with charmonium?

Hybrid cc̄g of quantum numbers 1−− are considered in a quark model with constituant quarks and gluon. The lowest JP = 1− states may be built in two ways, lg = 1 (gluon excited) corresponding to an angular momentum between the gluon and the cc̄ system, while lcc̄ = 1 (quark excited) corresponds to an angular momentum between the c and the c̄. The lowest lying hybrid JP = 1− state in the flux tube model is similar to the lg = 1 in the quark-gluon model. In particular it verifies the selection rule that it cannot decay into two fundamental mesons. The lqq̄ = 1 hybrid may decay into two fundamental mesons, but with decay widths larger than 1 GeV, which tells that they do not really exist as resonant states. Using a chromoharmonic potential, we find no mixing between the lg = 1 and lcc̄ = 1. More realistic potentials might induce a strong mixing between them, implying that no hybrid meson exist. If, on the contrary, such a strong mixing does not occur, we find, in agreement with the flux tube model, that only the lg = 1 appears as a real resonant state. In such a case, hybrid mesons may exist as resonances only if they are decoupled from the ground state channels, which explains the difficulty to observe them experimentally. We reconsider accordingly the Ono-Close-Page scenario of mixing between charmonium and charmed-hybrid to explain the anomalies around 4.1 GeV. We find a very small mixing between radially excited charmonium and hybrid mesons, which forbids considering the ψ(4.040) and ψ(4.160) as combinations of 3S charmonium and lg = 1 hybrid meson with a large mixing. LPT Oran 10/97 LPTHE Orsay-97-71 hep-ph/9803470 e-mail: [email protected] 2 Laboratoire associé au Centre National de la Recherche Scientifique URA D00063