Measurements of $SU(3)_f$ symmetry breaking in $B$ meson decay constants

TL;DR

This paper reports on lattice QCD calculations of $B$ meson decay constants, focusing on $SU(3)_f$ symmetry breaking effects, using improved actions and systematic averaging techniques to reduce uncertainties.

Contribution

It introduces an automated weighted averaging method over multiple fit ranges to improve the precision of $f_B$ and $f_{B_s}$ calculations and discusses systematic uncertainties in $SU(3)_f$ breaking measurements.

Findings

Quantified $SU(3)_f$ symmetry breaking in $B$ meson decay constants.

Developed an automated fitting range averaging technique.

Reduced systematic errors in decay constant calculations.

Abstract

We present updates from QCDSF/UKQCD/CSSM on the $SU(3)_f$ breaking in $B$ meson decay constants. The $b$-quarks are generated with an anisotropic clover-improved action, and are tuned to match properties of the physical $B$ and $B^*$ mesons. Configurations are generated with $\overline{m}=(1/3)(2m_l+m_s)$ kept constant to control symmetry breaking effects. Various sources of systematic uncertainty will be discussed, including those from continuum extrapolations and extrapolations to the physical point. We also present new efforts to calculate $f_B$ and $f_{B_s}$ using weighted averages across multiple time fitting regions. The use of an automated weighted averaging technique over multiple fitting ranges allows for timely tuning of the $b$-quark and reduces the impact of systematic errors from fitting range biases in calculations of $f_B$ and $f_{B_s}$