Search for Positron Emission inK40

Abstract

A search for positron emission in ${\mathrm{K}}^{40}$ has been made with the use of a triple coincidence technique. An upper limit of (3.6±1.8)×${10}^{-4\mathrm{}}$ positron per second per gram of natural potassium has been set. A corresponding upper limit of 0.59±0.28 has been computed for the ratio of the squares of the matrix elements, $\frac{{M_{+}}^2}{{M_{-}}^2}$, for the ${\mathrm{K}}^{40}$ ${\beta }^{+}$ and ${\beta }^{-}$ transitions.