# Implications of residual CP symmetry for leptogenesis in a model with two right-handed neutrinos

## TL;DR

This paper investigates how residual CP symmetry influences leptogenesis in a two right-handed neutrino model, revealing conditions for CP asymmetry generation and analyzing specific flavor symmetries like elta(6n^2).

## Contribution

It provides a detailed analysis of residual CP symmetries' effects on leptogenesis and lepton mixing, especially within elta(6n^2) flavor symmetry frameworks.

## Key findings

- CP asymmetries vanish with two residual CP transformations.
- A single residual CP transformation constrains the lepton mixing matrix.
- The R-matrix depends on one real parameter and has three viable forms.

## Abstract

We analyze the interplay between leptogenesis and residual symmetry in the framework of two right-handed neutrino model. Working in the flavor basis, we show that all the leptogenesis CP asymmetries are vanishing for the case of two residual CP transformations or a cyclic residual flavor symmetry in the neutrino sector. If a single remnant CP transformation is preserved in the neutrino sector, the lepton mixing matrix is determined up to a real orthogonal matrix multiplied from the right side. The $R$-matrix is found to depend on only one real parameter, it can take three viable forms, and each entry is either real or purely imaginary. The baryon asymmetry is generated entirely by the CP violating phases in the mixing matrix in this scenario. We perform a comprehensive study for the $\Delta(6n^2)$ flavor group and CP symmetry which are broken to a single remnant CP transformation in the neutrino sector and an abelian subgroup in the charged lepton sector. The results for lepton flavor mixing and leptogenesis are presented.