Leptonic CP and Flavor Violations in SUSY GUT with Right-handed Neutrinos

TL;DR

This paper investigates how renormalization group effects in SUSY GUT models with right-handed neutrinos can lead to significant leptonic CP and flavor violations, independent of the right-handed neutrino mass scale, potentially observable in experiments.

Contribution

It demonstrates that the maximal leptonic CP and flavor violating signals are insensitive to right-handed neutrino masses when considering the Casas-Ibarra parametrization.

Findings

Leptonic CP and flavor violation signals can be large enough to be experimentally detectable.

Signals are insensitive to the right-handed neutrino mass scale.

Casas-Ibarra parameters significantly influence CP and flavor violating observables.

Abstract

We study leptonic CP and flavor violations in supersymmetric (SUSY) grand unified theory (GUT) with right handed neutrinos, paying attention to the renormalization group effects on the slepton mass matrices due to the neutrino and GUT Yukawa interactions. In particular, we study in detail the impacts of the so-called Casas- Ibarra parameters on CP and flavor violating observables. The renormalization group effects induce CP and flavor violating elements of the SUSY breaking scalar mass squared matrices, which may result in sizable leptonic CP and flavor violating signals. Assuming seesaw formula for the active neutrino masses, the renormalization group effects have been often thought to be negligible as the right-handed neutrino masses become small. With the most general form of the neutrino Yukawa matrix, i.e., taking into account the Casas-Ibarra parameters, however, this is not the case. We found that the maximal possible sizes of signals of leptonic CP and flavor violating processes are found to be insensitive to the mass scale of the right-handed neutrinos and that they are as large as (or larger than) the present experimental bounds irrespective of the right-handed neutrino masses.