Liu, C (reprint author), Peking Univ, Sch Phys, Beijing 100871, Peoples R China.
We present an exploratory study for charmonium radiative transitions: J/psi -> eta(c)gamma, chi(c0) -> J/Psi gamma, and h(c) -> eta(c)gamma using Nf = 2 twisted-mass lattice QCD gauge configurations. The single-quark vector form factors for eta(c) and chi(c0) are also determined. The simulation is performed at a lattice spacing of a = 0.067(2) fm and the lattice size is 32(3) x 64 with a pion mass of about 485 MeV. After extrapolation of lattice data at nonzero Q(2) to 0, we compare our results with previous quenched lattice results and the available experimental values.