Using the mass predictions of the recently developed infinite nuclear matter model of atomic nuclei, we show here that the classical magic numbers disappear under exotic condition of neutron or proton excess. This localized nature of the magic numbers supports the reported strong quenching of the magic shells implied from the study of astrophysical r-process nuclidic abundances, and in agreement with the experimental trends observed in the low-mass region. An important offshoot of the present study is the identification of the characteristic local energies of the model as the carrier of shell structure.

Proton and deuteron distributions from $11.6A\hspace{0.5em}\mathrm{GeV}/c$ Au + Au collisions measured by the E802 Collaboration in experiment E-866 are presented. The invariant yield of protons and deuterons is studied as a function of the transverse mass for different cuts of rapidity and centrality. At low $m_t-m_0$ the proton and deuteron invariant spectra deviate from a single exponential shape. The average $m_t$ as function of centrality and rapidity is used to explore the effect of collective transverse flow in the reaction. The ratio of the deuteron to squared proton yield as a function of transverse momentum, rapidity, and centrality is used to probe the coalescence model of deuteron production. This ratio is constant as a function of rapidity only for the most central cuts and decreases with the centrality for every rapidity cut. The ratio of the differential cross section of the deuteron to the squared differential cross section of the proton, for the most central cut, is not constant as a function of $m_t-m_0.$

The binary decay of very light nuclear systems into the ground state exit channel has been investigated for light heavy-ion collisions at energies ranging from the Coulomb barrier up to $\sim 4\hspace{0.5em}\mathrm{MeV}$ per nucleon. A systematic analysis of 14 reactions and up to 50 angular distributions allowed the extraction of the energy thresholds ${(E}_{\mathrm{ef}})$ for the fission channel forming the final products at the ground state (“elastic fission”). A significant suppression of the contribution of statistical processes is observed when the size of the system is reduced. This effect may be related to a relative increase of the fast and peripheral yields.

Spin distributions of fission fragments have been measured in ${}^{12}\mathrm{C},$ ${}^{16}\mathrm{O},$ ${}^{19}\mathrm{F}{+}^{209}\mathrm{Bi},$ and ${}^{232}\mathrm{Th}$ reactions at near and above barrier energies. It is found that the collective spin modes are suppressed for fragment emission along $90°$ in comparison to the forward-backward emission angles. The suppression factor exhibits a universal scaling with respect to the rotational frequency of the fissioning nucleus along the fission symmetry axis. The analysis of data from the present measurements, as well as those available from the literature, shows that the suppression of collective spin degrees of freedom has the form ${\mathrm{S}}_{\mathrm{coll}}\left(\theta \right)=\exp \left(-\Delta E\right(\theta )/T){\mathrm{S}}_{\mathrm{coll}}\left(0\mathrm{}°\right),$ where $\Delta E\left(\theta \right)$ is the excitation energy in the tilting mode characterized by the K quantum number.

We study the structure of excited states of ${}^{10}\mathrm{Be}$ with the method of variation after spin-parity projection in the framework of antisymmetrized molecular dynamics. Present calculations describe many excited states and reproduce the experimental data of $E2\mathrm{}$ and $E1\mathrm{}$ transitions and the new data of the $\beta$ transition strength successfully. We include systematic discussions on the moleculelike structures of light unstable nuclei and the important role of the valence neutrons based on the results obtained with the framework which is free from such model assumptions as the existence of inert cores and clusters.

A parameter-free method is proposed for the analysis of the ${(d,}^2\mathrm{He})$ reaction. The three-body final state is treated in the adiabatic approximation. The method is successfully applied to the data at 270 MeV on ${}^{12}\mathrm{C}$ target.

Quark light cone momentum distributions in the nucleon are calculated in a relativistic three-body approach to the Nambu–Jona-Lasinio model by using a simple “static approximation” for the Faddeev kernel. A method is presented which automatically satisfies the number and momentum sum rules, even in the regularized theory. In order to assess the sensitivity to the regularization scheme, two schemes which can be formulated in terms of light cone variables are discussed. The effects of the (composite) pion cloud are taken into account in a convolution approach, and the violation of the Gottfried sum rule is discussed. After performing the $Q^2$ evolution, the resulting distributions are compared to the empirical ones.

We compare precise analyzing power measurements for $p+d$ elastic scattering between 70 and 200 MeV proton laboratory energy with three-body Faddeev calculations. Using the CD-Bonn nucleon-nucleon force alone leads to an overprediction of the data at higher energies, suggesting that three-body $\mathrm{}\left(3NF\right)\mathrm{}$ forces may be important. The $2\pi$-exchange Tuscon-Melbourne $3NF$ model, adjusted to match the triton binding energy, leads to a better shape for the excitation function but gives too large of an effect.

Three new high-$K$ multiquasiparticle intrinsic states, $K^{\pi }{=(29\mathrm{}}^{+}),$ $K^{\pi }{=30\mathrm{}}^{+},$ and $K^{\pi }{=(34\mathrm{}}^{+}),$ have been assigned in ${}^{178}\mathrm{W}.$ The configurations of these states are based on ten, eight, and ten, unpaired nucleons, respectively, and they represent the highest-seniority intrinsic K states observed to date. The $\gamma$-ray intensity branching ratios and associated $|g_K-g_R|$ values have been used to contribute to the specifications of the underlying single-particle configurations of the states. Configuration-constrained potential energy surface calculations indicate that the nucleus retains stably deformed axially symmetric shapes. This evidence, coupled with the experimental $\gamma$-ray decay rates, suggests that K remains a good quantum number in these highest-seniority intrinsic state configurations. The aligned angular momenta of the $K^{\pi }{=(29\mathrm{}}^{+}),$ $K^{\pi }{=30\mathrm{}}^{+},$ and $K^{\pi }{=(34\mathrm{}}^{+})$ bands are observed to be lower than those of the other eight quasiparticle, $K^{\pi }{=25\mathrm{}}^{+}$ and $K^{\pi }{=28\mathrm{}}^{-}$ bands in ${}^{178}\mathrm{W}.$ These differences are interpreted as the effects of reduced pairing due to blocking by the constituent particles. While the dynamic moments of inertia are similar, they remain substantially less than those of a classical rigid rotor, apparently saturating at a value of about $56{ħ}^2\hspace{0.5em}{\mathrm{MeV}}^{-1}.$

We approach the gross structure of compressed nuclei by scaling ground-state relativistic Thomas-Fermi (RTF) densities as well as by performing RTF calculations with a density-dependent constraint as the equivalent for an external pressure. For the NL1 parametrization of the nuclear effective Lagrangian the line of $\beta$ stability as well as the proton drip lines are found to be bended to neutron-richer nuclei with increasing compression. In addition we conclude from calculated critical ${(Z}^2{/A)}_{\mathrm{crit}}$ values that fission barriers are appreciably reduced by the presence of an external pressure.

The onset of instabilities, in the standard proton-neutron quasiparticle random phase approximation (QRPA), is investigated by using different boson mappings and trial states belonging to a representation of coherent states. The model describes pairing and proton-neutron interactions. It is shown that an exact mapping of the Hamiltonian is needed to describe correctly the QRPA phase transition, i.e., that the algebra of all operators participant in the Hamiltonian should be preserved by the boson mapping. Spurious components of the wave functions, which appear if the Pauli principle is violated, are isolated by construction.

The production of positron-electron pairs in collisions of ${}^{238}\mathrm{U}{+}^{232}\mathrm{Th}$ at 5.95 MeV/nucleon, and of ${}^{238}\mathrm{U}{+}^{181}\mathrm{Ta}$ at 5.95, 6.1, and 6.3 MeV/nucleon, has been studied with the APEX spectrometer at Argonne National Laboratory. Several analyses have been performed to search for sharp structures in sum-energy spectra for positron-electron pairs. Such features have been reported in previous experiments. No statistically convincing evidence for such behavior is observed in the present data.

Proton spectra from the ${}^{20}\mathrm{Ne}{\mathrm{}(n,p)\mathrm{}}^{20}\mathrm{F}$ reaction induced by 298 MeV neutrons have been measured for angles between 14° and 32°, angles at which the excitation of the stretched $6^{-}$ states is expected to be observed. The results are presented and are compared with those from the ${}^{20}\mathrm{Ne}\mathrm{}(p,n)\mathrm{}$ reaction study of Tamimi et al. [Phys. Rev. C 45, 1005 (1990)] and the calculations of Carr et al. [Phys. Rev. C 45, 1145 (1990)].

The Λ single-particle energies $B_{\Lambda }$ of hypernuclei (HN) are calculated microscopically using the Fermi hypernetted chain method to obtain for our $\Lambda N$ and $\Lambda \mathrm{NN}$ potentials the Λ binding $D\left(\rho \right)$ to nuclear matter, and the effective mass $m_{\Lambda }^{*}\left(\rho \right)$ at densities $\rho <~{\rho }_0$ $({\rho }_0$ is normal nuclear density), and also the corresponding effective $\Lambda N$ and $\Lambda \mathrm{NN}$ potentials. The Λ core-nucleus potential $U_{\Lambda }\mathrm{}\left(r\right)\mathrm{}$ is obtained by suitably folding these into the core density. The Schrödinger equation for $U_{\Lambda }$ and $m_{\Lambda }^{*}$ is solved for $B_{\Lambda }.$ The fringing field (FF) due to the finite range of the effective potentials is theoretically required. We use a dispersive $\Lambda \mathrm{NN}$ potential but also include a phenomenological ρ dependence allowing for less repulsion for $\rho <{\rho }_0,$ i.e., in the surface. The best fits to the data with a FF give a large ρ dependence, equivalent to an A dependent strength consistent with variational calculations of ${}_{\mathrm{\Lambda }}^5\mathrm{He},$ indicating an effective $\Lambda \mathrm{NN}$ dispersive potential increasingly repulsive with A whose likely interpretation is in terms of dispersive plus two-pion-exchange $\Lambda \mathrm{NN}$ potentials. The well depth is $29\pm 1\mathrm{MeV}.$ The $\Lambda N$ space-exchange fraction corresponds to $m_{\Lambda }^{*}\left(\rho \right)\approx 0.75–0.80$ and a ratio of p- to s-state potentials of $\approx 0.5\pm \mathrm{0.1.}$ Charge symmetry breaking (CSB) is significant for heavy HN with a large neutron excess; with a FF the strength agrees with that obtained from the $A=4\mathrm{}\mathrm{HN}.$ The fits without FF are excellent but inconsistent with the requirement for a FF, with ${}_{\mathrm{\Lambda }}^5\mathrm{He},$ and also with the CSB sign for $A=4.\mathrm{}$

The masses and decay constants of the light vector mesons $\rho /\omega ,$ $\phi ,$ and $K^{\star }$ are studied within a ladder-rainbow truncation of the coupled Dyson-Schwinger and Bethe-Salpeter equations of QCD with a model two-point gluon function. The approach is consistent with quark and gluon confinement, reproduces the correct one-loop renormalization group behavior of QCD, generates dynamical chiral symmetry breaking, and preserves the relevant Ward identities. The one phenomenological parameter and two current quark masses are fixed by requiring that the calculated $f_{\pi },$ $m_{\pi },$ and $m_K$ are correct. The resulting $f_K$ is within 3% of the experimental value. For the vector mesons, all eight transverse covariants are included and the dominant ones are identified; the complete angle dependence of the amplitudes is also retained. The calculated values for the masses $m_{\rho },$ $m_{\phi },$ and $m_{K^{\star }}$ are within 5%, while the decay constants $f_{\rho },$ $f_{\phi },$ and $f_{K^{\star }}$ for electromagnetic and leptonic decays are within 10% of the experimental values.

We discuss the structural effects in the spin-orbit density part of the nucleus-nucleus potential, calculated within the framework of the Skyrme energy density formalism. The structural effects are analyzed by considering a two-nucleon transfer process in both the $\alpha$ and non-$\alpha$ colliding nuclei. We find that the spin-orbit density part of the nucleus-nucleus potential shows a preference for the $\alpha$-nuclei transfers in the $\alpha$ multiplier $\mathrm{}(N=Z,A=4n)\mathrm{}$ colliding nuclei, which diminishes for the non-$\alpha$ multiplier nuclei. Such $\alpha$-transfer effects are found to be related to the closure of the last j shell(s) of the product nucleus (nuclei), for both protons and neutrons. The interesting result is that this effect is shown to exist both for the number of valence particles and the weighted number of valence particles, called particle strength.

We investigate the $p\overrightarrow{p}{\mathrm{pK}}^{+}\Lambda$ reaction within an effective Lagrangian model where the contributions to the amplitudes are taken into account within the tree level. The initial interaction between the two nucleons is modeled by the exchange of $\pi ,$ $\rho ,$ $\omega ,$ and $\sigma$ mesons, and the $\Lambda K^{+}$ production proceeds via the excitation of the $N^{*}\mathrm{}\left(1650\right),$ $N^{*}\mathrm{}\left(1710\right),$ and $N^{*}\mathrm{}\left(1720\right)\mathrm{}$ baryonic resonances. The parameters of the model at the nucleon-nucleon-meson vertices are determined by fitting the elastic nucleon-nucleon scattering with an effective interaction based on the exchange of these four mesons, while those at the resonance vertices are calculated from the known decay widths of the resonances as well as the vector meson dominance model. Available experimental data is described well by this approach. The one-pion-exchange diagram dominates the production process at both higher and lower beam energies. The $\rho$ and $\omega$ meson exchanges make negligible contributions. However, the $\sigma$-exchange processes contribute substantially to the total cross sections at lower beam energies. The excitation of the $N^{*}\mathrm{}\left(1710\right)\mathrm{}$ and $N^{*}\mathrm{}\left(1650\right)\mathrm{}$ resonances dominate this reaction at beam momenta above and below $3\mathrm{GeV}/c,$ respectively. The interference among the amplitudes of various resonance excitation processes is significant. For beam energies very close to the $K^{+}$ production threshold the hyperon-proton final state interaction effects are quite important. The data is selective about the model used to describe the low-energy scattering of the two final state baryons.

We have studied the residual interaction effects theoretically on the deeply bound pionic states which have been observed recently. In order to extract precise information on the pion-nucleus optical potential, we need to evaluate the residual interaction effects on the pionic states. The S-wave $\pi N$ interaction is used for the pion-nucleon residual interaction. We show that the complex eigenenergies vary typically about 0–20 keV and that the effects should be taken into account carefully in the analysis of data with high precision.

Angular distributions of cross sections and complete sets of analyzing powers for the ${}^3\mathrm{He}(\overrightarrow{d}{,p)}^4\mathrm{He}$ reaction have been measured at five energies between $E_d=60\mathrm{}$ and 641 keV. The energy dependence of the cross section was also measured from 245 to 685 keV, and the absolute cross section was determined at $E_d=426\mathrm{}\mathrm{keV}.$ The data have been included in an R-matrix analysis of the ${}^5\mathrm{Li}$ system. The bare-nuclear cross section derived from the R-matrix parametrization was used to determine the electron screening potential.