Systematics of quark-antiquark states: where are the lightest glueballs?

Abstract

The analysis of the experimental data of Crystal Barrel Collaboration on the p anti-p annihilation in flight with the production of mesons in the final state resulted in a discovery of a large number of mesons over the region 1900-2400 MeV, thus allowing us to systematize quark-antiquark states in the (n,M^2) and (J,M^2) planes, where n and J are radial quantum number and spin of the meson with the mass M. The data point to meson trajectories in these planes being approximately linear, with a universal slope. Basing on these data and results of the recent K-matrix analysis a nonet classification is performed. In the scalar-isoscalar sector, the broad resonance state f0(1200-1600) is superfluous for the q anti-q classification, i.e. it is an exotic state. The ratios of coupling constants for the transitions f0-> pi pi, K anti-K, eta eta, eta eta' point to the gluonium nature of the broad state f0(1200-1600). The problem of the location of the lightest pseudoscalar glueball is also discussed.