Experiment

The proton radius puzzle is being addressed by a number of new experimental efforts, including heavier muonic atoms, redoing the atomic hydrogen measurements and redoing the electron scattering measurements to even lower momentum transfer. The MUon proton Scattering Experiment (MUSE) at the PSI πM1 beam line is an effort to expand the comparisons by determining the proton radius through muon scattering, with simultaneous electron scattering measurements.