Leptonic CP problem in left-right symmetric model

TL;DR

This paper shows that in the minimal left-right symmetric model, leptonic CP violation can induce a large strong CP phase at one-loop, predicting that leptonic CP violation should be negligible to satisfy experimental bounds.

Contribution

It demonstrates that leptonic CP violation can radiatively generate a strong CP phase, leading to a testable prediction of negligible leptonic CP violation in the model.

Findings

Leptonic CP violation can generate a strong CP phase at one-loop.

Current neutron EDM bounds constrain leptonic CP violation to be negligible.

The model predicts $ ext{delta}_{CP} = 0$ or $ extpi$ in most parameter space.

Abstract

We find using the minimal left-right symmetric model that the presence of leptonic CP violation can radiatively generate a strong CP phase at the one-loop level itself, which can be beyond the current bounds established by the neutron electic dipole moment experiments. If there are no axions or unnatural cancellations, this leads to the testable prediction that leptonic CP violation must be negligibly small (Dirac phase $\delta_{CP} = 0$ or $\pi$), in a wide and interesting region of parameter space.