Muon Neutrino Disappearance and Tau Neutrino Appearance
  Since evidence for neutrino oscillations was first observed in 1998, the study of muon neutrino oscillations has been aggressively pursued. In doing so, atmospheric and accelerator-based neutrino experiments have measured with the highest precision two fundamental neutrino parameters: the mass-square difference and the large mixing angle in the atmospheric neutrino sector. Furthermore, the dominant mode of these oscillations has recently been established to be from muon to tau neutrinos with both direct and indirect observations. Also, for the first time the anti-neutrino counterparts to these oscillation parameters are being studied. While a consistent picture of the mu-tau sector is thus emerging, a new generation of accelerator-based experiments using off-axis neutrino beams to access this sector could lead to new discoveries. 
M. C. Sanchez
hep-ex