Total reaction cross sections are predicted for nucleons scattering from various nuclei. Projectile energies up to 300 MeV are considered. So also are mass variations of those cross sections at selected energies. All predictions have been obtained from coordinate space optical potentials formed by full folding effective two-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ interactions with one-body density matrix elements of the nuclear ground states. Good comparisons with data result when effective $\mathrm{NN}$ interactions defined by medium modification of free $\mathrm{NN}$ t matrices are used. Coupled with analyses of differential cross sections, these results are sensitive to details of the model ground states used to describe nuclei.

Longitudinal momentum distributions of ${}^7\mathrm{Be}$ fragments following the dissociation of ${}^8\mathrm{B}$ on heavy, highly charged target nuclei show forward-aft asymmetries, the result of interference of electric quadrupole $\mathrm{}\left(E2\mathrm{}\right)\mathrm{}$ transitions with the dominant $E1\mathrm{}$ excitation process. These asymmetries can therefore be used to gain insight into the $E2\mathrm{}$ contributions to the breakup process. To assess the sensitivity of these $E2\mathrm{}$ interference terms to the assumed reaction mechanism, in particular, the role of higher-order coupling effects at medium energies, coupled discretized continuum channels (CDCC) calculations are carried out for ${}^8\mathrm{B}$ breakup at 44 and 81 MeV/nucleon on heavy targets. The effects of higher-order processes due to both Coulomb and nuclear breakup mechanisms can be estimated. In line with earlier work we find that the asymmetries produced by the calculations are reduced when including the higher-order couplings, reflecting an effective quenching of the $E2\mathrm{}$ contributions. The full CDCC calculations show less asymmetry than the available experimental data, suggesting that the structure or reaction model now contains insufficient $E2\mathrm{}$ strength. This contrasts with the results of lowest-order reaction theories that conclude that the ${}^8\mathrm{B}$ model $E2\mathrm{}$ amplitudes are too large.

We present a detailed quark-model study of pion photoproduction within the effective Lagrangian approach. Cross sections and single-polarization observables are investigated for the four charge channels, $\gamma \overrightarrow{p}{\pi }^{+}n,$ $\gamma \overrightarrow{n}{\pi }^{-}p,$ $\gamma \overrightarrow{p}{\pi }^{0}p,$ and $\gamma \overrightarrow{n}{\pi }^{0}n.\mathrm{}$ Leaving the $\pi N\Delta$ coupling strength to be a free parameter, we obtain a reasonably consistent description of these four channels from threshold to the first resonance region. Within this effective Lagrangian approach, strongly constrained by the quark model, we consider the issue of double counting which may occur if additional t-channel contributions are included.

A relativistic constituent quark model is found to reproduce the recent data regarding the ratio of proton form factors, $F_2{(Q}^2{)/F}_1{(Q}^2).\mathrm{}$ We show that imposing Poincaré invariance leads to substantial violation of the helicity conservation rule, and an analytic result that the ratio $F_2{(Q}^2{)/F}_1{(Q}^2)\sim 1/Q$ for intermediate values of $Q^2.$

Excluded volume effects are incorporated in the quark-meson coupling model to take into account in a phenomenological way the hard-core repulsion of the nuclear force. The formalism employed is thermodynamically consistent and does not violate causality. The effects of the excluded volume on in-medium nucleon properties and the nuclear matter equation of state are investigated as a function of the size of the hard core. It is found that in-medium nucleon properties are not altered significantly by the excluded volume, even for large hard-core radii, and the equation of state becomes stiffer as the size of the hard core increases.

The methods allowing us to extract the coherent component of pion emission conditioned by the formation of a quasiclassical pion source in heavy ion collisions are suggested. They exploit a nontrivial modification of the quantum statistical and final state interaction effects on the correlation functions of like and unlike pions in the presence of the coherent radiation. The extraction of the coherent pion spectrum from ${\pi }^{+}{\pi }^{-}$ and ${\pi }^{\pm }{\pi }^{\pm }$ correlation functions and single-pion spectra is discussed in detail for large expanding systems produced in ultrarelativistic heavy ion collisions.

Strange particle ratios and $p_{\perp }$ spectra are calculated in a thermal model with single freeze-out, previously used successfully to describe nonstrange particle production at RHIC. The model and the recently released data for $\phi ,$ $\Lambda ,$ $\overline{\Lambda },$ and $K^{*}{\mathrm{}\left(892\right)\mathrm{}}^0$ are in very satisfactory agreement, showing that the thermal approach can be used to describe the strangeness production at RHIC.

The recently measured lower limit on the transition quadrupole moment $Q_t$ of a strongly deformed band in ${}^{108}\mathrm{Cd}$ is compatible with the value suggested by a simple analytic formula deduced from a binary cluster model. This model indicates that such large deformations should be widespread in the $A\sim 110$ region.

Very recent data for the reaction $\gamma \overrightarrow{d}\eta np,$ namely, total cross sections, angular and momentum spectra, are analyzed within a model that includes contributions from the impulse approximation and next-order corrections due to the $\mathrm{np}$ and $\eta N$ interactions in the final state. Comparison between the calculations and the new data indicate sizable contributions from the $\mathrm{np}$ and $\eta N$ final-state interactions. Some systematic discrepancies between the calculations and the data are also found.

Existing data for the $3_1^{+}$ state of ${}^{152}\mathrm{Sm}$ present serious uncertainties for any collective interpretation of this nucleus. In this work the lifetime of the $3_1^{+}$ state in ${}^{152}\mathrm{Sm}$ was remeasured, using the gamma ray induced Doppler technique in the $(n,\gamma )$ capture reaction, and the $E2/M1\mathrm{}$ mixing ratio of the $3_1^{+}\to 2_3^{+}$ transition was obtained from linear polarization measurements of $\gamma$ rays following the $\epsilon$ decay of ${}^{152}\mathrm{Eu}.$ The results remove the previous potential discrepancies and are in agreement with the interpretation of ${}^{152}\mathrm{Sm}$ as exhibiting phase coexistence near the critical point of a spherical-deformed phase transition.

We propose a new approach to the determination of hadronic observables in which the essential features of chiral symmetry are combined with conventional constituent quark models. To illustrate the approach, we consider the simple quark model in the limit of SU(3) flavor symmetry at the strange quark mass. The comparison with data is made after an analytic continuation which ensures the correct leading nonanalytic behavior of chiral perturbation theory. The approach not only gives an excellent fit for the octet baryon magnetic moments but the prediction for the ${\Delta }^{++}$ magnetic moment is also in good agreement with current measurements.

The production of intermediate-mass dileptons in ultrarelativistic nuclear collisions at SPS energies is studied. The acceptance and detector resolution inherent to measurements by the NA50 experimental collaboration are accurately modeled. The measured centrality dependence of the intermediate mass lepton pair excess is also addressed.

We study one-particle spectra and a two-particle correlation function in the 130 GeV/nucleon $\mathrm{Au}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider by making use of a hydrodynamical model. We calculate the one-particle hadronic spectra and present an analysis of Bose-Einstein correlation functions based on a numerical solution of the hydrodynamical equations which takes both longitudinal and transverse expansion into account appropriately. The hydrodynamical model provides excellent agreement with the experimental data in the pseudorapidity and the transverse momentum spectra of charged hadrons, the rapidity dependence of the antiproton-to-proton ratio, and almost consistent results for the pion Bose-Einstein correlation functions. Our numerical solution with a simple freeze-out picture suggests the formation of a quark-gluon plasma with large volume and low net-baryon density.

A Ward-Takahashi identity preserving Bethe-Salpeter kernel can always be calculated explicitly from a dressed-quark-gluon vertex whose diagrammatic content is enumerable. We illustrate that fact using a vertex obtained via the complete resummation of dressed-gluon ladders. While this vertex is planar, the vertex-consistent kernel is nonplanar and that is true for any dressed vertex. In an exemplifying model the rainbow-ladder truncation of the gap and Bethe-Salpeter equations yields many results; e.g., π- and ρ-meson masses, that are changed little by including higher-order corrections. Repulsion generated by nonplanar diagrams in the vertex-consistent Bethe-Salpeter kernel for quark-quark scattering is sufficient to guarantee that diquark bound states do not exist.

The PHOBOS experiment has measured the charged particle multiplicity at midrapidity in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathrm{NN}}}=200\mathrm{}\hspace{0.5em}\mathrm{GeV}$ as a function of the collision centrality. Results on ${\mathrm{dN}}_{\mathrm{ch}}/d\eta {|}_{|\eta |<1\mathrm{}}$ divided by the number of participating nucleon pairs $〈N_{\mathrm{part}}〉/2\mathrm{}$ are presented as a function of $〈N_{\mathrm{part}}〉.$ As was found from similar data at $\sqrt{s_{\mathrm{NN}}}=130\mathrm{}\hspace{0.5em}\mathrm{GeV},$ the data can be equally well described by parton saturation models and two-component fits, which include contributions that scale as $N_{\mathrm{part}}$ and the number of binary collisions $N_{\mathrm{coll}}.$ We compare the data at the two energies by means of the ratio $R_{200/130}$ of the charged particle multiplicity for the two different energies as a function of $〈N_{\mathrm{part}}〉.$ For events with $〈N_{\mathrm{part}}〉>100,$ we find that this ratio is consistent with a constant value of $1.14\pm 0.01\left(\mathrm{stat}\right)\pm 0.05\left(\mathrm{syst}\right).\mathrm{}$

We propose a new shell model method, combining the Lanczos diagonalization and extrapolation methods. This method can give accurate shell model energy from a series of shell model calculations with various truncation spaces, in a well-controlled manner. Its feasibility is demonstrated by taking $\mathrm{fp}$ shell calculations.

We develop and test efficient approximations to estimate ground state correlations associated with low- and zero-energy modes. The scheme is an extension of the generator coordinate method (GCM) within Gaussian overlap approximation (GOA). We show that the GOA fails in non-Cartesian topologies and presents a topologically correct generalization of the GOA (topGOA). A random-phase-approximation like (RPA-like) correction is derived as the small amplitude limit of topGOA, called topRPA. Using exactly solvable models, the topGOA and topRPA schemes are compared with conventional approaches (GCM-GOA, RPA, Lipkin-Nogami projection) for rotational-vibrational motion and for particle-number projection. The results shows that the new schemes perform very well in all regimes of coupling.

The $\mathrm{sp}\mathrm{}(3,R)\mathrm{}$ mean field approximation describes collective nuclear rotation in a symplectic density matrix formalism. The densities are $6\times 6$ matrices that are defined by the quantum mechanical expectations of the symplectic algebra generators. The 21 generators of the noncompact symplectic algebra $\mathrm{sp}\mathrm{}(3,R)\mathrm{}$ include the mass quadrupole and monopole moments, the kinetic energy, the harmonic oscillator Hamiltonian, and the angular, vibrational, and vortex momenta. The mean field approximation restricts the densities to a coadjoint orbit of the canonical transformation group $\mathrm{Sp}\mathrm{}(3,R).$ The reduction of a $\mathrm{Sp}\mathrm{}(3,R)\mathrm{}$ coadjoint orbit into orbits of the dynamical symmetry group GCM(3) is proved to be consistent with the reduction of an $\mathrm{Sp}\mathrm{}(3,R)\mathrm{}$ discrete series representation into irreducible representations of GCM(3). This reduction places a strict bound on the range of the Kelvin circulation which is the Casimir of the 15-dimensional subalgebra gcm(3)⊂sp(3,R). The cranked anisotropic oscillator and Riemann ellipsoid model are special cases of symplectic mean field theory. The application of the Riemann model in the even-even heavy deformed region indicates that the character of low energy collective rotational modes depends only on the quadrupole deformation β. The energy of the first $2^{+}$ state in such isotopes is a simple function of β.