A Supersymmetric Solution to CP Problems

Abstract

We analyze the minimal supersymmetric left-right model with non-re\-nor\-malizable interactions induced by higher scale physics and study its {\it CP} violating properties. We show that it: (i) solves the strong {\it CP} problem; (ii) predicts the neutron electric dipole moment well within experimental limits (thus solving the usual SUSY {\it CP} problem). In addition, it automatically conserves {\it R}-parity. The key points are that the parity symmetry forces the Yukawa couplings to be hermitean, while supersymmetry ensures that the scalar potential has a minimum with real higgs doublet vacuum expectation values. Gluino and B-L gaugino masses are automatically real. The observed {\it CP} violation in the kaon system comes, as in the Standard Model, from the Kobayashi-Maskawa-type phases. These solutions are valid for any value of the right-handed breaking scale $M_R$, as long as the effective theory below $M_R$ has only two Higgs doublets that couple fully to fermions. ({\it i.e.} the theory below $M_R$ is MSSM-like.) The potentially dangerous $SU(2)_L$ gaugino one-loop contributions to $\bar{\Theta}$ below $M_R$ can be avoided if the left-right symmetry originates from a unified theory in which the $SU(2)_{L,R}$ gaugino masses are real. As an example, we show how the left-right symmetry can be embedded in an SO(10) theory.