ORCID Profile
0000-0002-6742-6677
Current Organisation
University of Zurich
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Physical Society (APS)
Date: 04-06-2020
Publisher: American Physical Society (APS)
Date: 14-08-2020
Publisher: Sissa Medialab
Date: 27-06-2019
DOI: 10.22323/1.352.0135
Publisher: Springer Science and Business Media LLC
Date: 10-2020
Abstract: A search for a chargino-neutralino pair decaying via the 125 GeV Higgs boson into photons is presented. The study is based on the data collected between 2015 and 2018 with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 fb − 1 of pp collisions at a centre-of-mass energy of 13 TeV. No significant excess over the expected background is observed. Upper limits at 95% confidence level for a massless $$ {\\tilde{\\chi}}_1^0 $$ χ ˜ 1 0 are set on several electroweakino production cross-sections and the visible cross-section for beyond the Standard Model processes. In the context of simplified supersymmetric models, 95% confidence-level limits of up to 310 GeV in $$ m\\left({\\tilde{\\chi}}_1^{\\pm }/{\\tilde{\\chi}}_2^0\\right) $$ m χ ˜ 1 ± / χ ˜ 2 0 , where $$ m\\left({\\tilde{\\chi}}_1^0\\right) $$ m χ ˜ 1 0 = 0 . 5 GeV, are set. Limits at 95% confidence level are also set on the $$ {\\tilde{\\chi}}_1^{\\pm }{\\tilde{\\chi}}_2^0 $$ χ ˜ 1 ± χ ˜ 2 0 cross-section in the mass plane of $$ m\\left({\\tilde{\\chi}}_1^{\\pm }/{\\tilde{\\chi}}_2^0\\right) $$ m χ ˜ 1 ± / χ ˜ 2 0 and $$ m\\left({\\tilde{\\chi}}_1^0\\right) $$ m χ ˜ 1 0 , and on scenarios with gravitino as the lightest supersymmetric particle. Upper limits at the 95% confidence-level are set on the higgsino production cross-section. Higgsino masses below 380 GeV are excluded for the case of the higgsino fully decaying into a Higgs boson and a gravitino.
Publisher: Springer Science and Business Media LLC
Date: 08-2020
DOI: 10.1140/EPJC/S10052-020-8050-3
Abstract: The results of a search for electroweakino pair production $$pp \\rightarrow \\tilde{\\chi }^\\pm _1 \\tilde{\\chi }^0_2$$ p p → χ ~ 1 ± χ ~ 2 0 in which the chargino ( $$\\tilde{\\chi }^\\pm _1$$ χ ~ 1 ± ) decays into a W boson and the lightest neutralino ( $$\\tilde{\\chi }^0_1$$ χ ~ 1 0 ), while the heavier neutralino ( $$\\tilde{\\chi }^0_2$$ χ ~ 2 0 ) decays into the Standard Model 125 GeV Higgs boson and a second $$\\tilde{\\chi }^0_1$$ χ ~ 1 0 are presented. The signal selection requires a pair of b -tagged jets consistent with those from a Higgs boson decay, and either an electron or a muon from the W boson decay, together with missing transverse momentum from the corresponding neutrino and the stable neutralinos. The analysis is based on data corresponding to 139 $$\\mathrm {fb}^{-1}$$ fb - 1 of $$\\sqrt{s}=13$$ s = 13 TeV pp collisions provided by the Large Hadron Collider and recorded by the ATLAS detector. No statistically significant evidence of an excess of events above the Standard Model expectation is found. Limits are set on the direct production of the electroweakinos in simplified models, assuming pure wino cross-sections. Masses of $$\\tilde{\\chi }^{\\pm }_{1}/\\tilde{\\chi }^{0}_{2}$$ χ ~ 1 ± / χ ~ 2 0 up to 740 GeV are excluded at 95% confidence level for a massless $$\\tilde{\\chi }^{0}_{1}$$ χ ~ 1 0 .
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: A search for Higgs boson pair production via vector-boson fusion (VBF) in the $$ b\\overline{b}b\\overline{b} $$ b b ¯ b b ¯ final state is carried out with the ATLAS experiment using 126 fb − 1 of proton- proton collision data delivered at $$ \\sqrt{s} $$ s = 13 TeV by the Large Hadron Collider. This search is sensitive to VBF production of additional heavy bosons that may decay into Higgs boson pairs, and in a non-resonant topology it can constrain the quartic coupling between the Higgs bosons and vector bosons. No significant excess relative to the Standard Model expectation is observed, and limits on the production cross-section are set at the 95% confidence level for a heavy scalar resonance in the context of an extended Higgs sector, and for non-resonant Higgs boson pair production. Interpretation in terms of the coupling between a Higgs boson pair and two vector bosons is also provided: coupling values normalised to the Standard Model expectation of κ 2 V − 0 . 76 and κ 2 V 2 . 90 are excluded at the 95% confidence level in data.
Publisher: Elsevier BV
Date: 2021
Publisher: Springer Science and Business Media LLC
Date: 08-2020
DOI: 10.1140/EPJC/S10052-020-8181-6
Abstract: A measurement of observables sensitive to spin correlations in $$t\\bar{t}$$ t t ¯ production is presented, using 36.1 $$\\hbox {fb}^{-1}$$ fb - 1 of pp collision data at $$\\sqrt{s} = 13$$ s = 13 TeV recorded with the ATLAS detector at the Large Hadron Collider. Differential cross-sections are measured in events with exactly one electron and one muon with opposite-sign electric charge as a function of the azimuthal opening angle and the absolute difference in pseudorapidity between the electron and muon candidates in the laboratory frame. The azimuthal opening angle is also measured as a function of the invariant mass of the $$t\\bar{t}$$ t t ¯ system. The measured differential cross-sections are compared to predictions by several NLO Monte Carlo generators and fixed-order calculations. The observed degree of spin correlation is somewhat higher than predicted by the generators used. The data are consistent with the prediction of one of the fixed-order calculations at NLO, but agree less well with higher-order predictions. Using these leptonic observables, a search is performed for pair production of supersymmetric top squarks decaying into Standard Model top quarks and light neutralinos. Top squark masses between 170 and 230 GeV are largely excluded at the 95% confidence level for kinematically allowed values of the neutralino mass.
Publisher: Springer Science and Business Media LLC
Date: 07-2020
DOI: 10.1140/EPJC/S10052-020-8001-Z
Abstract: This paper describes precision measurements of the transverse momentum $$p_\\mathrm {T}^{\\ell \\ell }$$ p T ℓ ℓ ( $$\\ell =e,\\mu $$ ℓ = e , μ ) and of the angular variable $$\\phi ^{*}_{\\eta }$$ ϕ η ∗ distributions of Drell–Yan lepton pairs in a mass range of 66–116 GeV. The analysis uses data from 36.1 fb $$^{-1}$$ - 1 of proton–proton collisions at a centre-of-mass energy of $$\\sqrt{s}=13\\,$$ s = 13 TeV collected by the ATLAS experiment at the LHC in 2015 and 2016. Measurements in electron-pair and muon-pair final states are performed in the same fiducial volumes, corrected for detector effects, and combined. Compared to previous measurements in proton–proton collisions at $$\\sqrt{s}=7$$ s = 7 and $$8\\,$$ 8 TeV, these new measurements probe perturbative QCD at a higher centre-of-mass energy with a different composition of initial states. They reach a precision of 0.2 $$\\%$$ % for the normalized spectra at low values of $$p_\\mathrm {T}^{\\ell \\ell }$$ p T ℓ ℓ . The data are compared with different QCD predictions, where it is found that predictions based on resummation approaches can describe the full spectrum within uncertainties.
Publisher: American Physical Society (APS)
Date: 13-08-2020
Publisher: American Physical Society (APS)
Date: 18-08-2023
Publisher: Springer Science and Business Media LLC
Date: 11-07-2022
DOI: 10.1140/EPJC/S10052-022-10472-0
Abstract: This paper presents studies of Bose–Einstein correlations (BEC) in proton–proton collisions at a centre-of-mass energy of 13 TeV, using data from the ATLAS detector at the CERN Large Hadron Collider. Data were collected in a special low-luminosity configuration with a minimum-bias trigger and a high-multiplicity track trigger, accumulating integrated luminosities of 151 $$\upmu $$ μ b $$^{-1}$$ - 1 and 8.4 nb $$^{-1}$$ - 1 , respectively. The BEC are measured for pairs of like-sign charged particles, each with $$|\eta | 2.5$$ | η | 2.5 , for two kinematic ranges: the first with particle $$p_{\mathrm {T}} 100$$ p T 100 MeV and the second with particle $$p_{\mathrm {T}} 500$$ p T 500 MeV. The BEC parameters, characterizing the source radius and particle correlation strength, are investigated as functions of charged-particle multiplicity (up to 300) and average transverse momentum of the pair (up to 1.5 GeV). The double-differential dependence on charged-particle multiplicity and average transverse momentum of the pair is also studied. The BEC radius is found to be independent of the charged-particle multiplicity for high charged-particle multiplicity (above 100), confirming a previous observation at lower energy. This saturation occurs independent of the transverse momentum of the pair.
Publisher: American Physical Society (APS)
Date: 26-07-2021
No related grants have been discovered for Steven Juhyung Lee.