Leptogenesis During an Era of Early SU(2) Confinement

Abstract

We explore leptogenesis during a cosmological epoch during which the electroweak $SU(2)_L$ force is confined. During weak confinement, there is only one conserved non-anomalous global charge, $r$, which is a linear combination of lepton-number, baryon-number, and hypercharge. The inclusion of heavy Majorana neutrinos leads to an $r$-charge and $CP$-violating interaction, allowing for the generation of an $r$-charge asymmetry, which translates into a baryon asymmetry post $SU(2)_L$ deconfinement. Determining the resulting baryon asymmetry as a function of the model parameters, we find that the predicted baryon-asymmetry can match observations for a wide swath of parameter space. While leptogenesis under the assumption of a standard cosmology relies on the complex phase of the neutrino Yukawa couplings, the asymmetry generated in this novel background cosmology primarily depends on a strong phase from $SU(2)_L$ confinement and favors negligible $CP$-violation in the right-handed neutrino decays.