Dortmund 2021 – scientific programme

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T: Fachverband Teilchenphysik

T 28: Top quark production II

T 28.3: Talk

Tuesday, March 16, 2021, 16:30–16:45, Tc

Measurement of the tt production cross-section in the lepton+jets channel at √s=13 TeV with the ATLAS experiment — •Baida Achkar¹, Tomas Dado^1,2, Jacopo Magro³, Kevin Moor¹, Clara Nellist^1,4, Marcel Niemeyer¹, Arnulf Quadt¹, Leonid Serkin⁵, and Elizaveta Shabalina¹ — ¹II. Physikalisches Institut, Georg-August-Universität Göttingen — ²now at: Technische-Universität Dortmund — ³Università di Udine/INFN — ⁴now at: Radboud University Nijmegen/Nikhef — ⁵ICTP Trieste/INFN

Studies of top-quark production and decays provide a precise probe of the Standard Model (SM) as well as its extensions. At the CERN Large Hadron Collider, top quarks are primarily produced in quark–antiquark pairs (tt) and form an important background in many searches for physics beyond the SM. This talk reports ATLAS measurements of the tt cross-sections in the full phase space (inclusive) and in a phase space close to the experimental measurement range (fiducial) at √s = 13 TeV, using the full pp data set collected during 2015–2018 which corresponds to an integrated luminosity of L=139 fb⁻¹. Events with exactly one charged lepton and four or more jets in the final state, with at least one jet containing b-hadrons are used to measure the tt cross-section through a profile-likelihood fit to data of the distributions of discriminating variables in three non-overlapping regions. The tt fiducial cross-section is measured with a precision of 4.3% to be: σ_fid = 110.7± 4.8 pb. The inclusive cross-section is measured with a precision of 4.6% to be: σ_inc = 830± 38 pb. Results agree with the theoretical calculations at NNLO in QCD.