Design of the positron tracking detector for the muon g − 2/EDM experiment at J-PARC

The muon anomalous magnetic moment (g − 2) has been measured with a precision of 0.54 ppm, which had 3.3σ discrepancy between the SM prediction and measured value. The muon electric dipole moment (EDM) has been constrained down to 10^-19 e·cm. The muon g − 2/EDM experiment at J-PARC (E34) aims to measure muon g − 2 with a precision of 0.1 ppm, and search for muon EDM with sensitivity down to 10^-21 e·cm. In this experiment, muon is accelerated to the 300 MeV/c and injected to the storage ring that has a 3 T precise magnetic field. We plan to measure a track of a decay positron by a highly-segmented positron tracking detector. The tracker is required to have high rate capability, high stability against a large rate change, good operation in a high magnetic field, and good position resolution. The silicon strip sensor is useful for our experiment. To satisfy these requirements, optimization of the sensor specification and precise alignment are necessary. First, we optimized the sensor specification by considering rate capability by the simulation study. Second, the requirement of alignment accuracy was estimated, and we confirmed that alignment accuracy has to be better than 0.01 mrad. Then, we produced two types of test sensors based on the specification and evaluated the fundamental performance. Signal to noise ratio was estimated when sensor was connected to the readout ASIC developed by ourselves (SlitA). We confirmed that signal to noise ratio satisfied the requirement of SN > 15. (author)