The nuclear overlap zone in noncentral relativistic heavy-ion collisions is azimuthally very asymmetric. By varying the angle between the axes of deformation and the transverse direction of the pair momenta, the suppression of $J/\Psi$ and ${\Psi }^{\prime }$ will oscillate in a characteristic way. Whereas the average suppression is mostly sensitive to the early and high density stages of the collision, the amplitude is more sensitive to the late stages. This effect provides additional information on the $J/\Psi$ suppression mechanisms such as direct absorption on participating nucleons, comover absorption or formation of a quark-gluon plasma. The behavior of the average $J/\Psi$ suppression and its amplitude with centrality of the collisions is discussed for Super Proton Synchrotron, Relativistic Heavy-Ion Collider, and Large Hadron Collider energies with and without a phase transition.

Masses of hadrons (baryons as well as mesons) are modified in the nuclear medium because of their interactions. In this paper we investigate the effect of in-medium meson masses on the properties of the nuclear matter. The calculations are performed in the Walecka model. We find that with the inclusion of meson mass modification, the computed equation of state becomes softer. We also find that the decrease in the nucleon as well as meson masses in the medium is smaller than that obtained in the case when the in-medium meson masses are not taken into account.

The role of the low lying nucleon resonances beyond the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ in the reaction $p\overrightarrow{p}\mathrm{pp}{\pi }^0$ near threshold is shown to be numerically significant by a calculation, which takes into account the pion rescattering contribution described by chiral perturbation theory and the short-range mechanisms that are implied by the nucleon-nucleon interaction model. The intermediate $N\left(1440\right)\mathrm{}\hspace{0.5em}{(P}_{11})$ resonance is excited by the short-range exchange mechanisms, while the $N\left(1535\right)\mathrm{}\hspace{0.5em}{(S}_{11})$ and $N\left(1520\right)\mathrm{}\hspace{0.5em}{(D}_{13})$ resonances are excited by $\eta$ and $\rho$ meson exchange, respectively. The $P_{11}$ increases the calculated cross section, whereas the $S_{11}$ and $D_{13}$ resonances decrease it. The calculation takes full account of the initial and final state interactions.

We present microscopic calculations of neutrino propagation in hot neutron matter above the nuclear density within the framework of the random phase approximation. Calculations are performed for nondegenerate neutrinos using various Skyrme effective interactions. We find that for densities just above the nuclear density, spin zero sound is present at zero temperature for all Skyrme forces considered. However, it disappears rapidly with increasing temperature due to a strong Landau damping. As a result the mean free path is given, to a good approximation, by the mean field value. Because of the renormalization of the bare mass in the mean field, the medium is more transparent as compared to the free case. We find, in contrast, that at several times the nuclear density, a new type of behavior sets in due to the vicinity of a magnetic instability. It produces a strong reduction of the mean free path. The corresponding transition density, however, occurs in a region where inputs from more realistic calculations are necessary for the construction of a reliable Skyrme-type parametrization.

Ground-state rotational energies of even-even deformed superheavy nuclei were calculated in the cranking approximation. Rather complex systematics of the results was obtained. It is interpreted as reflecting the exceptional shell structure of these nuclei, predicted by theory and partly confirmed by their decay properties, already shown in experiment.

Fragment-fragment-$\gamma$ coincidences have been measured for ${}^{28}\mathrm{Si}{+}^{28}\mathrm{Si}$ at an energy corresponding to the population of a conjectured resonance in ${}^{56}\mathrm{Ni}.$ Fragment angular distributions as well as $\gamma$-ray angular correlations indicate that the spin orientations of the outgoing fragments are perpendicular to the orbital angular momentum. This differs from the ${}^{24}\mathrm{Mg}{+}^{24}\mathrm{Mg}$ and the ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}$ resonances, and suggests two oblate ${}^{28}\mathrm{Si}$ nuclei interacting in an equator-to-equator molecular configuration.

We present a general method for incorporating an external electromagnetic field into descriptions of few-body systems whose strong interactions are described by integral equations. In particular, we address the case where the integral equations are those of quantum field theory and effectively sum up an infinite number of Feynman diagrams. The method involves the idea of gauging the integral equations themselves, and results in electromagnetic amplitudes where an external photon is effectively coupled to every part of every strong interaction diagram in the model. Current conservation is therefore implemented in the way prescribed by quantum field theory. We apply our gauging procedure to the four-dimensional integral equations describing a system of three distinguishable relativistic particles. In this way we obtain the expressions needed to calculate all possible electromagnetic processes of the three-body system. An interesting aspect of our results is the natural appearance of a subtraction term needed to avoid the overcounting of diagrams.

The gauging of equations method, introduced in the preceding paper, is applied to the four-dimensional integral equations describing the strong interactions of three identical relativistic particles. In this way we obtain gauge-invariant expressions for all possible electromagnetic transition currents of the identical three-particle system. In the three-nucleon system with no isospin violation, for example, our expressions describe the electromagnetic form factors of ${}^3\mathrm{H},$ $p\overrightarrow{d}\mathrm{pd}\gamma ,$ ${\gamma }^3\mathrm{He}\to pd,$ ${\gamma }^3\mathrm{He}\to ppn,$ etc. A feature of our approach is that gauge invariance is achieved through the coupling of the photon to all possible places in the (nonperturbative) strong interaction model. Moreover, once the proper identical particle symmetry is incorporated into the integral equations describing the strong interactions, the gauging procedure automatically provides electromagnetic transition currents with the proper symmetry. In this way the gauging of equations method results in a unified description of strong and electromagnetic interaction of strongly interacting systems.

Intermediate mass fragment (IMF) production is different for the reaction pair ${}^{58}\mathrm{Fe}{+}^{58}\mathrm{Fe}$ and ${}^{58}\mathrm{Ni}{+}^{58}\mathrm{Ni}$ for which the only difference is the ratio $N/Z,$ 1.23 for ${}^{58}\mathrm{Fe}$ and 1.07 for ${}^{58}\mathrm{Ni}.$ For beam-velocity fragments at $5.4°$ with Z from 3 to 15 the more proton-rich Ni reaction produces more even-$Z$ IMFs than the Fe reaction. The ratio (number of IMFs from ${}^{58}\mathrm{Ni}{+}^{58}\mathrm{Ni})$/(number of IMFs from ${}^{58}\mathrm{Fe}{+}^{58}\mathrm{Fe})$ as a function of Z is about 10% larger for even-$Z$ values than for odd-$Z$ values. The magnitude of this odd-even effect is about the same for beam energies with $E/A=45,$ 75, and 105 MeV.

We propose an effective current operator for nucleon electromagnetic knockout that incorporates spinor distortion and density-dependent nucleon form factors using an effective momentum approximation. This method can be used in a coordinate-space approach with either relativistic or nonrelativistic optical potentials and overlap functions. We studied these effects for the ${}^{16}\mathrm{O}\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{p}\right)$ reaction at $Q^2=0.8\mathrm{}\hspace{0.5em}(\mathrm{GeV}{/c)}^2$. Spinor distortion substantially enhances the left-right asymmetry while reducing the ratio between sideways and longitudinal recoil polarization for p-shell knockout by about 5% for modest missing momenta. We also find that the density dependence of nucleon form factors suggested by a quark-meson coupling model reduces the polarization ratio further. Much larger effects are obtained for the s shell than for the p shell. However, both effects are subject to much larger Gordon ambiguities than comparable nonrelativistic calculations.

We illustrate some of the concepts introduced in a recent paper devoted to the formulation of a self-consistent theory of large amplitude collective motion at finite excitation energy. We apply these concepts to a Hamiltonian with the symmetry of $\mathrm{SU}\mathrm{}\left(2\right)\mathrm{}\times \mathrm{SU}\mathrm{}\left(2\right)\mathrm{}$ (a doubled Lipkin model), in which the latter, exemplifying the slow, collective degrees of freedom, interacts with a set of harmonic oscillators representing the fast, noncollective variables. We pass to a mean-field approximation, which implies a collisionless regime, but show as well how the formalism may be extended to include the limit of collisions that establish instantaneous local equilibrium. In the representation of natural orbitals, the variables split into classical canonical sets and occupation numbers of the orbitals. Careful attention is paid to the problem of eliminating the intrinsic canonical coordinates from the equations of motion in such a way (white noise approximation) as to yield dissipative equations of motion for the collective variables. For the case of local equilibrium, the relaxation problem requires in addition an equation relating the slow change in temperature to the slow change of the collective variables. The two limiting relaxation scenarios are studied numerically.

The deformation driving $\nu i_{13/2}$ [660]1/2 structure has been identified for the first time in ${}^{131}\mathrm{Nd}.$ It is the lightest Nd $\mathrm{}(Z=60\mathrm{})\mathrm{}$ isotope in which a band based on this intruder orbital has been reported. A crossing between the [411]1/2 band and the [660]1/2 sequence takes place near $ħ\omega \approx 0.34$ MeV with a large interaction strength $(|V{|}_{\max }=47\mathrm{}$ keV). Thus, a smooth transition from the normal to the highly deformed minimum is established in ${}^{131}\mathrm{Nd}.$

The elastic scattering of ${}^{12}\mathrm{C}{+}^{24}\mathrm{Mg}$ has been studied by means of a phase-shift analysis of 21 angular distributions ranging from $E_{\mathrm{lab}}=16\mathrm{}\mathrm{MeV}$ up to $E_{\mathrm{lab}}=40\mathrm{}\mathrm{MeV}.$ A tridimensional plot of the reflection coefficient of the S matrix as a function of the angular momentum and energy shows a well-defined region of energy, which separates two regimes: strong absorption for higher energies and the so-called “anomalous transparency regime,” recently observed in this system at low energies. The Argand diagrams of the S matrix in angular momentum space also present very contrasting behaviors in the two regions with very rapidly varying phases in the low energy region, which we associate with a parity dependent term in the S matrix directly related to significant coupling to the elastic transfer of a ${}^{12}\mathrm{C}$ nucleus.

We used the local $N\Delta ,$ $NN,$ and $\mathrm{NN}\leftrightarrow N\Delta$ potentials derived from the chiral quark cluster model to analyze the bound-state problems of the $\mathrm{NN}\Delta ,$ $NNN,$ and $\mathrm{NN}$ systems. The last two systems are included for completeness and in order to check the reliability of our model. We found that the $\mathrm{NN}\Delta$ system has no bound states although there is evidence of a resonance near the $\mathrm{NN}\Delta$ threshold in the $\mathrm{}(J,I)=(3/2,1/2)\mathrm{}$ channel. We calculated the triton binding energy and the deuteron wave function produced by our model. We also calculated the $\mathrm{NN}{\hspace{0.5em}}^1{D}_2$ amplitude in order to study the effect upon the $\mathrm{NN}$ system of the $\mathrm{}(j,i)=(2,1)\mathrm{}\hspace{0.5em}N\Delta$ bound state predicted by the chiral quark cluster model.

A remarkable set of correlations of yrast and excited quasiband energies in collective nonrotor and rotor nuclei is discussed. These correlations are essentially independent of the nature of the states (e.g., yrast, quasi-$\gamma$-vibrational, superdeformed), of mass region, and of the type of nucleus (even-even, odd-$A,$ or odd-odd), and indicate a universal behavior which apparently describes all collective low energy structures. The results also show that, for most cases in odd-$A$ deformed nuclei, the band energies do not follow the rotational formula. The nature of spherical-deformed phase/shape transitions is also discussed and related to the seemingly (but not actually) different behavior of the neighboring even-even core nuclei. Finally, theoretical treatments that reproduce these correlations in even-even and odd-A nuclei are discussed, and new calculations with the geometric collective model are presented.

The charge-dependent realistic nuclear Hamiltonian for a nucleus, composed of neutrons and protons, can be successfully approximated by a charge-independent one. The parameters of such a Hamiltonian, i.e., the nucleon mass and the NN potential, depend upon the mass number A, charge Z, and isospin quantum number T of state of the studied nucleus.

The ${}_{\Lambda }^{16}\mathrm{O}$ hypernucleus is investigated by way of a folded-diagram method. The input G-matrix elements are calculated accurately from the Jülich-$\tilde{B}$ and the Nijmegen realistic hyperon-nucleon potentials with the Pauli exclusion operator properly treated in the finite hypernuclear system. The effect of hyperon-nucleon-nucleon three-body forces is included through the consideration of core polarization diagrams. Although our predicted energy spectrum of the hypernucleus is in good agreement with experiments in general, there are significant differences between the $J^{+}$ energy levels obtained from these two realistic potentials. A folded-diagram calculation for the $\Lambda$ single-particle energy has been performed. The spin-dependence parameters of Millener et al. calculated from the Jülich-$\tilde{B}$ and Nijmegen potentials are significantly different from each other, and the contribution from the $\Lambda -\Sigma$ three-body force to these parameters is important.

Low-energy two-neutron transfer reactions with Borromean nuclei (like ${}^6\mathrm{He})$ are shown to be an effective instrument for studying both the structure of such nuclei and the dynamics of nuclear reactions with their participation. A four-body model is developed to describe such two-nucleon transfer processes within the distorted-wave Born approximation. A realistic three-body bound-state wave function of ${}^6\mathrm{He}$ is used in the calculations and the role of its spatial localization is thoroughly studied. In particular, it is found that the “dineutron” configuration of the ${}^6\mathrm{He}$ nucleus gives the dominant contribution to the two-neutron transfer cross sections. Detailed analysis of the dynamics of these reactions is carried out and the possibilities of using multineutron transfer reactions for studying the structure of other exotic nuclei, in particular ${}^8\mathrm{He},$ are discussed.

Results of experiments performed to investigate the Xe+Cu 30 MeV/nucleon reaction are presented. The decay products coming from the disassembly of the unique source formed in central collisions and those coming from the decay of the quasiprojectile in peripheral and midperipheral ones have been identified through a careful data selection taking into account the experimental efficiency distortion on energy and angular distributions. The nuclear temperatures of these decaying systems have been measured from the relative isotopic abundances; the excitation energies of the fragment sources have been extracted by means of model calculations. The results have been compared to those obtained in the study of the Au+Au 35 MeV/nucleon in order to probe the effects of the finite size of the intermediate mass fragment emitting source on the relationship between its excitation energy and temperature. The studied fragment emitting sources have mass $A_1\simeq 130,\hspace{0.5em}{A}_2\simeq 200,\hspace{0.5em}{A}_3\simeq 300;$ moreover, the $A_2$ system have been investigated via two different reaction channels: the quasiprojectile of peripheral Au+Au and the unique fused system of the Xe+Cu central collisions. The relationship between temperature and excitation energy seems to be almost independent on the size of the emitting source and on the reaction entrance channel. On the contrary a weak dependence arises when individual thermometers are considered.