Precise half-life measurement of the superallowedβ+emitter38Ca

Abstract

The half-life of ${}^{38}$Ca, a ${T}_{Z}=\ensuremath{-}1$ superallowed ${0}^{+}$$\ensuremath{\rightarrow}$ ${0}^{+}$${\ensuremath{\beta}}^{+}$ emitter, has been measured to be 443.77(36) ms. In our experiment, pure sources of ${}^{38}$Ca were produced and the decay positrons were detected in a high-efficiency 4$\ensuremath{\pi}$ proportional gas counter. Since the ${\ensuremath{\beta}}^{+}$ decay of ${}^{38}$Ca feeds ${}^{38}$K${}^{m}$, which is itself a superallowed ${\ensuremath{\beta}}^{+}$ emitter, the data were analyzed as a linked parent-daughter decay. Our result, with a precision of 0.08$%$, is a factor of 5 improvement on the best previous result.