title:
Multiple Electromagnetic Excitation in Fast Peripheral Heavy Ions
  Collisions

abstract:
  We study the corrections of first order electromagnetic excitation due to
higher order electromagnetic interactions. An effective operator is introduced
which takes these effects into account in the sudden approximation. Evaluating
the matrix-elements of this operator between the relevant states corrections to
the first order result are obtained in a simple way. As an example we discuss
the excitation of the first excited state in 11Be. It tends to improve the
agreement between experiment and theory.


title:
Variational Calculation of Relativistic Meson-Nucleon Scattering In
  Zeroth Order

abstract:
  We extend the polaron variational treatment previously developed for the
propagator to the case where one nucleon and $n$ external mesons are present.
Using the particle representation of the scalar Wick-Cutkosky model this is
done in lowest order of an expansion of the exact action around a retarded
quadratic trial action. In particular, we evaluate the form factor for
scattering of mesons from the scalar nucleon and determine the radius of the
dressed particle. After analytic continuation to Minkowski space we study
elastic meson-nucleon scattering both analytically and numerically near
threshold and show that it is essential to incorporate the correct behaviour of
the retardation function at large proper times. Only if this is done the
optical theorem is approximately fulfilled over a range of energies and
coupling constants.


title: Low--Energy Kaon--Nucleon Interactions and Scattering at DA$\Phi$NE

abstract:
  We present in this contribution the basic formul\ae\ for the analysis of
low--momentum charged-- and neutral--kaon interactions in hydrogen, including
as well a (brief) description of the problems left open by past experiments,
and of the improvements DA$\Phi$NE can be expected to offer over them.
Interactions in deuterium and other light nuclei will be only briefly
mentioned, and only in those respects touching directly upon the more
``elementary'' aspects of kaon--nucleon interactions.


title: Enhancement of low-mass dileptons in heavy-ion collisions

abstract:
  Using a relativistic transport model for the expansion stage of S+Au
collisions at 200 GeV/nucleon, we show that the recently observed enhancement
of low-mass dileptons by the CERES collaboration can be explained by the
decrease of vector meson masses in hot and dense hadronic matter.


title:
Mesonic Width Effects on the Momentum Dependence of the Rho-Omega Mixing
  Matrix Element

abstract:
  It is shown, in a model independent way, that the large difference in rho and
omega widths gives rise to a new source of momentum dependence for the
rho-omega mixing matrix element. The q^2 dependence arising due to the meson
widths leads to a significant alteration of the result obtained in the
zero-width approximation usually discussed in the literature. The origin of
this strong momentum dependence lies in the difference between the rho and
omega meson widths.


title: A Monte-Carlo Approach to Zero Energy Quantum Scattering

abstract:
  Monte-Carlo methods for zero energy quantum scattering are developed.
Starting from path integral representations for scattering observables, we
present results of numerical calculations for potential scattering and
scattering off a schematic $^4 \rm He $ nucleus. The convergence properties of
Monte-Carlo algorithms for scattering systems are analyzed using stochastic
differential equation as a path sampling method.


title: Kaon production cross sections from baryon-baryon interactions

abstract:
  In a one-pion plus one-kaon exchange model, we calculate the kaon production
cross sections in nucleon-nucleon, nucleon-delta and delta-delta interactions.
We find that this model describes reasonably well the experimental data on kaon
production in the proton-proton interaction. Near the kaon production
threshold, the cross section obtained from this model is smaller than that from
the linear parameterization of Randrup and Ko. For kaon production cross
sections from the nucleon-delta and delta-delta interactions, the cross
sections are singular in free space, so we calculate them in a nuclear medium
by including the (complex) pion self-energy. The results are compared with the
scaling ansatz of Randrup and Ko. The theoretical cross sections are then used
in a transport model to study kaon production from Au+Au collisions at 1
GeV/nucleon.


title: Role of correlated two-pion exchange in $K^+ N$ scattering

abstract:
  A dynamical model for S-- and P--wave correlated $2 \pi$ (and $K \bar K$)
exchange between a kaon and a nucleon is presented, starting from corresponding
$N \bar N \rightarrow K \bar K$ amplitudes in the pseudophysical region, which
have been constructed from nucleon, $\Delta$--isobar and hyperon ($\Lambda$,
$\Sigma$) exchange Born terms and a realistic meson exchange model of the $\pi
\pi \rightarrow K \bar K$ and $K \bar K \rightarrow K \bar K$ amplitude. The
contribution in the s--channel is then obtained by performing a dispersion
relation over the unitarity cut. In the $\rho$--channel, considerable
ambiguities exist, depending on how the dispersion integral is performed. Our
model, supplemented by short range interaction terms, is able to describe
empirical $K^+ N$ data below pion production threshold in a satisfactory way.


title:
Classcial Bifurcation and Enhancement of Quantum Shells --- Systematic
  Analysis of Reflection-Asymmetric Deformed Oscillator ---

abstract:
  Correspondence between classical periodic orbits and quantum shell structure
is investigated for a reflection-asymmetric deformed oscillator model as a
function of quadrupole and octupole deformation parameters. Periodic orbit
theory reveals several aspects of quantum level structure for this
non-integrable system. Good classical- quantum correspondence is obtained in
the Fourier transform of the quantum level density, and importance of periodic
orbit bifurcation is demonstrated. Systematic survey of the local minima of
shell energies in the two-dimensional deformation parameter space shows that
prominent shell structures do emerge at finite values of the octupole
parameter. Correspondences between the regions exhibiting strong shell effects
and the classical bifurcation lines are investigated, and significance of these
bifurcations is indicated.


title: Exchange Current Corrections to Neutrino--Nucleus Scattering

abstract:
  Relativistic exchange current corrections to neutrino--nucleus cross sections
are presented assuming non--vanishing strange quark form factors for the
constituent nucleons. For charged current processes the exchange current
corrections can lower the impulse approximation results by 10\% while these
corrections are found to be sensitive to both the nuclear density and the
strange quark axial form factor of the nucleon for neutral current processes.
Implications on the LSND experiment to determine this form factor are
discussed.


title: NUCLEAR SUPPRESSION OF HADROPRODUCTION

abstract:
  We demonstrate that the main part of the observed nuclear suppression of
dilepton and charmonium production, especially the x-dependence of the
suppression, can be explained by the absorption of fast initial partons. We
assume the absorption to be x1-dependent and determine the empirical form of
this dependence. Several reactions at different energies are described with the
same parametrization of the absorption cross section. The factorization theorem
constraints and some alternative models are discussed. The obtained description
of data allows to make conclusions about the origin of nuclear effects in
hadro- and electroproduction. In particular, it is concluded that the parton
recombination and the excess pion contribution are unimportant in nuclei and an
indication of excess gluons at $x_{2}\sim 0.1$ is observed.


title:
Proton inelastic scattering to continuum studied with antisymmetrized
  molecular dynamics

abstract:
  Intermediate energy (p,p$'$x) reaction is studied with antisymmetrized
molecular dynamics (AMD) in the cases of $^{58}$Ni target with $E_p = 120$ MeV
and $^{12}$C target with $E_p = $ 200 and 90 MeV. Angular distributions for
various $E_{p'}$ energies are shown to be reproduced well without any
adjustable parameter, which shows the reliability and usefulness of AMD in
describing light-ion reactions. Detailed analyses of the calculations are made
in the case of $^{58}$Ni target and following results are obtained: Two-step
contributions are found to be dominant in some large angle region and to be
indispensable for the reproduction of data. Furthermore the reproduction of
data in the large angle region $\theta \agt 120^\circ$ for $E_{p'}$ = 100 MeV
is shown to be due to three-step contributions. Angular distributions for
$E_{p'} \agt$ 40 MeV are found to be insensitive to the choice of different
in-medium nucleon-nucleon cross sections $\sigma_{NN}$ and the reason of this
insensitivity is discussed in detail. On the other hand, the total reaction
cross section and the cross section of evaporated protons are found to be
sensitive to $\sigma_{NN}$. In the course of the analyses of the calculations,
comparison is made with the distorted wave approach.


title:
Charge-Symmetry-Breaking Potentials from Isospin-Violating Meson-Baryon
  Coupling Constants

abstract:
  We consider charge-symmetry violations in the nucleon-nucleon force which
result from isospin-violating meson-baryon coupling constants. The vector
mesons are assumed to couple to the nucleon's electromagnetic current, which we
decompose into isoscalar and isovector quark components. We compute these
currents in the context of a constituent quark model. The isospin violations in
the meson-baryon couplings arise from the difference in the up and down
constituent quark masses. We show that class IV charge-symmetry-breaking
potentials arise in the resulting $\omega$ and $\rho$ exchange contributions to
the $NN$ force. The magnitude of these contributions is consistent with that
phenomenologically required by the measured difference of $n$ and $p$ analyzing
powers in elastic $\vec{n}-\vec{p}$ scattering at 183 MeV.


title: Comment on ``Large-space shell-model calculations for light nuclei''

abstract:
  In a recent publication Zheng, Vary, and Barrett reproduced the negative
quadrupole moment of Li-6 and the low-lying positive-parity states of He-5 by
using a no-core shell model. In this Comment we question the meaning of these
results by pointing out that the model used is inadequate for the reproduction
of these properties.


title:
Constraints on $\Sigma$ Nucleus Dynamics from Dirac Phenomenology of
  $\Sigma^-$ Atoms

abstract:
  Strong interaction level shifts and widths in $\Sigma^-$ atoms are analyzed
by using a $\Sigma$ nucleus optical potential constructed within the
relativistic mean field approach. The analysis leads to potentials with a
repulsive real part in the nuclear interior. The data are sufficient to
establish the size of the isovector meson--hyperon coupling. Implications to
$\Sigma$ hypernuclei are discussed.


title: The Role of Strangeness in Ultrarelativistic Nuclear Collisions

abstract:
  We review the progress in understanding the strange particle yields in
nuclear collisions and their role in signalling quark-gluon plasma formation.
We report on new insights into the formation mechanisms of strange particles
during ultrarelativistic heavy-ion collisions and discuss interesting new
details of the strangeness phase diagram. In the main part of the review we
show how the measured (multi-)strange particle abundances can be used as a
testing ground for chemical equilibration in nuclear collisions, and how the
results of such an analysis lead to important constraints on the collision
dynamics and space-time evolution of high energy heavy-ion reactions.


title: QCD Sum Rules, Scattering Length and the Vector Mesons in Nuclear Medium

abstract:
  Critical examination is made on the relation between the mass shift of vector
mesons in nuclear medium and the vector-meson $-$ nucleon scattering length. We
give detailed comparison between the QCD sum rule approach by two of the
present authors (Phys. Rev. {\bf C46} (1992) R34) and the scattering-length
approach by Koike (Phys. Rev. {\bf C51} (1995) 1488). It is shown that the
latter approach is mortally flawed both technically and conceptually.


title: A Coupled-Channels Study of $^{11}Be$ Coulomb Excitation

abstract:
  We study the effects of channel coupling in the excitation of $^{11}Be$
projectiles incident on heavy targets. The contribution to the excitation from
the Coulomb and the nuclear fields in peripheral collisions are considered. Our
results are compared with recent data on the excitation of the $\halfm$ state
in $^{11}Be$ projectiles. We show that the experimental results cannot be
explained, unless very unusual parameters are used.


title: Gamow-Teller strength in 54Fe and 56Fe

abstract:
  Through a sequence of large scale shell model calculations, total
Gamow-Teller strengths ($S_+$ and $S_-$) in $^{54}$Fe and $^{56}$Fe are
obtained. They reproduce the experimental values once the $\sigma\tau$ operator
is quenched by the standard factor of $0.77$. Comparisons are made with recent
Shell Model Monte Carlo calculations. Results are shown to depend critically on
the interaction. From an analysis of the GT+ and GT$-$ strength functions it is
concluded that experimental evidence is consistent with the $3(N-Z)$ sum rule.


title: Spherical Shell Model description of rotational motion

abstract:
  Exact diagonalizations with a realistic interaction show that configurations
with four neutrons in a major shell and four protons in another -or the same-
major shell, behave systematically as backbending rotors. The dominance of the
$q\cdot q$ component of the interaction is explained by an approximate form of
SU3 symmetry. It is suggested that these configurations are associated with the
onset of rotational motion in medium and heavy nuclei.


title: From Reversible Quantum Microdynamics to Irreversible Quantum Transport

abstract:
  The transition from reversible microdynamics to irreversible transport can be
studied very efficiently with the help of the so-called projection method. We
give a concise introduction to that method, illustrate its power by using it to
analyze the well-known rate and quantum Boltzmann equations, and present, as a
new application, the derivation of a source term accounting for the spontaneous
creation of electron-positron pairs in strong fields. Thereby we emphasize the
fundamental importance of time scales: only if the various time scales
exhibited by the dynamics are widely disparate, can the evolution of the slower
degrees of freedom be described by a conventional Markovian transport equation;
otherwise, one must account for finite memory effects. We show how the
projection method can be employed to determine these time scales, and how --if
necessary-- it allows one to include memory effects in a straightforward
manner. Finally, there is an appendix in which we discuss the concepts of
entropy and macroscopic irreversibility.


title: The realistic collective nuclear Hamiltonian

abstract:
  The residual part of the realistic forces ---obtained after extracting the
monopole terms responsible for bulk properties--- is strongly dominated by
pairing and quadrupole interactions, with important $\sigma\tau\cdot\sigma
\tau$, octupole and hexadecapole contributions. Their forms differ from the
schematic ones through normalizations that lead to a universal $A^{-1/3}$
scaling for all multipoles. Coupling strengths and effective charges are
calculated and shown to agree with the observed values.


title: Microscopic mass formulae

abstract:
  By assuming the existence of a pseudopotential smooth enough to do
Hartree-Fock variations and good enough to describe nuclear structure, we
construct mass formulae that rely on general scaling arguments and on a
schematic reading of shell model calculations. Fits to 1751 known binding
energies for N,Z$\geq 8$ lead to rms errors of 375 keV with 28 parameters.
Tests of the extrapolation properties are passed successfully. The
Bethe-Weizs\"acker formula is shown to be the asymptotic limit of the present
one(s). The surface energy of nuclear matter turns out to be probably smaller
than currently accepted.


title: Separation of the monopole contribution to the nuclear Hamiltonian

abstract:
  It is shown that the nuclear Hamiltonian can be separated rigorously as
${\cal H}={\cal H}_m+{\cal H}_M.$ For sufficiently smooth forces the monopole
part ${\cal H}_m $is entirely responsible for Hartree-Fock selfconsistency and
hence saturation properties. The multipole part ${\cal H}_M$ contains the
``residual'' terms - pairing, quadrupole, etc. - that will be analyzed in a
companion paper. We include a review of the basic results often needed when
working with multipole decompositions and average monopole properties.


title: Phase Transitions in Warm, Asymmetric Nuclear Matter

abstract:
  A relativistic mean-field model of nuclear matter with arbitrary proton
fraction is studied at finite temperature. An analysis is performed of the
liquid-gas phase transition in a system with two conserved charges (baryon
number and isospin) using the stability conditions on the free energy, the
conservation laws, and Gibbs' criteria for phase equilibrium. For a binary
system with two phases, the coexistence surface (binodal) is two-dimensional.
The Maxwell construction through the phase-separation region is discussed, and
it is shown that the stable configuration can be determined uniquely at every
density. Moreover, because of the greater dimensionality of the binodal
surface, the liquid-gas phase transition is continuous (second order by
Ehrenfest's definition), rather than discontinuous (first order), as in
familiar one-component systems. Using a mean-field equation of state calibrated
to the properties of nuclear matter and finite nuclei, various phase-separation
scenarios are considered. The model is then applied to the liquid-gas phase
transition that may occur in the warm, dilute matter produced in energetic
heavy-ion collisions. In asymmetric matter, instabilities that produce a
liquid-gas phase separation arise from fluctuations in the proton concentration
(chemical instability), rather than from fluctuations in the baryon density
(mechanical instability).


title:
The Phase Transition to the Quark-Gluon Plasma and Its Effect on
  Hydrodynamic Flow

abstract:
  It is shown that in ideal relativistic hydrodynamics a phase transition from
hadron to quark and gluon degrees of freedom in the nuclear matter equation of
state leads to a minimum in the excitation function of the transverse
collective flow.


title: Isospin non-equilibrium in heavy-ion collisions at intermediate energies

abstract:
  We study the equilibration of isospin degree of freedom in intermediate
energy heavy-ion collisions using an isospin-dependent BUU model. It is found
that there exists a transition from the isospin equilibration at low energies
to non-equilibration at high energies as the beam energy varies across the
Fermi energy in central, asymmetric heavy-ion collisions. At beam energies
around 55 MeV/nucleon, the composite system in thermal equilibrium but isospin
non-equilibrium breaks up into two primary hot residues with N/Z ratios closely
related to those of the target and projectile respectively. The decay of these
forward-backward moving residues results in the strong isospin asymmetry in
space and the dependence of the isotopic composition of fragments on the N/Z
ratios of the target and projectile. These features are in good agreement with
those found recently in experiments at NSCL/MSU and TAMU, implications of these
findings are discussed.


title:
Formation of superdense hadronic matter in high energy heavy-ion
  collisions

abstract:
  We present the detail of a newly developed relativistic transport model (ART
1.0) for high energy heavy-ion collisions. Using this model, we first study the
general collision dynamics between heavy ions at the AGS energies. We then show
that in central collisions there exists a large volume of sufficiently
long-lived superdense hadronic matter whose local baryon and energy densities
exceed the critical densities for the hadronic matter to quark-gluon plasma
transition. The size and lifetime of this matter are found to depend strongly
on the equation of state. We also investigate the degree and time scale of
thermalization as well as the radial flow during the expansion of the
superdense hadronic matter. The flow velocity profile and the temperature of
the hadronic matter at freeze-out are extracted. The transverse momentum and
rapidity distributions of protons, pions and kaons calculated with and without
the mean field are compared with each other and also with the preliminary data
from the E866/E802 collaboration to search for experimental observables that
are sensitive to the equation of state. It is found that these inclusive,
single particle observables depend weakly on the equation of state. The
difference between results obtained with and without the nuclear mean field is
only about 20\%. The baryon transverse collective flow in the reaction plane is
also analyzed. It is shown that both the flow parameter and the strength of the
``bounce-off'' effect are very sensitive to the equation of state. In
particular, a soft equation of state with a compressibility of 200 MeV results
in an increase of the flow parameter by a factor of 2.5 compared to the cascade
case without the mean field. This large effect makes it possible to distinguish
the predictions from different theoretical models and to detect the signatures


title: Chiral Lagrangian Approach to Exchange Vector Currents in Nuclei

abstract:
  Exchange vector currents are calculated up to one-loop order (corresponding
to next-to-next-to-leading order) in chiral perturbation theory. As an
illustration of the power of the approach, we apply the formalism to the
classic nuclear process $n+p\rightarrow d +\gamma$ at thermal energy. The
exchange current correction comes out to be $(4.5 \pm 0.3)$ \% in amplitude
giving a predicted cross section $\sigma= (334\pm 3)\ {\mbox mb}$ in excellent
agreement with the experimental value $(334.2\pm 0.5)\ {\mbox mb}$. Together
with the axial charge transitions computed previously, this result provides a
strong support for the power of chiral Lagrangians in nuclear physics. As a
by-product of our results, we suggest an open problem in the application of
chiral Lagrangian approach to nuclear processes that has to do with giving a
physical meaning to the short-range correlations that play an important role in
nuclei.


title:
On the impossibility of temperature extraction from heavy ion induced
  particle spectra

abstract:
  Spectra of various particle species have been calculated with the Quantum
Molecular Dynamics (QMD) model for very central collisions of Au+Au. They are
compatible with the idea of a fully stopped thermal source which exhibits a
transversal expansion besides the thermal distribution of an ideal gas.
However, the microscopic analyses of the local flow velocities and temperatures
indicate much lower temperatures at densities associated with the freeze-out.
The results express the overall impossibility of a model-independent
determination of nuclear temperatures from heavy ion spectral data, also at
other energies e.g. CERN or for other species (i.e. pions, kaons, hyperons)!


title: Initial State Interactions for $K^-$-Proton Radiative Capture

abstract:
  The effects of the initial state interactions on the $K^--p$ radiative
capture branching ratios are examined and found to be quite sizable. A general
coupled-channel formalism for both strong and electromagnetic channels using a
particle basis is presented, and applied to all the low energy $K^--p$ data
with the exception of the {\it 1s} atomic level shift. Satisfactory fits are
obtained using vertex coupling constants for the electromagnetic channels that
are close to their expected SU(3) values.


title:
Nuclear Shell Model Calculations with Fundamental Nucleon-Nucleon
  Interactions

abstract:
  Some fundamental Nucleon-Nucleon interactions and their applications to
finite nuclei are reviewed. Results for the few-body systems and from
Shell-Model calculations are discussed and compared to point out the advantages
and disadvantages of the different Nucleon-Nucleon interactions. The recently
developed Drexel University Shell Model (DUSM) code is mentioned.


title:
Nucleon-Antinucleon Annihilation in Large Nc QCD with rho and omega
  Mesons

abstract:
  We use classical/large Nc (number of colors) QCD to study
nucleon--antinucleon annihilation at rest. We include pion, rho and omega
fields in the classical dynamics, starting from the nonlinear sigma model. We
begin with a spherical blob of pionic matter with zero baryon number and energy
of twice the nucleon mass. This evolves according to the classical dynamics to
pion and vector meson fields into the radiation zone. The radiation fields are
quantized using the method of coherent states modified to include isospin and
four momentum conservation. Empirical information is extracted from that
coherent state. We find good agreement with data for single particle momentum
and number spectra, and with branching ratios to many annihilation channels.
All this emerges with nearly no free parameters.


title: A METHOD OF CALCULATING THE JOST FUNCTION FOR ANALYTIC POTENTIALS

abstract:
  A combination of the variable-constant and complex coordinate rotation
methods is used to solve the two-body Schr\"odinger equation. The latter is
replaced by a system of linear first-order differential equations, which
enables one to perform direct calculation of the Jost function for all complex
momenta of physical interest, including the spectral points corresponding to
bound and resonance states. Explicit forms of the equations, appropriate for
central, noncentral, and Coulomb-tailed potentials are given. Within the
proposed method, the scattering, bound, virtual, and resonance state problems
can be treated in a unified way. The effectiveness of the method is
demonstrated by a numerical example.


title:
The longitudinal asymmetry of the $(e,e'p)$ missing momentum
  distribution as a signal of color transparency

abstract:
  We use multiple scattering theory to evaluate the $Q^{2}$ dependence
  of the forward-backward asymmetry, $A_{z}$, of the missing momentum
distribution in quasielstic $A(e,e'p)$ scattering, which is expected to be
affected by color transparency. The novel features of our analysis are a
consistent treatment of the structure of the ejectile state formed after
absorption of the virtual photon by the struck proton and a careful evaluation
of the background asymmetry induced by the nonvanishing real part of the
proton-nucleon scattering amplitude. We find that the absolute magnitude of
$A_{z}$ is dominated by this background at the $Q^{2}$'s attainable at the
Continuous Electron Beam Accelerator Facility. However, the $Q^{2}$ dependence
of the asymmetry is sensitive to the onset of color transparency, whose
observation in high statistics experiments appears to be feasible, particularly
using light targets such as $^{12}C$ or $^{16}O$.


title: Pre-Equilibrium Particle Emission and Critical Exponent Analysis

abstract:
  In two different phase transition models of nuclear fragmentation we show
that the emission of pre-equilibrium particles and mixing of events from
different classes cannot be ignored in the analysis of nuclear fragmentation
data in terms of critical exponents, and we show how the apparent values of the
extracted exponents are affected.


title:
Isospin Lattice Gas Model and Nuclear-Matter Phase Diagram and
  Pressure-Volume Isotherms

abstract:
  We study a cubic lattice gas model for nuclear matter where each lattice site
can be either occupied, by one proton or one neutron, or unoccupied. A
nearest-neighbor interaction of the form $ - \sum_{<ij>} J_{ij}\tau_{zi}
\tau_{zj}$ is assumed. Our model is an isospin-1 Ising model, with ${\tau_z}$ =
(1,0,-1) representing respectively (proton, vacancy, neutron).
  A kinetic-energy term has been included in our model. Under the
Bragg-Williams mean field approximation our model exhibits the existence of a
dense phase (liquid-like) and a rare phase (gas-like). The nuclear-matter p-v
isotherms given by our model are discussed.


title:
Effective Lagrangians and Parity-Conserving Time-Reversal Violation at
  Low Energies

abstract:
  Using effective Lagrangians, we argue that any time-reversal-violating but
parity-conserving effects are too small to be observed in flavor-conserving
nuclear processes without dramatic improvement in experimental accuracy. In the
process we discuss other arguments that have appeared in the literature.


title:
Delta degrees of freedom in antisymmetrized molecular dynamics and
  (p,p') reactions in the delta region

abstract:
  Delta degrees of freedom are introduced into antisymmetrized molecular
dynamics (AMD). This is done by increasing the number of basic states in the
AMD wave function, introducing a Skyrme-type delta-nucleon potential, and
including $NN\leftrightarrow N\Delta$ reactions in the collision description.
As a test of the delta dynamics, the extended AMD is applied to (p,p$'$)
recations at $E_{\rm lab}=800$ MeV for a $^{12}$C target. It is found that the
ratio and the absolute values for delta peak and quasielastic peak (QEP) in the
$^{12}$C(p,p$'$) reaction are reproduced for angles $\Theta_{\rm lab} \agt
40^\circ$, pointing to a correct treatment of the delta dynamics in the
extended AMD. For forward angles the QEP is overestimated. The results of the
AMD calculations are compared to one-step Monte Carlo (OSMC) calculations and a
detailed analysis of multi-step and delta potential effects is given. As
important side results we present a way to apply a Gallilei invariant theory
for (N,N$'$) reactions up to $E_{\rm lab} \approx 800$ MeV which ensures
approximate Lorentz invariance and we discuss how to fix the width parameter
$\nu$ of the single particle momentum distribution for outgoing nucleons in the
AMD calculation.


title: Representations for Three-Body T-Matrix on Unphysical Sheets

abstract:
  Explicit representations are formulated for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. According to the representations, the T-matrix on unphysical
sheets is obviously expressed in terms of its components taken on the physical
sheet only. The representations for T-matrix are used then to construct similar
representations for analytical continuation of three-body scattering matrices
and resolvent. Domains on unphysical sheets are described where the
representations obtained can be applied.


title: Representations for Three-Body T-Matrix on Unphysical Sheets: Proofs

abstract:
  A proof is given for the explicit representations which have been formulated
in the author's previous work (nucl-th/9505028) for the Faddeev components of
three-body T-matrix continued analytically on unphysical sheets of the energy
Riemann surface. Also, the analogous representations for analytical
continuation of the three-body scattering matrices and resolvent are proved. An
algorithm to search for the three-body resonances on the base of the Faddeev
differential equations is discussed.


title:
Removal of the Energy Dependence from the Resolvent-like
  Energy-Dependent Interactions

abstract:
  The spectral problem $(A + V(z))\psi=z\psi$ is considered with $A$, a
self-adjoint Hamiltonian of sufficiently arbitrary nature. The perturbation
$V(z)$ is assumed to depend on the energy $z$ as resolvent of another
self-adjoint operator $A':$ $V(z)=-B(A'-z)^{-1}B^{*}$. It is supposed that
operator $B$ has a finite Hilbert-Schmidt norm and spectra of operators $A$ and
$A'$ are separated. The conditions are formulated when the perturbation $V(z)$
may be replaced with an energy-independent ``potential'' $W$ such that the
Hamiltonian $H=A +W$ has the same spectrum (more exactly a part of spectrum)
and the same eigenfunctions as the initial spectral problem. The orthogonality
and expansion theorems are proved for eigenfunction systems of the Hamiltonian
$ H=A + W $. Scattering theory is developed for $H$ in the case when operator
$A$ has continuous spectrum. Applications of the results obtained to few-body
problems are discussed.


title: Nuclear incompressibility: An analytical study on leptodermous expansion

abstract:
  A comparative study of the liquid-drop model (LDM) type expansions of energy
$E$ and compression modulus $K_A$ is made within the energy density formalism
using Skyrme interactions. As compared to the energy expansion, it is found
that, in the pure bulk mode of density vibration, the LDM expansion of $K_A$
shows an anomalous convergence behaviour due to {\it pair \ effect}. A least
squares fit analysis is done to estimate the minimum error, one would expect
even with synthetic data due to the inherent nature of the LDM expansion of
$K_A$ as well as the narrow range of accessible mass number $A$, in the values
of the various coefficients. The dependence of the higher-order coefficients
like curvature and Gauss curvature on the coupling $\beta_c$ between the bulk
and surface parts of the monopole vibrations is analytically studied. It is
shown that the $K_A -$ expansion including the dynamical effect ( $A-$
dependence of $\beta_c$ ) shows an `up-turn' behaviour below mass number about
120, suggesting the inapplicability of the LDM expansion of $K_A$ over this
mass region.


title:
Extracting Source Parameters from Gaussian Fits to Two-Particle
  Correlations

abstract:
  Using a quadratic saddle-point approximation, we show how information about a
particle-emitting source can be extracted from gaussian fits to two-particle
correlation data. Although the formalism is completely general, extraction of
the relevant parameters is much simpler for sources within an interesting class
of azimuthally symmetric models. After discussing the standard fitting
procedure, we introduce a new gaussian fitting procedure which is an
azimuthally symmetric generalization of the Yano-Koonin formalism for
spherically symmetric sources. This new fitting procedure has the advantage
that in addition to being able to measure source parameters in a fixed frame or
the longitudinally co-moving system, it can also measure these parameters in
the local rest frame of the source.


title:
New Scaling Law for Deuteron Production in Ultra-Relativistic Nucleus
  Nucleus Collisions

abstract:
  Deuteron production in S and Pb induced collisions at beam energies of 200
and 160 AGeV is studied in the framework of the transport theoretical approach
RQMD. Strong transverse flow invalidates the differential coalescence formula
in momentum space. The transverse momentum integrated $d$ yields scale in a
broad rapidity interval with the squared proton densities and inversely with
the produced particle rapidity densities. This kind of scaling can be linked to
constant relative sizes of nucleon and pion sources at freeze-out. With
increasing projectile mass the nucleon source blows up stronger than the pion
source. As a result, the scaled deuteron densities drop in central Pb+Pb
collisions by 15 percent as compared to S induced reactions.


title: On the balance of the solar p-p chain

abstract:
  I show that the solar neutrino fluxes, predicted by standard nuclear and
solar physics, can get closer to the experimental observations if one takes the
freedom to introduce two free parameters into the model, as it is done in the
MSW solution. I point out that the plasma electron capture of Be7 and the
He3(He3,2p)He4 nuclear reactions deserve further experimental and theoretical
attention.


title:
Electron-positron pairs from thermal resonances in ultrarelativistic
  nuclear collisions

abstract:
  We use a boost-invariant one-dimensional (cylindrically symmetric) fluid
dynamics code to calculate $e^+e^-$ production from $\rho^0$ and $\omega$ decay
in the central rapidity region of a central S+Au collision at $\sqrt{s}=20$
GeV/nucleon. We use equations of state with a first-order phase transition
between a massless pion gas and quark gluon plasma, with transition
temperatures in the range $150-200$ MeV. The production cross section at the
$\rho$ mass loosely constrains the transition and freeze-out temperatures, and
we find that the $m_T$ spectrum is a good thermometer for sufficiently high
$T_c$.


title: Chaoticity in Vibrating Nuclear Billiards

abstract:
  We study the motion of classical particles confined in a two-dimensional
"nuclear" billiard whose walls undergo periodic shape oscillations according to
a fixed multipolarity. The presence of a coupling term in the single particle
Hamiltonian between the particle motion and the collective coordinate generates
a fully selfconsistent dynamics. We consider in particular monopole
oscillations and demonstrate that self-consistency is essential in order to
induce chaotic single-particle motion. We also discuss the dissipative
behaviour of the wall motion and its relation with the order-to-chaos
transition in the dynamics of the microscopic degrees of freedom. Analogous
considerations can be extended to higher multipolarities.


title: Neutron Stars and Massive Quark Matter

abstract:
  Using the Color-Dielectric model to describe quark confinement, including
strange quarks and accounting for beta--equilibrium, we get masses for a static
neutron star in the range $1.3\leq M/M_{\odot}\leq 1.54 $ for a radius
$R\approx 9$ km. Rapid cooling through the direct URCA mechanism is obtained.
The implications for the composition of neutron stars is discussed.


title: Momentum Distribution in Nuclear Matter and Finite Nuclei

abstract:
  A simple method is presented to evaluate the effects of short-range
correlations on the momentum distribution of nucleons in nuclear matter within
the framework of the Green's function approach. The method provides a very
efficient representation of the single-particle Green's function for a
correlated system. The reliability of this method is established by comparing
its results to those obtained in more elaborate calculations. The sensitivity
of the momentum distribution on the nucleon-nucleon interaction and the nuclear
density is studied. The momentum distributions of nucleons in finite nuclei are
derived from those in nuclear matter using a local-density approximation. These
results are compared to those obtained directly for light nuclei like $^{16}O$.


title: Resonant nuclear transition in the d-mu-Li6 muonic molecule

abstract:
  The reaction rate of the nuclear fusion d+Li6 ----> Be8*(2+,0) is estimated
in the case where the nuclei are confined to each other by a muon. For the
description of nuclear transitions, a method which is analogous to the Linear
Combination of Atomic Orbitals has been used. Using the complex coordinate
rotation method, we found that a molecular d-mu-Li6 state exists with energy
(-20.3084-i0.0066) eV and |\Psi_{m}(0)|=0.44x10^{-7} fm^-3/2. The nuclear wave
functions needed, were constructed in the form of antisymmetrized products of
harmonic-oscillator functions for the three-cluster approximation, (dd\alpha),
to the five-body (NNNN\alpha) problem. It was found that the reaction rate
\lambda is strongly dependent on the energy gap between the d-Li6 threshold and
the energy of the final Be8^* resonant state. The value of \lambda obtained by
averaging over the width of this resonance, is 0.183x10^10 sec^{-1}.


title:
Updated analysis of $\pi$N elastic scattering data to 2.1~GeV: The
  Baryon Spectrum

abstract:
  We present the results of energy-dependent and single-energy partial-wave
analyses of $\pi$N elastic scattering data with laboratory kinetic energies
below 2.1~GeV. Resonance structures have been extracted using Breit-Wigner
fits, speed plots, and a complex plane mapping of the associated poles and
zeroes. This is the first set of resonance parameters from a VPI analysis
constrained by fixed-t dispersion relations. We have searched our solutions for
structures which may have been missed in our previous analyses, finding
candidates in the $S_{11}$ and $F_{15}$ partial-wave amplitudes. Our results
are compared with those found by the Karlsruhe, Carnegie-Mellon$-$Berkeley, and
Kent State groups.


title: Temperature dependent Nucleon Mass and entropy bound inequality

abstract:
  Mass of a baryon as a function of temperature is calculated using
colour-singlet partition function for massless quarks (with two flavours) and
abelian gluons confined in a bag with a temperature dependent bag pressure
constant $B(T)$. The non-perturbative aspect of QCD interaction is included
through colour-singlet restriction on quark-gluon partition function in a
phenomenological way. The entropy bound inequality $ S/E \ \leq \ 2\pi R/\hbar
c $, where $S, \ E $ and $R$ are entropy, energy and radius, respectively of
the enclosed system with $\hbar c \ = \ 197.331 $ MeVfm, is found to be
consistent with the equilibrium solutions of the baryon mass upto a temperature
$T_E$. There is a region of temperature $T_E < T < T_C$ ($T_C$ is critical
temperature for quark-gluon plasma formation) in which no admissible
equilibrium states exist for the bag. We say that the system expriences a phase
jump from hadron to quark-gluon plasma through thermodynamic non-equlibrium
processes.


title:
Approximate particle number projection for finite range density
  dependent forces

abstract:
  The Lipkin-Nogami method is generalized to deal with finite range density
dependent forces. New expressions are derived and realistic calculations with
the Gogny force are performed for the nuclei $^{164}$Er and $^{168}$Er. The
sharp phase transition predicted by the mean field approximation is washed out
by the Lipkin-Nogami approach; a much better agreement with the experimental
data is reached with the new approach than with the Hartree-Fock_Bogoliubov
one, specially at high spins.


title: Chiral Dynamics and the Low Energy Kaon-Nucleon Interaction

abstract:
  We examine the meson-baryon interaction in the strangeness S=-1 sector using
an effective chiral Lagrangian. Potentials are derived from this Lagrangian and
used in a coupled-channel calculation of the low energy observables. The
potentials are constructed such that in the Born approximation the s-wave
scattering amplitude is the same as that given by the effective chiral
Lagrangian, up to order $q^2$. Comparison is made with the available low energy
hadronic data of the coupled $K^-p, \Sigma \pi, \Lambda \pi$ system, which
includes the $\Lambda (1405)$ resonance, $K^-p$ elastic and inelastic
scattering, and the threshold branching ratios of the $K^-p$ decay. Good fits
to the experimental data and estimates of previously unknown Lagrangian
parameters are obtained.


title: Strangelets at finite temperature

abstract:
  Within the MIT bag model picture of QCD, we have studied the stability of
finite size strangelets at finite temperature with baryon number $A \leq 100$.
The light quarks $u$ and $d$ are considered massless while mass of the $s$
quark is taken as $150$ MeV. Using discrete eigen energies of the
non-interacting quarks in the bag, grand canonical partition function is
constructed and then the free energy is minimized with respect to the bag
radius. In the $T\rightarrow 0$ limit clear shell structures are found which
persist upto about $T=10$ MeV. Infact for $A=6$ the shell structure disappears
only at $T > 20$ MeV.


title: A Consistent Meson-Field-Theoretical Description of PP-Bremsstrahlung

abstract:
  A parameter-free and relativistic extension of the RuhrPot meson-baryon model
is used to define the dominant isoscalar meson-exchange currents. We compute
pp-bremsstrahlung observables below the $\pi-$production threshold using a
relativistic hadronic current density that includes impulse, wave function
re-orthonormalization, meson-recoil, $\bar{{\rm N}}$N creation and
annihilation, $\rho\pi\gamma$ + $\omega\pi\gamma$ + $\rho\eta\gamma$ +
$\omega\eta\gamma$ vector-meson decay and N$\Delta\gamma(\pi,\rho)$ exchange
currents. We obtain a good description of the available data. The
N$\Delta\gamma(\pi)$ current is shown to dominate the large two-body
contributions and closed-form expressions for various non-relativistic
approximations are analyzed. An experimental sensitivity to the admixture of
pseudo-scalar and pseudo-vector admixture of the NN$\pi$ interaction is
demonstrated. We examine the Lorentz invariance of the NN$\rightleftharpoons$NN
$t$-matrices and show a dominantly pseudo-vector NN$\pi$ coupling renders
impulse approximation calculations without boost operators to be essentially
exact. Conversely, a similar analysis of the $\Delta{\rm
N}\rightleftharpoons$NN transitions shows that boost operators and the two-body
$N\Delta\gamma$ wave function re-orthonormalization meson-recoil currents are
required in NN, $\Delta$N and $\Delta\Delta$ coupled channel $t$-matrix
applications. The need for additional data is stressed.


title: High-spin states in boson models with applications to actinide nuclei

abstract:
  We use the 1/$N$ expansion formalism in a systematic study of high-spin
states in the $sd$ and $sdg$ boson models with emphasis on spin dependence of
moment of inertia and E2 transitions. The results are applied to the high-spin
states in the actinide nuclei $^{232}$Th, $^{234-238}$U, where the need for $g$
bosons is especially acute but until now, no realistic calculation existed. We
find that the $d$-boson energy plays a crucial role in description of the
high-spin data.


title: Composite nucleons in scalar and vector mean-fields

abstract:
  We emphasize that the composite structure of the nucleon may play quite an
important role in nuclear physics. It is shown that the momentum-dependent
repulsive force of second order in the scalar field, which plays an important
role in Dirac phenomenology, can be found in the quark-meson coupling (QMC)
model, and that the properties of nuclear matter are well described through the
quark-scalar density in a nucleon and a self-consistency condition for the
scalar field. The difference between theories of point-like nucleons and
composite ones may be seen in the change of the $\omega$-meson mass in nuclear
matter if the composite nature of the nucleon suppresses contributions from
nucleon-antinucleon pair creation.


title:
Coulomb displacement energy and the low-energy astrophysical S factor
  for the Be7(p,gamma)B8 reaction

abstract:
  The relationship between the Coulomb displacement energy for the A=8, J=2+,
T=1 state and the low-energy astrophysical S factor for the Be7(p,gamma)B8
reaction is discussed. The displacement energy is interpreted in a
particle-hole model. The dependence of the particle displacement energy on the
potential well geometry is investigated and is used to relate the particle
displacement energy to the rms radius and the asymptotic normalization of the
valence proton wave function in B8. The asymptotic normalization is used to
calculate the astrophysical S factor for the Be7(p,gamma)B8 reaction. The
relationship to the Li7(n,gamma) reaction, the B8 quadrupole moment, radial
density, and break-up momentum distribution are also discussed.


title: Extraction of the $\pi NN$ coupling constant from NN scattering data

abstract:
  We reexamine Chew's method for extracting the $\pi NN$ coupling constant from
np differential cross section measurements. Values for this coupling are
extracted below 350 MeV, in the potential model region, and up to 1 GeV. The
analyses to 1~GeV have utilized 55 data sets. We compare these results to those
obtained via $\chi^2$ mapping techniques. We find that these two methods give
consistent results which are in agreement with previous Nijmegen
determinations.


title:
Quantum-Statistical Correlations and Single Particle Distributions for
  Slowly Expanding Systems with Temperature Profile

abstract:
  Competition among particle evaporation, temperature gradient and flow is
investigated in a phenomenological manner, based on a simultaneous analysis of
quantum statistical correlations and momentum distributions for a
non-relativistic, spherically symmetric, three-dimensionally expanding, finite
source. The parameters of the model emission function are constrained by fits
to neutron and proton momentum distributions and correlation functions in
intermediate energy heavy-ion collisions. The temperature gradient is related
to the momentum dependence of the radius parameters of the two-particle
correlation function, as well as to the momentum-dependent temperature
parameter of the single particle spectrum, while a long duration of particle
evaporation is found to be responsible for the low relative momentum behavior
of the two-particle correlations.


title:
A Multi-Configuration Mixing Approach with Symmetry-Projected Complex
  Hartree-Fock-Bogoliubov Determinants

abstract:
  A multi-configuration mixing approach built on essentially complex,
symmetry-projected Hartree-Fock-Bogoliubov (HFB) mean fields is introduced. The
mean fields are obtained by variation after projection. The configuration space
consists out of the symmetry-projected HFB vacuum and the symmetry-projected
two-quasiparticle excitations for even, and the symmetry-projected
one-quasiparticle excitations for odd A systems. The underlying complex HFB
transformations are assumed to be time-reversal invariant and axially
symmetric. The model allows nuclear structure calculations in large model
spaces with arbitrary two-body interactions. The approach has been applied to
$^{20}$Ne and $^{22}$Ne. Good agreement with the exact shell model results and
considerable improvement with respect to older calculations, in which only real
HFB transformations were admitted, is obtained.


title: Antibaryons in massive heavy ion reactions: Importance of potentials

abstract:
  In the framework of RQMD we investigate antiproton observables in massive
heavy ion collisions at AGS energies and compare to preliminary results of the
E878 collaboration. We focus here on the considerable influence of the *real*
part of an antinucleon--nucleus optical potential on the antiproton momentum
spectra.


title: Phasespace Correlations of Antideuterons in Heavy Ion Collisions

abstract:
  In the framework of the relativistic quantum molecular dynamics approach
({\small RQMD}) we investigate antideuteron ($\overline{d}$) observables in
Au+Au collisions at 10.7~AGeV. The impact parameter dependence of the formation
ratios $\overline{d}/\overline{p}^2$ and ${d}/{p}^2$ is calculated. In central
collisions, the antideuteron formation ratio is predicted to be two orders of
magnitude lower than the deuteron formation ratio. The $\overline{d}$ yield in
central Au+Au collisions is one order of magnitude lower than in Si+Al
collisions. In semicentral collisions different configuration space
distributions of $\overline{p}$'s and $\overline{d}$'s lead to a large
``squeeze--out'' effect for antideuterons, which is not predicted for the
$\overline{p}$'s.


title:
Hadronic cross-section fluctuations and proton coherent diffractive
  dissociation on helium

abstract:
  The differential cross-section of inelastic coherent diffractive dissociation
off nuclei $p~+~^4$He $\rightarrow X ~+ ~^4$He is expressed in terms of the
relative cumulants of the cross-section distribution $P_N(\sigma)$. The
theoretical result for the ratio
$r=\Bigg(\frac{d\sigma_{diff}}{dt}\Bigg)^{pHe}_{t=0} \Bigg/
\Bigg(\frac{d\sigma_{diff}}{dt}\Bigg)^{pp}_{t=0}=6.8 \div 7.6$ is close to the
value $r=7.1 \pm 0.75$ which we extracted from the FNAL data. These are the
only $A>2$ data of this kind. The comparison provides the first confirmation of
the cross-section fluctuation approach to the description of the absolute value
of the inelastic diffraction cross-section off nuclei. It provides also a new
constraint on the first 4 cumulants of the cross-section distribution.


title: Hyperon-rich Matter in Neutron Stars

abstract:
  We study the equation of state of hyperon-rich matter for neutron stars using
an extended relativistic mean-field model. We take special care of the recently
proposed non-linear behaviour of the vector field which gives a much better
description of Dirac-Brueckner calculations. The hyperon-hyperon interaction is
also implemented by introducing additional meson exchanges. These new terms
avoid the instability found at high densitites in previous works while keeping
the excellent description for finite nuclear systems. We also demonstrate
within the mean-field approach that the presence of hyperons inside neutron
stars on one hand and the hyperon-hyperon interactions on the other hand make
the onset of kaon condensation less favourable.


title: The Path of Hot Nuclei Towards Multifragmemtation

abstract:
  The initial production and dynamical expansion of hot spherical nuclei are
examined as the first stage in the projectile-multifragmentation process. The
initial temperatures, which are necessary for entering the adiabatic spinodal
region, as well as the minimum temperatures and densities, which are reached in
the expansion, significantly differ for hard and soft equations of state.
Additional initial compression, occurring in central collisions leads most
likely to a qualitatively different multifragmentation mechanism. Recent
experimental data are discussed in relation to the results of the proposed
model.


title: Intrinsic vs. laboratory frame description of the deformed nucleus 48Cr

abstract:
  The collective yrast band of the nucleus $^{48}$Cr is studied using the
spherical shell model and the HFB method. Both approaches produce basically the
same axially symmetric intrinsic state up to the - accurately reproduced -
observed backbending. Agreement between both calculations extends to most
observables. The only significant discrepancy comes from the static moments of
inertia and can be attributed to the need of a more refined treatment of
pairing correlations in the HFB calculation.


title: Short-range Correlations in a CBF description of closed-shell nuclei

abstract:
  The Correlated Basis Function theory (CBF) provides a theoretical framework
to treat on the same ground mean-field and short-range correlations. We
present, in this report, some recent results obtained using the CBF to describe
the ground state properties of finite nuclear systems. Furthermore we show some
results for the excited state obtained with a simplified model based on the CBF
theory.


title:
Heated nuclear matter, condensation phenomena and the hadronic equation
  of state

abstract:
  The thermodynamic properties of heated nuclear matter are explored using an
exactly solvable canonical ensemble model. This model reduces to the results of
an ideal Fermi gas at low temperatures. At higher temperatures, the
fragmentation of the nuclear matter into clusters of nucleons leads to features
that resemble a Bose gas. Some parallels of this model with the phenomena of
Bose condensation and with percolation phenomena are discussed. A simple
expression for the hadronic equation of state is obtained from the model.


title: Strangeness in Hadronic Stellar Matter

abstract:
  We examine the presence of strangeness-bearing components, hyperons and
kaons, in dense neutron star matter. Calculations are performed using
relativistic mean field models, in which both the baryon-baryon and kaon-baryon
interactions are mediated by meson exchange. Results of kaon condensation are
found to be qualitatively similar to previous work with chiral models, if
compatibility of the kaon optical potentials is required. The presence of
strangeness, be it in the form of hyperons or kaons, implies a reduction in the
maximum mass and a relatively large number of protons, sufficient to allow
rapid cooling to take place. The need to improve upon the poorly-known
couplings of the strange particles, which determine the composition and
structure of neutron stars, is stressed. We also discuss generic problems with
effective masses in mean field theories.


title:
Neutral Pion Photoproduction on Nuclei in Baryon Chiral Perturbation
  Theory

abstract:
  Threshold neutral pion photoproduction on light nuclei is studied in the
framework of baryon chiral perturbation theory. We obtain a general formula for
the electric dipole amplitude in the special case of neutral pion
photoproduction on a nucleus. To third order in small momenta, the amplitude is
a sum of 2- and 3-body interactions with no undetermined parameters. With
reasonable input from the single nucleon sector, our result for neutral pion
photoproduction on the deuteron is in agreement with experiment.


title: Tensor Coupling and Vector Mesons in Dense Nuclear Matter

abstract:
  The effects of magnetic interaction between vector mesons and nucleons on the
propagation (mass and width) of the $\rho$-meson in particular moving through
very dense nuclear matter is studied and the modifications, qualitative and
quantitative, due to the relevant collective modes (zero-sound and plasma
frequencies) of the medium discussed. It is shown that the $\rho$-mesons
produced in high-energy nuclear collisions will be longitudinally polarized in
the region of sufficiently dense nuclear matter, in the presence of such an
interaction.


title:
The Isovector Quadrupole-Quadrupole Interaction Used in Shell Model
  Calculations

abstract:
  An interaction $-\chi Q\cdot Q(1+B\vec{\tau}(1)\cdot \vec{\tau}(2))$ is used
in a shell model calculation for $^{10}Be$. Whereas for $B=0$ the $2_1^+$ state
is two-fold degenerate, introducing a negative $B$ causes an `isovector' $2^+$
state to come down to zero energy at $B=-0.67$ and an $S=1~L=1$ triplet
($J=0^+,~1^+,~2^+$) to come down to zero energy at $B=-0.73$. These are
undesirable properties, but a large negative $B$ is apparently needed to fit
the energy of the isovector giant quadrupole resonance.


title: Projectile $\Delta$ Excitations in $p(p,n)N\pi $ Reactions

abstract:
  It has recently been proven from measurements of the spin-transfer
coefficients $D_{xx}$ and $D_{zz}$ that there is a small but non-vanishing
$\Delta S=0$ component $\sigma_{0}$, in the inclusive $p(p,n)N\pi\,$ reaction
cross section $\sigma\,$. It is shown that the dominant part of the measured
$\sigma_{0}$ can be explained in terms of the projectile $\Delta$ excitation
mechanism. An estimate is further made of contributions to $\sigma_{0}$ from
s-wave rescattering process. It is found that s-wave rescattering contribution
is much smaller than the contribution coming from projectile $\Delta$
excitation mechanism. The addition of s-wave rescattering contribution to the
dominant part, however, improves the fit to the data.


title: Colour-singlet strangelets at finite temperature

abstract:
  Considering massless $u$ and $d$ quarks, and massive (150 MeV) $s$ quarks in
a bag with the bag pressure constant $B^{1/4} = 145$ MeV, a colour-singlet
grand canonical partition function is constructed for temperatures $T = 1-30$
MeV. Then the stability of finite size strangelets is studied minimizing the
free energy as a function of the radius of the bag. The colour-singlet
restriction has several profound effects when compared to colour unprojected
case: (1) Now bulk energy per baryon is increased by about $250$ MeV making the
strange quark matter unbound. (2) The shell structures are more pronounced
(deeper). (3) Positions of the shell closure are shifted to lower $A$-values,
the first deepest one occuring at $A=2$, famous $H$-particle ! (4) The shell
structure at $A=2$ vanishes only at $T\sim 30$ MeV, though for higher
$A$-values it happens so at $T\sim 20$ MeV.


title: Fermion Pair Production From an Electric Field Varying in Two Dimensions

abstract:
  The Hamiltonian describing fermion pair production from an arbitrarily
time-varying electric field in two dimensions is studied using a
group-theoretic approach. We show that this Hamiltonian can be encompassed by
two, commuting SU(2) algebras, and that the two-dimensional problem can
therefore be reduced to two one-dimensional problems. We compare the group
structure for the two-dimensional problem with that previously derived for the
one-dimensional problem, and verify that the Schwinger result is obtained under
the appropriate conditions.


title:
Rho-Omega Mixing Off Shell and Charge Symmetry Breaking In the N-N
  Potential

abstract:
  The role of the off-shell dependence of $\rho-\omega$ mixing in the charge
symmetry breaking nucleon-nucleon potential is discussed. It is shown that
models describing the off-shell dependence of $\rho-\omega$ mixing are not
sufficient to determine the charge symmetry breaking nucleon-nucleon potential.


title:
Two Model-Independent Results for the Momentum Dependence of Rho-Omega
  Mixing

abstract:
  Two model-independent results on the momentum-dependence of $\rho$-$\omega$
mixing are described. First, an explicit choice of interpolating fields for the
vector mesons is displayed for which both the mixing in the propagator and the
isospin-breaking at the nucleon-vector meson vertices (and hence also the
one-vector-meson-exchange contribution to NN charge symmetry breaking) vanish
identically at $q^2=0$. Second, it is shown, using the constraints of unitarity
and analyticity on the spectral function of the vector meson propagator, that
there is no possible choice of interpolating fields for the $\rho^0$,
$\omega^0$ mesons such that, with the $\rho\omega$ element of the propagator
defined by $\Delta^{\rho\omega}_{\mu\nu}(q^2)= (g_{\mu\nu}-q_\mu q_\nu
/q^2)$$\theta (q^2)/(q^2-m^2_\rho )(q^2- m^2_\omega )$, $\theta (q^2)$ is
independent of momentum. It follows that the standard treatment of charge
symmetry breaking in few-body systems cannot be interpreted as arising from any
realizable effective meson-baryon Lagrangian and must, therefore, be considered
purely phenomenological in content.


title: Analysis of the Low-Energy Theorem for \gamma p \to p \pi^0

abstract:
  The derivation of the `classical' low-energy theorem (LET) for \gamma p
\rightarrow p\pi^0 is re-examined and compared to chiral perturbation theory.
Both results are correct and are not contradictory; they differ because
different expansions of the same quantity are involved. Possible modifications
of the extended partially conserved axial-vector current relation, one of the
starting points in the derivation of the LET, are discussed. An alternate, more
transparent form of the LET is presented.


title: Rescaling of Nuclear Structure Functions

abstract:
  It is shown that nucleonic structure functions are $x-$ and $Q^{2}-$rescaled
in nuclei. The $x-$rescaling accounts for nuclear effects in the case of exact
scaling, while the $Q^{2}-$rescaling is responsible for a corresponding
modification of quantum corrections. This result is obtained in the leading
order for all flavour combinations and connects the two known models for the
EMC-effect. Electroproduction and gluonic nuclear structure functions are
calculated.


title: Spectral Statistics in Large Shell Model Calculations

abstract:
  The spectral statistics of low--lying states of $fp$ shell nuclei are studied
by performing large shell--model calculations with a realistic nuclear
interaction. For $Ca$ isotopes, we find deviations from the predictions of the
random--matrix theory which suggest that some spherical nuclei are not as
chaotic in nature as the conventional view assumes.


title: Compton scattering from a pion and off-shell effects

abstract:
  We discuss the most general form of the electromagnetic vertex of an
off-shell pion. The framework of chiral perturbation theory is used to
illustrate the representation dependence of the electromagnetic three-point
Green's function. For that purpose we discuss the concept of field
transformations which, in comparison with the standard Gasser and Leutwyler
Lagrangian, generate equivalent Lagrangians containing additional terms at
order p^4 proportional to the lowest-order equation of motion. We consider
Compton scattering from a pion to show that calculations involving different
off-shell effects in the s- and u-channel pole diagrams may nevertheless lead
to the same on-shell Compton scattering amplitude. This is a result of the
equivalence theorem which states that two equivalent Lagrangians predict the
same S-matrix elements even though they may generate a different off-shell
behaviour of Green's functions. We conclude that off-shell effects are not only
model dependent but also representation dependent.


title: Photo- and Electroproduction of Eta Mesons

abstract:
  Eta photo- and electroproduction off the nucleon is investigated in an
effective lagrangian approach that contains Born terms and both vector meson
and nucleon resonance contributions. In particular, we review and develop the
formalism for coincidence experiments with polarization degrees of freedom. The
different response functions appearing in single and double polarization
experiments have been studied. We will present calculations for structure
functions and kinematical conditions that are most sensitive to details of the
lagrangian, in particular with regard to contributions of nucleon resonances
beyond the dominant $S_{11}$(1535) resonance.


title: The Pion-Nucleon Form Factor From QCD Sum Rules

abstract:
  QCD sum rules are used to calculate the $q^2$ dependence of the $\pi NN$
coupling $g_{\pi NN} (q^2)$ in the spacelike region $0.5 \ {\mbox{GeV}}^2
\lesssim q^2 \lesssim 1.5\ {\mbox{GeV}}^2$. We study the Borel sum rule for the
three point function of one pseudoscalar and two nucleon currents up to order
four in the operator product expansion. The Borel transform is performed with
respect to the nucleon momenta, whereas the momentum $q^2$ of the pseudoscalar
vertex is kept fixed at spacelike values. The results can be well fitted using
a monopole form with a cutoff mass of about $\Lambda_\pi \approx 800 \
{\mbox{MeV}}.


title: Electromagnetic couplings in a collective model of the nucleon

abstract:
  We study the electromagnetic properties of the nucleon and its excitations in
a collective model. In the ensuing algebraic treatment all results for helicity
amplitudes and form factors can be derived in closed form in the limit of a
large model space. We discuss nucleon form factors and transverse
electromagnetic couplings in photo- and electroproduction, including transition
form factors that can be measured at new electron facilities.


title:
Saturation properties and incompressibility of nuclear matter: A
  consistent determination from nuclear masses

abstract:
  Starting with a two-body effective nucleon-nucleon interaction, it is shown
that the infinite nuclear matter model of atomic nuclei is more appropriate
than the conventional Bethe-Weizsacker like mass formulae to extract saturation
properties of nuclear matter from nuclear masses. In particular, the saturation
density thus obtained agrees with that of electron scattering data and the
Hartree-Fock calculations. For the first time using nuclear mass formula, the
radius constant $r_0$=1.138 fm and binding energy per nucleon $a_v$ = -16.11
MeV, corresponding to the infinite nuclear matter, are consistently obtained
from the same source. An important offshoot of this study is the determination
of nuclear matter incompressibility $K_{\infty}$ to be 288$\pm$ 28 MeV using
the same source of nuclear masses as input.


title:
The eta Photoproduction of Nucleons and The structure of the Resonance
  S11(1535) in The Quark Model

abstract:
  In this paper, we present our study on the $\eta$ photoproduction based on
the chiral quark model. We find that quark model provides a very good
description of the $\eta$ production with much less parameters, and the
threshold region is not a reliable source to determine the $\eta NN$ coupling
constant due to its strong dependence on the properties of the resonance
$S_{11}(1535)$. We suggest that the systematic data in $E_{lab}=1.2 \sim 1.4$
GeV region may help us to determine the $\eta NN$ coupling constant more
precisely.
  The structure of the resonance $S_{11}(1535)$ is discussed, we find that the
recent data from Mainz group bring the helicity amplitude much closer to the
quark model prediction. However, more studies need to be done to understand the
large $\eta N$ branching ratio of the resonance $S_{11}(1535)$. Our results
show that the quark model is a very good approach to study the underlying
structure of baryon resonances from the meson photoproduction data.


title:
Algebraic-eikonal approach to medium energy proton scattering from
  odd-mass nuclei

abstract:
  We extend the algebraic-eikonal approach to medium energy proton scattering
from odd-mass nuclei by combining the eikonal approximation for the scattering
with a description of odd-mass nuclei in terms of the interacting boson-fermion
model. We derive closed expressions for the transition matrix elements for one
of the dynamical symmetries and discuss the interplay between collective and
single-particle degrees of freedom in an application to elastic and inelastic
proton scattering from $^{195}$Pt.


title: Effective Field Theories

abstract:
  Three lectures on effective field theory given at the Seventh Summer School
in Nuclear Physics, Seattle June 19-30 1995.


title: Three-body correlations in few-body nuclei

abstract:
  A detailed comparison of Faddeev and variational wave functions for $^3$H,
calculated with realistic nuclear forces, has been made to study the form of
three-body correlations in few-body nuclei. Three new three-body correlations
for use in variational wave functions have been identified, which substantially
reduce the difference with the Faddeev wave function. The difference between
the variational upper bound and the Faddeev binding energy is reduced by half,
to typically $<2\%$. These three-body correlations also produce a significant
lowering of the variational binding energy for $^4$He and larger nuclei.


title: Subthreshold $K^+$ Production on Nuclei by $\pi^+$ Mesons

abstract:
  The inclusive $K^+$ mesons production in $\pi^+$--nucleus reactions in the
subthreshold energy regime is analyzed with respect to the one--step
($\pi^+n\to K^+\Lambda$) and the two--step ($\pi^+n\to \eta p_1,~ \eta p_2\to
K^+\Lambda$) incoherent production processes on the basis of an appropriate
folding model, which allows one to take into account the various forms of an
internal nucleon momentum distribution as well as on-- and off--shell
propagation of the struck target nucleon. Contrary to proton--nucleus reactions
primary reaction channel is found to be significant practically at all
considered energies. Detailed predictions for the $K^+$ total and invariant
differential cross sections from \piC-- and \piPb--collisions at subthreshold
energies are provided.


title:
Delays Associated with Elementary Processes in Nuclear Reaction
  Simulations

abstract:
  Scatterings, particularly those involving resonances, and other elementary
processes do not happen instantaneously. In the context of semiclassical
nuclear reaction simulations, we consider delays associated with an interaction
for incident quantum wave-packets. As a consequence, we express delays
associated with elementary processes in terms of elements of the scattering
matrix and phase shifts for elastic scattering. We show that, to within the
second order in density, the simulation must account for delays in scattering
consistently with the mean field in order to properly model thermodynamic
properties such as pressure and free-energy density. The delays associated with
nucleon-nucleon and pion-nucleon scattering in free space are analysed with
their nontrivial energy dependence. Finally, an example of s-channel scattering
of massless partons is studied, and scattering schemes in nuclear reaction
simulations are investigated in the context of scattering delays.


title: On the Numerical Solution of the Time-Dependent Schroedinger Equation

abstract:
  An algorithm for the numerical solution of the Schr\"odinger equation in the
case of a time dependent potential is proposed. Our simple modification
upgrades the well known method of Koonin while negligibly increasing the
computing time. In the presented test the accuracy is enhanced by up to an
order of magnitude.


title:
Recent Chalk River Experiments on Superallowed $0^{+} \to 0^{+}$ Beta
  Decays

abstract:
  Two experiments, (1) a measurement of the superallowed $0^{+} \rightarrow
0^{+}$ branching ratio in $^{10}$C, and (2) a measurement of (or limit on)
non-analogue $0^{+} \rightarrow 0^{+}$ branches in $^{38m}$K, $^{46}$V,
$^{50}$Mn and $^{54}$Co, are described. The implications these experiments have
on the test of the conservation of the weak vector current (CVC) and the
unitarity of the Cabibbo-Kobayashi-Maskawa matrix are surveyed.


title: Superallowed Fermi Beta Decay -- a Status Report

abstract:
  Data on superallowed Fermi beta decay in nuclei are compiled and
electromagnetic corrections discussed. Recommended values for the weak vector
coupling constant and the leading element of the Cabibbo-Kobayashi-Maskawa
mixing matrix are given. Comments on neutron decay and limits extracted on
extensions to the Standard Model are made.


title: Delta Excitations in Neutrino-Nucleus Scattering

abstract:
  We derive the contribution of $\Delta$-h excitations to quasielastic
charged-current neutrino-nucleus scattering in the framework of relativistic
mean-field theory. We discuss the effect of $\Delta$ production on the
determination of the axial mass $M_A$ in neutrino scattering experiments.


title: Effect of Nucleon Structure Variation in Super-allowed Fermi Beta-decay

abstract:
  There is a well known anomaly between the value of the Fermi decay constant
extracted from super-allowed Fermi beta-decay of nuclear isotriplets and that
required by unitarity of the Cabibbo-Kobayashi-Maskawa matrix. This discrepancy
remains at the level of a few tenths of a percent after the most rigorous
investigation of conventional nuclear and radiative corrections. Within the
framework of the quark-meson coupling model of nuclear matter, which has been
previously applied successfully to phenomena such as nuclear saturation and
nuclear charge symmetry violation, we show that it is possible to understand a
significant fraction of the observed anomaly.


title:
Path integral approach to no-Coriolis approximation in heavy-ion
  collisions

abstract:
  We use the two time influence functional method of the path integral approach
in order to reduce the dimension of the coupled-channels equations for
heavy-ion reactions based on the no-Coriolis approximation. Our method is
superior to other methods in that it easily enables us to study the cases where
the initial spin of the colliding particle is not zero. It can also be easily
applied to the cases where the internal degrees of freedom are not necessarily
collective coordinates. We also clarify the underlying assumptions in our
approach.


title:
Effects of mass renormalization on the surface properties of heavy-ion
  fusion potential

abstract:
  We discuss the effects of fast nuclear excitations on heavy-ion fusion
reactions at energies near and below the Coulomb barrier. Using the fusion of
two $^{40}$Ca nuclei as an example and the inversion method, we show that the
mass renormalization induced by fast nuclear excitations leads to a large
surface diffuseness in the effective potential for heavy-ion fusion reactions.


title: Charge Symmetry Violation in Nuclear Physics

abstract:
  The study of charge symmetry violation in nuclear physics is a potentially
enormous subject. Through a few topical examples we aim to show that it is not
a subject of peripheral interest but rather goes to the heart of our
understanding of hadronic systems.


title:
Large-basis shell model studies of light nuclei with a multi-valued
  G-matrix effective interaction

abstract:
  Large-basis shell model studies of low-lying excitations in light nuclei from
4He to 7Li have been performed with a multi-valued G-matrix effective
interaction, as recently suggested by Haxton et al.. Calculations were
performed relative to the vacuum (``no core") using very large, separable model
spaces containing all excitations with unperturbed energies up to 8\hbar\Omega.
Using G matrices derived from a new Nijmegen potential, we achieve a very
satisfactory description of these excitations.


title: Change of shape in the yrast sequence in 50Cr

abstract:
  In shell model calculations for the yrast even spin states of 50Cr, the
static quadrupole moments of the low spin states 2+_1 and 4+_1 are negative but
those of the high spin states 10+_1, 12+_1 and 14+_1 are positive. Even spin
states beyond the single j shell limit, J_max=14, again have negative moments.
While the B(E2)'s for the J -> J-2 transitions are strongest along the yrast
path for J <= 8, it is found that the transition from the second J=10 state to
the first J=8 state (10+_2 -> 8+_1) is much stronger than the 10+_1 -> 8+_1
transition. We also note that while the 16+_1 -> 14+_1 transition is weak, the
16+_1 -> 14+_2 is quite strong.


title:
Incompressibility of nuclear matter, and Coulomb and volume-symmetry
  coefficients of nucleus incompressibility in the relativistic mean field
  theory

abstract:
  The volume coefficient $K$(=incompressibility of the nuclear matter), the
Coulomb coefficient $K_c$, and the volume-symmetry coefficient $K_{vs}$ of the
nucleus incompressibility are studied in the framework of the relativistic mean
field theory, with aid of the scaling model. It is found that $K= 300\pm 50$MeV
is necessary to account for the empirical values of $K_v$, $K_c$, and $K_{vs}$,
simultaneously. The result is independent on the detail descriptions of the
potential of the $\sigma$-meson self-interaction and is almost independent of
the strength of the $\omega$-meson self-interaction.


title:
Nucleon mean free path in nuclear matter based on nuclear
  Schwinger-Dyson formalism

abstract:
  A mean free path of nucleon moving through nuclear matter with kinetic energy
of more than 100MeV is formulated based on the bare vertex nuclear
Schwinger-Dyson (BNSD) method in the Walecka model. The self-energy which is
derived from the higher order diagrams more than the forth order includes the
Feynman part of propagator of energetic nucleon and grows up rapidly as an
increase of kinetic energy. To avoid too large growth of these diagrams, meson
propagators are modified by introducing some form factors to take account of a
internal structure of hadron. It is confirmed that the mean free path
calculated by the BNSD method agrees good with experimental data if a
reasonable form factor is chosen, i.e., a dipole (quadrupole) type of form
factor with a cut-off parameter about 750 MeV $\sim$ 1000 MeV (1200 MeV $\sim$
1500 MeV).


title: Macroscopic-Microscopic Mass Models

abstract:
  We discuss recent developments in macroscopic-microscopic mass models,
including the 1992 finite-range droplet model, the 1992 extended-Thomas-Fermi
Strutinsky-integral model, and the 1994 Thomas-Fermi model, with particular
emphasis on how well they extrapolate to new regions of nuclei. We also address
what recent developments in macroscopic-microscopic mass models are teaching us
about such physically relevant issues as the nuclear curvature energy, a new
congruence energy arising from a greater-than-average overlap of neutron and
proton wave functions, the nuclear incompressibility coefficient, and the
Coulomb redistribution energy arising from a central density depression. We
conclude with a brief discussion of the recently discovered rock of metastable
superheavy nuclei near 272:110 that had been correctly predicted by
macroscopic-microscopic models, along with a possible new tack for reaching an
island near 290:110 beyond our present horizon.


title:
Compressional properties of nuclear matter in the relativistic mean
  field theory with the excluded volume effects

abstract:
  Compressional properties of nuclear matter are studied by using the mean
field theory with the excluded volume effects of the nucleons. It is found that
the excluded volume effects make it possible to fit the empirical data of the
Coulomb coefficient $K_{c}$ of nucleus incompressibility, even if the volume
coefficient $K$ is small($\sim 150$MeV). However, the symmetry properties favor
$K=300\pm 50$MeV as in the cases of the mean field theory of point-like
nucleons.


title: phi-meson in Nuclear Matter

abstract:
  $\phi$-meson mass in nuclear matter ($m_{\phi}^*$) is investigated using an
effective Lagrangian of $\phi$ interacting with octet baryons. $m_{\phi}^*$
decreases by a few \% in nuclear matter due to the current conservation and
effective nucleon/hyperon masses. Its implication to the p-A and A-A collisions
are briefly discussed.


title: Quantum Chaos, Degeneracies and Exceptional Points

abstract:
  It is argued that, if a regular Hamiltonian is perturbed by a term that
produces chaos, the onset of chaos is shifted towards larger values of the
perturbation parameter if the unperturbed spectrum is degenerate and the
lifting of the degeneracy is of second order in this parameter. The argument is
based on the behaviour of the exceptional points of the full problem.


title: Nuclear Shell Structure and Chaotic Dynamics in Hexadecapole Deformation

abstract:
  The effect of an axially symmetric hexadecapole term is investigated in a
strongly deformed quadrupole potential. While the system is nonintegrable and
shows significant chaotic behaviour classically, the quantum mechanical
treatment not only produces a general smoothing effect with regard to chaos but
even yields a pronounced shell structure at certain hexadecapole strength
parameter values for oblate and prolate deformation.


title:
A Comment on General Formulae for Polarization Observables in Deuteron
  Electrodisintegration and Linear Relations

abstract:
  We establish a simple, explicit relation between the formalisms employed in
the treatments of polarization observables in deuteron two-body
electrodisintegration published by Arenh\"ovel, Leidemann, and Tomusiak in
Few-Body Systems {\bf 15}, 109 (1993) and the results of the present authors
published in Phys.~Rev.~C {\bf 40}, 2479 (1989). We comment on the overlap
between the two sets of results.


title:
Relativistic Calculations for Photonuclear Reactions (II).
  Nonrelativistic reductions and nuclear medium effects

abstract:
  The relativistic amplitude for the direct knock-out contribution to $\left(
\gamma, p \right)$ reactions on nuclei is reduced to a nonrelativistic form
using an effective Pauli reduction scheme. The reduction is carried out to
second order in the inverse nucleon mass. It is found that the interaction
Hamiltonian appearing in the nonrelativistic amplitude has significant
dependence, starting at second order, on the vector and scalar mean nuclear
potentials. These strong medium modifications are absent in traditional
nonrelativistic calculations. Detailed comparisons show that these
modifications are crucial to understanding the differences between relativistic
and nonrelativistic models. These differences are also examined through
reduction of the relativistic amplitude via the Foldy-Wouthuysen
transformation. Similar medium modifications are obtained in this case as well.
We discuss the implications of these medium modifications for the consistency
of existing nonrelativistic calculations.


title:
Bulk properties of nuclear matter in the relativistic Hartree
  approximation with cut-off regularization

abstract:
  A method of cut-off regularization is proposed to evaluate vacuum corrections
in nuclear matter in the framework of the Hartree approximation. Bulk
properties of nuclear matter calculated by this method are a good agreement
with results analyzed by empirical values. The vacuum effect is quantitatively
evaluated through a cut-off parameter and its role for saturation property and
compressional properties is clarified.


title: Kaon Energies in Dense Matter

abstract:
  We discuss the role of kaon-nucleon and nucleon-nucleon correlations in kaon
condensation in dense matter. Correlations raise the threshold density for kaon
condensation, possibly to densities higher than those encountered in stable
neutron stars.


title:
Realistic Model of the Nucleon Spectral Function in Few- and Many-
  Nucleon Systems

abstract:
  By analysing the high momentum features of the nucleon momentum distribution
in light and complex nuclei, it is argued that the basic two-nucleon
configurations generating the structure of the nucleon Spectral Function at
high values of the nucleon momentum and removal energy, can be properly
described by a factorised ansatz for the nuclear wave function, which leads to
a nucleon Spectral Function in the form of a convolution integral involving the
momentum distributions describing the relative and center-of-mass motion of a
correlated nucleon-nucleon pair embedded in the medium. The Spectral Functions
of $^3He$ and infinite nuclear matter resulting from the convolution formula
and from many-body calculations are compared, and a very good agreement in a
wide range of values of nucleon momentum and removal energy is found.
Applications of the model to the analysis of inclusive and exclusive processes
are presented, illustrating those features of the cross section which are
sensitive to that part of the Spectral Function which is governed by
short-range and tensor nucleon-nucleon correlations.


title: Pion correlation from Skyrmion-AntiSkyrmion annihilation

abstract:
  We study two pion correlations from Skyrmion and antiSkyrmion collision,
using the product ansatz and an approximate random grooming method for nucleon
projection. The spatial-isospin coupling inherent in the Skyrme model, along
with empirical averages, leads to correlations not only among pions of like
charges but also among unlike charge types.


title: Rho-Omega Mixing via QCD Sum Rules with Finite Mesonic Widths

abstract:
  Based on the analysis of both Borel and Finite-Energy QCD sum rules, the
inclusion of finite mesonic widths leads to a dramatic effect on the
predictions for the momentum dependence of the rho-omega mixing matrix element.
It is shown that the rho-omega mixing matrix element traditionally discussed in
the literature, has the same sign and similar magnitude in the space-like
region as its on-shell value. This contrasts the zero-width result where the
mixing matrix element is typically of opposite sign in the space-like region.


title: Theory of Multiphonon Excitation in Heavy-Ion Collisions

abstract:
  We study the effects of channel coupling in the excitation dynamics of giant
resonances in relativistic heavy ions collisions. For this purpose, we use a
semiclassical approximation to the Coupled-Channels problem and separate the
Coulomb and the nuclear parts of the coupling into their main multipole
components. In order to assess the importance of multi-step processes, we
neglect the resonance widths and solve the set of coupled equations exactly.
Finite widths are then considered. In this case, we handle the coupling of the
ground state with the dominant Giant Dipole Resonance exactly and study the
excitation of the remaining resonances within the Coupled-Channels Born
Approximation. A comparison with recent experimental data is made.


title: From Chiral Mean Field to Walecka Mean Field and Kaon Condensation

abstract:
  A unified treatment of normal nuclear matter described by Walecka's mean
field theory and kaon condensed matter described by chiral perturbation theory
is proposed in terms of mean fields of an effective chiral Lagrangian. The BR
scaling is found to play a key role in making the link between the ground state
properties of nuclear matter and the fluctuation into the strangeness-flavor
direction. A simple prediction for kaon condensation is presented.


title: Shell Model Monte Carlo Studies of $\gamma$-Soft Nuclei

abstract:
  We present Shell Model Monte Carlo calculations for nuclei within the full
major shell 50-82 for both protons and neutrons. The interaction is determined
solely by self-consistency and odd-even mass differences. The methods are
illustrated for ${}^{124}$Sn, ${}^{128}$Te and ${}^{124}$Xe. We calculate shape
distributions, moments of inertia and pairing correlations as functions of
temperature and angular velocity. Our calculations are the first microscopic
evidence of $\gamma$-softness of nuclei in this region.


title: Isospin Violations in the Pion-Nucleon System

abstract:
  We examine the effect of isospin-violating meson-nucleon coupling constants
on low-energy pion-nucleon scattering. We compute the couplings in the context
of a nonrelativistic quark model. The difference between the up and down
constituent masses induces a coupling of the neutral pion to the proton that is
slightly larger than the corresponding one for the neutron. This difference
generates a large isospin-violating correction---proportional to the
isospin-even contribution arising from the nucleon Born terms---to the
charge-exchange ($\pi^{-}p \rightarrow \pi^{0}n$) amplitude. In contrast to the
isospin-conserving case, this correction is not cancelled by $\sigma$-meson
exchange; in our model there is no isospin-violating $NN\sigma$ coupling at
$q^2=0$. As a result, we find a violation of the triangle identity consistent
with the one reported by Gibbs, Ai, and Kaufmann from a recent analysis of
pion-nucleon data.


title:
Production of $K^-$-mesons in proton-proton and proton-nucleus
  interactions at various energies

abstract:
  The experimental data on the production of $K^-$-mesons in pp-collisions are
analyzed and a method of the unified description of these data in a broad
energy range for primary protons is proposed. The $K^-$-mesons production in
pA-collisions is considered. The simple formulas for inclusive cross sections
of the $K^-$ production in these collisions are given. The results of the
calculations by these formulas are compared with the available experimental
data.


title: Magnetic Moments of the Octet Baryons in a Chiral Quark Potential Model

abstract:
  In quark potential models, two--body current contributions to baryon magnetic
moments arise necessarily to satisfy the continuity equation for the
electromagnetic current. On the other hand, the naive additive quark model
predicts the experimental octet magnetic moments to within 5$\%$. We
demonstrate that consistently derived two--body current contributions to the
octet baryon magnetic moments are individually large, but tend to cancel each
other globally.


title: Reheating after Supercooling in the Chiral Phase Transition

abstract:
  The chirally symmetric quark-gluon plasma produced in energetic heavy-ion
collisions is predicted to supercool at the late stages of its evolution. The
thermal energy is then transformed into the potential energy associated with an
energetically unfavorable field configuration. Since the system is in an
unstable state it eventually rolls down to the true minimum of the effective
chiral potential. When this motion is described in terms of the sigma-model, we
find that the energy of the coherent $\sigma-$field is very efficiently
converted into pionic excitations due to anharmonic oscillations around this
minimum. The system is expected to partially thermalize before its
disintegration.


title: Quantum Dissipation

abstract:
  We address the question of the microscopic origin of dissipation in
collective motion of a quantum many--body system in the framework of a
parametric random matrix approach to the intrinsic dynamics. We show that the
fluctuation--dissipation theorem is generally violated and, moreover, energy
diffusion has a markedly non--Gaussian character and the corresponding
distribution has very long tails. Such features do not support a Langevin or
Fokker--Planck approach to dissipation in collective nuclear motion.


title: Antiprotonic Helium Atoms

abstract:
  Metastable antiprotonic helium atoms $^{3,4}\! H\! e\bar pe$ have been
discovered recently in experiments of the delayed annihilation of antiprotons
in helium media. These exotic atoms survive for an enormous time (about tens of
microseconds) and carry the extremely large total angular momentum $L\sim
30-40$. The theoretical treatment of the intrinsic properties of antiprotonic
helium atoms, their formation and collisions with atoms and molecules is
discussed.


title: Chiral Dynamics and the $S_{11}(1535)$ Nucleon Resonance

abstract:
  The $SU(3)$ chiral effective lagrangian at next-to-leading order is applied
to the S-wave meson-baryon interaction in the energy range around the $\eta N$
threshold. Potentials are derived from this lagrangian and used in a coupled
channel calculation of the $\pi N$, $\eta N$, $K \Lambda$, $K \Sigma$ system in
the isospin-$1/2$, $l=0$ partial wave. Using the same parameters as obtained
from a fit to the low energy $\overline{K} N$ data it is found that a
quasi-bound $K \Sigma$-state is formed, with properties remarkably similar to
the $S_{11}(1535)$ nucleon resonance. In particular, we find a large partial
decay width into $\eta N$ consistent with the empirical data.


title:
Nucleon and pion electromagnetic form factors in a light-front
  constituent quark model

abstract:
  Nucleon and pion electromagnetic form factors are evaluated in the spacelike
region within a light-front constituent quark model, where eigenfunctions of a
mass operator, reproducing a large set of hadron energy levels, are adopted and
quark form factors are considered in the one-body current. The hadron form
factors are sharply affected by the high momentum tail generated in the wave
function by the one-gluon-exchange interaction. Useful information on the
electromagnetic structure of light constituent quarks can be obtained from the
comparison with nucleon and pion experimental data.


title: Charge form factor of $\pi$ and $K$ mesons

abstract:
  The charge form factor of $\pi$ and $K$ mesons is evaluated adopting a
relativistic constituent quark model based on the light-front formalism. The
relevance of the high-momentum components of the meson wave function, for
values of the momentum transfer accessible to $CEBAF$ energies, is illustrated.
The predictions for the elastic form factor of $\pi$ and $K$ mesons are
compared with the results of different relativistic approaches, showing that
the measurements of the pion and kaon form factors planned at $CEBAF$ could
provide information for discriminating among various models of the meson
structure.


title:
Final state interactions and $NN$ correlations: are the latter
  observable?

abstract:
  Are effects of short range correlations in the ground state of the target
nucleus (initial state correlations ISC) observable in experiments on
quasielastic $A(e,e'p)$ scattering at large missing momentum $p_{m}$? Will the
missing momentum spectrum observed at CEBAF be overwhelmed by final state
interactions (FSI) of the struck proton? The recent advances in the theory of
FSI and findings of complex interplay and strong quantum-mechanical
interference of FSI and ISC contributions to scattering at $p_{m}\gsim
1$\,fm$^{-1}$ are reviewed. We conclude that for $p_m \gsim 1$ \, fm$^{-1}$
quasielastic scattering is dominated by FSI effects and the sensitivity to
details of the nuclear ground state is lost.


title: Numerical Convergence in Solving the Vlasov Equation

abstract:
  When the Vlasov equation is investigated numerically using the method of test
particles, the particle-particle interactions that inevitably arise in the
simulation (but are not present in the Vlasov equation itself) result in an
accumulation of errors which eventually drive the collection of test particles
toward a state of classical thermal equilibrium. We estimate the rate at which
these errors accumulate.


title:
Relativistic Effects in Simulations of the Fragmentation Process with
  the Microscopic Framework

abstract:
  We simulate the fragmentation processes in the \CaCa collisions at the
bombarding energy 1.05 GeV/u using the Lorentz covariant RQMD and the
non-covariant QMD approaches, incorporated with the statistical decay model. By
comparing the results of RQMD with those of QMD, we examine the relativistic
effects and find that the multiplicity of the $\alpha$ particle after the
statistical decay process is sensitive to the relativistic effects. It is shown
that the Lorentz covariant approach is necessary to analyze the fragmentation
process even at the energy around \Elab = 1 GeV/u as long as we are concerned
with the final observables of the mass distribution, particularly, the light
fragments around $A = 3 \sim 4$.


title: On the possibility of an eta-meson light nucleus bound state formation

abstract:
  The resonance and bound--state poles of the amplitude describing elastic
scattering of $\eta$-meson off the light nuclei $^2H$,\,$^3H$,\, $^3He$, and
$^4He$ are calculated in the framework of a microscopic approach based on
few--body equations. For each of the nuclei, the two--body parameters that
enhance the $\eta N$--attraction which generate quasi--bound states, are also
determined.


title: Interaction of eta-meson with light nuclei

abstract:
  A microscopic treatment of $\eta$--nucleus scattering is presented. When
applying the underlying exact integral equations, the excitation of the target
are neglected, and an input $\eta N$ amplitude is chosen which reproduces the
$S_{11}(1535)$ resonance. It is shown that the $\eta$--nucleus scattering
lengths are quite sensitive to the $\eta N$ parameters and the nuclear wave
functions. For a special choice of the parameters an $\eta {^4\!H}e$
quasi--bound state occurs.