The $\rho$-resonance with physical pion mass from $N_f=2$ lattice QCD

TL;DR

This paper reports the first lattice QCD calculation of the rho resonance with physical pion mass, providing precise resonance parameters and comparing different analysis methods.

Contribution

It presents the first Nf=2 lattice QCD computation of the rho resonance at physical pion mass, including systematic uncertainty analysis.

Findings

Resonance mass: 786(20) MeV

Resonance width: 180(6) MeV

Good agreement with experimental mass, slightly higher width

Abstract

We present the first-ever lattice computation of pi pi-scattering in the I=1 channel with Nf=2 dynamical quark flavours obtained including an ensemble with physical value of the pion mass. Employing a global fit to data at three values of the pion mass, we determine the universal parameters of the rho-resonance. We carefully investigate systematic uncertainties by determining energy eigenvalues using different methods and by comparing inverse amplitude method and Breit-Wigner type parametrizations. Overall, we find mass 786(20) MeV and width 180(6) MeV, including statistical and systematic uncertainties. In stark disagreement with the previous Nf=2 extrapolations from higher than physical pion mass results, our mass value is in good agreement with experiment, while the width is slightly too high.