Effect of neutral weak current in the decayΣ0→Λ0+e++e−in Weinberg's model

Abstract

Weinberg's model of weak and electromagnetic interaction predicts a longitudinal polarization of ${\ensuremath{\Lambda}}^{0}$ in the decay ${\ensuremath{\Sigma}}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}+{e}^{+}+{e}^{\ensuremath{-}}$ which can be calculated uniquely, in terms of the Weinberg angle. The polarization of ${\ensuremath{\Lambda}}^{0}$ is in general of the order of ${10}^{\ensuremath{-}5}$. However, for small $|{\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}}_{\ensuremath{\Lambda}}|$ $({\ensuremath{\Lambda}}^{0} \mathrm{momentum})\ensuremath{\simeq}{10}^{\ensuremath{-}2}$ MeV/c, the polarization is large and is \ensuremath{\simeq}0.1% for the Weinberg angle ${\ensuremath{\theta}}_{W}\ensuremath{\simeq}35\ifmmode^\circ\else\textdegree\fi{}$. The width of the peak, where the polarization is large, is narrow and is in the region where the number of events expected is small.