The decay of the observed JPC=1-+ (1400) and JPC=1-+ (1600) hybrid candidates

We study the possible interpretation of the two exotic resonances J(PC) = 1(-+) at 1400 and 1600 MeV, claimed to be observed by BNL, decaying, respectively, into eta pi, eta ' pi, f(1)pi and rho pi. These objects are interpreted as hybrid mesons, in the quark-gluon constituent model using a chromoharmonic confining potential. The quantum numbers J(PC)I(G) = 1(-+)1(-) can be considered in a constituent model as an hybrid meson (q (q) over barg). The lowest JPC = 1-+ states may be built in two ways: l(g) = 1 (gluon-excited) corresponding to an angular momentum between the gluon and (q (q) over bar) system, while l(q (q) over bar) = 1 (quarks-excited) corresponds to an angular momentum between q and (q) over bar. For the gluon-excited mode 1(-+) hybrids, we find the decay dominated by the b(1)pi channel, and by the rho pi channel for the quark-excited mode. In our model, neither the quark-excited nor the gluon-excited 1(-+) (1400 MeV) hybrids can decay into eta pi and eta ' pi, in contradiction with experiment. Hence, the 1400 MeV resonance seems unlikely to be an hybrid stale. The 1-+ (1600 MeV) gluon-excited hybrid is predicted with too large a total decay width, to be considered as an hybrid candidate. On the contrary the quark-excited mode has a total decay width around 165 MeV, with a pn preferred decay channel, in agreement with BNL. Our conclusion is that this resonance may be considered as a hybrid meson in rhc quark-excited mode. (C) 2001 Elsevier Science B.V. All rights reserved.