We discuss medium modification of the $\rho$ meson originating from its coupling to in medium quasipions and delta-hole states. This medium effect leads to a marked structure of the $\rho$ meson strength function in the 500 MeV invariant mass region. We suggest that this effect may provide an explanation of the structure observed by the DLS Collaboration in the Ca+Ca/C+C ratio at 1 GeV/nucleon.

The effects of higher order corrections in ultrarelativistic nuclear collisions are considered. It is found that higher order contributions are small at low energy, large at intermediate energy, and small again at very high energy. An explanation for this effect is given. This means that the Weizsacker-Williams formula is a good approximation to use in calculating cross sections and beam lifetimes at energies relevant to relativistic and ultrarelativistic colliders.

It is essential to know the space-time structure of the nonlocal vacuum condensates for application to medium energy processes. Using the Dyson-Schwinger formalism in the rainbow approximation for the quark propagator, we study the nonlocal quark condensate and model forms for the nonperturbative gluon propagator constrained by fits to local condensates and deep inelastic scattering with nucleon targets.

Deep inelastic scattering of leptons off nuclear targets is analyzed within the convolution model and taking into account nucleon-nucleon correlations. We show that in the nuclear medium nucleons are distributed according to a function that exhibits a sizable $Q^2$ dependence and reduces to the ordinary light-cone distribution in the Bjorken limit. At $Q^2<50\mathrm{}\hspace{0.5em}(\mathrm{GeV}{/c)}^2$ and $x>\mathrm{}$1 this $Q^2$ dependence turns out to be stronger than the one associated with the nucleon structure function, predicted by perturbative quantum chromodynamics.

The quadrupole cross sections for $K^{+}{}^6\mathrm{Li}$ elastic scattering and inelastic scattering to the $3^{+}$ excited state are calculated using the distorted wave impulse approximation. Comparison is made to recent data to determine the importance of the quadrupole cross sections and to see if both the $K^{+}$ ${}^6\mathrm{Li}$ and $K^{+}$ ${}^{12}\mathrm{C}$ elastic scattering data can be fit using the same $K^{+}$-nucleon amplitudes.

We analyze recent experimental data on energy spectra and electromagnetic transition intensities of neutron-rich even Ru isotopes within the framework of the interacting boson model, taking into account both neutron and proton degrees of freedom. Signatures supporting an effective $\gamma$ deformation different from zero in the mass region around $A=110\mathrm{}$ are pointed out.

Quadrupole moments of the six known superdeformed (SD) bands of ${}^{193}\mathrm{Hg}$ and the yrast SD band of ${}^{192}\mathrm{Hg}$ have been determined by a Doppler-shift-attenuation-method measurement utilizing the gammasphere array. The quadrupole moments of all ${}^{193}\mathrm{Hg}$ SD bands were found to be similar, suggesting the active single-particle orbitals in the mass-190 region exhibit only small shape-driving effects. Additionally, there is evidence for an unexpected difference in the quadrupole moments of SD bands in ${}^{192}\mathrm{Hg}$ and ${}^{193}\mathrm{Hg}.$

Excited states in ${}^{108}\mathrm{Te}$ have been identified up to spins of $\sim 20ħ$ using the extremely weak $2p2n$ evaporation channel ($\sim 0.2\%$ of ${\sigma }_{\mathrm{fus}}$) from the bombardment of a backed ${}^{54}\mathrm{Fe}$ target with 243 MeV ${}^{58}\mathrm{Ni}$ ions. Channel selection and enhancement was made possible using the power of the GAMMASPHERE array to measure high-fold γ-ray coincidences and the resultant application of multiple γ-ray gating techniques. The observation in ${}^{108}\mathrm{Te}$ of two interleaved sequences of levels with assumed opposite parity connected by enhanced $E1\mathrm{}$ transitions is interpreted in terms of octupole correlations. The current results for ${}^{108}\mathrm{Te}$ make it the closest nucleus to the predicted region of octupole deformation centered at $N=Z=56\mathrm{}$ yet studied to high spin.

Vaporization and high multiplicity events, where the nuclear system is almost completely disassembled in light charged particles $(Z<~2),$ were analyzed for events with total charge detected $(\Sigma Z=23)$ in the ${}^{35}{\mathrm{C}\mathrm{l}+}^{12}\mathrm{C}$ reaction at 43 MeV/nucleon. Kinematic characteristics have been studied separately for $Z=1,$ $Z=2,$ and $Z=3\mathrm{}–4$ particles. When those are compared to simulations, noticeable differences in privileged emission direction have been found between $Z>~2$ particles and protons. For violent reactions, these differences could be explained by the apparent “symmetrization” of the reaction partners via the formation of a large necklike structure, and its subsequent breakup into many light ions.

Measurements are reported for fragment masses and velocities from the reactions $(17\mathrm{}–115)A\mathrm{MeV}$ ${}^{40}\mathrm{A}\mathrm{r}+\mathrm{C}\mathrm{u},$ Ag, and Au. Charged particle multiplicities were used to select the most violent reactions, and systematics are reported for the momentum and energy deposition. These reactions are fusionlike for $\lesssim 44A\mathrm{MeV}$ ${}^{40}\mathrm{Ar}$ with a large fraction of momentum and energy deposition in the heavy nuclear system. However, for $\gtrsim 44A\mathrm{MeV}$ ${}^{40}\mathrm{Ar},$ a majority of the projectile energy and momentum is carried away by a multibody spray of light ejectiles and only a minority is deposited in the heavy nucleus. Nevertheless heavy composite systems are formed with up to 9–12 MeV per source nucleon for $115A\mathrm{MeV}$ ${}^{40}\mathrm{Ar}.$

Excited states have been observed for the first time in the very neutron-deficient ${}^{118}\mathrm{Ba}$ nuclide. The ground-state band and a side band have been observed up to spins 20 and 17 ħ, respectively. The bands have been assigned to ${}^{118}\mathrm{Ba}$ using gamma-recoil and gamma-x ray coincidences. Excitation-energy systematics suggest that the ground state of ${}^{118}\mathrm{Ba}$ is less deformed than that of ${}^{120}\mathrm{Ba}.$ The side band decays into the ground-state band via three transitions, which are presumed to have $E1\mathrm{}$ character. The occurrence of $E1\mathrm{}$ transitions and negative-parity states in the very neutron-deficient barium $\mathrm{}(Z=56\mathrm{})\mathrm{}$ isotopes is discussed with respect to the possible onset of octupole correlations.

Proton emission from ${}^{145}\mathrm{Tm}$ was observed for the first time via the ${}^{92}\mathrm{Mo}{(}^{58}\mathrm{Ni},p4n)$ reaction, using the Holifield Radioactive Ion Beam Facility Recoil Mass Spectrometer in conjunction with a double-sided Si strip detector at the focal plane. The measured energy of the emitted proton is 1.728(10) MeV and its half-life is 3.5(10) μs, the shortest ever observed for ground-state proton radioactivity. When compared to the calculated WKB half-life for an $l=5\mathrm{}$ transfer, the spectroscopic factor is 0.51(16), which is consistent with the value of 0.64 calculated via the BCS approximation for a spherical nucleus. Also, the half-life of ${}^{113}\mathrm{Cs}$ was determined with a greater precision than previously available to be 16.7(7) μsec.

Excitation functions have been measured for quasielastic and elastic scattering of ${}^{16}{\mathrm{O}+}^{152}\mathrm{Sm}$ around the Coulomb barrier at three backward angles with high precision in small energy steps. The barrier distributions have been extracted from the quasielastic and elastic scattering excitation functions and compared with experimental barrier distributions obtained from the existing fusion excitation function and spin distributions for the same reaction system, and from the quasielastic and elastic scattering excitation functions for the neighboring isotope ${}^{154}\mathrm{Sm}.$ The agreement is rather good. The results show clearly that the asymmetric barrier distributions are due to the effects of static deformations on the target nucleus. This is the first attempt to compare quantitatively the experimental barrier distributions with the fusion barrier distributions extracted from the spin distributions for the same system.

Transverse kinetic energies of individual fragments have been measured over a broad range of emitter excitation energies for the reaction $1A\mathrm{GeV}$ $\mathrm{A}\mathrm{u}+\mathrm{C}.$ For excitation energies leading to large intermediate mass fragment multiplicities, these transverse energies require large collective radial expansion of the emitting systems. However, the traditional decomposition of the transverse energy into a thermal component and a Coulomb and collective component proportional to the fragment mass cannot account for this expansion. Expansion velocities show an increase with decreasing fragment $Z$ and thus indicate fractionation of the collective energy for the expanding system. This collective energy increases with emitter excitation up to about 50% of the energy deposited for a nuclear system with total energy $\sim 12A\mathrm{MeV}.$ The bulk of the collective energy is carried away by ejectiles of $Z<~3.$

High-spin states in ${}_{94}^{240}\mathrm{Pu}$ and ${}_{96}^{248}\mathrm{Cm}$ have been populated with Coulomb excitation at beam energies slightly above the Coulomb barrier. In each nucleus a new side band has been identified in γ-γ coincidence measurements and has been interpreted as the lowest-lying octupole excitation. The alignments and Routhians of these bands, as well as the branching ratios of $E1\mathrm{}$ decays to the ground-state bands, are in good agreement with results from cranked RPA calculations.

The relativistic Hartree-Bogoliubov model in coordinate space, with a finite range pairing interaction, is applied to the description of Λ hypernuclei with a large neutron excess. The addition of the Λ hyperon to Ne isotopes with neutron halo can shift the neutron drip by stabilizing an otherwise unbound core nucleus. The additional binding of the halo neutrons to the core originates from the increase in magnitude of the spin-orbit term. Although the Λ produces only a fractional change in the central mean-field potential, through a purely relativistic effect it increases the spin-orbit term which binds the outermost neutrons.

The isoscalar and the isovector dipole mode of drip line and β-stable nuclei are investigated, using the self-consistent Hartree-Fock plus the random-phase approximation with Skyrme interactions. Including simultaneously both the isoscalar and the isovector correlation, the RPA response function is estimated in the coordinate space so as to take into account properly the continuum effect. The spurious component is carefully taken away from the calculated strength. In β-stable nuclei such as ${}^{208}\mathrm{Pb}$ the frequency of the isovector giant dipole resonance (IVGDR) is lower than that of the isoscalar giant dipole resonance (compression mode). In contrast, in lighter drip line nuclei a major part of the isoscalar compression dipole strength lies at an energy much lower than the energy of the IVGDR.

We present solutions of the coupled, nonrelativistic ${}^3{S}_1$-${}^3{D}_1$ gap equations for neutron-proton pairing in symmetric nuclear matter, and estimate relativistic effects by solving the same gap equations modified according to minimal relativity and using single-particle energies from a Dirac-Brueckner-Hartree-Fock calculation. As a main result we find that relativistic effects decrease the value of the gap at the saturation density $k_F=1.36\mathrm{}{\mathrm{fm}}^{-1}$ considerably, in conformity with the lack of evidence for strong neutron-proton pairing in finite nuclei.

By deriving the angle between the proton and neutron spin vectors $j_{\pi }$ and $j_{\nu }$ in the shears bands in ${}^{198,199}\mathrm{Pb},$ we present a semiclassical analysis of the $B\left(M1\mathrm{}\right)\mathrm{}$ and $B\left(E2\mathrm{}\right)\mathrm{}$ transition probabilities as a function of the shears angle. This provides a semiempirical confirmation of the shears mechanism proposed by Frauendorf using the tilted-axis-cranking model. In addition, we propose that the rotational-like behavior observed for these bands may arise from a residual proton-neutron interaction.

We provide an interpretation of anomalous large angle scattering (ALAS) for α-nucleus systems by decomposing the full scattering amplitude $A\left(\theta \right)$ into three components in $l$ space viz. $A_I\left(\theta \right),$ $A_S\left(\theta \right),$ and $A_O\left(\theta \right)$ corresponding to interior, surface, and predominantly Coulombic outer partial waves and show that it is the interference between $A_S\left(\theta \right)$ and $A_O\left(\theta \right)$ terms which is primarily responsible for ALAS. The interpretation of ALAS given here is complementary to that of Brink and Takigawa where the nuclear $S$ matrix was split into a barrier region part and an interior region part in coordinate space. We also compute the resonance-like poles of the $S$ matrix in the complex energy plane and find that one can associate broad barrier region resonance poles with the few partial waves which contribute to $A_S\left(\theta \right).\mathrm{}$