The inclusive cross section for top quark pair (tt) 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 tt production cross section, σₓₓ = 3. 42^+0. 54-₀. ₅₁ (stat) ^+0. 50-₀. ₄₃ (syst) μb, 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 (σDY) for dilepton masses above 10 GeV and the ratio of tt to DY cross sections (Rₓₓ/₃ₘ) are found to be compatible with the NNLO predictions. The observables σₓₓ, σDY, and Rₓₓ/₃ₘ 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.
Belyaev et al. (Thu,) studied this question.