Quark models of dibaryon resonances in nucleon-nucleon scattering

TL;DR

This study investigates dibaryon resonances in nucleon-nucleon scattering using two quark models, revealing different resonance structures and identifying a promising candidate for the ABC resonance at 2410 MeV.

Contribution

It compares two phenomenological quark models, showing their differing predictions for dibaryon resonances and connecting results to experimental observations.

Findings

ChQM does not predict NN S-wave resonances, aligning with experimental data.

QDCSM predicts an NN S-wave resonance disappearing below a nucleon size of 0.53 fm.

Both models find a $$ resonance near 2360-2420 MeV, matching the ABC structure.

Abstract

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.