An Updated Numerical Analysis of eV Seesaw with Four Generations

Abstract

We consider the so-called "eV seesaw" scenario, with right-handed Majorana mass $M_R$ at eV order, extended to four lepton generations. The fourth generation gives a heavy pseudo-Dirac neutral lepton, which largely decouples from other generations and is relatively stable. The framework naturally gives 3 active and 3 sterile neutrinos. We update a previous numerical analysis of a 3+3 study of the LSND anomaly, taking into account the more recent results from the MiniBooNE experiment. In particular, we study the implications for the third mixing angle $\mathrm{sin}^2\theta_{13}$, as well as CP violation. We find that current data do not seriously constrain more than one sterile neutrinos.