Hybrid quark-diquark baryon model

A simple hybrid quark-diquark model for the baryons is constructed as a partial solution to the well-known missing resonances problem. In this model, the quark-diquark approach is merged with the usual constituent three-quark model. The underlying idea is that the quark-diquark approach describes the excited states while the three-quark model the ground states. The spectrum is calculated through a mass formula, a generalization of the Gursey-Radicati formula, built to reproduce the rotational and vibrational Regge trajectories. Using the quark-diquark scheme, we were also able to describe the spin-flavor degrees of freedom in the framework of an algebraic model. Moreover, we have constructed a complete classifications of the possible quark-diquark states only based on group theory and thus it can be useful both for other model builders and for experimentalists.