Extracting $B_s\to D_s^*\ell\nu_\ell$ form factors

TL;DR

This paper demonstrates how to extract form factors for the semileptonic decay $B_s o D_s^* u ar{ u}$ using lattice QCD data, aiding in CKM matrix and lepton universality tests.

Contribution

It provides a detailed analysis method to determine the four form factors from existing lattice data for $B_s o D_s^* u ar{ u}$ decays, utilizing the narrow width approximation.

Findings

Successfully extracted four form factors from lattice data.

Used RBC/UKQCD's 2+1 flavor gauge ensembles with multiple lattice spacings.

Analyzed decays with pion masses between 268 and 433 MeV.

Abstract

Semileptonic $B_{(s)}$ decays are of great phenomenological interest because they allow to determine e.g. CKM matrix elements or test lepton flavor universality. Taking advantage of already existing lattice data, we demonstrate the analysis steps to extract the four form factors describing exclusive semileptonic $B_s\to D_s^*\ell\nu_\ell$ decays using the narrow width approximation. Our data are based on RBC/UKQCD's set of 2+1 flavor gauge field ensembles with Shamir domain-wall fermion and Iwasaki gauge field action featuring inverse lattice spacings of $a^{-1}=$1.785, 2.383, and 2.785 GeV as well as pion masses between 268 and 433 MeV. Light, strange and charm quarks are simulated using domain-wall fermions, whereas bottom quarks are generated with the relativistic heavy quark (RHQ) action.