Singlet-Doublet dark matter freeze-in: LHC displaced signatures versus cosmology

Abstract

We study the Singlet-Doublet dark matter model in the regime of feeble couplings, where the dark matter abundance is obtained via the freeze-in mechanism. As a consequence of the small couplings, the heavier particles in the model are long-lived with decay length at typical scales of collider experiments. We analyse the collider signatures of the model, characterised by displaced h and Z bosons plus missing momentum, employing current LHC searches for displaced vertices and missing energy to significantly constrain the parameter space of the model. We also take into account the cosmological bounds relevant for our light dark matter candidate arising from Lyman-α forest constraints. Our analysis emphasises the interplay between displaced signatures at the LHC and cosmology for dark matter candidates whose relic abundance is obtained through the freeze-in mechanism.

Probing dark matter freeze-in with long-lived particle signatures: MATHUSLA, HL-LHC and FCC-hh

“…This model is very similar to the singlet-doublet DM model considered in [30,41], and could be regarded as a simplified version of the Higgsino-Axino system studied in [10,27,39,40], or an analog of a would-be feebly interacting Higgsino-Bino or Higgsino-Singlino system, bearing in mind that here χ and Ψ are Dirac fermions.…”

“…(2.1) is neutral, which are significantly more challenging to probe experimentally than those with a charged parent particle 5 , particularly if the decay length of A is large, cτ A 1 m. In the following we consider B SM in Eq. (2.1) to be the SM Higgs [27,30,40].…”

“…Nevertheless, when freeze-in DM production in the early Universe proceeds via the decay of thermal bath particles [8], the corresponding feeble coupling would make these particles long-lived. Searches for long-lived particles (LLPs) at the LHC and beyond (see [25,26]) have received renewed attention in recent years from the lack of conclusive signals in prompt LHC searches for physics beyond the SM, and provide a promising avenue for probing freeze-in DM scenarios [27][28][29][30][31].…”

“…As a concrete model, we study a freeze-in DM scenario via the SM Higgs (a simple version of a supersymmetric Higgsino-Axino [27,39,40] or Higgsino-singlino system, very similar to the so-called singlet-doublet DM scenario from [30,41]). We perform an analysis of the projected sensitivity of MATHUSLA in its 100 m × 100 m (MATHUSLA100) and 200 m × 200 m (MATHUSLA200) design proposals [34], to the freeze-in DM parameter space, and study its complementarity to LLP searches with the ATLAS and CMS detectors which use displaced vertices and missing transverse energy E miss T [30]. We then analyze the improvement in sensitivity than would come from a forward detector within a future 100 TeV pp -collider (FCC-hh).…”

A long-lived stop with freeze-in and freeze-out dark matter in the hidden sector

“…We note that several works exist in the literature on supersymmetric U (1) extensions of MSSM and their implications on dark matter and collider searches (see, e.g., [29]). Also, several works on signatures of long-lived particles at colliders with freeze-in dark matter have appeared recently [30][31][32][33][34][35] as well as scenarios testing for freeze-in via direct detection [36][37][38][39][40] and indirect detection [41,42]. The analysis of this work is significantly different from these.…”