Phenomenology of the generalised scotogenic model with fermionic dark matter

Abstract

We study a simple extension of the Standard Model that accounts for neutrino masses and dark matter. The Standard Model is augmented by two Higgs doublets and one Dirac singlet fermion, all charged under a new dark global symmetry. It is a generalised version of the Scotogenic Model with Dirac fermion dark matter. Masses for two neutrinos are generated radiatively at one-loop level. We study the case where the singlet fermion constitutes the dark matter of the Universe. We study in depth the phenomenology of the model, in particular the complementarity between dark matter direct detection and charged lepton flavour violation observables. Due to the strong limits from the latter, dark matter annihilations are suppressed and the relic abundance is set by coannihilations with (and annihilations of) the new scalars if the latter and the Dirac fermion are sufficiently degenerate in mass. We discuss how different ratios of charged lepton flavour violating processes can be used to test the model. We also discuss the detection prospects of the charged scalars at colliders. In some cases these leave ionising tracks and in others have prompt decays, depending on the flavour in the final state and neutrino mass orderings.

Dark matter direct detection of a fermionic singlet at one loop

“…In this work we have studied the case of a fermionic singlet DM ψ, which is a simple scenario where DD is naturally induced at one-loop order. The type of scenario considered appears in supersymmetric extensions where the neutralino is pure bino [15] (notice that in this case its mass is typically very heavy, larger than 2 TeV), and also in connection to neutrino masses, in particular in the seesaw model [13] and in some radiative neutrino mass models [8,9,12,80]. We have considered a simplified scenario with a dark sector made of a vector-like (or a SM) fermion and a (complex) scalar.…”

“…In the absence of one of these couplings DD limits are stronger above a certain DM mass given by the experimental energy thresholds of the DD experiments. In some cases the same particles entering in the DD loop may naturally violate lepton number (specially if the DM couples to the left-handed lepton doublets) and give rise to radiative neutrino mass models such as the scotogenic model with Majorana DM [9] or the generalized scotogenic model with Dirac DM [80].…”

Neutrino portals to dark matter

“…Direct detection of a SM singlet fermion DM candidate at one loop has been recently studied in detail in [94]. Moreover, an interesting example, which also provides radiative generation of neutrino masses, has been presented in [95]. The most stringent constraint on DM-nucleon spin-independent cross section for m χ 10 GeV comes from XENON1T [68].…”

Bound-state dark matter with Majorana neutrinos

“…) and the SU(3) c color factor N c is assumed to be 8, since the new particles running in the loop transform as octets. Note that the effective one-loop induced neutrino mass matrix has in general rank two, implying two non-vanishing neutrino masses (similar general structure occurs also in non-colored models [12][13][14]), as required to account for neutrino oscillation data.…”