Extrapolation of lattice QCD results beyond the power-counting regime

TL;DR

This paper reviews resummation methods in chiral effective field theory, especially finite-range regularization, to accurately extrapolate lattice QCD results beyond the power-counting regime, identifying its limited range.

Contribution

It introduces FRR techniques to determine the power-counting regime of chiral perturbation theory, extending the applicability of chiral extrapolations beyond previous limits.

Findings

PCR extends only slightly beyond physical pion mass

FRR techniques effectively constrain chiral expansion parameters

Chiral extrapolation accuracy is achieved within 1% at m_pi ≤ 0.18 GeV

Abstract

Resummation of the chiral expansion is necessary to make accurate contact with current lattice simulation results of full QCD. Resummation techniques including relativistic formulations of chiral effective field theory and finite-range regularization (FRR) techniques are reviewed, with an emphasis on using lattice simulation results to constrain the parameters of the chiral expansion. We illustrate how the chiral extrapolation problem has been solved and use FRR techniques to identify the power-counting regime (PCR) of chiral perturbation theory. To fourth-order in the expansion at the 1% tolerance level, we find 0 \le m_pi \le 0.18 GeV for the PCR, extending only a small distance beyond the physical pion mass.