Physics beyond the standard model, LHC, and cosmology

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dc.contributor.advisor Sarkar, Utpal
dc.contributor.advisor Mahajan, Namit Hati, Chandan 2017-10-18T05:35:07Z 2017-10-18T05:35:07Z 2016
dc.identifier.citation Hati, Chandan (2016). Physics beyond the standard model, LHC, and cosmology (PhD. Dissertation). Indian Institute of Technology, Gandhinagar, pp. 137 (Acc No: T00218) en_US
dc.description.abstract The Standard Model (SM) of particle physics has been highly successful in explaining most of the experimental measurements in elementary particle physics. It has survived decades of precision tests at highest available energies and with the discovery of the Higgs boson in 2012 at the Large Hadron Collider (LHC) the last missing piece of the SM was confirmed. However, the SM suffers from a number of shortcomings, which strongly suggest that the SM is only an effective limit of a more fundamental theory of interactions. The aim of this thesis is to study various aspects of the physics beyond the SM ranging from the phenomenological implications of viable models to cosmological implications such as the matter-antimatter asymmetry of the universe, dark matter, and dark energy. In this thesis we study several models beyond the SM in the contexts of LHC phenomenology, neutrino masses, flavor anomalies associated with B-decays and gauge coupling unification. We also study the possibilities of explaining the matter-antimatter asymmetry via baryogenesis (leptogenesis) mechanisms in these models. We also touch upon the issues of potential candidates for dark matter and the realization of dark energy in models beyond the SM. We study the implications of a right handed charged gauge boson W R with mass of around a few TeV for leptogenesis. We point out how the discovery of a TeV scale W R will rule out all possibilities of leptogenesis in all classes of the left-right symmetric extensions of the SM due to the unavoidable fast gauge mediated B ?? L violating interactions. We also study the framework of LRSM with additional scalar singlets and vector-like fermions in the context of the recent LHC excess signals and the phenomenological implications for the fermion masses and mixing. We also discuss how the introduction of a real bi-triplet scalar, which contains a potential DM candidate, can allow gauge coupling unification. Furthermore, we point out that the existence of new vector-like fermions can also have interesting implications for baryogenesis and the dark matter sector. The effective low energy left-right symmetric subgroups of the superstring inspired E6 model provide a rich phenomenology, thanks to many additional exotic fields including leptoquarks. We systematically study these low energy subgroups in the context of the LHC excess signals reported by the CMS collaboration, and high scale leptogenesis. We also study the left-right symmetric low energy subgroups of E6 in the context of recent experimental results from the LHCb, BaBar and Belle collaborations on the decays of the B mesons: B ! D( ) and B ! Kll, showing significant deviations from the SM, which hint towards a new physics scenario beyond the SM. We use the leptonic decays D+ s ! + , B+ ! + , D+ ! + and D0- D0 mixing to constrain the couplings involved in explaining the enhanced B decay rates. We also study the E6 motivated U(1)N extension of the supersymmetric SM in the context of the LHC excess signals and the baryon asymmetry of the universe. In light of the hint, from short-baseline neutrino experiments, of the existence of one or more light sterile neutrinos, we also study the neutrino mass matrices, which are dictated by the discrete symmetries in the variants of this model. We study a cogenesis mechanism in which the observed baryon asymmetry of the universe and the dark matter abundance can be produced simultaneously at a low reheating temperature without violating baryon number in the fundamental interactions. This mechanism can also provide a natural solution for the cosmic coincidence problem. We also present a realization of mass varying neutrino dark energy in two simple extensions of the SM, where the SM is extended to include new TeV scale triplet scalars and fermions, respectively. We also discuss the possible leptogenesis mechanisms for simultaneously generating the observed baryon asymmetry of the universe in both the scenarios and the collider signatures for the new TeV scale fields. en_US
dc.description.statementofresponsibility by Chandan Hati
dc.format.extent 137 p.; 29 cm.
dc.language.iso en_US en_US
dc.publisher Indian Institute of Technology Gandhinagar en_US
dc.title Physics beyond the standard model, LHC, and cosmology en_US
dc.type Thesis en_US
dc.contributor.department Physics Ph.D.

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