Leptonic CP violation from a vector-like lepton

TL;DR

This paper explores how a heavy vector-like lepton can induce spontaneous leptonic CP violation, linking non-decoupling effects to CP violation and analyzing constraints from flavor processes.

Contribution

It introduces a model where a heavy vector-like lepton induces spontaneous leptonic CP violation and examines its implications and constraints.

Findings

Non-decoupling of VLL is linked to CP violation.

VLL couplings are of similar magnitude due to large mixing angles.

Constraints from charged lepton flavor violation are strong but sensitive to neutrino phases.

Abstract

Leptonic CP violation is yet to be confirmed as an additional source of CP violation in fundamental interactions. We study the case where leptonic CP violation is spontaneous and is induced by the mixing with a heavy charged vector-like lepton (VLL). We show that the non-decoupling of this VLL is linked with the presence of CP violation and its coupling with the SM leptons are partly fixed from the SM Yukawas. Due to the large leptonic mixing angles, these couplings are typically of the same order and there is no flavor preference. Strong but not definitive constraints come from charged lepton flavor violating processes because the VLL can decouple from one or two leptonic flavors in very special points of parameter space. These special points are very sensitive to the neutrino Majorana phases.