Branching Ratio Measurements of $B_s$ Decays

TL;DR

This paper discusses the challenges in accurately measuring $B_s$ decay branching ratios due to mixing effects and proposes using effective lifetime measurements from untagged data to correct for systematic biases.

Contribution

It introduces a method to correct $B_s$ branching ratio measurements using effective lifetime data derived from untagged samples, addressing systematic biases.

Findings

Effective $B_s$ lifetime can correct decay branching ratio biases.

Systematic biases in untagged data can reach 10%.

Recommendations for experimental procedures at hadron colliders.

Abstract

We have just entered an era of precision measurements for $B_s$-decay observables. A characteristic feature of the $B_s$-meson system is $B^0_s$--$\bar B^0_s$ mixing, which exhibits a sizable decay width difference. The latter feature leads to a subtle complication for the extraction of branching ratios of $B_s$ decays from untagged data samples, leading to systematic biases as large as O(10%) that depend on the dynamics of the considered decay. We point out that this effect can only be corrected for using information from a time-dependent analysis and suggest the use of the effective $B_s$ decay lifetime, which can already be extracted from the untagged data sample, for this purpose. We also address several experimental issues that can play a role in the extraction of effective lifetimes at a hadron collider, and advocate the use of the $B_s$ branching ratios, as presented in this note, for consistent comparisons of theoretical calculations and experimental measurements in particle listings.