P. Schwandt

Features of the analyzing powers in deuteron elastic scattering near 80 MeV

Abstract Measurements of the differential cross section and vector ( A y ) and tensor ( A yy ) analyzing powers are reported for deuteron elastic scattering on 58 Ni at 80 MeV. A smooth exponential decline in the cross section is present at large scattering angles. Both A y and A yy rise to large, positive values beyond 60°. These effects are understood in terms of a semiclassical description of the scattering involving only the real central and spin-orbit potentials. A comparison is made to optical-model calculations using global potentials. Additional calculations show that the T R and T P tensor potentials have small but distinguishable effects on the tensor analyzing powers.

Comparison of the noncoplanar 6Li(p, pd)4He reactions at 120 and 200 MeV

Abstract The 6 Li(p, pd) 4 He reaction was studied at 200.2 MeV, at the quasi-free angle pair ( θ p , θ d ) = (54°, −48.9°), for noncoplanarity angles φ from 0° to 28°. 6 Li αd spectroscopic factors of 0.84 and 0.76 are deduced from our coplanar data at this energy and 120 MeV, respectively, for ground-state 2S Woods-Saxon wave functions. A recent microscopic three-body calculation predicts spectroscopic factors from 0.70 to 0.75; using the ground-state wave functions from this study, we deduce a factor of 0.76 from the 200 MeV data. DWIA calculations fit the measured integrated cross sections versus φ for spectator momenta P α ≲ 100 MeV/ c at both bombarding energies, but underpredict them for larger P α . Momentum form factors were better reproduced with 1S αd cluster wave functions for a soft-core bound-state potential than with the 2S Woods-Saxon wave functions, but the former wave functions generate unphysically large (∼1.25) spectroscopic factors.

The noncoplanar 6Li(p, pd)4He reaction at 120 MeV, and the 6Li cluster momentum wave function☆

Abstract The 6Li(p, pd)4He reaction was studied at 119.6 MeV, at the quasifree angle-pair (θp, θd) = (40°, 59°), for noncoplanarity angles 0° ⩽ φ ⩽ 36°. The deduced 6Li αd spectroscopic factor (0.75) and momentum distribution (73 MeV/c) FWHM) agree reasonably well with most other intermediate-energy measurements. A minimum and adjacent secondary maximum in the integrated cross section versus φ, predicted by the DWIA theory, was observed for the first time. Cross sections at large φ are about 2.5 times greater than the DWIA predictions, suggesting contributions of higher-order processes not included in the DWIA treatment of the reaction, or larger momenta than the cluster wave function contains.

The 116Si(d, p)117Sn l=0 reaction mechanism at intermediate energies

Abstract We report measurements of the cross section, proton polarization, and deuteron vector ( A y ) and tensor ( A yy ) analyzing powers for the 116 S(d, p) 117 )Sn reaction to the 1 2 + ground state of 117 Sn at E d = 79.0 MeV. The polarization was observed as the analyzing power in the time-reversed 117 Sn(p, d) 116 Sn reaction. Adiabatic model calculations of the deuteron elastic channel reveal significant 3 D-wave breakup contributions to the elastic cross section. Satisfactory agreement with the transfer reaction data is nevertheless obtained using adiabatic calculations which include only 3 S -wave breakup and the bound deuteron D-state. The influence of the deuteron spin-orbit distortions on the polarization and vector analyzing power is reduced through a combination of the effects of angular momentum mismatch and deuteron channel absorption.

Implications of far-side dominance for the disagreement between distorted wave theory and well-matched intermediate energy (d, p) reactions

Abstract Distorted wave calculations of large l n -transfer (d, p) reactions near 90 MeV indicate that far-side dominance reduces the number of effective amplitudes at large angles to two or three, making many spin observables redundant. Comparisons of A y with A yy data for 116 Sn(d, p) 117 Sn, and A yy with p y data for 66 Zn(d, p) 67 Zn, do not confirm this expectation.

The effects of far-side dominance on the j-dependence of the medium energy 116Sn(d, p)117Sn reaction

We report measurements of the 116Sn(d, p)117Sn reaction to the d32, g72, and h112 low-lying states at 79.0 MeV. Transfer reaction calculations which include an adiabatic deuteron channel wavefunction, finite range including the deuteron S- and D-state, and non-locality corrections are performed for these transitions. A separation of the reaction amplitude into the near- and far-side components shows that the g72 and h112 reaction calculations are far-side dominated. In this context, the proton channel spin-orbit distortions modify the j-dependence of the Ay vector analyzing power and introduce a strong j-dependence in the Ayy tensor analyzing power.

The noncoplanar 7Li(p, pd)5He and 7Li(p, pt)4He reactions at Ep = 200 MeV, and evidence for deuteron clustering in 7Li

Abstract The 7Li(p, pd)5He reaction was studied at 200 MeV, at the quasi-free angle pair θ p θ d = 64° −47.4° , for noncoplanarity angles from 0° to 16°. Data were fitted with DWIA calculations, which gave a spectroscopic factor Cd of 1.1 for deuterons in 7Li if entrance-channel absorption was neglected, and 1.4 if it was not. The Cd deduced from plane-wave analysis (by comparison with 6Li(p, pd) data) is 0.9. The deuteron cluster momentum distribution is characterized, at small momentum, by an FWHM of 140 MeV/c. At large momentum there is an excess of measured cross section over predictions, as is true also for 6Li(p, pd) at intermediate energies. Cross sections for 7Li(p, pt)4He at the same experimental conditions are very small but are consistent with unit spectroscopic factor for t + α; these cross sections show the expected minimum at zero relative cluster momentum, and are adequately fitted by DWIA predictions.

Detection efficiency of Ge telescopes for 35 to 105 MeV deuterons

Abstract The probability of deuterons detected in Ge telescopes giving anomalously small pulse heights, due to their undergoing inelastic interactions and possibly elastic scattering, was measured from about 35 to 105 MeV. The loss factors, determined to 0.5% or better, increase from 3.1 to 12.2% in this region, and are consistent with a nearly energy-independent d + Ge total reaction cross section of about 2000 mb.

Multibody final states of the 6Li + 6Li reaction AT 97 MeV☆

Abstract Absolute coincidence cross sections were measured for the reactions 6Li + 6Li → 3α, 6Li(6Li, 2α), and 6Li (6Li, 2d), where the latter two represent N- body (N ≧ 4) final states. Broad peaks from the 6Li (6Li, 2α) reaction are well described by a double spectator pole (DSP) model utilizing a Hulthen wave function, whereas near 40 MeV the DSP peaks are much narrower than predicted. A broad peak in the 3α final-state spectrum, attributed to a single-spectator pole (SSP) process, is well described with the same wave function. The SSP is the principal mechanism for the 3α reaction, in contrast to data near 40 MeV which show that sequential decay from 8Be levels is dominant.

Polarization study of the 3-nucleon \vec d + p system

Many models and parameterlzatlons of the fundamental nucleon-nucleon (N-N) interactions have been developed which predict Well both the N-N observables as well as d+p elastic scattering through a Fadeev calculation. These interactions offer similar On-shell (asymptotic) features but differ In their off-shell (interior) behavior. To investigate the interior region, one may examine d+p breakup under kinematic condltlons that require a large mOmentum change for each nucleon. Since all three nucleons Participate In the reaction process, individual nucleon-nucleon Interactlons may have substanclal off-shell contributions. The requirement that the two protons interact at short range places them In an Spp 0 state. One geometry which yields this Is the Symmetrlc Constant Relative Energy (SCRE) geometry, where the three nucleons emerge with equal center-of-mass energies. Fadeev calculations show measureable discrepancies between different N-N interactions of the tensor analyzing powers Axx and Ayy in this geometry for the reaction iH(d,pp)n near E d = 80 MeV. A few values of these tensor analyzing powers have been measured by Schwandt Iet al. at E d = 79 MeV. Flgure I shows the data obtained for the tensor analyzing powers Axx and Ayy along with calculations employing the Fadeev equations with various N-N potentials. The analyzing powers are plotted with respect to the variable u, which is COmplement of the angle which the outgolng neutron makes to the beam direction in the c.m. frame. The solid llne refers to a recent Separable potential employed by Doleschall 2. The long-dashed llne is a calculation made for E d = 94 HeY by Stolk and Tjon 3 which uses an Older potential, treating the S-wave exactly and adding higher order Waves perturbatlvely. Finally, the short-dashed llne Is a separable Version of the Paris potential ~. Note that the three calculations differ substantially in the region u ~ 120°-160 ° • The data shown In Fig. 1 was obtained using discrete detector Pairs with small angular acceptances in an out-of-plane geometry Consistent with the chosen values of u. The experiment was attempted USing both solid (CH2) and gaseous targets wlth limited success. The carbon in the solid target yielded a large flux of breakup particles Which, due to the possibility of radlatlon damage in the detectors, llmlted the beam current. The gas target provided an insufficient target thickness. This, combined wlth the small solid angle required for a reasonable resolution in u, resulted in low efficiency which led to the poor statistics shown in Flg. I. We are therefore Planning a renewed effort to acquire more precise and extensive data, especially in the region where the calculations disagree. The new experimental apparatus will accept the entire SCRE region at once and will employ sclntlllatlon detectors which are not Sensltlve to radiation damage. The incoming deuteron energy will be 95 HeV and both outgoing protons will be detected in coincidence