Measurement of the top quark pair production cross section in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV

Abstract

The inclusive cross section for top quark pair ($\mathrm{t}\bar{\mathrm{t}}$) production in lead-lead (PbPb) collisions is reported for the first time at a center-of-mass energy per nucleon pair of 5.36 TeV. The analysis uses data corresponding to an integrated luminosity of 1.58 nb${}^{-1}$ collected by the CMS experiment at the CERN LHC in 2023. The $\mathrm{t}\bar{\mathrm{t}}$ production cross section, ${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$ = 3.42 ${}_{-0.51}^{+0.54}$ (stat) ${}_{-0.43}^{+0.50}$ (syst) $\mu$b, is measured in dilepton final states using a fit to a multivariate discriminator that combines the decay electron and muon kinematic properties with the multiplicity of bottom quark jets. The result is consistent with perturbative quantum chromodynamics calculations at next-to-next-to-leading order (NNLO) accuracy employing several nuclear parton distribution functions. In addition, the Drell$-$Yan production cross section (${\sigma }_{\text{DY}}$) for dilepton masses above 10 GeV and the ratio of $\mathrm{t}\bar{\mathrm{t}}$ to DY cross sections ($R_{\mathrm{t}\bar{\mathrm{t}}/\mathrm{DY}}$) are found to be compatible with the NNLO predictions. The observables ${\sigma }_{\mathrm{t}\bar{\mathrm{t}}}$, ${\sigma }_{\text{DY}}$, and $R_{\mathrm{t}\bar{\mathrm{t}}/\mathrm{DY}}$ are measured separately for central and semicentral PbPb collisions to investigate for the first time the dependence of top quark production on the collision impact parameter.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-24-021 (CMS Public Pages)