I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD

TL;DR

This study calculates the I=2 pi-pi scattering length and phase shift using fully-dynamical lattice QCD at multiple pion masses, employing Luscher's method and chiral extrapolation, achieving results consistent with experimental data.

Contribution

It presents the first fully-dynamical lattice QCD calculation of I=2 pi-pi scattering length at multiple pion masses with chiral extrapolation to the physical point.

Findings

Scattering length m_pi a_2 = -0.0426 with uncertainties.

Phase shift delta = -43 degrees at |p| ~ 544 MeV for m_pi ~ 484 MeV.

Results agree well with experimental measurements.

Abstract

We compute the I=2 pi-pi scattering length at pion masses of m_pi ~ 294, 348 and 484 MeV in fully-dynamical lattice QCD using Luscher's finite-volume method. The calculation is performed with domain-wall valence-quark propagators on asqtad-improved MILC configurations with staggered sea quarks at a single lattice spacing, b ~ 0.125 fm. Chiral perturbation theory is used to perform the extrapolation of the scattering length from lattice quark masses down to the physical value, and we find m_pi a_2 = -0.0426 +- 0.0006 +- 0.0003 +- 0.0018, in good agreement with experiment. The I=2 pi-pi scattering phase shift is calculated to be delta = -43 +- 10 +- 5 degrees at |p| ~ 544 MeV for m_pi ~ 484 MeV.