# Semi-leptonic form factors for $B_s \to K \ell \nu$ and $B_s \to D_s \ell \nu$

## TL;DR

This paper discusses lattice QCD calculations of semi-leptonic $B_s$ decays to $K$ and $D_s$ mesons, aiming to improve the determination of CKM matrix elements and explore lepton flavor universality.

## Contribution

It provides new lattice QCD results for $B_s o K$ and $B_s o D_s$ form factors, aiding in precise CKM element extraction and testing lepton flavor universality.

## Key findings

- High-precision form factor calculations with controlled uncertainties
- Insights into CKM matrix element determinations
- Potential implications for lepton flavor universality tests

## Abstract

Semi-leptonic $B_s \to K \ell \nu$ and $B_s \to D_s \ell \nu$ decays provide an alternative $b$-decay channel to determine the CKM matrix elements $|V_{ub}|$ and $|V_{cb}|$ or to obtain $R$-ratios to investigate lepton flavor universality violations. In addition, these decays may shed further light on the discrepancies seen in the analysis of inclusive vs. exclusive decays. Using the nonperturbative methods of lattice QCD, theoretical results are obtained with good precision and full control over systematic uncertainties. This talk will highlight ongoing efforts of the $B$-physics program by the RBC-UKQCD collaboration.