The Production of Neutrons byμ-Meson Capture in Lead, Magnesium, and Calcium

Measurements are reported of the yield of disintegration neutrons from the capture of stopped negative $\mu$-mesons in Pb, Ca, and Mg. A magnetized iron lens is used to separate $\mu$-meson capture from other processes giving rise to neutrons associated with telescope anticoincidences. The functioning of the lens is tested experimentally by observation of decay electrons from stopped mesons; as a byproduct, the competition between capture (${\tau }_{-}=1\mathrm{}$ μsec for Mg) and natural decay (${\tau }_0=2.15\mathrm{}$ μsec) is confirmed. The telescope coincidence and anticoincidence rates are in excellent agreement with recent absolute determinations of the $\mu$-meson spectrum at sea level.