Studies of New Physics in $B^0_q-\bar{B}^0_q$ Mixing and Implications for Leptonic Decays

TL;DR

This paper examines $B^0_q$-$ar{B}^0_q$ mixing as a probe for new physics beyond the Standard Model, analyzing current data, tensions in CKM parameters, and future scenarios to refine leptonic decay predictions.

Contribution

It provides a comprehensive analysis of the impact of current and future data on constraining new physics through $B$ mixing and leptonic decays, highlighting the role of CKM parameter determinations.

Findings

Current data leaves room for new physics in $B_q$ mixing.

Tensions between inclusive and exclusive CKM determinations affect predictions.

Future precision measurements can significantly sharpen constraints on new physics.

Abstract

The phenomenon of $B^0_q$-$\bar{B}^0_q$ mixing ($q=d,s$) provides a sensitive probe for physics beyond the Standard Model. We have a careful look at the determination of the Unitarity Triangle apex, which is needed for the Standard Model predictions of the $B_q$ mixing parameters, and explore how much space for New Physics is left through the current data. We study the impact of tensions between inclusive and exclusive determinations of the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$, and focus on the $\gamma$ angle extraction. We present various future scenarios and discuss the application of these results for leptonic rare $B$ decays, which allows us to minimise the CKM parameter impact in the New Physics searches. Performing future projections, we explore and illustrate the impact of increased precision on key input quantities. It will be exciting to see how more precise data in the future high-precision era of flavour physics can lead to a much sharper picture.