A. Okihana

Optical model and folding model potentials for elastic scattering of 56 MeV polarized deuterons

Abstract Differential cross sections σ and all four analyzing powers Ay, Axx, Ayy and Axz have been measured for deuteron elastic scattering from 12C, 16O, 40Ca, 58Ni, 90Zr, 118Sn, 144Sm and 208Pb at 56 MeV. The tensor analyzing power Axz was measured using horizontally polarized deuterons. These data were analyzed in terms of an optical potential containing central, spin-orbit and TR type tensor terms. A complex TR tensor potential was necessary to explain Axz and the quantity X 2 = (2A xx + A yy ) √3 . The optical potentials obtained were compared with exact folding model calculations. The real part of the TR tensor potential is generally smaller than the folding model potential, especially for heavier nuclei. The imaginary TR potential is comparable with the folding model for lighter nuclei and is smaller than the folding model for heavier nuclei. The folding model TR potential overestimates the amplitudes of the Axz and X2 data. Features of the σ, Ay and Ayy data at large angles are discussed in connection with nuclear rainbow scattering.

Measurements of analyzing powers Ay, Axx, Ayy and Axz in dp elastic scattering at Ed = 56 MeV

Abstract The differential cross section and all components of the analyzing powers A y , A xx , A yy and A xz have been measured in dp elastic scattering at 56 MeV. This is the first measurement of A xz in the cyclotron energy region. A xz has been measured with the beam polarized in the horizontal plane using the polarization tagging method. Faddeev calculations have been performed for four cases of the NN interaction. The Coulomb correction gave smaller effects at the present energy than at lower energies. Three of them reproduce the experimental data well. The agreement between the calculations and data for A xz was better than that reported at lower energy. The deuteron asymptotic D- to S-state ratio has been obtained and is consistent within the limits of uncertainty with previously obtained values.

Alpha spectroscopic factors for 6Li, 7Li, 9Be and 12C from the (p, pα) reaction at 296 MeV

Abstract Three-body breakup cross sections and analyzing powers for the 6Li, 7Li, 9Be and 12 C ( p ,pα) reactions were measured at an incident energy of 296 MeV. Data were analyzed using the plane wave impulse approximation (PWIA) and the distorted wave impulse approximation (DWIA) and compared with previous studies. DWIA calculations reproduce shapes of projected spectra and analyzing power distributions fairly well with the exception of the 12 C ( p ,pα) 8 Be reactions. Extracted spectroscopic factors for 6Li, 9Be and 12C are larger than those found in the previous studies. In contrast, extracted spectroscopic factors for 7Li agree with the previous work. This work suggests that the spectroscopic factor for 6Li is ∼ 0.8, independent of incident energies and reaction types.

A study of nucleon properties in nuclei through (p, 2p) reactions

Abstract The differential cross sections and analyzing powers have been measured for a proton knockout reaction from s 1/2 orbits of several target nuclei aiming at studying nuclear medium effects in the nucleon-nucleon interaction, and in-medium nucleon properties through it. It is confirmed from the cross section data that the reaction mechanism is simple and contribution from the multi-step processes is less than ten percent, only a few percent for a 12 C target case. The analyzing power shows a distinct reduction from the value of the free proton-proton scattering and the target dependence, which is equivalent to the density dependence, of the reduction suggests existence of a medium effect. The study has been extended to the measurement of other spin observables, polarization and spin-transfer coefficients, and a preliminary result is given.

Search for deeply-bound pionic states using (p,2He) reactions at 390.6 MeV

Abstract Deeply-bound pionic states in 207 Pb have been searched for using the 208 Pb(p, 2 He) reaction at 0° with a 390.6 MeV proton beam. The spectrum near the threshold for free π − production shows contributions from π − bound states. The spectrum for 12 C taken with the same experimental method shows no signature of pionic bound states, and is explained to be composed of a flat continuum and the contribution of quasi-free π − production process.

Spectroscopy of neutron halo nucleus 11Be via the 11B (d, 2He) reaction at 70 MeV

Abstract Differential cross sections and vector and tensor analyzing powers for the 11 B(d, 2 He) 11 Be reaction at 70 MeV have been measured and Gamow-Teller and spinflip dipole transitions are identified. Observed mean excitation energy and strength for the spinflip dipole transition in which possible neutron halo effect manifests itself are consistent with the shell model prediction which takes the neutron halo into account.

Deuteron breakup with 3He at 89.4 and 118.9 MeV

Quasifree processes were studied by measuring coincident energy spectra for the 2H(3He, 3Hep)n, 2H(3He, tp)p and 2H(3He, dd)p reactions at 89.4 and 118.9MeV. The spectral shape was reproduced with two types of spectator model, that is, a three-body model (TBM) and a four-body model (FBM). The latter contains the effects of projectile breakup processes. Angular correlations of peak cross sections were explained by calculations in the FBM in contrast with those in the TBM. The absolute cross sections were not explained by either model.

Tensor analyzing power measurement of 1H(d, 2He)n reaction at 70 MeV

Abstract Tensor analyzing powers A yy were measured for the 1 H(d, 2 He)n reaction at E d = 70 MeV. At forward angles, experimental data are reasonably reproduced by a PWIA calculation. This is inconsistent with the result reported on the transverse polarization coefficients K y y , at 0° of the same reaction with a proton beam, 2 H(p, n) 2 He. This cannot be understood wholly within the frame-work of the impulse approximation. At backward angles, where the momentum transfer is large, PWIA predictions deviate far from the experimental data indicating a large contribution of the multiple scattering process.

Multiple scattering effects for quasifree scattering in 3He(d, dd)1H breakup reaction

Abstract The differential cross sections for the 3He(d, dd)1H breakup reaction have been measured in the kinematical region corresponding to quasifree scattering (QFS). The angular dependence of the cross section at the minimum laboratory energy of the unobserved proton has been obtained. The shapes of energy spectra are approximately reproduced by a calculation in the plane-wave impulse approximation (PWIA). As for the angular dependence of the cross section and for the absolute values, the calculation fails to reproduce the experimental results. A calculation with multiple scattering effects reproduces the experimental data well, not only for the shape of the energy spectra but also for the angular dependence. For the absolute cross sections, the ratio of the experimental values to the calculated ones with multiple scattering effects is 0.7 and this value is improved compared with the value of 0.3 obtained by the PWIA calculation.

Elastic scattering of 56 MeV polarized deuterons on 4He

Abstract 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- 4 He 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. 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- 4 He elastic scattering at 20.2 MeV.