SEARCHING FOR THE QUARK–DIQUARK SYSTEMATICS OF BARYONS COMPOSED BY LIGHT QUARKS q = u, d

Abstract

Supposing quark–diquark structure of baryons, we look for systematics of baryons composed of light quarks (q = u, d). We systematize baryons using the notion of two diquarks: (i) axial–vector state, [Formula: see text], with the spin SD = 1 and isospin ID = 1 and (ii) scalar one, [Formula: see text], with the spin SD = 0 and isospin ID = 0. We consider several schemes for the composed baryons: (1) with different diquark masses, [Formula: see text], (2) with [Formula: see text] and overlapping [Formula: see text] and [Formula: see text] states (resonances), (3) with/without SU(6) constraints for low-lying states (with quark–diquark orbital momenta L = 0). In the high-mass region, the model predicts several baryon resonances at M ~ 2.0–2.9 GeV . Moreover, the model gives us the double pole structure (i.e. two poles with the same Re M but different Im M) in many amplitudes at masses M ≳ 2.0 GeV . We see also that for description of low-lying baryons (with L = 0), the SU(6) constraint is needed.