D.G. Madland

Nuclear Ground State Observables and QCD Scaling in a Refined Relativistic Point Coupling Model

We present results obtained in the calculation of nuclear ground state properties in relativistic Hartree approximation using a Lagrangian whose QCDscaled coupling constants are all natural (dimensionless and of order 1). Our model consists of four-, six-, and eight-fermion point couplings (contact interactions) together with derivative terms representing, respectively, two-, three-, and four-body forces and the finite ranges of the corresponding mesonic interactions. The coupling constants have been determined in a self-consistent procedure that solves the model equations for representative nuclei simultaneously in a generalized nonlinear least-squares adjustment algorithm. The extracted coupling constants allow us to predict ground state properties of a much larger set of even-even nuclei to good accuracy. The fact that the extracted coupling constants are all natural leads to the conclusion that QCD scaling and chiral symmetry apply to finite nuclei.

Total prompt energy release in the neutron-induced fission of 235U, 238U, and 239Pu

Abstract This study addresses, for the first time, the total prompt energy release and its components for the fission of 235 U, 238 U, and 239 Pu as a function of the kinetic energy of the neutron inducing the fission. The components are extracted from experimental measurements, where they exist, together with model-dependent calculation, interpolation, and extrapolation. While the components display clear dependencies upon the incident neutron energy, their sums display only weak, yet definite, energy dependencies. Also addressed is the total prompt energy deposition in fission for the same three systems. Results are presented in equation form. New measurements are recommended as a consequence of this study.

QCD scales in finite nuclei

The role of QCD scales and chiral symmetry in finite nuclei is examined. The Dirac-Hartree mean-field coupling constants of Nikolaus, Hoch, and Madland (NHM) are scaled in accordance with the QCD-based prescription of Manohar and Georgi. Whereas the 9 empirically based coupling constants of NHM span 13 orders of magnitude, the scaled coupling constants are almost all {ital natural}, being dimensionless numbers of order 1. We argue that this result provides good evidence that QCD and chiral symmetry apply to finite nuclei. {copyright} {ital 1996 The American Physical Society.}

Elastic scattering of 0.8-GeV protons from C12, Ni58, and Pb208

Differential cross sections for elastic scattering of 0.8-GeV protons from /sup 12/C, /sup 58/Ni, and /sup 208/Pb have been measured. Preliminary analysis of the data in terms of the Kerman-McManus-Thaler formalism with spin-dependent nucleon-nucleon amplitudes shows sensitivity to details of proton and neutron matter distributions.

Predicting Total Reaction Cross Sections for Nucleon-Nucleus Scattering

Nucleon total reaction and neutron total cross sections to 300 MeV for 12C and 208Pb, and for 65 MeV scattering spanning the mass range, are predicted using coordinate space optical potentials formed by full folding of effective nucleon-nucleon interactions with realistic nuclear ground state densities. Good to excellent agreement is found with existing data.

Coupled-channels effects in 0.8 GeV proton inelastic scattering from 58Ni

Abstract New differential cross sections for 0.8 GeV proton inelastic excitation of the first 2+ and 4+ states in 58Ni are compared with distorted wave Born approximation and coupled-channels predictions. Multistep processes and multi-phonon mixing are both shown to be important in describing the excitation of the 4+ state.

Elastic and inelastic scattering of 800 MeV protons by 58Ni

Abstract Differential cross sections for elastic and inelastic scattering of 800 MeV protons from 58 Ni have been measured to momentum transfers of 4 fm −1 . The elastic scattering data were fit using a phenomenological optical model potential. The inelastic scattering was analyzed in the distorted wave Born approximation (DWBA) to obtain deformation lengths.

Prediction of intermediate-energy neutron scattering observables from a Dirac optical potential

Abstract We construct a global optical potential for intermediate-energy nucleon + 208 Pb scattering using the Dirac phenomenology. Experimental proton elastic differential cross sections, analyzing powers, spin-rotation functions, total reaction cross sections, and neutron total cross sections are used to construct a Dirac potential spanning an energy range of 95 to 300 MeV. Calculations of n + 208 Pb scattering observables are performed and significant differences with predictions and measurements of the corresponding proton scattering observables are found. The origins of the differences are explored by performing calculations using a “gedanken” projectile. The predicted neutron observables are as yet unmeasured and thus have relevance for the newly-constructed intermediate-energy neutron beam facilities.

Adjustment studies in self-consistent relativistic mean-field models

Abstract We investigate the influence of the adjustment procedure and the set of measured observables on the properties and predictive power of relativistic self-consistent mean-field models for the nuclear ground state. These studies are performed with the point-coupling variant of the relativistic mean-field model. We recommend optimal adjustment algorithms for the general two-part problem and we identify various trends and dependencies as well as deficiencies of current models. Consequences for model improvements are presented.

Influence of fission fragment excitation energy on prompt fission neutron observables

We have implemented a Monte‐Carlo simulation of the statistical decay of fission fragments by sequential neutron emission. In this presentation, we report on some numerical results obtained for the spontaneous fission of 252Cf and neutron‐induced fission of 235U at 0.53 MeV neutron energy, and compare them to the results of the Los Alamos model for the calculation of the average number of prompt fission neutrons v and the prompt fission neutrons spectrum N(E). Within this approach, we also calculate neutron multiplicity distributions P(v) as well as neutron‐neutron correlations such as the full matrix v(A, T K E). Two assumptions for partitioning the total available excitation energy among the light and heavy fragments are considered. The influence of the fission fragments excitation energy for low total kinetic energies on prompt neutron energy spectrum, multiplicity distributions and v(A, T K E) is discussed.