${\tau }_{B_s}/{\tau }_{B_d}$ and $\Delta {\Gamma }_s$ confront new physics in $b\to s\tau \tau$

Abstract

Several new physics scenarios that address anomalies in $B$-physics predict an enhancement of $b\to s\tau \tau$ with respect to its Standard Model prediction. Such scenarios necessarily imply modifications of the lifetime ratio ${\tau }_{B_s}/{\tau }_{B_d}$ and the lifetime difference $\Delta {\Gamma }_s$. In this work, we explore indirect bounds provided by these observables over new physics scenarios. We also estimate future projections, showing that future experimental and theoretical improvements on both ${\tau }_{B_s}/{\tau }_{B_d}$ and $\Delta {\Gamma }_s$ have the potential to provide bounds competitive with those directly extracted from $b\to s\tau \tau$ transitions. After performing a model-independent analysis, we apply our results to the particular case of leptoquark mediators proposed to address the $R_{D^{(\ast )}}$ anomalies.

Comments: 12 pages + Appendix, 4 Figures. v2: Minor discussions added, typos corrected, conclusions unchanged. Version accepted in EPJC