$B$-meson semileptonic decays with highly improved staggered quarks

TL;DR

This paper updates calculations of B-meson decay form factors using improved lattice QCD techniques, reducing uncertainties and enabling more precise tests of the Standard Model.

Contribution

It introduces a unified treatment of heavy and light quarks with the HISQ action, eliminating the need for perturbative matching in form factor calculations.

Findings

Use of highly improved staggered quarks (HISQ) for all quarks.

Lattice spacings down to 0.03 fm improve precision.

Form-factor results are preliminary and blinded.

Abstract

We present an update of the Fermilab Lattice and MILC Collaborations project to compute the form factors for semileptonic $B_{(s)}$-meson decays. Our calculation uses the highly improved staggered quark (HISQ) action for sea and valence quarks, and ensembles with up, down, strange, and charm quarks in the sea. Using a highly improved action with the MILC Collaboration's gauge ensembles with lattice spacings down to $a\approx0.03$ fm, allows the heavy valence quarks to be treated with the same discretization as the light and strange quarks. This unified treatment of the valence quarks allows for absolutely normalized vector currents, bypassing the need for perturbative matching, which has been a source of uncertainty in previous calculations of $B$-meson decay form factors by our collaboration. All preliminary form-factor results are blinded.