Quark models of dibaryon resonances in nucleon-nucleon scattering

We look for Delta Delta and N Delta resonances by calculating NN scattering phase shifts of two interacting baryon clusters of quarks with explicit coupling to these dibaryon channels. Two phenomenological nonrelativistic chiral quark models giving similar low-energy NN properties are found to give significantly different dibaryon resonance structures. In the chiral quark model (ChQM), the dibaryon system does not resonate in the NNS waves, in agreement with the experimental SP07 NN partial-wave scattering amplitudes. In the quark delocalization and color screening model (QDCSM), the S-wave NN resonances disappear when the nucleon size b falls below 0.53 fm. Both quark models give an IJ(P)=03(+)Delta Delta resonance. At b=0.52 fm, the value favored by the baryon spectrum, the resonance mass is 2390 (2420) MeV for the ChQM with quadratic (linear) confinement, and 2360 MeV for the QDCSM. Accessible from the D-3(3)NN channel, this resonance is a promising candidate for the known isoscalar ABC structure seen more clearly in the pn -> d pi pi production cross section at 2410 MeV in the recent preliminary data reported by the CELSIUS-WASA Collaboration. In the isovector dibaryon sector, our quark models give a bound or almost bound S-5(2)Delta Delta state that can give rise to a D-1(2)NN resonance. None of the quark models used have bound N Delta P states that might generate odd-parity resonances.