Precise measurement of the $f_s/f_d$ ratio of fragmentation fractions and of $B^0_s$ decay branching fractions

TL;DR

This paper precisely measures the ratio of $f_s/f_d$ fragmentation fractions and $B^0_s$ decay branching fractions at the LHCb experiment, improving accuracy and updating many decay measurements to aid new physics searches.

Contribution

It provides the first detailed measurement of $f_s/f_d$ as a function of transverse momentum and energy, and significantly reduces uncertainties in $B^0_s$ decay branching fractions.

Findings

The $f_s/f_d$ ratio varies linearly with transverse momentum.

Branching fractions of $B^0_s o J/ \u03a6$ and $B^0_s o D^-_s \u03c0^+$ are measured with halved uncertainties.

Updated $B^0_s$ decay branching fractions decrease systematic uncertainties in new physics searches.

Abstract

The ratio of the $B^0_s$ and $B^0$ fragmentation fractions, $f_s/f_d$, in proton-proton collisions at the LHC, is obtained as a function of $B$-meson transverse momentum and collision centre-of-mass energy from the combined analysis of different $B$-decay channels measured by the LHCb experiment. The results are described by a linear function of the meson transverse momentum, or with a function inspired by Tsallis statistics. Precise measurements of the branching fractions of the $B^0_s \to J/\psi \phi$ and $B^0_s \to D^-_s \pi^+$ decays are performed, reducing their uncertainty by about a factor of two with respect to previous world averages. Numerous $B^0_s$ decay branching fractions, measured at the LHCb experiment, are also updated using the new values of $f_s/f_d$ and branching fractions of normalisation channels. These results reduce a major source of systematic uncertainty in several searches for new physics performed through measurements of $B^0_s$ branching fractions.