New Positron Spectrometer for MEG Experiment Upgrade

Abstract

An upgrade of the MEG experiment, which searches for the lepton flavor violating decay, $\mu \to e\gamma$, at the highest sensitivity ever, is planned in order to improve the sensitivity down to $\sim 5\times {10}^{-14}$. We plan to employ a stereo wire drift chamber with a unique volume for the tracking and a pixelated scintillation detector with silicon photomultiplier (SiPM) readout for the timing measurement with improved efficiency and resolutions. We will describe the expected performance and the R&D status of the new spectrometer especially focusing on the new timing counter, which is expected to contribute better resolution of the relative timing between positron and gamma-ray.