The ρ-resonance from N = 2 lattice QCD including the physical pion mass
Matthias Fischer, Bartosz Kostrzewa, Maxim Mai, Marcus Petschlies, Ferenc Pittler, Martin Ueding, Carsten Urbach, M. Werner
Abstract
We present a lattice computation of ππ–scattering in the I=1 channel with Nf=2 dynamical quark flavours obtained with ensembles bracketing the 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 ρ-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, exploring the complex energy plane we find mass Mρ=786(22)MeV and width Γρ=180(6)MeV, including statistical and systematic uncertainties. In contrast to previous Nf=2 extrapolations from higher than physical pion mass results, our mass value is in good agreement with experiment, while the width is too high.