Characterization of Muon and Electron Beams in the Paul Scherrer Institute PiM1 Channel for the MUSE Experiment

TL;DR

This paper characterizes the muon and electron beams in the PiM1 channel at PSI, demonstrating its suitability for high-precision scattering experiments relevant to the MUSE project.

Contribution

It provides a detailed analysis of the beam properties and simulations, validating the PiM1 channel for muon and electron scattering measurements.

Findings

G4beamline simulations agree with experimental measurements

PiM1 channel can achieve high-precision muon and electron scattering

Beam properties are suitable for the MUSE experiment

Abstract

The MUon Scattering Experiment, MUSE, at the Paul Scherrer Institute, Switzerland, investigates the proton charge radius puzzle, lepton universality, and two-photon exchange, via simultaneous measurements of elastic muon-proton and electron-proton scattering. The experiment uses the PiM1 secondary beam channel, which was designed for high precision pion scattering measurements. We review the properties of the beam line established for pions. We discuss the production processes that generate the electron and muon beams, and the simulations of these processes. Simulations of the $\pi$/$\mu$/$e$ beams through the channel using TURTLE and G4beamline are compared. The G4beamline simulation is then compared to several experimental measurements of the channel, including the momentum dispersion at the IFP and target, the shape of the beam spot at the target, and timing measurements that allow the beam momenta to be determined. We conclude that the PiM1 channel can be used for high precision $\pi$, $\mu$, and $e$ scattering.