Probing New Physics with $B^0_s\to \mu^+\mu^-$: Status and Perspectives

TL;DR

This paper discusses how the decay $B^0_s o \mu^+\mu^-$ can be used to test the Standard Model and explore New Physics, highlighting the impact of decay width differences and proposing new observables for future experiments.

Contribution

It introduces the effect of decay width difference $\Delta\Gamma_s$ on the $B^0_s o \\mu^+\\mu^-$ decay analysis and proposes new observables like the effective lifetime and CP asymmetry for probing New Physics.

Findings

The Standard Model branching ratio must be increased by about 10% due to $\\Delta\\Gamma_s$ effects.

The effective $B^0_s o \\mu^+\\mu^-$ lifetime provides a new probe for New Physics.

Correlations between observables and branching ratios are model-dependent.

Abstract

The rare decay $B^0_s \to \mu^+\mu^-$ plays a key role for the testing of the Standard Model. It is pointed out that the sizable decay width difference $\Delta\Gamma_s$ of the $B_s$-meson system affects this channel in a subtle way. As a consequence, its calculated Standard Model branching ratio has to be upscaled by about 10%. Moreover, the sizable $\Delta\Gamma_s$ makes a new observable through the effective $B^0_s\to \mu^+\mu^-$ lifetime accessible, which probes New Physics in a way complementary to the branching ratio and adds an exciting new topic to the agenda for the high-luminosity upgrade of the LHC. Further probes of New Physics are offered by a CP-violating rate asymmetry. Correlations between these observables and the $B^0_s \to \mu^+\mu^-$ branching ratio are illustrated for specific models of New Physics.