# Reopening the Higgs portal for Singlet Scalar Dark Matter

## TL;DR

This paper explores an extended Higgs portal model with an extra singlet scalar to evade current dark matter detection bounds, showing it can still account for observed relic abundance and remain undetected in current experiments.

## Contribution

It introduces a minimal extension with an additional singlet scalar, demonstrating how it can evade detection constraints while maintaining the correct dark matter relic density.

## Key findings

- Extra scalar allows new annihilation channels avoiding detection bounds.
- The model reproduces relic abundance for DM masses above 50 GeV.
- An effective theory can be derived by integrating out the extra scalar.

## Abstract

A real singlet scalar, connected to the Standard Model sector through a portal with the Higgs boson, is one of the simplest and most popular models for dark matter (DM). However, the experimental advances in direct and indirect DM searches, together with the latest results from the LHC, have ruled out vast areas of the parameter space of this scenario, and are expected to probe it completely within the next years, ruling it out if no signal is found. Motivated by the simplicity of this model, in this article we address a minimal, renormalizable extension that could evade detection, consisting of the addition of an extra real singlet scalar field in the dark sector. We analyze the physical constraints on the model and show that the new annihilation and/or coannihilation channels involving the extra singlet allow to reproduce the correct DM relic abundance while avoiding the bounds from direct and indirect searches for any DM mass above 50 GeV. We also show that, in some interesting regions of the parameter space, the extra particle can be integrated-out, leaving a "clever" effective theory (just involving the DM particle and the Higgs), that essentially reproduces the results.