Recoil proton polarization observables were measured for both the $p\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{p}\right)$ and $d\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{p}\right)n$ reactions at two values of $Q^2$ using a newly commissioned proton focal plane polarimeter at the MIT-Bates Linear Accelerator Center. The hydrogen and deuterium spin-dependent observables $D_{\ell \ell }$ and $D_{\ell t}$, the induced polarization $P_n$, and the form factor ratio $G_E^p{/G}_M^p$ were measured under identical kinematics. The deuterium and hydrogen results are in good agreement with each other and with the plane-wave impulse approximation (PWIA).

The first measurements of the induced proton polarization $P_n$ for the ${}^{12}\mathrm{C}\left({e,e}^{\prime }\overrightarrow{p}\right)$ reaction are reported. The experiment was performed at quasifree kinematics for energy and momentum transfer $(\omega ,q)\approx$ (294 MeV, 756 MeV/c) and sampled a missing momentum range of 0–250 MeV/c. The induced polarization arises from final-state interactions and for these kinematics is dominated by the real part of the spin-orbit optical potential. The distorted-wave impulse approximation provides good agreement with data for the ${1p}_{3/2}$ shell. The data for the continuum suggest that both the ${1s}_{1/2}$ shell and underlying $\ell >1\mathrm{}$ configurations contribute.

Relativistic Hartree-Bogoliubov theory in coordinate space is used to describe the chain of zirconium isotopes reaching from ${}^{116}\mathrm{Zr}$ to the drip line nucleus ${}^{140}\mathrm{Zr}$. Pairing correlations are taken into account by a density dependent force of zero range. For neutron numbers larger than the magic number $N=82\mathrm{}$ a giant neutron halo outside the core of ${}^{122}\mathrm{Zr}$ is predicted. It is formed by up to six neutrons.

Evidence for a modification of the ${\rho }^0$ mass in the nuclear medium via the ${}^3\mathrm{He}(\gamma ,{\pi }^{+}{\pi }^{-})X$ reaction is reported here. The tagged photon energies were mostly below the ${\rho }^0$ production threshold on a free nucleon, and the bound nucleon's Fermi momentum was utilized to produce the ${\rho }^0$. The mass shift observed is $\delta m_{{\rho }^0}=160\mathrm{}\pm 35\mathrm{MeV}{/c}^2$ and is significantly larger than theoretical model predictions for this nucleus and nuclear matter density.

${}^{12}\mathrm{C}(\gamma ,pn)$ and $(\gamma ,pp)$ cross sections have been measured in kinematics which emphasize direct $2N$ knockout for $E_{\gamma }=120\mathrm{}–400\mathrm{MeV}$ and ${\theta }_p=23\mathrm{}°–152°$. The cross sections for both reactions peak strongly in the $\Delta$-resonance region. Theoretical calculations that account for the medium dependence of the $\Delta$ propagator predict a similar photon energy dependence to the data and describe the general trends of the measured $(\gamma ,pp)/(\gamma ,pn)$ ratio. Both cross sections show strong angular dependence, and the large differences between the two channels indicate different microscopic reaction mechanisms.

A Comment on the Letter by Weiping Liu, et al., Phys. Rev. Lett. 77, 611 (1996).

A new experimental method for the high-resolution measurement of photoabsorption cross sections has been developed. The energy resolution of about 0.1% is achieved by measuring the transmitted photons from a target with a high-resolution high-energy photon spectrometer. The method is applied to the measurement of the photoabsorption cross section of ${}^{18}\mathrm{O}$ in the giant resonance region. Significant fine structure of the resonance is observed.

We investigate the shell structure of bubble nuclei in simple phenomenological shell models using Strutinsky's method. Shell energies down to $-40\mathrm{}\mathrm{MeV}$ are shown to occur for certain magic nuclei. Estimates demonstrate that the calculated shell effects for certain magic numbers of constituents are probably large enough to produce stability against fission, $\alpha$, and $\beta$ decay. No bubble solutions are found for mass number $A\le 450$.

We determine an “empirical” kaon dispersion relation by analyzing and fitting recent experimental data on kaon production in heavy-ion collisions. We then investigate its effects on the hadronic equation of state at high densities and on neutron star properties. We find that the maximum mass of neutron stars can be lowered by about ${0.4M}_{\odot }$ once kaon condensation as constrained by our empirical dispersion relation is introduced. We emphasize the growing interplay between hadron physics, relativistic heavy-ion physics, and the physics of compact objects in astrophysics.

A parameter-free nonlocal double-folding-inspired interaction is proposed for the nucleus-nucleus systems. Excellent reproductions of elastic scattering differential cross section data were obtained for several systems over a wide range of bombarding energies. Our results should be of value in the description of the scattering of other many-body systems.

In a finite temperature Thomas-Fermi theory, we construct caloric curves for finite nuclei enclosed in a freeze-out volume a few times the normal nuclear volume, with and without inclusion of flow. Without flow the caloric curve indicates a smooth liquid-gas phase transition, whereas with flow the transition may be very sharp. We discuss these results in the context of two recent experiments, one for a heavy symmetric system ( $\mathrm{Au}+\mathrm{Au}$ at $600A\mathrm{MeV}$) and the other for a highly asymmetric system ( $\mathrm{Au}+\mathrm{C}$ at $1A\mathrm{GeV}$) where different behaviors in the caloric curves are seen.

A Comment on the Letter by E. E. W. Bruins, et al., Phys. Rev. Lett. 75, 21 (1995). The authors of the Letter offer a Reply.

A Reply to the Comment by J. Jourdan, I. Sick, and J. Zhao.

We propose the use of ratios of the pion-proton correlation functions evaluated under different conditions to study the relative space-time asymmetries in pion and proton emission (pion and nucleon source relative shifts) in high energy heavy ion collisions. We address the question of the noncentral collisions, where the sources can be shifted spatially relative to each other both in the longitudinal and in the transverse directions in the reaction plane. We use the RQMD event generator to illustrate the effect and the technique.

Transient electric field gradients have been observed in measurements of particle-γ-angular correlations of Coulomb excited nuclei in H-like ions during traversal through thick metallic layers. The $V_{\mathrm{ZZ}}$ values deduced for ${}^{20}\mathrm{Ne}\left(2^{+}\right)$, ${}^{32}\mathrm{S}\left(2^{+}\right)$, ${}^{40}\mathrm{Ar}\left(2^{+}\right)$, ${}^{52}\mathrm{Cr}\left(2^{+}\right)$, ${}^{54}\mathrm{Fe}\left(2^{+}\right)$, and ${}^{62}\mathrm{Ni}\left(2^{+}\right)$ are found to be of the order of ${10}^{21}\mathrm{V}/{\mathrm{cm}}^2$ with consistently positive sign. They arise from distortions of the $1s$ electron orbit of the H-like ions by the wake field gradient induced in the solid by the charge of the moving ion. The observed interaction frequencies reflect the sign of the quadrupole moment of the excited $2^{+}$ states.

The dependence of the stability of prolate deformed nuclei on the neck parameter is studied from the point of view of the interplay between order and chaos. The statistical properties of level spectra for the deformed space explored by the fission process are presented. It is found that on saddles the single particle motion is unstable against chaos, whereas at minimums it is stable. Based on this investigation a possible understanding of hyperdeformed ${}^{144–146}\mathrm{Ba}$ appearing in the spontaneous fission of ${}^{252}\mathrm{Cf}$ is provided.

The spectra and the electromagnetic transitions of the nuclei ${}^{51}$Ca and ${}^{51}$Sc with 11 nucleons in the f-p shell are described in the nuclear shell-model approach by using two different two-body effective interactions. The full f-p shell basis functions are used with no truncation. The new parallel shell-model computer code DUPSM (Drexel University parallel shell model), that we recently developed, has been used. The calculations have been done on the MOSIX parallel machine at the Hebrew University of Jerusalem.

Invariant mass analyses of $(p,{\pi }^{\pm })$ pairs in ${}^{58}\mathrm{Ni}+\mathrm{Cu}$ collisions at $1.97A\mathrm{GeV}$ have been performed and show correlations resulting from the decays of the Δ resonance, the Λ baryon, and possibly the $N^{*}\left(1440\right)$ resonance. A reduction in the Δ mass is observed and the mass reduction increases with collision centrality. Events generated by the relativistic cascade model (ARC) also reveal a mass reduction. The mass reduction is related to the size of the reaction volume and the details of Δ production mechanisms in heavy ion collisions.

High-spin states have been investigated in the mirror pair nuclei ${}^{49}\mathrm{Cr}$ ( $Z=24\mathrm{}$, $N=25\mathrm{}$) and ${}^{49}\mathrm{Mn}$ $(Z=25,N=24\mathrm{})$. Mirror symmetry up to the band termination at about 10.7 MeV has been established. A comparison of the corresponding energy levels of the pair shows, for the first time, that the Coulomb energy difference approaches zero as the band termination is approached. This is explained intuitively in terms of a pure $f_{\frac{7}{2}}$ shell framework. For ${}^{49}\mathrm{Cr}$, excellent agreement is found between the data and recent full $\mathrm{pf}$-shell calculations.

The origin of the forward-backward enhancement of $K^{+}$ emission observed in symmetric nucleus-nucleus collisions at 1 GeV/nucleon has been explored. The nonisotropic pion-baryon reaction leading to $K^{+}$ production has been found to play a substantial role in creating the forward-backward peak of the kaon angular distribution. By an analysis including also the effects from relevant final-state interactions on kaons, we can reproduce the experimental kaon angular distribution. We argue that the observed nonisotropic kaon emission may provide a support to the pion-induced channel for subthreshold kaon production in heavy ion reactions.