Evidence for modification of $b$ quark hadronization in high-multiplicity $pp$ collisions at $\sqrt{s} = 13$ TeV

TL;DR

This study provides evidence that the hadronization process of $b$ quarks in high-multiplicity proton-proton collisions at 13 TeV may be modified, with increased production of $B_s^0$ mesons relative to $B^0$, suggesting medium effects.

Contribution

It presents the first evidence of multiplicity-dependent modification in $b$ quark hadronization in high-energy $pp$ collisions, indicating possible medium effects on hadronization mechanisms.

Findings

Increased $B_s^0$ to $B^0$ ratio at low transverse momentum with higher multiplicity.

No significant ratio change at transverse momenta above 6 GeV/$c$.

Supports the role of quark coalescence in high-multiplicity environments.

Abstract

The production rate of $B^{0}_{s}$ mesons relative to $B^{0}$ mesons is measured by the LHCb experiment in $pp$ collisions at a center-of-mass energy $\sqrt{s} = 13$ 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$\sigma$ level is found for an increase of the ratio of $B^{0}_{s}$ to $B^{0}$ 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.