The sensitivity of nucleon-nucleus elastic scattering observables to the off-shell structure of nucleon-nucleon $t$ matrices, derived from realistic $\mathrm{NN}$ potentials, is investigated within the context of a full-folding model based on the impulse approximation. Our study uses recently developed $\mathrm{NN}$ potential models, which describe a subset of the $\mathrm{NN}$ data base with a ${\chi }^2$ per datum $\sim 1$, which means that the $\mathrm{NN}$ $t$ matrices are essentially on-shell equivalent. We calculate proton-nucleus elastic scattering observables for ${}^{16}\mathrm{O}$, ${}^{40}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$ between 100 and 200 MeV laboratory energy. We find that the elastic scattering observables are insensitive to off-shell differences of the employed $\mathrm{NN}$ $t$ matrices. A more detailed investigation of the scattering equation and the optical potential as given in a factorized approximation reveals that the elastic scattering observables do not sample the $\mathrm{NN}$ $t$ matrices very far off-shell where they exhibit differences.

We investigate the properties of the optical model wave function for light heavy-ion systems where absorption is incomplete, such as $\alpha {+}^{40}$Ca and $\alpha {+}^{16}$O around 30 MeV incident energy. Strong focusing effects are predicted to occur well inside the nucleus where the probability density can reach values much higher than that of the incident wave. This focusing is shown to be correlated with the presence at back angles of a strong enhancement in the elastic cross section, the so-called ALAS (anomalous large angle scattering) phenomenon; this is substantiated by calculations of the quantum probability flux and of classical trajectories. To clarify this mechanism, we decompose the scattering wave function and the associated probability flux into their barrier and internal wave contributions within a fully quantal calculation. Finally, a calculation of the divergence of the quantum flux shows that when absorption is incomplete, the focal region gives a sizable contribution to nonelastic processes.

We present calculations for the nuclear level density parameter over a wide range of nuclear mass and temperature. The hot nucleus is modeled in a refined Thomas-Fermi approximation that allows the confinement of the hot evaporating metastable system through an external pressure. The position and temperature dependence of the momentum and frequency dependent effective masses are taken into account. The agreement with experimental data, particularly its temperature dependence, is reasonably reproduced.

We present calculations for $\Delta$ excitation in the ${(K}^{+}{,K}^{+})$ reaction in nuclei. The background from quasielastic $K^{+}$ scattering in the $\Delta$ region is also evaluated and shown to be quite small in some kinematical regions, so as to allow for a clean identification of the $\Delta$ excitation strength. Nuclear effects tied to the $\Delta$ renormalization in the nucleus are considered and the reaction is shown to provide new elements to enrich our knowledge of the $\Delta$ properties in a nuclear medium.

We suggest several possibilities to study the properties of the symmetry term in the nuclear equation of state from radioactive beam experiments. Collision simulations with a stochastic transport approach, where asymmetry effects are suitably introduced, are presented. The dynamical response of an interacting highly asymmetric nuclear matter can be studied, taking advantage of the neutron skin structure. The main reaction mechanisms, from fusion to deep inelastic and fragmentation, appear quite sensitive to the form of the symmetry term of the effective force used, opening some new appealing experimental perspectives. Finally new features of fragment production are presented, due to the onset of chemical plus mechanical instabilities in dilute asymmetric nuclear matter.

Systematic results are presented on proton, deuteron, and triton emission from the target spectator region in collisions of $10.20A$ GeV gold projectiles with a gold target. A forward hodoscope utilizes detection of projectile spectator fragments to determine the orientation of the reaction plane, event by event. The directed flow $〈p_x〉$ is determined as a function of pseudorapidity. Projectile spectator energy is used to estimate impact parameters. Results are compared to current theoretical models ARC, ART, and RQMD. In all cases good agreement with theory is obtained for calculations utilizing a pure cascade without nuclear potential contributions.

We reconsider the influence of two-particle final state interactions (FSI) on two-particle Bose-Einstein interferometry. We concentrate in particular on the problem of particle emission at different times. Assuming chaoticity of the source, we derive a new general expression for the symmetrized two-particle cross section. We discuss the approximations needed to derive from the general result the Koonin-Pratt formula. Introducing a less stringent version of the so-called smoothness approximation we also derive a more accurate formula. It can be implemented into classical event generators and allows us to calculate FSI corrected two-particle correlation functions via modified Bose-Einstein “weights.”

The production of pions and sigma mesons from disoriented chiral condensates (DCC’s) of finite size is studied using the linear sigma model and a continuous mode coherent state. Two models are used to describe the decay of DCC’s. One assumes instantaneous decay and the other assumes radiation from the surface. It is found that, for a spherical DCC of radius of several fm, possible signals related to the momentum spectrum, multiplicity, and the neutral-to-charged pion ratio will be completely masked by the background which dominates multiparticle production in nucleus-nucleus collisions at high energies unless an appropriate cut or binning in the phase space is made on an event-by-event basis. We propose that a signal of DCC’s may manifest itself as an abnormal peak in the rapidity distribution if pions with medium and large transverse momenta are cut off. The smearing effect due to sigma meson decay on the characteristic distribution of neutral-to-charged pion ratio is also studied.

Phi meson-baryon cross sections, estimated within a one-boson-exchange model, serve as input for a calculation of the collision rates in hot hadronic matter. We find that the width of the φ meson is modified through collisions with baryons by 1–10 MeV at 160 MeV temperature depending on the baryon fugacity. Thermalization of the φ in high energy heavy ion collisions is discussed.

A gauge invariant model based on $\pi$ and $\rho$ Regge trajectory exchanges provides a successful and economical description of the forward charged pion electroproduction reactions above the resonance region. Its sensitivity to the meson form factors is investigated in kinematics where the pion electromagnetic form factor will be extracted at high $Q^2$ at TJNAF. An extension to $K^{+}$ electroproduction is presented.

The Green’s functions are constructed and a one-loop calculation is given for the scalar and vector densities and for the equation of state of nuclear matter with a Bose condensate of dibaryons. This is the lowest approximation in the loop expansion of quantum hadrodynamics, sufficient to account for the presence of dibaryons not in the condensate in the heterophase nucleon-dibaryon matter. It leads to a finite effective nucleon mass and remains consistent with increasing the density.

We present a coupled channels model for $\pi N$ scattering based on $N$, $\Delta$, and $N_{S11\mathrm{}}^{*}\mathrm{}\left(1535\right)\mathrm{}$ pole and nonpole contributions, plus correlated $2\pi$ and $a_0$ meson exchange. The open channels considered are $\pi N$, $\eta N$, $\sigma N$, and $\pi \Delta$. The model gives a qualitatively good fit to the phase shifts and elasticity parameters in both isospin channels for partial waves up to $J=$$\frac{3}{2}$ and $\pi N$ c.m. energies of 1.4 GeV. Above that energy the appearance of resonances in various partial waves precludes a precise fit to the data without explicitly including resonances in those partial waves and—probably—additional inelastic channels. Within the model the $N_{S11\mathrm{}}^{*}\mathrm{}\left(1535\right)\mathrm{}$ resonance appears to require a genuine three-quark component, whereas the $N_{P11\mathrm{}}^{*}\mathrm{}\left(1440\right)\mathrm{}$ resonance appears to permit description as a purely dynamical effect.

We calculate the leading contribution to the weak $\Lambda \Lambda K$ coupling in heavy baryon chiral perturbation theory, including the SU(3) breaking terms arising at one loop. This coupling gives the leading one-boson exchange amplitude for the process $\Lambda \overrightarrow{\Lambda }\Lambda n$ and is an important component in understanding the decay of $\Lambda \Lambda$ hypernuclei. We predict the $S$-wave and $P$-wave amplitudes to be found in the ranges $-0.5\lesssim {\mathcal{A}}^{\mathrm{}\left(S\right)\mathrm{}}\lesssim 1.1$ and $-8.9\lesssim {\mathcal{A}}^{\mathrm{}\left(P\right)\mathrm{}}\lesssim -0.7$, respectively.

A formalism developed previously to study the smaller nuclear spin-dependent parity-violating effects using the relativistic mean field theory has been generalized to the case of odd-odd nuclear systems such as ${}^{210}$Fr. Because of the recent success in trapping Fr atoms, parity-violation experiments for Fr seem feasible. The nuclear spin-dependent parameters $\eta$ and ${\eta }^{\prime }$ are calculated using the anapole moment parameters ${\kappa }_p$ and ${\kappa }_n.$ They are used to calculate the hyperfine transition amplitudes for the $6\overrightarrow{S}7S$ transition in ${}^{134}$Cs and $7\overrightarrow{S}8S$ in ${}^{210}$Fr. The calculated hyperfine transition amplitudes in Fr are one order of magnitude larger than those in Cs.

The consequences of the charge symmetry breaking effects of the mass difference between the up and down quarks and electromagnetic effects for searches for strangeness form factors in parity violating electron scattering from the proton are investigated. The formalism necessary to identify and compute the relevant observables is developed by separating the Hamiltonian into charge symmetry conserving and breaking terms. Using a set of SU(6) nonrelativistic quark models, the effects of the charge symmetry breaking Hamiltonian are considered for experimentally relevant values of the momentum transfer and found to be less than about 1%. The charge symmetry breaking corrections to the Bjorken sum rule are also studied and shown to vanish in first-order perturbation theory.

The new nuclide ${}^{186}$Hf has been produced via a multinucleon transfer reaction between 60 MeV/nucleon ${}^{18}$O ions and a natural tungsten target in a net result of an exchange of two target protons for two projectile neutrons, i.e., ${(}^{186}\mathrm{W}-2p+2n).$ Sources of ${}^{186}$Hf prepared by radiochemical separation have been studied. The growth and decay of ${}^{186}$Ta $\gamma$ rays has been observed, identifying the ${}^{186}$Ta parent as ${}^{186}$Hf. The half-life of ${}^{186}$Hf has been determined to be 2.6$\pm$1.2 min.

Two-particle azimuthal correlations have been used to extract reaction plane dispersion free triple-differential cross sections for $d$, $t$, and $\alpha$ particles for the midcentral collisions of ${}^{84}\mathrm{Kr}{+}^{197}\mathrm{Au}$ at $E/A=35\mathrm{}$, 55, and 70 MeV. Both experimental measurements and extrapolations from lower incident energies suggest that rotational flow disappears at $E/A\approx 100$ MeV for light charged particles and that reaction plane dispersions introduce large uncertainties in extracting the disappearance of rotational flow.

The phenomenological model we proposed previously to describe simultaneously the ground and $K^{\pi }{=0\mathrm{}}^{-}$ bands in pear shape nuclei is used to describe the recently published data for some Rn isotopes which behave as an octupole vibrator. The application for the isotopes ${}^{222,224,226}\mathrm{Ra}$, where data for high spin states are now available, is also made. Although the two sets of isotopes have a diffierent behavior, they are treated in a unified fashion, and the agreement of predictions with experimental data is excellent.

Double-dipole excitations in ${}^{208}\mathrm{Pb}$ are analyzed within a microscopic model explicitly treating $2p2h$ excitations. Collective states built from such excitations are shown to appear at about twice the energy of the isovector giant dipole resonance, in agreement with experimental findings. The calculated cross section for Coulomb excitation at relativistic energies cannot explain simultaneously the measured single-dipole and double-dipole cross sections, however.

Using the kinetic theory we discuss how the particle and energy densities of the quark-gluon plasma fluctuate in a space-time cell. The fluctuations in the equilibrium plasma and in one from the early stage of ultrarelativistic heavy-ion collisions are estimated. Within the physically interesting values of the parameters involved the fluctuations appear sizable in both cases.