Enhanced production of ${\Lambda }_b^0$ baryons in high-multiplicity $pp$ collisions at $\sqrt{s}=13$ TeV

Abstract

The production rate of ${\Lambda }_b^0$ baryons relative to $B^0$ mesons in $pp$ collisions at a center-of-mass energy $\sqrt{s}=13$ TeV is measured by the LHCb experiment. The ratio of ${\Lambda }_b^0$ to $B^0$ 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 $\sim 2$ with increasing multiplicity. At relatively low transverse momentum, the ratio of ${\Lambda }_b^0$ to $B^0$ 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.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2023-027.html (LHCb public pages)

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