NARROW DIPROTON RESONANCES IN NP INTERACTIONS AT 0.6-5 GEV

Spectra of the effective masses of the two protons from the reactions np --> pppi-, pppi- pi0, pppi+ pi- pi-, and pppi+ pi- pi- pi0 have been analyzed for incident-neutron energies from 0.6 to 5 GeV. Seventeen narrow resonances (GAMMA(true) almost-equal-to 1-10 MeV/c2) have been found in the effective-mass interval 1877-2300 MeV/c2, with statistical significance of about 3-6 standard deviations from a background curve constructed by ''weighted mixing. '' The spins of the resonances with masses 1937, 1965, and 1980 MeV/c2 are estimated. The most probable values are greater-than-or-equal-to 3-, greater-than-or-equal-to 3-, and greater-than-or-equal-to 4+/-, respectively. A phenomenological rotation-vibration model with a fundamental pipi interaction is described. The predictions of this model agree fairly well with the experimental data. Some interesting prospects for research on narrow hadron resonances of various types are pointed out.