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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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.
Full text in Research Archive
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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
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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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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,916 contributors for this article]
(2025).
Observation of double parton scattering in same-sign W boson pair production in pp collisions at s=13 TeV with the ATLAS detector.
Physics Letters B.
ISSN 0370-2693.
870.
doi:
10.1016/j.physletb.2025.139892.
Full text in Research Archive
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This letter reports the measurement of double parton scattering in same-sign W boson pair production with the ATLAS detector. The data set used corresponds to an integrated luminosity of 140 fb−1 of proton–proton collisions at a center-of-mass energy of 13 TeV, collected during Run 2 of the Large Hadron Collider. The study is performed in final states including two same-charge leptons, electron or muon, missing transverse momentum, and up to one jet. An excess of events is observed over the expected background contributions with a significance of 8.8 standard deviations. The measured fiducial cross section times leptonic branching fraction is 4.59 ± 0.64 fb. The measurement corresponds to a double parton scattering effective cross section of 10.6 ± 1.8 mb.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 51 contributors for this article]
(2025).
Search for light neutral particles decaying promptly into collimated pairs of electrons or muons in pp collisions at √s = 13 Te V with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
doi:
10.1140/epjc/s10052-025-13916-5.
Full text in Research Archive
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A search for a dark photon, a new light neutral particle, which decays promptly into collimated pairs of electrons or muons is presented. The search targets dark photons resulting from the exotic decay of the Standard Model Higgs boson, assuming its production via the dominant gluon-gluon fusion mode. The analysis is based on 140 fb - 1 of data collected with the ATLAS detector at the Large Hadron Collider from proton-proton collisions at a center-of-mass energy of 13 Te V . Events with collimated pairs of electrons or muons are analysed and background contributions are estimated using data-driven techniques. No significant excess in the data above the Standard Model background is observed. Upper limits are set at 95% confidence level on the branching ratio of the Higgs boson decay into dark photons between 0.001% and 5%, depending on the assumed dark photon mass and signal model.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 50 contributors for this article]
(2025).
Measurement of the Lund jet plane in hadronic decays of top quarks and W bosons with the ATLAS detector.
European Physical Journal C.
ISSN 1434-6044.
85.
doi:
10.1140/epjc/s10052-025-13924-5.
Full text in Research Archive
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The Lund jet plane (LJP) is measured for the first time in t t ¯ events, using 140 fb - 1 of s = 13 TeV pp collision data collected with the ATLAS detector at the LHC. The LJP is a two-dimensional observable of the sub-structure of hadronic jets that acts as a proxy for the kinematics of parton showers and hadron formation. The observable is constructed from charged particles and is measured for R = 1.0 anti- k t jets with transverse momentum above 350 GeV containing the full decay products of either a top quark or a daughter W boson. The other top quark in the event is identified from its decay into a b-quark, an electron or a muon and a neutrino. The measurement is corrected for detector effects and compared with a range of Monte Carlo predictions sensitive to different aspects of the hadronic decays of the heavy particles. In the W-boson-initiated jets, all the predictions are incompatible with the measurement. In the top quark initiated jets, disagreement with all predictions is observed in smaller subregions of the plane, and with a subset of the predictions across the fiducial plane. The measurement could be used to improve the tuning of Monte Carlo generators, for better modelling of hadronic decays of heavy quarks and bosons, or to improve the performance of jet taggers.
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Aad, G.; Aakvaag, Erlend; Abbott, B.; Abdelhameed, S.; Abeling, K. & Abicht, N. J.
[Show all 2,923 contributors for this article]
(2025).
Search for displaced leptons in √s=13 TeV and 13.6 TeV pp collisions with the ATLAS detector.
Physical Review D.
ISSN 2470-0010.
112.
doi:
10.1103/w8hh-xf24.
Full text in Research Archive
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A search for leptons displaced from the primary vertex is performed with the ATLAS detector at the Large Hadron Collider. The search includes the full proton-proton collision dataset collected during Run 2 at √𝑠 =13 TeV and a partial dataset collected during Run 3 in 2022–2023 at √𝑠 =13.6 TeV, corresponding to integrated luminosities of 140 fb−1 and 56.3 fb−1, respectively. Final states with displaced electrons or muons are considered, and novel triggers introduced in Run 3 are employed that use large impact parameter tracking to reconstruct displaced tracks with low momentum. In addition, photon reconstruction and multivariate techniques are employed to broaden the sensitivity to channels with large background rates or highly displaced electrons, respectively. The results are consistent with the Standard Model background expectations and are used to set model-independent limits on the production of displaced electrons and muons. The analysis is also interpreted in the context of a gauge-mediated supersymmetry breaking model with pair-produced long-lived sleptons and a dark sector model with pair-produced chargino-like states. The results include 95% confidence level exclusions of selectrons with lifetimes from 4 ps to 60 ns and a mass of 150 GeV, and exclusions of selectrons, smuons, and staus with a lifetime of 0.3 ns for masses up to 740, 830, and 440 GeV, respectively. Dark charginos with masses up to 380 GeV are excluded for a mass difference with the neutral state of 40 GeV, and mass differences down to 17 GeV are excluded for dark charginos with a 100 GeV mass.
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View all works in NVA
Published
Nov. 4, 2010 12:16 PM
- Last modified
Nov. 4, 2025 10:50 AM
