Academic Interests
Analysis of data from the ATLAS experiment at CERN. Mostly concerned with beyond Standard Model searches and in particular Supersymmetry.
Higher education and employment history
Bachelordegree from the program Fysikk, astronomi og meteorologi, UiO
Masterdegree at the group of Experimental Particle Physics, UiO
PhD from University of Oslo, 2013 Supersymmetry in Di-Lepton Final States with the ATLAS Detector at √s = 7 TeV
Education
FYS3150 - Computational Phyics
FYS4411 - Computational Physics II Ouantum mechanical systems
Spring 2020: FYS5555 - Research-Based Particle Physics
Tags:
Particle physics,
LHC,
ATLAS,
Higgs boson,
Supersymmetry,
Neutrinos
Publications
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,932 contributors for this article]
(2026).
Search for signatures of electroweakinos with photons, jets, and large missing transverse momentum in √s=13 TeV pp collisions with the ATLAS detector.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2026(4).
doi:
10.1007/JHEP04(2026)150.
Full text in Research Archive
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A search for final states characterised by at least one isolated high transversemomentum photon, jets and large missing transverse momentum is presented. Such a final
state might occur in gauge-mediated supersymmetric models where a pair of binos and higgsinos mix to form neutralinos, one of which decays into a photon plus a gravitino while
the other decays into a Higgs boson, a Z boson or a photon, plus a gravitino. The search is performed using the full Run-2 data sample of 140 fb−1 of √s = 13TeV proton-proton
collisions collected by the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed above the Standard Model prediction and model-dependent
exclusion limits at the 95% confidence level are set. These limits are interpreted in terms of the masses of gauginos, which are excluded up to 1.2TeV depending on their branching
ratios, and on their branching ratios as a function of their mass.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,934 contributors for this article]
(2026).
Measurement of the top-quark mass using decays with a J/ψ meson at √s=13 TeV with the ATLAS detector.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2026(4).
doi:
10.1007/JHEP04(2026)099.
Full text in Research Archive
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The top-quark mass is measured using top-quark decays producing an isolated lepton and J/ψ meson reconstructed in its μ+μ− decay mode. The data sample was recorded
with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of √s = 13TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of
140 fb−1. The measurement is based on the invariant mass m(ℓμ+μ−) of the system made of the isolated lepton ℓ from the W boson decay and the non-isolated μ+μ− pair from a J/ψ
decay of a b-hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximumlikelihood fit to the m(ℓμ+μ−) distribution is performed to extract the top-quark mass. The
top-quark mass is measured to be mtop = 172.17±0.80 (stat)±0.81 (syst)±1.07 (recoil) GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole
parton shower gluon-recoil scheme used in top-quark decays.
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Zwalinski, L.; Zormpa, O.; Zorbas, T. G.; Zografos, A.; Zoch, K. & Zoccoli, A.
[Show all 2,915 contributors for this article]
(2026).
Electroweak diboson production in association with a high-mass dijet system in semileptonic final states from pp collisions at √s=13 TeV with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
86(4).
doi:
10.1140/epjc/s10052-025-15217-3.
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This paper reports the observation of electroweak diboson (WW/WZ/ZZ) production in association with a high-mass dijet system, in which final states with one boson decaying leptonically and the other boson decaying hadronically are studied. The hadronically decaying W/Z boson is reconstructed as either two small-radius jets or one large-radius
jet with jet substructure requirements. The data analyzed correspond to an integrated luminosity of 140 fb−1 of proton–proton collisions at a center-of-mass energy of
√s = 13 TeV collected with the ATLAS detector during the 2015-2018 data taking at the Large Hadron Collider. The electroweak production of WW/WZ/ZZ in association
with two jets is observed in a phase space dominated by vector-boson scattering with a significance of 7.4σ (expected 6.1σ) and the signal strength is determined to be 1.28+0.23
−0.21. The corresponding production cross section in a fiducial phase space is measured in addition. The signal strengths of both electroweak and QCD associated diboson productions are furthermore measured in a two-dimensional fit, the result of which agrees with the Standard Model prediction. The data are interpreted in the context of a dimension-8 effective field theory to probe anomalous quartic gauge couplings resulting in the first set of exclusion limits on the Wilson coefficients in the semileptonic channel reported by the ATLAS Collaboration. The observed limits for the S02, T0 and M0 operators are (−3.96 < fS02/4 < 3.96) TeV−4, (−0.25 < fT 0/4 < 0.22) TeV−4, (−1.26 < fM0/4 < 1.25) TeV−4.
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Zwalinski, L.; Zormpa, O.; Zorbas, T. G.; Zografos, A.; Zoch, K. & Zoccoli, A.
[Show all 2,928 contributors for this article]
(2026).
Measurement of the W-boson angular coefficients and transverse momentum in pp collisions at √s=13 TeV with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
86(5).
doi:
10.1140/epjc/s10052-025-15264-w.
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The angular distributions of Drell–Yan lepton pairs provide sensitive probes of the underlying dynamics of quantum chromodynamics (QCD) effects in vector-boson production. This paper presents for the first time the measurement of the full set of angular coefficients together with the differential cross-section as a function of the transverse
momentum of the W boson, in the full phase space of the decay leptons. The measurements are performed separately for the W− and W+ channels. The analysis uses proton–
proton collision data recorded by the ATLAS experiment at the Large Hadron Collider in 2017 and 2018, during special low-luminosity runs with a reduced number of interactions
per bunch crossings (pile-up). The data correspond to an integrated luminosity of 338 pb−1 at a centre-of-mass energy of √s = 13 TeV. The low pile-up environment provides
excellent experimental conditions for high-precision measurements ofW-boson production. All results agree with theoretical predictions incorporating finite-order QCD corrections
up to order α2S.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,850 contributors for this article]
(2026).
Search for long-lived charginos and τ-sleptons using final states with a disappearing track in pp collisions at √s=13 TeV with the ATLAS detector.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2026(7).
doi:
10.1007/JHEP07(2026)152.
Full text in Research Archive
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This paper reports a search for decays of long-lived charginos or τ-sleptons to final states containing a short disappearing track, a single high-energy jet, and missing transverse momentum. The search uses 137 fb−1 of data from 13 TeV proton–proton collisions recorded by the ATLAS detector during Run 2 of the LHC. Multiple search regions are defined, all requiring the presence of a track reconstructed from either three or four measurements in the innermost layers of the ATLAS detector. Regions with tracks having only three measurements are further characterised by the absence or presence of a low-energy charged pion reconstructed using a dedicated algorithm, leveraging machine learning. Data-driven methods are used to estimate the background contributions in the search regions. No significant excesses are found and 95% CL lower limits are placed on the masses of charginos and τ-sleptons in the lifetime range 0.01–10 ns. Observed (expected) mass limits of up to 225 GeV (250 GeV) are set for pure-higgsino charginos in scenarios with lifetimes below 0.03 ns, where the electroweakino mass splitting is entirely due to loop corrections involving the Standard Model bosons, and up to 720 GeV (840 GeV) for charginos with a lifetime of around 1 ns. For wino production, charginos with masses up to 880 GeV (1020 GeV) are excluded for lifetimes of around 1 ns. For τ-sleptons with lifetimes of around 1 ns, masses are excluded up to 320 GeV (390 GeV) in Constrained Minimal Supersymmetric Standard Model scenarios and 300 GeV (380 GeV) in Gauge-Mediated Supersymmetry-Breaking scenarios.
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Zwalinski, L.; Zorbas, T. G.; Zografos, A.; Zoch, K.; Zoccoli, A. & Živković, L.
[Show all 2,855 contributors for this article]
(2026).
Breaking barriers: the impact of ATLAS Virtual Visits in science communication.
The European Physical Journal Plus.
141(7).
doi:
10.1140/epjp/s13360-026-07771-w.
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The ATLAS Collaboration at CERN’s Large Hadron Collider is at the forefront of particle physics research and is equally committed to bridging the gap between cutting-edge science and the wider public. Since 2010, the ATLAS Virtual Visits programme has provided live, interactive tours of the ATLAS detector and control room to global audiences in their language, without the need to travel. The programme has grown significantly since its inception, as demonstrated by quantitative data collected since January 2019 and case studies of large-scale implementations in Brazil and Greece. The impact on individual participants is also discussed.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,928 contributors for this article]
(2026).
Measurement of the azimuthal anisotropy of charged particles in √sNN = 5.36 TeV<sup>16</sup>O+<sup>16</sup>O and<sup>20</sup>Ne+<sup>20</sup>Ne collisions with the ATLAS detector.
Physical Review C.
ISSN 2469-9985.
113(4).
doi:
10.1103/XQXZ-8BHF.
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Zwalinski, L.; Zou, W.; Zormpa, O.; Zorbas, T. G.; Zoch, K. & Zoccoli, A.
[Show all 2,918 contributors for this article]
(2025).
Measurement of W±-boson differential cross-sections in proton–proton collisions with low pile-up data at √s=5.02 TeV and 13TeV with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
85(7).
doi:
10.1140/epjc/s10052-025-14178-x.
Full text in Research Archive
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High precision single-differential W ±-boson pro- duction cross-sections as a function of electron or muon transverse momentum pT or their pseudorapity η, as well as double-differential cross-sections as functions of these vari- ables, are measured in proton–proton collisions at centre-of- mass energies √s = 5.02 TeV and 13 TeV. The W -boson charge asymmetry as a function of lepton η is also measured. The data, collected in dedicated runs at reduced instantaneous luminosity with the ATLAS detector at the Large Hadron Collider, correspond to integrated luminosities of 255 pb−1 at 5.02 TeV and 338 pb−1 at 13 TeV. The measurements are in agreement with Standard-Model predictions calculated at next-to-next-to-leading-order in the strong coupling constant αs including transverse-momentum resummation at next-to- next-to-leading logarithmic accuracy using several parton distribution functions. The impact of the measured differen- tial cross-sections as a function of lepton η on the determina- tion of these functions is studied using a profiling technique.
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Ciangottini, D.; Forti, A. C.; Heinrich, L.; Skidmore, N.; Alpigiani, C. & Aly, M.
[Show all 66 contributors for this article]
(2025).
Analysis Facilities for the HL-LHC White Paper.
Computing and Software for Big Science.
ISSN 2510-2036.
9(1).
doi:
10.1007/s41781-025-00133-8.
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This white paper presents the current status of the R&D for Analysis Facilities (AFs) and attempts to summarize the views on the future direction of these facilities. These views have been collected through the High Energy Physics (HEP) Software Foundation’s (HSF) Analysis Facilities forum (HSF Analysis Facilities Forum), established in March 2022, the Analysis Ecosystems II workshop (Analysis Ecosystems Workshop II), that took place in May 2022, and the WLCG/HSF pre-CHEP workshop (WLCG–HSF pre-CHEP Workshop), that took place in May 2023. The paper attempts to cover all the aspects of an analysis facility.
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Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H. & Aboulhorma, A.
[Show all 2,924 contributors for this article]
(2025).
Measurements of W+W−production cross-sections in pp collisions at s=13 TeV with the ATLAS detector.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(8).
doi:
10.1007/JHEP08(2025)142.
Full text in Research Archive
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Measurements of W+W− → e±νμ∓ν production cross-sections are presented, providing a test of the predictions of perturbative quantum chromodynamics and the electroweak theory. The measurements are based on data from pp collisions at √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider in 2015–2018, corresponding to an integrated luminosity of 140 fb−1. The number of events due to top-quark pair production, the largest background, is reduced by rejecting events containing jets with b-hadron decays. An improved methodology for estimating the remaining top-quark background enables a precise measurement of W+W− cross-sections with no additional requirements on jets. The fiducial W+W− cross-section is determined in a maximum-likelihood fit with an uncertainty of 3.1%. The measurement is extrapolated to the full phase space, resulting in a total W+W− cross-section of 127 ± 4 pb. Differential cross-sections are measured as a function of twelve observables that comprehensively describe the kinematics of W+W− events. The measurements are compared with state-of-the-art theory calculations and excellent agreement with predictions is observed. A charge asymmetry in the lepton rapidity is observed as a function of the dilepton invariant mass, in agreement with the Standard Model expectation. A CP-odd observable is measured to be consistent with no CP violation. Limits on Standard Model effective field theory Wilson coefficients in the Warsaw basis are obtained from the differential cross-sections.
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Aad, G.; Abbott, B.; Abeling, K.; Abicht, N. J.; Abidi, S. H. & Aboulhorma, A.
[Show all 2,877 contributors for this article]
(2025).
Search for diphoton resonances in the 66 to 110 GeV mass range using pp collisions at (Formula presented.) TeV with the ATLAS detector.
Journal of High Energy Physics (JHEP).
ISSN 1126-6708.
2025(1).
doi:
10.1007/JHEP01(2025)053.
Full text in Research Archive
Show summary
A search is performed for light, spin-0 bosons decaying into two photons in the 66 to 110 GeV mass range, using 140 fb−1 of proton-proton collisions at √s = 13 TeV produced by the Large Hadron Collider and collected by the ATLAS detector. Multivariate analysis techniques are used to define event categories that improve the sensitivity to new resonances beyond the Standard Model. A model-independent search for a generic spin-0 particle and a model-dependent search for an additional low-mass Higgs boson are performed in the diphoton invariant mass spectrum. No significant excess is observed in either search. Mass-dependent upper limits at the 95% confidence level are set in the model-independent scenario on the fiducial cross-section times branching ratio into two photons in the range of 8 fb to 53 fb. Similarly, in the model-dependent scenario upper limits are set on the total cross-section times branching ratio into two photons as a function of the Higgs boson mass in the range of 19 fb to 102 fb.
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Zwalinski, L.; Zou, W.; Zormpa, O.; Zorbas, T. G.; Zoch, K. & Zoccoli, A.
[Show all 2,903 contributors for this article]
(2025).
Total Cost of Ownership and Evaluation of Google Cloud Resources for the ATLAS Experiment at the LHC.
Computing and Software for Big Science.
ISSN 2510-2036.
9(1).
doi:
10.1007/s41781-024-00128-x.
Full text in Research Archive
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The ATLAS Google Project was established as part of an ongoing evaluation of the use of commercial clouds by the ATLAS Collaboration, in anticipation of the potential future adoption of such resources by WLCG grid sites to fulfil or complement their computing pledges. Seamless integration of Google cloud resources into the worldwide ATLAS distributed computing infrastructure was achieved at large scale and for an extended period of time, and hence cloud resources are shown to be an effective mechanism to provide additional, flexible computing capacity to ATLAS. For the first time a total cost of ownership analysis has been performed, to identify the dominant cost drivers and explore effective mechanisms for cost control. Network usage significantly impacts the costs of certain ATLAS workflows, underscoring the importance of implementing such mechanisms. Resource bursting has been successfully demonstrated, whilst exposing the true cost of this type of activity. A follow-up to the project is underway to investigate methods for improving the integration of cloud resources in data-intensive distributed computing environments and reducing costs related to network connectivity, which represents the primary expense when extensively utilising cloud resources.
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Zwalinski, L.; Zormpa, O.; Zorbas, T. G.; Zografos, A.; Zoch, K. & Zoccoli, A.
[Show all 2,854 contributors for this article]
(2026).
Publisher Correction: Calibration of the jet energy scale and resolution of small-radius jets using semileptonic tt¯ events with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
86(10).
doi:
10.1140/epjc/s10052-026-16348-x.
Full text in Research Archive
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In the originally published article, several typographical and formatting errors were identified. In the PDF version, on page 10 (bottom left), the terms “POWHEGinterfaced” and
“POWHEGsettings” should read “POWHEGinterfaced” and “POWHEG settings”, respectively. In the online version, instances of “T{eV}” and “G{eV}” throughout the text should
read “TeV” and “GeV”, respectively. The publisher regrets these errors and any inconvenience they may have caused.
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Published
Nov. 4, 2010 12:16 PM
- Last modified
Nov. 4, 2025 10:50 AM
