ND280 TPC contribution to recent T2K results

Abstract

The T2K (Tokai to Kamioka) experiment is a long baseline neutrino oscillation experiment designed to measure the θ13 neutrino mixing parameter by looking for the appearance of νe in an almost pure νμ beam. The concurrent measurement of νμ disappearance allows refined measurements of the atmospheric Δm2 and of the θ23 mixing parameters.A neutrino beam is produced at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai, Japan, and aimed at 2.5° off the direction of the Super-Kamiokande (SK) detector, 295 km away. The resulting narrow energy band neutrino beam at the SK location, peaked at about 600 MeV, is optimized to maximize the probability of oscillation at the atmospheric Δm2 scale, minimizing at the same time the backgrounds for νe searches. The neutrino beam is monitored before the oscillation by a Near Detector, ND280 located at J-PARC at 280 m from the target. A key element of the T2K Near Detector is composed of three large TPCs instrumented with MicroMEGAS detectors used to measure the neutrino spectrum and flavor composition before the oscillation. The charge and momentum of the charged particles crossing the TPCs are reconstructed, as well as the ionization energy loss in the TPCs allowing to distinguish electrons from muons.T2K has successfully operated since January 2010, and it has presently been paused due to the recent earthquake in Japan. Results on the search for νe appearance and of νμ disappearance have been presented in this talk, particularly stressing the inputs to these measurements from the TPCs.