Speaker
Description
The MUon Scattering Experiment (MUSE) at the Paul Scherrer Institute (PSI) is designed to address the "proton radius puzzle" through high-precision measurements of elastic lepton-proton scattering. By utilizing a mixed secondary beam in the $\pi$M1 channel, MUSE performs simultaneous measurements of electron-proton ($e^{\pm}p$), muon-proton ($\mu^{\pm}p$), and pion-proton ($\pi^{\pm}p$) scattering. This multi-lepton approach, covering a low-momentum transfer range of $Q^2 \approx 0.002$ to $0.08$ GeV$^2$, enables a direct test of lepton universality and a determination of the proton charge radius with reduced systematic uncertainties, while the dual-polarity measurements are necessary for two-photon exchange corrections.
In this talk, I will present the current status of the MUSE experiment, the expected sensitivity, and the data analysis, focusing on techniques developed to minimize systematic bias in the extraction of the charge radius. These include high-granularity detector calibration and alignment of the tracking systems, optimized event selection for reaction identification, and data-driven corrections for detector efficiencies, geometric acceptance, and multiple scattering. Furthermore, I will discuss the treatment of radiative effects, which differ significantly between electrons and muons. These efforts are critical for reaching the sub-percent precision required to constrain potential new physics or conventional explanations of the proton radius discrepancy.