MEASUREMENT OF THE BRANCHING RATIO AND ASYMMETRY PARAMETER FOR THE SIGMA(+)-]P-GAMMA RADIATIVE DECAY

We have measured the branching ratio for the hyperon radiative decay ${\mathrm{\ensuremath{\Sigma}}}^{+}$\ensuremath{\rightarrow}p\ensuremath{\gamma} using the Fermilab polarized charged hyperon beam. This measurement and our previously published result on the asymmetry parameter in the same decay are part of Fermilab experiment E761. We find B(${\mathrm{\ensuremath{\Sigma}}}^{+}$\ensuremath{\rightarrow}p\ensuremath{\gamma})/B(${\mathrm{\ensuremath{\Sigma}}}^{+}$\ensuremath{\rightarrow}p${\mathrm{\ensuremath{\pi}}}^{0}$) to be [2.32\ifmmode\pm\else\textpm\fi{}0.11(stat)\ifmmode\pm\else\textpm\fi{}0.10(syst)]\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ with a sample of 31 901 events. The higher statistics and careful attention to systematic uncertainties make these significant improvements over previous measurements. We describe how our measurements were performed and briefly review the theoretical implications of these results.