| Neutrino oscillations were discovered in atmospheric and solar neutrinos and have been confirmed by experiments using neutrinos from accelerators and nuclear reactors. It has been found that there are large mixing angles in the nue → numu and numu → nu tau oscillations. The third mixing angle theta13, which parameterizes the mixing between the first and the third generation, is constrained to be small by the CHOOZ reactor experiment. The T2K experiment is a long baseline neutrino oscillation experiment that uses the intense muon neutrino beam produced at J-PARC (Tokai, Japan) and Super-Kamiokande detector at 295 km as the far detector to measure the angle theta13 using the nu e appearance channel. One dominant background to the nue appearance search is the single pi0 from neutral-current interactions. This background will be measured at the near site using the pi 0 detector which was built at Stony Brook. The pi0 measurement requires a high rejection efficiency for backgrounds from charged-current neutrino interactions. We have developed an event reconstruction specialized to reject the charged-current backgrounds while keeping the signal pi 0. This event reconstruction was also used during the detector design phase to study its performance. Finally, we have done the energy calibration of the detector using cosmic ray muons. |
