Credit:
The first T2K event seen in Super-Kamiokande. Each dot is a PMT which has detected light. The two circles of hits indicate that a neutrino has produced a particle called a 0, perfectly in time with the arrival of a pulse of neutrinos from J-PARC. Another faint circle surrounds the viewpoint of this image, probably made by the low-energy muon created directly by the neutrino.