Research and development of a muon entrance trigger for the muEDM experiment at PSI

Abstract

The muEDM experiment at the Paul Scherrer Institute (PSI) in Switzerland aims to probe the muon electric dipole moment (EDM) using the frozen-spin technique in a compact storage ring, with a sensitivity of $6\times {10}^{-23}$ e⋅cm. A fast entrance detector is expected to work in concert with a magnetic pulse generator to direct muons into the desired orbit. Simultaneously, the entrance detector is designed to veto muons that exceed the apparatus's admittance without introducing significant multiple scatterings. We developed a prototype entrance trigger detector consisting of a thin scintillator for detecting incoming muons and four wall scintillators as veto detectors. The prototype was tested at 27.5 MeV/c at the πE1 beamline at PSI. A total of $7\times {10}^5$ events were collected, which were read out by SiPMs coupled to the plastic scintillators under two different beam tunes. These events were analyzed to characterize the detector's performance, which was also cross-checked with Monte Carlo simulations that took into account the beam phase space and scintillation processes.