Measurement of $f_s / f_u$ variation with proton-proton collision energy and $B$-meson kinematics

TL;DR

This study measures how the ratio of $f_s/f_u$ varies with collision energy and B-meson kinematics, revealing a significant dependence on transverse momentum and an increase with collision energy.

Contribution

It provides the first detailed measurement of $f_s/f_u$ dependence on collision energy and B-meson kinematics across multiple energies at the LHC.

Findings

$f_s/f_u$ depends on B-meson transverse momentum with 6.0$\sigma$ significance.

Evidence for $f_s/f_u$ increasing with collision energy at 4.8$\sigma$.

Results vary across different collision energies, with the strongest effects at 13 TeV.

Abstract

The ratio of the $\mathrm{B}^0_\mathrm{s}$ and $\mathrm{B}^+$ fragmentation fractions $f_\mathrm{s}$ and $f_u$ is studied with $B^0_\mathrm{s}\to\mathrm{J}/\psi \phi $ and $B^+\to\mathrm{J}/\psi K^+$ decays using data collected by the LHCb experiment in proton-proton collisions at 7, 8 and 13$\text{ TeV}$ center-of-mass energies. The analysis is performed in bins of $\mathrm{B}$-meson momentum, longitudinal momentum, transverse momentum, pseudorapidity and rapidity. The fragmentation-fraction ratio $f_\mathrm{s} / f_u$ is observed to depend on the $\mathrm{B}$-meson transverse momentum with a significance of $6.0\,\sigma$. This dependency is driven by the 13$\text{ TeV}$ sample ($8.7\,\sigma$) while the results for the other collision energies are not significant when considered separately. Furthermore the results show a $4.8\,\sigma$ evidence for an increase of $f_\mathrm{s} / f_u$ as a function of collision energy.