Longitudinal Polarization of Positrons from the Decay ofO14

The longitudinal polarization of 1.2-Mev positrons from the well-known 0+ → 0+ transition of 72-second $0^{14}$ has been measured. Positrons, selected by a magnetic spectrometer, were allowed to annihilate in a plastic scintillator. Annihilation-in-flight photons were analyzed for circular polarization by Compton scattering from magnetized iron. The positrons were found to have right-handed longitudinal polarization $(+0.73\mathrm{}\pm 0.17)\frac{v}{c}$.