New physics in the lepton sector
Mon, Sep. 28th 2015, 14:00
Amphi Claude Bloch, Bât. 774, Orme des Merisiers
This thesis deals with some scenarios of new physics as well as their consequences on the lepton sector. \par The fact that neutrinos are massive is one of the problems left unsolved by the Standard Model.One possible solution is the seesaw mechanism, that involves new heavy states whose decay violateslepton number. Because of this, these states can participate in leptogenesis, one of the scenariosthat could explain the origin of the asymmetry between matter and antimatter in our universe. I will discuss leptogenesis with a scalar triplet, and focus especially on the impact of flavour effects,that have been little considered previously. After introducing a very general scenario, I will present a more specific model that establishes a correlation between leptogenesis and neutrino masses. \par I will then turn to supersymmetric theories. I will describe a model in which the fermionic partner of a pseudo-Goldstone boson, associated to a symmetry broken at high energy, plays the role of a sterile neutrino, that could explain some experimental anomalies.I will compare predictions of the model to current experimental data. \par Finally, to be viable, supersymmetry should be broken in a hidden sector, and this breaking should be transmitted to the fields of the low energy theory. One of the most elegant scenarios for this is gauge mediation. Unfortunately, it cannot easily reproduce the mass of the Higgs boson measured at LHC. Extensions can rehabilitate this scenario by accommodating the Higgs mass $m_h=126$ GeV. I will present a general derivation of supersymmetry-breaking terms and show how the results can be applied to specific models, which include both gauge mediation and the seesaw mechanism.
Contact : lbervas