Muon Capture in Gaseous Hydrogen

An experiment to measure the muon nuclear capture rate in ultrapure gaseous hydrogen (8 atm, 293^∘{}K) has been performed using a special target in which a system of gas proportional counters, working with the pure hydrogen of the target itself, were operating. Neutrons from the capture reactions were detected using a scintillation-counter technique, and the γ-ray background was eliminated by pulse-shape discrimination. The working conditions ensured that the captures were taking place in μp atomic systems in a singlet total-spin state. The experimental result is Λₑₓₚₜ=651±57 sec^-1, which has to be compared with the theoretical rate Λs, theor=626±26 sec^-1. From the experimental capture rate, and within the framework of the currently accepted theory, we have obtained for the induced pseudoscalar coupling constant gₚ=(-7.3±3.7)gV. The results of the present experiment are analyzed, together with results obtained from stopping negative muons in liquid hydrogen.