Precision Lattice Calculation of D and Ds decay constants

TL;DR

This paper reports a highly precise lattice QCD calculation of D and D_s meson decay constants, achieving about 2% error, improving accuracy over previous work, and enabling precise CKM matrix element determination.

Contribution

The study introduces a highly improved discretization method for charm quarks in lattice QCD, combined with extensive gauge configurations, to significantly enhance the precision of decay constant calculations.

Findings

Decay constants determined with about 2% error

Accurate continuum and chiral extrapolations performed

Results enable precise CKM element extraction

Abstract

We present a determination of the decay constants of the $D$ and $D_s$ mesons from lattice QCD, each with a total error of about 2%, approximately a factor of three better than previous calculations. We have been able to achieve this through the use of a highly improved discretization of QCD for charm quarks, coupled to gauge configurations generated by the MILC collaboration that include the full effect of sea u, d, and s quarks. We have results for a range of u/d masses down to m_s/5 and three values of the lattice spacing, which allow us to perform accurate continuum and chiral extrapolations. We fix the charm quark mass to give the experimental value of the \eta_c mass, and then a stringent test of our approach is the fact that we obtain correct (and accurate) values for the mass of the D and D_s mesons. We compare f_D and f_{D_s} with f_K and f_\pi, and using experiment determine corresponding CKM elements with good precision.