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Creators/Authors contains: "A. Hanlon"

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  1. Progress in computing various meson-baryon scattering amplitudes is presented on a single en- semble from the Coordinated Lattice Simulations (CLS) consortium with m π = 200 MeV and Nf = 2 + 1 dynamical fermions. The finite-volume Lüscher approach is employed to determine the lowest few partial waves from ground- and excited-state energies computed from correla- tion matrices rotated in a single pivot using a generalized eigenvector solution. This analysis requires evaluating matrices of correlation functions between single- and two-hadron interpolat- ing operators which are projected onto definite spatial momenta and finite-volume irreducible representations. The stochastic LapH method is used to estimate all needed quark propagators. Preliminary results are presented for I = 1/2, 3/2 N π amplitudes including the ∆(1232) resonance and the I = 0 S-wave amplitude with unit strangeness relevant for the Λ(1405). 
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  2. We present the current status of our efforts in search of dibaryon on =2+1 CLS ensembles away from the (3) flavor symmetric point. Utilizing the distillation framework (also known as LapH) in its exact and stochastic forms, we calculate two-point correlation matrices using large bases of bi-local two-baryon interpolators to reliably determine the low-energy spectra. We report the low lying spectrum on several moving frames for multiple ensembles with different lattice spacing and physical volumes. The status of finite-volume analysis to extract the scattering amplitudes is also discussed. 
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  3. Lattice QCD calculations of two-nucleon interactions have been underway for about a decade, but still haven’t reached the pion mass regime necessary for matching onto effective field theories and extrapolating to the physical point. Furthermore, results from different methods, including the use of the Lüscher formalism with different types of operators, as well as the HALQCD potential method, do not agree even qualitatively at very heavy pion mass. We investigate the role that different operators employed in the literature may play on the extraction of spectra for use within the Lüscher method. We first explore expectations from Effective Field Theory solved within a finite volume, for which the exact spectrum may be computed given different physical scenarios. We then present preliminary lattice QCD results for two-nucleon spectra calculated using different operators on a common lattice ensemble. 
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