Enhanced production of Λ°b baryons in high-multiplicity pp collisions at √s = 13 TeV

Abstract

[Abstract] The production rate of Λ°b baryons relative to B° mesons in pp collisions at a center-of-mass energy √s = 13 TeV is measured by the LHCb experiment. The ratio of Λ°b to B° production cross-sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity. At low multiplicity, the ratio measured at LHCb is consistent with the value measured in e+ e− collisions and increases by a factor of ∼ 2 with increasing multiplicity. At relatively low transverse momentum, the ratio of Λ°b to B° cross-sections is higher than what is measured in e+ e− collisions, but converges with the e+ e− ratio as the momentum increases. These results imply that the evolution of heavy b quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision. Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.