Leptogenesis from magnetic helicity of gauged $\text{U}(1)_{B-L}$

TL;DR

This paper proposes a novel leptogenesis mechanism where magnetic helicity of a gauged $B-L$ field, generated during axion inflation, leads to the observed matter-antimatter asymmetry after certain decoupling and decay processes.

Contribution

It introduces a new leptogenesis scenario based on the magnetic helicity of gauged $B-L$ symmetry, linking early universe magnetic fields to baryon asymmetry.

Findings

Magnetic helicity of $B-L$ gauge field can generate $B-L$ asymmetry.

The scenario can produce the observed baryon asymmetry.

Decoupling and decay of magnetic helicity are key steps in the process.

Abstract

If the $B-L$ symmetry is gauged with the addition of right-handed neutrinos, the standard model $B-L$ current is anomalous with respect to the $B-L$ gauge field itself. Then, the anomaly relation implies that the magnetic helicity of the $B-L$ gauge field is related to the standard model $B-L$ charges, although the whole universe is $B-L$ neutral with right-handed neutrinos. Based on this, we propose a new leptogenesis scenario with the gauged $B-L$ symmetry as follows. First, the magnetic helicity of the $B-L$ gauge field is generated, e.g., by the axion inflation, together with the standard model and right-handed neutrino $B-L$ charges, with the net $B-L$ charge kept zero. The $B-L$ charges in the standard model and right-handed neutrino sectors are then subject to washout effects from the interactions between them. After the washout effects decouple, the $B-L$ gauge symmetry is Higgsed and the magnetic helicity of the $B-L$ gauge field decays and generates $B-L$ charges in the both sector; thanks to the washout effects, we obtain a non-zero $B-L$ asymmetry. We show that the baryon asymmetry of the universe can be generated in this scenario, discussing the decay of the magnetic helicity of the $B-L$ gauge field and the interactions between the right-handed neutrinos and the standard model particles.