Elastic nucleon-pion scattering amplitudes in the channel at physical pion mass from lattice QCD

We present an investigation of pion -nucleon elastic scattering in the I(J(P)) = 3/2 (3/2(+)) channel using lattice 2 QCD with degenerate up and down, strange and charm quarks with masses tuned to their physical values. We use an ensemble of twisted mass fermions with box size L = 5.1 fm and lattice spacing a = 0.08 fm and we consider the NN system in rest and moving frames up to total momentum (p) over bar (2) = 3(2 pi/L)(2) = 0.17 GeV2. We take into account the finite volume symmetries and S- and P -wave mixing, and use the Luscher formalism to simultaneously constrain the J = 1/2, l = 0 and J = 3/2, l = 1 scattering amplitudes. We estimate the Delta resonance pole in the P -wave channel as well as the S -wave isospin-3/2 scattering length.