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In this paper, low-energy scattering of the (D*...*)± meson system is studied within Liischer's finite-size formalism using Nf = 2 twisted-mass gauge field configurations. With three different pion mass values, the 5-wave threshold scattering parameters--namely the scattering length a0 and the effective range r0--are extracted in the JPC = l+- channel. Our results indicate that, in this particular channel, the interaction between the two vector charmed mesons is weakly repulsive in nature and hence it does not support the possibility of a shallow bound state for the two mesons, at least for the pion mass values being studied. However, these results might suffer from undetermined systematic errors due to low-lying states ignored in this exploratory study. Still, it provides some useful information on the nature of the newly discovered resonance-like structure Zc(4025) observed in various experiments. [ABSTRACT FROM AUTHOR]

We present an exploratory study for charmonium radiative transitions: J/ψ → ηcγ χc0 → J/ψγ, and hc → ηcγ using Nf = 2 twisted-mass lattice QCD gauge configurations. The single-quark vector form factors for ηc and χc0 are also determined. The simulation is performed at a lattice spacing of α = 0.067(2) fm and the lattice size is 32³ x 64 with a pion mass of about 485 MeV. Alter extrapolation of lattice data at nonzero Q² to 0, we compare our results with previous quenched lattice results and the available experimental values. [ABSTRACT FROM AUTHOR]