Analysis of reactions with polarized deuterons (II)

Criteria for a simplified analysis of polarization measurements on reactions of deuterons with light nuclei are derived. In these reactions prominent resonances appear at deuteron energies up to several MeV. The characteristic signature of such levels in polarization data can be used to determine the spin parameters of the resonant element. Methods developed in an earlier paper, dealing with isolated resonances, are supplemented to include interference terms between two or more (l, s, J) reaction matrix elements. Linear relations between expansion coefficients of different polarization quantities are given for various cases. The application of these criteria in a simple, preliminary analysis is discussed and demonstrated using experimental data available at present.     

Neutrino scattering on polarized deuterons

The possible presence of anI=0 axial vector piece in the hadronic neutral current may be detected by looking for an asymmetry in the emission of the recoil deuterons in elastic scattering of neutrinos or antineutrinos on polarized deuterons. It is estimated that this asymmetry could be about 40% with the incident neutrinos in the energy range of tens of MeV.     

Parity-nonconservation effects in the photodisintegration of polarized deuterons

P-odd correlations in deuteron photodisintegration are considered. It is shown that, in the case of unpolarized deuterons, π-meson exchanges do not contribute to these correlations. For polarized deuterons, the contribution of π-meson exchanges to the P-odd correlation is about 0.3×10^?8. The contribution to P-odd effects from weak interactions at short distances substantially exceeds the contribution from π-meson exchanges.     

Virtual breakup effects in elastic scattering of polarized deuterons

Elastic scattering of polarized deuterons at E_d = 56 MeV is investigated for ¹⁶O, ⁴⁰Ca, ⁵⁸Ni, ¹¹⁸Sn and ²⁰⁸Pb target nuclei by the use of folding interactions. Effects of virtual breakup of the deuteron to S- and D-states in the continuum region are taken into account by the CDCC method and are found to make indispensable contributions to cross sections and analyzing powers, where continuum-continuum couplings are substantial. The contribution of the D-state admixture in the ground state is important for the tensor analyzing powers. The calculated results agree well with experimental data. The invariant-amplitude method and the second-order sum rule study clarify the characteristic feature of the spin dependence of the effective interactions due to the virtual breakup. The near-side/far-side decomposition of scattering amplitudes illuminates the difference of the reaction mechanism between light and heavy target nuclei. The investigation for the ²⁰⁸Pb target at E_d = 21.5 MeV gives important information on the energy dependence of the effective interactions. The use of different parameter sets for the input nucleon-target optical potentials shows that the detailed results depend significantly on the choice of the parameter sets.     

Vector analyzing power of polarized deuterons in elastic scattering

Isotope dependence of vector analyzing powers of polarized deuterons in elastic scattering off Se targets is discussed by optical-model and coupled-channel calculations. Attention is particularly directed to relations between analyzing power and imaginary potential.     

Inclusive hadron photoproduction from longitudinally polarized protons and deuterons

We report measurements of the asymmetry A₆ for inclusive hadron production on longitudinally polarized proton and deuteron targets by circularly polarized photons. The photons were produced via internal and external bremsstrahlung from an electron beam of 48.35 GeV. Asymmetries for both positive and negative signed hadrons, and a subset of identified pions, were measured in the momentum range 10<P<30 GeV at 2.75° and 5.5°. Small non-zero asymmetries are observed for the proton, while the deuteron results are consistent with zero. Recent calculations do not describe the data well.     

Elastic scattering of polarized deuterons by protons at intermediate energies

The tensor analyzing power T₂₀(θ) in dp backward scattering has been measured at or near center-of-mass angle θ = 180° in the energy range 0.3–2.3 GeV. A pronounced structure is observed around T_d = 0.5 GeV which is explained by a predominant one-neutron-exchange mechanism. Other structures appear around 1 GeV and higher. They are not explained by calculations which include Δ-excitations in intermediate states. In addition, full angular distributions of vector A_y and tensor A_yy analyzing powers and differential cross sections have been obtained at 1.2 GeV and limited angular ranges explored at 0.5 GeV (back angles) and 1.6 GeV (forward angles).     

Use of tensor polarized deuterons in method II angular correlations

A new technique for gamma-ray angular correlation measurements using tensor polarized deuterons is illustrated with the ${}^{24}\text{Mg}\text{(}\text{d}\text{, αγ)}{}^{22}\text{Na}$ reaction. The 4.77 MeV level of ²²Na is assigned J^π = 3⁺ and the transition to the 1.95 MeV level is determined to be pure magnetic dipole.     

Measurement of the photon asymmetry in capture of polarized neutrons by deuterons

We have looked for parity violation in neutron capture by deuterons. Parity violation would produce an asymmetric angular distribution of the 6.24 MeV photon about the spin direction of the neutron of the form (1 + A cos θ), where θ is the angle between photon momentum and incident neutron spin. We find A = (4.2 ± 3.8) × 10⁻⁶, where the error is the statistical error of counting. If we include an estimate of systematic errors, the error increases to ± 3.9. In addition there is an overall scale error which can be described by multiplying the result by (1 ± 0.15). The value is one standard deviation larger than predictions based on either Cabbibo or gauge theoretical models, which give values of A between 10⁻⁶ and 10⁻⁷.     

On the test ofT-invariance in elastic scattering of electrons from polarized deuterons

An additional (magnetic) form factor G₂ which violatesT-invariance is introduced in the electromagnetic vertex of the deuteron. This additional interaction yields a right-left asymmetry in the scattering of electrons from polarized deuterons. For our numerical evaluations we used values of G₂ which are consistent with the deviations from the impulse approximation found in measurements of the unpolarized cross section. A maximum asymmetry of approximately 40 percent was obtained at q=3.5 f^?1. However, care must be taken in the preparation of the polarized target, as a suitable tensor polarization may also produce asymmetry.     

Elastic scattering of vector polarized deuterons by 4He

The vector analyzing power iT₁₁ for deuterons elastically scattered by ⁴He has been measured for c.m. angles between 51.8° and 158.9° and deuteron energies in the range 11.5 to 17 MeV. The results show that d-α scattering is a convenient analyzer for deuteron vector polarization in the energy range investigated, since the angular dependence of iT₁₁ is fairly insensitive to energy and the magnitude of iT₁₁ is quite large at some angles.     

Elastic and inelastic scattering of 11.8 MEV polarized deuterons from 34S

The elastic and inelastic scattering of 11.8 MeV vector polarized deuterons from ³⁴S has been studied. Angular distributions of the cross section σ(θ) and vector analyzing power iT₁₁(θ) have been measured for the ground state and the first three excited states in ³⁴S. Optical model parameters were first obtained by fitting the elastic deuteron scattering data alone. DWBA calculations with a collective model form factor were performed for the inelastic scattering to the excited states. Coupled-channels calculations were also done both for the one-phonon and the two-phonon excited states. The optical model parameters were suitably modified to obtain simultaneous fit to elastic and inelastic data when channel coupling was introduced. The values of the vibrational parameter β₂ for one- and two-phonon states are discussed and compared with those obtained from γ-decay width studies.     

Elastic scattering of 56 MeV polarized deuterons on 4He

The differential cross section and the vector and tensor analyzing powers A_y, A_xx, A_yy and A_xz were measured for the d-⁴He elastic scattering at 56 MeV. The measurement of A_xz was performed using a deuteron beam polarized in the horizontal plane. An optical-model analysis of the experimental data was carried out. The magnitude of the tensor analyzing powers could not be reproduced without the tensor potential. By including the T_R type tensor potential, the optical-model calculations give a reasonable reproduction of the experimental data at θ_c.m. < 120°. The obtained T_R tensor potential was much stronger than that predicted by the folding model. The strength of the real T_R potential was roughly in accordance with that obtained from the optical-model analysis of d-⁴He elastic scattering at 20.2 MeV.     

A study of deuteron quadrupole moment effects in sub-coulomb scattering of tensor polarized deuterons

Measurements of the tensor analyzing power T₂₀ are presented for deuteron elastic scattering from ²⁰⁸Pb at energies below the Coulomb barrier. It is found that, for energies below about 7 MeV, T₂₀ arises primarily from the interaction of the deuteron quadrupole moment with the nuclear electric field gradient. Contributions to T₂₀ from nuclear interactions with the target are shown to be very small for E_d ? 5 MeV. Measurements of T₂₀ at E_d = 4 MeV, accurate to ± 8 × 10^?5, are presented. After correcting for deuteron stretching and a number of additional small effects, the data are used to make a new determination of the quadrupole moment. The result, Q = 0.282 ± 0.019 fm², is in good agreement with the conventional value deduced from molecular hyperfine structure data.     

Nuclear reactions between energetic deuterons in contemporary beam-injected tokamak experiments

In tokamak heating experiments utilizing nearly isotropic D° injection, or with unidirectional injection and plasma Z_eff ? 1, large-relative-velocity collisions between energetic deuterons can be the dominant source of D-D neutrons when $\text{n}{}_{\mathrm{<mtext>hot</mtext>}}\text{n}{}_{\mathrm{<mtext>e</mtext>}}\text{?}\text{1}\text{10}$.     

Coupled-channels effects for inelastic scattering of 15 MeV polarized deuterons from Ti and Sm isotopes

Cross sections and analyzing powers have been measured for elastic and inelastic scattering of 15 MeV deuterons from ¹⁴⁸'Sm and ¹⁵²Sm. These data, as well as previous data for the ${}^{\mathrm{48,\; 50}}\text{Ti}\text{(}\text{d}\text{, d'}\text{)}$ reaction have been analyzed in the coupled-channels approximation. Data for ⁴⁸Ti and ¹⁵²Sm are better described by the rotational model than by the vibrational model but the quality of the fits is not sufficiently good to establish ($\text{d}\text{, d'}$) reactions as a sensitive method of discriminating between these two models.     

Elastic and inelastic scattering of vector polarized deuterons from even samarium isotopes at 56 MeV

Differential cross sections and vector analyzing powers of deuteron elastic and inelastic scattering have been measured at 56 MeV over the whole range of the even samarium isotopes. Comprehensive analyses were performed with the optical model and the coupled-channels formalism. In the optical model analysis, calculations with a global parameter set could reproduce the experimental data only for the vibrational nuclei. The strong coupling approximation was applied assuming the ^{144, 148, 150}Sm to be harmonic vibrators and the ^152,154Sm symmetric rotators. The 2^λ (λ = 2, 3, 4, 6) pole deformation parameters were deduced from a systematic coupled-channels analysis. The transition strengths were extracted from the deformed optical potentials and compared with the corresponding electromagnetic ones. The transition rates for the rotational nuclei agreed with the electro-magnetic ones, but those for the vibrational nuclei gave the systematically smaller values. The latter fact was attributed to the difference between the proton and neutron transition matrix elements near the neutron-closed-shell nuclei. The ratios of the two matrix elements were obtained.