A Lattice Study of the Nucleon Excited States with Domain Wall Fermions

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We present results of our numerical calculation of the mass spectrum for isospin one-half and spin one-half non-strange baryons, i.e. the ground and excited states of the nucleon, in quenched lattice QCD. We use a new lattice discretization scheme for fermions, domain wall fermions, which possess almost exact chiral symmetry at non-zero lattice spacing. We make a systematic investigation of the negative-parity N* spectrum by using two distinct interpolating operators at β=6/g²=6.0 on a 16³ × 32 × 16 lattice. The mass estimates extracted from the two operators are consistent with each other. The observed large mass splitting between this state, N*(1535), and the positive-parity ground state, the nucleon N(939), is well reproduced by our calculations. We have also calculated the mass of the first positive-parity excited state and found that it is heavier than the negative-parity excited state for the quark masses studied.