Large CP Phases and the Cancellation Mechanism in EDMs in SUSY, String and Brane Models

TL;DR

The paper addresses the EDM constraints that confront large CP-violating phases in SUSY. It demonstrates an approximate scaling of EDMs in the large $|\mu|$ region under the joint scaling $m_0 \to \lambda m_0$, $m_{1/2} \to \lambda m_{1/2}$ with $\mu \to \lambda \mu$, enabling a single cancellation point to generate a whole trajectory where EDMs remain small. The authors illustrate this scaling in MSSM with radiative electroweak symmetry breaking and extend the idea to Type IIB string/brane models with non-universal gaugino masses and to a heterotic string model, where cancellations can accommodate large CP phases. This framework provides a practical method to explore SUSY parameter space with sizable CP phases within current EDM bounds and has implications for upcoming EDM experiments.

Abstract

We show that EDMs obey a simple approximate scaling under the transformation $m_0\to λm_0,m_{1/2}\to λm_{1/2}$ in the large $μ$ region when $μ$ itself obeys the same scaling, ie., $μ\to λμ$. In the scaling region the knowledge of a single point in the MSSM parameter space where the cancellation in the EDMs occur allows one to generate a trajectory in the $m_0-m_{1/2}$ plane where the cancellation mechanism holds and the EDMs are small. We illustrate these results for MSSM with radiative electro-weak symmetry breaking constraints. We also discuss a class of D brane models based on Type IIB superstring compactifications which have non-universal phases in the gaugino mass sector and allow large CP violating phases consistent with the EDM constraints through the cancellation mechanism. The scaling in these D brane models and in a heterotic string model is also discussed.