Study of Charge Integration Electronics in Pi-Zero Detector of a Long-Baseline Neutrino Oscillation Experiment

The Pi-Zero Detector (P0D), a part of Long Baseline Neutrino Oscillation experiment, uses a beam produced and characterized in Tokai, Japan and measured 295 km away in Kamioka. The P0D consists of around 10,000 scintillator bars with wavelength-shifting fibers attached to a Multi-Pixel Photon Counter that measures the energy deposited by neutrino interactions in the bar. The charge output from each photon counter is integrated during a few hundred nanoseconds windows, stamped with hit time, and then read out into a data acquisition system. We also use a Light Injection system to introduce a controlled amount of light into the fibers by pulsing a set of LEDs. Here we present a study of the signals measured in a sequence of integration windows from individual photon counters as well as distributions of hit times. Our results indicate a substantial effect for integration windows following a large signal and demonstrate the need to have further studies of integration electronics so we can eliminate possible effects of background to the interaction signals.