Design and test of the calibration system of the MEGII Pixelated Timing Counter

The MEG II experiment (Baldini et al., 2018) [1] is designed to improve the sensitivity to the μ +→e + γ decay. A crucial component is the Pixelated Timing Counter (pTC), dedicated to the measurement of the positron time to reduce the combinatorial background (Cattaneo et al., 2014; Nishimura et al., 2016) [3,4]. The detector consists of 512 scintillation counters, each performing a precise measurement of the positron crossing time. This approach requires that the time offsets of the counters are calibrated and regularly monitored over the lifetime of the experiment. The pTC time calibration and monitor system will use a laser diode to deliver pulses to each pixel. The system components have been tested in laboratory, the results demonstrate that a calibration and monitoring resolution satisfying the requirements is within reach.