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

Abstract

The ratio of the ${\mathrm{B}}_{\mathrm{s}}^0$ and ${\mathrm{B}}^{+}$ fragmentation fractions $f_{\mathrm{s}}$ and $f_u$ is studied with $B_{\mathrm{s}}^0\to \mathrm{J}/\psi \varphi$ 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.

All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2019-020.html (LHCb public pages)

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