Quarkonium and Bc mesons from Pb + Pb at LHC energies

Abstract

The bb̄(Υ) mesons appear to be produced in the initial PbPb collision at 2.76 TeV per nucleon pair followed by partial melting in the hot quark-gluon plasma. In sharp contrast, the cc̄(J/Ψ) mesons seem more likely to be formed by recombination at the hadronization stage. The Bc mesons, with one quark of each kind are seldom seen in pp collisions because a particle-antiparticle pair requires the simultaneous production of four heavy quarks. Although a family of Bc mesons have been predicted, only the ground state has been seen. If the cc̄ mesons are produced by recombination, it could be expected that Bc mesons would be abundant with PbPb. Because the quark and antiquark have different flavor, the Bc are relatively long lived, 0.45 ps (to be compared with about 1.5 ps for the lighter B mesons). They would be seen with PbPb reactions by B±c → J/Ψ(μ+μ−)π± looking at muons and pions from displaced vertices.