S. Hama

Neutron densities from a global analysis of medium-energy proton nucleus elastic scattering

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.

Pion-nucleus scattering at medium energies with densities from chiral effective field theories

Abstract Recently developed chiral effective field theory models provide excellent descriptions of the bulk characteristics of finite nuclei, but have not been tested with other observables. In this work, densities from both relativistic point-coupling models and mean-field meson models are used in the analysis of meson-nucleus scattering at medium energies. Elastic scattering observables for 790 MeV/ c π ± on 208 Pb are calculated in a relativistic impulse approximation, using the Kemmer-Duffin-Petiau formalism to calculate the π ± nucleus optical potential.

Reaction cross sections for 65 MeV protons on targets from 9Be to 208Pb

Abstract Reaction cross sections for 65.5 MeV protons have been measured for 9 Be, 12 C, 16 O, 28 Si, 40 Ca, 58,60 Ni, 112.116.118.120.124 Sn, and 208 Pb. The results are compared with optical model predictions using relativistic global potentials.

Theoretical and Experimental K+ + Nucleus Total and Reaction Cross Sections from the KDP-RIA Model

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 + + 6 Li, 12 C, 28 Si and 40 Ca 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.

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.

Nucleon-Nucleus Scattering and Dirac Phenomenology: What We Have Learned and What Remains

It is now generally recognized that the Dirac equation is a viable alternative to the usual Schroedinger 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 40Ca, 48Ca and 208Pb 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, Rp and Rn, and the neutron skin thickness, Sn = Rn - Rp.

Erratum to: Pion-nucleus scattering at medium energies with densities from chiral effective field theories: [Phys. Lett. B 427 (1998) 231–234]

Recently developed chiral effective field theory models provide excellent descriptions of the bulk characteristics of finite nuclei, but have not been tested with other observables. In this work, densities from both relativistic point-coupling models and mean-field meson models are used in the analysis of meson-nucleus scattering at medium energies. Elastic scattering observables for 790 MeV/

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

c

Global optical potentials for elastic p+ /sup 40/Ca scattering using the Dirac equation

\pi^{\pm}