Power counting regime of chiral extrapolation and beyond

Abstract

Finite-range regularised chiral effective field theory is presented in the context of approximation schemes ubiquitous in modern lattice QCD calculations. Using FRR techniques, the power-counting regime (PCR) of chiral perturbation theory can be estimated. To fourth-order in the expansion at the 1% tolerance level, we find 0 ≤ mπ < 180 MeV for the PCR, extending only a small distance beyond the physical pion mass.