Higgs portal dark matter in non-standard cosmological histories

Abstract

A scalar particle with a relic density set by annihilations through a Higgs portal operator is a simple and minimal possibility for dark matter. However, assuming a thermal cosmological history this model is ruled out over most of parameter space by collider and direct detection constraints. We show that in theories with a non-thermal cosmological history Higgs portal dark matter is viable for a wide range of dark matter masses and values of the portal coupling, evading existing limits. In particular, we focus on the string theory motivated scenario of a period of late time matter domination due to a light modulus with a decay rate that is suppressed by the Planck scale. Dark matter with a mass GeV is possible without additional hidden sector states, and this can have astrophysically relevant self-interactions. We also study the signatures of such models at future direct, indirect, and collider experiments. Searches for invisible Higgs decays at the high luminosity LHC or an e + e − collider could cover a significant proportion of the parameter space for low mass dark matter, and future direct detection experiments will play a complementary role.1 The phenomenology is very similar if the DM is a complex or real scalar, we take it to be real throughout. 2 This is assuming the coupling λ is not very small. If λ is tiny, ∼ 10 −10 , the DM relic abundance could be generated from freeze in [5,6]. 4 There might be a relatively minor inaccuracy in our calculation of the relic abundance for DM masses

Scalar singlet dark matter in non-standard cosmologies

“…Recent studies in Refs. [22,23], have shown that in this simple framework one can both evade the current observational constraints but expect to detect a signal in the near future. However, in order to fully understand the scenario and its observational prospects, a more detailed analysis than what was conducted in Refs.…”

Pseudo-Nambu-Goldstone dark matter: Examples of vanishing direct detection cross section

“…An order of magnitude estimate can be deduced by assuming an interaction of the form (the tree level coupling cancels at zero momentum transfer, so we only show the loop-induced one here) L hξξ ∼ λ 2 (4π) 2 v h ξ 2 (ξ is a DM particle). 11 For such interactions, the spin-independent cross section is approximately [53]…”

Freeze-in axion-like dark matter

“…The LHC data on the 125 GeV Higgs boson constrain only the coupling λ hφ if a Higgs invisible decay to ALPs is open. If produced by thermal freeze-out, ALP dark matter overcloses the universe in most of the parameter space allowed by the experimental limit on spin-independent interactions with nuclei and LHC searches for Higgs invisible decays [16]. To prevent the ALP from thermalizing with the SM plasma, one needs to make it feebly interact with the SM sector with [17] λ hφ 10 −7 .…”