Non-zero U_(e3) in the Presence of eV Scale Sterile Neutrino

摘要

51.1 Introduction Recent anomalies at short baselines hint towards the existence of one or more sterile neutrinos at the eV scale or even higher. The evidence for {formula} appearance in the LSND experiment [1], subsequently, confirmed by the MiniBooNE experiment [2] along with reactor {formula} fluxes [3] is compatible with one or more extra sterile neutrinos at the eV scale. The hints for the presence of sterile neutrinos come, also, from Big Bang nucleosynthesis (BBN) and the structure of the universe. However, adding light sterile species would result in tension with the cosmological bounds. This conflict can be resolved if eV scale sterile neutrinos are partially thermalized before BBN era but equilibrate with active neutrinos at a later time. Harrison, Perkins and Scott first showed that experimentally obtained mixing matrix is close to the so-called tribimaximal (TBM) mixing [4]. In the present work, we attempt to generate deviations from the TBM mixing while keeping one of the columns of TBM fixed by incorporating sterile neutrinos to the known active neutrino spectrum. We impose the additional constraint of CP-conservation to simplify the analysis. The present work allows non-trivial mixing between active and sterile neutrinos.