LIMITS ON NONSTANDARD WEAK CURRENTS FROM THE POLARIZATION OF O-14 AND C-10 DECAY POSITRONS

We report the relative polarization of the P(F)/P(GT) = 0.9996 +/- 0.0037 for the positrons emitted by the pure Fermi O-14 and the pure Gamow-Teller C-14 decays, using a technique based on the observation of the positronium-decay time spectrum. The radioisotopes to be compared are part of the same source, eliminating some of the potential systematic errors which may vitiate relative polarization measurements of high precision. Combining our result with a similar Al-26(m)/P-30 decay positron comparison obtained by Bhabha polarimetry, we deduce the following constraint on the product of the mixing angle-zeta and mass-squared ratio-delta of the chiral W bosons assumed in left-right symmetric models: -0.0004 < zeta-delta < 0.0007 (90% C.L.). Our result also constrains possible scalar and tensor admixtures to the dominant vector and axial-vector currents: [GRAPHICS]