Evidence for nonanalytic light quark mass dependence in the baryon spectrum

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 nonanalytic in the light quark masses, contributions which are often denoted chiral logarithms. It is demonstrated that the SU(3) flavor-singlet mass combination suffers the most severe convergence issues. 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 nonanalytic light quark mass dependence in the baryon spectrum; we simultaneously find the Gell-Mann-Okubo 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.