Observation of Bs⁰ mesons and measurement of the Bs⁰/B⁺ yield ratio in PbPb collisions at [Formula presented] TeV

The B and B production yields are measured in PbPb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV. The data sample, collected with the CMS detector at the LHC, corresponds to an integrated luminosity of 1.7 nb. The mesons are reconstructed in the exclusive decay channels B->s0J/?(??)?(KK) and B->+J/?(??)K, in the transverse momentum range 7-50 GeV/c and absolute rapidity 0-2.4. The B meson is observed with a statistical significance in excess of five standard deviations for the first time in nucleus-nucleus collisions. The measurements are performed as functions of the transverse momentum of the B mesons and of the PbPb collision centrality. The ratio of production yields of B and B is measured and compared to theoretical models that include quark recombination effects.