Radiative neutrino mass with electroweak scale Majorana dark matter in the Scotogenic model

Abstract

Non-zero neutrino mass and dark matter (DM) overshadow the success of the Standard Model (SM) of particle physics. The most straightforward extension of the SM to explain these two issues is the Scotogenic model, where the SM particle spectrum extends with three isospin singlet right-handed neutrinos and one doublet scalar, all odd under a Z2 symmetry. The neutrino masses and mixings result from the Weinberg operator induced at one-loop level. The particle spectrum of this model contains a few weakly interacting stable massive particles, each of which can be a good candidate for DM. In this work, we have considered the lightest right-handed neutrino as DM candidate. The Yukawa couplings that give rise to the observed flavor mixings in the neutrino sector also lead to flavor violation in the SM charged lepton sector and hence, get tightly constrained from the charged lepton flavor violating (CLFV) observables. The same Yukawa couplings also contribute to the DM annihilation in the early universe and hence, determine the relic density of the DM. In this work, we address the tension between the constraints from CLFV observables and measured DM relic density to obtain the large Yukawa couplings with the help of a parameterization that reduces the phenomenology relevant parameters to merely three and enhances the detection prospect at the collider experiments. We have explored the parameter space consistent with current CLFV bounds, the observed DM relic density, and the absolute neutrino mass limit. To search for these scenarios, we have identified two promising signals at the proposed lepton colliders: the mono-photon plus missing energy and di-lepton plus missing energy signals. We have studied the collider phenomenology of these signatures and estimated the 5σ detection required luminosity for the center of mass energies at 500 GeV and 1 TeV.