T2K Experiment finds first indication of muon to electron neutrino oscillation

15 June 2011

The T2K experiment, whose primary purpose is to study neutrino interactions at a large distance from their source, has detected 6 electron neutrino candidate events based on the data collected before March 11, 2011. For the first time, it was possible to observe an indication that muon neutrinos are able to transform into electron neutrinos over a distance of 295 km through the quantum mechanical phenomena of neutrino flavor oscillations.

The picture shows one of the electron neutrino events. In this projected diagram of the cylinder-shaped Super-Kamiokande detector, each colored dot shows a photomultiplier that detected light (these photomultipliers are mounted on the inside wall of the detector). Electron neutrinos interact with water in the detector to produce electrons, which subsequently induce electromagnetic showers to eventually emit Cherenkov light that is detected as a ring-shaped structure.

The Oxford group in T2K has provided part of the DAQ system for one of the detector complexes and is actively involved in the data analysis. The experiment, which is located in Japan, stopped taking data after the March earthquake. Dr. Alfons Weber is quite excited about the new result: "We have worked hard building the experiment for many years. This is an early exciting indication that our efforts are paying off. It is now important to get the detector running again a.s.a.p. and to take more data so that this strong hint becomes into a science fact."

The press release of the host laboratory KEK can be found here. The news from UK funding agency STFC is here. The paper publishing the results has been submitted to PRL.