Vladimir V. Anisovich

Systematics of quark?antiquark states and scalar exotic mesons

Analysis of experimental data from the Crystal Barrel Collaboration on the in-flight pp annihilation into mesons revealed a large group of mesons in the 1900 – 2400-MeV range, allowing the systematization of quark–antiquark states in the (n, M2)- and (J, M2)-planes (n being the radial quantum number, and J the spin of a meson of mass M). From the data, meson trajectories in these planes are approximately linear and have a universal slope. A detailed discussion of the scalar meson sector is given for which, based on a recent K-matrix analysis, the nonet classification of quark–antiquark states places two scalar nonets — the basic nonet and that of the first radial excitation — in the range below 2000 MeV. Two isospin 0 scalar states — the broad resonance f0(1200–1600) and the light σ-meson — do not fit into the quark–antiquark classification, i.e., are exotic. The ratios between the coupling constants for hadronic decays to the ππ, K, ηη and ηη states point to the gluonium nature of the broad state f0(1200–1600).

The lightest scalar glueball

Recent studies of meson spectra have enabled the resonance structure of the IJ PC a 00 aa ,1 0 aa ,0 2 aa ,1 2 aa , and IJ P a 1 0 a waves to be found for masses ranging up to 1900 MeV, thus fully reconstructing the 1 3 P0qq and 2 3 P0qq meson multiplets. There is firm experimental evidence for the existence offivescalar-isoscalarstates inthismassrange,four of which are qq states and members of the 1 3 P0qq and 2 3 P0qq nonets, whereas the fifth falls out of the quark picture and displaysallthepropertiesofthelightestpossiblescalarglueball. A dispersion analysis of the 00 aa wave elucidates how the mixture of the pure glueball state (or gluonium) with neighbor- ing scalar qq states forms: three scalar mesons, namely two relatively narrow f0(1300) and f0(1500) resonances and a very broad f0(1530 a90 ˇ250) resonance, share the gluonium, the broad resonance being the gluoniums descendant and accounting for about 40 to 50% of it. To the memory of Yuri|fl Dmitrievich Prokoshkin