The OPERA experiment has a new paper presenting new results on tau neutrino appearance at the CNGS beam. They have reduced backgrounds a bit more and have found a new candidate tau neutrino event. According to them, this now brings their statistical significance to the 5-σ level. In high energy physics, this is usually where a measurement is said to have discovered something. While tau neutrinos themselves have already been discovered, this would be the first measurement of tau neutrino appearance at the CNGS beam to reach that threshold. Tau neutrinos are probably the most difficult particle to find out of all of the particles of the Standard Model. The Higgs took longer to find but is now much better understood. The tau neutrino remains incredibly difficult to measure.
The CNGS beam is a high energy neutrino beam aimed from the accelerator facility at CERN toward the Gran Sasso laboratory in central Italy.