Non-strange baryon masses with color hyperfine and pion exchange interactions

The masses of strangeness zero baryons, with quarks in the S, P, and D shells of a harmonic oscillator potential, are calculated in the nonrelativistic constituent quark model. While the color hyperfine interaction is known to be successful in describing the mass splittings, inclusion of pion exchanges markedly improve the mass predictions of nucleon resonances, particularly those of negative parity. Fitting to all well established non-strange baryon masses below ≅ 2 GeV/c2 significantly improves previous results. (orig.)