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Register a new userMechanism of proton-$^3{rm He} $ elastic backward scattering at intermediate energy
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We provide systematic analysis of the differential cross section of the proton-$^3{rm He}$ elastic scattering at $theta_{rm cm}=180^{circ}$ and at $T_p<700$ MeV. Three mechanisms are discussed: 2N pair exchange in the triplet and singlet spin states, pion exchange and direct mechanism. It is shown that t Tp>150 MeV tree-body structure, including triplet and singlet states of the 2N pair, becomes of great importance for understanding energy dependence of the reaction observables. Prediction for the differential cross section and the polarization correlation $C_{00nn} which can be studied now in experiment are given. PACS number(s): 21.30.Cb, 21.30.-x, 25.40.Cm, 25.55.Ci
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We present a precise measurement of the cross section, proton and $rm ^3He$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-$rm ^3He$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $Delta$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the $rm ^3 He$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $Delta$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-$rm ^3He$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering.
We present new accurate measurements of the differential cross section $sigma(theta)$ and the proton analyzing power $A_{y}$ for proton-$^{3}$He elastic scattering at various energies. A supersonic gas jet target has been employed to obtain these low energy cross section measurements. The $sigma(theta)$ distributions have been measured at $E_{p}$ = 0.99, 1.59, 2.24, 3.11, and 4.02 MeV. Full angular distributions of $A_{y}$ have been measured at $E_{p}$ = 1.60, 2.25, 3.13, and 4.05 MeV. This set of high-precision data is compared to four-body variational calculations employing realistic nucleon-nucleon (NN) and three-nucleon (3N) interactions. For the unpolarized cross section the agreement between the theoretical calculation and data is good when a $3N$ potential is used. The comparison between the calculated and measured proton analyzing powers reveals discrepancies of approximately 50% at the maximum of each distribution. This is analogous to the existing ``$A_{y}$ Puzzle known for the past 20 years in nucleon-deuteron elastic scattering.
For backward elastic scattering of deuterons by ^3He, cross sections sigma and tensor analyzing power T_{20} are measured at E_d=140-270 MeV. The data are analyzed by the PWIA and by the general formula which includes virtual excitations of other channels, with the assumption of the proton transfer from ^3He to the deuteron. Using ^3He wave functions calculated by the Faddeev equation, the PWIA describes global features of the experimental data, while the virtual excitation effects are important for quantitative fits to the T_{20} data. Theoretical predictions on T_{20}, K_y^y (polarization transfer coefficient) and C_{yy} (spin correlation coefficient) are provided up to GeV energies.
Background: Theoretical calculations of the four-particle scattering above the four-cluster breakup threshold are technically very difficult due to nontrivial singularities or boundary conditions. Further complications arise when the long-range Coulomb force is present. Purpose: We aim at calculating proton-${}^3$He elastic scattering observables above three- and four-cluster breakup threshold. Methods: We employ Alt, Grassberger, and Sandhas (AGS) equations for the four-nucleon transition operators and solve them in the momentum-space framework using the complex-energy method whose accuracy and practical applicability is improved by a special integration method. Results: Using realistic nuclear interaction models we obtain fully converged results for the proton-${}^3$He elastic scattering. The differential cross section, proton and ${}^3$He analyzing powers, spin correlation and spin transfer coefficients are calculated at proton energies ranging from 7 to 35 MeV. Effective three- and four-nucleon forces are included via the explicit excitation of a nucleon to a $Delta$ isobar. Conclusions: Realistic proton-${}^3$He scattering calculations above the four-nucleon breakup threshold are feasible. There is quite good agreement between the theoretical predictions and experimental data for the proton-${}^3$He scattering in the considered energy regime. The most remarkable disagreements are the peak of the proton analyzing power at lower energies and the minimum of the differential cross section at higher energies. Inclusion of the $Delta$ isobar reduces the latter discrepancy.
Observables in elastic proton-deuteron scattering are sensitive probes of the nucleon-nucleon interaction and three-nucleon force effects. The present experimental data base for this reaction is large, but contains a large discrepancy between data sets for the differential cross section taken at 135 MeV/nucleon by two experimental research groups. This paper reviews the background of this problem and presents new data taken at KVI. Differential cross sections and analyzing powers for the $^{2}{rm H}(vec p,d){p}$ and ${rm H}(vec d,d){p}$ reactions at 135 MeV/nucleon and 65 MeV/nucleon, respectively, have been measured. The data differ significantly from previous measurements and consistently follow the energy dependence as expected from an interpolation of published data taken over a large range at intermediate energies.
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