Speaker
Description
Recent lattice QCD results for the first two low-lying odd-parity excitations of the nucleon have revealed that they have magnetic moments consistent with constituent-quark-model expectations. Thus, in constructing a basis of states to describe scattering in this channel, one should not represent both odd-parity excitations by a single three-quark basis state. Two single-particle basis states are required to accommodate these two quark-model-like states. This contrasts previous studies where it has been assumed that both low-lying negative-parity states observed on the lattice are part of the finite-volume spectrum associated with the N(1535) resonance. Using Hamiltonian Effective Field Theory (HEFT), we represent these constituent-quark-like states by including two single-particle basis states in the Hamiltonian, mixing through meson-baryon scattering channels. By constraining the parameters of HEFT using S-wave pion-Nucleon scattering data, we perform the first calculation of the finite-volume energy spectrum for this system using multiple single-particle basis states.
