The double-folding model is generalized for the calculation of nucleus-nucleus potential using the new version of the density-dependent M3Y interaction which reproduces consistently the equilibrium density and binding energy of the normal nuclear matter as well as the density and energy dependence of the nucleon optical potential. The exchange part of the heavy-ion optical potential is evaluated within a local density formalism, using the finite-range exchange components of the same interaction. The model is used successfully to describe the elastic ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ scattering data at low and medium energies. The influence of different density-dependent parameters (which determine different nuclear equations of state) on the description of heavy-ion scattering is also discussed.

We present the results of an analysis of two charged particle and transverse energy correlations in Si+Pb collisions at BNL AGS at 14.6 GeV/c per nucleon. The measured semi-inclusive normalized two particle pseudorapidity corrleation function exhibits short range correlations similar to the correlations observed in hadron-hadron and hadron-nucleus collisions at higher energies, although the observed correlations are smaller than the values scaled from hp and hA data. Estimates, provided by the observed correlations, of the intermittency indices as well as of the parameters of the cluster model are presented. Predictions using the fritiof event generator, which at this level of statistical accuracy show no pseudorapidity correlations, are not in agreement with our data. Azimuthal angle two particle correlations show nonzero back-to-back correlations in the central region (consistent with fritiof predictions) and are almost flat in the projectile fragmentation region. We also present results on the transverse energy azimuthal correlation function, which are similar to those from the two particle correlation function.

We calculate thermal production of u, d, s, c, and b quarks in ultrarelativistic heavy ion collisions. The following processes are taken into account: thermal gluon decay (g→i i¯), gluon fusion (gg→i i¯) and quark-antiquark annihilation ( j¯→i ī), where i and j represent quark species. We use the thermal quark masses, ${\mathit{m}}_{\mathit{i}}^2$(T)≃${\mathit{m}}_{\mathit{i}}^2$+(2${\mathit{g}}^2$/9)${\mathit{T}}^2$, in all the rates. At small mass [${\mathit{m}}_{\mathit{i}}$(T)<2T], the production is largely dominated by the thermal gluon decay channel. We obtain numerical and analytic solutions of one-dimensional hydrodynamic expansion of an initially pure glue plasma. Our results show that even in a quite optimistic scenario, all quarks are far from chemical equilibrium throughout the expansion. Thermal production of light quarks (u, d, and s) is nearly independent of species. Heavy quark (c and b) production is quite independent of the transition temperature and could serve as a very good probe of the initial temperature. Thermal quark production measurements could also be used to determine the gluon damping rate, or equivalently the magnetic mass.

We consider equilibration in relativistic nuclear dynamics starting from a nonequilibrium Green’s-functions approach. The widely used Boltzmann-Uehling-Uhlenbeck equation is obtained only as the Markovian limit (i.e., negligible memory time). The actual memory time in energetic nuclear collisions turns out to be ∼2–3 fm/c, which interferes substantially with the time scale of the relaxation process. The memory kernels of the collision process will be presented. Because of their more involved structure, depending sensitively on the kinematical regime, both less and more stopping power is observed in the reaction compared to the Markovian description.

Given the phenomenological success of the Nambu–Jona-Lasinio model in describing the meson physics in the low energy limit, it is tempting to find the fully relativistically structured nucleon solution in the same model under the similar approximation employed in the mesonic sector. To achieve this goal we need to solve a relativistic Faddeev equation. The factorizability of the two-body T matrix induces the three-body Faddeev equation to a tractable two-body Bethe-Salpeter equation. The reduced equation is then solved numerically. Our result indicates that the nucleon consists of three loosely bound constituent quarks.

We introduce a scalar and a vector ΔΔ-meson vertex in the relativistic Dirac-Brueckner model for nuclear matter and investigate the consequences. We find small effects on the effective nucleon properties. The effects in the Δ sector are more profound, although the Δ is still effectively repelled out of the medium.

Measurements of the vector analyzing power ${\mathit{iT}}_{11}$ in πd elastic scattering at 49 MeV have been performed using a dynamically polarized target and a magnetic spectrometer. Data at seven ${\mathrm{\pi }}^{+}$ laboratory scattering angles between 50° and 130° were taken together with a complementary measurement at 60° for ${\mathrm{\pi }}^{\mathrm{-}}$d elastic scattering. In general, we find agreement with models that include the πN ${\mathrm{P}}_{11}$ amplitude and disagreement with models that exclude or suppress it.

A recoil-shadow measurement of isomer decays in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Hf}$ has revealed many weak γ-ray transitions. One of these is a sevenfold K-forbidden E1 transition from the ${\mathit{K}}^{\mathrm{\pi }}$=$8^{\mathrm{-}}$ isomer (${\mathit{T}}_{1/2}$=163 ns) to the ${\mathit{K}}^{\mathrm{\pi }}$=$0^{+}$ ground-state band. The low hindrance factor for this transition in ${}_{}{}^{172}{}_{}{}^{}\mathrm{Hf}$ is compared with the hindrance factors for other ΔK=8 E1 transitions.

We have measured the light charged particle (LCP) emission probabililty for the spontaneous fission of ${}_{}{}^{244}{}_{}{}^{}\mathrm{Pu}$. For the LCP emission to binary fission probability ratio a value of (2.96±0.31)×${10}^{\mathrm{-}3}$ was found. This result is in agreement with the previously observed trends concerning the LCP emission probability.

Fokker-Planck equations are derived for QCD Wigner distributions taking into account quantum color dynamics. These equations show that the anomalously large color diffusion coefficient in a high T quark-gluon plasma leads to strong damping of collective color modes.

Fusion cross sections and gamma ray multiplicities have been measured for the ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$${+}^{142}$Ce, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$${+}^{138}$Ba, and ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$${+}^{122}$Sn entrance channels leading to the ${}_{}{}^{170}{}_{}{}^{}\mathrm{Hf}$ compound nucleus. The mean spins deduced from the gamma multiplicities do not show any anomalous behavior as observed in some other measurements.

Excited states of ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}$ were observed using the ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$${(}^7$Li,4n) reaction at a beam energy of 40 MeV. Two rotational bands with levels of spins up to 45/2ħ were seen; a positive parity band built on the 5/$2^{+}$ ground state, and a negative parity band built on the 5/$2^{\mathrm{-}}$ level at 97.5 keV excitation energy. Transitions were also observed from levels in a band built on a 3/$2^{+}$ state at 103.2 keV. Several features of the 5/$2^{\pm }$ bands suggest octupole instability or deformation, as may be expected for nuclei in this region. Levels of the same spin but opposite parity are nearly degenerate, and strong electric dipole transtions connect appropriate band members. Other features such as gyromagnetic ratios indicate an interpretation in terms of bands associated with separate orbits in a reflection-symmetric potential.

Inspired by the results of a recent (${\gamma }^{\mathrm{*}}$,p${\mathrm{\pi }}^{\mathrm{-}}$) measurement, a mechanism is proposed for ${\mathit{N}}^{\mathrm{*}}$ electroproduction and propagation in nuclei at high momentum transfer. Quantum interference effects predicted by our model could be observed in an exclusive measurement under suitable kinematic conditions and momentum resolution.

The problem of nuclear rotation treated within the framework of the two-dimensional cranking and particles-rotor Hamiltonians is solved in the many-body space for a deformed single-j shell configuration with pairing. The properties of ‘‘identical’’ (twinned) bands in neighboring, in particular, odd and even systems are studied. It is shown that the twinned band mechanism is accompanied by a ‘‘quantized alignment’’ in the relative angular momentum (or incremental) alignments without involving any special dynamical symmetry as, e.g., pseudospin symmetry. Conditions for a nontrivial manifestation of the quantized incremental alignment together with the criteria of ‘‘being identical’’ found in the literature are discussed.

As it is well known, the single-nucleonic levels in a nucleus manifest either the Kramers degeneracy d=2, or, if a nucleus is spherical, a trivial ‘‘magnetic’’ degeneracy d=2j+1. It will be shown using the results of the realistic total nuclear energy calculations that a possibility of a fourfold degenerate levels exists in a number of N∼136 isotones due to their high intrinsic symmetry. Those exotic states are predicted to be isometric; they lie only a few hundreds of keV above the ground state. Other possible nuclear regions where the same mechanism may take place are indicated.

Enhanced production of soft—i.e., low transverse momentum—pions has been experimentally observed in nucleus-nucleus collisions at beam energies of 14.5A GeV [the Brookhaven National Laboratory Alternating Gradient Synchrotron (AGS)] and 200A GeV (CERN Super Proton Synchrotron). Here the rapidity dependence of soft pion and kaon production for the reaction Si(14.5A GeV)+Au is studied in the framework of the relativistic quantum molecular dynamics (RQMD) approach. The softest mesons from decaying resonance matter, which turns out to be the main production mechanism in RQMD, show a peculiar rapidity dependence, a weakening of the signal in the central rapidity region of the participant nucleons. This is in striking contrast to expectations from all other suggested mechanisms like mean fields, collective flow, and quantum statistical effects. The prediction can be tested by forthcoming experiments at the AGS in the near future. It is also predicted that a similar, though quantitatively much weaker, signal can be observed in the kaon spectra.

We investigate the photoexcitation of nucleon resonances in nuclei taking into account the quark structure of the nucleon. We calculate the total strength of the M1, E1, and E2 excitation in a two-nucleon system, considered as two three-quark clusters with a properly antisymmetrized wave function. The calculations show that the resonance excitation in the deuteron is not modified with respect to the free nucleon case. In contrast, when the nucleon relative distance assumes typical nuclear values, quark exchange leads to a ∼11% damping of the ${\mathit{D}}_{13}$ resonance and ∼23% of the ${\mathit{F}}_{15}$, but it leaves the Δ excitation practically unaffected, in agreement with the recent photoabsorption measurements.

Double differential cross sections have been measured for inclusive (p,p’) reactions on targets of ${}_{}{}^{89}{}_{}{}^{}\mathrm{Y}$, ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, and the even-mass Mo isotopes from A=92 to 98 at incident proton energies of 120, 160, and 200 MeV. Comparisons are made with calculations based on the statistical multistep direct theory of Feshbach, Kerman, and Koonin. In general it is found that the theory gives a good description of the angular distributions. Possible explanations for the deviation of the predicted cross sections from experiment at very low and very high excitation energies of the residual nucleus are given.

Inclusive fragment isotope spectra were measured at 15°, 30°, 45°, and 60° for the ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ + Ag reaction at 35 MeV/nucleon. The energy spectra of many isotopes of elements from Be to Ne were obtained. A two-parameter thermal model fits the angular distributions of the low-energy fragments. One parameter, source kinetic energy/temperature, is proportional to fragment mass number. The other, total fragment production cross section, after adjustment for binding energy, has a decreasing exponential dependence on mass number.