Fermionic singlet dark matter in one-loop solutions to the RK anomaly: a systematic study

We study the dark matter phenomenology of Standard Model extensions addressing the reported anomaly in the R-K observable at one-loop. The article covers the case of fermionic singlet DM coupling leptophilically, quarkphilically or amphiphilically to the SM. The setup utilizes a large coupling of the new particle content to the second lepton generation to explain the R-K anomaly, which in return tends to diminish the dark matter relic density. Further, dark matter direct detection experiments provide stringent bounds even in cases where the dark matter candidate only contributes a small fraction of the observed dark matter energy density. In fact, direct detection rules out all considered models as an explanation for the R-K anomaly in the case of Dirac dark matter. Conversely, for Majorana dark matter, the R-K anomaly can be addressed in agreement with direct detection in coannihilation scenarios. For leptophilic dark matter this region only exists for M-DM less than or similar to 1000 GeV and dark matter is under-abundant. Quarkphilic and amphiphilic scenarios even provide narrow regions of parameter space where the observed relic density can be reproduced while offering an explanation to R-K in agreement with direct detection experiments.

Automated summary

The study focuses on dark matter phenomenology in Standard Model extensions, specifically in the context of fermionic singlet dark matter coupling to leptons, quarks, or both, to explain the reported anomaly in the R-K observable. Large couplings between new particle content and the second lepton generation are used to address the R-K anomaly, which leads to a decrease in dark matter relic density. Direct detection experiments impose stringent bounds, even when the dark matter candidate only contributes a small fraction of the observed dark matter energy density.