Non-unitarity of the Leptonic Mixing Matrix in the Low-scale Type-I Seesaw Model

by Christoph Popa (Department of Theoretical Physics, KTH)

Friday 17 Sept 2010, 10:15 → 11:00 Europe/Stockholm

A4:1069

In this work, we study the non-unitarity effects from the realistic low-scale type-I seesaw model. We begin by giving an outline of the Standard Model (SM), followed by the history of neutrino physics and neutrino oscillations in particular. We then present the current knowledge on neutrinos and explore the theory of neutrino oscillations in detail. Subsequently, we discuss the possibilities of extending the SM in order to include massive neutrinos and present the type-I seesaw model, wherein heavy right-handed neutrinos are added to the SM particle content. We show that within an effective low-energy theory, the physics effects of right-handed neutrinos manifest themselves in non-unitary leptonic flavor mixing, and explore the resulting effects on neutrino oscillation probabilities. Working within the framework of the realistic low-scale type-I seesaw model in which the light neutrino masses are protected by structural cancellations among the contributions from different righthanded neutrinos, we show that there exist non-trivial correlations among the non-unitarity parameters. We demonstrate that the six non-unitarity parameters are related to three model parameters, and that the widely studied parameters \eta_{e \tau} and \eta_{\mu \tau} cannot simultaneously be phenomenologically significant.