CP Violating Phases, Nonuniversal Soft Breaking And D-brane Models

TL;DR

This paper investigates CP violation and electric dipole moments in supergravity and D-brane models, highlighting fine-tuning issues and parameter space constraints to satisfy experimental EDM bounds.

Contribution

It analyzes CP violating phases in nonuniversal soft breaking supergravity and D-brane models, revealing fine-tuning problems and parameter space restrictions for EDM compliance.

Findings

Fine tuning of phases is necessary to meet EDM constraints.

Large electroweak scale phases are possible with fine tuning.

EDM constraints limit tanβ to less than about 5 in most cases.

Abstract

The question of CP violating phases and electric dipole moments (EDMs)for the electron ($d_e$) and the neutron ($d_n$) for supergravity models with nonuniversal soft breaking is considered for models with a light ($\stackrel{<}{\sim}$1 TeV) mass spectrum and R-parity invariance. As with models with universal soft breaking (mSUGRA) one finds a serious fine tuning problem generally arises for $\theta_{0B}$ (the phase of the B soft breaking parameter at the GUT scale), if the experimental EDM constraints are obeyed and radiative breaking of $SU(2)_L\times U(1)_Y$ occurs. A D-brane model where $SU(3)_C\times U(1)_Y$ is associated with one set of 5-branes and $SU(2)_L$ with another intersecting set of 5-branes is examined, and the cancellation phenomena is studied over the parameter space of the model. Large values of $\theta_B$ (the phase of B at the electroweak scale) can be accommodated, though again $\theta_{0B}$ must be fine tuned. Using the conventional prescription for calculating $d_n$, one finds the region in parameter space where the experimental EDM constraints on both $d_e$ and $d_n$ hold is significantly reduced, and generally requires tan$\beta\stackrel{<}{\sim}$5 for most of the parameter space, though there are small allowed regions even for tan$\beta\stackrel{>}{\sim}$10. We find the Weinberg three gluon term generally makes significant contributions, and results are sensitive to the values of quark masses.