We present the first determination of ρπ scattering, incorporating dynamicallycoupled partial-waves, using lattice QCD, a first-principles numerical approach to QCD. Considering the case of isospin-2 ρπ, we calculate partial-wave amplitudes with J ≤ 3 and determine the degree of dynamical mixing between the coupled S and D-wave channels with J P = 1 + . The analysis makes use of the relationship between scattering amplitudes and the discrete spectrum of states in the finite volume lattice. Constraints on the scattering amplitudes are provided by over one hundred energy levels computed on two lattice volumes at various overall momenta and in several irreducible representations of the relevant symmetry groups. The spectra follow from variational analyses of matrices of correlations functions computed with large bases of meson-meson operators. Calculations are performed with degenerate light and strange quarks tuned to the physical strange quark mass so that m π ∼ 700 MeV, ensuring that the ρ is stable against strong decay. This work demonstrates the successful application of techniques, opening the door to calculations of scattering processes that incorporate the effects of dynamically-coupled partial-waves, including those involving resonances or bound states.

We present the first lattice QCD calculation of coupled πω and πφ scattering, incorporating coupled S and D-wave πω in J P = 1 + . Finite-volume spectra in three volumes are determined via a variational analysis of matrices of two-point correlation functions, computed using large bases of operators resembling single-meson, two-meson and three-meson structures, with the light-quark mass corresponding to a pion mass of mπ ≈ 391 MeV. Utilizing the relationship between the discrete spectrum of finite-volume energies and infinite-volume scattering amplitudes, we find a narrow axial-vector resonance (J P C = 1 +− ), the analogue of the b1 meson, with mass mR ≈ 1380 MeV and width ΓR ≈ 91 MeV. The resonance is found to couple dominantly to S-wave πω, with a muchsuppressed coupling to D-wave πω, and a negligible coupling to πφ consistent with the 'OZI rule'. No resonant behavior is observed in πφ, indicating the absence of a putative low-mass Zs analogue of the Zc claimed in πJ/ψ. In order to minimally present the contents of a unitary three-channel scattering matrix, we introduce an n-channel generalization of the traditional two-channel Stapp parameterization.

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We present a method of performing high-speed rotational anisotropy nonlinear optical harmonic generation experiments at rotational frequencies of several hertz by projecting the harmonic light reflected at different angles from a sample onto a stationary position-sensitive detector. The high rotational speed of the technique, 10 3 to 10 4 times larger than existing methods, permits precise measurements of the crystallographic and electronic symmetries of samples by averaging over low frequency laser-power, beampointing, and pulse-width fluctuations. We demonstrate the sensitivity of our technique by resolving the bulk fourfold rotational symmetry of GaAs about its [001] axis using second-harmonic generation.

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