[en] In this contribution the author briefly summarizes some interesting unsolved problems in hadron spectroscopy, with particular emphasis on recent experimental and theoretical developments in multiquark systems

[en] Short communication

[en] The decay modes of the lowest O^- glueball are studied in the framework of chiral symmetry and 1/N_C expansion

[en] The model for pions as collective modes in the glueball condensate vacuum is extended to incorporate massive quarks. The quark mass dependence of < anti ss> and f_k is calculated without resorting to chiral perturbation theory. 10 refs.; 5 figs

[en] We review the theoretical and experimental status of hermaphrodite states - mixed states of quarks and gluons. States consisting mostly of qantiqg and qqqg are discussed. The qantiqg system contains a Jsup(PC) exotic, 1^-+, which may have been seen in an etaπ⁰ partial wave analysis. We suggest a search for the I=1 1^-+ as the most unambiguous way to look for constituent glue. The low-lying 0^-+ I=0 qantiqg state may be the i(1440). Photoproduction amplitudes of qqqg states do not support the Roper P₁₁(1440) as a candidate qqqg hermaphrodite baryon

No abstract available

[en] In hadronic peripheral collisions, ordinary hadrons are produced with relatively large cross-sections, glueballs, hybrids, etc., being produced weakly, if at all. Attempts to enhance the interesting signals have been made, choosing initial or final states, or both, assumed to be rich in glue: OZI forbidden transitions, hadronic and radiative J/ψ decays, proton-antiproton annihilations, double pomeron exchanges (or at least central collisions), and, for the final states η and, even better η'. A contrario, one may also investigate reactions low in glue such as photon-photon interactions. For sure, candidates for glueballs and hybrids (or multiquark states) have been observed, and this Conference has brought a rich harvest of new and interesting results. But three major difficulties still prevent us from reaching decisive conclusions. The first one is related to the concept of resonance. The second difficulty is due to the fact that, even when a resonance with well-defined quantum numbers has been well established, there is no absolute guarantee that it is not an ordinary hadron, unless its quantum numbers are exotic (not compatible with the qantiq or qqq systems). The third difficulty is found when trying to relate several observations (different production mechanisms or decay modes) of the same object. Experimentally, these comparisons are always delicate since they are usually obtained with different techniques. With these words of caution, we shall now summarize briefly what we have learnt at Hadron 89 on light quark meson spectroscopy, using as usual the qantiq model as base line and treating in turn the I=1/2,I=1,I=0 (santis) and I=0 (non santis) sectors. At the end, we shall make a few comments on exotic candidates

[en] Glueballs are widely believed to be part of the spectrum of quantum chromodynamics, but QCD provides little detailed information about them. It is necessary to use various models to circumvent this difficulty. Here, the bag model is described and its principal advantages are discussed. Finally, several testable consequences of the model are mentioned, e.g. that glueballs are light and that the E(1420) state is a glueball

[en] Besides the widely known rotations of a straight-line string, there exist rotations of a closed string whose shape is more complicated. The found solutions should be considered as a string model of quarkless hadrons-glueballs

[en] The properties of the G(1590) meson recently discovered at the Institute of High Energy Physics are analyzed by using a model based on the assumption that the interaction between hadrons is carried by their confined components (by the virton spinor and vector fields). The available experimental data support the assertion that the G(1590) meson is a scalar gluonium