Sterile neutrinos and the solar mixing

Neutrino mixing matrix appears to be close to bimaximal mixing, but for the solar angle which is definitively smaller than 45 degrees. Whereas it seems quite easy to understand bimaximal mixings, as in models using Le - Lμ - Lτ global symmetries, understanding the 12 degrees of deviation in the observed solar angle seems less simple. We suggest that such a deviation could be due to a light sterile neutrino that mixes with the active sector. The mass scale needed to produce the effect is shown to be smaller than atmospheric scale, and thus, irrelevant for LSND. © 2006 American Institute of Physics.