Abstract
The parity-violating component of the 482 keV gamma transition of 181Ta has been investigated by measuring its degree of circular polarization. Two Compton forward scattering analysers were used and the scattered gamma rays were detected by eight lead-loaded plastic scintillators, each one connected to an independent energy selection and counting system. Because of the small asymmetry expected a careful investigation of the various sources of systematic errors was made. The possible causes of such systematic errors were minimized or eliminated. False asymmetries of the polarimeters and detectors were measured using the 498 keV gamma transition from a 103Ru source. A calculation of the asymmetry due to bremsstrahlung shows that it is negligible, due to the energy selection. The efficiency of the polarization analysers was calculated and experimentally measured by beta-gamma circular polarization correlation on 198Au. Our result for the polarization of the 482 keV transition of 181 Ta is: {ce:inline-formula}P = −(0.21±0.11)·10 −4{/ce:inline-formula}.Comparisons with theoretical estimates and previous experiments are made.
Published Version
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