The T2K $\pi^0$ Detector and Calibration of Novel MPPC Photo Sensors

Neutrino oscillations have been discovered by atmospheric and solar neutrino experiments, then later confirmed by experiments using neutrinos from accelerators and nuclear reactors. The Tokai to Kamioka (T2K) experiment, a long baseline neutrino oscillation experiment, will measure the neutrino mixing angle $\theta_{13}$ via a $\nu_\mu \rightarrow \nu_e$ appearance search. $\theta_{13}$ is the third mixing angle which parameterizes the mixing between the first and third generation, and has not yet been measured. T2K uses an intense neutrino beam produced at J-PARC in Tokai, Japan, a near detector (ND280) at 280 m, and Super Kamiokande as the far detector at 295 km. $\pi^0$ particles make a large contribution to the $\nu_e$ appearance background. For this reason the scintillator based $\pi^0$ detector, a sub-detector of ND280, will measure the $\pi^0$ background. The $\pi^0$ detector uses novel Multi-pixel Photon Counter (MPPC) photo sensors. MPPCs are pixelized silicon devices with $\sim1$mm$^2$ active area, where each pixel is an avalanche photo diode working in Geiger mode. This poster will describe the $\pi^0$ detector and MPPC calibration.