Targeting (Pseudo)-Scalar CP Violation with $B_s \to \mu^+\mu^-$

TL;DR

This paper proposes a new method to detect CP-violating new physics in the rare decay $B_s o \mu^+\mu^-$ by analyzing specific observables, leveraging decay width differences and related decay channels.

Contribution

It introduces a novel strategy combining multiple observables to identify CP violation from (pseudo)-scalar new physics in $B_s o \mu^+\mu^-$ decays.

Findings

Identifies constrained regions in observable space for future experimental tests.

Demonstrates the sensitivity of the strategy to new physics contributions.

Provides a framework for future measurements to probe CP violation.

Abstract

The leptonic decay $B_s \to \mu^+\mu^-$ is both rare and theoretically clean, making it an excellent probe for New Physics searches. Due to its helicity suppression in the Standard Model, this decay is particularly sensitive to new (pseudo)-scalar contributions. We present a new strategy for detecting CP-violating New Physics contributions of this kind, exploiting two observables: $\mathcal{A}_{\Delta\Gamma_s}^{\mu\mu}$, which is accessible due to the sizeable decay width difference of the $B_s$ system, and the mixing-induced CP asymmetry $\mathcal{S}_{\mu\mu}$. The strategy also uses information from $B\to K^{(*)} \mu^+\mu^-$ and $B_s\to \phi \mu^+\mu^-$ decays. We find remarkably constrained regions in the $\mathcal{A}_{\Delta\Gamma_s}^{\mu\mu}$-$\mathcal{S}_{\mu\mu}$ plane that serve as promising targets for future measurements.