Charmed and strange pseudoscalar meson decay constants from HISQ simulations

TL;DR

This paper updates the determination of decay constants and quark mass ratios for charmed and strange pseudoscalar mesons using HISQ simulations with near-physical light quark masses, employing multiple analysis methods to control errors.

Contribution

It introduces an alternative analysis using staggered chiral perturbation theory and a comprehensive error analysis for decay constants and quark mass ratios.

Findings

Updated decay constants for D+ and Ds mesons

Precise quark mass ratios with controlled systematic errors

Analysis methods that reduce chiral extrapolation uncertainties

Abstract

We update our determinations of $f_{D^+}$, $f_{D_s}$, $f_K$, and quark mass ratios from simulations with four flavors of HISQ dynamical quarks. The availability of ensembles with light quarks near their physical mass means that we can extract physical results with only small corrections for valence- and sea-quark mass mistunings instead of a chiral extrapolation. The adjusted valence-quark masses and lattice spacings may be determined from an ensemble-by-ensemble analysis, and the results for the quark mass ratios then extrapolated to the continuum limit. Our central values of the charmed meson decay constants, however, come from an alternative analysis, which uses staggered chiral perturbation theory for the heavy-light mesons, and allows us to incorporate data at unphysical quark masses where statistical errors are often smaller. A jackknife analysis propagated through all of these steps takes account of the correlations among all the quantities used in the analysis. Systematic errors from the finite spatial size and EM effects are estimated by varying the parameters in the analysis, and systematic errors from the assumptions in the continuum extrapolation are estimated from the spread of values from different extrapolations.