Resonance Parameters for the rho-meson from Lattice QCD

Abstract: We present a calculation of the phase-shift for $\pi$-$\pi$ scattering in isospin-1, spin-1 channel in the elastic region. The mass and width of the rho resonance is extracted by fitting these phaseshifts. To vary the scattering momentum we employ asymmetric boxes. We use $N_f = 2$ nHYP-smeared clover fermions and generate two sets of ensembles with pion masses about 315MeV and 227MeV. To determine the phase shifts we compute the energy spectrum both for states at rest and boosted. We employ a variational analysis with interpolating fields including several $q$-$\bar{q}$ and $\pi$-$\pi$ interpolating fields with different scattering momenta.