G. M. Stinson

Deformation and target spin-dependent effects in 9Be + p at 220 MeV☆

Abstract Cross-section and analyzing-power measurements were performed for the 9 Be(p¯, p 0 ) 9 Be and 9 Be(p¯, p 2 ) 9 Be* reactions. The depolarization parameter D was also measured on the first reaction. The data were analyzed in terms of standard optical-model and macroscopic DWBA as well as coupled-channel calculations. The former approach does not reproduce well the elastic and inelastic analyzing-power data. Coupled-channel calculations provide a good description of both the cross-section and analyzing-power data. The D -data are interpreted in terms of contributions from both the quadrupole spin-flip mechanism and the nucleon-nucleus spin-spin interactions.

The 40Ca(d,n)41Sc reaction; neutron polarization and angular distribution measurements

Abstract The angular distributions and neutron polarizations have been measured for the reaction 40 Ca(d,n) 41 Sc at a deuteron bombarding energy of 6 MeV. The polarization measurements, from 0° to 120°, were made for neutron groups corresponding to the ground, 1.718 MeV and 2.415 MeV states in 41 Sc. Additional angular distribution measurements were made for neutron groups corresponding to the 2.096, 2.719 and 3.463 MeV states in 41 Sc. Good agreement is found between the observed and DWBA predicted neutron angular distributions. No satisfactory agreement between the experimental and calculated neutron polarizations is found for any reasonable choice of optical parameters.

Quasi-free collisions of 400 MeV protons in deuterium and carbon

Abstract The first results from a program to compare quasi-free proton and neutron knockout from nuclei are presented. The binding energy of the s and p neutron hole states in 12 C have been obtained. Relative cross sections for proton and neutron knockout from 2 H and 12 C were determined for two very different kinematical conditions. The ratio, R of σ(p, pn) to σ(p, 2p) is in agreement with estimates based on the impulse approximation for 2 H but there is a deviation for 12 C. These observations suggest that refinements will have to be made to the theoretical ideas used to analyze quasi-free knockout reactions.

Parity violation in P‐P scattering at TRIUMF

The TRIUMPF experiment 497 which will measure the (weak) parity violating component of the nucleon‐nucleon interaction with proton‐proton quasi‐elastic scattering at 223 MeV is described. The longitudinal analyzing power Az=(σ+−σ−)/(σ++σ−) where σ+ and σ− are the scattering cross sections for positive and negative beam helicity, respectively, with an expected precision of ±2×10−8. (AIP)

TWIST- The TRIUMF weak interaction symmetry test the Michel parameters from μ+ decay

Abstract We propose to make the first high precision measurements of nearly the entire differential spectrum (in energy and angle) of positrons from the decay of polarized muons. The main goal of the experiment is the precise testing of the ( V - A ) structure of electroweak interactions in the framework of the SU (2) L × U (1) model. Highly polarized “surface” μ + from the TRIUMF M13 beamline will enter a large volume, high field superconducting magnet on axis and will stop in a thin target at its center. The e + from the muon decay will be precisely tracked in the magnetic field using small-cell planar drift chambers. This spectrometer has been simulated with GEANT and EGS4 and has been demonstrated to meet the precision requirements.

Parity violation in p-p scattering

Abstract An outline is given of an experiment to measure parity violation in p-p scattering at 230 MeV at TRIUMF. The parity-violating longitudinal analysing power A z will be measured to a precision of 2×10 −8 and will isolate the parity-violating 3 P 2 − 1 D 2 partial wave amplitude.

Elastic scattering of polarized protons at 200 to 500 MeV

We have measured proton elastic scattering cross sections and analyzing power angular distributions on Ca and 208Pb at 200, 300, 400, and 500 MeV. The 400 MeV data from 208Pb have been fitted by an optical model and also compared with results of Impulse Approximation calculations.

Quasi free scattering of polarized protons from 40Ca

Measurements have been made of the cross section and asymmetry of the 40Ca(p↘,2p) reaction. Peaks corresponding to the knockout of protons from the 1d3/2, 1d5/2 and 2s1/2 shells are seen. By comparing the asymmetry for protons from the 2s1/2 shell with that arising from free p‐p scattering, information on spin orbit distortion effects is obtained.This experiment was performed using a 200 MeV polarized proton beam from the TRIUMF cyclotron. The polarization and interacting of the incident beam were monitored in a polarimeter and an ion chamber. The energies and angles of outgoing protons were measured by four detector telescopes consisting of plastic scintillation counters, multi‐wire proportional chambers, and 75 mm thick × 125 mm diameter NaI (Tl) scintillation crystals. Coincidences between particles traversing detector telescopes on opposite sides of the beam line were recorded. Missing energy spectra for events with recoil momenta ∠ 0 MeV/c and ∠ 100 MeV/c are shown in Figures I(a) and I(b) respective...

Parity violation in proton-proton scattering

Abstract Measurements of parity-violating longitudinal analyzing powers (normalized asymmetries) in polarized proton-proton scattering provide a unique window on the interplay between the weak and strong interactions between and within hadrons. Several new proton-proton parity violation experiments are presently either being performed or are being prepared for execution in the near future: at TRIUMF at 221 MeV and 450 MeV and at COSY (Kernforschungsanlage Julich) at 230 MeV and near 1.3 GeV. These experiments are intended to provide stringent constraints on the set of six effective weak meson-nucleon coupling constants, which characterize the weak interaction between hadrons in the energy domain where meson exchange models provide an appropriate description. The 221 MeV is unique in that it selects a single transition amplitude ( 3 P 2 - 1 D 2 ) and consequently constrains the weak meson-nucleon coupling constant h ϱ pp . The TRIUMF 221 MeV proton-proton parity violation experiment is described in some detail. A preliminary result for the longitudinal analyzing power is A z = (1.1 ± 0.4 ± 0.4) × 10 −7 . Further proton-proton parity violation experiments are commented on. The anomaly at 6 GeV/c requires that a new multi-GeV proton-proton parity violation experiment be performed.

The TRIUMF parity violation experiment

An experiment (E497) is underway at TRIUMF to measure the angle-integrated, parity violating longitudinal analyzing power, A{sub z}, in proton-proton elastic scattering, to a precision of {plus_minus}0.2{times}10{sup {minus}7}. The experiment uses a 221 MeV longitudinally polarized proton beam incident on a 40 cm liquid hydrogen target. The beam energy is carefully chosen so that the contribution to A{sub z} from the J=0 parity mixed partial wave ({sup 1}S{sub 0}{minus}{sup 3}P{sub 0}) integrates to zero over the acceptance of the apparatus, leaving the experiment sensitive mainly ({gt}95{percent}) to A{sub z} arising from the {sup 3}P{sub 2}{minus}{sup 1}D{sub 2}, J=2 wave. To minimize sources of systematic error, the TRIUMF ion source and cyclotron parameters have been refined to the extent that helicity correlated beam changes are at an extremely low level, and specialized instrumentation on the E497 beamline is able to measure residual helicity correlated modulations to a precision consistent with the goals of the experiment. A data taking run in February-March, 1997 logged approximately 12{percent} of the desired data and produced a preliminary result, A{sub z}=(1.1{plus_minus}0.4{plus_minus}0.4){times}10{sup {minus}7}, where the error is statistical only. {copyright} {ital 1997 American Institute of Physics.}