Exploring new physics beyond the standard model

In the study under investigation in this thesis, we explore the possibility of one of the new physics beyond standard model namely, the Scotogenic model to account for the observed relic density of dark matter in our Universe while respecting all imposed constraints on its parameter space. The Scotogenic model is one of the simplest extensions of the standard model that can provide a mechanism for light neutrino mass generation and can provide a candidate for dark matter. The Scotogenic model was introduced by Ernest Ma in 2006 (Ma 2006). Within framework of the model, three singlet right-handed Majorana fermions, N_1,2,3, are introduced. The lightest among these new fermions, N_1, was considered to be a candidate of dark matter. The annihilations of N_1 N ̅_1 can result in final states with two standard model particles. Specifically, these final states are ℓ+ ℓ- and ν ν where ℓ represents a charged lepton and ν denotes a neutrino. The cross sections of these final states contribute to the relic density of dark matter. However, it turns out that it is difficult to account for the measured value of the relic density of the Dark Matter while respecting the strong constraint from the process μ → eγ. It should be noted that an alternative scenario can be considered to overcome this difficulty. In this alternative scenario, which is taken into account in this thesis, one assumes that N_1 and N_2 are degenerate or nearly degenerate in mass and thus N_1 N ̅_2 and N_2 N ̅_2 annihilations into ℓ+ ℓ-, ν ν will contribute also to the relic density of dark matter. In this work, we will analyze the effect of the latest findings related to neutrino oscillations, dark matter direct detection experiments, the bound from branching ratio of the process μ → eγ and the Planck measurement of the relic density of dark matter on the parameters of the Scotogenic model. We will show the effect of each individual constraint on the parameter space of the Scotogenic model and the effect of imposing these constraints together on the parameter space. We will show that it is possible to account for the observed relic density of dark matter within 2σ range of its measured value by Planck satellite while respecting all the imposed constraints for Dark Matter masses close to 1 TeV.