An asymptotic restoration procedure is applied for analyzing bound-state overlap functions, separation energies, and single-nucleon spectroscopic factors by means of a model one-body density matrix emerging from the Jastrow correlation method in its lowest order approximation for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ nuclei. Comparison is made with available experimental data and mean-field and natural orbital representation results. © 1996 The American Physical Society.

In this paper, we present the Hartree-Fock-Bogoliubov model calculations for transition charge densities of even-even ${}_{}{}^{98–112}{}_{}{}^{}\mathrm{Ru}$ nuclei, using the pairing-plus-quadrupole-quadrupole interactions operating in s-d-g-h valence space. It is predicted that the transition charge densities should be able to act as a more sensitive means for clear signature of the shape transitions, which have yet only been looked upon with respect to the changes in the static properties. The static properties calculated from the same model are in good agreement with the available experimental data. © 1996 The American Physical Society.

In inelastic scattering of 22 MeV deuterons from an isotope-separated target of ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$ containing about 2×${10}^{13}$ nuclei in the isomeric ${16}^{+}$ state we observed rotational excitation to the ${17}^{+}$ state at an excitation energy with respect to the isomeric state of 356.5±0.4 keV and weak evidence for the ${18}^{+}$ state at 737±2 keV. We compared the differential cross sections with coupled-channel calculations and with scattering from ${}_{}{}^{178}{}_{}{}^{}\mathrm{Hf}$ ($0^{+}$) and ${}_{}{}^{177}{}_{}{}^{}\mathrm{Hf}$ (7/$2^{\mathrm{-}}$). © 1996 The American Physical Society.

Angular distributions of the 14–17 MeV γ rays from the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,γ) reaction at ${\mathit{E}}_{\mathit{p}}$=450, 402, and 80 keV were measured at 0°≤${\mathrm{\theta }}_{\mathrm{lab}}$≤135°, using a BGO detector and a 28-μg/${\mathrm{cm}}^2$ LiF target. The angular distributions at ${\mathit{E}}_{\mathit{p}}$=450 and 402 keV agree with the previous results by Mainsbridge; at ${\mathit{E}}_{\mathit{p}}$=80 keV the ground-state transition is anisotropic on the order of 20%, confirming recent results by Chasteler et al. © 1996 The American Physical Society.

Inclusive ${\mathrm{\pi }}^{+}$ photoproduction below the Δ(1232) resonance has been measured from H, C, Ca, Sn, and Pb at laboratory angles of 51°, 81°, 109°, and 141° using tagged photons and ΔE-E plastic scintillator telescopes with 17-MeV thresholds. Particle identification involved both the determination of differential energy loss and the detection of the ${\mathrm{\mu }}^{+}$ from the ${\mathrm{\pi }}^{+}$ decay. Double differential cross sections, angular distributions, and total cross sections were obtained for four incident photon energy bins centered at 184, 194, 204, and 213 MeV. Comparisons are made to both theoretical predictions and previous data sets. Ratios of nuclear cross sections to those obtained from the proton are extracted, and the features of these ratios are discussed. © 1996 The American Physical Society.

Fission fragment anisotropies and mass distributions have been measured to high accuracy, over a wide range of angles, for the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ + ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ reaction. The bombarding energies spanned the fusion barrier distribution, in steps of 1 MeV. Fission following transfer reactions was rejected by making use of the deduced velocity vectors of the fissioning nuclei. The resulting mass distributions for full momentum transfer fission show a small but significant skewness, which increases as the beam energy falls through the fusion barrier region, displaying a similar energy dependence as the fission fragment angular anisotropies. This is conclusive evidence for the interpretation that collisions with the tips of the deformed ${}_{}{}^{238}{}_{}{}^{}\mathrm{U}$ target nuclei lead to quasifission, while collisions with the sides result in fusion-fission. © 1996 The American Physical Society.

Evaporation-residue and transfer reaction cross sections have been measured for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{108,110}$Pd and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{113,115}$In. The residual nuclei were detected and identified by off-line observation of the γ rays emitted in their radioactive decays. The 3n evaporation channel is the dominant decay mode following the fusion of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{110}$Pd and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{115}$In at sub- and near-barrier energies, and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{108}$Pd and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{113}$In at bombarding energies just above the Coulomb barrier. The experimental evaporation-residue excitation functions are compared with calculations obtained using simplified coupled-channel and statistical models. In these calculations it is not necessary to include transfer channels to explain the data in the case of ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{110}$Pd and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{108}$Pd but they must be taken into account for ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{115}$In and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$${+}^{113}$In. © 1996 The American Physical Society.

Double-differential cross sections for fast neutron-induced triton and alpha-particle production on carbon are reported at three incident neutron energies: 42.5, 62.7, and 72.8 MeV, complementing our previous results for proton and deuteron emissions. Angular distributions were measured at laboratory angles between 20° and 160° in steps of 10°. Procedures for data taking and data reduction are described. Results for double-differential, energy-differential, and total cross sections are presented. The measurements are compared to existing data and to nuclear model calculations which include preequilibrium and equilibrium decay mechanisms. © 1996 The American Physical Society.

The recent fragmentation data for central collisions of gold on gold are even qualitatively different from those for central collisions of argon on scandium. The latter can be fitted with a lattice gas model calculation. Effort is made to understand why the model fails for gold on gold. The calculation suggests that the large Coulomb interaction which is operative for the larger system is responsible for this discrepancy. This is demonstrated by mapping the lattice gas model to a molecular dynamics calculation for disassembly. This mapping is quite faithful for argon on scandium but deviates strongly for gold on gold. The molecular dynamics calculation for disassembly reproduces the characteristics of the fragmentation data for both gold on gold and argon on scandium. © 1996 The American Physical Society.

A semiclassical model of neutron resonance reactions has been developed, where time evolution and the recurrence of the compound nuclear system are explicitly considered. We have derived an average recurrence frequency of a multiple oscillator system as a function of the total excitation energy and oscillator number involved, where the tolerable phase angle error is assumed to be 1 rad. On the compound nuclei formed by neutron resonances, we have deduced effective oscillator numbers M and nuclear temperatures T. These values agree well with the traditional ones. As regards the time evolution of the compound nucleus, we have defined the ‘‘coalescent phase’’ where the neutron density is high on the target nuclear surface in a time duration ∼${10}^{\mathrm{-}21}$ s. It appears repeatedly like a pulse array with an interval of recurrence time, and continues during lifetime of resonance ∼${10}^{\mathrm{-}14}$ s. Fourier transforming the coalescent phases, we have found the S matrix, in which neutron reaction cross sections can be derived. They consist of equidistant fine structure resonances, with an envelope of a giant resonance. Triple uncertainty relations between energy and time were derived. Using this model, a smooth shift from the isolated resonance region to the continuum region could be predicted. © 1996 The American Physical Society.

We have reanalyzed elastic α scattering data on many target nuclei from ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ up to ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ over a wide range of energies. Using double-folded potentials we have obtained excellent agreement between the experimental scattering data and our optical model calculations. In addition, bound state properties have been calculated successfully. A systematic behavior of the energy and mass dependence of the strengths of the real and imaginary potentials has been found. © 1996 The American Physical Society.

We compute the hard photon production rate of a chemically nonequilibrated quark-gluon plasma. We assume that the plasma is already thermally equilibrated, i.e., describable by a temperature, but with a phase-space distribution that deviates from the Fermi-Bose distribution by a time dependent factor (fugacity). The photon spectrum is obtained by integrating the photon rate over the space-time evolution of the quark-gluon plasma. Some consequences for ultrarelativistic heavy ion collisions are discussed. © 1996 The American Physical Society.

We propose a parameter-free method to determine the temperature of a thermalized state in relativistic nuclear interactions, using the experimental ${\mathrm{\mu }}_{\mathit{q}}$/T and ${\mathrm{\mu }}_{\mathit{s}}$/T values, obtained from strange particle ratios. The hadron gas formalism and strangeness neutrality are employed to relate the quark-chemical potential ${\mathrm{\mu }}_{\mathit{q}}$ and ${\mathrm{\mu }}_{\mathit{s}}$ to the temperature and thus determine its value at chemical freeze-out. This temperature, together with the inverse slope parameter from ${\mathit{m}}_{\mathit{T}}$ distributions, enable the determination of the transverse flow velocity of the fireball matter, thus disentangling the thermal and flow effects. We study several nucleus-nucleus interactions from AGS and SPS and obtain the temperature, transverse flow velocity, and quark-chemical potentials. Extrapolating the systematics we predict the values of these quantities for ongoing and future experiments at AGS, SPS, and RHIC. We discuss the possibility of reaching the conditions for quark deconfinement and QGP formation and give distinct and identifiable signature. © 1996 The American Physical Society.

${\mathit{g}}_{\mathit{KN}}$Λ and ${\mathit{g}}_{\mathit{KN}\mathrm{\Sigma }}$ are calculated using a QCD sum rule motivated method used by Reinders, Rubinstein, and Yazaki to extract hadron couplings to Goldstone bosons. The SU(3) symmetry breaking effects are taken into account by including the contributions from the strange quark mass and assuming different values for the strange and the up-down quark condensates. We find ${\mathit{g}}_{\mathit{KN}}$Λ/√4π=-1.96 and ${\mathit{g}}_{\mathit{KN}\mathrm{\Sigma }}$/√4π=0.33. © 1996 The American Physical Society.

The present work is an extension of a previous study of the nucleon-nucleon interaction based on the chromodielectric soliton model. The former approach was static, leading to an adiabatic potential. Here we perform a dynamical study in the framework of the generator coordinate method. In practice we derive an approximate Hill-Wheeler differential equation and obtain a local nucleon-nucleon potential as a function of a mean generator coordinate. This coordinate is related to an effective separation distance between the two nucleons by a Fujiwara transformation. This latter relationship is especially useful in studying the quark substructure of light nuclei. We investigate the explicit contribution of the one-gluon exchange part of the six-quark Hamiltonian to the nucleon-nucleon potential, and we find that the dynamics are responsible for a significant part of the short-range N-N repulsion. © 1996 The American Physical Society.

We calculate the tensor describing ρ-ω mixing making use of an extended Nambu–Jona-Lasinio (NJL) model that we have developed in recent years. We use the definition of the ρ and ω fields that arises upon a momentum-space bosonization of the extended NJL model. A quantity of interest is the on-shell (${\mathit{q}}^2$=${\mathit{m}}_{\mathrm{\omega }}^2$) matrix element that describes the coupling of the ρ and ω fields, 〈ρ‖${\mathit{H}}_{\mathit{SB}}$‖ω〉. That quantity has been determined to be 〈ρ‖${\mathit{H}}_{\mathit{SB}}$‖ω〉=-(4520±600) ${\mathrm{MeV}}^2$ in a study of the two-pion decay of the ω meson. If corrected for an electromagnetic process, the strong interaction contribution is 〈ρ‖${\mathit{H}}_{\mathit{SB}}^{\mathrm{st}}$‖ω〉=-(5130±600) ${\mathrm{MeV}}^2$. Our calculation of 〈ρ‖${\mathit{H}}_{\mathit{SB}}^{\mathrm{st}}$‖ω〉 is sensitive to the difference of the current quark masses, ${\mathit{m}}_{\mathit{d}}^0$-${\mathit{m}}_{\mathit{u}}^0$. Our results may be put into agreement with the data, if we use ${\mathit{m}}_{\mathit{d}}^0$-${\mathit{m}}_{\mathit{u}}^0$=3.1±0.3 MeV. (That value is reduced to ${\mathit{m}}_{\mathit{d}}^0$-${\mathit{m}}_{\mathit{u}}^0$=2.7±0.3 MeV, if we use a subtraction scheme that causes the polarization tensor to be equal to zero at ${\mathit{q}}^2$=0.) The momentum-space bosonization procedure naturally leads to momentum-dependent coupling constants, ${\mathit{g}}_{\mathrm{\omega }\mathit{qq}}$(${\mathit{q}}^2$) and ${\mathit{g}}_{\mathrm{\rho }\mathit{qq}}$(${\mathit{q}}^2$). The value of these constants increases by about a factor of √2, when one goes from ${\mathit{q}}^2$=${\mathit{m}}_{\mathrm{\omega }}^2$ (or ${\mathit{q}}^2$=${\mathit{m}}_{\mathrm{\rho }}^2$) to ${\mathit{q}}^2$=0. The values at ${\mathit{q}}^2$=0 reproduce the strength of the relevant components of the nucleon-nucleon interaction at small momentum transfer, as was demonstrated in an earlier work. © 1996 The American Physical Society.

We examine the role played by the ${\mathrm{U}}_{\mathit{A}}$(1) symmetry-breaking ’t Hooft interaction in scalar mesons, using the two- and three-flavor versions of the Nambu and Jona-Lasinio model. We first examine the two-flavor case within the Hartree + random phase approximation in order to (a) develop the formalism necessary for the treatment of the three-flavor case, and (b) to see if the scalar sector can be treated as ideally mixed, i.e., if the u,d quark mesons completely separate themselves from the ones with strange quarks. Then we calculate the scalar and pseudoscalar meson mass spectra in the three-flavor model within the mean-field approximation and establish relations between the scalar and pseudoscalar meson masses. This analysis leads to a new approximate sum rule that is a consequence of ${\mathrm{U}}_{\mathit{A}}$(1) breaking in the Nambu–Jona-Lasinio (NJL) model: ${\mathit{m}}_{{\mathrm{\eta }}^{\prime }}^2$+${\mathit{m}}_{\mathrm{\eta }}^2$-2${\mathit{m}}_{\mathit{K}}^2$≃ -${\mathit{m}}_{{\mathit{f}}_0}^{\prime 2}$-${\mathit{m}}_{{\mathit{f}}_0}^2$ +2${\mathit{m}}_{{\mathit{K}}_0^{\mathrm{*}}}^2$, where η′,η,K are the observed pseudoscalar mesons, ${\mathit{K}}_0^{\mathrm{*}}$ is the strange scalar meson at 1430 MeV, and ${\mathit{f}}_0$,${\mathit{f}}_0^{\prime }$ are ‘‘the eighth and the ninth’’ scalar mesons. It states that the mass splitting between the scalar singlet and the octet is of the same size as, but of opposite sign to, the corresponding splitting among the pseudoscalars. We discuss the large-${\mathit{N}}_{\mathit{C}}$ limit of our results. Two of our partial results leading to the sum rule are consistent with the large-${\mathit{N}}_{\mathit{C}}$ limit results of QCD, though one of them is not required by QCD.

Although this paper is meant primarily to be a demonstration of relevance of ${\mathrm{U}}_{\mathit{A}}$(1) breaking to scalar mesons in the NJL model, we can and do make definite and apparently sensible predictions of the scalar masses but their decay widths are only in qualitative agreement with experiment. In the process we have extended Eguchi and Sugawara’s ‘‘bosonization’’ method to the SU(3) NJL model and found that it is ‘‘equivalent’’ to the M. Lévy’s [Nuovo Cimento A 52, 23 (1967)] SU(3) linear σ model with coupling constants specified in the text of the present paper. © 1996 The American Physical Society.

The neutron capture cross sections of the stable cerium isotopes 136, 138, 140, and 142 have been measured relative to that of gold by means of the activation method. The samples were irradiated in a quasistellar neutron spectrum for kT=25 keV using the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$(p,n${)}^7$Be reaction near threshold. Variation of the experimental conditions in different activations and the use of different samples allowed for the reliable determination of corrections and the evaluation of systematic uncertainties. The resulting stellar cross sections can be given with uncertainties between 3% and 7%. The present data for ${}_{}{}^{136}{}_{}{}^{}\mathrm{Ce}$ and ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ce}$ are the first experimental information in this mass region of relevance for p-process studies to our knowledge, whereas the new ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ cross section allowed to resolve a previous discrepancy. The experimental results are complemented by a set of calculated cross sections for all cerium isotopes from ${}_{}{}^{132}{}_{}{}^{}\mathrm{Ce}$ to ${}_{}{}^{142}{}_{}{}^{}\mathrm{Ce}$ as well as for ${}_{}{}^{141}{}_{}{}^{}\mathrm{Pr}$, ${}_{}{}^{142}{}_{}{}^{}\mathrm{Pr}$, and ${}_{}{}^{143}{}_{}{}^{}\mathrm{Pr}$. The improved cross sections were used in an updated s-process analysis of the Ce-Pr-Nd region that included the small branchings at ${}_{}{}^{141}{}_{}{}^{}\mathrm{Ce}$ and ${}_{}{}^{142}{}_{}{}^{}\mathrm{Pr}$. The consequences of the resulting s abundances are discussed with respect to isotopic anomalies in meteoritic neodymium as well as for the r- and p-process residuals. © 1996 The American Physical Society.

Inclusive and semi-inclusive neutrino-nucleus reaction cross sections at intermediate energies (20 MeV≤${\mathit{E}}_{\nu }$≤500 MeV) are calculated throughout the Periodic Table for the most interesting nuclei from an experimental point of view. The method used had previously proved to be very accurate in calculating the inclusive reaction cross section for light nuclei ${(}^{12}$C and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$) and in the study of other similar processes and has been further improved to deal with low energy neutrinos. The electron neutrino (${\nu }_{\mathit{e}}$) and muon neutrino (${\nu }_{\mathrm{\mu }}$) cross sections weighted by their energy distributions are also calculated and discussed in conjunction with the existing experimental results at LAMPF and the KARMEN Collaboration. © 1996 The American Physical Society.

We study the equation of state of hyperon-rich matter in neutron stars using an extended relativistic mean-field model. We take special care of the recently proposed nonlinear behavior of the vector field providing a much better agreement with Dirac-Brückner calculations. The hyperon-hyperon interaction is also implemented by introducing additional meson exchanges. With these new terms we avoid the instability found at high densities while keeping the excellent description for finite nuclear systems. We also demonstrate within the mean-field approach that the presence of hyperons inside neutron stars on one hand and the hyperon-hyperon interactions on the other hand make the onset of kaon condensation less favorable. © 1996 The American Physical Society.