# Constraints and Implications on Higgs FCNC Couplings from Precision Measurement of $B_s \to \mu^+\mu^-$ Decay

## TL;DR

This paper analyzes how recent LHCb measurements of B_s to mu+ mu- decay constrain Higgs-mediated flavor-changing neutral currents, revealing tight bounds on such couplings and exploring implications for related rare decays and CP violation.

## Contribution

It provides the first comprehensive constraints on Higgs FCNC couplings using multiple experimental measurements and discusses the implications of the Cheng-Sher ansatz.

## Key findings

- Higgs FCNC couplings are severely constrained by current data.
- Allowed regions for rare decays like B_s to mu tau and h to sb are identified.
- Large CP violation is still possible in h to tau+ tau- decay.

## Abstract

We study constraints and implications of the recent LHCb measurement of ${\cal B}(B_s \to \mu^+\mu^-)$ for tree-level Higgs-mediated flavor-changing neutral current (FCNC) interactions. Combined with experimental data on $B_s$ mass difference $\Delta m_s$, the $h \to \mu \tau$, and the $h \to \tau^+\tau^-$ decay branching ratios from the LHC, we find that the Higgs FCNC couplings are severely constrained. The allowed regions for $B_s \to \mu \tau$, $\tau\tau$ and $h \to sb$ decays are obtained. Current data allow large CP violation in the $h \to \tau^+ \tau^-$ decay. Consequences of the Cheng-Sher ansatz for the Higgs Yukawa couplings are discussed in some detail.