Properties ofΣDecays and theΣ0Lifetime

Abstract

The consequences of a possible nonconservation of parity in the electromagnetic decay, ${\Sigma }^0\to {\Lambda }^0+\gamma$, are deduced and an experimental test of parity conservation is proposed. In order to devise a method to determine the ${\Sigma }^0$ lifetime, $\tau \left({\Sigma }^0\right)$, a study is made of ${\Lambda }^0\to {\Sigma }^0$ conversion in ${\Lambda }^0$-nucleus collisions and it is found that the ${\Lambda }^0\to {\Sigma }^0$ conversion induced by the nuclear Coulomb field, with cross section proportional to $\frac{Z^2}{\tau \left({\Sigma }^0\right)}$, is the dominant process at large $Z$ for ${\Sigma }^0$ generation in approximately forward directions. In addition, the implications of a principle of "minimal weak coupling" (involving a conserved baryon-meson polar-vector current) are exhibited for ${\Sigma }^{\pm }\to {\Lambda }^0$ strangeness-conserving leptonic decays and are used to propose a further conceivable method to determine the ${\Sigma }^0$ lifetime. Throughout the discussion, the various cross sections and decay rates are given for the two possible relative intrinsic parities of the ${\Lambda }^0$ and ${\Sigma }^0$.