A search for muon-electron and muon-positron conversion in sulfur

An experiment to search for the neutrinoless conversion of a muon into an electron or a positron in the processes μ- + 32S → e- + 32S and μ- + 32S → e+ + 32Sisup(*) has been carried out at SIN. No evidence for the occurrence of these conversion processes has been found. The resulting new upper limits (under certain assumption about coherence), relative to ordinary muon capture, are 7 X 10-11 (90% CL) for μ- → e-conversion and 9 X 10-10 (90% CL) for μ- → e+ conversion. The measured momentum spectra of the electrons and positrons are compatible with the background spectra expected from bound muon decay and radiative muon capture. (orig.)