The Physics Program of MUSE*

The MUon Scattering Experiment (MUSE) at the Paul Scherrer Institute (PSI) seeks primarily to address the proton radius puzzle via investigation of the proton charge radius by performing simultaneous high-precision measurements of elastic electron-proton and muon-proton scattering. Measurements of the proton charge radius will be obtained from a beam of both positively and negatively charged particles from a mixture of electrons, muons, and pions. The experiment runs at varying momenta of 115, 160, and 210 MeV/c. The unique setup of muse allows for a direct muon/electron scattering comparison, a low-Q² region for sensitivity to the proton charge radius (with Q² = 0.002 to 0.082 GeV² /c² ), and for the study of possible two-photon exchange mechanisms.