We present a parametrization and two fits to proton nucleus scattering data from 20 to 1040 MeV and mass ranges from He-4 to Pb-208. We show that He-4 can be included with the other nuclei instead of having to be treated separately as previously [B. C. Clark, E. D. Cooper, and S. Hama, Phys. Rev. C 73, 024608 (2006)]. An interesting change of sign in the imaginary potentials at low energies and high densities is noted. This may be an indicator of density dependence in the relativistic g matrix.

In the past, Dirac phenomenology has been used to determine global proton-nucleus optical potentials for a number of targets. He-4 has not been previously included in these analyses. This paper addresses p+He-4 using medium-energy proton elastic scattering data with proton kinetic energies in the laboratory from 156 to 1728 MeV. The characteristic features of the optical potentials for p+He-4 are shown as well as the the predictive power of the global approach for this nucleus.

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.

It is now generally recognized that the Dirac equation is a viable alternative to the usual Schrodinger equation approach for analyzing nucleon-nucleus scattering data. This paper reviews the development of Dirac phenomenology, stressing how closely this development has been tied to experiment. In addition we discuss a new method for extracting neutron densities from intermediate energy elastic proton-nucleus scattering observables uses a global Dirac phenomenological (DP) approach based on the Relativistic Impulse Approximation (RIA). Data sets for Ca-40, Ca-48 and Pb-208 in the energy range from 500 MeV to 1040 MeV are used. The global fits reproducing the data well and this allows one to obtain the proton and neutron densities, their root-mean-square radii, R-p and R-n, and the neutron skin thickness, S-n = R-n - R-p.

A new method for extracting neutron densities from intermediate energy elastic proton-nucleus scattering observables uses a global Dirac phenomenological (DP) approach based on the Relativistic Impulse Approximation (RIA). Data sets for Ca40, Ca48 and Pb208 in the energy range from 500 MeV to 1040 MeV are considered. The global fits are successful in reproducing the data and in predicting data sets not included in the analysis. Using this global approach, energy independent neutron densities are obtained. The vector point proton density distribution is determined from the empirical charge density after unfolding the proton form factor. The other densities are parametrized. This work provides energy independent values for the RMS neutron radius, R_n and the neutron skin thickness, S_n, in contrast to the energy dependent values obtained by previous studies. In addition, the results presented in paper show that the expected rms neutron radius and skin thickness for Ca40 is accurately reproduced. The values of R_n and S_n obtained from the global fits that we consider to be the most reliable are given as follows: for Ca40 R_n is 3.314 > R_n > 3.310 fm and S_n is -0.063 > S_n > -0.067 fm; for Ca48 R_n is 3.459 > R_n > 3.413 fm and S_n is 0.102 > S_n > 0.056 fm; and for Pb208 R_n is 5.550 > R_n > 5.522 and S_n is 0.111 > S_n > 0.083 fm. These values are in reasonable agreement with nonrelativistic Skyrme Hartree-Fock models and with relativistic Hartree-Bogoliubov models with density-dependent meson-nucleon couplings. The results from the global fits for Ca48 and Pb208 are generally not in agreement with the usual relativistic mean-field models.

The 5-dimensional spin-0 form of the Kemmer-Duffin-Petiau (KDP) equation is used to calculate scattering observables [elastic differential cross sections (dσ/dΩ), total cross sections (σTot), and total reaction cross sections (σReac)] and to deduce σTot and σReac from transmission data for K++6Li, 12C, 28Si and 40Ca at several momenta in the range 488– 714 MeV/c.Realistic uncertainties are generated for the theoretical predictions. These errors, mainly due to uncertainties associated with the elementary K++nucleon amplitudes, are large, which may account for some of the disagreement between experimental and theoretical σTot and σReac. The results suggest that the K++nucleon amplitudes need to be much better determined before further improvement in the understanding of these data can occur.

Elastic and inelastic scattering of 800 MeV protons from the axially deformed nucleus Mg-26 is analyzed using optical potentials obtained from the relativistic impulse approximation (RIA) in Dirac coupled channel formalism. A rotational collective model is used to obtain the transition optical potentials for the low-lying excited states of the ground-state rotational band. The theoretical results agree with the experimental data for the elastic and the 2(+) state, and reproduce the 4(+) excited state reasonably well. In order to check these RIA results we perform Dirac phenomenological (DP) analysis of the data and obtain the best fit Lorentz scalar and vector optical potentials. RIA and DP optical potentials are compared with those of a similar treatment for 800 MeV protons scattering from Mg-24.

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.

Elastic differential cross sections for K+ mesons scattered from natC and 6Li 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 natC to 6Li 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.

We report precision measurements of the polarization transfer parameter {ital D}{sub {ital NN}} for 500 MeV polarized proton elastic scattering from {sup 12,13}C at the first diffractive minima in the differential cross sections. The ratio {ital D}{sub {ital NN}}({sup 13}C)/{ital D}{sub {ital NN}}({sup 12}C) (1.000{plus_minus}0.028) is consistent with zero spin-flip probability ({ital S}) for {sup 13}C, where {ital S} (1{minus}{ital D}{sub {ital NN}}). Comparisons are made with results of theoretical calculations reported in the literature. {copyright} {ital 1996 The American Physical Society.}

The elastic scattering observables for 400 MeV [pi][sup [plus minus]] on [sup 28]Si are calculated using a relativistic impulse approximation Kemmer-Duffin-Petiau formalism to calculate the [pi][sup [plus minus]] nucleus optical potential, and the Kemmer-Duffin-Petiau wave equation of motion with the aforementioned potential. The results are compared with recent experiments and with the results of nonrelativistic impulse approximation treatments.

The elastic scattering observables for 400 MeV ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$ on $^{28}\mathrm{Si}$ are calculated using a relativistic impulse approximation Kemmer-Duffin-Petiau formalism to calculate the ${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$ nucleus optical potential, and the Kemmer-Duffin-Petiau wave equation of motion with the aforementioned potential. The results are compared with recent experiments and with the results of nonrelativistic impulse approximation treatments.

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.

Energy-dependent global Dirac optical model potentials are found by fitting proton elastic scattering data in the energy range 20-1040 MeV for C-12, O-16, Ca-40, Zr-90, and Pb-208. Three different energy- and atomic-mass-number-dependent global Dirac optical potentials are also obtained. A number of characteristic features of the potentials are discussed. In addition, the mean free path, the effective mass m(e)*, the Dirac mass M*, and the relativistic energy shift E* are calculated.

In this paper we give the results of a relativistic analysis of elastic and inelastic scattering of 180 MeV antiprotons from C-12. The calculations are performed within a Dirac coupled-channel framework using a collective model for the transition potentials. While the presence of the inelastic data does seem to remove some of the ambiguity in the Dirac optical model potentials, the largest constraint comes from the elastic analyzing power measurements. In the Dirac approach for proton-nucleus scattering, spin observables are very important; this is also true for the determination of the antiproton-nucleus optical potential.