Lepton Flavour Violation and B_s Leptonic Final States at the LHC

TL;DR

This paper reviews ATLAS and CMS studies on B_s leptonic decays to constrain lepton flavour violation, discussing measurement strategies, current status, and expected sensitivities for rare decay processes at the LHC.

Contribution

It provides a comprehensive overview of experimental approaches and projected sensitivities for detecting lepton flavour violation via B_s decays at the LHC.

Findings

Expected 3-sigma evidence for B_s -> mu^+ mu^- in low-luminosity LHC.

CMS sensitivity to tau -> 3mu decay around 10^-8 branching ratio.

Feasibility analysis of measuring rare B_s and tau decays at ATLAS and CMS.

Abstract

An overview of ATLAS and CMS studies of B_s leptonic decays providing constraints on the lepton flavour violation phenomenon is presented. Except direct lepton flavour violating final states B_s -> l_1^+ l_2^-, constraints can also be set by a measurement of B_s -> mu^+ mu^- decay, whose branching ratio in some theoretical models correlates with a branching ratio of B_s -> l_1^+ l_2^-, tau -> 3mu and some other lepton flavour violating decays. In this paper, the feasibility of measurements of B_s -> mu^+ mu^- decay is described, including the present status, the trigger and the offline analysis strategies and the expected reach in the branching ratio measurement. The ATLAS and CMS experiments foresee to provide 3-sigma evidence of Standard Model B_s -> mu^+ mu^- branching ratio by the end of LHC low-luminosity stage (30 fb^(-1)). Also a CMS study of the tau -> 3mu decay and an initial particle-level based study of the B_s -> tau mu decay are presented. A sensitivity of ~10^(-8) for the tau -> 3mu branching ratio measurement is predicted by CMS.