Study of particle physics models with implication for dark matter and cosmic ray phenomenology

Abstract

There are many observations in particle physics and cosmology, which seek physics beyond standard model for their explanation. Some of them are : The excess of positron over cosmic ray background observed by AMS-02 experiment, the 3:6_ discrepancy between muon (g ð€€€ 2) measurement by BNL and its standard model prediction, and the absence of Glashow-resonance in the PeV neutrino events at IceCube. As the thesis title indicates this work is about the study of particle physics models which not only explain the mentioned observations but also give a suitable candidate of dark matter with correct relic density. In the work presented here we have proposed a gauged horizontal symmetry model for which we introduce a 4th generation of fermions into SM. We then introduce a SU(2)HV vector gauge symmetry between the 4th generation leptons and muon families. The 4th generation right-handed neutrino is identi_ed as dark matter which annihilates into leptons _nal state (_+_ð€€€; _c_ __) giving rise to correct relic density. In this model, dark matter is lephtophilic in nature, so it can explain AMS-02 positron excess remaining consistent with stringent bounds from antiproton. It is also possible to alleviate the discrepancy in muon (g ð€€€ 2) from 4th generation charge lepton, SU(2)HV gauge boson, and from neutral and charged scalars. In this way, both the signals, muon (g ð€€€ 2) and the excess of positron can be explained simultaneously. We have also studied an alternative left-right model called dark left-right model, where it is possible to accommodate a suitable dark matter candidate. The second generation right-handed neutrino is identi_ed as dark matter which dominantly annihilates into leptons _nal state. So it is possible to explain AMS-02 positron excess and lift the stringent bounds from antiproton. The singly and doubly charged scalars in dark left-right model also contribute to muon (g ð€€€2) and so both the signatures can also be related in this model. Another part of this thesis deals with the absence of Glashow resonance at Ice-Cube PeV neutrino events. The IceCube collaboration has observed neutrino of very high energy which goes upto _ 3 PeV, but did not see any events at Glashow resonance. The Glashow resonance gives rise to an enhanced cross-section for __e at resonance energy 6.3 PeV which increases the detection rate of __e by a factor of _ 10. This implies that at least some of the events should have been observed at Glashow resonance, but none were. We proposed a new mechanism which can explain why neutrinos arising from astrophysical process may be suppressed. We assume a Lorentz violating higher dimensional operator, which modi_ed dispersion relation of neutrinos (antineutrinos). As a result, pion and kaon decay widths get suppressed and we observe a cuto_ in the neutrino spectrum which is consistent with IceCube data.