| 421. |
- Aad, G, et al.
(author)
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Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in Pb+Pb Collisions at √sNN=5.02 TeV with the ATLAS Detector
- 2023
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In: Physical Review Letters. - 1079-7114. ; 131:17
-
Journal article (peer-reviewed)abstract
- This letter presents a measurement of the nuclear modification factor of large-radius jets in Formula Presented Formula Presented collisions by the ATLAS experiment. The measurement is performed using Formula Presented and Formula Presented of Formula Presented and Formula Presented data, respectively. The large-radius jets are reconstructed with the anti-Formula Presented algorithm using a radius parameter of Formula Presented, by reclustering anti-Formula Presented Formula Presented jets, and are measured over the transverse momentum (Formula Presented) kinematic range of Formula Presented and absolute pseudorapidity Formula Presented. The large-radius jet constituents are further reclustered using the Formula Presented algorithm in order to obtain the splitting parameters, Formula Presented and Formula Presented, which characterize the transverse momentum scale and angular separation for the hardest splitting in the jet, respectively. The nuclear modification factor, Formula Presented, obtained by comparing the Formula Presented jet yields to those in Formula Presented collisions, is measured as a function of jet transverse momentum (Formula Presented) and Formula Presented or Formula Presented. A significant difference in the quenching of large-radius jets having single subjet and those with more complex substructure is observed. Systematic comparison of jet suppression in terms of Formula Presented for different jet definitions is also provided. Presented results support the hypothesis that jets with hard internal splittings lose more energy through quenching and provide a new perspective for understanding the role of jet structure in jet suppression. © 2023 CERN, for the ATLAS Collaboration.
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| 422. |
- Aad, G., et al.
(author)
-
Measurement of t-channel single-top-quark production in pp collisions at s=5.02 TeV with the ATLAS detector
- 2024
-
In: Physics Letters B. - : Elsevier B.V.. - 0370-2693 .- 1873-2445. ; 854
-
Journal article (peer-reviewed)abstract
- The observation of the electroweak production of single-top-quarks is made using 255 pb−1 of proton-proton collision data recorded at s=5.02 TeV with the ATLAS detector at the Large Hadron Collider. An event selection is used to identify single-top-quark candidates arising from t-channel production with the top quark decaying semi-leptonically. Events passing the selection are then used to measure the inclusive cross-section for the combined production of single-top-quarks and antiquarks, σ(tq+t¯q), and the ratio Rt between these two. They are measured to be σ(tq+t¯q)=27.1−4.1+4.4(stat.)−3.7+4.4(syst.) pb and Rt=2.73−0.82+1.43(stat.)−0.29+1.01(syst.). The individual single-top-quark (tq) and single-top-antiquark (t¯q) production cross-sections are measured to be σ(tq)=19.8−3.1+3.9(stat.)−2.2+2.9(syst.) pb and σ(t¯q)=7.3−2.1+3.2(stat.)−1.5+2.8(syst.) pb. All measurements are in good agreement with the Standard Model predictions.
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| 423. |
- Aad, G, et al.
(author)
-
Measurement of the azimuthal anisotropy of charged-particle production in Xe+Xe collisions at sNN =5.44 TeV with the ATLAS detector
- 2020
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In: Physical Review C. - 2469-9985. ; 101:2
-
Journal article (peer-reviewed)abstract
- This paper describes the measurements of flow harmonics v2-v6 in 3μb-1 of Xe+Xe collisions at sNN=5.44 TeV performed using the ATLAS detector at the Large Hadron Collider (LHC). Measurements of the centrality, multiplicity, and pT dependence of the vn obtained using two-particle correlations and the scalar product technique are presented. The measurements are also performed using a template-fit procedure, which was developed to remove nonflow correlations in small collision systems. This nonflow removal is shown to have a significant influence on the measured vn at high pT, especially in peripheral events. Comparisons of the measured vn with measurements in Pb+Pb collisions and p+Pb collisions at sNN=5.02 TeV are also presented. The vn values in Xe+Xe collisions are observed to be larger than those in Pb+Pb collisions for n=2, 3, and 4 in the most central events. However, with decreasing centrality or increasing harmonic order n, the vn values in Xe+Xe collisions become smaller than those in Pb+Pb collisions. The vn in Xe+Xe and Pb+Pb collisions are also compared as a function of the mean number of participating nucleons, (Npart), and the measured charged-particle multiplicity in the detector. The v3 values in Xe+Xe and Pb+Pb collisions are observed to be similar at the same (Npart) or multiplicity, but the other harmonics are significantly different. The ratios of the measured vn in Xe+Xe and Pb+Pb collisions, as a function of centrality, are also compared to theoretical calculations.
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| 424. |
- Aad, G., et al.
(author)
-
Measurement of the B0s → ΌΌ effective lifetime with the ATLAS detector
- 2023
-
In: Journal of High Energy Physics (JHEP). - : Springer. - 1126-6708 .- 1029-8479. ; :9
-
Journal article (peer-reviewed)abstract
- This paper reports the first ATLAS measurement of the B-s(0) -> mu mu effective lifetime. The measurement is based on the data collected in 2015-2016, amounting to 26.3 fb(-1) of 13TeV LHC proton-proton collisions. The proper decay-time distribution of 58 +/- 13 background-subtracted signal candidates is fit with simulated signal templates parameterised as a function of the B-s(0) effective lifetime, with statistical uncertainties extracted through a Neyman construction. The resulting effective measurement of the B-s(0) -> mu mu lifetime is 0.99(-0.07)(+0.42) (stat.) +/- 0.17 (syst.) ps and it is found to be consistent with the Standard Model.
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| 425. |
- Aad, G., et al.
(author)
-
Measurement of the B0s → μμ effective lifetime with the ATLAS detector
- 2023
-
In: Journal of High Energy Physics (JHEP). - : Springer Nature. - 1126-6708 .- 1029-8479. ; 2023:9
-
Journal article (peer-reviewed)abstract
- This paper reports the first ATLAS measurement of the → μμ effective lifetime. The measurement is based on the data collected in 2015–2016, amounting to 26.3 fb−1 of 13 TeV LHC proton-proton collisions. The proper decay-time distribution of 58 ± 13 background-subtracted signal candidates is fit with simulated signal templates parameterised as a function of the effective lifetime, with statistical uncertainties extracted through a Neyman construction. The resulting effective measurement of the → μμ lifetime is (stat.) ± 0.17 (syst.) ps and it is found to be consistent with the Standard Model.
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| 426. |
- Aad, G., et al.
(author)
-
Measurement of the c-jet mistagging efficiency in t(t)over-bar events using pp collision data at root s=13 TeV collected with the ATLAS detector
- 2022
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In: European Physical Journal C. - : Springer. - 1434-6044 .- 1434-6052. ; 82:1
-
Journal article (peer-reviewed)abstract
- A technique is presented to measure the efficiency with which c-jets are mistagged as b-jets (mistagging efficiency) using t (t) over bar events, where one of theW bosons decays into an electron or muon and a neutrino and the other decays into a quark-antiquark pair. The measurement utilises the relatively large and known W -> cs branching ratio, which allows ameasurement to be made in an inclusive c-jet sample. The data sample used was collected by the ATLAS detector at root s = 13 TeV and corresponds to an integrated luminosity of 139 fb(-1). Events are reconstructed using a kinematic likelihood technique which selects the mapping between jets and t (t) over bar decay products that yields the highest likelihood value. The distribution of the b-tagging discriminant for jets from the hadronic W decays in data is compared with that in simulation to extract the mistagging efficiency as a function of jet transverse momentum. The total uncertainties are in the range 3-17%. The measurements generally agree with those in simulation but there are some differences in the region corresponding to the most stringent b-jet tagging requirement.
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| 427. |
- Aad, G., et al.
(author)
-
Measurement of the Centrality Dependence of the Dijet Yield in Formula Presented Collisions at Formula Presented with the ATLAS Detector
- 2024
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 132:10
-
Journal article (peer-reviewed)abstract
- ATLAS measured the centrality dependence of the dijet yield using Formula Presented of Formula Presented data collected at Formula Presented in 2016. The event centrality, which reflects the Formula Presented impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, Formula Presented, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The Formula Presented shows a scaling with the Bjorken Formula Presented of the parton originating from the proton, Formula Presented, while no such trend is observed as a function of Formula Presented. This analysis provides unique input to understanding the role of small proton spatial configurations in Formula Presented collisions by covering parton momentum fractions from the valence region down to Formula Presented and Formula Presented. © 2024 CERN, for the ATLAS Collaboration.
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| 428. |
- Aad, G., et al.
(author)
-
Measurement of the Centrality Dependence of the Dijet Yield in p+Pb Collisions at √sNN=8.16 TeV with the ATLAS Detector
- 2024
-
In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 132:10
-
Journal article (peer-reviewed)abstract
- ATLAS measured the centrality dependence of the dijet yield using 165 nb−1 of p+Pb data collected at √sNN=8.16 TeV in 2016. The event centrality, which reflects the p+Pb impact parameter, is characterized by the total transverse energy registered in the Pb-going side of the forward calorimeter. The central-to-peripheral ratio of the scaled dijet yields, RCP, is evaluated, and the results are presented as a function of variables that reflect the kinematics of the initial hard parton scattering process. The RCP shows a scaling with the Bjorken x of the parton originating from the proton, xp, while no such trend is observed as a function of xPb. This analysis provides unique input to understanding the role of small proton spatial configurations in p+Pb collisions by covering parton momentum fractions from the valence region down to xp∼10−3 and xPb∼4×10−4.
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| 429. |
- Aad, G, et al.
(author)
-
Measurement of the charge asymmetry in highly boosted top-quark pair production in √s=8 TeV pp collision data collected by the ATLAS experiment
- 2016
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In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 756, s. 52-71
-
Journal article (peer-reviewed)abstract
- In the pp→tt¯ process the angular distributions of top and anti-top quarks are expected to present a subtle difference, which could be enhanced by processes not included in the Standard Model. This Letter presents a measurement of the charge asymmetry in events where the top-quark pair is produced with a large invariant mass. The analysis is performed on 20.3 fb−1 of pp collision data at s=8TeV collected by the ATLAS experiment at the LHC, using reconstruction techniques specifically designed for the decay topology of highly boosted top quarks. The charge asymmetry in a fiducial region with large invariant mass of the top-quark pair (mtt¯>0.75 TeV) and an absolute rapidity difference of the top and anti-top quark candidates within −2<|yt|−|yt¯|<2 is measured to be 4.2±3.2%, in agreement with the Standard Model prediction at next-to-leading order. A differential measurement in three tt¯ mass bins is also presented. © 2016 CERN for the benefit of the ATLAS Collaboration
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| 430. |
- Aad, G., et al.
(author)
-
Measurement of the charge asymmetry in top-quark pair production in association with a photon with the ATLAS experiment
- 2023
-
In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 843
-
Journal article (peer-reviewed)abstract
- A measurement of the charge asymmetry in top-quark pair (tt¯) production in association with a photon is presented. The measurement is performed in the single-lepton tt¯ decay channel using proton–proton collision data collected with the ATLAS detector at the Large Hadron Collider at CERN at a centre-of-mass-energy of 13 TeV during the years 2015–2018, corresponding to an integrated luminosity of 139 fb−1. The charge asymmetry is obtained from the distribution of the difference of the absolute rapidities of the top quark and antiquark using a profile likelihood unfolding approach. It is measured to be AC=−0.003±0.029 in agreement with the Standard Model expectation. © 2023 The Author(s)
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