HYBRID AND CONVENTIONAL MESONS IN THE FLUX TUBE MODEL - NUMERICAL-STUDIES AND THEIR PHENOMENOLOGICAL IMPLICATIONS

We present results from analytical and numerical studies of a flux tube model of hybrid mesons. Our numerical results use a Hamiltonian Monte Carlo algorithm and so improve on previous analytical treatments, which assumed small flux tube oscillations and an adiabatic separation of quark and flux tube motion. We find that the small oscillation approximation is inappropriate for typical hadrons and that the hybrid mass is underestimated by the adiabatic approximation. For physical parameters in the ''one-bead'' flux tube model we estimate the lightest hybrid masses ((Lambda)L = P-1 states) to be 1.8-1.9 GeV for u ($) over bar u hybrids, 2.1-2.2 GeV for s ($) over bar s, and 4.1-4.2 GeV for c ($) over bar c We also determine masses of conventional q ($) over bar q mesons with L = 0 to L = 3 in this model, and confirm good agreement with experimental J-averaged multiplet masses. Mass estimates are also given for hybrids with higher orbital and flux tube excitations, The gap from the lightest hybrid level (P-1) to the first hybrid orbital excitation (D-1) is predicted to be approximate to 0.4 GeV for light quarks (q = u, d) and approximate to 0.3 GeV for q = c. Both P-1 and D-1 hybrid multiplets contain the exotics 1(-+) and 2(+-); in addition the P-1 has a 0(+-) and the D-1 contains a 3(-+). Hybrid mesons with doubly excited hwr tubes are also considered. The implications of our results for spectroscopy are discussed, with emphasis on charmonium hybrids, which may be accessible at facilties such as BEPC KEK, a Tan-Charm Factory, and in psi production at hadron colliders.