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 tub e model of hybrid mesons. Our numerical results use a Hamiltonian Mont e Carlo algorithm and so improve on previous analytical treatments, wh ich assumed small flux tube oscillations and an adiabatic separation o f quark and flux tube motion. We find that the small oscillation appro ximation is inappropriate for typical hadrons and that the hybrid mass is underestimated by the adiabatic approximation. For physical parame ters in the ''one-bead'' flux tube model we estimate the lightest hybr id masses ((Lambda)L = P-1 states) to be 1.8-1.9 GeV for u ($) over ba r u hybrids, 2.1-2.2 GeV for s ($) 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 als o 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 q uarks (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 t he P-1 has a 0(+-) and the D-1 contains a 3(-+). Hybrid mesons with do ubly excited hwr tubes are also considered. The implications of our re sults for spectroscopy are discussed, with emphasis on charmonium hybr ids, which may be accessible at facilties such as BEPC KEK, a Tan-Char m Factory, and in psi production at hadron colliders.