Probing Sterile Neutrinos with cosmology, astrophysics and...

By Marco Cirelli, Yale University

The conversion into a pure sterile neutrino is nowadays excluded as dominant solution for the solar or atmospheric neutrino oscillations. So sterile neutrinos, that are interesting for many other reasons, have now become even more elusive. The present relevant questions are: which subdominant role can they have? Where can they show up? And how can we see signatures of their presence? With the most general scenarios in mind, I present some selected parts of a recent analysis (hep-ph/0403158) in which we explore (and combine together) all possible sterile effects in cosmology (BBN, CMB, LSS), astrophysics (the Sun, SN...) and terrestrial neutrino experiments. I show how we find no evidence for a sterile neutrino in the present data, identify the still allowed regions and study the signals in the most promising future probes. I show how the region of the LSND sterile neutrino is excluded by the constraints of standard cosmology.