# Electroweak Baryogenesis and Dark Matter via a Pseudoscalar vs. Scalar

## TL;DR

This paper investigates how a pseudoscalar mediator in a fermionic dark matter model can enable electroweak baryogenesis by inducing a strong first-order phase transition, consistent with relic density and experimental constraints.

## Contribution

It demonstrates that a pseudoscalar mediator allows successful electroweak baryogenesis within dark matter models, unlike the scalar mediator case, and constrains the parameter space accordingly.

## Key findings

- Pseudoscalar mediator enables a strong first-order electroweak phase transition.
- Dark matter mass range 110-320 GeV satisfies relic density and experimental bounds.
- Scalar mediator scenario struggles to explain baryogenesis under current constraints.

## Abstract

We study the electroweak baryogenesis in a fermionic dark matter scenario with a (pseudo)scalar being the mediator in the Higgs portal. It is discussed that the electroweak phase transition turns to be first-order after taking into account the role of the (pseudo)scalar in the thermal effective potential in our extended standard model. Imposing the relic density constraint from the WMAP/Planck and the bounds from the direct detection experiments XENON100/LUX, we show that the dark matter scenario with a scalar mediator is hardly capable of explaining the baryogenesis while the same model with a pseudoscalar mediator is able to explain the baryon asymmetry. For the latter, we constrain more the model with {\it Fermi}-LAT upper limit on dark matter annihilation into $b\bar b$ and $\tau^+\tau^-$. The allowed dark matter mass that leads to correct relic abundance, renders the electroweak phase transition strongly first-order, and respects the {\it Fermi}-LAT limit, will be in the range $110-320$ GeV. The exotic and invisible Higgs decay bounds and the mono-jet search limit at the LHC do not affect the viable space of parameters.