We first show that the pions produced at high $p_T$ in heavy-ion collisions over a wide range of high energies exhibit a scaling behavior when the distributions are plotted in terms of a scaling variable. We then use the recombination model to calculate the scaling quark distribution just before hadronization. From the quark distribution, it is then possible to calculate the proton distribution at high $p_T,$ also in the framework of the recombination model. The resultant $p/\pi$ ratio exceeds one in the $\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{m}\mathrm{e}\mathrm{d}\mathrm{i}\mathrm{a}\mathrm{t}\mathrm{e}-p_T$ region where data exist, but the scaling result for the proton distribution is not reliable unless $p_T$ is high enough to be insensitive to the scale-breaking mass effects.

The momentum diffusion effect of the quark pair due to the multiple scattering in a nuclear medium is studied to explain the observed $J/\psi$ yields in SPS experiments. The resulting suppression is found to be insufficient to reproduce the $J/\psi$ yield in Pb-Pb collisions at SPS energy.

The quantum hadrodynamics model with minimal nucleon-meson couplings is generalized by introducing couplings of mesons to derivatives of the nucleon field in the Lagrangian density. This approach allows an effective description of a state-dependent in-medium interaction in the mean-field approximation. Various parametrizations for the generalized couplings are developed and applied to infinite nuclear matter. In this approach, scalar and vector nucleon self-energies depend on both density and momentum similarly as in the Dirac-Brueckner theory. The Schrödinger-equivalent optical potential is much less repulsive at high nucleon energies as compared to standard relativistic mean-field models and thus agrees better with experimental findings. The derivative couplings in the extended model have significant effects on the properties of symmetric nuclear matter and neutron matter.

We calculate the rapidity distribution and the total cross section of coherent and incoherent $\rho$ production in heavy ion ultraperipheral collisions at ${\sqrt{s}}_{\mathrm{NN}}=130\mathrm{}\mathrm{GeV}$ using the generalized vector dominance model and the Gribov-Glauber approach. We find the coherent cross section of ρ-production ${\sigma }_{\mathrm{coh}}=490\mathrm{}\mathrm{mb}$ compared to ${\sigma }_{\mathrm{coh}}=370\mathrm{}\pm 170\pm 80\mathrm{mb}$ recently reported by the STAR collaboration at RHIC. The predicted cross section inside the acceptance of the experiment, $|y|<~1,$ agrees with the data within half a standard deviation. It is emphasized that measurements of the rapidity distribution will provide a much more stringent test of the used approach.

The Weinberg theorem, the Adler self-consistency zero, the Goldberger and Treiman relation, and the Gell-Mann, Oakes, and Renner relation are proved analytically in full detail for quark models. These proofs are independent of the particular quark-quark interaction, and they are displayed with Feynman diagrams in a compact notation. I assume the ladder truncation, which is natural in the quark model, and also detail the diagrams that must be included in each relation. Off mass shell and finite size effects are included in the quark-antiquark pion Bethe-Salpeter vertices. The axial and vector Ward identities, for the quark propagator and for the ladder, exactly cancel any model dependence.

We reexamine the role of vector meson dominance in nuclear shadowing at low $Q^2.$ We find that models incorporating both vector meson and partonic mechanisms are consistent with both the magnitude and the $Q^2$ slope of the shadowing data.

A new technique for solving three-nucleon scattering equations is developed. It is based on the two-dimensional Chebyshev expansion of the two-baryon transition matrix. Its validity and its effectiveness are demonstrated. The dynamics of the examples is based on a two-baryon potential which allows for the excitation of a nucleon to a Δ isobar; the coupled-channel potential yields an effective three-nucleon force in the three-nucleon system. The purely nucleonic reference potential is the charge-dependent Bonn potential.

Microscopic description of low-lying two-phonon states in even-even nuclei is introduced. The main building blocks are the quasiparticle random-phase approximation (QRPA) phonons. A realistic microscopic nuclear Hamiltonian, based on the Bonn one-boson-exchange potential, is diagonalized in a basis containing one-phonon and two-phonon components, coupled to a given angular momentum and parity. The QRPA equations are directly used in deriving the equations of motion for the two-phonon states. The Pauli principle is taken into account by diagonalizing the metric matrix and discarding the zero-norm states. The electromagnetic transition matrix elements are derived in terms of the metric matrix. The model has been applied to the ${}^{106}\mathrm{Pd}$ and ${}^{108}\mathrm{Pd}$ nuclei, known to contain two-phonon structures. In spite of its simplicity, the model predicts energies and ratios of $B\left(E2\mathrm{}\right)\mathrm{}$ values in a reasonable agreement with the data.

High-spin states in the odd-odd $N=Z$ nucleus ${}_{37}^{74}{\mathrm{Rb}}_{37}$ were studied using the ${}^{40}\mathrm{Ca}{(}^{40}\mathrm{Ca},\alpha np)$ reaction. A previously observed odd-spin $T=0\mathrm{}$ band has been extended to $I^{\pi }{=(31\mathrm{}}^{+})$ and an even-spin $T=0\mathrm{}$ band has been observed for the first time to $I^{\pi }{=(22\mathrm{}}^{+});$ both have a $\pi {(g}_{9/2})\otimes \nu {(g}_{9/2})$ structure. A strongly coupled low-spin $T=0,K=3\mathrm{}$ band has been interpreted as being based upon a $\pi \left[312\right]\frac{3}{2}\otimes \nu \left[312\right]\frac{3}{2}$ configuration. Cranked relativistic Hartree-Bogoliubov calculations, which are corrected for the $t=1\mathrm{}\mathrm{np}$-pair field by restoring isospin symmetry, reproduce the observed spectrum. These new results provide evidence for the existence of an isovector pair field that contains a neutron-proton component with the proper strength for ensuring isospin conservation.

We investigate the nuclear effects on the transverse and longitudinal responses in the deep inelastic region due to the nuclear binding and nucleon Fermi motion. We display the role of the transverse-longitudinal admixture due to the transverse nucleon momentum. The mixing effect is appreciable at small $Q^2$ values, and gradually disappears at large $Q^2$ values. The nuclear modification is then dominated by the binding and Fermi-motion effects which are contained in the spectral function.

A microscopic calculation of near-threshold η-meson production in the reaction $N\overrightarrow{N}\mathrm{NN}\eta$ is presented. It is assumed that the η meson is produced via direct emission and via elementary rescattering processes $M\overrightarrow{N}\eta N$ of various mesons $M=\pi ,\rho ,$ etc. As a novel feature the amplitudes for the latter production mechanism are taken from a multichannel meson-exchange model of the $\pi N$ system developed by the Jülich group which contains explicitly the channels $\pi N,\rho N,\eta N,\sigma N,$ and πΔ. Furthermore, effects of the $\mathrm{NN}$ interaction in the final as well as in the initial state are taken into account microscopically. Our results are compared with recent data from the COSY and CELSIUS accelerator facilities. Reasonable agreement with available near-threshold cross section data for the reactions $p\overrightarrow{p}\mathrm{pp}\eta ,p\overrightarrow{n}\mathrm{pn}\eta ,$ and $p\overrightarrow{n}d\eta$ is found.

The cranked relativistic Hartree-Bogoliubov theory has been applied for a systematic study of the nuclei around ${}^{254}\mathrm{No},$ the heaviest element for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasiparticle, and other properties of these nuclei have been studied with different parametrizations for the effective mean-field Lagrangian. Pairing correlations are taken into account by a finite range two-body force of Gogny type. While the deformation properties are well reproduced, the calculations reveal some deficiencies of the effective forces both in the particle-hole and particle-particle channels. For the first time, the quasiparticle spectra of odd deformed nuclei have been calculated in a fully self-consistent way within the framework of the relativistic mean field (RMF) theory. The energies of the spherical subshells, from which active deformed states of these nuclei emerge, are described with an accuracy better than 0.5 MeV for most of the subshells with the NL1 and NL3 parametrizations. However, for a few subshells the discrepancies reach 0.7–1.0 MeV. In very heavy systems, where the level density is high, this level of accuracy is not sufficient for reliable predictions of the location of relatively small deformed shell gaps. The calculated moments of inertia reveal only small sensitivity to the RMF parametrization and, thus, to differences in the single-particle structure. However, in contrast to lighter systems, it is necessary to decrease the strength of the D1S Gogny force in the pairing channel in order to reproduce the moments of inertia.

The fragment yields from the multifragmentation of gold, lanthanum, and krypton nuclei obtained by the EOS Collaboration are examined in terms of Fisher’s droplet formalism modified to account for Coulomb energy. The critical exponents $\sigma$ and $\tau$ and the surface energy coefficient $c_0$ are obtained. Estimates are made of the pressure-temperature and temperature-density coexistence curve of finite neutral nuclear matter as well as the location of the critical point.

Neutron-induced fission cross sections on ${}^{235}\mathrm{U}$ and ${}^{235}{\mathrm{U}}^m$ targets in the incident neutron energy range $E_n=0.1\mathrm{}–2.5\mathrm{MeV}$ have been deduced from surrogate ${}^{234}\mathrm{U}\mathrm{}(t,pf)\mathrm{}$ measurements. The surrogate $\mathrm{}(t,pf)\mathrm{}$ reaction is used to populate the same compound system as the $\mathrm{}(n,f)\mathrm{}$ reaction before fission, and modeling is used to compensate for the difference in population mechanisms. The calculations presented in this paper improve on previous results by incorporating realistic angular momentum and parity distributions for the $\mathrm{}(t,p)\mathrm{}$ channel, and by updating transmission-coefficient values used in the neutron-capture and emission contributions that compete with the fission process. The results are generally reliable within the 10% systematic uncertainties of the $\mathrm{}(t,pf)\mathrm{}$ data.

The interaction of a nucleus in a low energy electromagnetic excited state with its environment is discussed. First, rigorous evolution equations, for populations only and for both populations and coherences, are derived through a projection operator technique. They are integral equations with time dependent kernels. Indeed, if the width in time of the latter is short enough, the Fermi golden rule is recovered. Otherwise, being computed up to the second order in the coupling constant, they allow the description of the onset of possible Rabi oscillations. But if those are too strong, the second order approximation fails. On the other hand, since the environment is described through its thermal response functions, it is shown how to handle the various situations in a unified way. Particular attention is turned to bound internal conversion and nuclear excitation by electronic transition effects.

Chemical and thermal freeze-out of the hadronic fireball formed in symmetric collisions of light, intermediate-mass, and heavy nuclei at beam energies between $0.8A$ GeV and $2.0A$ GeV are discussed in terms of an equilibrated, isospin-symmetric ideal hadron gas with grand-canonical baryon-number conservation. For each collision system the baryochemical potential ${\mu }_B$ and the chemical freeze-out temperature $T_c$ are deduced from the inclusive ${\pi }^0$ and η yields which are augmented by interpolated data on deuteron production. With increasing beam energy ${\mu }_B$ drops from 800 MeV to 650 MeV, while $T_c$ rises from 55 MeV to 90 MeV. For given beam energy ${\mu }_B$ grows with system size, whereas $T_c$ remains constant. The centrality dependence of the freeze-out parameters is weak as exemplified by the system Au+Au at 0.8A GeV. For the highest beam energies the fraction of nucleons excited to resonance states reaches freeze-out values of nearly 15%, suggesting resonance densities close to normal nuclear density at maximum compression. In contrast to the particle yields, which convey the status at chemical freeze-out, the shapes of the related transverse-mass spectra do reflect thermal freeze-out. The observed thermal freeze-out temperatures $T_{\mathrm{th}}$ are equal to or slightly lower than $T_c,$ indicative of nearly simultaneous chemical and thermal freeze-out.

We have studied the time evolution of the fluctuations in the net baryon number for different initial conditions and space-time evolution scenarios. We observe that the fluctuations at the freeze-out depend crucially on the equation of state (EOS) of the system and for realistic EOS the initial fluctuation is substantially dissipated at the freeze-out stage. At superproton synchrotron energies the fluctuations in net baryon number at the freeze-out stage for quark-gluon plasma and hadronic initial state is close to the Poissonian noise for ideal as well as for EOS obtained by including heavier hadronic degrees of freedom. For EOS obtained from the parametrization of lattice QCD results the fluctuation is larger than Poissonian noise. It is also observed that at relativistic heavy-ion collider energies the fluctuations at the freeze-out point deviates from the Poissonian noise for ideal as well as realistic equation of state, indicating presence of dynamical fluctuations.

High spin states in ${}^{178}\mathrm{Ir}$ were investigated by means of in-beam $\gamma$-ray spectroscopy techniques using the multidetector array GASP. Excited states of ${}^{178}\mathrm{Ir}$ were populated through the ${}^{159}\mathrm{Tb}{(}^{24}\mathrm{Mg},5n)$ fusion-evaporation reaction at ${E(}^{24}\mathrm{Mg})=131\mathrm{}–141$ MeV. Fourteen rotational bands have been observed and their configurations discussed. Alignments, band crossing frequencies, dynamical and kinematical moments of inertia, and electromagnetic properties have been analyzed in the framework of the cranking model. Signature inversion in the $\pi i_{13/2}\otimes \nu i_{13/2}$ and $\pi h_{9/2}\otimes \nu i_{13/2}$ structures has been identified and interpreted in the framework of the particle rotor model with residual $p-n$ interaction and variational moment of inertia. In bands involving the $\pi i_{13/2}$ orbital an increase in the deformation, relative to the other bands, has been found.

We studied the influence of a momentum dependent interaction in the context of isospin effects on fragmentation and dissipation in intermediate energy heavy ion collisions by using an isospin dependent quantum molecular dynamics model. It is shown that nuclear stopping, the number of nucleons emitted, and the multiplicity of intermediate mass fragments are larger with a momentum dependent interaction than without. In particular, the differences for these observables, when using an isospin dependent in-medium nucleon-nucleon cross section versus an isospin independent one, are also larger at high energies for a momentum dependent interaction than without one. Therefore, momentum dependence enhances the sensitivities of those observables to the isospin effect of the in-medium nucleon-nucleon cross section towards high beam energies.

The density dependent relativistic mean field (DDRMF) model in the new parametrization used recently is extended to investigate antikaon condensation and in-medium (anti)kaon production in $\beta$ equilibrium nuclear matter, and the obtained results are compared for different models. Our results show that the mean critical density for antikaon condensation is $\approx 2.8{\rho }_0$ in the DDRMF model with the two model parameter sets and in the nonlinear $\sigma -\omega$ model with the parameter set Tm1, while a little larger critical density $3.3{\rho }_0$ is obtained in chiral perturbation theory. The subthreshold energies for (anti)kaon production are calculated, and indicate that the in-medium effects predicted by the DDRMF model are essential for explaining the antikaon enhanced production, while kaon production rates are possibly enhanced only in the high density region. As an application for $\beta$ equilibrium nuclear matter, the masses against the central densities of neutron stars are studied in the DDRMF model too.