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Exploring physics beyond the standard model: Neutrinos, dark matter, and lepton magnetic moments

Padmanabhan Kovilakam, Vishnu
In this dissertation, we address some of the important limitations of the Standard Model (SM) of particle physics. For this, we have developed novel new physics scenarios and studied their phenomenological implications in various experiments. The primary focus of this dissertation is neutrino physics, dark matter, and lepton magnetic moments. In the context of neutrino physics, the main attention has been given to Dirac neutrino mass models. In this context, we have developed two different frameworks based on abelian gauge extensions of the SM that could address the tiny masses of Dirac neutrinos. The models based on the right-handed abelian gauge extension of the SM have sizeable contributions to Left-Right asymmetry that can be tested at the colliders. In the context of dark matter (DM), we proposed a minimal UV-complete model for sub-GeV thermal DM candidates. In addition to the DM particle, this model required only a second Higgs doublet, which provided a light mediator for DM annihilation. In the last part of this dissertation, we studied various new physics interpretations of experimental anomalies, such as lepton magnetic moment anomalies and W-boson mass shift reported by the Fermilab CDF collaboration. We explored the two-Higgs-doublet model (2HDM) and various neutrino mass models to resolve these anomalies. In the context of 2HDM, anomalies related to electron and muon g-2 can be simultaneously explained with the aid of a light-neutral scalar emerging from the second Higgs doublet. We discussed the prospects of discovering such light scalars in various experiments. We also demonstrated an interesting correlation between the W- boson mass shift observed by the CDF collaboration and the muon g-2 anomaly within the context of the 2HDM. The entire parameter space of this framework can be tested at the LHC. In addition to these studies, we analyzed the correlation between muon g-2 and neutrino transition magnetic moments in the context of a horizontal symmetry model. We found that if the contribution to neutrino magnetic moment is large in this model, then there is no freedom to control the sign and the strength of the muon g-2 contributions.