Microscopic calculation of a model 16O nucleus

We present variational calculations for a hypothetical system of 16 nucleons interacting via the Malfliet-Tjon potential and compare our results with the Green-function Monte Carlo (GFMC) data of Helmbrecht et al.For a system of 16 bosons, we find that the (approximate) ground-state energy of our optimized hypernetted-chain calculation agrees with the GFMC data within 1%. For fermions, we find that the optimized Fermi hypernetted chain calculation leads to a ground state energy between the GFMC data and the variational Monte Carlo result with non-optimized correlations; the one-body density predicted by the FHNC theory agrees well with the one predicted by the GFMC calculation.     

Microscopic calculation of the repulsive core in the elastic nucleon-nucleon scattering

The resonating group method is used to study the effective potential between two nucleons, due to the confining potential between quarks taken together with the Pauli principle for quarks. The potential used has harmonic form, unitary spin factor λ(1)·λ(2), and both ordinary and spin-spin components. Its parameters are determined by appeal to experimental data, and phase shifts are calculated for the¹ S ₀ and³ S ₁ states of the nuncleon-nucleon (NN) system. The results indicate that the repulsive core in theNN potential may arise from quark antisymmetrization required if nucleons are composed of quarks.     

Total cross section for inclusive electron scattering in the lowQ 2 region

Absolute cross sections for inclusive electron scattering on H, D, Be, Al, and Si have been measured in the kinematical region 0.08 (GeV/c)²<Q ²<1.0 (GeV/c)² and 0.3 GeV<v<6.5 GeV. The measurements have been performed at incident energies of 3, 5, 6, and 7 GeV and at the fixed scattering angle of 10°. A careful treatment of radiative corrections due to elastic electron nucleus scattering, quasielastic and inelastic scattering on the bound nucleons has been applied to the measured cross sections. The comparison of the nuclear cross sections with the elementary ones leads to a value ofA _eff<A with a rapid onset of this effect at small values of the scaling variablex′.     

Correlation and finite interaction-range effects in high energy electron inclusive scattering

We calculate cross sections of high energy electron inclusive scattering off nuclear matter in a new and consistent formulation based on the Glauber approximation. It allows us to examine the details of the nucleon-nucleon interaction in the final-state interaction and the nuclear wave function. We point out the importance of the finite-range effect and of the nuclear short-range correlations.     

A resonant interpretation of gross structure in 12C + 12C and16O + 16O inelastic scattering

A barrier-top-resonance model calculation is found adequate to describe the gross structure behavior thus far observed in ${}^{12}\text{C}\text{+}{}^{12}\text{C and}{}^{16}\text{O}\text{+}{}^{16}\text{O}$ inelastic scattering excitation functions.     

Final-state interaction effects in exclusive and inclusive quasi-elastic electron scattering from C

Nucleon emission in the quasi-elastic region is studied for the ¹²C(e, e'p) and ¹²C(e, e'n) reactions. We present a model which couples the one-nucleon emission channels microscopically and treats the multi-nucleon emission channels phenomenologically. We analyze the spectral functions extracted from the ¹²C(e, e'p)¹¹B reaction measured at NIKHEF-K and Saclay and make predictions for the ¹²C(e, e'n)¹¹C spectral functions. The ratio of the ¹²C(e, e'p)¹¹B and ¹²C(e, e'n)¹¹C spectral functions is found to depend strongly on the two-nucleon interaction. We analyze the contribution of the one-proton and one-neutron emission channels to the inclusive longitudinal and transverse response functions. Our analysis suggests the importance of multi-nucleon emission in the quasi-elastic region. The ratio of the experimental transverse-to-longitudinal structure functions is satisfactorily reproduced.     

Microscopic calculation of low-energy deuteron-deuteron scattering on the basis of the cluster-reduction method

The cluster-reduction method is used to solve numerically the differential equations for the s-wave Yakubovsky components characterizing the nnpp system in the S=2 spin state. Elastic deuteron-deuteron scattering is analyzed for the case where nucleon-nucleon interaction is simulated by the MT I–III potentials. Effective equations describing the relative motion of clusters is derived. The scattering length and phase shifts for low-energy deuteron-deuteron scattering are calculated.     

Barrier-wave-internal-wave interference and airy minima in 16O16+O elastic scattering

Taking 16O+16O elastic scattering at 124 MeV as an example, we show that a barrier-wave-internal-wave decomposition of the elastic scattering amplitude provides valuable information on the light heavy-ion interaction and complements the more conventional nearside-farside decomposition. In particular, we show that the Airy minima present in the angular distributions are due to a barrier-wave-internal-wave interference mechanism, which sheds additional light on the exceptional transparency displayed by some light heavy-ion scattering systems. Extension of these ideas to other fields, like atomic and molecular collision physics, could prove rewarding.     

Elastic electron scattering from C and O

Electron scattering cross sections for carbon and oxygen between q = 1 fm⁻¹ and 4 fm⁻¹ are given. The data are analysed in terms of a phenomenological charge distribution and new information concerning the tail and the center of the charge distribution are obtained. The presence of dispersion effects appears to be necessary to explain the cross sections in the first diffraction minimum. The effect of a finite potential and short range correlations on the form factor are discussed.     

Phase shift calculation for low-energy electron scattering from mercury

Summary The relativistic formalism is used to study the scattering of electrons from mercury at low energy. A method of numerical integration is applied to calculate phase shifts by including a local exchange approximation and phenomenological polarization potential. The phase shifts are found to exhibit a resonant behaviour which is in conformity with the results of some earlier calculations. In contrast to the previous methods, this approach has a general validity over the entire energy range and is free from divergences. The author of this paper has agreed to not receive proofs for correction.     

Phenomenology of the electron structure function

The advantages of introducing the electron structure function (ESF) in electron induced processes are demonstrated. Contrary to the photon structure function it is directly measured in such processes. At present energies, a simultaneous analysis of both the electron and the photon structure functions gives an important test of the experimentally applied methods. Estimates of the ESF at LEP momenta are given. At very high momenta contributions from W and Z bosons together with –Z interference can be observed. Predictions for the next generation of experiments are given. Received: 17 July 2001 / Revised version: 28 August 2001 / Published online: 5 October 2001     

16O+16O molecular structure and superdeformation in 32S

The molecular structure with the ¹⁶O+¹⁶O configuration in ³²S and the superdeformed structure in ³²S are discussed from the viewpoint of the cluster model.     

Microscopic multichannel calculation of the molecular dipole degree of freedom in the18O nucleus

StrongB(E1) transitions have been recently observed between states in the¹⁸O nucleus which follow roughly the energy sequence of a dimolecular α+¹⁴C rotator. These findings have been interpreted by Gai et al. as evidence for a molecular dipole degree of freedom being present in the¹⁸O nucleus. However, this idea was contradicted by the results of a microscopic multichannel calculation performed by Descouvemont and Baye which was based on elastic α+¹⁴C and inelastic α+¹⁴C(2⁺) many-body cluster wave functions. We have improved this study by performing a microscopic multichannel calculation including additionally an+¹⁷O many-body fragmentation in order to enlarge our model space by those shell model components which dominate the structure of the (positive parity)¹⁸O ground state band. Like Descouvemont and Baye we find a positive parity α+¹⁴C molecular band in¹⁸O and, additionally, a rather strong collectivity in the lowest 1^?, 3^? and 5^? states in¹⁸O. However, since the internal structure is different within these states, the calculated states should not be interpreted as a negative parity α+¹⁴C molecular band. In this perspective, the microscopic multichannel calculations do not support the hypothesis of a molecular dipole degree of freedom being present in the¹⁸O nucleus.     

Microscopic structure of nuclei from scattering through isobaric analogue resonances

Microscopic nuclear structure information that can be reached by proton scattering through isobaric analogue resonances (IAR) is discussed, mainly within the framework of weak-coupling. The concept of isospin for unbound states is examined. A critical evaluation of the methods for extracting nuclear structure information from the experimental results (such as excitation functions, angular distributions, etc.) is given. The mass regions that are studied in detail are the Pb-region and the N = 82 neutron single-closed shell nuclei. Attention is given to the comparison between weak-coupling calculations and experimental results supporting this concept in many nuclei. Level schemes as well as proton partial decay widths and angular distributions have been calculated and compared with the existing data concerning the proton decay of IAR. The concept of generalized neutron particle-hole (GNPH) state is introduced and its occurence extensively discussed within the Pb-region and N = 82 nuclei.