EXOTIC MESONS IN QUENCHED LATTICE QCD

Since gluons in QCD are interacting fundamental constituents just as q uarks are, we expect that in addition to mesons made from a quark and an antiquark, there should also be glueballs and hybrids (bound states of quarks, antiquarks, and gluons). In general, these states would mi x strongly with the conventional <(q)over bar q> mesons. However, they can also have exotic quantum numbers inaccessible to <(q)over bar q> mesons. Confirmation of such states would give information on the role of ''dynamical'' color in low energy QCD. In the quenched approximati on we present a lattice calculation of the masses of mesons with exoti c quantum numbers. These hybrid mesons can mix with four quark (<(qq)o ver bar qq>) states. The quenched approximation partially suppresses t his mixing. Nonetheless, our hybrid interpolating fields also couple t o four quark states. Using a four-quark source operator, we demonstrat e this mixing for the 1(-+) meson. Using the conventional Wilson quark action, we calculate both at reasonably light quark masses, intending to extrapolate to small quark mass, and near the charmed quark mass, where we calculate the masses of some <(c)over bar cg> hybrid mesons. The hybrid meson masses are large-over 4 GeV for charmonium and more t han twice the vector meson mass at our smallest quark mass, which is n ear the strange quark mass. [S0556-2821(97)06123-7].