Measurement of charged particle spectra emitted following muon nuclear capture in Si nuclei

When a negative muon stops in matter, it is captured into an atomic orbit, and subsequently, it is captured by the atomic nucleus at a certain probability through the weak interaction 1. This process is known as muon nuclear capture (µNC). In this process, most of the muon's rest energy is carried away by a muon neutrino and the remainder is used to excite the residual nucleus. This excited nucleus may emit charged particles such as protons, deuterons, and alpha particles, in addition to gamma rays and neutrons. The low-energy spectra of these emissions reflect the evaporation process from the compound nucleus formed after µNC. Conversely, the spectral shape in the high-energy region is considered to reflect the details of the pre-equilibrium process.