The reaction cross section $({\sigma }_R)$ is calculated using the optical limit of the Glauber theory. A density-dependent effective nucleon-nucleon $(NN)$ cross section ${\sigma }_{NN}$ is considered. Finite and zero range $NN$ interactions are studied. The effect of finite range and an appropriate local density can increase ${\sigma }_R$ up to 20% compared to the zero range at constant density $(0.16{\mathrm{fm}}^{-3})$, while a zero range calculation with free $NN$ cross section increases ${\sigma }_R$ up to 13%. These factors affect the values of the rms radii for neutron rich nuclei extracted from ${\sigma }_R$.

The total fusion cross section for the ${}^9\mathrm{Be}+{}^{27}\mathrm{Al}$ system has been measured at energies close and above the Coulomb barrier. Reaction cross sections for this system were derived from elastic scattering data, and the breakup-plus-transfer-channel cross sections were estimated from the difference between these data and measured cross-section fusion.

Experimental data of the pion charge form factor are well represented by Poincaré invariant constituent-quark phenomenology depending on two parameters: a confinement scale and an effective quark mass. Pion states are represented by eigenfunctions of mass and spin operators and of the light-front momenta. An effective current density is generated by the dynamics from a null-plane impulse current density. A simple shape of the wave function depending only on the confinement scale is sufficient. The range of quark masses and confinement scales consistent with both low- and high-$Q^2$ data depends on the shape of the wave function.

The first ($d,p$) neutron transfer reaction on a neutron-rich r-process nucleus has been measured at the Holifield Radioactive Ion Beam Facility. The ${}^2\mathrm{H}({}^{82}\mathrm{Ge},p){}^{83}\mathrm{Ge}$ reaction was studied by bombarding a 430-$\mu g/{\mathrm{cm}}^2$ (${\mathrm{CD}}_2$)${}_n$ target with a 330-MeV beam of radioactive ${}^{82}\mathrm{Ge}$. The reaction Q value ($Q=1.47\pm 0.02$ stat. $\pm 0.07$ sys. MeV) has been measured leading to the first determination of the mass of the $N=51$ nucleus ${}^{83}\mathrm{Ge}$. Excitation energies, angular distributions, and spectroscopic factors for the first two states of ${}^{83}\mathrm{Ge}$ have also been determined.

The problem of calculating the four-nucleon bound state properties for the case of realistic two- and three-body nuclear potentials is studied using the hyperspherical harmonic (HH) approach. A careful analysis of the convergence of different classes of HH functions has been performed. A restricted basis is chosen to allow for accurate estimates of the binding energy and other properties of the ${}^4\mathrm{He}$ ground state. Results for various modern two-nucleon and two- plus three-nucleon interactions are presented. The origin of the isospin $T=1$ and $T=2$ admixtures in the ${}^4\mathrm{He}$ ground state is discussed in detail. The ${}^4\mathrm{He}$ asymptotic normalization constants for separation in $2+2$ and $1+3$ clusters are also computed.

We adjust a new improved relativistic mean-field effective interaction with explicit density dependence of the meson-nucleon couplings. The effective interaction DD-ME2 is tested in relativistic Hartree-Bogoliubov and quasiparticle random-phase approximation (QRPA) calculations of nuclear ground states and properties of excited states, in calculation of masses, and it is applied to the analysis of very recent data on superheavy nuclei.

Shell-model calculations in the $s-d$ shell have been utilized to examine how the statistical behavior of eigenvalues and reduced transition probabilities are affected by broken isospin symmetry. Calculations have been performed for the nuclides ${}^{22}\mathrm{Na},{}^{26}\mathrm{Al}$, and ${}^{34}\mathrm{Cl}$ and have been compared to existing experimental data for ${}^{26}\mathrm{Al}$ and ${}^{30}\mathrm{P}$. The eigenvalue statistics depend on the magnitude of the Coulomb matrix element, and this is reflected in a sensitivity to the choice of single-particle energies. The distributions of reduced transition probabilities are not universal but depend upon the particular transition mode chosen; this behavior is qualitatively similar to experimental results.

The reactions $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ and $e^{+}{e}^{-}\to \stackrel{̲}{N}N$ with $N=p,n$ are studied in a nonperturbative quark model. The work suggests that the two-step process, in which the primary $\stackrel{-}{q}q$ pair first forms a vector meson which in turn decays into a hadron pair, is dominant over the one-step process in which the primary $\stackrel{-}{q}q$ pair is directly dressed by additional $\stackrel{-}{q}q$ pairs to form a hadron pair. To reproduce the experimental data of the reaction $e^{+}{e}^{-}\to \stackrel{-}{n}n$ and $\stackrel{-}{p}p$, a D-wave, ω-like vector meson with a mass of around 2 GeV has to be introduced.

The exclusive processes ${}^2\mathrm{H}(e,e^{\text{'}}p)n,{}^3\mathrm{He}(e,e^{\text{'}}p){}^2\mathrm{H}$, and ${}^3\mathrm{He}(e,e^{\text{'}}p)(\mathrm{pn})$ have been analyzed using realistic few-body wave functions and treating the final state interaction (FSI) within a generalized eikonal approximation (GEA), based on direct calculation of the Feynman diagrams describing the rescattering of the struck nucleon with the nucleons of the $A-1$ system. The approach represents an improvement of the conventional Glauber approach (GA) because it allows one to take into account the effects of the nuclear excitation of the $A-1$ system on the rescattering of the struck nucleon. Using realistic three-body wave functions corresponding to the AV18 interaction, the results of our parameter-free calculations are compared with available experimental data. It is found that in some kinematical conditions FSI effects represent small corrections, whereas in other kinematics conditions they are very large and absolutely necessary to provide a satisfactory agreement between theoretical calculations and experimental data. It is shown that in the kinematics of the experimental data that have been considered, covering the region of missing momentum and energy with $p_m⩽0.6\hspace{1em}\mathrm{GeV}/c$ and $E_m⩽100\hspace{1em}\mathrm{MeV}$ in the perpendicular kinematics, the GA and GEA predictions differ only by less than $\simeq 3\text{−}4\%$.

Isomeric ${}^{178}\mathrm{Hf}$ ($t_{1/2}=31$ yr, $E_x=2.446\mathrm{MeV}$, $J^{\pi }={16}^{+}$) was bombarded by a white beam of x rays from the Advanced Photon Source at Argonne National Laboratory. A search was made for x-ray induced decay of the isomer by detecting prompt and delayed $\gamma$ rays associated with the decay. No induced decay was observed. Upper limits for such a process for x-ray energies between 7 and 100 keV were set. The limits between 7 and 30 keV are below $\approx 3\times {10}^{-27}$ ${\mathrm{cm}}^2\mathrm{keV}$ for induced decay that bypasses the 4-s isomer and $\approx 5\times {10}^{-27}$ ${\mathrm{cm}}^2\mathrm{keV}$ for induced decay that is delayed through this isomer, which are orders of magnitude below values at which induced decay was reported previously. These limits are consistent with what is known about the properties of atomic nuclei.

The photodissociation reaction ${}^8\mathrm{B}+\gamma \to {}^7\mathrm{Be}+p$ is used to provide information on the astrophysical $S_{17}$ factor of the inverse radiative capture reaction, knowledge of which is crucial for an estimation of the high-energy neutrino flux from the sun. Since, at present, the Coulomb field of a fully stripped nucleus serves as the source of the photons, an adequate analysis requires a genuine three-body treatment of this reaction. Among the uncertainties still affecting present analyses, the possible modification of the dissociation cross section by the post-decay acceleration of the fragments ${}^7\mathrm{Be}$ and p in the target field plays a major role. Working with the prior form of the dissociation amplitude, we first discuss why the standard approximation for the final-state wave function is not appropriate for a proper investigation of this problem; instead, use of a genuine three-particle wave function for the final state proves to be mandatory. Such is provided by a recently proposed wave function for three charged particles in the continuum [A. M. Mukhamedzhanov and M. Lieber, Phys. Rev. A 54, 3078 (1996)] which possesses all the essential features required. It is an exact solution of the three-body Schrödinger equation, but only asymptotically, i.e., for large distances. Therefore, only qualitative predictions can be made currently, such as predicting the kinematic configurations in which post-decay acceleration effects play a negligible role. Explicit calculations are presented for the single and the double differential cross sections for the ${}^{208}\mathrm{Pb}({}^8\mathrm{B},{}^7\mathrm{Be}p){}^{208}\mathrm{Pb}$ Coulomb breakup reaction. We also investigate the influence of the $E2$ multipole and find its contribution to be small for small scattering angles, but comparable to the one from the $E1$ dipole for large scattering angles.

This article reviews experimental results obtained recently on the x-ray-induced acceleration of the decay of the long-lived isomer ${}^{178}\mathrm{Hf}{}^{m2}$. Two basic mechanisms for the induced decay are considered: (1) direct interaction of the incident x rays with the nucleus and (2) the nucleus-ray interaction proceeding via atomic shells. We establish that the absence of $K$ forbiddenness for all transitions to a hypothetical $“\text{mixed}K“$ level cannot explain the measured cross sections even if collective nuclear matrix elements, resonant conditions, and so on, are assumed. We also tested, and rejected, the hypothesis that the enhancement is due to normal nuclear transitions in the inverse nuclear excitation by electron transition process. The possibility to make measurements with intense laser radiation is considered too. Thus, there appears to be no explanation of these experimental results within quantum electrodynamics and the contemporary concepts of atomic nuclei.

A study of the lattice gas (Ising) model shows the properties of saturated vapor in coexistence with a liquid to be independent of the system's fixed mean density ${\rho }_{\mathrm{fixed}}$, in keeping with standard thermodynamics. This behavior ensures that Fisher scaling plots are unique, independent of ${\rho }_{\mathrm{fixed}}$, and yield a unique characterization of the liquid–vapor phase diagram. The resulting phase diagram and critical parameters for the square lattice gas model are shown to agree with accepted values to within a few percent throughout the coexistence region.

New data on forward neutron emission in fragmentation of $30A-\mathrm{GeV}{}^{208}\mathrm{Pb}$ ions on Al, Cu, Sn, and Pb nuclei are presented. The measurements were performed at the CERN SPS in the framework of the ALICE-LUMI experiment. The measured cross sections are compared with predictions of the RELDIS model for electromagnetic interactions and with results of the abrasion-ablation model for hadronic interactions. The electromagnetic excitation of a Pb projectile followed by single- and double-neutron emission is found to be the dominant process in full agreement with theoretical estimations. The measured $1nX$ cross sections are generally well described. The measured $2nX$ data, which are 4–5 times lower than the $1nX$ data, are slightly underestimated by theory. Nevertheless, the sum of $1nX$ and $2nX$ cross sections is in good agreement with theory. This confirms the predictive power of the RELDIS model, which can be used to calculate the sum of $1nX$ and $2nX$ emission rates for the purpose of calibration of luminosity measurements in PbPb collisions at the Large Hadron Collider at CERN.

The dressed K-matrix model, developed previously for low- and intermediate-energy Compton scattering, is generalized to calculate the photon-nucleon vertex with a virtual photon and an off-shell nucleon. This model was used to compute the ratio of the proton electromagnetic form factors. The calculated ratio is in excellent agreement with the ratio measured in polarized electron-proton scattering.

Photoproduction of the ${\Theta }^{+}$ pentaquark on the proton is analyzed by using isobar and Regge models. The difference in the calculated total cross section is found to be more than two orders of magnitude for a hadronic form-factor cutoff $\Lambda >1\mathrm{GeV}$. Comparable results would be obtained for $0.6\le \Lambda \le 0.8\mathrm{GeV}$. The contribution of the ${\Theta }^{+}$ photoproduction to the GDH integral is also calculated. By comparing with the current phenomenological calculation, it is found that the GDH sum rule favors the result obtained from the Regge approach and isobar model with small Λ.

Excited states in ${}^{166}\mathrm{Hf}$ were populated in the ${\beta }^{+}/\epsilon$ decay of ${}^{166}\mathrm{Ta}$ and studied through off-beam $\gamma$-ray spectroscopy at the Yale moving tape collector. New coincidence data found no support for two previously reported excited $0^{+}$ states and led to a substantially revised level scheme. Similarities between the revised level scheme of ${}^{166}\mathrm{Hf}$ and the X(5) critical point symmetry are discussed, and the extent of X(5) behavior in this mass region is explored through the W and Os isotopes. Among X(5) candidates with $N>90$, good agreement is observed for most energies and interband $B(E2)$ strengths, while all exhibit similar disagreements with other key observables, in particular, yrast $B(E2)$ values and spacing in the excited $K\hspace{1em}=\hspace{1em}{0}^{+}$ sequence.

In the independent-particle model, the nuclear level density is determined from the neutron and proton single-particle level densities. The single-particle level density for the positive-energy continuum levels is important at high excitation energies for stable nuclei and at all excitation energies for nuclei near the drip lines. This single-particle level density is subdivided into compound-nucleus and gas components. Two methods are considered for this subdivision: In the subtraction method, the single-particle level density is determined from the scattering phase shifts. In the Gamov method, only the narrow Gamov states or resonances are included. The level densities calculated with these two methods are similar; both can be approximated by the backshifted Fermi-gas expression with level-density parameters that are dependent on A, but with very little dependence on the neutron or proton richness of the nucleus. However, a small decrease in the level-density parameter is predicted for some nuclei very close to the drip lines. The largest difference between the calculations using the two methods is the deformation dependence of the level density. The Gamov method predicts a very strong peaking of the level density at sphericity for high excitation energies. This leads to a suppression of deformed configurations and, consequently, the fission rate predicted by the statistical model is reduced in the Gamov method.

Classical color fields produced by the small-x wave functions of colliding ultrarelativistic nuclei have been numerically computed. We set up the framework for computing the production of small-mass quark-antiquark pairs in these color fields by numerically integrating the Dirac equation. This computation is essential for understanding the conversion of the initial gluonic state to a chemically equilibrated quark-gluon plasma. To illustrate and overcome technical difficulties associated with the longitudinal dimension, we first consider numerically the case of one time + one longitudinal space dimension.

The influence of the central depression in the density distribution of spherical superheavy nuclei on the shell structure is studied within the relativistic mean-field theory. A large depression leads to the shell gaps at the proton $Z=120$ and neutron $N=172$ numbers, whereas a flatter density distribution favors $N=184$ and leads to the appearance of a $Z=126$ shell gap and to the decrease of the size of the $Z=120$ shell gap. The correlations between the magic shell gaps and the magnitude of the central depression are discussed for relativistic and nonrelativistic mean field theories.