Leptogenesis from the Dirac CP-violating phase in the minimal left-right symmetric model

TL;DR

This paper demonstrates that in a minimal left-right symmetric model, the Dirac CP-violating phase alone can generate the observed baryon asymmetry through leptogenesis, linking low-energy neutrino physics to cosmological matter-antimatter asymmetry.

Contribution

It shows that the Dirac CP phase can be the sole source of leptogenesis in this model, with minimal assumptions on high-energy parameters, and explores the parameter space for successful baryogenesis.

Findings

Dirac CP phase can produce the observed baryon asymmetry.

Leptogenesis sensitivity depends on neutrino mass ordering.

The framework is testable with future neutrino experiments.

Abstract

Leptogenesis from low-energy CP violation provides a vital link between neutrino physics and the observed baryon asymmetry of the universe. However, this connection is typically obscured by unknown high-energy parameters. In this work, we investigate thermal leptogenesis in the Minimal Left-Right Symmetric Model with generalized parity as the left-right symmetry, where the hermiticity of the Dirac neutrino coupling allows the right-handed mixing matrix $V_\mathrm{R}$ to be determined with minimal assumptions. We show that for a real $V_\mathrm{R}$, these conditions favor CP-conserving Majorana phases, leaving the Dirac CP-violating phase ($\delta$) as the sole source of asymmetry. By numerically exploring all four leptogenesis scenarios, we demonstrate that $\delta$ alone can generate the observed baryon asymmetry with the correct sign within specific regions of the parameter space. The results exhibit a high sensitivity to the neutrino mass ordering and the lightest neutrino mass, providing a stringent, testable framework for future experimental measurements of the CP phase and neutrino mass scale.