# Dark CP Violation and Gauged Lepton/Baryon Number for Electroweak Baryogenesis

## TL;DR

This paper proposes a novel electroweak baryogenesis mechanism involving a gauged lepton number and dark sector CP violation, generating baryon asymmetry with implications for dark matter and collider phenomenology.

## Contribution

It introduces a new baryogenesis model with gauged lepton number, dark sector CP violation, and a strong first order phase transition, extending the Standard Model.

## Key findings

- Successful generation of baryon asymmetry via dark CP violation.
- Phenomenological implications for $Z'$ boson, dark matter, and Higgs sector.
- Potential signals in electric dipole moments and collider experiments.

## Abstract

We explore the generation of the baryon asymmetry in an extension of the Standard Model where the lepton number is promoted to a $U(1)_\ell$ gauge symmetry with an associated $Z^\prime$ gauge boson. This is based on a novel electroweak baryogenesis mechanism first proposed by us in Ref. \cite{Carena:2018cjh}. Extra fermionic degrees of freedom - including a fermionic dark matter $\chi$ - are introduced in the dark sector for anomaly cancellation. Lepton number is spontaneously broken at high scale and the effective theory, containing the Standard Model, the $Z^\prime$, the fermionic dark matter, and an additional complex scalar field $S$, violates CP in the dark sector. The complex scalar field couples to the Higgs portal and is essential in enabling a strong first order phase transition. Dark CP violation is diffused in front of the bubble walls and creates a chiral asymmetry for $\chi$, which in turn creates a chemical potential for the Standard Model leptons. Weak sphalerons are then in charge of transforming the net lepton charge asymmetry into net baryon number. We explore the model phenomenology related to the leptophilic $Z^\prime$, the dark matter candidate, the Higgs boson and the additional scalar, as well as implications for electric dipole moments. We also discuss the case when baryon number $U(1)_B$ is promoted to a gauge symmetry, and discuss electroweak baryogenesis and its corresponding phenomenology.