Measurement of the asymmetry parameter in the hyperon radiative decay Sigma +-->p gamma.

We have measured the asymmetry parameter (alpha(gamma)) in the hyperon radiative decay SIGMA+ --> p-gamma with a sample of 34754 +/- 212 events obtained in a polarized charged hyperon beam experiment at Fermilab. We find alpha(gamma) = -0.720 +/- 0.086 +/- 0.045, where the quoted errors are statistical and systematic, respectively.