The possible formation of a $\rho$-nucleus bound state is studied within the framework of the Walecka model. Bound states are found in different nuclei ranging from ${}^3\mathrm{He}$ to ${}^{208}\mathrm{Pb}.$ These bound states may have a direct bearing on the recent experiments on the photoproduction of $\rho$ meson in the nuclear medium.

Measurements of the total reaction cross section for ${}^{12-16}\mathrm{C},$ ${}^{14-17}\mathrm{N},$ and ${}^{16-18}\mathrm{O}$ on carbon target at intermediate energies were performed on the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. A larger enhancement of ${\sigma }_R$ for ${}^{15}\mathrm{C}$ was observed than for its neighbors. Evidence for possible anomalous nuclear structure in ${}^{15}\mathrm{C}$ was revealed in the analysis of the total reaction cross section in terms of the difference factor $d.\mathrm{}$

We extend a semiclassical model of transfer reactions to the case in which one of the collision partners is a vibrational nucleus. The model is applied to one- and two-proton stripping reactions in the ${}^{37}\mathrm{Cl}{+}^{98}\mathrm{Mo}$ system, for which a rapid transition from normal to anomalous slope in the two proton transfer reaction at energies around the Coulomb barrier is experimentally observed. This behavior is satisfactorily reproduced by the present extension of the model.

A dynamical approach is developed to predict the $\pi N$ scattering amplitudes starting with the constituent quark models. The first step is to apply a variational method to solve the three-quark bound state problem. The resulting wave functions are used to calculate the $N^{*}\to \pi N,\eta N,\pi \Delta$ vertex functions by assuming that the $\pi$ and $\eta$ mesons couple directly to quarks. These vertex functions and the predicted baryon bare masses then define a Hamiltonian for $\pi N$ reactions. We apply a unitary transformation method to derive from the constructed Hamiltonian a multichannel and multiresonance reaction model for predicting the $\pi N$ scattering amplitudes up to $W=2\mathrm{}$ GeV. With the parameters constrained by the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ excitation, we have examined the extent to which the $\pi N$ scattering in the $S_{11}$ channel can be described by constituent quark models based on one-gluon-exchange or one-meson exchange mechanisms. It is found that the data seem to favor the spin-spin interaction due to one-meson exchange and the tensor interaction due to one-gluon exchange. A phenomenological quark-quark potential has been constructed to reproduce the $S_{11}$ amplitude.

Exclusive transverse flow in $\mathrm{Au}+\mathrm{Au}$ reactions, calculated within the BNV transport model with a momentum dependent microscopic mean field+phase space coalescence model, is presented and discussed in comparison with the data from the EOS experiment, taken at LBNL Bevalac. The mean field has been obtained in the framework of the Brueckner theory up to the third order in the $G$ matrix. The calculated exclusive flow for protons, deuterons, and alphas follow the observed experimental trend versus the energy and the fragment mass.

A separation of the longitudinal and transverse ${}^{12}\mathrm{C}{(e,e}^{\prime }p)$ cross sections in the quasifree region has been performed in parallel kinematics at $Q^2$ of 0.64 and 1.8 ${\mathrm{GeV}}^2$ for initial proton momentum $<80\mathrm{}$ MeV. The separated transverse and longitudinal spectral functions at $Q^2=0.64\mathrm{}{\mathrm{GeV}}^2$ show significant differences for missing energy between 25 and 60 MeV indicating a breakdown in the single nucleon knockout picture. The transverse spectral functions exhibit definite momentum transfer dependence.

Exclusive differential cross sections of virtual bremsstrahlung in proton-proton scattering below the pion-production threshold have been measured and their leptonic-angle dependence was exploited to determine all six nucleon-nucleon electromagnetic response functions in the timelike region. The data are compared to a low-energy calculation and a fully relativistic microscopic model. Over the entire phase space the low-energy calculation gives a better description of the cross sections than does the microscopic model. At large virtual-photon masses both models are unable to account for the observed strength of the interference response functions.

The $\beta$ decay of ${}^9\mathrm{C}$ ${(T}_{1/2}=126.5\mathrm{}\hspace{0.5em}\mathrm{ms})$ has been studied in two experiments observing about $15\times {10}^7$ and $8\times {10}^7$ decays, respectively, at the TISOL facility at TRIUMF; different detector configurations were employed in the two experiments. In this first of two papers, the two experimental setups are described, as well as data analysis and a phenomenological approach to deducing branching ratios to and from states in ${}^9\mathrm{B}.$ In the experiments single spectra, and double and triple coincidence spectra, were recorded. Several states in ${}^9\mathrm{B}$ were observed; $\beta$-branching ratios to these states, and particle decay channels from these states, are reported. In particular, secondary decays into the ${}^5\mathrm{Li}$ and ${}^8\mathrm{Be}$ ground states were observed. With the inclusion of a considerable continuum and additional states, fair agreement with the reported ${}^9\mathrm{Li}\log \mathrm{ft}$ values is found with a phenomenological approach for deducing the branching ratios. To extend the discussion, in a second, forthcoming paper, a multichannel, multistate R-matrix analysis of these data will be described.

The hadron and string cascade model JPCIAE, which is based on the LUND string model, especially the PYTHIA event generator, is used to study both inclusive photon production and direct photon production in $200A$ GeV S+Au central collisions. The model takes into account in a consistent way the photon production from the partonic QCD scattering processes, the hadronic final-state interaction, and hadronic decays. The results of the JPCIAE model reproduce successfully both the WA80 data on the transverse momentum dependent upper limits of direct photon yields and the WA93 data on low $p_T$ inclusive photon distribution. The photon production from different decay channels is investigated for both direct and inclusive photons.

The decay channels and the half-life of the proposed anomalously low-energy nuclear isomer ${}^{229}{\mathrm{Th}}^m{(3/2\mathrm{}}^{+},3.5\mathrm{}\pm 1.0\hspace{0.5em}\mathrm{eV})$ in a dielectric and in metals are discussed. The preferred decay channel in wide energy-gap dielectrics is via nuclear $\gamma$ emission in the optical range. The isomer’s half-life lies in the range 10 min–1 h in ${}^{229}{\mathrm{ThO}}_2$ for the spectral range ${\omega }_N=4.5\mathrm{}–2.5\mathrm{eV}.$ Nonradiative decay channels dominate in metals. A two-step experimental scheme is developed. The first step is the excitation of the low-energy isomeric level by synchrotron radiation via the 29- and 72-keV levels, and precise measurement of the wave length of the low-energy nuclear transition in ${}^{229}{\mathrm{ThO}}_2.$ The second step is the excitation of a large number of the isomeric nuclei ${}^{229}{\mathrm{Th}}^m{(3/2\mathrm{}}^{+},3.5\mathrm{}\pm 1.0\hspace{0.5em}\mathrm{eV})$ from the ground state by laser radiation in thorium dioxide, and investigation of the $\alpha$ decay of the isomeric level.

The density dependent relativistic hadron field (DDRH) theory, previously introduced and applied to isospin nuclei, is extended to hypernuclei by including the octet hyperons. Infinite matter Dirac-Brueckner theory for octet baryons and the derivation of in-medium DDRH baryon-meson vertices is discussed. From the properties of Dirac-Brueckner interactions it is found that hyperon and nucleon self-energies and vertices are related by the ratios of free space coupling constants. This leads to simple scaling laws for the in-medium hyperon and nucleon vertices. The model is applied in relativistic DDRH mean-field calculations to single Λ nuclei. Free space $N\Lambda$ T-matrix results are used for the scalar vertex. As the only free parameter the hyperon vector vertex scaling factor is adjusted to a selected set of hypernuclear data. Spectroscopic data of single Λ hypernuclei over the full mass range are well described. A reduction of the Λ spin-orbit splitting is found to be related closely to the medium dependence of scalar and vector interactions.

The role of the breakup process of the weakly bounded light projectile ${}^9\mathrm{Be},$ on the near barrier fusion reaction and elastic scattering, is investigated by two different approaches. The fusion cross sections for the ${}^9\mathrm{Be}{+}^{64}\mathrm{Zn}$ system were compared with the ones from other similar systems (the ${}^{16}\mathrm{O}{+}^{64}\mathrm{Zn}$ and ${}^{14}\mathrm{N}{+}^{59}\mathrm{Co}).\mathrm{}$ The measurement of the elastic scattering for this system was also used to study the threshold anomaly. There are indications that the fusion suppression due to the ${}^9\mathrm{Be}$ breakup is not important for the interaction of ${}^9\mathrm{Be}$ with this medium mass target.

The single-nucleon knockout reactions ${}^9\mathrm{Be}{(}^{14}\mathrm{B}{,}^{13}\mathrm{B}+\gamma )X$ and ${}^{197}\mathrm{Au}{(}^{14}\mathrm{B}{,}^{13}\mathrm{B}+\gamma )X,$ at an incident energy of 60 MeV per nucleon, have been used to probe the structure of ${}^{14}\mathrm{B}$ and of the core fragment ${}^{13}\mathrm{B}.$ A dominant $2s$ configuration is deduced for the neutron in the ground state of ${}^{14}\mathrm{B}.$ The longitudinal momentum distribution for this state is consistent with “neutron halo” structure. Spin assignments for ${}^{13}\mathrm{B}$ excited states at 3.48 and 3.68 MeV are proposed based on the observed spectroscopic factors for one-neutron removal.

A method for incorporating the effect of the resonant continuum into Hartree-Fock+BCS equations is proposed. The method is applied for the case of a neutron-rich nucleus calculated with a Skyrme-type force plus a zero-range pairing interaction and the results are compared with Hartree-Fock-Bogoliubov calculations. It is shown that the widths of resonant states have an important effect on the pairing properties of nuclei close to the drip line.

The asymmetry between proton and neutron numbers in a nucleus is viewed as a consequence of the spontaneous symmetry breaking of the isospin symmetry. The signatures of this effect, as it was suggested by Danchev, Khanna, and Umezawa and co-workers, may have been seen already in the energetics of the nuclear isobaric analog resonance state and in the systematic of double-odd double-even mass differences. In order to account for finite size effects, not included in Umezawa’s approach, we have calculated the mean field term of the Hamiltonian in a realistic nuclear single-particle basis. The nonvanishing value of the $I_3$ current in the nonperturbative vacuum is explained in terms of $\rho$ meson exchange.

Parity-violating elastic electron scattering on neutron-rich nuclei is described in the framework of relativistic mean-field theory. Self-consistent ground state density distributions of Ne, Na, Ni, and Sn isotopes are calculated with the relativistic Hartree-Bogoliubov model, and the resulting neutron radii are compared with available experimental data. For the elastic scattering of 850 MeV electrons on these nuclei, the parity-violating asymmetry parameters are calculated using a relativistic optical model with inclusion of Coulomb distortion effects. The asymmetry parameters for chains of isotopes are compared, and their relation to the Fourier transforms of neutron densities is studied. It is shown that parity-violating asymmetries are sensitive not only to the formation of the neutron skin, but also to the shell effects of the neutron density distribution.

The ${}^{12}\mathrm{C}{(}^6\mathrm{Li}\to ,\alpha {)}^{14}\mathrm{N}$ reaction cross section, and analyzing powers to the $2^{+}$ (7.03 MeV) natural parity state of ${}^{14}\mathrm{N}$ have been studied by coupled reaction channels calculations that include deuteron cluster transfer from the $1^{+}$ ground and $3^{+},$$2^{+},1^{+}$ spin-orbit triplet excited states in ${}^6\mathrm{Li}$ as well as from the first $2^{+}$ excited state in ${}^{12}\mathrm{C}$ to assess the role played by these inelastic transfers. This natural parity transition was chosen for detailed study because the number of L transfers allowed is more limited than for transfers to unnatural parity states. Inclusion of the transfer from the $1^{+}$ excited state of ${}^6\mathrm{Li}$ is especially vital for understanding the tensor analyzing power data $T_{21}.$ The same analysis was then applied to the transfers to the $1^{+}$ ground and 3.95 MeV states in ${}^{14}\mathrm{N}.$ Failure to describe the shape of the ground state angular distribution motivated its remeasurement and its anomalous shape was confirmed. The present work suggests that single nucleon sequential transfer might be the dominant mode for the ground state transfer.

Standard solution methods are known to be applicable to Faddeev-type momentum space integral equations for three-body transition amplitudes, not only for purely short-range interactions but also, after suitable modifications, for potentials possessing Coulomb tails provided the total energy is below the three-body threshold. For energies above that threshold, however, long-range Coulomb forces have been suspected to give rise to such severe singularities in the kernels, even of the modified equations, that their compactness properties are lost. Using the rigorously equivalent formulation in terms of an effective-two-body theory we prove that, for all energies, the nondiagonal kernels occurring in the integral equations which determine the transition amplitudes for all binary collision processes, possess on and off the energy shell only integrable singularities, provided all three particles have charges of the same sign, i.e., all Coulomb interactions are purely repulsive. Hence, after a few iterations these kernels become compact. The case of the diagonal kernels is dealt with in a subsequent paper.

High-spin states have been studied in neutron-deficient ${}_{\hspace{0.5em}52}^{109}\mathrm{Te},$ populated through the ${}^{58}\mathrm{Ni}{(}^{58}\mathrm{Ni},\alpha 2pn)$ reaction at 250 MeV. The GAMMASPHERE $\gamma -\mathrm{ray}$ spectrometer has been used in conjunction with the MICROBALL charged-particle detector and 15 neutron detectors in order to select weakly populated evaporation residues. New band structures have been established in ${}^{109}\mathrm{Te}.$ Measured $B\left(E1\mathrm{}\right)\mathrm{}$ strengths are discussed in terms of octupole correlations in this mass region. In addition, possible noncollective oblate states have been identified.