Sigma-term physics in the perturbative chiral quark model

Abstract

We apply the perturbative chiral quark model at one loop to analyze meson-baryon sigma terms. Analytic expressions for these quantities are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our result for the $\ensuremath{\pi}N$ sigma term ${\ensuremath{\sigma}}_{\ensuremath{\pi}N}\ensuremath{\approx}45 \mathrm{MeV}$ is in good agreement with the value deduced by Gasser, Leutwyler, and Sainio using dispersion-relation techniques and exploiting the chiral symmetry constraints.