B- and D-meson semileptonic decays with highly improved staggered quarks

TL;DR

This paper reports on lattice QCD calculations of B- and D-meson semileptonic decays using highly improved staggered quarks, achieving more precise results by reducing uncertainties related to current normalization and perturbative matching.

Contribution

It introduces a unified treatment of heavy and light quarks with the HISQ action, enabling more accurate form-factor calculations without perturbative matching.

Findings

Use of HISQ action for all quark flavors improves accuracy.

Inclusion of physical-mass ensembles reduces extrapolation uncertainties.

Preliminary form-factor results are blinded for unbiased analysis.

Abstract

We present results for $B_{(s)}$- and $D_{(s)}$-meson semileptonic decays from ongoing calculations by the Fermilab Lattice and MILC Collaborations. Our calculation employs the highly improved staggered quark (HISQ) action for both sea and valence quarks and includes several ensembles with physical-mass up, down, strange, and charm quarks and lattice spacings ranging from $a\approx0.15$ fm down to 0.06 fm. At most lattice spacings, an ensemble with physical-mass light quarks is included. The use of the highly improved action, combined with the MILC Collaboration's gauge ensembles with lattice spacings down to $a\approx0.042$ fm, allows heavy valence quarks to be treated with the same discretization as the light and strange quarks. This unified treatment of the valence quarks allows (in some cases) for absolutely normalized currents, bypassing the need for perturbative matching, which has been a leading source of uncertainty in previous calculations of $B$-meson decay form factors by our collaboration. All preliminary form-factor results are blinded.