Heavy-meson semileptonic decays for the Standard Model and beyond

TL;DR

This paper uses lattice QCD to calculate form factors for semileptonic B meson decays, providing essential inputs for testing the Standard Model and exploring new physics.

Contribution

It presents the first lattice QCD calculations of form factors for $B_s o K\,\ell\nu$ and $B\to K\ell\ell$ decays across multiple lattice spacings and quark masses, extending to the full kinematic range.

Findings

Form factors obtained at several lattice spacings and quark masses.

Chiral-continuum extrapolations performed up to 1.2 GeV.

Results extended to the entire kinematic range using the $z$ expansion.

Abstract

We calculate the form factors for the semileptonic decays $B_s\to K\ell\nu$ and $B\to K\ell\ell$ with lattice QCD. We work at several lattice spacings and a range of light quark masses, using the MILC 2+1-flavor asqtad ensembles. We use the Fermilab method for the $b$ quark. We obtain chiral-continuum extrapolations for $E_K$ up to $\sim1.2$ GeV and then extend to the entire kinematic range with the model-independent $z$ expansion.