Systematics of quark-antiquark states and scalar exotic mesons
Abstract
The analysis of the experimental data of Crystal Barrel Collaboration on the p\bar 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. The sector of scalar mesons is discussed in more detail, where, on the basis of the recent K-matrix analysis, the nonet classification of quark-antiquark states is performed: in the region below 2000 MeV, two scalar nonets are fixed, that is, the basic 1^3P_0q\bar q nonet and that of the first radial excitation, 2^3P_0q\bar q. In the scalar sector, there are two states with the isospin I=0, which are extra ones with respect to the q\bar q classification, i.e. exotic states: the broad resonance f_0(1200-1600) and the light sigma-meson. The ratios of coupling constants for the transitions f0 -> pi pi, K\bar K, eta eta, eta eta' point to the gluonium nature of the broad state f0(1200-1600) and enable us to estimate the ratios of the gluonium and quarkonium components in the f0(980), f0(1300), f0(1500) and f0(1750). The performed classification of scalar meson states is in a reasonable agreement with the estimate of quarkonium components obtained from the analysis of experimental data on the radiative decays.Keywords
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