Experimental observation of neutrino flavour transformation:
As reported in Physical Review Letters (2014) as an Editor's Suggestion and since then cited almost 600 times, the T2K experiment for the first time experimentally observed neutrino flavour transformation. Muon neutrinos were produced at the J-PARC facility on Japan's east coast and sent 295 km through the ground to the Super-Kamiokande (SK) neutrino detector in western Japan. SK recorded a decreased number of muon neutrinos and the appearance of electron neutrinos, demonstrating flavour transformation. The discovery of an explicit oscillation confirms the neutrino oscillation mechanism (first observed with solar neutrinos) and opens the door to the use of neutrino oscillation as a probe of CP symmetry violation in leptons.