Forbidden frozen-in dark matter

Abstract

We examine and point out the importance of a regime of dark matter production through the freeze-in mechanism that results from a large thermal correction to a decaying mediator particle mass from hot plasma in the early Universe. We show that mediator decays to dark matter that are kinematically forbidden at the usually considered ranges of low temperatures can be generically present at higher temperatures and actually dominate the overall dark matter production, thus leading to very distinct solutions from the standard case. We illustrate these features by considering a dark Higgs portal model where dark matter is produced via decays of a scalar field with a large thermal mass. We identify the resulting ranges of parameters that are consistent with the correct dark matter relic abundance and further apply current and expected future collider, cosmological, and astrophysical limits.

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

“…In this case, DM freezes-in while the EW 10 The potential influence of the EW phase transition on freeze-in processes has already been noted and discussed, albeit for different freeze-in scenarios to the freeze-in from decay A → BSMχ considered in this work, in Refs. [16][17][18]56]. 11 Here thermal corrections are disregarded by setting…”

“…The particle ψ ± will in principle leave a short track in the detector's inner tracker before decaying, but since the decay length of ψ ± is O(1 cm) (see Eq. (3.7) and Section 6.2), such a short track typically does not affect the mono-jet event selection 18 . We first focus on the Drell-Yan pp →χ 2 χ 2 process with an ISR jet, which is mediated by an off-shell Z-boson.…”

“…Among these, the freeze-in mechanism [7,8] (see [9] for a recent review) constitutes a very appealing possibility for its simplicity and the fact that it can be invoked in a wide range of well-motivated extensions of the SM (see e.g. [10][11][12][13][14][15][16][17][18][19][20]). In freeze-in scenarios, DM particles are very feebly coupled to the thermal bath in the early Universe and never achieve thermal equilibrium, yet the coupling between DM and the thermal bath particles allows DM to be produced in decays and/or scatterings of bath particles 1 .…”

“…In addition, we discuss in detail several technical aspects of the present DM freeze-in scenario (the latter three being in fact more general): the role of the breaking of electroweak (EW) symmetry in the early Universe (the EW phase transition) on the freeze-in production of DM; the inclusion of thermal masses on the computation of the DM relic density, previously disregarded in DM freeze-in studies (there have been however very recent efforts to include these effects as part of fully-consistent DM freeze-in analyses [17][18][19]); the potential impact of 2 → 2 scattering processes on setting the DM relic abundance and the interplay between freeze-in and super-WIMP DM production mechanisms (see also [15] for a detailed analysis on the latter). Finally, we analyze the constraints from cosmology, namely from Big-Bang Nucleosynthesis (BBN) and from limits on the washout of small-scale structure via Lyman-α forest observations.…”

Spontaneous freeze out of dark matter from an early thermal phase transition

“…The possibility that the dark-matter mass might be a time-dependent quantity was studied in the past in the context of Variable-Mass Particles (VAMPs) in which dark-matter particles interact with a quintessence field [73][74][75]. Moreover, the effect of thermal corrections to the potential of a dark scalar was also used in the context of the so-called Flip-Flop vev mechanism [76,77], super-cool dark matter [78], or in the forbidden freeze-in scenario [79], where a second order phase transition is used to kinematically open or close certain annihilation or decay channels in the early universe.…”