New results from the T2K neutrino oscillation experiment

The T2K experiment searches for the appearance of electron neutrinos in a muon neutrino beam. The rate of this process is sensitive to the neutrino mixing parameter θ13. Recent measurements that θ13 ≠ 0 imply that νμ → νe oscillations should be observable. Using all data through May 15, 2012 the T2K experiment has detected 10 candidate νe events, with an expected background for θ13 = 0 of 2.73±0.37 events. This 3.2σ excess of νe events is the strongest indication to date for appearance of electron neutrinos in a neutrino oscillation experiment, and for normal mass hierarchy and δCP = 0 yields 0.059 < sin2 2θ13 < 0.164 at the 68 % C.L.