ELECTRIC-DIPOLE TRANSITIONS OF PSI(3770) AND S-D MIXING BETWEEN PSI(3686) AND PSI(3770)

Various E1 transition rates for psi(3770) and other ccBAR states are calculated in a QCD-motivated potential model. Relativistic corrections are found to be substantial. While a good agreement between theory and experiment is achieved for the rates of psi(2S) --> gamma-chi(cJ) and chi(cJ) --> gamma-psi(1S) (J = 0, 1, 2), the calculated rates for psi(3770) --> gamma-chi(cJ) are smaller by a factor of -2 than their experimental values obtained by the Mark III Collaboration. The S-D mixing effects are further considered and are found to be important. The mixing angle theta = -10-degrees is favored and 0 = 30-degrees is ruled out. While most observed transition rates may be explained in the theory, the disagreement between theory and the psi(3770) --> gamma-chi-1 data still remains to be clarified.