$B \to \pi$, $B_{(s)} \to D_{(s)}$ from 2+1+1 Flavor Lattice QCD

TL;DR

This paper reports a lattice-QCD calculation of form factors for B-meson semileptonic decays using 2+1+1 flavor ensembles, aiming for high-precision CKM matrix element determinations.

Contribution

It provides a detailed lattice-QCD computation of B-meson decay form factors at physical quark masses with improved techniques, advancing precision in flavor physics.

Findings

Preliminary chiral-continuum fit results for scalar and vector form factors.

Use of highly improved staggered quark action on multiple lattice spacings.

Direct computation at physical b-quark mass on finest ensembles.

Abstract

We present a lattice-QCD calculation of the hadronic form factors for $B$-meson semileptonic decays computed using the highly improved staggered quark action for both valence and sea quarks on the MILC collaborations 2+1+1-flavor ensembles with lattice spacing ranging from 0.09 fm to 0.03 fm, many with physical pion masses On our finest ensembles, we compute the form factors directly at the physical $b$-quark mass. We discuss the computational setup and analysis strategies for two- and three-point correlation functions. For $B_{(s)} \to D_{(s)}$ we present preliminary results of chiral-continuum fits for the scalar and vector form factors. The goal of this project is a percent-level determination of the scalar and vector form factors to enable high-precision determinations of $|V_{ub}|$ and $|V_{cb}|$. This work fits into a broader program of lattice-QCD studies of weak $B$-meson decays by the Fermilab Lattice and MILC Collaborations.