We have been developing a positron timing counter for the MEG II experiment which aims to search for $\mu^{+} \rightarrow e^{+} \gamma$ decay with an unprecedented sensitivity. It is expected to have an ultimate time resolution of $\sim$30 ps in the high rate environment of the MEG II experiment. We employed a “pixelated” design with $\sim$500 small counters, each of which is based on a fast plastic scintillator plate readout by multiple SiPMs connected in series. This SiPM readout scheme provides a sharp signal waveform and a maximum light collection and thus, a good time resolution of each counter. Furthermore the overall time resolution can be significantly improved by simultaneous multiple timing measurements with several counters. We performed beam tests with a prototype detector and achieved an excellent overall time resolution of $\sim$35ps. In this talk the design and performance of the pixelated timing counter will be presented

The University of Tokyo

INFN Pavia, Dipartimento di Fisicà dell’Università di Pavia, INFN Genova, Universitá degli Studi di Genova