–Xe, p–Pb and pp collisions in the multi-TeV centre of mass energy range, during the Run 1–2 data-taking periods at the LHC (2009–2018). The aim of this review is to summarise the key ALICE physics results in this endeavor, and to discuss their implications on the current understanding of the macroscopic and microscopic properties of strongly-interacting matter at the highest temperatures reached in the laboratory. It will review the latest findings on the properties of the QGP created by heavy-ion collisions at LHC energies, and describe the surprising QGP-like effects in pp and p–Pb collisions. Measurements of few-body QCD interactions, and their impact in unraveling the structure of hadrons and hadronic interactions, will be discussed. ALICE results relevant for physics topics outside the realm of QCD will also be touched upon. Finally, prospects for future measurements with the ALICE detector in the context of its planned upgrades will also be briefly described.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,030 contributors for this article]
(2024).
ψ (2S) Suppression in Pb-Pb Collisions at the LHC.
Physical Review Letters.
ISSN 0031-9007.
132(4).
doi:
10.1103/PhysRevLett.132.042301.
Full text in Research Archive
Show summary
The production of the 𝜓(2𝑆) charmonium state was measured with ALICE in Pb-Pb collisions at √𝑠NN =5.02 TeV, in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity (2.5 <𝑦 <4). The measurement of the ratio of the inclusive production cross sections of the 𝜓(2𝑆) and J/𝜓 resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region 𝑝𝑇<12 GeV/𝑐. The results are compared with the corresponding measurements in 𝑝𝑝 collisions, by forming the double ratio [𝜎𝜓(2𝑆)/𝜎𝐽/𝜓]Pb−Pb/[𝜎𝜓(2𝑆)/𝜎𝐽/𝜓]𝑝𝑝. It is found that in Pb-Pb collisions the 𝜓(2𝑆) is suppressed by a factor of ∼2 with respect to the 𝐽/𝜓. The 𝜓(2𝑆) nuclear modification factor 𝑅AA was also obtained as a function of both centrality and 𝑝𝑇. The results show that the 𝜓(2𝑆) resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to ∼3 with respect to 𝑝𝑝. Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of 𝑅AA with higher-𝑝𝑇 results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC.
-
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,042 contributors for this article]
(2024).
Pseudorapidity dependence of anisotropic flow and its decorrelations using long-range multiparticle correlations in Pb–Pb and Xe–Xe collisions.
Physics Letters B.
ISSN 0370-2693.
850.
doi:
10.1016/j.physletb.2024.138477.
Full text in Research Archive
Show summary
The pseudorapidity dependence of elliptic (𝑣�2), triangular (𝑣�3), and quadrangular (𝑣�4) flow coefficients of charged particles measured in Pb–Pb collisions at a centre-of-mass energy per nucleon pair of √𝑠�NN = 5.02 TeV and in Xe–Xe collisions at √𝑠�NN = 5.44 TeV with ALICE at the LHC are presented. The measurements are performed in the pseudorapidity range −3.5 < 𝜂� <5 for various centrality intervals using two- and multi-particle cumulants with the subevent method. The flow probability density function (p.d.f.) is studied with the ratio of flow coefficient 𝑣�2 calculated with four- and two-particle cumulant, and suggests that the variance of flow p.d.f. is independent of pseudorapidity. The decorrelation of the flow vector in the longitudinal direction is probed using two-particle correlations. The results measured with respect to different reference regions in pseudorapidity exhibit differences, argued to be a result of saturating decorrelation effect above a certain pseudorapidity separation, in contrast to previous publications which assign this observation to non-flow effects. The results are compared to 3 + 1 dimensional hydrodynamic and the AMPT transport model calculations. Neither of the models is able to simultaneously describe the pseudorapidity dependence of measurements of anisotropic flow and its fluctuations. The results presented in this work highlight shortcomings in our current understanding of initial conditions and subsequent system expansion in the longitudinal direction. Therefore, they provide input for its improvement.
-
-
Aehle, M.; Alme, Johan; Arata, C.; Arsene, Ionut Cristian; Bearden, I. & Bodova, Tea
[Show all 77 contributors for this article]
(2024).
Performance of the electromagnetic and hadronic prototype segments of the ALICE Forward Calorimeter.
Journal of Instrumentation (JINST).
19(7).
doi:
10.1088/1748-0221/19/07/P07006.
Full text in Research Archive
Show summary
We present the performance of a full-length prototype of the ALICE Forward Calorimeter (FoCal). The detector is composed of a silicon-tungsten electromagnetic sampling calorimeter with longitudinal and transverse segmentation (FoCal-E) of about 20X0 and a hadronic copper-scintillating-fiber calorimeter (FoCal-H) of about 5λint. The data were taken in various test beam campaigns between 2021 and 2023 at the CERN PS and SPS beam lines with hadron beams up to energies of 350 GeV, and electron beams up to 300 GeV. Regarding FoCal-E, we report a comprehensive analysis of its response to minimum ionizing particles across all pad layers, employing various operational modes including different pre-amplifier and bias voltage settings. The longitudinal shower profile of electromagnetic showers is measured with a layer-wise segmentation of 1X0. As a projection to the performance of the final detector in electromagnetic showers, we demonstrate linearity in the full energy range, and show that the energy resolution fulfills the requirements for the physics needs. Additionally, the performance to separate two-showers events was studied by quantifying the transverse shower width. Regarding FoCal-H, we report a detailed analysis of the response to hadron beams between 60 and 350 GeV. The results are compared to simulations obtained with a Geant4 model of the test beam setup, which in particular for FoCal-E are in good agreement with the data. The energy resolution of FoCal-E was found to be lower than 3% at energies larger than 100 GeV. The response of FoCal-H to hadron beams was found to be linear, albeit with a significant intercept that is about factor 2 larger than in simulations. Its resolution, which is non-Gaussian and generally larger than in simulations, was quantified using the FWHM, and decreases from about 16% at 100 GeV to about 11% at 350 GeV. The discrepancy to simulations, which is particularly evident at low hadron energies, needs to be further investigated.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,038 contributors for this article]
(2024).
Measurement of the fraction of jet longitudinal momentum carried by Λc+ baryons in pp collisions.
Physical Review D.
ISSN 2470-0010.
109(7).
doi:
10.1103/PhysRevD.109.072005.
Full text in Research Archive
Show summary
Recent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by Λþ c baryons, zch k , in hadronic collisions. The results are obtained in proton-proton (pp) collisions at ffiffi s p ¼ 13 TeV at the LHC, with Λþ c baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of 3 ≤ pΛþ c T < 15 GeV=c and 7 ≤ pjet ch T < 15 GeV=c, respectively. The zch k distribution is compared to a measurement of D0-tagged charged jets in pp collisions as well as to PYTHIA 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation.
-
Acharya, S.; Adamová, D.; Agarwal, A.; Rinella, Rinella Aglieri; Aglietta, L. & Agnello, M.
[Show all 1,063 contributors for this article]
(2024).
Investigating strangeness enhancement with multiplicity in pp collisions using angular correlations.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2024(9).
doi:
10.1007/JHEP09(2024)204.
Full text in Research Archive
Show summary
A study of strange hadron production associated with hard scattering processes and with the underlying event is conducted to investigate the origin of the enhanced production of strange hadrons in small collision systems characterised by large charged-particle multiplicities. For this purpose, the production of the single-strange meson K0 S and the double-strange baryon Ξ ± is measured, in each event, in the azimuthal direction of the highest-pT particle (“trigger” particle), related to hard scattering processes, and in the direction transverse to it in azimuth, associated with the underlying event, in pp collisions at √ s = 5.02 TeV and √ s = 13 TeV using the ALICE detector at the LHC. The per-trigger yields of K0 S and Ξ ± are dominated by the transverse-to-leading production (i.e., in the direction transverse to the trigger particle), whose contribution relative to the toward-leading production is observed to increase with the event charged-particle multiplicity. The transverseto-leading and the toward-leading Ξ ±/K0 S yield ratios increase with the multiplicity of charged particles, suggesting that strangeness enhancement with multiplicity is associated with both hard scattering processes and the underlying event. The relative production of Ξ ± with respect to K0 S is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The K0 S and Ξ ± per-trigger yields and yield ratios are compared with predictions of three diferent phenomenological models, namely Pythia8.2 with the Monash tune, Pythia8.2 with ropes and EPOS LHC. The comparison shows that none of them can quantitatively describe either the transverse-to-leading or the toward-leading yields of K0 S and Ξ ±.
-
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,042 contributors for this article]
(2024).
Light-flavor particle production in high-multiplicity pp collisions at s= 13 TeV as a function of transverse spherocity.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2024(5).
doi:
10.1007/JHEP05(2024)184.
Full text in Research Archive
Show summary
Results on the transverse spherocity dependence of light-favor particle production (π, K, p, ϕ, K∗0 , K0 S , Λ, Ξ) at midrapidity in high-multiplicity pp collisions at √ s = 13 TeV were obtained with the ALICE apparatus. The transverse spherocity estimator (S pT=1 O ) categorizes events by their azimuthal topology. Utilizing narrow selections on S pT=1 O , it is possible to contrast particle production in collisions dominated by many soft initial interactions with that observed in collisions dominated by one or more hard scatterings. Results are reported for two multiplicity estimators covering diferent pseudorapidity regions. The S pT=1 O estimator is found to efectively constrain the hardness of the events when the midrapidity (|η| < 0.8) estimator is used. The production rates of strange particles are found to be slightly higher for soft isotropic topologies, and severely suppressed in hard jet-like topologies. These efects are more pronounced for hadrons with larger mass and strangeness content, and observed when the topological selection is done within a narrow multiplicity interval. This demonstrates that an important aspect of the universal scaling of strangeness enhancement with fnal-state multiplicity is that high-multiplicity collisions are dominated by soft, isotropic processes. On the contrary, strangeness production in events with jet-like processes is signifcantly reduced. The results presented in this article are compared with several QCD-inspired Monte Carlo event generators. Models that incorporate a two-component phenomenology, either through mechanisms accounting for string density, or thermal production, are able to describe the observed strangeness enhancement as a function of S pT=1 O .
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,056 contributors for this article]
(2024).
Photoproduction of K+K- Pairs in Ultraperipheral Collisions.
Physical Review Letters.
ISSN 0031-9007.
132(22).
doi:
10.1103/PhysRevLett.132.222303.
Full text in Research Archive
Show summary
𝐾+𝐾− pairs may be produced in photonuclear collisions, either from the decays of photoproduced 𝜙(1020) mesons or directly as nonresonant 𝐾+𝐾− pairs. Measurements of 𝐾+𝐾− photoproduction probe the couplings between the 𝜙(1020) and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of 𝐾+𝐾− pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct 𝐾+𝐾− production. There is significant 𝐾+𝐾− production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<𝑀𝐾𝐾<1.4 GeV/𝑐2 above the 𝜙(1020) resonance, for rapidity |𝑦𝐾𝐾|<0.8 and 𝑝𝑇,𝐾𝐾 <0.1 GeV/𝑐, the measured coherent photoproduction cross section is d𝜎/d𝑦=3.37±0.61(stat)±0.15(syst) mb. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system 𝑊𝛾Pb,𝑛 ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for 𝜙(1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of 𝜙(1020) decays, direct 𝐾+𝐾− photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct 𝐾+𝐾− photoproduction are presented.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,042 contributors for this article]
(2024).
Measurement of the low-energy antitriton inelastic cross section.
Physics Letters B.
ISSN 0370-2693.
848.
doi:
10.1016/j.physletb.2023.138337.
Full text in Research Archive
Show summary
In this Letter, the first measurement of the inelastic cross section for antitriton–nucleus interactions is reported, covering the momentum range of 0.8 ≤ 𝑝 < 2.4 GeV∕𝑐. The measurement is carried out using data recorded with the ALICE detector in pp and Pb–Pb collisions at a centre-of-mass energy per nucleon of 13 TeV and 5.02 TeV, respectively. The detector material serves as an absorber for antitriton nuclei. The raw yield of (anti)triton nuclei measured with the ALICE apparatus is compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of (anti)particles through matter, allowing one to quantify the inelastic interaction probability in the detector material. This analysis complements the measurement of the inelastic cross section of antinuclei up to 𝐴 = 3 carried out by the ALICE Collaboration, and demonstrates the feasibility of the study of the isospin dependence of inelastic interaction cross section with the analysis techniques presented in this Letter.
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,052 contributors for this article]
(2024).
System-size dependence of the hadronic rescattering effect at energies available at the CERN Large Hadron Collider.
Physical Review C.
ISSN 2469-9985.
109(1).
doi:
10.1103/PhysRevC.109.014911.
Full text in Research Archive
Show summary
The first measurements of 𝐾*(892)0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at √𝑠𝑁𝑁=5.44 TeV and 𝑝𝑝 collisions at√𝑠=5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity (|𝑦| < 0.5) using the hadronic decay channel 𝐾*0 →𝐾±𝜋∓. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of 𝐾*0, and yield ratios of resonance to stable hadron (𝐾*0/𝐾) are compared across different collision systems (𝑝𝑝, 𝑝-Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of 𝐾*0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of 𝐾*0 in Xe-Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas–partial chemical equilibrium model.
-
Acharya, S.; Adamová, D.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,034 contributors for this article]
(2024).
Modification of charged-particle jets in event-shape engineered Pb–Pb collisions at √sNN=5.02 TeV.
Physics Letters B.
ISSN 0370-2693.
851.
doi:
10.1016/j.physletb.2024.138584.
Full text in Research Archive
Show summary
Charged-particle jet yields have been measured in semicentral Pb–Pb collisions at center-of-mass energy per nucleon–nucleon collision TeV with the ALICE detector at the LHC. These yields are reported as a function of the jet transverse momentum, and further classified by their angle with respect to the event plane and the event shape, characterized by ellipticity, in an effort to study the path-length dependence of jet quenching. Jets were reconstructed at midrapidity from charged-particle tracks using the antialgorithm with resolution parameters R = 0.2 and 0.4, with event-plane angle and event-shape values determined using information from forward scintillating detectors. The results presented in this letter show that, in semicentral Pb–Pb collisions, there is no significant difference between jet yields in predominantly isotropic and elliptical events. However, out-of-plane jets are observed to be more suppressed than in-plane jets. Further, this relative suppression is greater for low transverse momentum (< 50 GeV/c) R = 0.2 jets produced in elliptical events, with out-of-plane to in-plane jet-yield ratios varying up to 5.2σ between different event-shape classes. These results agree with previous studies indicating that jets experience azimuthally anisotropic suppression when traversing the QGP medium, and can provide additional constraints on the path-length dependence of jet energy loss.
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,032 contributors for this article]
(2023).
Investigation of K+K- interactions via femtoscopy in Pb-Pb collisions at sNN =2.76 TeV at the CERN Large Hadron Collider.
Physical Review C.
ISSN 2469-9985.
107(5).
doi:
10.1103/PhysRevC.107.054904.
Full text in Research Archive
Show summary
Femtoscopic correlations of nonidentical charged kaons ( K + K − ) are studied in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision √ s N N = 2.76 TeV by ALICE at the CERN Large Hadron Collider. One-dimensional K + K − correlation functions are analyzed in three centrality classes and eight intervals of particle-pair transverse momentum. The Lednický and Luboshitz interaction model used in the K + K − analysis includes the final-state Coulomb interactions between kaons and the final-state interaction through a 0 ( 980 ) and f 0 ( 980 ) resonances. The mass of f 0 ( 980 ) and coupling were extracted from the fit to K + K − correlation functions using the femtoscopic technique. The measured mass and width of the f 0 ( 980 ) resonance are consistent with other published measurements. The height of the ϕ ( 1020 ) meson peak present in the K + K − correlation function rapidly decreases with increasing source radius, qualitatively in agreement with an inverse volume dependence. A phenomenological fit to this trend suggests that the ϕ ( 1020 ) meson yield is dominated by particles produced directly from the hadronization of the system. The small fraction subsequently produced by final-state interactions could not be precisely quantified with data presented in this paper and will be assessed in future work.
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,031 contributors for this article]
(2023).
Measurements of the groomed jet radius and momentum splitting fraction with the soft drop and dynamical grooming algorithms in pp collisions at √s = 5.02 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2023(5).
doi:
10.1007/JHEP05(2023)244.
Full text in Research Archive
Show summary
This article presents measurements of the groomed jet radius and momentum splitting fraction in pp collisions at s√ = 5.02 TeV with the ALICE detector at the Large Hadron Collider. Inclusive charged-particle jets are reconstructed at midrapidity using the anti-kT algorithm for transverse momentum 60<pchjetT<80 GeV/c. We report results using two different grooming algorithms: soft drop and, for the first time, dynamical grooming. For each grooming algorithm, a variety of grooming settings are used in order to explore the impact of collinear radiation on these jet substructure observables. These results are compared to perturbative calculations that include resummation of large logarithms at all orders in the strong coupling constant. We find good agreement of the theoretical predictions with the data for all grooming settings considered.
-
Acharya, S.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M.; Agrawal, N. & Ahammed, Z.
[Show all 1,045 contributors for this article]
(2023).
Anisotropic flow and flow fluctuations of identified hadrons in Pb–Pb collisions at √sNN = 5.02 TeV.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2023(5).
doi:
10.1007/JHEP05(2023)243.
Full text in Research Archive
Show summary
The first measurements of elliptic flow of π±, K±, p+p¯¯¯, K0S, Λ+Λ¯¯¯¯, ϕ, Ξ−+Ξ¯¯¯¯+, and Ω−+Ω¯¯¯¯+ using multiparticle cumulants in Pb–Pb collisions at sNN−−−√ = 5.02 TeV are resented. Results obtained with two- (v2{2}) and four-particle cumulants (v2{4}) are shown as a function of transverse momentum, pT, for various collision centrality intervals. Combining the data for both v2{2} and v2{4} also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark–gluon plasma. The characteristic features observed in previous pT-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low pT and the approximate scaling with the number of constituent quarks at intermediate pT, are similarly present in the four-particle correlations and the combinations of v2{2} and v2{4}. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide pT range.
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 944 contributors for this article]
(2023).
Measurement of ψ (2S) production as a function of charged-particle pseudorapidity density in pp collisions at √s = 13 TeV and p–Pb collisions at √sNN = 8.16 TeV with ALICE at the LHC.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2023(6).
doi:
10.1007/JHEP06(2023)147.
Full text in Research Archive
Show summary
Production of inclusive charmonia in pp collisions at center-of-mass energy of √ s = 13 TeV and p–Pb collisions at center-of-mass energy per nucleon pair of √ sNN = 8.16 TeV is studied as a function of charged-particle pseudorapidity density with ALICE. Ground and excited charmonium states (J/ψ, ψ(2S)) are measured from their dimuon decays in the interval of rapidity in the center-of-mass frame 2.5 < ycms < 4.0 for pp collisions, and 2.03 < ycms < 3.53 and −4.46 < ycms < −2.96 for p–Pb collisions. The charged-particle pseudorapidity density is measured around midrapidity (|η| < 1.0). In pp collisions, the measured charged-particle multiplicity extends to about six times the average value, while in p-Pb collisions at forward (backward) rapidity a multiplicity corresponding to about three (four) times the average is reached. The ψ(2S) yield increases with the charged-particle pseudorapidity density. The ratio of ψ(2S) over J/ψ yield does not show a significant multiplicity dependence in either colliding system, suggesting a similar behavior of J/ψ and ψ(2S) yields with respect to charged-particle pseudorapidity density. Results for the ψ(2S) yield and its ratio with respect to J/ψ agree with available model calculations.
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,040 contributors for this article]
(2023).
Inclusive photon production at forward rapidities in pp and p–Pb collisions at √sNN=5.02 TeV.
European Physical Journal C.
ISSN 1434-6044.
83(7).
doi:
10.1140/epjc/s10052-023-11729-y.
Full text in Research Archive
Show summary
A study of multiplicity and pseudorapidity distributions of inclusive photons measured in pp and p–Pb collisions at a center-of-mass energy per nucleon–nucleon collision of √sNN = 5.02 TeV using the ALICE detector in the forward pseudorapidity region 2.3 < ηlab < 3.9 is presented. Measurements in p–Pb collisions are reported for two beam configurations in which the directions of the proton and lead ion beam were reversed. The pseudorapidity distributions in p–Pb collisions are obtained for seven centrality classes which are defined based on different event activity estimators, i.e., the charged-particle multiplicity measured at midrapidity as well as the energy deposited in a calorimeter at beam rapidity. The inclusive photon multiplicity distributions for both pp and p–Pb collisions are described by double negative binomial distributions. The pseudorapidity distributions of inclusive photons are compared to those of charged particles at midrapidity in pp collisions and for different centrality classes in p–Pb collisions. The results are compared to predictions from various Monte Carlo event generators. None of the generators considered in this paper reproduces the inclusive photon multiplicity distributions in the reported multiplicity range. The pseudorapidity distributions are, however, better described by the same generators.
-
-
Acharya, S.; Adamová, D.; Adler, A.; Rinella, Rinella Aglieri; Agnello, M. & Agrawal, N.
[Show all 1,039 contributors for this article]
(2023).
Azimuthal correlations of heavy-flavor hadron decay electrons with charged particles in pp and p–Pb collisions at √sNN = 5.02 TeV.
European Physical Journal C.
ISSN 1434-6044.
83(8).
doi:
10.1140/epjc/s10052-023-11835-x.
Full text in Research Archive
Show summary
The azimuthal (ϕ) correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and p–Pb collisions at √sNN = 5.02 TeV. Results are reported for electrons with transverse momentum 4 < pT < 16 GeV/c and pseudorapidity |η| < 0.6. The associated charged particles are selected with transverse momentum 1 < pT < 7 GeV/c, and relative pseudorapidity separation with the leading electron |η| < 1. The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from p– Pb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The ϕ distribution and the peak observables in pp and p–Pb collisions are compared with calculations from various Monte Carlo event generators.
-
View all works in NVA
-
Solheim, Emilie Haugland
(2026).
Characterisation of a Forward Calorimeter prototype for the upgrade of the ALICE detector. A simulated performance study of different FoCal-E prototype configurations.
Universitetet i Oslo.
Full text in Research Archive
Show summary
During the next long shutdown of the Large Hadron Collider at CERN, ALICE will upgrade its detectors to improve its measurement capabilities before the next round of data collection. One key upgrade is the inclusion of a new high-granularity forward calorimeter (FoCal). This calorimeter will be installed in the forward region, an area not yet covered by current detectors, allowing for new studies and measurements in this important region of the experiment.
This thesis presents simulated performance studies of the electromagnetic part of FoCal (FoCal-E), looking at different prototype designs. The simulation of the original prototype design was characterised and validated against experimental data before other detector setups were tested to study how they affected the detector’s linearity and resolution, and to assess the placement of the high-granularity layers. The studies showed that the original prototype design meets its performance requirements and that the simulated results agreed with the experimental data within acceptable limits. Furthermore, no significant improvements were found in the alternative designs. Consequently, the original prototype design remains the preferred option.
View all works in NVA
Published
Aug. 25, 2021 2:38 PM
- Last modified
July 19, 2022 6:26 PM
