QED-QCD MIXING EFFECT AND ISOSPIN VIOLATION IN S-1(0) NN SCATTERING

The charge dependence of the nucleon-nucleon scattering length due to the quark effects are examined in a quark cluster model. In addition t o the effects induced by the up-down quark mass difference and quark-e xchange Coulomb interaction, we consider the interference effects of Q CD and QED suggested by Maltman, Stephenson, and Goldman. We find that the total contribution of the quark effects to a(pp) - a(nn) is large and in the direction indicated by the experiments. The effect is, how ever, small for a(pp) - a(np).