Tetraquark states and spectrum

Abstract

A general classification of tetraquark states in terms of the spin-flavour, colour and spatial degrees of freedom has been constructed. The permutational symmetry properties of both the spin-flavour and orbital parts of the quark-quark and antiquark-antiquark subsystems are discussed in short. This classification is model indipendent and useful both for model-builders and experimentalists. An evaluation of the tetraquark spectrum is obtained from a generalization of a Iachello mass formula, originally developed for the $q\bar{q}$ mesons. The ground state tetraquark nonet is identified with $f_0(600)$, $\kappa (800)$, $f_0(980)$, $a_0(980)$.

Comments: Invited talk at XI Conference on Problems in Theoretical Nuclear Physics (Cortona 2006), Cortona, Italy, 11-14 Oct, 2006