The elastic scattering of ${}^6\mathrm{Li}$ and ${}^6\mathrm{He}$ by ${}^{208}\mathrm{Pb}$ at energies in the vicinity of the Coulomb barrier is studied by means of continuum-discretized coupled-channels calculations. It is shown that the strong reduction of the ${}^6\mathrm{He}{+}^{208}\mathrm{Pb}$ elastic scattering cross section at forward angles is caused by long-range dipole Coulomb excitation of the projectile. The role of breakup in the fusion of halo nuclei is also discussed.

The Landau-Pomeranchuk-Migdal (LPM) suppression of photon emission rates from the quark-gluon plasma have been studied at different temperatures and chemical potentials. The integral equation for the transverse vector function $\mathbf{f}̃\left({\tilde{\mathbf{p}}}_{\perp }\right)$ consisting of multiple scattering effects is solved for the parameter set $\{p_{\Vert },k,\kappa ,T\},$ for bremsstrahlung and off-shell annihilation (aws) processes. The integrated ${\tilde{\mathbf{p}}}_{\perp }\cdot \mathbf{f}̃\left({\tilde{\mathbf{p}}}_{\perp }\right)$ distributions lead to a unique global function $g\left(x\right)\mathrm{}$ that depends only on the dynamical variable x, defined by $x=(T/{\kappa }_0)|{(1/p}_{\Vert })-{(1/p}_{\Vert }+k)|,$ for all temperatures and chemical potentials. Empirical fits to this dimensionless emission function $g\left(x\right)\mathrm{}$ are obtained. The photon emission rate calculations with the LPM suppression effects reduce to one dimensional integrals that involve folding over the empirical $g\left(x\right)\mathrm{}$ function with quark distribution functions and the kinematic factors. The suppression factors for bremsstrahlung and aws obtained from this method have been shown to be consistent with the results of variational method.

We study the threshold $\phi$-meson production in the process $\Delta +\overrightarrow{N}N+N+\phi ,$ which appears as a possible important mechanism in high-energy nucleus-nucleus collisions. The isotopic invariance of the strong interaction and the selection rules due to P parity and total angular momentum result in a general and model independent parametrization of the spin structure of the matrix element in terms of three partial amplitudes. In the framework of one-pion exchange model these amplitudes can be derived in terms of two threshold partial amplitudes for the process $\pi +\overrightarrow{N}N+\phi$ and three amplitudes for the subprocess $\pi +\overrightarrow{\Delta }N+\phi .$ We predict the ratio of cross sections for $\phi$-meson production in $\mathrm{pp}$ and $\Delta N$ collisions and the polarization properties of the $\phi$ meson, in $\Delta +\overrightarrow{N}N+N+\phi .$

Backbending phenomena and low-lying collective states in the nucleus ${}^{132}\mathrm{Ba}$ are studied in terms of a pair-truncated shell model with the monopole and quadrupole pairing plus quadrupole-quadrupole interaction. The model reproduces well experimental energy levels, transition rates, and g factors for both low-lying states and those around the backbending region. The collective pair truncation of the shell-model space yields remarkable results for low-lying states, and the alignment of two ${0h}_{11/2}$ neutrons plays a decisive role in describing the backbending.

The Glauber approximation for the treatment of heavy-ion scattering has already been shown to give reliable predictions for the reaction cross section in the particular case of intermediate energy charge-exchange processes. In the present work, we couple a Glauber-type model to microscopic random phase approximation calculations of the charge-exchange excitations of ${}^{208}\mathrm{Pb}.$ The aim is to solve the long-standing question whether the very elusive charge-exchange isovector monopole has been really identified in the past experiments, or other multipoles were prevalent in the observed spectra.

A schematic model is presented that allows one to study the behavior of interacting neutral isosymmetric pseudo-Fermi matter, locked in a thermostatic box. As a function of the box volume and temperature, the matter is seen to show all of the familiar characteristics of a van der Waals gas, which include the coexistence of two phases under certain circumstances and the presence of a critical point.

The x-ray cascade from antiprotonic atoms was studied for ${}^{106}\mathrm{Cd},$ ${}^{116}\mathrm{Cd},$ ${}^{112}\mathrm{Sn},$ ${}^{116}\mathrm{Sn},$ ${}^{120}\mathrm{Sn},$ and ${}^{124}\mathrm{Sn}.$ Widths and shifts of the levels due to strong interaction were deduced. Isotope effects in Cd and Sn isotopes were investigated. The results are used to determine the nucleon density in the nuclear periphery. The deduced neutron distributions are compared with the results of the previously introduced radiochemical method and with Hartree-Fock-Bogoliubov calculations.

We apply the Lagrange-mesh technique to three-body systems defined in hyperspherical coordinates. The method is applied to ${}^6\mathrm{He}$ (described as $\alpha +n+n)$ and ${}^{12}\mathrm{C}$ (described as $\alpha +\alpha +\alpha ),$ and is shown to be fast and accurate. To deal with two-body forbidden states, we compare the usual projection method with the use of supersymmetric equivalent potentials. Both approaches provide similar spectroscopic properties, although the wave functions can be quite different. We also show that an accurate description of the three-body asymptotics requires bases with large hypermomenta.

Multiple superdeformed bands in the nuclei ${}^{80-83}\mathrm{Sr},$ ${}^{82-84}\mathrm{Y},$ and ${}^{83,84}\mathrm{Zr}$ have been studied in a backed-target experiment, using the Gammasphere and the Microball 4π detector arrays. For 15 bands in these nuclei, average transition quadrupole moments have been measured with high accuracy, using the Doppler-shift attenuation method. Among these are the newly observed superdeformed bands in ${}^{83,84}\mathrm{Y},$ which are “isospectral” with the bands in ${}^{82,83}$ Sr. These “isospectral” bands have nearly identical transition quadrupole moments. Two of the bands in ${}^{81}\mathrm{Sr}$ interact and cross transitions between them are observed. The present measurements place stringent conditions on configuration assignments for the bands obtained from two types of mean-field calculations, leading to a consistent understanding of the mass ∼80 superdeformed bands. The assignments for different bands arise from one or more nucleons occupying the $N_0{=5h}_{11/2}$ intruder orbital.

Cross section differences among the isotopes ${}^{182,184,186}\mathrm{W}$ have been measured as a part of a study of total cross sections in the 5–560 MeV energy range. These difference measurements show oscillations up to 150 mb between 5 and 100 MeV. Calculations with spherical and deformed phenomenological optical potentials employing standard radial and isospin dependences show much smaller oscillations than the experimental data. In a simple Ramsauer model, this discrepancy can be traced to a cancellation between radial and isospin effects. Understanding this problem requires a more detailed model that incorporates a realistic description of the neutron and proton density distributions. This has been done with the results of Hartree-Fock-Bogoliubov calculations using the Gogny force, together with a microscopic folding model employing a modification of the Jeukenne, Lejeune, and Mahaux potential as an effective interaction. This treatment yields a satisfactory interpretation of the observed total cross section differences up to 200 MeV. The calculations have been extended above that energy with a folding model based on an empirical effective interaction.

Differential and total cross sections for the exclusive breakup of a ${}^6\mathrm{Li}$ projectile into $\alpha +d$ and $\alpha +p$ fragments from a ${}^{208}\mathrm{Pb}$ target were measured at several energies around the Coulomb barrier. The $\alpha +d$ exclusive cross sections are well reproduced by full continuum discretized coupled channel calculations with excitation up to 11.5 MeV of the $\alpha +d$ ${(}^6{\mathrm{Li}}^{*})$ system. The total exclusive cross sections are much smaller than the inclusive ones for the production of $\alpha$ particles. This large difference gives very clear experimental evidence for the stripping breakup mechanism. Such a process, relevant in the reaction dynamics even at the Coulomb barrier with loosely bound projectiles such as ${}^6\mathrm{Li},$ needs to be carefully considered and described theoretically.

Typically, the materialization of highly energetic transverse partons to hadronic jets is assumed to occur outside the reaction zone in a relativistic heavy ion collision. In contrast, a quantum mechanical estimate yields a time on the order of only a few fm/c for building up the hadronic wave function for jets with typical transverse momenta of $p_{\perp }<~10\mathrm{GeV},$ as accessible at Relativistic Heavy Ion Collider (RHIC) facilities. The role of possible elastic or inelastic collisions of these high $p_{\perp }$ particles with the bulk of hadrons inside the fireball is addressed by means of an opacity expansion in the number of collisions. This analysis shows that the hadronic final state interactions can, in principle, account for the modification of the (moderate) high $p_{\perp }$ spectrum observed for central collisions at RHIC.

We utilize the existing next-to-leading-order (NLO) formalism to calculate the partonic structure of a constituent quark. The structure of any hadron can be obtained thereafter using a convolution method. Such a procedure is used to generate the structure functions of protons and pions in NLO, neglecting certain corrections to ${\Lambda }_{\mathrm{QCD}}.$ It is shown that while the constituent quark structure is generated purely perturbatively and accounts for the most part of the hadronic structure, there is a few percent contribution coming from the nonperturbative sector in the hadronic structure. This contribution plays the key role in explaining the SU(2) symmetry breaking of the nucleon sea and the observed violation of the Gottfried sum rule. These effects are calculated. We obtained an excellent agreement with the experimental data in a wide range of $x=[{10}^{-6},1\mathrm{}]$ and $Q^2=[0.5,5000]{\mathrm{GeV}}^2$ for the proton structure function. We have also calculated pion structure and compared it with the existing data. Again, the model calculations agree rather well with the data from experiment.

We study the spectrum of scalar-isoscalar excitations in the color-flavor locked phase of dense quark matter. The sigma meson in this phase appears as a four-quark state (of diquark and antidiquark) with a well-defined mass and extremely small width, as a consequence of its small coupling to two pions. The quark particle/hole degrees of freedom also contribute significantly to the correlator just above the threshold $2\Delta ,$ where $\Delta$ is the superconducting gap.

Electromagnetic processes in loosely bound nuclei are investigated using an analytical model. In particular, electromagnetic dissociation of ${}^8\mathrm{B}$ is studied and the results of our analytical model are compared to numerical calculations based on a three-body picture of the ${}^8\mathrm{B}$ bound state. The calculation of energy spectra is shown to be strongly model dependent. This is demonstrated by investigating the sensitivity to the rms intercluster distance, the few-body behavior, and the effects of final state interaction. In contrast, the fraction of the energy spectrum which can be attributed to $E1\mathrm{}$ transitions is found to be almost model independent at small relative energies. This finding is of great importance for astrophysical applications as it provides us with a new tool to extract the $E1\mathrm{}$ component from measured energy spectra. An additional, and independent, method is also proposed as it is demonstrated how two sets of experimental data, obtained with different beam energy and/or minimum impact parameter, can be used to extract the $E1\mathrm{}$ component.

The experimental results of particle multiplicity distributions in silicon-emulsion collisions at $4.5A\mathrm{GeV}/c$ (the Dubna synchrophasotron momentum) are reported. The correlations between the multiplicities of target fragments are given. The saturation effect of target black fragment multiplicity in the collisions is observed.

The nuclear-polarization (NP) energies with the collective model commonly employed in the NP calculations for hydrogenlike heavy ions are found to have serious gauge violations when the ladder and cross diagrams only are taken into account. Using the equivalence of charge-current density with a schematic microscopic model, the NP energy shifts with the collective model are gauge invariantly evaluated for the ${1s}_{1/2}$ states in ${}_{82}^{208}{\mathrm{Pb}}^{81+}$ and ${}_{92}^{238}{\mathrm{U}}^{91+}.$

The contribution of thermally excited electron-positron pairs to the bulk properties of the color-flavor locked quark phase inside compact stars is examined. The presence of these pairs causes the photon mean free path to be much smaller than a typical core radius ${(R}_0\simeq 1\mathrm{km})$ for all temperatures above 25 keV so that the photon contribution to the thermal conductivity is much smaller than that of the Nambu-Goldstone bosons. We also find that the electrons and positrons dominate the electrical conductivity, while their contributions to the total thermal energy is negligible.

The thick target inverse kinematic method was applied to the study of isobaric analog states in the neutron-rich nucleus ${}^9\mathrm{Li}.$ For this purpose, an excitation function for ${}^8\mathrm{He}+p$ elastic scattering was measured in the center-of-momentum energy range from 1.6 to 5.8 MeV. Three $T=5/2\mathrm{}$ states in ${}^9\mathrm{Li}$ (isobaric analogs of ${}^9\mathrm{He})$ were observed. Restrictions on the spin-parity assignments are provided according to R-matrix calculations, and conclusions regarding the structure of ${}^9\mathrm{He}$ are given.

We study the energy level statistics of the states in U(5) and O(6) dynamical symmetries of the interacting boson model and the high spin states with backbending in U(5) symmetry. In the calculations, the degeneracy resulting from the additional quantum number is eliminated manually. The calculated results indicate that the finite boson number N effect is prominent. When N has a value close to a realistic one, increasing the interaction strength of subgroup O(5) makes the statistics vary from Poisson type to Gaussian orthogonal ensemble type and further recover to Poisson type. However, in the case of $\overrightarrow{N}\infty ,$ they all tend to be Poisson type. The fluctuation property of the energy levels with backbending in high spin states in U(5) symmetry involves a signal of shape-phase transition between spherical vibration and axial rotation.