Lancaster T2K Group

The T2K (Tokai to Kamioka) experiment is a "long-baseline" neutrino experiment which will measure the probability that one type of neutrino will change to another as it traverses the 295 km from Tokai Japan to Kamioka Japan. Lancaster University, along with a group of U.K. universities, was involved in designing and constructing the T2K "near detector" (the ND280) which has the task of characterising the neutrino beam 280 m downstream from where it is produced at Tokai, in order that the properties of the beam can subsequently be compared with those determined by the "far detector", Super Kamiokande at Kamioka.

The T2K Near Detector (ND280), situated 280 m downstream of the neutrino production target, has the task of characterising the muon-neutrino beam before the neutrinos have changed flavour. This beam profile will be compared with the profile measured by the "far detector", Super Kamiokande, 295 km away, in order to determine the oscillation parameters. In addition, it is critical that the ND280 measure the main irreducible backgrounds in the beam so that their presence in Super Kamiokande can be predicted accurately.

The U.K.built the electromagnetic calorimeter (ECal) for the ND280. The ECal is capable of providing both tracking information and particle identification. The Barrel Ecal (Brl-ECal), shown in blue, surrounds the basket, shown in brown, which contains the inner sub-detectors: At the upstream end is the Pi-zero Detector (P0D) which was built in the U.S; followed by the tracker region consisting of the Fine Grain Detectors (FGDs) and the Time Projection Chambers (TPCs) which were built in Canada and Europe; and lastly the most downstream sub-detector, the Downstream Ecal (DS-ECal), which was built at Lancaster University. The DS-ECal will absorb more of the neutrino flux than the other parts of the ECal, and acted as our ECal calibration module. The outermost layers of the ND280 are formed by the iron return yoke (shown in red) of the former UA1 magnet, which is partially instrumented in order to provide trigger information and to veto cosmic ray muons and external backgrounds. The magnet coils, which provide a field of 0.2 T, are shown in green.

The operation of T2K was interruped by the earthquake on 11th March 2011. Luckily no-one was hurt and it is hoped that the detector and accelerator will be operational by early 2012. The data collected before the earthquake have already provided an indication that electron neutrinos are appearing at Kamkioka having started out as muon neutrinos in Tokai.