Properties of the ρ Resonance from ππ Elastic Scattering and the Spectrum of Excited ρ Mesons Using the Stochastic LapH Method in Lattice QCD

Inclusion of multi-meson operators allows lattice QCD calculations to extract energies of resonances above two-meson thresholds, as well as to study two-meson scattering. Previously, temporal correlations involving multi-hadron operators were difficult to evaluate due to contributions from quark propagators which begin and end on the same time slice.