Observation of B$^0_s$ mesons and measurement of the B$^0_s$ / B$^+$ yield ratio in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV

TL;DR

This paper reports the first observation of B$_s^0$ mesons in PbPb collisions at 5.02 TeV and measures the B$_s^0$/B$^+$ yield ratio, providing insights into quark recombination in quark-gluon plasma.

Contribution

It presents the first detection of B$_s^0$ mesons in nucleus-nucleus collisions and measures their yield ratio to B$^+$, advancing understanding of heavy-flavor production in heavy-ion environments.

Findings

B$_s^0$ mesons observed with >5 sigma significance in PbPb collisions.

Measured B$_s^0$/B$^+$ yield ratio as a function of transverse momentum and centrality.

Results compared to theoretical models including quark recombination effects.

Abstract

The B$^0_s$ 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$^{-1}$. The mesons are reconstructed in the exclusive decay channels B$^0_s$ $\to$ J/$\psi(\mu^+\mu^-)\phi($K$^+$K$^-)$ and B$^+$ $\to$ J/$\psi(\mu^+\mu^-)$K$^+$, in the transverse momentum range 7-50 GeV/c and absolute rapidity 0-2.4. The B$^0_s$ 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$^0_s$ and B$^+$ is measured and compared to theoretical models that include quark recombination effects.