C. E. Price

Relativistic mean field theory for nuclei

Abstract The phenomenology of relativistic mean field theory of nuclei is discussed for general scalar potential functions U ( φ ) with a minimum at zero scalar field φ = 0. The cubic-plus-quartic scalar self-interaction model U 34 is discussed as an important special case. We obtain general conditions on U required by the saturation properties including the incompressibility coefficient K . The effective mass M ∗ is uniquely related to the vector coupling. The pathologies of the U 34 model are discussed and modifications are proposed which cure the model when the quartic term is negative as phenomenologically required. It is argued that the equation of state (at T = 0) is effectively independent of the form of U if the parameters are adjusted to a given K, M ∗ , and that the phenomenology of finite nuclei, in particular the spin-orbit splitting in light nuclei, determines M ∗ ≈ 0.6 M essentially independently of U . The resulting (stiff) e.o.s. is then determined within narrow limits independently of the form of U .

Searching for the Berry phase effect with two-particle transfer reactions☆

Abstract Recent structure calculations of two-particle transfer amplitudes between rotating heavy nuclei have predicted strong variations that are related to Berrys topological phase. In this work these amplitudes are incorporated into a new method for calculating the reaction process that allows one to study the consequences of the structure variations on the observable cross sections.

Vacuum polarization currents in finite nuclei

Self-consistent relativistic Hartree calculations of odd-{ital A} nuclei, including vacuum polarization, are presented. The contribution to the baryon current from the deformed Dirac sea is calculated using a derivative expansion. This vacuum current does not affect magnetic moments; however, at intermediate momentum transfers it tends to cancel the current from the deformed occupied core, as expected from the random-phase approximation response in nuclear matter. Wave function mixing for the valence state, which arises in the self-consistent solution but not in random-phase approximations, significantly affects both Dirac and anomalous currents.

Pair-transfer with heavy deformed nuclei at high spins☆

Abstract The sudden limit for rotational excitation combined with a macroscopic description of the pair-transfer process allows calculations to be carried out for transfer reactions to high-spin states.

Two-particle transfer reactions with heavy-deformed nuclei

Abstract Detailed calculations of two-particle transfer reactions on heavy, deformed nuclei are carried out within the framework of the macroscopic model for pair transfer and the sudden limit for rotational excitation. The marked structure that appears as a general feature of the angular distributions is explained as an interference of amplitudes that correspond to different orientations of the deformed nucleus. A comparison to recent data supports the existence of this structure.

Meson exchange current corrections to magnetic moments in quantum hadro-dynamics

Abstract We have calculated pion exchange current corrections to the magnetic moments of closed shell ±1 particle nuclei near A=16 and 40 within the framework of quantum hadro-dynamics (QHD). We find that the correction is significant and that, in general, the agreement of the QHD isovector moments with experiment is worsened. Comparisons to previous non-relativistic calculations are also made.

Relativistic nuclear matter with self-consistent correlation energy

We study relativistic nuclear matter in the [sigma]-[omega] model including the ring-sum correlation energy. The model parameters are adjusted self-consistently to give the canonical saturation density and binding energy per nucleon with the ring energy included. Two models are considered, mean-field theory where we neglect vacuum effects, and the relativistic Hartree approximation where such effects are included but in an approximate way. In both cases we find self-consistent solutions and present equations of state. In the mean-field case the ring energy completely dominates the attractive part of the energy density and the elegant saturation mechanism of the standard approach is lost, namely, relativistic quenching of the scalar attraction. In the relativistic Hartree approach the vacuum effects are included in an approximate manner using vertex form factors with a cutoff of 1--2 GeV, the range expected from QCD. Due to the cutoff, the ring energy for this case is significantly smaller, and we obtain self-consistent solutions which preserve the basic saturation mechanism of the standard relativistic approach.

Transverse response functions in the Delta -resonance region.

We calculate transverse response functions for quasielastic electron scattering at high momentum transfers in a relativistic Hartree approximation in configuration space. We treat the excitation of the [Delta] resonance using its free mass and width. Good agreement with experiment is found in the dip region.

Deformed chiral nucleons

Abstract We compute properties of the nucleon in a hybrid chiral model based on the linear σ-model with quark degrees of freedom treated explicity. In contrast to previous calculations, we do not use the hedgehog ansatz. Instead we solve self-consistently for a state with well defined spin and isospin projections. We allow this state to be deformed and find that, although d- and g-state admixtures in the predominantly s-state single quark wave functions are not large, they have profound effects on many nucleon properties including magnetic moments and gA. Our best fit parameters provide excellent agreement with experiment but are much different from those determined in hedgehog calculations.

Angular momentum selectivity in transfer reactions with heavy deformed nuclei

Abstract It is shown that transfer reaction amplitudes which lead to rotational states at high spin I are built from a constructive superposition of intermediate transitions centered about the value 1 2 I . This feature follows from the general structure of the underlying Coulomb excitation mechanism.