Sphaleron portal baryogenesis

Abstract

Nontrivial topological vacua of non-Abelian gauge symmetry $SU(3)\times SU(2)_{L}$ of the Standard Model play an important role in baryogenesis. In particular, the baryon (and lepton) number violation from $SU(2)_{L}$ sphaleron is a crucial ingredient for baryogenesis at weak scale or higher. In this work, we point out that generically, a baryon asymmetry is induced by an asymmetry generated in the new sector through strong $SU(3)$ and/or weak $SU(2)_{L}$ sphaleron portals and vice versa. In the standard radiation-dominated early Universe, due to phenomenological constraints, the sphaleron portal baryogenesis has to take place at cosmic temperature $T\gtrsim10^{6}-10^{8}$ GeV together with a $(B-L)$-violating source. As an example, we show an explicit model where strong sphaleron portal baryogenesis occurs at the scale of Peccei-Quinn breaking to solve the strong CP problem and this coincides nicely with the scale where the Weinberg operator responsible for Majorana neutrino mass is in equilibrium.