Measurement of the Up-Down Asymmetries in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>β</mml:mi></mml:math>Decay of Polarized<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Λ</mml:mi></mml:math>Hyperons (Argonne-Chicago-Ohio State-Washington University Collaboration)

Abstract

We report results from a counter and optical spark-chamber-spectrometer experiment on the $\ensuremath{\beta}$ decay of polarized $\ensuremath{\Lambda}$ hyperons. A sample of 218 decays, constituting approximately one third of the total data, has been identified. The measured up-down asymmetries from a selected subsample of 173 events are ${A}_{v}=0.67\ifmmode\pm\else\textpm\fi{}0.18$, ${A}_{e}=0.14\ifmmode\pm\else\textpm\fi{}0.17$, and ${A}_{p}=\ensuremath{-}0.55\ifmmode\pm\else\textpm\fi{}0.18$. When interpreted in the framework of a $V\ensuremath{-}A$ theory with no second-class currents (${g}_{2}=0$), they confirm the sign of the form-factor ratio $\frac{{g}_{1}}{{f}_{1}}$ as given by the Cabibbo model, but favor a somewhat smaller magnitude.