Scalar (fermion) dark matter with mass in the MeV range coupled to ordinary neutrinos and another fermion (scalar) is motivated by scenarios that establish a link between radiatively generated neutrino masses and the dark matter relic density. With s
uch a coupling, cosmic supernova neutrinos, on their way to us, could resonantly interact with the background dark matter particles, giving rise to a dip in their redshift-integrated spectra. Current and future neutrino detectors, such as Super-Kamiokande, LENA and Hyper-Kamiokande, could be able to detect this distortion.
In 2006, a simple extension of the Standard Model was proposed in which neutrinos obtain radiative Majorana masses at one-loop level from their couplings with dark matter, hence the term scotogenic, from the Greek scotos meaning darkness. Here an ana
logous mechanism for Dirac neutrino masses is discussed in a minimal model. In different ranges of the parameter space, various candidates for dark matter are possible. In particular, the lightest Dirac fermion which appears in the loop diagram generating neutrino mass can be a viable dark matter candidate. Such a possibility does not exist for the Majorana case. Realistic neutrino mixing in the context of $A_4$ is discussed. A possible supersymmetric extension is also briefly discussed.
