Two photon width of eta_c

Abstract

We discuss the measured partial width of the pseudoscalar charmonium state, ${\eta }_c$, into two photons. Predictions from potential models are examined and compared with experimental values. Including radiative corrections, it is found that present measurements are compatible both with a QCD type potential and with a static Coulomb potential, with ${\alpha }_s$ evaluated at two loops. Results are also compared with those from $\text{jpsi}$ data through the NRQCD model.

Comments: 4 Pages, 1 figure, use ws-p8-50x6-00.cls. To appear in the proceedings of the Photon 2001 Conference on The Structure and Interactions of the Photon, September 2nd-7th 2001, Ascona, Switzerland