Measurement Of The Branching Fractions For J/->Gamma Pi(0), And Gamma Eta ' And Study Of Eta '->Gamma Pi(+)Pi(-) Decay Dynamics

The decay modes J/psi -> gamma pi(0), gamma eta and gamma eta' are analyzed using a data sample of 58 million J/psi decays collected with the BESII detector at the BEPC. The branching fractions are determined to be Br(J/psi -> gamma pi(0)) = (3.13(-0.47)(+0.65) x 10(-5), Br( J/psi -> gamma eta) = (11.23 +/- 0.89) x 10(-4), and Br(J/psi -> gamma eta') = ( 5.55 +/- 0.44) x 10(-3), where the errors are combined statistical and systematic errors. The ratio of partial widths and the singlet octet pseudoscalar mixing angle of eta - eta' system is determined. The eta' -> gamma pi(+)pi(-) decay dynamics is studied using 22,000 reconstructed J/psi -> gamma eta' -> gamma gamma pi(+)pi(-) events, the pi(+)pi(-) mass spectrum is fitted using different theoretical descriptions. The preliminary results show that only the rho(770) is not enough to describe the eta' -> gamma pi(+)pi(-) decay process and a non-rho(770) contribution is needed.