Proton polarization in the 3He(d,p)4He reaction

Abstract

The proton polarization in the 3He(d,p)4He reaction induced by unpolarized deuterons has been measured at deuteron lab. energies of 2.0, 2.8, 3.9 and 6.0MeV for 20 angles between 0° and 150° (c.m.). Statistical uncertainties are typically ± 0.01. The measurements were made with a proton polarimeter in which the left-right asymmetry of scattering at 60° (lab.) in 4He is determined. The polarimeter employs "venetian-blind" collimation of the protons by conical vanes and 75 cm2 plastic scintillator detectors. Four detectors are included for use in polarization transfer experiments. For 10.5 MeV protons and a helium pressure of 250 p.s.i. the target thickness is 3 MeV and the efficiency per detector per unpolarized proton incident is 10-4. For each polarimeter detector a triple coincidence with a 15 ns resolving time was required with two scintillator transmission detectors preceding the polarimeter. Spectra of random coincidences were accumulated simultaneously and subtracted. Asymmetries resulting from polarimeter-target misalignment and other geometrical effects are discussed. All results quoted are geometric means of pairs of measurements for 180° rotation of the polarimeter and are also arithmetic means of such measurements to left and right of the 3He target. The absolute analyzing power is estimated by computer simulation of trajectories to be -0.638 ± 0.020 for protons entering at 10.3 MeV. The product of polarization and cross section is fitted to an expansion of first-order associated Legendre polynomials using these results and earlier measurements. Only four terms are required except at 6.0MeV where a fifth is necessary. The energy dependence of these coefficients suggests resonances in 5Li at deuteron energies of 60MeV (odd coefficients) and 7.5 MeV (even coefficients) in agreement with results for the polarized-beam analyzing powers(1). Comparison of the results with vector-polarized-beam (1) and polarized-target(2) analyzing powers shows no evidence for the postulated simple relations(3) based on DWBA cal calculations. Comparison of the results with recent measurements of the neutron polarization in the mirror reaction(4) shows no significant differences. The theory of angular correlations in charged particle reactions is developed and used to calculate outgoing nucleon polarizations. Expressions are given for polarization transfer coefficients. These coefficients are evaluated in terms of the T-matrix elements for the interference of various channels with the dominant S-wave, JΠ = 3+/2 channel in 3He(d,p)4He at the 0.43 MeV resonance. Two experiments to measure combinations of these elements are discussed. (1) Gruebler, W. et al., 1971, Nucl. Phys. Al76, 631 (2) Leemann, Ch., W. Gruebler et al., 1971, in Polarization Phenomena in Nuclear Reactions (University of Wisconsin Press), p. 548 (3) Tanifuji,M. and K. Yazaki, 1968, Prog. Theor. Phys. 40, 1023 (4) Mutchler, G.S., W.B. Broste and J.E. Simmons, 1971, Phys. Rev. C3, 1031