QCD sum rules vs. chiral perturbation theory

Abstract

QCD sum rules are useful tools for studying the spectral properties of hadrons; however, assumptions underlying standard sum-rule analyses can lead to inconsistencies with known results of chiral perturbation theory. This possibility is demonstrated with QCD sum-rule extractions of the nucleon mass and $\sigma$ term. In both cases, inconsistent chiral behavior leads to an uncertainty in the sum-rule predictions of $\sim 100\,\text{MeV}$.