Quark models of dibaryon resonances in nucleon-nucleon scattering

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 $I{J}^P=03^{+}$ $\Delta \Delta$ 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 ${}^3{D}_3^{NN}$ 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 ${}^5{S}_2^{\Delta \Delta }$ state that can give rise to a ${}^1{D}_2^{NN}$ resonance. None of the quark models used has bound $N\Delta$ $P$-states that might generate odd-parity resonances.

14 pages, 6 tables, 6 figures; added supplementary results, added/deleted references, added 1 figure

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• Nuclear Force from Lattice QCD
• Quark-model study of few-baryon systems
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• Dynamical Coupled-Channel Model of $\pi N$ Scattering in the W $\le$ 2 GeV Nucleon Resonance Region
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Cited by in corpus (1)

• ABC Effect in Basic Double-Pionic Fusion --- Observation of a new resonance?