Neutrino Masses and Leptogenesis in Type I+II Seesaw Models

TL;DR

This paper investigates how neutrino masses generated by combined Type I and II seesaw mechanisms within left-right symmetric models can explain the observed baryon asymmetry of the universe through leptogenesis, considering current neutrino data and flavor effects.

Contribution

It provides a comprehensive analysis of baryogenesis via leptogenesis in combined Type I+II seesaw models, incorporating latest neutrino data and exploring CP phase effects.

Findings

Predictions for baryon to photon ratio consistent with observations.

Impact of flavor effects on leptogenesis outcomes analyzed.

Constraints on CP phases derived from successful baryon asymmetry predictions.

Abstract

The baryon to photon ratio in the present Universe is very accurately measured to be $(6.065 \pm 0.090) \times 10^{-10}$. We study the possible origin of this baryon asymmetry in the neutrino sector through the generic mechanism of baryogenesis through leptogenesis. We consider both type I and type II seesaw origin of neutrino masses within the framework of left right symmetric models (LRSM). Using the latest best fit global neutrino oscillation data of mass squared differences, mixing angles and Dirac CP phase, we compute the predictions for baryon to photon ratio keeping the Majorana CP phases as free parameters for two different choices of lightest neutrino mass eigenvalue for both normal and inverted hierarchical patterns of neutrino masses. We do our calculation with and without lepton flavor effects being taken into account. We choose different diagonal Dirac neutrino mass matrix for different flavor effects in such a way that the lightest right handed neutrino mass is in the appropriate range. We also study the predictions for baryon asymmetry when the neutrino masses arise from a combination of both type I and type II seesaw (with dominating type I term) and discriminate between several combinations of Dirac and Majorana CP phases by demanding successful predictions for baryon asymmetry.