By using the Boltzmann-Langevin equation, which incorporates dynamical fluctuations beyond usual transport theories, we simulate the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$${+}^{40}$Ca reaction system at different beam energies 20, 60, and 90 MeV/nucleon for different impact parameters. Dynamical fluctuations become larger and larger with increasing bombarding energy and the system can reach densities corresponding to the unstable region of the nuclear matter equation of state at energies above 60 MeV/nucleon. By coupling the Boltzmann-Langevin equation with a coalescence model in the late stages of the reaction, we obtain the distribution of the intermediate mass fragments in each event. From the correlation analysis of these fragments, we recover some trends of recent multifragmentation data. A critical behavior analysis is also provided.

Within a multichannel, multirank model of wide applicability, resonances in complex systems are studied. In particular, compound resonances, which are well observed in nuclear systems can be clearly examined as arising from bound states in subsystems of the coupled-channel system. A less well known, and until now little understood, form of resonance is the quasicompound resonance (or structure). These are seen as arising from resonances in subsystems of the multichannel system. The nature of the two types of resonances is contrasted, in their behavior as the strength of coupling increases. Compound resonances arise infinitely narrow, but of fixed height and increase in width, whereas quasicompound structures arise as small ‘‘bumps’’ of finite width, and increase in height. After presentation of the general theory, these properties are illustrated in a simple numerical model calculation.

A quasipotential formalism for elastic scattering from relativistic bound states is based on applying an instant constraint to both initial and final states in the Breit frame. This formalism is advantageous for the analysis of electromagnetic interactions because current conservation and four momentum conservation are realized within a three-dimensional formalism. Wave functions are required in a frame where the total momentum is nonzero, which means that the usual partial wave analysis is inapplicable. In this work, the three-dimensional equation is solved numerically, taking into account the relevant symmetries. A dynamical boost of the interaction also is needed for the instant formalism, which in general requires that the boosted interaction be defined as the solution of a four-dimensional equation. For the case of a scalar separable interaction, this equation is solved and the Lorentz invariance of the three-dimensional formulation using the boosted interaction is verified. For more realistic interactions, a simple approximation is used to characterize the boost of the interaction.

Relaxation rates are calculated by numerically solving the Kadanoff-Baym equations for an extended system of nuclear matter. The time evolutions of initial nonequilibrium distributions in momentum space, defined by two Fermi spheres, is studied. Comparisons are made with the (semi-) classical method used in BUU, VUU, etc. Danielewicz has found that at a nucleon density of ∼0.3 nucleon/${\mathrm{fm}}^3$ and an equilibrated temperature of about 70 MeV, the quantum relaxation rate is smaller than the classical by a factor of about 2. These results are confirmed. The calculations are extended to lower temperatures (energies) and densities and this ratio is found to be essentially unchanged over a wide range although there are deviations from this rule as seen in the text. The quantum evolutions are started either with an uncorrelated or a correlated initial distribution. The latter are obtained with imaginary time stepping. The relaxation time approximation was previously found to be excellent for the classical evolution. It is found to be as good for the quantum evolution. The memory time is in the present calculations found to be less than 5 fm/c (i.e., ∼1.7×${10}^{\mathrm{-}23}$ s). One concludes that quantum-mechanical effects have to be incorporated in the models of heavy ion collisions and nuclear dynamics. Not until this is done comprehensively will one be able to readily assess the role of two-nucleon collisions in the equilibration process.

We present results of a calculation of the low-energy fusion reaction α+d${\to }^6$Li+γ. In this calculation ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ was treated as a three body α-2N system in the framework of the multicluster dynamic model with Pauli projection (MDMP). To construct the ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$ wave function with a high precision a large basis is used for the radial wave function of α-2N relative motion in the ground state of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. We pay special attention to the asymptotic region of this radial function. We obtained good agreement with experimental data on both angular distribution and total cross section by taking into account the contribution of the isoscalar E1 multipole.

We investigate the role of relativistic and nonrelativistic optical potentials used in the analysis of (e,e’p) data. We find that the relativistic calculations produce smaller (e,e’p) cross sections even in the case in which both relativistic and nonrelativistic optical potentials fit equally well the elastic proton-nucleus scattering data. Compared to the nonrelativistic impulse approximation, this effect is due to a depletion in the nuclear interior of the relativistic nucleon current, which should be taken into account in the nonrelativistic treatment by a proper redefinition of the effective current operator.

The azimuthal correlation function has been calculated as a function of beam energy and impact parameter for the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ar}$${+}^{27}$Al system from 36 MeV/nucleon to 100 MeV/nucleon via a quantum molecular dynamics (QMD) approach. The anisotropy of the azimuthal correlation at midrapidity interval becomes weaker with increasing beam energy and collision centrality. Around 100 MeV/nucleon the azimuthal correlation tends to be flat which indicates the rotational collective motion disappears. The vanishing of rotation may be due to the short lifetime of the emitter as suggested by the two-particle correlation function at small relative momenta. A method to estimate the fluctuation of the experimental reaction plane with respect to the true reaction plane is presented also via the azimuthal correlation function.

Within the one level R-matrix approach several hindrance factors for the radioactive decays in which are emitted ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{20}{}_{}{}^{}\mathrm{O}$ atomic nuclei are calculated. The interior wave functions are supposed to be given by the recently proposed enlarged superfluid model, an extension of the JINR-Dubna’s quasiparticle phonon nuclear model. The spectroscopic factors are expanded in terms of products of cluster overlaps and intrinsic overlap integrals. The cluster overlaps are equivalents of the generalized coefficients of fractional parentage, while for the intrinsic overlap integrals we construct a model, which is an extension of the usual models for simple particle decay such as deuteron, triton, and α decay. The exterior wave functions are calculated from a cluster-nucleus double-folding model potential obtained with the M3Y interaction. As examples of the cluster decay fine structure we analyzed the particular cases of α decay of ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}$, ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ decay of ${}_{}{}^{223}{}_{}{}^{}\mathrm{Ra}$ and ${}_{}{}^{20}{}_{}{}^{}\mathrm{O}$ decay of ${}_{}{}^{229}{}_{}{}^{}\mathrm{Th}$ and ${}_{}{}^{255}{}_{}{}^{}\mathrm{Fm}$. A relatively good agreement with the experimental data is obtained especially in the case of the α-decay fine structure.

The optical potential and observables for proton${\mathrm{-}}^8$He elastic scattering are studied within the single scattering approximation to the Kerman, McManus, and Thaler (KMT) multiple scattering expansion. Calculations are performed for proton${\mathrm{-}}^8$He elastic scattering at 72 MeV/nucleon, for which there are available experimental data, and also at 200 MeV/nucleon incident energy. It is shown that the calculated elastic scattering observables are modified significantly by the inclusion of the proton${\mathrm{-}}^8$He spin dependence arising from the nucleon-nucleon amplitude. The roles of the core and valence nucleon contributions to this spin dependence are clarified.

The properties of the α${+}^{16}$O interaction in the vicinity of the Coulomb barrier are investigated by constructing (real, energy-independent) potentials which reproduce—when resonant nonpotential contributions are added to the potential background—all available ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$(α,α) elastic scattering angular distributions and excitation functions between 3.5 and 9 MeV incident energies. These low energy potentials, which are constructed for angular momenta ranging from 0 to 5, are in line with the global potential extracted from the analysis of the higher energy data (20≤${\mathit{E}}_{\mathrm{\alpha }}$≤150 MeV), but a slight angular momentum dependence, and an increase of the barrier height of about 1 MeV, are found necessary to reproduce the low energy data; this effect is qualitatively similar to that predicted by calculations taking into account antisymmetrization or dispersion relation effects. These potentials reproduce the properties of the first three members of the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ${\mathit{K}}^{\mathrm{\pi }}$=$0_4^{+}$ ‘‘higher nodal’’ rotational band, which dominate the scattering in the investigated energy range, and of the ${\mathit{J}}^{\mathrm{\pi }}$=$5^{\mathrm{-}}$ member of the ${\mathit{K}}^{\mathrm{\pi }}$=$0^{\mathrm{-}}$ ‘‘inversion doublet’’ band. By taking into account the energy dependence of the interaction at lower energy, these potentials also give a nice account of the properties of the ${\mathit{J}}^{\mathrm{\pi }}$=$1^{\mathrm{-}}$ and $3^{\mathrm{-}}$ members of the same band, and are found to be compatible with the properties of the first three members of the ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ ground state band.

We have investigated the fragmentation of 3.65 GeV/nucleon ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$, and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ projectiles on C, Al, Cu, Ag, and Pb targets using solid state nuclear track detectors. Track counting was performed by an automatic measuring system. Total charge changing and the partial cross sections for the production of fragments with charges 9≤Z≤15 for ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ projectiles and of charge 6≤Z≤11 for ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}$ were determined. Comparison with theoretical models and other experimental data is made.

We present the results of an analysis of charged particle pseudorapidity distributions in the central region in collisions of a Au projectile with Al, Cu, Au, and U targets at an incident momentum of 10.8 GeV/c per nucleon. The pseudorapidity distributions are presented as a function of transverse energy produced in the target or central pseudorapidity regions. The correlation between charged multiplicity and transverse energy measured in the central region, as well as the target and projectile regions, is also presented. We give results for transverse energy per charged particle as a function of pseudorapidity and centrality.

We investigate the disappearance of collective flow in the reaction plane in heavy-ion collisions within a microscopic model (QMD). A systematic study of the impact parameter dependence is performed for the system Ca+Ca. The balance energy strongly increases with impact parameter. Momentum dependent interactions reduce the balance energies for intermediate impact parameters b≊4.5 fm. For the heavy system Au+Au, dynamical negative flow is not visible in the laboratory frame but does exist if the initial precontact rotation of the system due to the Coulomb potential is subtracted. For semiperipheral collisions of Ca+Ca with b≊6.5 fm a new two-component flow is discussed. Azimuthal distributions exhibit strong collective flow signals, even at the balance energy.

Open charm production during the equilibration of a gluon dominated parton plasma is calculated, with both the time-dependent temperature and parton densities given by a set of rate equations. Including prethermal production, the total enhancement of open charm production over the initial gluon fusion depends sensitively on the initial parton density and the effective temperature. The dependence of the prethermal charm production on the space-momentum correlation in the initial parton phase-space distribution is also discussed.

Recent experimental data on the negative correlation between forward energy and transverse energy, which have been reported for the interactions of 14.6A GeV ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ with Al, Cu, Au, and Pb, 60A and 200A GeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ with S, Cu, Ag, and Au, are investigated by a model based on the description of geometrical properties of nucleus-nucleus collision processes. A parameter, ellipticity e, which might describe the conversion of initial energy into that of radiated final-state hadrons is proposed.

Triple differential cross sections of pions in heavy ion collisions at 1 GeV/nucleon are studied with the isospin quantum molecular dynamics (IQMD) model. After discussing general properties of Δ resonance and pion production we focus on azimuthal correlations: At projectile- and target-rapidities we observe an anticorrelation in the in-plane transverse momentum between pions and protons. At c.m.-rapidity, however, we find that high ${\mathit{p}}_{\mathit{t}}$ pions are being preferentially emitted perpendicular to the event plane. We investigate the causes of those correlations and their sensitivity on the density and momentum dependence of the real and imaginary part of the nucleon and pion optical potential.

We use the quantum molecular dynamics model to investigate the formation mechanism of protons and composite fragments in intermediate-energy heavy-ion collisions. We demonstrate that dynamical correlations result in the production rate for final state nucleon clusters (and hence composite fragments) being higher than would be expected if statistics and the properties of the available phase space were dominant in determining composite formation. This finding contradicts assumptions which underlie models based on either the one-body phase-space density or on statistical equilibrium. Hybrid models which treat the initial violent collisions in an intranuclear cascade or a Boltzmann-Ühling-Uhlenbeck approach and then change to a statistical model may be used for central collisions at higher energy (e.g., 600A MeV) but fail for semiperipheral reactions and for all impact parameters at lower beam energies.

The electric properties of the neutron have been deduced from precise measurements of coherent scattering lengths and of total cross sections of Pb, of its isotopes with A=208, 207, and 206, and of Bi. Their energy dependences are due to nuclear properties, to nuclear and atomic charges as well as to the neutron’s electric polarizability and to the neutron-electron interaction. We investigated in detail the different evaluations used in the past by German and Russian scientist groups. By means of both data handling methods we found consistent results of ${\mathrm{\alpha }}_{\mathit{n}}$=(0.0±0.5)${10}^{\mathrm{-}3}$ ${\mathrm{fm}}^3$ for the electric polarizability and of ${\mathit{b}}_{\mathit{n}\mathit{e}}$=-(1.32±0.03)${10}^{\mathrm{-}3}$ fm for the neutron-electron scattering length. This result agrees with quark-core models of the neutron.

We discuss the calculation of QCD sum rules for hadrons in matter from the point of view of nuclear many-body theory and treat the sum rule for the rho meson as an example. We describe the factorization approximation that is used to calculate four-quark condensates in vacuum and in matter and discuss the corrections to that approximation in some detail. In the case of the rho meson, we find that corrections to the factorization approximation in matter can vary from about 10 to 40 percent depending upon the model used to describe the nucleon. If the nucleon is considered to be composed of a quark coupled to a scalar (T=0) diquark, the corrections are significant, while, if the quark is coupled to an axial-vector (T=1) diquark, the corrections are small. The physical nucleon may be taken to have equal scalar and axial-vector diquark components. In that case, corrections of about 20 percent are found for the density-dependent part of the vector-isovector polarization tensor. More precise estimates require a more detailed picture of nucleon structure than that considered here. In a previous work we discussed the corrections to the factorization approximate for the nucleon-nucleon correlator evaluated in nuclear matter. The corrections we calculated served to eliminate a problematic density dependence of the four-quark condensates that arose when using the factorization approximation in matter. However, our study provided a successful analysis only when the interpolating field advocated by Ioffe was used. The situation in the case of sum rules for the vector-isovector polarization tensor is subject to fewer uncertainties, since the choice of the current is unique. We find that, while the corrections we calculate for the density dependence of the four-quark condensates are not small, they lead to only very small modifications in the predicted density dependence of the rho mass.

A general framework to compute matrix elements of operators between relativistic three-quark bound states is presented and used to investigate static properties of the nucleonic solution to the Faddeev equation. The Ward-Takahashi identity in the three-quark system is derived and the violation of gauge invariance due to a Euclidean cut-off is investigated. Results for the axial vector coupling constants and quark condensates are presented and discussed in comparison to the additive diquark-quark model.