ORCID Profile
0000-0002-1214-9262
Current Organisation
Institute of Nuclear Physics
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Publisher: Springer Science and Business Media LLC
Date: 06-2020
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: Single top-quark production in association with a Z boson, where the Z boson decays to a pair of charged leptons, is measured in the trilepton channel. The proton-proton collision data collected by the ATLAS experiment from 2015 to 2018 at a centre-of-mass energy of 13 TeV are used, corresponding to an integrated luminosity of 139 fb − 1 . Events containing three isolated charged leptons (electrons or muons) and two or three jets, one of which is identified as containing a b -hadron, are selected. The main backgrounds are from $$ t\\overline{t}Z $$ t t ¯ Z and diboson production. Neural networks are used to improve the background rejection and extract the signal. The measured cross-section for t ℓ + ℓ − q production, including non-resonant dilepton pairs with $$ {m}_{{\\mathrm{\\ell}}^{+}{\\mathrm{\\ell}}^{-}} $$ m ℓ + ℓ − 30 GeV, is 97 ± 13 (stat.) ± 7 (syst.) fb, consistent with the Standard Model prediction.
Publisher: American Physical Society (APS)
Date: 04-06-2020
Publisher: American Physical Society (APS)
Date: 05-08-2020
Publisher: American Physical Society (APS)
Date: 14-08-2020
Publisher: IOP Publishing
Date: 14-09-2020
Publisher: Springer Science and Business Media LLC
Date: 07-2020
Abstract: This paper presents a measurement of the production cross-section of a Z boson in association with b -jets, in proton-proton collisions at $$ \sqrt{s} $$ s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 35.6 fb − 1 . Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one or at least two b -jets with transverse momentum p T 20 GeV and rapidity |y| 2 . 5. Predictions from several Monte Carlo generators based on leading-order (LO) or next-to-leading-order (NLO) matrix elements interfaced with a parton-shower simulation and testing different flavour schemes for the choice of initial-state partons are compared with measured cross-sections. The 5-flavour number scheme predictions at NLO accuracy agree better with data than 4-flavour number scheme ones. The 4-flavour number scheme predictions underestimate data in events with at least one b-jet.
Publisher: American Physical Society (APS)
Date: 27-07-2020
Publisher: Springer Science and Business Media LLC
Date: 08-2020
Abstract: The factor of four increase in the LHC luminosity, from 0 . 5 × 10 34 cm − 2 s − 1 to 2 . 0 × 10 34 cm − 2 s − 1 , and the corresponding increase in pile-up collisions during the 2015–2018 data-taking period, presented a challenge for the ATLAS trigger, particularly for those algorithms that select events with missing transverse momentum. The output data rate at fixed threshold typically increases exponentially with the number of pile-up collisions, so the legacy algorithms from previous LHC data-taking periods had to be tuned and new approaches developed to maintain the high trigger efficiency achieved in earlier operations. A study of the trigger performance and comparisons with simulations show that these changes resulted in event selection efficiencies of 98% for this period, meeting and in some cases exceeding the performance of similar triggers in earlier run periods, while at the same time keeping the necessary bandwidth within acceptable limits.
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: 08-2020
Publisher: Elsevier BV
Date: 11-2020
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: 21-09-2020
Publisher: Springer Science and Business Media LLC
Date: 09-2020
Abstract: Inclusive and differential cross-sections for the production of top quarks in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 139 fb − 1 . The data were collected by the ATLAS detector at the LHC during Run 2 between 2015 and 2018 at a centre-of-mass energy of 13 TeV. The measurements are performed in a fiducial volume defined at parton level. Events with exactly one photon, one electron and one muon of opposite sign, and at least two jets, of which at least one is b -tagged, are selected. The fiducial cross-section is measured to be $$ {39.6}_{-2.3}^{+2.7} $$ 39.6 − 2.3 + 2.7 fb. Differential cross-sections as functions of several observables are compared with state-of-the-art Monte Carlo simulations and next-to-leading-order theoretical calculations. These include cross-sections as functions of photon kinematic variables, angular variables related to the photon and the leptons, and angular separations between the two leptons in the event. All measurements are in agreement with the predictions from the Standard Model.
Location: United Kingdom of Great Britain and Northern Ireland
Location: Poland
No related grants have been discovered for Janina Krzysiak.