The validity of the chaos weighted wall formula developed for systems in which the particle motion is not fully randomized is tested. We consider an ideal gas in a cavity undergoing volume conserving shape oscillations and compare the energy transferred from the wall to the gas with the prediction of the chaos weighted wall formula. We find that the chaos weighted wall formula provides a fairly reliable description of one body dissipation for nearly integrable to highly chaotic systems.

In this paper we apply a well-tested approximation of electron Coulomb distortion effects to the exclusive reaction ${(e,e}^{\prime }p)$ in the quasielastic region. We compare the approximate treatment of Coulomb distortion effects to the exact distorted wave Born approximation evaluated by means of partial wave analysis to gauge the quality of our approximate treatment. We show that the approximate Møller potential has a plane-wave-like structure and hence permits the separation of the cross section into five terms which depend on bilinear products of transforms of the transition four current elements. These transforms reduce to Fourier transforms when Coulomb distortion is not present, but become modified with the inclusion of Coulomb distortion. We investigate the application of the approximate formalism to a model of ${}^{208}$Pb${(e,e}^{\prime }p)$ using Dirac-Hartree single particle wave functions for the ground state and relativistic optical model wave functions for the continuum proton. We show that it is still possible to extract, albeit with some approximation, the various structure functions from the experimentally measured data even for heavy nuclei.

Simple states, such as isobaric analog states or giant resonances, embedded into continuum are typical for mesoscopic many-body quantum systems. Due to the coupling to compound states in the same energy range, a simple mode acquires a damping width (“internal” dynamics). When studied experimentally with the aid of various reactions, such states reveal enhanced cross sections in specific channels at corresponding resonance energies (“external” dynamics which include direct decay of a simple mode and decays of intrinsic compound states through their own channels). We consider the interplay between internal and external dynamics using a general formalism of the effective non-Hermitian Hamiltonian and looking at the situation both from the “inside” (strength functions and spreading widths) and from the “outside” $(S$ matrix, cross sections, and delay times). The restoration of isospin purity and the disappearance of the collective strength of giant resonances at high excitation energy are discussed as important particular manifestations of this complex interplay.

A microscopic single-scattering model study of elastic scattering of ${}^9$Li from protons at 60 MeV/nucleon is reported. Results with two realistic effective nucleon-nucleon interactions, one adopted from the work of Mahaux and collaborators and another from the work of von Geramb and collaborators, bracket the $\sigma \left(\theta \right)$ data when a simple Gaussian ground state density with rms radius 2.32 fm is used.

Results of relativistic calculations of the direct knockout mechanism for the photon-induced removal of a proton from a target nucleus over a wide range of energies and nuclei are presented. Spectroscopic factors used in the calculations are fixed from consistent analyses of the quasifree electron scattering process ${(e,e}^{\prime }p)$. The results indicate that within the uncertainties of the model, the knockout contributions are generally close to the experimental data for missing momenta below $\approx 500$ MeV/$c$. This is in disagreement with nonrelativistic analyses which often find that the direct knockout contribution can be quite small compared to the data and that meson exchange corrections can be important. The present study suggests that meson exchange current contributions may not be as large when treated in a relativistic framework. We also point out some difficulties we encountered in analyzing the data for a ${}^{12}$C target at photon energies below 80 MeV.

The nonmesonic weak decay of $\Lambda$ hypernuclei is studied in a shell model framework. A complete strangeness-changing weak $\Lambda N\to \mathrm{NN}$ transition potential, based on one boson exchange, is constructed by including the exchange of the pseudoscalar mesons $\pi$, $K$, $\eta$ as well as the vector mesons $\rho ,\omega$, and $K^{*}$, whose weak-coupling constants are obtained from soft meson theorems and SU(6)${}_w.$ General expressions for nucleons in arbitrary shells are obtained. The transition matrix elements include realistic $\Lambda N$ short-range correlations and $\mathrm{NN}$ final state interactions based on the Nijmegen baryon-baryon potential. The decay rates are found to be especially sensitive to the inclusion of the strange mesons $K$ and $K^{*}$ even though the role of kaon exchange is found to be reduced with recent couplings obtained from one-loop corrections to the leading order in chiral perturbation theory. With the weak couplings used in this study the rates remain dominated by the pion-exchange mechanism since the contributions of heavier mesons either cancel each other or are suppressed by form factors and short-range correlations. The total decay rate therefore remains in agreement with present measurements. However, the partial rates which are even more sensitive to the inclusion of heavier mesons cannot be reconciled with the data. The proton asymmetry changes by 50% once heavier mesons are included and agrees with the available data.

The zero degree $\mathrm{}(p,n)\mathrm{}$ cross sections for a wide variety of targets and energies show an inverted angular shape for the differential cross section (the zero degree cross section has a minimum), which is correlated with the minimum observed in the neutron total cross section. Ramsauer calculations do not reproduce this correlation without the addition of a surface contribution. The existence of a zero degree $\mathrm{}(p,n)\mathrm{}$ minimum can be thought of as a Ramsauer effect in angular momentum space (i.e., $kR)$. We show that the existence of this inverted angular distribution also implies a rapid variation of the forward scattering amplitude with energy. We conjecture that the detailed description of the forward angle quasielastic $\mathrm{}(p,n)\mathrm{}$ cross sections at these minima is extremely sensitive to the details of the nuclear surface.

Based on the microscopic model, the friction coefficient for the relative motion of nuclei in deep-inelastic heavy-ion collisions is calculated. An advantage of the suggested method is that it allows one to consider the relative motion of nuclei and the intrinsic motion self-consistently. The radial dependence of the friction coefficient is studied and the results are compared with those found by other methods. It was demonstrated that the kinetic energy dissipation in deep-inelastic heavy-ion collisions is a gradual process which takes up a significant part of a reaction time. A decrease of the radial friction coefficient with a heating of nuclei is shown.

We report the most extensive set of vector ${\mathrm{iT}}_{11}$ and tensor $T_{20}$ and $T_{22}$ analyzing-power data for the $d\to +d\to d+p+n$ reaction. Two-particle coincidence data have been measured for six deuteron-proton, three deuteron-neutron and three proton-neutron angle pairs at an incident deuteron energy of 12.0 MeV. These data are compared to impulse-approximation calculations that treat the underlying nucleon-deuteron system exactly and include contributions from both target and projectile breakup processes. This model gives a good description of the analyzing-power and relative cross-section data. We show that the inclusion of nucleon-nucleon $P$ interactions considerably improves the agreement with the spin observables. The disagreement between the data and theoretical predictions show the limitations in our model and the importance of the rescattering processes. We suggest that the $d+d$ three-body breakup process will provide useful information on the nucleon-nucleon force when exact calculations become available.

We estimate the cross section of processes in which a transition effected by an inner atomic electron takes place simultaneously with a nuclear electromagnetic transition, for electric and magnetic interactions of various multipole orders. We calculate the rate of deexcitation of isomeric nuclei induced by processes of this type for the case when the holes in the atomic shells are produced by incident ionizing electrons and find that the induced nuclear deexcitation rate becomes comparable to the natural decay rate for ionizing fluxes of the order of ${10}^{14}$ W cm${}^{-2}$. We show that for $E1\mathrm{}$ and $M1\mathrm{}$ nuclear processes for which there is a matching between the electron and the nuclear transition energies, these electron-nuclear transitions can be used to produce pulses of Mössbauer radiation, with yields of the order of ${10}^4$ Bq mA${}^{-1}$.

We have obtained charge-changing cross sections and partial cross sections for fragmentation of 1.05 GeV/nucleon Fe projectiles incident on H, C, Al, Cu, and Pb nuclei. The energy region covered by this experiment is critical for an understanding of galactic cosmic ray propagation and space radiation biophysics. Surviving primary beam particles and fragments with charges from 12 to 25 produced within a forward cone of half-angle 61 mrad were detected using a silicon detector telescope to identify their charge and the cross sections were calculated after correction of the measured yields for finite target thickness effects. The cross sections are compared to model calculations and to previous measurements. Cross sections for the production of fragments with even-numbered nuclear charges are seen to be enhanced in almost all cases.

The interactions of ${}^{36}\mathrm{Ar}$ projectile nuclei with energies of 361, 546, and 765 MeV/nucleon and ${}^{40}\mathrm{Ar}$ nuclei with 352 MeV/nucleon, have been studied in a liquid-hydrogen target as part of a program to study interactions of relevance to the problem of cosmic-ray propagation in the interstellar medium. We have measured the cross sections for the production of isotopic fragments of the projectile nuclei in these interactions. The variations of these cross sections with mass, charge, and energy, are examined for insights into any systematic features of this type of fragmentation reaction that might aid predictions of other, unmeasured cross sections. These cross sections are also compared with the values derived from the most commonly used prediction techniques. It is suggested that these techniques could be improved by taking account of the systematic features identified here.

We compute the influence of Coulomb effects on the charged kaon distribution at low momentum in high-energy nucleus-nucleus collisions. This is accomplished by solving the Vlasov equation for the kaons in the presence of an expanding, highly charged, fireball.

The implications of the formation of a Bose condensate on one- and two-particle spectra are studied for ultrarelativistic nucleus-nucleus collisions in the framework of a hydrodynamic description. It is found that single-particle spectra are considerably enhanced at low momenta. The Bose-Einstein correlation function has an intercept below two. For pion pairs in the central region a two-component structure may appear in the correlation function, which is different from that found in quantum optics. The chaoticity parameter is strongly momentum dependent.

Considering the confinement of massless $u$ and $d$ quarks and massive $s$ quarks in an axially symmetric quadrupole shaped deformable bag, the stability properties of color-singlet strangelets at finite temperatures are studied for the baryon number $A<~100$. It is found that, in general, at each $A$ the energy of the strangelet is the lowest for the spherical shape. However, it is interesting to find shell structures for the deformed shapes at some new $A$ values, not found for the spherical shape. This should be of relevance for the experimental search of strangelets. The color projected (singlet) calculation shows that even for the deformed shapes the shell structures vanish only for the temperature, $T\gtrsim 30$ MeV. On the other hand, from a somewhat crude estimate we also find that at a fixed entropy per baryon (instead of a fixed temperature) of the order of unity or higher these shell structures disappear.

We address the question, what additional information on the source shape and dynamics can be extracted from three-particle Bose-Einstein correlations. For chaotic sources the true three-particle correlation term is shown to be sensitive to the momentum dependence of the saddle point of the source and to its asymmetries around that point. For partially coherent sources the three-pion correlator allows one to measure the degree of coherence without contamination from resonance decays. We derive the most general Gaussian parametrization of the two- and three-particle correlator for this case and discuss the space-time interpretation of the corresponding parameters.

The depletion of gluons as the parton flux traverses a nucleus in a heavy-ion collision can influence the production rate of heavy-quark states. Thus the suppression of $J/\psi$ can be due to gluon depletion in the initial state in addition to nuclear and hadronic absorption in the final state. A formalism is developed to describe the depletion effect. It is shown that, without constraints from other experimental facts beside the $J/\psi$ suppression data in $\mathrm{pA}$ and $\mathrm{AB}$ collisions, it is not possible to determine the relative importance of depletion vs absorption. Possible relevance to the enhanced suppression seen in the Pb-Pb data is mentioned but not studied.

We present an extension of global hydrodynamics [E. Schnedermann and U. Heinz, Phys. Rev. C 47, 1738 (1993)] to smooth transverse density and temperature profiles and to particle freeze-out along a continuous freeze-out hypersurface. With this model we reanalyze the single-particle spectra from S+S collisions at 200$A$ GeV and discuss the allowed range of initial conditions and equations of state.

We study the electromagnetic production from highly excited hadronic matter created in heavy ion collisions. The rates include the usual lowest order processes in quark-gluon plasma plus the usual reactions in the hadronic phase, related with $\rho {,a}_1$ mesons. The space-time integration is done using a hydrodynamical model. Conventional $\overline{q}q$ $\left({\pi }^{+}{\pi }^{-}\right)$ annihilation in quark-gluon plasma and hadronic phase cannot explain the observed dilepton spectrum, especially that by the CERES experiment at CERN. A decreased $\rho$ mass can account for the observed effect, provided it shifts into the region of 0.4–0.5 GeV near the phase transition. In order to test this hypothesis one should also look at the chiral partner of $\rho$, the axial $a_1$ meson: its mass must then behave similarly. Its decay $a_1\to \pi e^{+}{e}^{-}$ populates the low mass region seen in the same experiment. The results for direct photon production are below the current WA80 experimental bounds, for all variants considered.

We use a Glauber-like approach to describe very energetic nucleus-nucleus collisions as a sequence of binary nucleon-nucleon collisions. No free parameters are needed: All the information comes from simple parametrizations of nucleon-nucleon collision data. Produced mesons are assumed not to interact with each other or with the original baryons. Comparisons are made to published experimental measurements of baryon rapidity and transverse momentum distributions, negative hadron rapidity and transverse momentum distributions, average multiplicities of pions, kaons, hyperons, and antihyperons, and zero degree energy distributions for sulfur-sulfur collisions at 200 GeV$/c$ per nucleon and for lead-lead collisions at 158 GeV$/c$ per nucleon. Good agreement is found except that the number of strange particles produced, especially antihyperons, is too small compared with experiment. We call this model LEXUS: It is a base-line linear extrapolation of ultrarelativistic nucleon-nucleon scattering to heavy ion collisions.