Evidence for non-analytic light quark mass dependence in the baryon spectrum

TL;DR

This study provides the first direct lattice QCD evidence of non-analytic light quark mass effects, specifically chiral logarithms, in the baryon spectrum, challenging the convergence of SU(3) chiral perturbation theory.

Contribution

It offers the first direct lattice QCD evidence of chiral logarithms in the baryon spectrum and examines the limitations of SU(3) chiral perturbation theory.

Findings

Evidence of non-analytic light quark mass dependence in baryon masses

Consistency of baryon-pion axial couplings with QCD values

Inconsistency of the Gell-Mann--Okubo relation with a simple Taylor expansion

Abstract

Using precise lattice QCD computations of the baryon spectrum, we present the first direct evidence for the presence of contributions to the baryon masses which are non-analytic in the light quark masses; contributions which are often denoted "chiral logarithms". We isolate the poor convergence of SU(3) baryon chiral perturbation theory to the flavor-singlet mass combination. The flavor-octet baryon mass splittings, which are corrected by chiral logarithms at next to leading order in SU(3) chiral perturbation theory, yield baryon-pion axial coupling constants D, F, C and H consistent with QCD values; the first evidence of chiral logarithms in the baryon spectrum. The Gell-Mann--Okubo relation, a flavor-27 baryon mass splitting, which is dominated by chiral corrections from light quark masses, provides further evidence for the presence of non-analytic light quark mass dependence in the baryon spectrum; we simultaneously find the GMO relation to be inconsistent with the first few terms in a taylor expansion in m_s - m_l, which must be valid for small values of this SU(3) breaking parameter. Additional, more definitive tests of SU(3) chiral perturbation theory will become possible with future, more precise, lattice calculations.