Abstract
We demonstrate that in a class of the $U(1)'$ extension of the Standard Model (SM), under which all the Standard Model matter fields are uncharged and the additional neutral gauge boson $Z'$ couples to a set of heavy nonstandard fermions, dark matter (DM) production mediated by $Z'$ can proceed through the generation of generalized Chern-Simons (GCS) couplings. The origin of the GCS terms is intimately connected to the cancellation of gauge anomalies. We show that the DM production cross section triggered by GCS couplings is sufficient even for an intermediate scale $Z'$ . A large range of DM and Z masses is then allowed for reasonably high reheating temperature ($T_\rh \gtrsim 10^{10}~\text{GeV}$). This type of scenario opens up a new paradigm for unified models. We also study the UV completion of such effective field theory constructions, augmenting it by a heavy fermionic spectrum. The latter, when integrated out, generates the GCS-like terms and provides a new portal to the dark sector. The presence of a number of derivative couplings in the GCS-like operators induces a high temperature dependence to the DM production rate. The mechanism has novel consequences and leads to a new reheating dependence of the relic abundance.
Highlights
In spite of a lot of speculations about its origin, dark matter (DM) still remains an enigma, and the best we can do is to assume that it has a particle physics origin in the domain of natural extensions of the Standard Model (SM)
We demonstrate that in a class of the Uð1Þ0 extension of the Standard Model (SM), under which all the Standard Model matter fields are uncharged and the additional neutral gauge boson Z0 couples to a set of heavy nonstandard fermions, dark matter (DM) production mediated by Z0 can proceed through the generation of generalized Chern-Simons (GCS) couplings
We have shown that a dark massive Z0, not charged under the SM gauge group, can successfully play the role of a mediator between the visible and the dark sectors even if the corresponding Uð1Þ0 breaking scale lies far above the maximum temperature of the Universe
Summary
In spite of a lot of speculations about its origin, dark matter (DM) still remains an enigma, and the best we can do is to assume that it has a particle physics origin in the domain of natural extensions of the Standard Model (SM). The twin pressure of the clear existence of DM in the energy budget of the Universe [1] and simultaneously the lack of any DM signal in direct detection experiments XENON [2], LUX [3], and PANDAX [4] pushes the limits on weakly interacting massive particles (WIMPs) toward unnatural corners of the parameter space The simplest extensions such as the Higgs portal [5], Z portal [6], or even Z0 portal [7] are severely constrained To generate the effective interaction of the associated gauge boson Z0 with the SM fields, we would need a set of nonstandard fermions charged under Uð1Þ0 as well as under the SM gauge group(s) Such a setup is quite common in string constructions, or in E6 models. We conclude, highlighting the new aspects that emerged from our analysis
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