The FAMU experiment at RAL to study the muon transfer rate from hydrogen to other gases

The aim of the FAMU experiment is to realize the first measurement of the hyperfine splitting (hfs) in the 1S state of muonic hydrogen $ΔE^{hfs}_{1S}$, by using the RIKEN-RAL intense pulsed muon beam and a high-energy mid-infrared tunable laser. This requires a detailed study of the muon transfer mechanism at different temperatures and hence at different epithermal states of the muonic system. The experimental setup involves a cryogenic pressurized gas target and a detection system based on silicon photomultipliers-fiber beam hodoscopes and high purity Germanium detectors and Cerium doped Lanthanium Bromide crystals, for X-rays detection at energies around 100 keV. Simulation, construction and detector performances of the FAMU apparatus at RAL are reported in this paper.