A High Precision Measurement of Polarized Sigma- beta Decay

We report the results of a polarized-..sigma../sup -/ beta-decay experiment carried out in the Fermilab Proton Center charged-hyperon beam. These results are based on 49 671 observed ..sigma../sup -/..-->..ne/sup -/nu-bar decays. The ..sigma../sup -/ beam had a nominal momentum of 250 GeV/c and was produced by 400-GeV/c protons im- pinging on a Cu target. At a production angle of 2.5 mrad, the polarization was (23.6 +- 4.3)%. The decay asymmetries of the electron (..cap alpha../sub e/ = -0.519 +- 0.104), neutron (..cap alpha../sub n/ = +0.509 +- 0.102), and antineutrino (..cap alpha../sub ..nu../ = -0.230 +- 0.061) were measured and used to establish sign and approximate magnitude of the axial-vector-to-vector form-factor ratio g/sub 1//f/sub 1/. The form-factor ratios chemically bondg/sub 1//f/sub 1/chemically bond and f/sub 2//f/sub 1/ were determined most sensitively from the neutron and electron center-of-mass spectra, respectively. We obtain chemically bondg/sub 1//f/sub 1/-0.237g/sub 2//f/sub 1/chemically bond = 0.327 +- 0.007 +- 0.019 and f/sub 2/(0)/f/sub 1/(0) = -0.96 +- 0.97 +- 0.13, where the stated errors are statistical and systematic, respectively. A general fit that includes the asymmetries and makes the conventional assumption g/sub 2/ = 0 gives the final value g/sub 1/(0)/f/sub 1/(0) = -0.328 +- 0.019.more » The data are also compatible with positive values for g/sub 2//f/sub 1/ combined with corresponding reduced values for chemically bondg/sub 1//f/sub 1/chemically bond. .AE« less