Heavy-light meson decay constants and hyperfine splittings with the heavy-HISQ method

TL;DR

This paper calculates decay constants and hyperfine splittings for heavy-light mesons using the HISQ method, covering a range of heavy quark masses and including physical sea quark effects.

Contribution

It introduces a comprehensive lattice QCD study of heavy-light meson properties using the HISQ approach with physical sea quarks and a range of heavy quark masses, including near the bottom quark.

Findings

Ratios of decay constants and hyperfine splittings are computed across heavy quark masses.

Results include physical point extrapolations for $D_{(s)}^{(*)}$ and $B_{(s)}^{(*)}$ mesons.

Heavy-quark mass dependence of decay constants and splittings is mapped out.

Abstract

We compute ratios between the vector and pseudoscalar, and tensor and vector decay constants, and between hyperfine splittings for $D_{(s)}^{(*)}$ and $B_{(s)}^{(*)}$ mesons. We use the Highly Improved Staggered Quark (HISQ) action for all valence quarks, paired with the second generation MILC $n_f = 2+1+1$ HISQ gluon field configurations. These include light sea quarks with $m_u = m_d \equiv m_l$ going down to the physical values, as well as physically tuned strange and charm sea quarks. We also use a HISQ valence heavy quark, with mass ranging from that of the $c$-quark up to very nearly that of the physical $b$-quark on the finest lattices, allowing us to map out the heavy-quark mass dependence of the decay constant and hyperfine splitting ratios.