Recombination of Bc mesons in ultrarelativistic heavy-ion collisions

High-energy heavy-ion collisions have been suggested as a favorable environment for the production of Bc mesons, due to a much larger abundance of charm and bottom quarks compared to elementary reactions. Motivated by recent CMS data for B+c production in Pb-Pb(5.02 TeV) collisions at the Large Hadron Collider (LHC), we deploy a previously developed transport approach for charmonia and bottomonia to evaluate the kinetics of Bc mesons throughout the fireball formed in these reactions. The main inputs to our approach are two transport parameters: the Bc's reaction rate and equilibrium limit. Both quantities are determined by previous calculations via a combination of charm and bottom sectors. In-medium binding energies of Bc mesons are calculated from a thermodynamic T matrix with a lattice-QCD constrained potential, and figure in their inelastic reaction rates. Temperature-dependent equilibrium limits include charm- and bottom-quark fugacities based on their initial production. We compute the centrality dependence of inclusive Bc production and transverse-momentum (pT) spectra using two different recombination models: instantaneous coalescence and resonance recombination. The main uncertainty in the resulting nuclear modification factors, RAA, is currently associated with the Bc cross section in elementary pp collisions, caused by the uncertainty in the branching ratio for the B-c -> J/psi mu-nu over bar decay. Our results indicate a large enhancement of the RAA at low pT, with significant regeneration contributions up to pT ⠃ 20 GeV. Comparisons to CMS data are carried out but firm conclusions will require a more accurate value of the branching ratio, or alternative channels to measure the Bc production in pp collisions.