π−Capturel in Complex Nuclei and Nuclear Pair Correlations

Abstract

Scintillation counters in coincidence were used as detectors of neutrons and protons produced in pi /sup -/ capture by complex nuclei. By measuring neutrons, it was hoped to establish whether pi /sup -/ capture in complex nuclei involves two nucleons, and if it does, to use the process to study the ratio of neutron--proton pairs to proton--proton pairs. The pi /sup -/ mesons were stopped in Li, C, Al, S, Cu, and Pb targets. In order to test the spatial correlation of the ejected nucleons, measurements were made with the counters 90 and 180 deg from each other. The results obtained are given as coincidences as a function of angle. If corrections are made for relative probability of detecting neutrons and protons, the following ratios of n--n events (a) STA pi / sup -/ + p + n yields n + n! to n--p events (b) STA pi /sup -/ + p + p yields n + p! are obtained: carbon, a/b = 5.0 plus or minus 1.5; aluminum, a/b = 3.9 plus or minus 1.2. Due to background subtractions and secondary events contributing more to the proton coincidence runs, it is felt that these observed ratios are to bemore » taken as lower limits on the ratio of reaction. (B.O.G.)« less