Systematics of quark–antiquark states and scalar exotic mesons

Abstract

The analysis of the experimental data of Crystal Barrel Collaboration on the pp 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 was performed: in the region below 2000 MeV, two scalar nonets are fixed, that is, the basic one and the nonet of the first radial excitation. In the scalar sector, there are two states with the isospin

Regge trajectories for heavy quarkonia from the quadratic form of the spinless Salpeter-type equation

“…For light mesons, the Regge trajectories are suggested to be linear although the parameters take different values [78][79][80][81][82][83]. By fitting the experimental data, we find that the new Regge trajectory is better than the linear one even for π mesons, see Fig.…”

Towards Understanding Broad Degeneracy in Non-Strange Mesons

“…Above that region the experimental situation is worse. The only experiment which systematically looked for the non-strange resonances above 1.9 GeV (in the region 1.9-2.4 GeV) was the one carried out by the Crystal Barrel Collaboration on the protonantiproton annihilation in flight, the corresponding results are summarized in a review [26,27]. The Particle Data cites these results in the section "Further States".…”

Scalar Mesons and Low-Mass Sigma: Does the Σ Reveal the Confinement Singularity?

“…It was suggested in [49,50] that the existence of the light σ-meson may be due to a singular behaviour of forces between quark and antiquark at large distances; (in quark models they are conventionally called "confinement forces"). The scalar confinement potential, which is needed for the description of the spectrum of the qq-states in the region 1000-2000 MeV, behaves at large hadronic distances as V (c) conf inement (r) ∼ αr, where α ≃ 0.19 GeV 2 .…”