# A Simultaneous Study of Dark Matter and Phase Transition: Two-Scalar Scenario

## TL;DR

This paper explores a two-scalar extension of the Standard Model that can simultaneously account for dark matter and a strong electroweak phase transition, overcoming limitations of single-scalar models under current experimental constraints.

## Contribution

It introduces a two-scalar model that achieves viable dark matter relic density and strong first-order phase transition while satisfying collider and direct detection constraints.

## Key findings

- Viable parameter space exists for two scalars satisfying all constraints.
- The model can explain the dark matter relic density fraction or entirety.
- Electroweak symmetry breaking can occur via different channels in the two-scalar scenario.

## Abstract

The simplest extension of the Standard Model by only one real singlet scalar can explain the observed dark matter relic density while giving simultaneously a strongly first-order electroweak phase transition in the early universe. However, after imposing the invisible Higgs decay constraint from the LHC, the parameter space of the single scalar model shrinks to regions with only a few percent of the DM relic abundance and when adding the direct detection bound, e.g. from XENON100, it gets excluded completely. In this paper, we extend the Standard Model with two real guage singlet scalars, here $s$ and $s'$, and show that the electroweak symmetry breaking may occur via different channels. Despite very restrictive first-order phase transition conditions for the two-scalar model in comparison to the single scalar model, there is a viable space of parameters in different phase transition channels that simultaneously explains a fraction or the whole dark matter relic density, a strongly first-order electroweak phase transition and still evading the direct detection bounds from the latest LUX/XENON experiments while respecting the invisible Higgs decay width constraint from the LHC.