Abstract
As experimental null results increase the pressure on heavy weakly interacting massive particles (WIMPs) as an explanation of thermal dark matter (DM), it seems timely to explore previously overlooked regions of the WIMP parameter space. In this work we extend the minimal gauged $U(1)_{L_\mu-L_\tau}$ model studied in \cite{Bauer:2018onh} by a light (MeV-scale) vector-like fermion $\chi$. Taking into account constraints from cosmology, direct and indirect detection we find that the standard benchmark of $M_V=3 m_\chi$ for DM coupled to a vector mediator is firmly ruled out for unit DM charges. However, exploring the near-resonance region $M_V\gtrsim 2 m_\chi$ we find that this model can simultaneously explain the DM relic abundance $\Omega h^2 =0.12$ and the $(g-2)_\mu$ anomaly. Allowing for small charge hierarchies of $\lesssim\mathcal{O}(10)$, we identify a second window of parameter space in the few-GeV region, where $\chi$ can account for the full DM relic density.
Highlights
The advent of the standard model of particle physics (SM) [1,2,3] was one of the biggest milestones in physics
There are some hints for physics beyond the standard model (BSM), one of the most intriguing ones being the ∼4σ excess of the anomalous muon magnetic moment ðg − 2Þμ measured at the BNL E821 experiment [4,5,6,7]
The upcoming E989 experiment at Fermilab aims at a fourfold improvement in the experimental sensitivity compared to E821 [8] thereby potentially pushing the significance above 5σ, if the excess is due to BSM physics
Summary
The advent of the standard model of particle physics (SM) [1,2,3] was one of the biggest milestones in physics. One such class of models is a dark sector charged under a new secluded Uð1ÞD symmetry that is only coupled to SM particles via kinetic mixing of the associated gauge boson with the SM hypercharge boson [21,22,23,24,25]. While such secluded DM scenarios have been investigated extensively in the past, in this article we study a model where an extra vector-like fermion χ charged under a gauged Uð1ÞLμ−Lτ symmetry is added to the spectrum. In the remainder of this article we will first introduce the model, discuss the various dark matter and hidden photon constraints, before we will present our results and conclude
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