Sharif Digital Repository

One of the most simple questions of particle physics, which is still unanswered, is whether neutrino and antineutrino are the same particles or not. The answer to this question has many implications for the physics beyond the Standard Model, supersymmetric theories and unified theories.
In this thesis we first introduce Majorana fermion, the best candidate for which is neutrino. Then its implications for going beyond the standard Model have been discussed. At present time, the most important experiment which can prove this guess is neutrinoless double beta decay which has been studied in details in this thesis. The study of the theoretical and experimental aspects of neutrinoless double... 

In this thesis, we studied the oscillation of neutrino flavors and the measurement of mixing parameters through the detection of cosmic neutrinos at neutrino telescopes. Most of the astrophysical explosions predict the emission of neutrino flux and kilometer-scale detectors are under construction for the observation of these neutrinos. Detection of astrophysical neutrinos opens a new window to understand the neutrino properties and also the properties of astrophysical sources.In this thesis first we review the phenomenology of neutrino flavor oscillation and characteristics of neutrino mass matrix. By introducing a new class of invariants (under general transformation of lepton fields bases)... 

Today with respect to the particle physics experiments and astrophysical observations we know that Neutrinos are massive. Free streaming of light Neutrinos supresses the density field of matter and opposes gravitational growth, so that clusters formed at fixed mass are fewer and hence more biased than for a pure CDM density field. One way to study the effects of Neutrinos on the formation of large-scale structures is to examine the matter power-spectrum and corellation function in the presence of massive Neutrinos.In the presence of massive Neutrinos, the matter power-spectrum is suppressed in small scales and also correlation function and clustering bias are changed in comparison to the CDM... 

One of the open questions in particle physics and cosmology is matter-antimatter asymmetry in the Universe. Observations at different scales in the early universe indicates that the number of baryons and leptons are greater than the number of anti-baryons and anti-leptons. Various mechanisms in the last 50 years, have been proposed to generate this asymmetry from a symmetric Universe. They can be classified into two groups: models which add new particles and interactions and models which consider gravity and time dependent background fields. The basic difference is that if they respect CPT symmetry or not. In this thesis we take the second approach. We study the neutrino sector of the...