Phase Difference Between the Electromagnetic and Strong Amplitudes for   psi(2S) and J/psi Decays into Pairs of Pseudoscalar Mesons
  Using the data for 24.5x10^6 psi(2S) produced in e^+e^- annihilations at sqrt{s}=3686 MeV at the CESR-c e^+e^- collider and 8.6x10^6 J/psi produced in the decay psi(2S)->pi^+pi^-J/psi, the branching fractions for psi(2S) and J/psi decays to pairs of pseudoscalar mesons, pi^+pi^-, K^+K^-, and K_S K_L, have been measured using the CLEO-c detector. We obtain branching fractions Br(psi(2S)->pi^+pi^-)=(7.6+-2.5+-0.6)x10^-6, Br(psi(2S)->K^+K^-)=(74.8+-2.3+-3.9)x10^-6, Br(psi(2S)->K_S K_L)=(52.8+-2.5+-3.4)x10^-6, and Br(J/psi->pi^+pi^-)=(1.47+-0.13+-0.13)x10^-4, Br(J/psi->K^+K^-)=(2.86+-0.09+-0.19)x10^-4, Br(J/psi+-K_S K_L)=(2.62+-0.15+-0.14)x10^-4, where the first errors are statistical and the second errors are systematic. The phase differences between the amplitudes for electromagnetic and strong decays of psi(2S) and J/psi to 0^{-+} pseudoscalar pairs are determined by a Monte Carlo method to be \delta(psi(2S)_{PP}=(110.5^{+16.0}_{-9.5})^o and \delta(J/psi)_{PP}=(73.5^{+5.0}_{-4.5})^o. The difference between the two is \Delta\delta = \delta(psi(2S))_{PP}-\delta(J/psi)_{PP} =(37.0^{+16.5}_{-10.5})^o. 
Z. Metreveli, S. Dobbs, A. Tomaradze, T. Xiao, Kamal K. Seth, J.   Yelton, D. M. Asner, G. Tatishvili and G. Bonvicini
hep-ex