Parity-violating nucleon-nucleon force in the 1/N(c) expansion.
Several experimental investigations have observed parity violation (PV) in nuclear systems-a consequence of the weak force between quarks. We apply the 1/N(c) expansion of QCD to the P-violating T-conserving component of the nucleon-nucleon (NN) potential. We show there are two leading-order operators, both of which affect p[over →]p scattering at order N(c). We find an additional four operators at order N(c)(0)sin(2)θ(W) and six at O(1/N(c)). Pion exchange in the PV NN force is suppressed by 1/N(c) and sin(2)θ(W), providing a quantitative explanation for its nonobservation up to this time. The large-N(c) hierarchy of other PV NN force mechanisms is consistent with estimates of the couplings in phenomenological models. The PV observed in p[over →]p scattering data is compatible with natural values for the strong and weak coupling constants: there is no evidence of fine-tuning.