A measurement of the double beta decay half-life of Ca

Ca-48 is the lightest of the many double beta decay nuclei, and the only one simple enough to be treated exactly in the shell model without truncation. Thus a beta beta(2v) measurement of this isotope provides a unique test of the nuclear physics involved in beta beta matrix element calculations. Enriched Ca-48 sources of two different thicknesses have been exposed in a time projection chamber, and yield a preliminary T-1/2(2v) = (5.5(-1.5)(+3.5)) x 10(19) y, in agreement with shell model calculations.