Z′ mediated WIMPs: dead, dying, or soon to be detected?

Abstract

Although weakly interacting massive particles (WIMPs) have long been among the most studied and theoretically attractive classes of candidates for the dark matter of our universe, the lack of their detection in direct detection and collider experiments has begun to dampen enthusiasm for this paradigm. In this study, we set out to appraise the status of the WIMP paradigm, focusing on the case of dark matter candidates that interact with the Standard Model through a new gauge boson. After considering a wide range of Z′ mediated dark matter models, we quantitatively evaluate the fraction of the parameter space that has been excluded by existing experiments, and that is projected to fall within the reach of future direct detection experiments. Despite the existence of stringent constraints, we find that a sizable fraction of this parameter space remains viable. More specifically, if the dark matter is a Majorana fermion, we find that an order one fraction of the parameter space is in many cases untested by current experiments. Future direct detection experiments with sensitivity near the irreducible neutrino floor will be able to test a significant fraction of the currently viable parameter space, providing considerable motivation for the next generation of direct detection experiments.

Refined bounds on MeV-scale thermal dark sectors from BBN and the CMB

“…This is done by computing the background cosmology externally using NUDEC BSM [103,104] and then passing on the relevant parameters 2 to the section of PRIMAT that takes care of the The grey contours correspond to the mean ± 2σ measurements that enter our BBN and Planck data analyses, see Eqs. (13), (14) and (15).…”

“…In this work, we will combine BBN+CMB data in two ways: i) by constructing a joint χ 2 that is obtained by summing the individual Planck and BBN χ 2 's as defined in Eqs. (13) and (14) (labelled BBN+Planck across the paper) and ii) by adding to χ 2 BBN a measurement of Ω b h 2 = 0.02225 ± 0.00066, which is to be regarded as a cosmological model-independent Planck determination of the baryon energy density 5 (we shall call this analysis BBN+Ω b h 2 ). See Appendix C for details.…”

“…Left panels: Impact of a non-standard neutrino decoupling temperature on the cosmological observables N eff , YP and D/H|P. The YP and D/H|P predictions are computed with Ω b h 2 = 0.021875 and τn = 879.5 s. The grey contours correspond to the mean ± 2σ measurements that enter our BBN and Planck data analysis, see Eqs (13),(14). and(15).…”

Dirac neutrino mass generation from a Majorana messenger

“…The scenario where ψ 1 self-annihilates dominantly through h iα -mediated interactions resembles the very well known scotogenic model [18], where sizable h iα are required to reproduce the correct DM abundance, which in turn leads to a mild tension with experimental upper bounds on the rates for rare charged lepton decays [34][35][36]. On the other hand, when the Z portal [37,38] is the main gate to visible sector, ψ 1 largely annihilates into neutrinos in such a way the observed DM abundance can be reproduced without entering in conflict with the DM searches, which follows from the fact that the Z does not couple to quarks and charged leptons (see [38][39][40][41][42] for phenomenological studies on Z -mediated Majorana DM).…”

Interference effects in dilepton resonance searches for Z′ bosons and dark matter mediators

“…Such Z bosons generically appear in many extensions of the SM [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] and are an essential part of Grand Unified Theories. On a more phenomenological level, they have also received substantial attention as the mediator of spin-one simplified models of Dark Matter (DM) [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. These simplified models have been advertised by the LHC DM working group [41,42] in order to explore the complementarity between different LHC analyses and across different DM experiments, which include direct and indirect detection, as well as observations of the DM relic density.…”