The first measurement of muon antineutrino disappearance on the T2K Experiment, performed by Oxford graduate student Kirsty Duffy, was released on 18 May 2015.
T2K (Tokai to Kamioka) is a long-baseline neutrino oscillation experiment in Japan, studying neutrino oscillations and interactions. Researchers from 59 institutes in 11 countries search for oscillations from muon neutrinos to electron neutrinos and tau neutrinos, and study neutrino interactions at the two near detectors (ND280 and INGRID) and the far detector (Super-Kamiokande), 295km away from the initial beam.
Since May 2014, T2K has been running with a beam composed mostly of muon antineutrinos, and 59.8 events would have been detected in T2K's far detector Super-Kamiokande if there were no antineutrino oscillations. However, only 17 events were observed, which matches the expected "disappearance" due to muon antineutrinos oscillating into tau antineutrinos.