Probing pre-BBN era with scale invariant FIMP

Abstract

Detecting dark matter (DM) relic via freeze-in is difficult in laboratories due to smallness of the couplings involved. However, a non-standard cosmological history of the Universe, prior to Big Bang Nucleosynthesis (BBN), can dramatically change this scenario. In this context, we study the freeze-in production of dark matter (DM) in classically scale invariant U(1) X gauge extension of the Standard Model (SM), recently dubbed as the Scale Invariant FIMP Miracle. We assume an additional species dominates the energy density of the Universe at early times, causing the expansion rate at a given temperature to be larger than that in the standard radiation-dominated case. We find, the out-of-equilibrium scattering processes involving particles in the thermal bath lead to significantly suppressed DM production in this era, thereby enhancing the couplings between the visible and the dark sector (by several orders of magnitude) to satisfy the observed DM abundance, and improving the detection prospects for freeze-in in turn. Scale invariance of the underlying theory leaves only four free parameters in the model: the DM mass mX , the gauge coupling gX , the temperature of transition TR from early scalar-dominated to radiation-dominated era and the power-law dependence n of this temperature. We show, within this minimal set-up, experiments like FASER, MATHUSLA, DUNE, SHiP will be probing various cosmological models depending on the choice of {n, TR } that also satisfy the PLANCK observed relic density bound. Moreover, due to the presence of a naturally light scalar mediator, the direct detection of the DM at XENON1T, PandaX-4T or XENONnT becomes relevant for Higgs-scalar mixing sinθ ≃ {10-5–10-3}, thus providing complementary probes for freeze-in, as well as for non-standard cosmological pre-BBN era.

Signatures of non-thermal dark matter with kination and early matter domination. Gravitational waves versus laboratory searches

“…When studying the testability of our non-thermal DM production mechanism, we used a simple Higgs-Portal set-up and a fermionic DM particle. However, we insist on the fact that our prescription to search for complementary probes of new physics with laboratory and Gravitational Wave experiments is very general and can be applied to many other DM scenarios that involve a non-standard cosmology [11,25,80,[190][191][192][193][194]. Following this prescription, we believe that many realizations of non-thermal DM production in the early universe may lead to unique predictions of GW spectral shapes that can be detected in future GW experiments and searched for experimentally in laboratories.…”

“…In order to avoid these possibilities, we used a modified version of the code developed by the authors of refs. [80,81] to estimate the amount of dark matter produced out of equilibrium via two-to-two processes. When the reheaton decays and reheats the Universe, it may as well be possible that the reheating temperature exceeds the reheaton mass and lead him to be close from thermalizing.…”

Light Scalars at FASER

“…Light LLPs with mass a few GeV or lighter are predicted in many new physics scenarios [46][47][48][49][50][51], in particular, those involve dark matter [52][53][54][55][56][57][58], hidden valley [59,60], dark photon [61][62][63][64], axion-like particles [65][66][67][68] or heavy neutral leptons [69][70][71][72][73][74]. There are several undergoing and proposed experiments for light LLPs searches, including Belle-II [75][76][77], FNAL-µ [78,79], HPS [80][81][82], NA62 [83,84], NA64 [85][86][87][88], NA64 ++ e [89], NA64 µ [90], SeaQuest [91,92], SpinQuest/DarkQuest [93]…”