Lead-glass Calorimeter at MUSE

The MUon proton Scattering Experiment (MUSE) at the PiM1 beam line of the Paul Scherrer Institute works to simultaneously measure elastic scattering of electrons and muons from a liquid hydrogen target to extract the charge radius of the proton. Both beam polarities are measured over the course of the experiment. By comparing the four scattering cross sections, the experiment will provide unique muon proton scattering data with a precision sufficient to address the proton radius puzzle, and will directly measure two-photon exchange effects for both muons and electrons. The lead glass calorimeter at MUSE was developed primarily to measure initial-state radiation for use in radiative corrections. It can also be used to study the energy of beam particles and the stability of the energies, complementing measurements based on the dipole magnet settings and beam particle RF times. While the other techniques determine the beam momentum out of the channel, the calorimeter determines the beam energy after it has passed through beamline detectors and the cryotarget. Thus, it directly provides a measurement of the energy loss in these materials, verifying simulations and allowing the vertex kinematics to be reliably determined. This presentation will discuss these additional energy measurements done by the calorimeter.