# Extraction of the bare form factors for the semi-leptonic $B_s$ decays

## TL;DR

This paper presents a lattice QCD calculation of form factors for the semi-leptonic $B_s o K
u ar{
u}$ decay using Heavy Quark Effective Theory in the static approximation, achieving about 2% accuracy.

## Contribution

It introduces a method to extract bare form factors from lattice data using combined fits and ratios, with results consistent across methods and improved accuracy.

## Key findings

- Form factors extracted with approximately 2% accuracy.
- Methods for extracting matrix elements from lattice data are validated.
- Agreement among different extraction techniques is confirmed.

## Abstract

The computation of the form factors for the $B_s \to K \ell \nu$ decay is presented. The b quark is treated by means of Heavy Quark Effective Theory, currently in the static approximation. In these proceedings we discuss the extraction of the bare matrix elements from lattice data through a combined fit to two- and three-point correlation functions, as well as by considering suitable ratios. The different methods agree concerning the extracted form factors and approximately 2% accuracy is reached. The non-perturbative renormalization and matching to QCD is described in accompanying proceedings PoS(LATTICE2016)292.