Cross-channel study of pion scattering from lattice QCD

We use a chiral model for pion interactions, in the inverse amplitude formalism, to perform a simultaneous analysis of lattice QCD results for pion-pion scattering in all three isospin channels. The input is the finite-volume two-pion spectrum computed using lattice QCD from six ensembles on lattices elongated in one of the spatial dimensions. A two-flavor dynamical lattice QCD action is used with two quark masses corresponding to a pion mass of 315 and 224 MeV. The spectrum in the elastic region is subjected to a global fit which takes into account full correlations across isospin, pion mass and decay constant. The parameters from the fit are used to perform a chiral extrapolation to the physical point. The cross-channel fit results in a more precise determination of the parameters of the model when compared with single channel fits. We obtain, mπa0I=0=0.2132(9), and mπa0I=2=0.0433(2) as well as mσ=443(3)−i221(6) MeV and mρ=724(4)−i67(1) MeV. Several aspects of scale setting and consistency with previous analyses of lattice QCD results are discussed as well.