The deuteron breakup reaction induced by protons of 65, 85 and 100 MeV

Coplanar energy sharing spectra for p + d breakup at 65, 85 and 100 MeV proton bombarding energies were measured using the University of Maryland sectored isochronous cyclotron, by measuring the energies of either two protons or one proton and one neutron in coincidence. The detector angles were chosen to enhance either the p-p or p-n quasifree scattering, or the p-n final state interaction. The energy dependence of the peak cross section at equal symmetric quasifree scattering angle pairs was extracted for the ²H(p, 2p)n and ²H(p, pn)p reactions. Quasifree angular distributions were obtained for the reaction ²H(p, 2p)n at 65 MeV and for the reaction ²H(p, pn)p at 65, 85 and 100 MeV. The plane wave impulse approximation theory can only qualitatively reproduce the shape of the quasifree scattering peak in the energy sharing spectra and the shape of the p-p quasifree angular distribution. The discrepancies observed between the plane wave impulse approximation theory and the experimental data imply that the presence of the spectator particle (i.e., the multiple scattering effects) has a strong influence on the magnitude and the shape of the experimental results. Multiple scattering calculations were carried out in the three-body model of Aaron, Amado and Yam except that the S-wave separable two-body amplitudes were modified to fit two-nucleon elastic scattering data at higher energies. Comparisons of the results of these multiple scattering calculations to the experimental data show excellent quantitative agreement throughout the energy range and the angular region of this experiment, except for a few cases in which this model is inherently insufficient; namely, regions in which the Coulomb interaction is important, or regions for which a Hulthén wave function is inaccurate and the off-shell effects are not properly taken into account.     

Proton-neutron correlation in the deuteron breakup at 56 MeV and prior-form DWBA analysis

Proton-neutron angular correlations in the ¹²C, ⁵¹V and ¹¹⁸Sn(d, pn) reactions have been measured at 56 MeV to investigate the deuteron breakup process. The elastic breakup which leaves the target nucleus in its ground state dominates the coincident spectra. The elastic breakup cross sections are estimated to be 36–48% of the inclusive breakup yields at 15° or 17.5°. In the angular correlations the protons are emitted predominantly on the side of the beam opposite to the neutrons. The experimental data have been analyzed using the prior-form DWBA. For both nuclear and Coulomb breakup, sufficient convergence of the calculations is obtained by including the pn angular momenta up to l = 2. For the nuclear breakup calculations, the l = 0 and 2 contributions dominate the cross sections. For the Coulomb breakup the l = 1 contribution is predominant. In the calculations the effect of the Coulomb breakup is seen at forward angles of the angular correlation. The DWBA calculations reproduce fairly well the coincident energy spectra and the angular correlations in the angular region where the protons are emitted on the side of the beam opposite to the neutrons. On the other hand the calculations overestimate the break-up cross sections by a factor of 2 to 10 in the angular region where the protons are emitted on the same side of the beam as the neutrons. The distributions of deuteron c.m. angular momenta that contribute to the breakup amplitude are examined to obtain information on the region of space in which the breakup reactions takes place.     

Spin observables in small-angle elastic → d scattering with an L-type deuteron target at 800 MeV

We have measured spin correlation parameters that describe the elastic scattering of 800 MeV polarized protons from an L-type polarized deuteron target at laboratory angles below 20°. The measured parameters include the correlated analyzing powers A_SL, A_LL and A_NLL and the proton spin-transfer coefficients C_0L,S, C_0L,L, C_SL,N, C_NL,S, C_NL,L and C_LL,N. The results are compared with single-scattering predictions based on different phase-shift solutions for the nucleon-nucleon scattering matrix.     

Elastic and inelastic scattering of 185 MeV protons from 12C

The polarization of 185 MeV protons in elastic scattering and in the excitation of the 2⁺ state at 4.44 MeV and the 0⁺ state at 7.65 MeV in ¹²C has been measured in the angular region 2°–60°. Optical model calculations are performed for the elastic scattering. Angular distributions for the inelastic scattering from the 2⁺ state at 4.44 MeV and the 3^? state at 9.64 MeV are calculated in the distorted-wave impulse approximation (DWIA) as well as in the distorted-wave Born approximation (DWBA).     

Deuteron breakup by α-particles at 13,15 and 18 MeV

Kinematically complete measurements on the D(α, αp)n reaction have been made at three low energies for the incident α-particle and for a number of coplanar angular combinations at each energy. The experimental data, which thus cover a substantial phase space volume, provide material for a severe test of low-energy reaction theories. The data have been analysed in a three-body model, which relies on the numerical solution of the Faddeev equations in momentum space. Rank-one separable two-body potentials for the alpha-nucleon and nucleon-nucleon systems have served as the input information.Agreement between calculated and measured cross sections ranges from excellent to rather poor. Due to the strong effect of the Coulomb correction, which at present is quite uncertain, the appearance of cases with excellent agreement may be fortuitous. The variation of on-shell properties of the two-body potentials produce small changes in the cross sections, implying that more refined models must be employed to achieve good agreement, for instance, the explicit inclusion of effects due to the Pauli principle. However, before firm conclusions in this respect can be drawn, much greater confidence has to be gained in how to treat the Coulomb interaction in few-body breakup reactions.     

Deuteron breakup by low-energy α-particles

An investigation of the ²H(α, αp)n reaction at a lab energy of 15 MeV has been performed. Results from kinematically complete measurements at eleven angular combinations are presented and analyzed in terms of a semiphenomenological impulse approximation. It is found that if contributions from three-nucleon transfer reactions and n-p final state interactions as well as sequential reactions via states in ⁶Li are included, it is possible to reach qualitative agreement with the data.     

Lifetime of the 3.854 MeV state in 13C by the recoil-distance method

The lifetime of the 3.85 MeV state in ¹³C has been remeasured by the recoil-distance method using the ¹²C(d, p)¹³C reaction. The value of the mean life determined is τ = 13.0 ± 0.4 ps. This result is compared to previous measurements, both by the Doppler-shift attenuation method and the recoil-distance method.     

Disintegration of the deuteron by 4 to 11 MeV electrons

The ratio of photodisintegration to electrodisintegration yields was measured in the 4 to 11 MeV region. The results are in good agreement with a virtual photon calculation.     

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.     

Shell effects on state densities with given numbers of excited protons and neutrons

A new method is introduced to calculate particle-hole state densities taking into account the complete structure in both the proton and neutron shells. The results are given for three nuclei: ²⁰⁸Pb, ¹⁷²Yb and ¹¹⁷Sn. They are compared with previous formulae and with two other expressions derived in the present paper. Strong shell effects are displayed and discussed.     

Backward inclusive spectra in proton-nucleus collisions at 640 MeV

Inclusive proton spectra induced by 640 MeV protons at θ_p = 150° are presented for ²H, ⁶Li, ⁷Li, ¹²C and Cu targets. In the case of ⁶Li the experimental results are compared with calculations made in the impulse approximation using experimentally determined parameters.     

The polarization of protons from the 2H(d, p)3H reaction for deuteron energies below 1 MeV

The angular distribution of proton polarization P^γ' (θ) from the ${}^2\text{H}\text{(}\text{d,}\text{p}\text{)}{}^3\text{H}$ reaction has been measured at 975 keV deuteron energy. Moreover, the energy dependence of P^γ′(E_d) was measured at 45°(lab) for deuteron energies between 250 and 975 keV. The values of σ₀(θ)P^γ' (θ) were fitted in terms of an associated Legendre polynomial expansion. The measured energy dependence of P^γ' (E_d) has been analyzed in terms of barrier-penetration parameters.     

Analysis of deuteron break-up induced by protons up to 160 MeV

In the Faddeev amplitudes, the inhomogeneous term is calculated with a realistic local potential and the sum of the upper order terms is evaluated exactly by solving the coupled integral equations with a simple separable potential. The validity of this method is tested for experimental deuteron break-up results using incident protons between 14 and 160 MeV.     

The elastic scattering of protons by deuterium

Proton-deuteron elastic scattering was investigated with a gas target. Excitation curves were taken at 45.28°, 90.26°, and 118.92° c.m. for lab proton energies from 4.5 to 11.5 MeV. Angular distribution were taken at 4.45, 5.45, 6.50, 7.46, 8.47, 9.47, 10.47 and 11.47 MeV from 30° to 140° c.m. Differential cross sections were measured with an absolute error of less than ±3%. The scattering data were compared with predictions derived from the scattering amplitudes of Aaron, Amado and Yam ¹⁰). No evidence for the existence of ³He excited states was found in this energy range.     

Study of deuteron breakup in light targets at intermediate energies

Reaction cross-sections and proton removal cross-sections in deuteron-induced reactions with carbon and beryllium targets are studied at intermediate energies. The cross-sections calculated in eikonal approximation show a good agreement with experimental data. The sensitivity of the cross-sections to the target structure, the nucleon-target interaction potential, and the spatial distribution of nucleons in the deuteron is discussed. Received: 30 May 2001 / Accepted: 2 October 2001     

The width of the 5.11 MeV state in 10B and isovector parity mixing

We review estimates for effects of parity mixing on the α-capture of vector polarized ⁶Li to the 5.16 MeV, 2⁺, T = 1 state in ¹⁰B. The cross section depends on the ⁶Li polarization direction because of isovector parity mixing with the 5.11 MeV, 2^?, T = 0 state. The effect is enhanced due to isospin conservation. The α-width of the 5.11 MeV state, an important parameter for calculating the enhancement, has been measured to be 0.98 ± 0.07 keV. The consequences of parity mixing are reevaluated using best available values for the relevant parameters.     

Scattering of polarized protons by deuterium from 1 to 3 MeV

Polarized proton beams of energies 0.99, 1.32, 2.21 and 3.12 MeV have been used to measure the angular distributions of the polarization in the interaction D(p, p)D. The accuracy of the datum points ranges from 0.005 to 0.011. A positive value of about 0.01 is discerned at the lowest energy centre-of-mass angles from 60° to 120°. This effect increases to about 0.05 at the highest energy with a maximum near 120°.     

Polarization in the inelastic scattering of 185 MeV protons

The polarizations produced in the inelastic scattering of 185 MeV protons exciting the lowest octupole states in ¹²C and ²⁰⁸Pb are measured. The data together with earlier similar measurements for ⁴⁰Ca and ⁹⁰Zr are compared with existing theoretical models. The inclusion of a deformed spin-dependent interaction of the full Thomas form in the DWBA amplitude is found to considerably improve the theoretical fits to the data. For ¹²C, however, the DWBA fit is found to be inferior to that obtained using DWIA. The strong absorption model is found to give qualitatively good fits to the data for the heavier nuclei but again fails in the ¹²C case.     

Li(p,pd)He reaction at 100 MeV

An angular correlation experiment of the ⁶Li(p, pd)⁴He reaction at 100 MeV has been performed using a symmetric and coplanar geometry and covering an angular range from 45.5 to 57°. In addition to the conventional ΔE-E telescope systems for the detection of both protons and deuterons, a 14° analyzing magnet was employed to select deuterons of a given momentum range. The results for the ground state transition are consistent with those obtained at other incident energies. The angular distribution for the transition to the 20 MeV excited state of the recoiling α-particle was also obtained and the overall magnitude of the differential cross section is at least an order of magnitude smaller than that of the ground state transition. The plane wave impulse approximation (PWIA) was used to analyze the experimental results. A form factor was generated using the Saxon-Woods potential as the d-α inter-cluster potential. Satisfactory agreement between theory and experiment was obtained. A value of 0.45 ±0.08 was extracted for the deuteron clustering probability on ⁶Li. The exchange and the optical distortion effects were also discussed.