Charmed and strange pseudoscalar meson decay constants from HISQ simulations

Understand

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.