Neutrino assisted GUT baryogenesis - revisited

TL;DR

This paper revisits GUT baryogenesis, demonstrating how right-handed neutrinos can prevent washout of baryon asymmetry by sphalerons, through numerical solutions of Boltzmann equations in realistic neutrino scenarios.

Contribution

It extends previous work by analyzing flavor effects and identifying parameter regions for successful baryogenesis with right-handed neutrinos.

Findings

Right-handed neutrinos can erase lepton asymmetry before sphaleron washout.

Flavor effects significantly influence baryogenesis outcomes.

Large parameter space allows successful baryogenesis with specific Yukawa couplings and neutrino masses.

Abstract

Many GUT models conserve the difference between the baryon and lepton number, $B-L$. These models can create baryon and lepton asymmetries from heavy Higgs or gauge boson decays with $B+L \neq 0$ but with $B-L=0$. Since the sphaleron processes violate $B+L$, such GUT-generated asymmetries will finally be washed out completely, making GUT baryogenesis scenarios incapable of reproducing the observed baryon asymmetry of the Universe. In this work, we revisit the idea to revive GUT baryogenesis, proposed by Fukugita and Yanagida, where right-handed neutrinos erase the lepton asymmetry before the sphaleron processes can significantly wash out the original $B+L$ asymmetry, and in this way one can prevent a total washout of the initial baryon asymmetry. By solving the Boltzmann equations numerically for baryon and lepton asymmetries in a simplified 1+1 flavor scenario, we can confirm the results of the original work. We further generalize the analysis to a more realistic scenario of three active and two right-handed neutrinos to highlight flavor effects of the right-handed neutrinos. Large regions in the parameter space of the Yukawa coupling and the right-handed neutrino mass featuring successful baryogenesis are identified.