We perform a dynamical calculation of the ∆∆ dibaryon candidates with IJ P = 03 + and IJ P = 30 + in the framework of two constituent quark models: the quark delocalization color screening model and the chiral quark model. Our results show that the dibaryon resonances with IJ P = 03 + and IJ P = 30 + can be formed in both models. The mass and width of IJ P = 03 + state are smaller than that of IJ P = 30 + state due to the one-gluon-exchange interaction between quarks. The resonance mass and decay width of IJ P = 03 + state in both models agree with that of the recent observed resonance in the reaction pn → dπ 0 π 0 . The IJ P = 30 + ∆∆ is another dibaryon candidate with smaller binding energy and larger width. The hidden-color channel coupling is added to the chiral quark model, and we find it can lower the mass of the dibaryons by 10-20 MeV.

Inspired by the discovery of two pentaquarks P c (4380) and P c (4450) at the LHCb detector, we study possible hidden-charm molecular pentaquarks in the framework of quark delocalization color screening model. Our results suggest that both N η c with IJ P = is a resonance, it may not be a good candidate of the observed P c (4450) because of the opposite parity of the state to P c (4380), although the mass of the state is not far from the experimental value. In addition, the calculation is extended to the hidden-bottom pentaquarks, and similar properties to that of hidden-charm pentaquarks system are obtained.

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 $NN$ $S$-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 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 $^3D_3^{NN}$ channel, this resonance is a promising candidate for the known isoscalar ABC structure seen more clearly in the $pn$$\to $$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 $^5S_2^{\Delta\Delta}$ state that can give rise to a $^1D_2^{NN}$ resonance. None of the quark models used has bound $N\Delta$ $P$-states that might generate odd-parity resonances.Comment: 14 pages, 6 tables, 6 figures; added supplementary results, added/deleted references, added 1 figur

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