# Update on $f_B$

## TL;DR

This paper reports on the MILC collaboration's recent progress in computing decay constants of B and D mesons, including improved data, error estimates, and analysis methods across various lattice configurations.

## Contribution

It presents updated results on $f_B$, $f_{B_s}$, $f_D$, and $f_{D_s}$ with enhanced statistical analysis and systematic error estimation, advancing lattice QCD calculations.

## Key findings

- Improved statistical data at multiple lattice parameters.
- Systematic error estimates for chiral extrapolation.
- Enhanced analysis methods accounting for data correlations.

## Abstract

We describe the current status of the MILC collaboration computation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios. Progress over the past year includes: better statistics and plateaus at $\beta=6.52$ (quenched), $\beta=5.6$ ($N_F=2$) and $\beta=5.445$ ($N_F=2$), new runs with a wide range of dynamical quark masses at $\beta=5.5$ ($N_F=2$), an estimate of the systematic errors due to the chiral extrapolation, and an improved analysis which consistently takes into account both the correlations in the data at every stage and the systematic effects due to changing fitting ranges.