Reopening the Higgs portal for Singlet Scalar Dark Matter
  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.
