Radiative transitions in charmonium from $N_f=2$ twisted mass lattice QCD

Abstract

We present a study for charmonium radiative transitions: $J/\ddot{I}ˆ\to \hat{I}{\cdot }_c{\hat{I}}^3$, $\ddot{I}{‡}_{c0}\to J/\hat{I}¨{\hat{I}}^3$ and $h_c\to \hat{I}{\cdot }_c{\hat{I}}^3$ using $N_f=2$ twisted mass lattice QCD gauge configurations. The single-quark vector form factors for $\hat{I}{\cdot }_c$ and $\ddot{I}{‡}_{c0}$ are also determined. The simulation is performed at a lattice spacing of $a=0.06666$ fm and the lattice size is $32^3\times 64$. 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.

typeset with revtex, 15 pages, 11 figures, 4 tables