Bi-maximal neutrino mixing in the MSSM with a single right-handed neutrino

We discuss neutrino masses in the framework of a minimal extension of the minimal supersymmetric standard model (MSSM) consisting of an additional single right-handed neutrino superfield N with a heavy Majorana mass M, which induces a single light see-saw mass mν3 leaving two neutrinos massless at tree-level. This trivial extension to the MSSM may account for the atomospheric neutrino data via νμ→ντ oscillations by assuming a near maximal mixing angle θ23∼π/4 and taking Δm232∼mν32∼2.5×10−3 eV2. In order to account for the solar neutrino data we appeal to one-loop radiative corrections involving internal loops of SUSY particles, which we show can naturally generate an additional light neutrino mass mν2∼10−5 eV again with near maximal mixing angle θ12∼π/4. The resulting scheme corresponds to so-called “bi-maximal” neutrino mixing involving “just-so” solar oscillations. We predict that the decay τ→eγ should be observed in the near future.