Evidence for Modification of b Quark Hadronization in High-Multiplicity pp Collisions at √s = 13 TeV

The production rate of B0s mesons relative to B0 mesons is measured by the LHCb experiment in pp collisions at a center-of-mass energy √s = 13 TeV over the forward rapidity interval 2 < y < 4.5 as a function of the charged particle multiplicity measured in the event. Evidence at the 3.4 σ level is found for an increase of the ratio of B0s to B0 cross sections with multiplicity at transverse momenta below 6 GeV/c, with no significant multiplicity dependence at higher transverse momentum. Comparison with data from e+ e− collisions implies that the density of the hadronic medium may affect the production rates of B mesons. This is qualitatively consistent with the emergence of quark coalescence as an additional hadronization mechanism in high-multiplicity collisions.