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Parity violation in proton-proton elastic scattering provides a unique window on the hadronic weak interaction. At low and intermediate energies, the coupling constants of an effective meson exchange model provide an appropriate parametrization. Measurements at different beam energies permit the lowest partial wave amplitudes to be determined in a model independent framework. The TRIUMF cyclotron provides a unique opportunity to measure the 3P2−1D2 contribution to proton-proton parity violation at 221 MeV beam energy. This partial wave in turn isolates the weak ρ meson exchange contribution, which is only known to within a factor of 2 from theoretical estimates. An experiment underway for many years at TRIUMF completed data taking in 1999, and the analysis is now nearing completion. Preliminary results, based on half of the acquired data sample, are consistent with the meson exchange model prediction at this beam energy.

A polarimeter capable of determining transverse component polarization profile of the 222 MeV proton beam both in horizontal (x) and vertical (y) directions with faster than 1 Hz scanning frequency has been developed and built as part of the preparations in the TRIUMF Experiment 497 measuring the flavour conserving hadronic weak interaction (parity violation measurement). The design features and test performance results are presented.

The Doppler-shift attenuation method was used to obtain the following mean lifetimes (in psec) for the indicated nuclear levels: $^{10}\mathrm{C}$(3.36), $\ensuremath{\tau}=0.155\ifmmode\pm\else\textpm\fi{}0.025$; $^{10}\mathrm{B}$(3.59), $\ensuremath{\tau}=0.150\ifmmode\pm\else\textpm\fi{}0.015$; $^{10}\mathrm{Be}$(3.37), $\ensuremath{\tau}=0.189\ifmmode\pm\else\textpm\fi{}0.020$; $^{10}\mathrm{B}$(2.15), $\ensuremath{\tau}={{2.7}_{\ensuremath{-}0.4}}^{+0.5}$. A limit of $\ensuremath{\tau}l30$ fsec is obtained for $^{10}\mathrm{B}$(1.74), which is a factor of 8 greater than, and therefore consistent with, the lifetime computed from the analog $\ensuremath{\beta}$ decay of $^{10}\mathrm{C}$. Transition strengths obtained from the $^{10}\mathrm{B}$(2.15) and $^{10}\mathrm{B}$(3.59) lifetimes are in good agreement with the effective-interaction calculations of Cohen and Kurath, as modified by Warburton et al. The $^{10}\mathrm{C}$(3.36) and $^{10}\mathrm{Be}$(3.37) states decay by analog $E2$ transitions: ${2}^{+}$, $T=1\ensuremath{\rightarrow}{0}^{+}$, $T=1$, with ${T}_{z}=\ifmmode\pm\else\textpm\fi{}1$, whose strengths are well described by calculations of Kurath's for an effective charge ${\ensuremath{\epsilon}}_{n}={\ensuremath{\epsilon}}_{p}=0.5$. An upper limit was obtained for the corresponding transition 5.17 \ensuremath{\rightarrow} 1.74 in $^{10}\mathrm{B}({T}_{z}=0)$ which is consistent (factor of 4 greater) with the analog strengths observed in the ${T}_{z}=\ifmmode\pm\else\textpm\fi{}1$ nuclei.

The lifetimes of the 5.10-MeV and 5.83-MeV levels in 14N and the 6.72-MeV level in 14C have been measured using a recoil distance method and the T(12C, nγ)14N and T(12C, pγ)14C reactions respectively. The lifetimes are 12.4 ± 1.4 and 18 ± 2 ps for the 5.10-MeV and 5.83-MeV levels in 14N respectively and 97 ± 15 ps for the 6.72-MeV level in 14C. These measurements are combined with previous determinations of gamma-ray branching and multipole mixing ratios to obtain the strengths of the transitions involved. Comparison of the strengths with recent calculations shows agreement in general. The ground-state E3 transitions from the 5.10-MeV level in 14N and the 6.72-MeV level in 14C are enhanced by 2.2 ± 0.7 and 3.3 ± 0.8 Weisskopf units respectively. The isotopic spin selection rule for E1 and M2 transitions in the self-conjugate nucleus 14N is observed and discussed for some transitions. For example, the allowed M2 transition from the 5.10-MeV to the 2.31-MeV level has [Formula: see text] whereas the isotopic spin forbidden M2 part of the 5.10-MeV to ground-state transition has [Formula: see text]

A 3He–4He dilution refrigerator has been used to cool a 32 g polycrystalline cobalt rod to 0.034 K. The rod is held in a longitudinal magnetic field of 6.5 kOe and has a nuclear polarization of 0.38. The cobalt piece will be used to study the scattering of polarized and unpolarized fast neutrons from polarized 59Co.

Measurements of the spin-spin effect σss in the neutron total cross section of 59Co covering the energy range from 0.3 to 8.0 MeV are reported. The measurements were made with a target having a nuclear polarization of 33 %. Fine structure in the spin-spin effect can be explained by the statistical theory of Carlson and Barschall. The evidence for intermediate structure is inconclusive. The gross energy dependence of σss is not well reproduced by optical-model calculations employing a macroscopic spin-spin potential, even when a tensor term is added to the usual spherical potential. There is thus considerable ambiguity in the potential parameters extracted from the data. The experimental values of σss are also much larger than the predictions of any reasonable microscopic model, particularly at neutron energies less than 1 MeV.

The mean lifetimes of the 5.10 MeV and 5.83 MeV levels of 14N are 12.4 ± 1.4 ps and 18 ± 2 ps, respectively, as determined by a recoil-distance method. Absolute strengths are given for the dipole, quadrupole and octupole transitions for the γ decay of these levels.

Measurements of the 'spin-spin effect' in the neutron total cross section of 59Co employing a polarized 59Co target are reported. (Author)

Measurements of the vector analyzing power iT11 in πd elastic scattering at 49 MeV have been performed using a dynamically polarized target and a magnetic spectrometer. Data at seven π+ laboratory scattering angles between 50° and 130° were taken together with a complementary measurement at 60° for π-d elastic scattering. In general, we find agreement with models that include the πN P11 amplitude and disagreement with models that exclude or suppress it.

Measurements of the vector analyzing power iT11 in π+d elastic scattering at 50 MeV have been made at pion laboratory scattering angles between 60° and 130° using a dynamically polarized target and a magnetic spectrometer. In contrast to measurements of spin observables at higher energies, we find agreement with models that include the πN P11 amplitude and disagreement with models that exclude or suppress it.