Lattice study of pion-pion scattering using Nf=2+1 Wilson improved quarks with masses down to their physical values

TL;DR

This study uses lattice QCD simulations with near-physical pion masses to analyze pion-pion scattering in the rho channel, providing results consistent with experimental data and exploring the pion mass dependence of the rho decay coupling.

Contribution

It presents a lattice QCD investigation of pion-pion scattering at near-physical pion masses using improved Wilson quarks, with detailed analysis of scattering parameters and rho decay.

Findings

Results agree with experimental values

Observed weak pion mass dependence of rho coupling

Detected level repulsion indicating interaction sensitivity

Abstract

We use 2HEX smeared gauge configurations generated with an $\mathrm{N}_\mathrm{f}\mathrm{=2+1}$ clover improved Wilson action to investigate $\pi\pi$ scattering in the $\rho$ channel. The range of lattice spacings (0.054 to 0.12 fm) and space-like extents (32 and 48) allows us to extract the scattering parameters through the volume dependence of the $\pi\pi$-state energies according to L\"uscher's formalism. The pion masses (134 to 300 MeV) are light enough to allow the decay of the rho and the level repulsion observed indicates that our data are sensitive to the interaction. We analyse our data with a multi-channel GEVP variational formula. Our results are in good agreement with the experimental values and consistent with a weak pion mass dependence of the $\rho\pi\pi$ coupling constant.