Universal phase between strong and eletromagnetic interactions
  It is shown that the experimental data of psi(3686) and psi(3770) are consistent with a -90 degree phase between the strong and eletromagnetic decay amplitudes. The e+ e- -> rho-pi measured at psi(3770) is also consistent with the branching ratio predicted by Rosner's scenario on rho-pi puzzle in charmonium physics. This scenario leads to a possible large charmless branching ratio in psi(3770) decays. 
P. Wang