SU(2) and SU(3) chiral perturbation theory analyses on meson and baryon masses in 2+1 flavor lattice QCD

TL;DR

This study analyzes meson and baryon masses from 2+1 flavor lattice QCD using SU(2) and SU(3) chiral perturbation theories, revealing convergence issues at physical strange quark mass and identifying the valid range for baryon mass expansion.

Contribution

It provides a detailed comparison of SU(2) and SU(3) chiral expansions in lattice QCD and assesses their convergence for meson and baryon masses.

Findings

SU(3) expansion is not convergent at NLO for physical strange quark mass.

Chiral behavior of nucleon mass is well described up to m_pi^2 ~ 0.2 GeV^2.

Results include determination of low energy constants.

Abstract

We investigate the quark mass dependence of meson and baryon masses obtained from 2+1 flavor dynamical quark simulations performed by the PACS-CS Collaboration. With the use of SU(2) and SU(3) chiral perturbation theories up to NLO, we examine the chiral behavior of the pseudoscalar meson masses and the decay constants in terms of the degenerate up-down quark mass ranging form 3 MeV to 24 MeV and two choices of the strange quark mass around the physical value. We discuss the convergence of the SU(2) and SU(3) chiral expansions and present the results for the low energy constants. We find that the SU(3) expansion is not convergent at NLO for the physical strange quark mass. The chiral behavior of the nucleon mass is also discussed based on the SU(2) heavy baryon chiral perturbation theory up to NNLO. Our results show that the expansion is well behaved only up to m_pi^2 ~ 0.2 GeV^2.