The recent advent of experimental techniques in which the dynamical characteristics of fission fragments are determined more accurately prompted us to investigate the angular momentum acquired by fragments in a model which describes the cold (neutronless) fission of ${}^{252}\mathrm{Cf}$ as the decay of a giant nuclear molecule. The molecular configuration is a consequence of the interplay between the attractive nuclear part and the repulsive Coulomb+nuclear forces. The basic idea of the present approach is to separate the radial (fission) modes describing the decay of the molecule from the modes associated to transversal vibrations (bending) of the fragments. The distance between the centers of the two fragments is fixed by the requirement that the energy released in the fission reaction Q equals the sum of quantum zero energies of radial and transversal modes and the total excitation energy $E^{*}.$ Using a semiclassical coupled channel formalism we computed the additional angular momenta acquired by the fragments during their postscission motion, and found that the Coulomb excitation accounts for less than 10% of the final spins.

Energy-integrated reaction cross sections have been measured at energies ranging from 38 to 80 MeV/nucleon for various exotic neutron-rich isotopes of Al, Si, P, S, Cl, Ar, K, Ca, Sc, and Ti stopping in Si. An experimental technique is employed where Si detectors are used for both particle identification and to serve as the target material. The reduced strong absorption radii $r_0^2$ are deduced and compared with other experimental results. The radius dependence on the neutron number was studied and a trend of increasing reduced radius with neutron excess was found. This behavior is similar to that seen in lighter systems, although less pronounced than found there. The implications of this result on the conjectured existence of neutron halo or skin nuclei is discussed.

Elastic and inelastic proton scattering has been measured in inverse kinematics on the unstable nucleus ${}^{40}\mathrm{S}$. A phenomenological distorted wave Born approximation analysis yields a quadrupole deformation parameter ${\beta }_2=0.35\mathrm{}\pm 0.05$ for the $2_1^{+}$ state. Consistent phenomenological and microscopic proton scattering analyses have been applied to all even-even sulfur isotopes from $A=32\mathrm{}$ to $A=40\mathrm{}$. The second analysis used microscopic collective model densities and a modified Jeukenne-Lejeune-Mahaux nucleon-nucleon effective interaction. This microscopic analysis suggests the presence of a neutron skin in the heavy sulfur isotopes. The analysis is consistent with normalization values for ${\lambda }_v$ and ${\lambda }_w$ of 0.95 for both the real and imaginary parts of the Jeukenne-Lejeune-Mahaux potential.

We evaluate the bremsstrahlung production of low mass dileptons and soft photons from equilibrating and transversely expanding quark gluon plasma which may be created in the wake of relativistic heavy ion collisions. We use initial conditions obtained from the self-screened parton cascade model. We consider a boost invariant longitudinal and cylindrically symmetric transverse expansion of the parton plasma and find that for low mass dileptons $(M<~0.3\hspace{0.5em}\mathrm{GeV})$ and soft photons ${(p}_T<~0.5\hspace{0.5em}\mathrm{GeV}),$ the bremsstrahlung contribution is rather large compared to annihilation process at both the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) energies. We also find an increase by a factor of 15–20 in the low mass dileptons and soft photons yield as one goes from RHIC to LHC energies.

A combined analysis of new eta photoproduction data for total and differential cross sections, target asymmetry, and photon asymmetry is presented. Using a few reasonable assumptions we perform the first model-independent analysis of the $E_{0+},$ $E_{2-},$ and $M_{2-}$ eta photoproduction multipoles. Making use of the well-known $A_{3/2}$ helicity amplitude of the $D_{13}\mathrm{}\left(1520\right)\mathrm{}$ state, we extract its branching ratio to the $\eta N$ channel, ${\Gamma }_{\eta N}/\Gamma =(0.08\mathrm{}\pm 0.01)\%$. At higher energies, we show that the photon asymmetry is extremely sensitive to small multipoles that are excited by photons in the helicity $3/2$ state. The new GRAAL photon asymmetry data at higher energy show a clear signal of the $F_{15}\mathrm{}\left(1680\right)\mathrm{}$ excitation which permits extracting an $F_{15}\mathrm{}\left(1680\right)\mathrm{}\to \eta N$ branching ratio of ${(0.15\mathrm{}}_{-0.10}^{+0.35\mathrm{}})\%$.

The statistical properties of the charmonium energy spectrum determined by the Bethe-Salpeter equation are investigated. It is found that the regular motion of the $c\overline{c}$ system can be expected at a small value of color screening mass but the chaotic motion is expected at a large one. It is shown that the level mixing due to color screening serves as a new mechanism resulting in the $J/\psi$ suppression. Moreover, this kind of suppression can occur before the color screening mass reaches its critical value for $J/\psi$ dissociation. This implies that a strong $J/\psi$ suppression is possible in the absence of dissociation of $J/\psi .$

We propose a new method to analyze fluctuations in the strength function phenomena in highly excited nuclei. Extending the method of multifractal analysis to the cases where the strength fluctuations do not obey power scaling laws, we introduce a new measure of fluctuation, called the local scaling dimension, which characterizes scaling behavior of the strength fluctuation as a function of energy bin width subdividing the strength function. We discuss properties of the new measure by applying it to a model system which simulates the doorway damping mechanism of giant resonances. It is found that the local scaling dimension well characterizes fluctuations and their energy scales of fine structures in the strength function associated with the damped collective motions.

The yrast superdeformed band in ${}^{61}\mathrm{Zn}$ has been established using ${}^{28}\mathrm{Si}{(}^{36}\mathrm{Ar},$ ${2pn)}^{61}\mathrm{Zn}$ and ${}^{40}\mathrm{Ca}{(}^{29}\mathrm{Si},$ $2\alpha {)}^{61}\mathrm{Zn}$ fusion-evaporation reactions. The excitation energy of this band was determined via two transitions that link this band to the normally deformed states. Lifetime analysis of this band resulted in a quadrupole moment of $Q_t=3.0\mathrm{}{\pm }_{0.4}^{0.5}e\mathrm{b},$ which corresponds to a deformation of ${\beta }_2=0.50\mathrm{}{\pm }_{0.06}^{0.07}.$ A comparison of the $J^{\mathrm{}\left(2\right)\mathrm{}}$ dynamical moments of inertia of the yrast superdeformed band in ${}^{61}\mathrm{Zn}$ with those in ${}^{60}\mathrm{Zn}$ shows a nearly complete blocking of the observed alignment in ${}^{60}\mathrm{Zn},$ indicating that $T=0\mathrm{}$ proton-neutron pair correlations may be present in ${}^{60}\mathrm{Zn}.$

The onset of chaos in the characteristics of the hot giant dipole resonance (GDR) is studied through the evolution of the hot GDR as a function of temperature and time. The strength distribution, the time correlation function, and the logarithm of the total number of transitions of magnitude smaller than a given threshold value have been calculated using the phonon-damping model for the hot GDR in ${}^{120}\mathrm{Sn}.$ The results show that the existence of the hot GDR, even at high temperatures, is a manifestation of the coexistence of order and chaos in highly excited nuclei.

This work addresses the question of precisely what features of few body models of halo nuclei are probed by elastic scattering on protons at high center-of-mass energies. Our treatment is based on a multiple scattering expansion of the proton-projectile transition amplitude in a form which is well adapted to the weakly bound cluster picture of halo nuclei. In the specific case of ${}^{11}\mathrm{Li}$ scattering from protons at 800 MeV/nucleon we show that because core recoil effects are significant, scattering cross sections cannot, in general, be deduced from knowledge of the total matter density alone. We advocate that the optical potential concept for the scattering of halo nuclei on protons should be avoided and that the multiple scattering series for the full transition amplitude should be used instead.

We derive analytic expressions for the energies and $B\left(E2\mathrm{}\right)\mathrm{}$-transition probabilities in the states of the ground and $\gamma$ bands of heavy deformed nuclei within a collective vector-boson model with SU(3) dynamical symmetry. On this basis we examine the analytic behavior of the SU(3) energy splitting and the $B\left(E2\mathrm{}\right)\mathrm{}$ interband transition ratios in the SU(3) contraction limits of the model. The theoretical analyses outline physically reasonable ways in which the ground-$\gamma$ band coupling vanishes. The experimental data on the lowest collective states of even-even rare earth nuclei and actinides strongly support the theoretical results. They suggest that a transition from the ground-$\gamma$ band coupling scheme to a scheme in which the ground band is situated in a separate irreducible representation of SU(3) should be realized towards the midshell regions. We propose that generally the SU(3) group contraction process should play an important role for such transitions in any collective band coupling scheme in heavy deformed nuclei.

The production of negative strangeness in reactions of inelastic antineutrino scattering on a nucleus provides information on the modification of strange degrees of freedom in nuclear matter. We calculate cross sections of the reaction channels ${\overline{\nu }}_{e\left(\mu \right)}\to e^{+}({\mu }^{+}{)+K}^{-}$ and ${\overline{\nu }}_{e\left(\mu \right)}+\overrightarrow{p}\Lambda {+e}^{+}\left({\mu }^{+}\right)$ and investigate their sensitivity to the medium effects. In particular, we consider effects induced by the presence of a low-energy excitation mode in the $K^{-}$ spectrum, associated with correlated Λ-particle and proton-hole states, and by renormalization of the weak interaction in medium. In order to avoid double counting, various contributions to antineutrino scattering are classified with the help of the optical theorem, formulated within the nonequilibrium Green’s function technique.

Elastic scattering angular distributions have been measured for the system ${}^{12}\mathrm{C}{+}^{209}\mathrm{Bi}$ at ten energies between 58.9 to 87.4 MeV. Optical model analysis of these, together with existing data at 118 MeV, using both phenomenological and microscopic models, shows a pronounced energy dependence of the optical potential. Fusion cross sections have been deduced, by a barrier penetration model and by subtracting the direct reaction contributions from the reaction cross sections. Threshold anomaly of the optical potential has been explained both by dispersion relation and by coupled reaction channel (CRC) calculations. The CRC calculations, including inelastic excitation and transfer channels, reproduce simultaneously the elastic, inelastic, and transfer angular distributions measured at 61.9, 63.9, and 87.4 MeV. Comparison of threshold anomaly results for ${}^4\mathrm{He},{\hspace{0.5em}}^{11}\mathrm{B},{\hspace{0.5em}}^{16}\mathrm{O}{+}^{209}\mathrm{Bi}$ systems along with the present case indicates that the degree of anomaly increases with the projectile mass.

An electromagnetic field produced in high-energy heavy-ion collisions contains much useful information, because the field can be directly related to the motion of the matter in the whole stage of the reaction. One can divide the total electromagnetic field into three parts, i.e., the contributions from the incident nuclei, nonparticipating nucleons, and charged fluid, the latter consisting of strongly interacting hadrons or quarks. Parametrizing the space-time evolution of the charged fluid based on hydrodynamic model, we study the development of the electromagnetic field which accompanies the high-energy heavy-ion collisions. We found that the incident nuclei bring a rather strong electromagnetic field to the interaction region of hadrons or quarks over a few fm after the collision. On the other hand, the observed charged hadrons’ spectra are mostly affected (Coulomb effect) by the field of the charged fluid. We compare the result of our model with experimental data and found that the model reproduces them well. The pion yield ratio ${\pi }^{-}/{\pi }^{+}$ at a RHIC energy, Au+Au 100+100 GeV/nucleon, is also predicted.

We introduce coupled channels of ladder Bethe-Salpeter mesons both in the bound state equation for mesons and in the mass gap equation for chiral symmetry. Consistency is insured by the Ward identities for axial currents, which preserve the Goldstone boson nature of the pion and prevent a systematic shift of the hadron spectrum. We study the decay of a scalar meson coupled to a pair of pseudoscalars. We also show that coupled channels reduce the breaking of chiral symmetry, with the same Feynman diagrams that appear in the coupling of a scalar meson to a pair of pseudoscalar mesons. Exact calculations are performed in a particular confining quark model, where we find that the ground state $I=0,$ ${}^3{P}_0\hspace{0.5em}q\overline{q}$ meson is the $f_0\mathrm{}\left(980\right)\mathrm{}$ with a partial decay width of 40 MeV. We also find a 30% reduction of the chiral condensate due to coupled channels.

Using a microscopic transport model together with a coalescence afterburner, we study the formation of deuterons in Au+Au central collisions at $\sqrt{s}=200A\hspace{0.5em}\mathrm{GeV}.$ It is found that the deuteron transverse momentum distributions are strongly affected by the nucleon space-momentum correlations, at the moment of freeze-out, which are mostly determined by the number of rescatterings. This feature is useful for studying collision dynamics at ultrarelativistic energies.

We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models—the Skyrme-Hartree-Fock approach and the relativistic mean-field model—using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of ${}^{208}\mathrm{Pb}$ and the spin-orbit splittings of selected neutron and proton levels in ${}^{16}\mathrm{O},$ ${}^{132}\mathrm{Sn},$ and ${}^{208}\mathrm{Pb}.$ While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%–80%, which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at ${}_{184}^{298}114,$ ${}_{172}^{292}120,$ or ${}_{184}^{310}126$ depending on the parametrization. The $Z=114\mathrm{}$ proton shell closure, which is related to a large spin-orbit splitting of proton $2f$ states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in ${}^{208}\mathrm{Pb}.$ The $Z=120\mathrm{}$ and $N=172\mathrm{}$ shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for ${}_{172}^{292}120$ to be the next spherical doubly magic superheavy nucleus.

Exclusive studies of angular distributions for intermediate-mass fragments (IMFs) produced in GeV hadron-induced reactions have been performed with the Indiana Silicon Sphere (ISiS) 4π detector array. Special emphasis has been given to understanding the origin of sideways peaking, which becomes prominent in the angular distributions for beam momenta above about $10\hspace{0.5em}\mathrm{GeV}/c.\mathrm{}$ Both the magnitude of the effect and the peak angle increase as a function of fragment multiplicity and charge. When gated on IMF kinetic energy, the angular distributions evolve from forward-peaked to near isotropy as the fragment kinetic energy decreases. Fragment-fragment angular-correlation analyses show no obvious evidence for a dynamic mechanism that might signal shock wave effects or the breakup of exotic geometric shapes such as bubbles or toroids. Moving-source and intranuclear cascade simulations suggest that the observed sideways peaking is of kinematic origin, arising from significant transverse momentum imparted to the heavy recoil nucleus during the fast cascade stage of the collision. A two-step cascade and statistical multifragmentation calculation is consistent with this assumption.

The $\alpha$ decays of the two neutron-deficient nuclei ${}^{172}\mathrm{Hg}$ and ${}^{173}\mathrm{Hg}$ were observed for the first time using the ${}^{78}\mathrm{Kr}{(}^{96}\mathrm{Ru},2n)$ and ${}^{80}\mathrm{Kr}{(}^{96}\mathrm{Ru},3n)$ reactions, respectively. The reaction products were dispersed according to their mass-to-charge state ratios in the Argonne Fragment Mass Analyzer and implanted in a double-sided silicon strip detector, where their subsequent decays were studied using spatial and time correlations between implants and decays. A half-life of ${250(}_{-90}^{+350\mathrm{}})\hspace{0.5em}\mu \mathrm{s}$ and an energy of 7350(12) keV were deduced for the $\alpha$ decay of ${}^{172}\mathrm{Hg}$. In ${}^{173}\mathrm{Hg}$ the half-life was measured to be ${0.93(}_{-0.26}^{+0.57\mathrm{}})\hspace{0.5em}\mathrm{ms}$ and the corresponding energy is 7211(11) keV. In addition, the half-life and energy of the $\alpha$ decay of ${}^{174}\mathrm{Hg}$ were measured more precisely. The reduced widths deduced for these Hg isotopes indicate that the observed decays correspond to unhindered $\Delta l=0\mathrm{}$ transitions. The $\alpha$-decay Q values are compared with the values calculated using mass tables by Möller and Nix, and by Liran and Zeldes. The latter mass tables show better agreement with the data.

The resilience to averaging over an initial energy distribution of reducibility and thermal scaling observed in nuclear multifragmentation is studied. Poissonian reducibility and the associated thermal scaling of the mean are shown to be robust. Binomial reducibility and thermal scaling of the elementary probability are robust under a broad range of conditions. The experimental data do not show any indication of deviation due to averaging.