Ordinary muon capture studies for the matrix elements in ββ decay

Abstract

High-purity germanium (HPGe) detectors were used to make a precise measurement of the γ-ray spectrum produced following ordinary (nonradiative) capture of negative muons by natural Se, Kr, Cd, and Sm. The measurement was repeated for isotopically enriched 48Ti, 76Se, 82Kr, 106Cd, and 150Smtargets. By investigating energy and time distributions, the lifetime of negative muons in the different isotopes was deduced. A detailed analysis of the intensity of the γ lines enabled the extraction of the relative yields of several daughter nuclei. The partial rates of (μ−,ν) capture to numerous excited levels of the 48Sc, 76As, 82Br, 106Ag, and 150Tc isotopes (considered to be virtual states of the intermediate odd-odd nuclei in the ββ decay of 48Ca, 76Ge, 82Se, 106Cd, and 150Nd, respectively) were also extracted. These rates are important as an experimental input for the theoretical calculation of the nuclear matrix elements in ββ decay.