Prediction of an exotic state around 4240 MeV with JPC=1-+ as the C-parity partner of Y(4260) in a molecular picture

The possibility of the Y(4260) being the molecular state of D (D) over bar (1) (2420) + c.c. is investigated in the one boson exchange model. It turns out that the potential of J(PC) = 1(--) state formed by D (D) over bar (1) (2420) + c.c. is attractive and strong enough to bind them together when the momentum cutoff Lambda greater than or similar to 1.4 GeV. To produce the Y(4260) with correct binding energy, we need Lambda approximate to 2.25 GeV. Besides, D (D) over bar (1) (2420) + c.c. can also form a state with exotic quantum numbers, J(PC) = 1(-+), and its potential is more attractive than that of the J(PC) = 1(--) state. Therefore, an exotic state with mass around 4240 MeV [called eta(c1)(4240)] is expected to exist. Our estimation of the mass of the J(PC) = 1(-+) state in charmonium region is in agreement with those predicted by the chiral quark model and the lattice QCD. The possible decay modes and their relative widths are estimated and the results suggest that this exotic state can be searched for in eta eta(c) and eta chi(c1) channels.