$\Delta M_s$ theory precision confronts flavour anomalies

TL;DR

This paper refines Standard Model predictions for neutral B meson mass differences using recent theoretical calculations, analyzes their implications for new physics models addressing flavor anomalies, and discusses future prospects for reducing uncertainties.

Contribution

It provides updated SM predictions for B meson mass differences based on HQET sum rule and lattice calculations, and explores their impact on constraining new physics explanations of flavor anomalies.

Findings

Updated SM predictions for ΔM_s and ΔM_d with reduced uncertainties.

Derived upper bounds on Z' and S_3 lepto-quark masses from flavor anomaly explanations.

Discussed future improvements in theory precision and their implications.

Abstract

Based on recent HQET sum rule and lattice calculations we present updated Standard Model predictions for the mass differences of neutral $B$ mesons: $\Delta M_s^{\rm SM} = \left(18.4^{+0.7}_{-1.2} \right) \mbox{ps}^{-1}$ and $\Delta M_d^{\rm SM} = \left(0.533^{+0.022}_{-0.036} \right) \mbox{ps}^{-1}$ and study their impact on new physics models that address the present hints of anomalous data in $b \to s \ell \ell$ transitions. We also examine future prospects of further reducing the theory uncertainties and discuss the implications of a 2025 scenario with $\Delta M_s^\text{SM 2025} = \left(18.4 \pm 0.5\right) \mbox{ps}^{-1}$. In particular, the latter yields upper bounds $M_{Z'}\lesssim 9~\text{TeV}$ and $M_{S_3}\lesssim 30~\text{TeV}$ for the minimal $Z'$ and $S_3$ lepto-quark explanations of the $b \to s \ell \ell$ anomalies, respectively.