Generalized fresnel model for very heavy ion scattering: (III). Dynamic polarization effects

It is shown that the large deviations from the typical Fresnel shape of heavy ion angular distributions, observed recently in the elastic scattering from deformed nuclei, can be described quite adequately by a very simple modification of the closed formulae for the differential cross section ratio $\text{gs(θ)}\text{σ}{}_{\mathrm{R}}\text{(θ)}$ of the generalized Fresnel model presented in parts I and II of this work. Our treatment rests basically on the relatively long range of the dynamic polarization potential that describes the Coulomb excitation to which the large deviations from the normal Fresnel pattern are attributed. We also calculate the effects of nuclear coupling in an adiabatic approximation and show that these lead to another modification, this time of the damping function F(z), which is however much smaller than that for Coulomb excitation and hardly discernible in angular distributions for very heavy ion scattering.     

Inelastic scattering of heavy ions at intermediate energies with excitations of nuclear collective states

Excitation of low-lying nuclear collective states upon scattering of heavy ions with energies of several tens of MeV/nucleon has been studied. The interaction potential leading to excitation is chosen in the form of a derivative of the microscopic (or semimicroscopic) nucleus-nucleus double-folding optical potential. Elastic and inelastic scattering cross sections have been calculated within the high-energy approximation; the inelastic scattering amplitude was obtained in the first order in the deformation parameter. The cross sections are compared with the experimental data on scattering of ¹⁷O from a series of nuclei with excitation of the 2⁺ level.     

On the possibility of detecting superheavy quasimolecules

The formation of superheavy electronic quasimolecules leads to measurable deviations from the Rutherford cross section in heavy ion collisions. For the system ²³⁸₉₂U-²³⁵₉₂U with E_c.m. = 800 MeV we find an average correction of 1.5% for the scattering cross section in forward directions. Additional background contributions like electronic shielding of the nucleus, vacuum polarization, nuclear Coulomb excitation and static deformations of the nuclei are taken into account.     

Application of a folding-model optical potential to analyzing inelastic pion–nucleus scattering and the in-medium effect on a pion–nucleon amplitude

The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π ^±-mesons on ²⁸Si, ⁴⁰Ca, ⁵⁸Ni, and ²⁰⁸Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2⁺ and 3^? collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion–nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole (β ₂) and octupole (β ₃) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion–nucleon amplitude is emphasized.     

Ground state reorientation effects in elastic scattering cross sections

Elastic scattering cross sections are shown to be quite sensitive to ground state reorientation amplitudes and cross sections. These effects are dramatically evident when comparing scattering from even-even nuclei with that from high-spin odd-A nuclei, and may affect choices of potentials for odd versus even nuclei. Neutron scattering data from ²³⁵U and ²³⁸U are analyzed via coupled channels methods. The diffraction minima in elastic scattering from ²³⁵U are found to be dominated by reorientation cross sections. The majority of this reorientation is shown to follow from second order virtual nuclear excitations rather than proceeding through amplitudes for direct ground state reorientation.     

Excitation of nuclear collective states by heavy ions within the model of semimicroscopic optical potential

The (semi)microscopic double-folding nucleus-nucleus optical potentials are suggested for consideration of inelastic scattering with excitation of collective nuclear states by using the adiabatic approach and the elastic scattering amplitude in the high-energy approximation. The analytical expression for inelastic scattering amplitude is obtained keeping the first-order terms in the deformation parameter of a potential. Calculations of inelastic cross sections for the ¹⁷O heavy ions scattered on different nuclei at about hundred MeV/nucleon are made, and the acceptable qualitative agreement with the experimental data is obtained without introducing free parameters. The prospect of the method for further applications is discussed. The text was submitted by the authors in English.     

Electromagnetic dissociation of ultrarelativistic heavy ions and cross sections for photonuclear reactions in the region of a giant resonance

In calculating cross sections for the electromagnetic dissociation of heavy ions by the Weizsäcker-Williams method, use is made of approximations and extrapolations of experimental data on photonuclear reactions. On the basis of the predicted cross sections for the mutual dissociation of nuclei in beams of ultrarelativistic colliders, it is proposed to measure, among other things, the yields of neutrons from such a dissociation in order to monitor the luminosity of accelerators. Considerable discrepancies between the results of different photonuclear experiments impose limitations on the accuracy of the method. The reasons behind these discrepancies are determined on the basis of a systematic analysis of available data on the cross sections for photoneutron reactions, and a method for removing them is proposed. By considering the example where new data on the dissociation of ²⁰⁸Pb nuclei at an energy of 30 GeV per nucleon are compared with the results of calculations, it is shown that the use of evaluated cross sections for partial photoneutron reactions of the (γ, n) and (γ, 2n) types makes it possible to improve the accuracy in calculating cross sections for electromagnetic dissociation.     

Analysis of elastic and inelastic α + <Superscript>24</Superscript>Mg scattering within the <Emphasis Type="Italic">S</Emphasis> matrix model involving regge poles

A generalization of the phenomenological S-matrix model taking into account isolated Regge poles is proposed for simultaneously describing refractive effects in the cross sections for the elastic and inelastic scattering of light nuclei. The cross sections for elastic α + ²⁴Mg scattering are analyzed at energies of 50, 54, 65.7, 81, and 119 MeV. The analysis of the cross sections for elastic scattering is supplemented with an analysis of the inelastic scattering of alpha particles that is accompanied by the excitation of the first excited state (2⁺) of ²⁴Mg nuclei. It is shown that the proposed model makes it possible to describe satisfactorily all of the aforementioned cases of elastic and inelastic scattering, correctly reproducing the refraction Airy structures and anomalous large-angle scattering that are observed at large scattering angles.     

Nucleus-nucleus scattering in the high-energy approximation and optical folding potential

A microscopic complex folding-model potential that reproduces the scattering amplitude of Glauber-Sitenko theory in its optical limit is obtained. The real and imaginary parts of this potential are dependent on energy and are determined by known data on the nuclear-density distributions and on the nucleon-nucleon scattering amplitude. For the real part, use is also made of a folding potential involing effective nucleon-nucleon forces and allowing for the nucleon-exchange term. Three forms of semimicroscopic optical potentials where the contributions of the template potentials—that is, the real and the imaginary folding-model potential—are controlled by adjusting two parameters are constructed on this basis. The efficiency of these microscopic and semimicroscopic potentials is tested by means of a comparison with the experimental differential cross sections for the elastic scattering of heavy ions ¹⁶O on nuclei at an energy of E ～ 100 MeV per nucleon.     

Diffractive scattering of loosely bound nuclei involving two charged clusters on nuclei

The theory of diffractive interaction between loosely bound nuclei featuring two charged clusters and nuclei is developed with allowance for Coulomb interaction. The differential cross sections for the scattering of ⁶Li, ⁷Be, and ⁸B nuclei on ¹²C nuclei are calculated, and the results of these calculations are compared with data from recent experiments.     

Diffraction scattering of Λ 3 H and Λ 6 He hypernuclei on nuclei with allowance for edge diffuseness, the structure of hypernuclei, and multiple-scattering effects

General formulas for the amplitudes of the diffraction scattering of two-and three-cluster loosely bound nuclei on spherical nuclei for an arbitrary dependence of the profile functions on the impact parameter are represented in a form that is convenient for calculations. The differential cross sections for the elastic scattering of _Λ ³ H and _Λ ⁶ He hypernuclei and the total cross sections are obtained with allowance for the diffuseness of the target-nucleus edge, the binding energy of incident hypernuclei, the ranges of nuclear forces between the clusters in the hypernuclei, and multiple (double and triple) scattering. Changes in the behavior of the cross sections in response to a transition from the two-cluster to the three-cluster model of the aforementioned nuclei are revealed.     

Elastic scattering of 1 GeV protons from nuclei as a test for flucton model

Cross sections for elastic scattering of 1 GeV protons from⁴⁰Ca nuclei have been calculated using the flucton model. The influence of the collective flucton nuclaon correlations on the calculated cross sections is examined. The calculated cross sections are in significant disagreement with the experimental data. This may be considered as an argument against the flucton model.     

Effect of the shell structure of nuclei on p 15C and p 15N scattering within diffraction theory

The differential cross sections for elastic proton scattering on ¹⁵C and ¹⁵N nuclei at energies of 150 and 800 MeV were calculated within the diffraction theory of Glauber multiple scattering. Shellmodel wave functions were used in these calculations, and particular attention was given to analyzing the sensitivity of the calculated features to distinctions between the shell structure of the ¹⁵C nucleus and the shell structure of the ¹⁵N nucleus. The calculations were performed in the approximation of double scattering. The multiple-scattering operator was written in a form that permits taking into account collisions with nucleons belonging to different shells. It is shown that the difference in structure between the two nuclei in question leads to substantial distinctions between the differential cross sections for scattering at an energy of 800 MeV and scattering angles larger than 25°.     

Effects of a non-standardW ± magnetic moment inW ± production via deep inelastice −P scattering

We calculate the production of charged bosons in deep inelastice ^?P scattering in the context of an electroweak model in which the vector boson self interactions may be different from those prescribed by the electroweak standard model. We present results which show the dependence of the cross section on the anomalous magnetic dipole moment κ of theW ^±. We find for energies available at HERA that even small deviations from the standard model value of κ imply observable deviations in theW ^± production rates. We also show that the contributions from heavy boson exchange diagrams are very important.     

Fusion and transfer reactions in beams of light loosely bound nuclei at energies in the vicinity of the Coulomb barrier

Experiments devoted to studying cross sections for fusion and transfer reactions induced by the interaction of beams of halo-like (⁶He), cluster (⁶Li and ⁷Li), and loosely bound (³He) nuclei with nuclei of light and heavy elements are described. The cross sections obtained experimentally for such reactions are analyzed. Special features in the behavior of the cross sections for the formation of evaporation residues and products of transfer reactions at energies in the vicinity of the Coulomb barrier are revealed. In particular, an increase in the cross sections for fusion and transfer reactions involving halo-like nuclei and proceeding at energies in the subbarrier region is observed. The cross sections for neutron-transfer and light-cluster-transfer reactions reachmaximum values at an energy in the vicinity of the Coulomb barrier for the reaction being considered.     

The interaction and fusion of arbitrarily oriented deformed nuclei

The fusion/capture cross sections between various deformed nuclei are calculated. It is shown that quadrupole and hexadecapole deformations of heavy nuclei are important for evaluating the barrier height, capture well depth, and fusion/capture cross sections of heavy nuclei. It is found that calculations of the capture cross section of two heavy deformed nuclei must be performed with averaging over all possible mutual orientations of the colliding nuclei.     

Transfer reactions at high energy and ambiguities in heavy-ion potentials

The smaller impact parameters that contribute to transfer reactions between heavy ions at high energies make them more sensitive to different types of optical potentials than is the case at lower energies. This may allow one to distinguish between potentials that otherwise generate similar elastic scattering cross sections within the limited angular region over which typical elastic data are available. We cite as evidence results for nucleon transfers induced by¹⁸O +²⁸Si at 352 MeV which rule out surface transparent potentials.