Constrained MSSM and the electric dipole moment of the neutron

Abstract

We study the constraints on the CP-violating soft-breaking phases in the minimal supersymmetric standard model using the limits on the chromoelectric dipole moment of the strange quark extracted from the neutron EDM experiment. Our investigation shows that the phase mediated by the gluino exchange diagram has to be very small, $\phi\leq 8 10^{-4}$, for the common supersymmetric mass of the order of 100 GeV. Then, solving the renormalization group equations analytically by iterations, we calculate the electric dipole moment of the neutron in the MSSM with CP-conserving soft-breaking parameters for the case of three and four generations. For the three-generation case we resolve the apparent discrepancies between order-of-magnitude estimates and numerical calculations existing in the literature. In this case the EDM of the neutron does not exceed $10^{-32} e cm$. For the four-generation case we show that there is a significant enhancement which renders the EDM of the neutron at a measurable level of $10^{-26}e cm$.