Aspects in new physics beyond standard model

In particle physics, the Standard Model is considered the most successful theory describing three fundamental forces (electromagnetic force, strong nuclear force and weak nuclear force) in nature. The Standard Model provides a framework for unifying these forces and can explain most phenomena related to these forces. In addition, a significant part of the predictions made within the framework of this model were later confirmed experimentally. However, many important issues in our universe such as neutrino masses, dark matter, the superiority of matter over antimatter and other observations cannot be explained within the framework of the Standard Model. All these can be seen as a hint for the necessity of the presence of new physics extending the Standard Model to resolve some of these issues. In the literature, there are many trials to extend the Standard Model. One of these is the so-called scotogenic model. To test this model, it is crucial to investigate its signature in future colliders. In this thesis, we investigate the process e+e− →H+H− in the framework of the scotogenic model. The scotogenic model has non-standard particles consisting of new scalars and new singlet fermions with at least one of them serving as a dark matter candidate. The process receives different contributions arising from tree-level diagrams mediated by photon exchange, Z boson exchange and N1,2,3 new singlet right-handed fermion exchange. Also, we estimate the size of each contribution and the total crosssection of the process after applying all dominant constraints on the parameters of the model. Besides, we investigate the dependence of cross-section on the centre-of-mass energy for a set of benchmark points of the parameter space of the scotogenic model. We show that the dominant contribution to the cross-section originates from the new singlet right-handed fermions N1,2,3. Additionally, we present the cross-section's dependence on the center-of-mass energy for a set of benchmark points in the model's parameter space that adhere to the robust bounds that were obtained. Here, the parameter space is calculated according to the masses of the first two lightest fermions. Furthermore, the constraints of the dark matter include the relic density and accepts the lightest fermion as a potential candidate for the dark matter. These predictions can be tested in future e+e− colliders and hence can test the validity of the model or set further strong constraints on the model.