Scalar Triplet Leptogenesis with a CP violating phase

TL;DR

This paper investigates scalar triplet leptogenesis with CP violation, analyzing how different branching ratio hierarchies and flavor effects influence baryon asymmetry, and explores low-scale resonant leptogenesis scenarios.

Contribution

It introduces a detailed analysis of triplet scalar leptogenesis considering complex VEV phases, flavor effects, and low-scale resonant leptogenesis, extending previous models.

Findings

Hierarchical branching ratios affect CP violation and leptogenesis efficiency.

Successful baryogenesis possible with B_phi >> B_L hierarchy.

Resonant leptogenesis viable at TeV scale.

Abstract

We study baryogenesis through leptogenesis via decay of triplet scalars embedded in the Standard Model. We consider two triplets scenario where the vacuum expectation value developed by one of the triplets is complex. The coupling of the triplet Higgs with the Standard Model leptons and Higgs scalar allows two decay channels, with branching ratios $B_L$ and $B_\phi$, respectively. It is known that the hierarchy between the two branching ratios ($B_L \gg B_\phi$ or $B_\phi\gg B_L$), is sensitive to the generation of adequate CP violation and efficiency of leptogenesis. Working in a hierarchical limit of branching ratios and requiring adequate CP violation, we find the mass of the lightest triplet can be as low as $1 \times 10^{10}$ GeV. In the temperature regime $\left[ 10^{9}, 10^{12} \right]$ GeV, flavor effects, especially two-flavor effects become important in the study of leptogenesis. In two-flavored regime we study flavor effects in leptogenesis. It is observed that adequate baryon asymmetry can not be obtained for purely flavored leptogenesis, which corresponds to the hierarchical branching ratios, $B_L \gg B_\phi$. But the hierarchy in the other way $B_\phi \gg B_L$ still allows successful baryogenesis through leptogenesis. The phase of the complex vacuum expectation value of the triplet scalar is constrained by requiring non-zero CP violation. Considering the mass scale of triplet scalars as TeV scale, we also study resonant leptogenesis in the light of TeV scale physics.