B.C. Clark

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

Abstract High-quality fits to 497 MeV p− 40 Ca 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.

Relativistic nucleon-nucleus optical model

Abstract A microscopic relativistic optical model is developed and compared with the empirical optical model at low energies.

K+ elastic scattering from C and 6Li at 715 MeV/c

Abstract Elastic differential cross sections for K + mesons scattered from nat C and 6 Li targets have been measured at an incident momentum of 715 MeV/c and at angles of 7° to 42° in the laboratory frame. The experimental cross sections agree, within errors, with two different parameter-free impulse approximation calculations. To reduce the effects of the systematic errors, the ratio of the experimental cross sections for nat C to 6 Li is compared to the theoretical values, and these ratios do not agree with theory. This discrepancy suggests either a density-dependent alteration of K + -nucleon amplitudes or a failure of the optical potential calculations to describe these nuclides adequately.

Dirac-global fits to calcium elastic scattering data in the range 21-200 MeV

Abstract We present a global relativistic optical model for p+ 40 Ca consisting of Lorentz scalar and vector potentials parametrized as a function of energy. The shapes chosen are Woods-Saxons for the real potentials, and a linear combination of Woods-Saxons and derivative Woods-Saxons for the imaginary potentials.

Phenomenological optical model for p-4He elastic scattering

Abstract The results of a Dirac equation optical model analysis of p- 4 He elastic scattering data are reported. The optical potential obtained at 1029 MeV reproduces the systematics of p- 4 He data over the energy range from 560 to 1730 MeV.

Comparison of optical model results from a microscopic Schrodinger approach to nucleon-nucleus elastic scattering with those from a global Dirac phenomenology

Comparisons are made among results of calculations for intermediate-energy nucleon-nucleus scattering for C12, O16, Ca40, Zr90, and Pb208, by use of optical potentials obtained from global Dirac phenomenology and from a microscopic Schrodinger model. Differential cross sections and spin observables for scattering from the set of five nuclei at 65 and 200 MeV have been studied to assess the relative merits of each approach. Total reaction cross sections from proton-nucleus and total cross sections from neutron-nucleus scattering have been evaluated and compared with data for those five targets in the energy range 20-800 MeV. The methods of analyses give results that compare well with experimental data in those energy regimes for which the procedures are suited.

Empirical determination of the mean free path of a nucleon in the nuclear medium

Abstract The mean free path of a nucleon in the nuclear medium extracted from measured neutron-nucleus total cross sections is compared with the values determined from the energy-momentum dispersion relation. The optical potentials used in the dispersion relation are the relativistic global energy-dependent Lorentz scalar and vector potentials of Dirac phenomenology. Excellent agreement between the values extracted from either total neutron-nucleus cross sections or proton-nucleus reaction cross sections and the calculated values is achieved when the optical potentials are evaluated using radial values corresponding to approximately 80% of nuclear matter density.

Pion-nucleus elastic scattering on {sup 12}C, {sup 40}Ca, {sup 90}Zr, and {sup 208}Pb at 400 and 500 MeV

Pion-nucleus elastic scattering at energies above the Delta(1232) resonance is studied using both pi+ and pi- beams on 12C, 40Ca, 90Zr, and 208Pb. The present data provide an opportunity to study the interaction of pions with nuclei at energies where second-order corrections to impulse approximation calculations should be small. The results are compared with other data sets at similar energies, and with four different first-order impulse approximation calculations. Significant disagreement exists between the calculations and the data from this experiment.