A Yukawa coupling parameterization for type I+ II seesaw formula and applications to lepton flavor violation and leptogenesis

TL;DR

This paper introduces a new parameterization for the neutrino Yukawa couplings in type I+II seesaw models, enabling detailed studies of neutrino properties, lepton flavor violation, and leptogenesis.

Contribution

It generalizes the Casas-Ibarra parameterization to include type I+II seesaw contributions, facilitating analysis when the triplet term is known.

Findings

Provides a practical framework for neutrino mass and mixing analysis.

Enables detailed study of lepton flavor violating processes.

Supports investigation of leptogenesis scenarios.

Abstract

In the type I + II seesaw formula the mass matrix of light neutrinos m_nu receives contributions from the exchanges of both heavy Majorana neutrinos and SU(2)_L-triplet Higgs bosons. We propose a new parameterization for the Dirac-type Yukawa coupling matrix of neutrinos in this case, which generalizes the well known Casas-Ibarra parameterization to type I + II seesaw and is useful when the triplet term in m_nu is known. Neutrino masses and mixing, lepton flavor violation in decays like mu -> e \gamma within mSUGRA models and leptogenesis can then be studied within this framework. We illustrate the usefulness of our new parameterization using a number of simple examples.