Precise Determination of the I=2 pipi Scattering Length from Mixed-Action Lattice QCD

TL;DR

This paper presents a precise lattice QCD calculation of the I=2 pion-pion scattering length, employing mixed-action techniques and chiral perturbation theory to achieve an accurate physical value.

Contribution

It introduces a fully-dynamical lattice QCD approach with mixed-action chiral perturbation theory for the first time to determine the I=2 pipi scattering length.

Findings

Calculated m_pi a_pipi(I=2) = -0.04330 ± 0.00042 at physical pion mass

Achieved combined statistical and systematic uncertainties in the result

Validated the use of mixed-action lattice QCD with chiral extrapolation methods

Abstract

The I=2 pipi scattering length is calculated in fully-dynamical lattice QCD with domain-wall valence quarks on the asqtad-improved coarse MILC configurations (with fourth-rooted staggered sea quarks) at four light-quark masses. Two- and three-flavor mixed-action chiral perturbation theory at next-to-leading order is used to perform the chiral and continuum extrapolations. At the physical charged pion mass, we find m_pi a_pipi(I=2) = -0.04330 +- 0.00042, where the error bar combines the statistical and systematic uncertainties in quadrature.