A brief review of the experimental status of neutrino mixing. The model of neutrino oscillations has now been established with high confidence, with many of the model parameters measured to an accuracy of a few per cent. However, some parameters stil
l remain unknown, notably the mixing angle $theta_{13}$ and the amount of CP violation. Recently, new questions have come to light, highlighting possibilities to search for new physics in the neutrino sector.
This letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for muon antineutrino production, accumulating an exposure of $1.71times 10^{20}$ protons on t
arget. In the Far Detector, 97 charged current muon antineutrino events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at $6.3sigma$. The best fit to oscillation yields $Delta bar{m}^{2}=(3.36^{+0.46}_{-0.40}textrm{(stat.)}pm0.06textrm{(syst.)})times 10^{-3},eV^{2}$, $sin^{2}(2bar{theta})=0.86^{+0.11}_{-0.12}textrm{(stat.)}pm0.01textrm{(syst.)}$. The MINOS muon neutrino and muon antineutrino measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.
