Characterization of the 6D Phase Space of a Muon Beam for the Measurement of the Muon Electric Dipole Moment

Abstract

The Universe as we know it has an asymmetry between matter and antimatter (called ‘baryon asymmetry’), a phenomenon which requires CP violation in the laws of physics. Although CP violation is established in the Standard Model, the amount is insufficient to explain the much larger observed asymmetry. As the electric dipole moments (EDMs) of fundamental particles are a source of CP violation any non-zero measurement of the EDMs above the values predicted by the Standard Model would indicate an excess of CP violation in the Universe which could help explain the observed baryon asymmetry. The µEDM experiment at the Paul Scherrer Institute (PSI) aims to measure the muon’s EDM at a greater sensitivity than ever before. The ultimate sensitivity goal, corresponding to |dµ | < 6 × 10−23e.cm, would improve upon the current direct limit of |dµ | < 1.8×10−19e.cm by almost four orders of magnitude, as well as the current indirect limit of |dµ | < 2×10−20e.cm by nearly three orders of magnitude. This thesis describes efforts to characterize the 6-dimensional phase space of the muon beam from the µE1 beamline at PSI, Switzerland for phase 2 of the µEDM experiment. Data was collected using a scintillating fibre array (SciFi) and a LaBr calorimeter, and the modelling of the results was performed using CERN’s Transport simulation software, Python’s XSuite library and G4Beamline software. These models will inform the design of phase 2 and are an important step towards an end-to-end experimental simulation which integrates the beamline and experimental apparatus. The results will also aid any experiments that may make use of the µE1 beamline at PSI in the future.