A new viable mass region of Dark matter and Dirac neutrino mass generation in a scotogenic extension of SM

We propose a scotogenic extension of the Standard Model which can provide a scalar Dark Matter candidate in the new, theoretically previously unaddressed, intermediate region ($200\leq M_{DM}\leq 550$ GeV) and also generate light Dirac neutrino masses. In this framework, the standard model is extended by three gauge singlet fermions, two singlet scalar fields, and one additional scalar doublet, all of which are odd under $Z_{2} \times Z_{4}$ discrete symmetry. These additional symmetries prevent the singlet fermions from obtaining Majorana mass terms along with providing the stability to the dark matter candidate. It is known that in the case of the scalar singlet DM model, the only region which is not yet excluded is a narrow region close to the Higgs resonance $m_{S} \simeq\frac{m_{h}}{2}$ - others ruled out from different experimental and theoretical bounds. In the case of the Inert doublet model, the mass region ($\sim 60$-$80$ GeV) and the high mass region (heavier than $ 550 $ GeV) are allowed. This motivates us to explore a parameter range in the intermediate-mass region $M_{W}\leq M_{DM}\leq 550 $ GeV, which we do in a scotogenic extension of SM with a scalar doublet and scalar singlets. The dark matter in our model is a mixture of singlet and doublet scalars. We constrain the allowed parameter space of the model using Planck bound on present dark matter relic abundance, neutrino mass, and the latest bound on spin-independent DM-nucleon scattering cross-section from XENON1T experiment. Our model may provide a viable DM candidate in the new, previously unexplored mass range ($200\leq M_{DM}\leq 550$ GeV), if this new window for the DM candidate mass is detected in future experiments, along with explanation of Dirac mass of neutrinos, since so far there is no strong evidence in support of Majorana nature of neutrino mass.