Left Right Symmetry-breaking Sensitivity of Beta-asymmetry Measurements

Absolute and relative measurements of the beta asymmetry parameter in the decays of mirror nuclei are examined as a means of detecting the possible existence of a right-handed contribution to the weak interaction, or of providing further restrictions on it. The constraints to be obtained from these measurements on the parameters of the manifest left-right symmetric model are shown to be complementary among mirror transitions. The limitations of recent experiments and the requirements to improve the present limits are discussed

A Study of Th-223 Levels Populated By Alpha-decay

Low spin states of Th223 have been populated via alpha-decay. The parent nucleus (U227, t 1/2 approximately 1 min) was formed in the reaction Pb-208(Ne-22, 3n)U227, E(beam) = 110 MeV. Out-of-beam measurements of alpha-gamma and alpha-e- coincidences were performed with the aid of a rotating target mechanism. These measurements have enabled a limited level scheme of the low-spin states in Th223 to be constructed, along with tentative J-pi assignments and alpha hindrance factors. The data are interpreted in terms of the geometric model assuming a static octupole deformation and compared to that for the N = 133 isotones Ra-221 and Rn-219

Production of Polarized N-12 With the C-12(p,N-12)n0 Reaction

The polarization transferred to N-12 in the C-12(p -->, N-12 -->)n0 reaction has been measured at E(p) = 50 and 72 MeV. In agreement with previous work, the N-12 polarization was a strong function of the material in which the ions stop, implying a complex depolarization mechanism. The largest nuclear polarization observed, P0 = 0.260 +/- 0.002, was for N-12 implanted in Al. This result gives the lower bound K(y)y' greater-than-or-equal-to 0.377 +/- 0.003 for the transverse polarization-transfer coefficient. Distorted-wave calculations predict K(y)y' should be approximately 2/3. The angular distribution of K(y)y' at E(p) = 72 MeV is nearly isotropic, in agreement with the distorted-wave prediction. The electronic polarization relaxation time T1 for N-12 implanted in C, Al, Ni and Au was found to be approximately constant and much longer than the N-12 half-life; viz., T1 = 0.150 +/- 0.014 s

Positron polarimetry with Nd2Fe14B magnets

The potential of using permanent Nd2Fe14B magnets in a positron polarimeter has been explored with a beam of 50 MeV positrons. The asymmetries observed during a first test run provide encouraging results

The Polarization Asymmetry Correlation of In-107 and Parity Violation

We report on the first measurements of the longitudinal polarization of positrons emitted by polarized nuclei, using cryogenically polarized 107In. This so-called polarization-asymmetry correlation is very sensitive to the mass of a possible right-handed gauge boson, which is invoked by parity symmetric extensions of the standard V-A electroweak model to explain the experimentally observed strong violation of parity which, however, may not be complete. The positron polarization is deduced from the time-resolved decay spectrum of positronium hyperfine states. Our preliminary result points to a lower limit of about 210 GeV for the mass of an eventual right-handed charged W gauge boson. This result can still be improved

BOUNDS ON RIGHT-HANDED CURRENTS FROM A RELATIVE BETA-POLARIZATION MEASUREMENT WITH POLARIZED IN-107

The first measurements of the longitudinal polarization of positrons emitted by polarized 107In are reported. The positron polarization is deduced from the time-resolved decay spectrum of positronium hyperfine states. Our result is in agreement with the standard electro-weak model and provides a new lower limit for the mass of an eventual, predominantly right-handed charged W-gauge boson of 220 GeV/c2