Results for light pseudoscalars from three-flavor simulations

TL;DR

This study calculates pseudoscalar meson properties using three-flavor lattice QCD, providing precise decay constants, quark mass ratios, and implications for CKM matrix element |V_{us}|, advancing understanding of light pseudoscalar physics.

Contribution

It presents the first detailed lattice QCD analysis of light pseudoscalar mesons with three dynamical flavors, including decay constants and quark mass ratios, using improved staggered quarks and chiral perturbation theory.

Findings

Decay constants: f_pi=129.5 MeV, f_K=156.6 MeV

Ratio f_K/f_pi=1.210(13)

Quark mass ratio m_u/m_d=0.43(8)

Abstract

We compute pseudoscalar meson masses and decay constants in partially quenched QCD with three dynamical flavors of improved staggered quarks. Fitting the lattice data to staggered chiral perturbation theory forms and extrapolating in quark mass and lattice spacing, we find: $f_\pi = 129.5 \pm 0.9 \pm 3.5$ MeV, $f_K = 156.6 \pm 1.0 \pm 3.6$ MeV, and $f_K/f_\pi = 1.210(4)(13)$. The value for $f_K/f_\pi$ implies $|V_{us}|=0.2219(26)$. We also obtain $m_u/m_d = 0.43(0)(1)(8)$, or, with more input on electromagnetic effects from the continuum, $m_u/m_d = 0.41(0)(1)(4)$. Using the one-loop perturbative mass renormalization, we determine $m_u$ and $m_d$ in the MSbar scheme.