Coupled ππ, KK̅ scattering in P-wave and the ρ resonance from lattice QCD

Abstract

We determine elastic and coupled-channel amplitudes for isospin-1 meson-meson scattering in P-wave, by calculating correlation functions using lattice QCD with light quark masses such that m_π = 236 MeV in a cubic volume of ∼ (4 fm)³. Variational analyses of large matrices of correlation functions computed using operator constructions resembling ππ, KK̅ and qq̅, in several moving frames and several lattice irreducible representations, leads to discrete energy spectra from which scattering amplitudes are extracted. In the elastic ππ scattering region we obtain a detailed energydependence for the phase-shift, corresponding to a ρ resonance, and we extend the analysis into the coupled-channel KK̅ region for the first time, finding a small coupling between the channels