G.A. Moss

Measurements of NN → dπ very near threshold: (I). The np → dπ0 cross section

Abstract We have measured cross sections for the reaction np→d π 0 at beam energies very near the pion-production threshold. The yield near threshold is 23% lower than the previously accepted value based on π + d→pp data. P-wave pion production was observed at energies as low as 1.5 MeV (c.m.) above threshold. There was no evidence of narrow πNN resonances in the energy range surveyed - 275 to 291 MeV, corresponding to pion c.m. momenta between 2 and 43 MeV/ c .

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.

Measurements of p-p and p-4He analyzing powers at medium energies

Abstract High precision proton-proton analyzing power measurements have been made at incident proton energies of 225, 327, and 520 MeV for θ lab = 17°, and at 205, 308, and 499 MeV for θ lab = 24°. The relative uncertainty is ± 1% for the results at 17° and ± 3% for the data at 24°. The p- 4 He analyzing power at θ lab = 15° was measured with ± 1–2% errors at 222, 325, and 518 MeV. These results can be used as accurate calibration standards for polarized proton beams and provide accurate polarization normalizations for phase shift analyses.

The efficiency of counter telescopes for detecting intermediate-energy protons

Abstract The absolute efficiency of simple counter spectrometers for detecting protons with energies from 89 to 466 MeV has been measured experimentally. The inefficiencies due to nuclear interactions are in close agreement with calculations using available reaction cross-sections. In addition, an investigation was made of the dependence of the efficiency on the position of the proton incident on the counter. A simple mathematical model for the shape of the efficiency profiles is presented in order that the present results may be generalized to other detector geometries. The model is shown to fit the efficiency profiles for the present geometry very well.

The reaction 2H(p,π+)3H at 470 and 500 MeV

Abstract Angular distributions of the cross section at 470 and 500 MeV and the analyzing power at 500 MeV incident proton energy are presented for the reaction 2 H ( p ,π + ) 3 H . The cross section and analyzing power measurements cover the respective angular ranges 10°

Large-angle measurements of the 4He(p, d) 3He reaction at intermediate energies☆

Abstract The differential cross section for the reaction 4 He (p, d) 3 He has been measured at incident proton energies of 275, 300, 350, 400, 440, and 500 MeV in the laboratory angular range between 144° and 168°. Polarization asymmetry has been observed served at 350, 400, and 500 MeV in the same angular range. The differential cross section is strongly backward peaked at all energies. The analyzing power is smaller than that for elastic p− 4 He elastic scattering. The differential cross section, similar in slope and magnitude to that for p− 3 He elastic scattering, indicates that deutron exchange may be the major component of the reaction mechanism.

Elastic proton-3He scattering at large angles and intermediate energies

Abstract Large-angle p-3He elastic scattering differential cross section have been measured at Ep = 415 and 600 MeV where they look very similar, and at 800 MeV where the cross section is 10% of the value at 600 MeV. A one-meson-plus-2N exchange mechanism could explain this feature.

The neutron beam facility at triumf

Abstract The polarized neutron beam facility at TRIUMF has been upgraded for use in high precision neutron scattering experiments. Polarized neutrons are produced via transverse polarization transfer in the D(p,n)2p reaction at 9° in the lab. Proton beam position on the LD2 production target is stabilized to better than ±0.2 mm using a feedback system controlling beam line elements. The region of uniform neutron beam intensity at the experimental target location is a rectangular area 56 mm wide and 40 mm high. In that area the neutron beam intensity is 9 × 103 (100 nA cm2 s) and the neutron polarization is 50%. The facility is being used to determine charge symmetry breaking in n−p elastic scattering, to study neutron radiative capture by hydrogen, and a measurement of the spin correlation parameter Ann.

Detection equipment for a test of charge symmetry in n−p elastic scattering☆

Detection equipment has been developed to allow precision measurements of n−p elastic scattering of 150 to 500 MeV polarized neutron beams at TRIUMF. The apparatus permits a determination of the difference in angle, ‡θ, at which the neutron and proton analyzing powers An and Ap cross zero with a precision of ±0.04° lab at 500 MeV. From this difference in ‡θ the difference between An and Ap can be obtained to a precision of ±0.001.

Elastic proton scattering from 4He in the forward direction at 200, 350 and 500 MeV☆

Abstract The differential cross section for the elastic scattering of protons from 4He has been measured at 200, 350, and 500 MeV over an angular range from 3.5° to 15° in the lab system. In addition, the analyzing power was measured in the same angular range at 350 and 500 MeV. The experiment makes use of a tenuous gas target in which the recoil α-energy is measured with solid-state detectors. The proton scattering angle is measured outside the target by a system of multi-wire proportional counters. The differential cross sections have a nearly exponential dependence on momentum transfer in this kinematic range and grow with increasing energy. The analyzing power shows strong positive asymmetry.