Dirac Optical Potential Research Articles

Isovector dirac optical potentials and nucleon charge exchange reactions

Abstract The isovector part of the Dirac optical potential for nucleon-nucleus scattering is calculated using a folding model approach based on the relativistic nucleon-nucleon t-matrix. Exchange and Pauli blocking effects are taken into account. The calculated potentials are compared with those obtained in the impulse approximation. We use these potentials in a relativistic DWBA calculation of the amplitude for charge exchange (p, n) reactions leading to the isobaric analog states. Good agreement is obtained with the cross section and analyzing power data for reactions on 48Ca, 90Zr, and 208Pb nuclei. We also present calculations for the spin rotation parameter.

Dirac optical potentials constrained by a Dirac-Hartree approach to nuclear structure.

Lorentz scalar and four-vector optical potentials are obtained for protons elastically scattered from /sup 16/O, /sup 40/Ca, /sup 48/Ca, /sup 90/Zr, and /sup 208/Pb. It is demonstrated that Dirac optical potentials constrained by relativistic Hartree theory are capable of producing good agreement with experiment

Vacuum polarization effects in elastic scattering of protons by nuclei

Sensitivity of spin observables in elastic proton scattering by nuclei to the vacuum polarization correction δϱ VAC is explored. The Dirac optical potential is calculated from a complete set of Lorentz invariant amplitudes, Dirac-Hartree densities and the existing estimate of δϱ VAC based on quantum hadrodynamics.

New aspects of the hadron-nucleus interaction

A review is presented of recent developments in the field of intermediate energy hadron-nucleus interactions. Particular reference is made to new formulations, in the impulse approximation of a Dirac optical potential, and to the importance of medium effects in the effective nucleon-nucleon interaction. Finally, some comment is made on recent experimental investigations of pion production and of nuclear pick-up reactions.

Reactive Content of the Proton-Nucleus Impulse-Approximation Dirac Optical Potential

The total reaction cross sections for intermediate-energy proton scattering on $^{40}\mathrm{Ca}$ and $^{208}\mathrm{Pb}$ are calculated within the Dirac-eikonal formalism. Comparison with data indicates that the recently proposed impulse-approximation Dirac optical potential for nucleon-nucleon scattering is quite adequate, and accounts for 90% of the measured total reaction cross section.

Effective isoscalar nucleon-nucleon interactions at 500 MeV

The 500 MeV effective nucleon-nucleon isoscalar interaction is investigated through nonrelativistic folding model analysis of $\stackrel{\ensuremath{\rightarrow}}{p}$+nucleus elastic scattering data. Three empirical interactions are deduced. The first, obtained from a relativistic-Schr\"odinger-equation-equivalent form of a phenomenological Dirac optical potential, contains terms which are dependent on the square of the nuclear matter density. A modified version of this interaction is then obtained, in which the density dependence is made explicit. Finally, an optical potential is deduced which depends linearly on the density, resulting in a density-independent nucleon-nucleon effective interaction. Nuclear size information inferred from calculations using these effective interactions is found to be in reasonable agreement with theoretical expectations. The relative merits of each of these three forms of the interaction are discussed.

Relativistic Impulse Approximation forp-Nucleus Elastic Scattering

First calculations based on an impulse-approximation Dirac optical potential are presented. All input parameters are constrained by other experimentally determined quantities. Excellent agreement with ${T}_{p}=500$ MeV ${p}_{\mathrm{pol}}$+$^{16}\mathrm{O}$ and $^{40}\mathrm{Ca}$ elastic scattering data is demonstrated. The differences between the relativistic and nonrelativistic results are explored in detail.

Impulse-Approximation Dirac Optical Potential

The impulse approximation to the Dirac optical potential for proton-nucleus elastic scattering is deduced from elementary considerations and found to be in remarkably good agreement with phenomenological parameters. The large difference between the real parts of scalar and vector optical potentials is explained by the impulse approximation.

Prediction of the spin-rotation function Q( θ) using a dirac equation based optical model

High-quality fits to 497 MeV p− 40Ca cross sections and analyzing powers are obtained using a Dirac equation optical model treatment. The predicted spin-rotation function Q( θ) agrees well with experiment. The spin rotation observable provides almost no new information about the real part of the Dirac optical potential but may provide some information about the imaginary part.