FAMU

Recent measurements of electron-proton scattering and muon hydrogen spectroscopy produce discrepant results with respect to the charge radius of the proton. The FAMU experiment aims to contribute to the solution of this puzzle by measuring the Zemach radius of the proton by means of hyperfine splitting measurements in muonic atoms.

The FAMU detector consists of a vessel that contains the gas mixture where muon captures take place, starting from a muon beam that is located at the RIKEN-RAL laboratories (UK). The characteristic X-rays emitted, following the de-excitations of the muon atoms, are revealed by a series of photo-detectors (HPGe, LaBr₃)), with an energy resolution better than 3%.

The FAMU-Pavia group is responsible for the realization of the muon beam monitor (hodoscope) and the LaBr₃photo-detectors with SiPM read-out. After a number of technical runs held in the years 2015-2018, the final data taking campaign of FAMU is scheduled for 2022-2023.