Observation of top-quark pair production in proton-lead collisions in ATLAS


Dear colleagues,

we would like to invite you to the seminar of Division of Elementary Particle Physics of Institute of Physics, presented by Petr Baroň.

For more info, please see invitation.



Top-quarks and Higgs boson are the only elementary particles that have not been observed in heavy-ion collisions in the ATLAS detector yet. In particular top quarks, the heaviest elementary particles carrying colour charges, have been argued to be attractive candidates for probing the quark-gluon plasma produced in heavy-ion collisions. In proton-lead collisions, top-quark production is expected to be sensitive to nuclear modifications of parton distribution functions (PDF) at high Bjoerken-x values which are hard to access experimentally using other probes available so far. In 2016 the ATLAS experiment collected proton-lead collisions at centre-of-mass energy of 8.16 TeV per nucleon pair. The data sample corresponds to an integrated luminosity of 165 nb-1, which allows for the first time in this data set with ATLAS, to measure top-quark pair production. In this work, we discuss the inclusive cross section measurement for the top-quark pairs production in dilepton and lepton+jets decay modes with electrons and muons recorded by the ATLAS experiment. The measurement is compared to the NNLO predictions for top-quark production using various PDF sets.