Karlsruhe 2024 – scientific programme
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T: Fachverband Teilchenphysik
T 50: Top physics 2 (top pair cross section)
T 50.1: Talk
Tuesday, March 5, 2024, 16:00–16:15, Geb. 30.95: Audimax
Observation of top-quark pair production in proton-lead collisions in the ATLAS experiment at the LHC — Petr Baroň1, Iwona Grabowska-Bołd2, Jiří Kvita1, Santu Mondal3, •Patrycja Potepa1,4, and Yuriy Volkotrub5 — 1Palacký University Olomouc, Czech Republic — 2AGH University of Krakow, Poland — 3Czech Technical University in Prague, Czech Republic — 4Johannes Gutenberg University Mainz, Germany — 5Jagiellonian University, Kraków, Poland
Top quarks, the heaviest elementary particles carrying colour charges, are considered to be promising probes of the quark-gluon plasma produced in heavy-ion collisions at LHC energies. In proton-lead collisions, top-quark production is expected to be sensitive to nuclear modifications of parton distribution functions at high Bjorken-x values, which is a region poorly constrained by other available probes. In 2016, the ATLAS experiment collected proton-lead collisions at centre-of-mass energy of 8.16 TeV per nucleon pair, corresponding to a total integrated luminosity of 165 nb−1. In this talk, we present the first measurement of the top-quark pair production cross section in dilepton and lepton+jet channels with the ATLAS experiment. The significance of the measured signal in both decay modes exceeds 5 standard deviations, resulting in the first observation of top-quark pair production in the dilepton channel in proton-lead collisions. The total relative uncertainty amounts to 9%, which makes it the most precise top-quark pair cross-section measurement in heavy-ion collisions at the LHC.
Keywords: top quark; heavy-ion collisions; ATLAS experiment