H. Nann

Total cross section for p+p→p+p+π0 close to threshold

Abstract Making use of an electron-cooled beam in the IUCF storage ring, we have measured the total cross section σ tot for pp→pp π 0 at 31 bombarding energies between 285 and 325 MeV. At a level of about 5%, the data show no fluctuations that could be associated with the onset of other pion production channels. A calculation of the single-partial-wave cross section σ ss , including direct production only (no rescattering), falls short of the experiment by a factor of 5.2±0.3, but reproduces the observed energy dependence when scaled. This energy dependence is explained by contributions from the phase-space factor and the final-state interaction between the outgoing nucleons. The relative importance of higher partial waves is deduced from the energy dependence of σ tot as well as from the angular distributions of reaction protons.

High-spin 1p-1h configurations in sn-116 and their fragmentation as seen in the reactions sn-116(-]p,p'), sn-116(e,e'), in-115(3he,d) and in-115(alpha, t)

Stretched spin configurations in 116Sn have been studied via the reactions 116Sn(p, p′), 116Sn(e, e′), 115In(3He, d) and 115In(α, t). The high-spin negative parity two-neutron quasiparticle states within the N = 51 − 82 major shell appear to be little fragmented. The most prominent examples are the Iπ = 9- state at Ex = 3.522 MeV and two 7− states at 2.909 and 3.120 MeV. It is found that in contrast the proton configurations (g−192, h112) and (g−192 g72) are strongly fragmented. Large-basis BCS shell model calculation, using a SkE-force have been made and DWBA analyses of the (e, e′) data and of the (p, p′) data are presented.

Deeply-bound hole states in 57Co and the spreading of the 1d52 hole strength distribution

In an attempt to locate the 1d52 proton hole state in 57Co we have measured the 58Ni(d, 3He)57Co reaction with 79.6 MeV vector polarized deuterons. An overall energy resolution of 50 keV was achieved with a magnetic spectrometer. The spectra show fine structure up to Ex = 11 MeV; this fact was used to define energy bins for which cross sections and analyzing powers were obtained. The latter allowed spin and parity assignments for deep-lying hole states in 57Co. Spectroscopic factors were obtained by applying standard DWBA calculations. Most of the strength above 6.6 MeV was identified as being 1d52 in nature. The running sum of Spectroscopic factors shows a linear increase implying a nearly uniform spread of the 1d52 Spectroscopic strength or a width of the 1d52 hole state comparable to the excitation energy.

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.

Spin determinations from the 58Ni(d→, α)56Co reaction at 80 MeV

Vector analyzing power angular distributions for the 58Ni(d→,a)56Co reaction have been measured at 80 MeV bombarding energy. They exhibit large differences between the possible transferred total angular momenta J=L+1, J=L and J=L − 1, thus allowing unique spin determinations of the levels in the residual nucleus 56Co. This has led to new spin assignments for the following high-spin states in 56Co: 3.54 MeV, 7+; 4.44 MeV, 7+; 5.14 MeV, 5+.

Low-lying excitations in sup 176 Yb and sup 180 Hf from ( rvec p , p prime ) scattering at E sub p =98. 4 MeV

The low-lying excited states of two rotational nuclei, {sup 176}Yb and {sup 180}Hf, have been investigated up to an excitation energy of 3.5 MeV by means of high-resolution inelastic scattering of 98.4-MeV polarized protons. The spins and excitation strengths of the observed levels have been deduced by comparing the measured cross sections and asymmetries with coupled-channel calculations. The deduced quadrupole, hexadecapole, and octupole strengths have been compared with the predictions of the interacting boson model in the {ital sdg}- and {ital sdf}-boson schemes.

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.

Measurement of the relative sign of neutron and proton transition matrix elements of the 2+ states in 30Si

Abstract Measurement of the inelastic alpha scattering cross sections for the first two 2 + states in 30 Si shows unambigously that the relative sign of the neutron and proton transition matrix elements for both 2 + states are positive. For the first 2 + state, this is consistent with its collective nature. For the second 2 + state, the result is consistent with recent lifetime measurements for the corresponding transition in 30 P but is in contradiction with the prediction of shell-model calculations.

Spectroscopy of 14C from the 11B(α,p)14C reaction at 118 MeV

Abstract Proton angular distributions have been measured for the 11 B(α, p) 14 C reaction at 118.1 MeV. DWBA calculations employing three-nucleon semi-microscopic form factors were made for states of excitation energies ranging from 6 MeV to 21.5 MeV. The weak coupling shell model wavefunctions of Lie were used in the DWBA calculations for states of 14 C below 12 MeV excitation energy. For states above 14.8 MeV 3p-5h components in the 14 C wavefunctions are shown to play a dominant role.