$f_B$ quenched and unquenched

TL;DR

This paper presents lattice QCD calculations of decay constants for B and D mesons, comparing quenched and unquenched results to estimate the effects of quenching on these quantities.

Contribution

It provides new high-statistics lattice results for decay constants at multiple beta values and offers a preliminary estimate of quenching errors by comparing quenched and dynamical quark configurations.

Findings

Quenched results at various beta values allow continuum extrapolation.

Dynamical quark effects cause significant deviations from quenched results.

Preliminary estimate of quenching error in decay constants.

Abstract

Results for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$, and their ratios are presented. High statistics quenched runs at $\beta=5.7$, $5.85$, $6.0$, and $6.3$, plus a run still in progress at $\beta=6.52$ make possible a preliminary extrapolation to the continuum. The data allows good control of all systematic errors except for quenching, although not all of the error estimates have been finalized. Results from configurations which include effects of dynamical quarks show a significant deviation from the quenched results and make possible a crude estimate of the quenching error.