Singlet-doublet fermion dark matter with Dirac neutrino mass, $(g-2)_\mu$ and $\Delta N_{\rm eff}$

TL;DR

This paper explores a model where singlet-doublet fermion dark matter and Dirac neutrinos are interconnected, explaining neutrino masses, muon g-2 anomaly, and extra relativistic particles, with testable predictions for future experiments.

Contribution

It introduces a scotogenic mechanism linking dark matter, Dirac neutrino mass, and muon g-2, highlighting correlations and experimental prospects.

Findings

Model explains neutrino masses and muon g-2 simultaneously.

Predicts additional relativistic degrees of freedom detectable by CMB experiments.

Provides detection prospects for dark matter and tests at future CMB observatories.

Abstract

We study the possibility of generating light Dirac neutrino mass via scotogenic mechanism where singlet-doublet fermion dark matter (DM) plays non-trivial role in generating one-loop neutrino mass, anomalous magnetic moment of muon $(g-2)_\mu$ as well as additional relativistic degrees of freedom $\Delta{N_{\rm eff}}$ within reach of cosmic microwave background (CMB) experiments. We show that the Dirac nature of neutrinos can bring interesting correlations within the parameter space satisfying the $\left(g-2\right)_\mu$ anomaly and DM relic density and the effective relativistic degrees of freedom $\Delta{N_{\rm eff}}$. While we stick to thermal singlet doublet DM with promising detection prospects, both thermal and non-thermal origin of $\Delta{N_{\rm eff}}$ have been explored. In addition to detection prospects at DM, $(g-2)$ and other particle physics experiments, the model remains verifiable at future CMB experiments like CMB-S4, SPT-3G.