title: Remarks on the Delta(+) mass

abstract:
  We question the reliability of current estimates for the Delta(+) mass. We
explain why the standard value, determined from pion photoproduction, should
not be used in conjunction with present estimates for the Delta(++) and
Delta(0) masses, determined from pion-nucleon scattering. The resultant mass
splittings are internally inconsistent. We also briefly comment on
discrepancies found when `theoretical' and `experimental' values for the Delta
masses are compared.


title: Effects of Spin-Isospin Modes in Transport Simulations

abstract:
  In-medium properties derived for nuclear matter in a microscopic pi +
nucleon-hole + delta-hole model are incorporated into transport simulations of
nuclear collisions by means of a local-density approximation and by utilizing a
local medium frame. Certain features of the transport results differ from those
based on the corresponding vacuum properties. Comparisons of the pi and delta
production rates, as well as pion energy spectra, are discussed in particular.


title: Temperature and thermodynamic instabilities in heavy ion collisions

abstract:
  We investigate thermodynamic properties and instability conditions in
intermediate energy heavy ion reactions. We define locally thermodynamic
variables, i.e. density, pressure and temperature, directly from the phase
space distribution of a relativistic transport calculation. In particular,
temperatures are determined by a fit to two covariant hot Fermi distributions
thus taking into account possible anisotropic momentum configurations. We
define instability independent from the nuclear matter spinodal by the
criterion that the effective compressibility becomes negative. The method is
applied to a semi-central Au on Au reaction at 600 MeV/nucleon. We investigate
in particular the center of the participant and the spectator matter. In the
latter we find a clear indication of instability with conditions of density and
temperature that are consistent with experimental determinations.


title:
Gluon Radiation and Coherent States in Ultrarelativistic Nuclear
  Collisions

abstract:
  We explore the correspondence between classical gluon radiation and quantum
radiation in a coherent state for gluons produced in ultrarelativistic nuclear
collisions. The expectation value of the invariant momentum distribution of
gluons in the coherent state is found to agree with the gluon number
distribution obtained classically from the solution of the Yang-Mills
equations. A criterion for the applicability of the coherent state formalism to
the problem of radiation in ultrarelativistic nucleus-nucleus collisions is
discussed. This criterion is found to be fulfilled for midrapidity gluons with
perturbative transverse momenta larger than about 1-2 GeV and produced in
collisions between valence partons.


title: Generalized Polarizabilities and the Chiral Structure of the Nucleon

abstract:
  We are studying the electron scattering process e p to e' p' gamma in order
to obtain information on the genuine virtual Compton scattering (VCS) process
gamma^* N to gamma N. In addition to the two kinematical variables of real
Compton scattering, e.g. the scattering angle theta and the energy omega' of
the outgoing photon, the invariant amplitude for VCS depends on a third
kinematical variable, which we choose as the absolute value of the
three-momentum transfer to the nucleon. The structure-dependent coefficients in
the VCS amplitude therefore acquire a momentum dependence and are termed
``generalized polarizabilities'' of the nucleon in analogy to real Compton
scattering. Utilizing the heavy baryon formalism of chiral perturbation theory
we present predictions for the momentum dependence of the ``generalized
polarizabilities'' and discuss the VCS response functions to be measured in the
scheduled electron scattering experiments.


title: Medium effects in K^+ nuclear interactions

abstract:
  Total and reaction cross sections are derived self consistently from the
attenuation cross sections measured in transmission experiments at the AGS for
K^+ on Li^6, C, Si and Ca in the momentum range of 500-700 MeV/c by using a
V_{opt}=t_{eff}(rho)rho optical potential. Self consistency requires, for the
KN in-medium t matrix, that Im t_{eff}(rho) increases linearly with the average
nuclear density in excess of a threshold value of 0.088+-0.004 fm^-3. The
density dependence of Re t_{eff}(rho) is studied phenomenologically, and also
applying a relativistic mean field approach, by fitting the integral cross
sections. The real part of the optical potential is found to be systematically
less repulsive with increasing energy than expected from the free-space
repulsive KN interaction. When the elastic scattering data for Li^6 and C at
715 MeV/c are included in the analysis, a tendency of Re V_{opt} to generate an
attractive pocket at the nuclear surface is observed.


title: Minijets in ultrarelativistic heavy ion collisions at future colliders

abstract:
  The role of minijet production as initial conditions for QGP production at
$\tau\sim 0.1 fm/c$ in nuclear collisions at the LHC and RHIC energies is
discussed.


title: Semiclassical Interpretation of the Mass Asymmetry in Nuclear Fission

abstract:
  We give a semiclassical interpretation of the mass asymmetry in the fission
of heavy nuclei. Using only a few classical periodic orbits and a cavity model
for the nuclear mean field, we reproduce the onset of left-right asymmetric
shapes at the fission isomer minimum and the correct topology of the
deformation energy surface in the region of the outer fission barrier. We point
at the correspondence of the single-particle quantum states responsible for the
asymmetry with the leading classical orbits, both lying in similar equatorial
planes perpendicular to the symmetry axis of the system.


title: Exchange Currents for Hypernuclear Magnetic Moments

abstract:
  The meson(K and $\pi$) exchange currents for the hypernuclear magnetic
moments are calculated using the effective Lagrangian method. The seagull
diagram, the mesonic diagram and the $\Sigma^0$-excitation diagram are
considered. The $\Lambda$-N exchange magnetic moments for the
${}^5_{\Lambda}He$, ${}^6_{\Lambda}He$ and ${}^6_{\Lambda}Li$ are calculated
employing the harmonic oscillator shell model. It is found that the two-body
correction is about -9% of the single particle value for ${}^5_{\Lambda}He$.
The $\pi$ exchange current, induced only in the $\Sigma^0$-excitation diagram,
is found to give dominant contribution for the isovector magnetic moments of
hypernuclei with A=6.


title: The Nucleon-Nucleon Interaction in a Chiral Constituent Quark Model

abstract:
  We study the short-range nucleon-nucleon interaction in a chiral constituent
quark model by diagonalizing a Hamiltonian comprising a linear confinement and
a Goldstone boson exchange interaction between quarks. The six-quark harmonic
oscillator basis contains up to two excitation quanta. We show that the highly
dominant configuration is $\mid s^4p^2[42]_O [51]_{FS}>$ due to its specific
flavour-spin symmetry. Using the Born-Oppenheimer approximation we find a
strong effective repulsion at zero separation between nucleons in both $^3S_1$
and $^1S_0$ channels. The symmetry structure of the highly dominant
configuration implies the existence of a node in the S-wave relative motion
wave function at short distances. The amplitude of the oscillation of the wave
function at short range will be however strongly suppressed. We discuss the
mechanism leading to the effective short-range repulsion within the chiral
constituent quark model as compared to that related with the one-gluon exchange
interaction.


title: Properties of Exotic Matter for Heavy Ion Searches

abstract:
  We examine the properties of both forms of strange matter, small lumps of
strange quark matter (strangelets) and of strange hadronic matter (Metastable
Exotic Multihypernuclear Objects: MEMOs) and their relevance for present and
future heavy ion searches. The strong and weak decays are discussed separately
to distinguish between long-lived and short-lived candidates where the former
ones are detectable in present heavy ion experiments while the latter ones in
future heavy ion experiments, respectively. We find some long-lived strangelet
candidates which are highly negatively charged with a mass to charge ratio like
a anti deuteron (M/Z=-2) but masses of A=10 to 16. We predict also many
short-lived candidates, both in quark and in hadronic form, which can be highly
charged. Purely hyperonic nuclei are bound and have a negative charge while
carrying a positive baryon number. We demonstrate also that multiply charmed
exotics (charmlets) might be bound and can be produced at future heavy ion
colliders.


title: E2/M1 ratio from the Mainz $p(\vec{\gamma}, p)\pi^0$

abstract:
  We reply to the Comment of R.L. Workman on the E2/M1 ratio from the Mainz
photoproduction data, nucl-th/9702052. We support our published result for the
E2/M1 ratio of REM = -(2.5 +- 0.2 +- 0.2)%.


title: Coexistence of Ordered and Chaotic States in Nuclear Structure

abstract:
  In atomic nuclei, as in other many-body systems, the classical phase space is
mixed, so ordered and chaotic states generally coexist. In this contribution we
discuss some models, showing the transition from order to chaos. In several
cases a clear correspondence between classical and quantum chaos has been
established. In particular the transition from ordered to chaotic states will
be discussed in the framework of the shell and roto-vibrational models.


title:
Precision Theorectical Tests of Effective Lagrangians: Pion
  Photoproduction from Threshold Through the Delta Resonance

abstract:
  We shall review here our current knowledge and new frontiers of the pion
photoproduction study, from threshold through the Delta resonance region,
emphasizing the hadron physics program, of interest to a 250 MeV, high duty
factor electron facility, such as the upgraded MAX-lab at the Lund University,
Sweden, where it would be possible to produce tagged photons of high quality,
with energy below approximately 200 MeV.


title: Mainz "measurement" of the $E2/M1$ ratio in the $N-\Delta$ transition

abstract:
  We comment on the recent Mainz "measurement" (PRL78 (1997) 606) of the
$E2/M1$ ratio in the $N-\Delta$ electromagnetic transition. Analyzing the Mainz
data using an effective Lagrangian approach, we find this ratio to be
(-3.19$\pm$0.24)%.


title: Higher-Order Nuclear-Size Corrections in Atomic Hydrogen

abstract:
  Nuclear-size corrections of order $(Z \alpha)^5$ and $(Z \alpha)^6$ to the
S-state levels of hydrogenic atoms are considered. These nuclear-elastic
contributions are somewhat smaller than the polarizability (nuclear-inelastic)
corrections for deuterium, but are of comparable or larger size for the
hydrogen case. For deuterium the (attractive) nonrelativistic $(Z \alpha)^5$
correction to the 2S-1S transition is 0.49 kHz, while the (repulsive)
relativistic $(Z \alpha)^6$ contribution is -3.40 kHz. For the proton the
corresponding corrections are 0.03 kHz and -0.61 kHz, respectively. The $(Z
\alpha)^5$ contribution largely cancels the Coulomb-retardation part of the
nuclear-polarization correction.


title: Hydrodynamical Evolution of a Quark-Gluon Plasma Drop With Boundary

abstract:
  We consider the evolution of a spherically symmetric Quark-Gluon Plasma (QGP)
drop with limited size in the framework of relativistic hydrodynamics. In the
presence of the boundary, the expanding and cooling of QGP drop may appear as
oscillating processes, which realize via multiple traveling of rarefaction and
compression waves through the plasma and lead to increasing of plasma
life-time. Within this picture, deflagration is the main possible way of
hadronization. The slow cooling mechanism also leads to a significant
enhancement of photon yield in comparison with Bjorken scenario.


title:
Matrix Model for the Transition Expansion of Dispersive Corrections to
  Nucleon-Nucleus Total Cross Sections

abstract:
  A finite-dimensional matrix model for the nucleon-nucleon cross section
operator is used to calculate the dispersive correction to nucleon-nucleus
total cross sections, and the leading terms in its expansion in the number of
inelastic transitions in the high-energy limit where the longitudnal momentum
transfers can be ignored.


title:
Quantum Molecular Dynamics Approach to the Nuclear Matter Below the
  Saturation Density

abstract:
  Quantum molecular dynamics is applied to study the ground state properties of
nuclear matter at subsaturation densities. Clustering effects are observed as
to soften the equation of state at these densities. The structure of nuclear
matter at subsaturation density shows some exotic shapes with variation of the
density.


title:
Skyrmion dynamics on the unstable manifold and the nucleon-nucleon
  interaction

abstract:
  The unstable manifold of the B=2 sector of the Skyrme model is constructed
numerically using the gradient-flow method. Following paths of steepest descent
from the B=2 hedgehog, we apply a collective coordinate description for the
motion on the manifold to extract a Hamiltonian, approximately valid for the
quantum description of the low-energy nucleon-nucleon interaction. The
resulting potential - obtained in the Born-Oppenheimer approximation - is in
qualitative agreement with phenomenological potentials.


title:
Interplay of parton and hadron cascades in nucleus-nucleus collisions at
  the CERN SPS and RHIC

abstract:
  We introduce a Monte Carlo space-time model for high-energy collisions with
nuclei, involving the dynamical interplay of perturbative QCD parton production
and evolution, with non-perturbative parton-cluster formation and `afterburner'
cascading of formed pre-hadronic clusters plus hadron excitations. This
approach allows us to trace the space-time history of parton and hadron degrees
of freedom of nuclear collisions on the microscopical level of parton and
hadron cascades in both position and momentum space, from the instant of
nuclear overlap to the final yield of particles. In applying this approach, we
analyze Pb+Pb collisions at the CERN SPS with beam energy 158 GeV (sqrt{s}/A =
17 GeV) and Au+Au collisions at RHIC with collider energy \sqrt{s}/A = 200 GeV.
We find that the perturbative QCD parton production and cascade development
provides an important contribution to particle production at central
rapidities, and that the `afterburner' cascading of pre-hadronic clusters and
formed hadrons emerging from the parton cascade is essential. The overall
agreement of our model calculations including the `afterburner' cascading with
the observed particle spectra at the CERN SPS is fairly good, whereas the
neglect of the final-state interactions among hadronic excitations deviates
significantly.


title: Towards Reconstructing the Final Stage of Heavy Ion Collisions

abstract:
  A Fourier inversion problem lies at the heart of determining spatio-temporal
characteristica of the final stage of a heavy ion collision: From the measured
two-particle momentum correlations C(p_1,p_2) of identical particles, pions
say, a Hanbury-Brown /Twiss (HBT) interferometric analysis aims at extracting
as much information as possible about the Wigner phase space density S(x,p) of
pion emitting sources in the collision region. Here, we discuss how this
analysis allows to separate the effects of temperature and transverse flow
which cannot be disentangled completely on the basis of single-particle
spectra.


title: Neutron star properties in the Thomas-Fermi model

abstract:
  The modern nucleon-nucleon interaction of Myers and Swiatecki, adjusted to
the properties of finite nuclei, the parameters of the mass formula, and the
behavior of the optical potential is used to calculate the properties of
$\beta$--equilibrated neutron star matter, and to study the impact of this
equation of state on the properties of (rapidly rotating) neutron stars and
their cooling behavior. The results are in excellent agreement with the outcome
of calculations performed for a broad collection of sophisticated
nonrelativistic as well as relativistic models for the equation of state.


title: A statistical theory of the mean field

abstract:
  A statistical theory of the mean field is developed. It is based on the
proposition that the mean field can be obtained as an energy average. Moreover,
it is assumed that the matrix elements of the residual interaction, obtained
after the average interaction is removed, are random with the average value of
zero. With these two assumptions one obtains explicit expressions for the mean
field and the fluctuation away from the average. The fluctuation is expanded in
terms of more and more complex excitations. Using the randomness of the matrix
elements one can then obtain formulas for the contribution to the error from
each class of complex excitations and a general condition for the convergence
of the expansion is derived. It is to be emphasized that no conditions on the
nature of the system being studied are made. Making some simplifying
assumptions a schematic model is developed. This model is applied to the
problem of nuclear matter. The model yields a measure of the strength of the
effective interaction. It turns out to be three orders of magnitude less than
that calculated using a potential which gives a binding energy of about -7
MeV/nucleon demonstrating the strong damping of the interaction strength
induced by the averaging process.


title: Hot Nuclear Matter in the Quark Meson Coupling Model

abstract:
  We study here hot nuclear matter in the quark meson coupling (QMC) model
which incorporates explicitly quark degrees of freedom, with quarks coupled to
scalar and vector mesons. The equation of state of nuclear matter including the
composite nature of the nucleons is calculated at finite temperatures. The
calculations are done taking into account the medium-dependent bag constant.
Nucleon properties at finite temperatures as calculated here are found to be
appreciably different from the value at $T=0.$


title: Nuclear aspects of the solar neutrino problem

abstract:
  The present status of the nuclear reaction rates determining the solar
neutrino flux is discussed. This includes the reaction rates for the two
branching ratios of the three pp-chains involving the reactions 3He(3He,2p)4He
and 3He(4He,gamma)7Be for the first branching, and 7Be(e-,nu_e)7Li and
7Be(p,gamma)7B for the second branching. Mainly we will concentrate on the
basic nuclear reaction p + p -> D + e+ + nu_e of the pp-chains. We use a
relativistic field theory model of the deuteron to calculate the low-energy
cross section for this reaction. The theoretical prediction of the cross
section obtained is about 2.9 times largerthan given in the conventional
potential approach. The consequences of this new reaction rate for the solar
neutrino problem will be presented and discussed.


title:
Effect of viscosity on one dimensional hydrodynamic flow and direct
  photons from 200 AGeV S+Au collisions at CERN SPS

abstract:
  We have analysed the direct photon data obtained by the WA80 collaboration in
200 A GeV S+Au collision at CERN SPS, in a one dimensional hydrodynamical
model. Two scenario was considered: (i) formation of quark-gluon plasma and
(ii) formation of hot hadronic gas. For both the scenario, ideal as well as
extremely viscous fluid was considered. It was found that direct photon yield
from QGP is not affected much whether the fluid is treated as ideal or
extremely viscous. The yield however differ substantially if hadron gas is
produced. Both the scenario do not give satisfactory description of the data.


title: Vector mesons in medium with finite three momentum

abstract:
  We formulate a QCD sum rule to find the three momentum dependence of the peak
position of the vector meson spectral density in nuclear medium. We find less
than 2 % (0.1 %) shift of the peak position at nuclear matter density and at
($q =0.5$GeV/c) for the $\rho,\omega (\phi$) mesons. However, at higher density
and three momentum, its effect becomes non-negligible. The relevance of our
result in the dilepton spectrum in A-A and p-A reaction is discussed.


title: Hartree Fock Calculations in the Density Matrix Expansion Approach

abstract:
  The density matrix expansion is used to derive a local energy density
functional for finite range interactions with a realistic meson exchange
structure. Exchange contributions are treated in a local momentum
approximation. A generalized Slater approximation is used for the density
matrix where an effective local Fermi momentum is chosen such that the next to
leading order off-diagonal term is canceled. Hartree-Fock equations are derived
incorporating the momentum structure of the underlying finite range
interaction. For applications a density dependent effective interaction is
determined from a G-matrix which is renormalized such that the saturation
properties of symmetric nuclear matter are reproduced. Intending applications
to systems far off stability special attention is paid to the low density
regime and asymmetric nuclear matter. Results are compared to predictions
obtained from Skyrme interactions. The ground state properties of stable nuclei
are well reproduced without further adjustments of parameters. The potential of
the approach is further exemplified in calculations for A=100...140 tin
isotopes. Rather extended neutron skins are found beyond 130Sn corresponding to
solid layers of neutron matter surrounding a core of normal composition.


title: AMD + HF model and its application to Be isotopes

abstract:
  In order to study light unstable nuclei systematically, we propose a new
method ''AMD + Hartree-Fock''. This method introduces the concept of the single
particle orbits into the usual AMD. Applying AMD + HF to Be isotopes, it is
found that the calculated lowest intrinsic states with plus and minus parities
have rather good correspondence with the explanation by the two-center shell
model. In addition, by active use of the single particle orbits extracted from
AMD wave function, we construct the first excited 0^+ state of $^{10}$Be. The
obtained state appears in the vicinity of the lowest 1^- state. This result is
consistent with the experimental data.


title: Hadron Formation Time and Dilepton Mass Spectra in Heavy Ion Collisions

abstract:
  We point out that formation time of pions produced in heavy ion collisions
modifies the mass spectrum of dileptons produced via pipi -> ee annihilation.
Increasing formation time enhances the production of dileptons with lower
masses. The effect offers an explanation of a part of the enhanced production
of dileptons below the rho-meson mass as observed by the CERES and HELIOS
Collaborations at the CERN SPS.


title:
Single Photons from Relativistic Heavy Ion Collisions and Quark-Hadron
  Phase Transition

abstract:
  The present status of theoretical expectations of studies of single photons
from relativistic heavy ion collisions is discussed. It is argued that the
upper limit of single photon radiation from S+Au collisions at CERN SPS
obtained by the WA80 collaboration perhaps rules out any reasonable description
of the collision process which does not involve a phase transition to quark
gluon plasma. Predictions for single photons from the quark-matter likely to be
created in collision of two lead nuclei at RHIC and LHC energies are given with
a proper accounting of chemical equilibration and transverse expansion.
Finally, it is pointed out that, contrary to the popular belief of a
quadrilateral dependence of electromagnetic radiations ($N_\gamma$) from such
collisions on the number of charged particles ($N_{ch})$, we may only have
$N_\gamma \propto N_{ch}^{1.2}$.


title:
About the determination of critical exponents related to possible phase
  transitions in nuclear fragmentation

abstract:
  We introduce a method based on the finite size scaling assumption which
allows to determine numerically the critical point and critical exponents
related to observables in an infinite system starting from the knowledge of the
observables in finite systems. We apply the method to bond percolation in 2
dimensions and compare the results obtained when the bond probability p or the
fragment multiplicity m are chosen as the relevant parameter.


title: An HFB scheme in natural orbitals

abstract:
  We present a formulation of the Hartree-Fock-Bogoliubov (HFB) equations which
solves the problem directly in the basis of natural orbitals. This provides a
very efficient scheme which is particularly suited for large scale calculations
on coordinate-space grids.


title: Boost covariant gluon distributions in large nuclei

abstract:
  It has been shown recently that there exist analytical solutions of the
Yang-Mills equations for non-Abelian Weizs\"acker-Williams fields which
describe the distribution of gluons in large nuclei at small x. These solutions
however depend on the color charge distribution at large rapidities. We here
construct a model of the color charge distribution of partons in the
fragmentation region and use it to compute the boost covariant momentum
distributions of wee gluons. The phenomenological applications of our results
are discussed.


title:
Probes for the early reaction dynamics of heavy-ion collisions at AGS
  and SPS

abstract:
  We discuss the early evolution of ultrarelativistic heavy-ion collisions
within a multi-fluid dynamical model. In particular, we show that due to the
finite mean-free path of the particles compression shock waves are smeared out
considerably as compared to the one-fluid limit. Also, the maximal energy
density of the baryons is much lower. We discuss the time scale of kinetic
equilibration of the baryons in the central region and its relevance for
directed flow. Finally, thermal emission of direct photons from the fluid of
produced particles is calculated within the three-fluid model and two other
simple expansion models. It is shown that the transverse momentum and rapidity
spectra of photons give clue to the cooling law and the early rapidity
distribution of the photon source.


title: The decay of the omega meson at finite temperature

abstract:
  The decay width of the $\omega$ meson at finite temperature is calculated
using the Gell-Mann Sharp Wagner model of $\rho$ pole dominance. Effective
masses of the $\rho$ and $\omega$ are determined within the framework of
real-time formalism of finite temperature field theory. It is shown that even
though the mass of the $\omega$-meson decreases with temperature, its decay
width increases because of an interesting interplay between the phase space
factors, the transition matrix element and Bose enhancement.


title: Soft Electromagnetic Radiations from Heavy Ion Colisions

abstract:
  The production of low mass dileptons and soft photons from thermalized Quark
Gluon Plasma (QGP) and hadronic matter in relativistic heavy ion collisions is
evaluated. A boost invariant longitudinal and cylindrically symmetric
transverse expansion of the systems created in central collision of lead nuclei
at CERN SPS, BNL RHIC, and CERN LHC, and undergoing a first order phase
transition to hadronic matter is considered. A large production of low mass
($M<$ 0.3 GeV) dileptons, and soft photons ($p_T<$ 0.4 GeV) is seen to emanate
from the bremsstrahlung of quarks and pions. We find an increase by a factor of
2--4 in the low mass dilepton and soft photon yield as we move from SPS to RHIC
energies, and an increase by an order of magnitude as we move from SPS to LHC
energies. Most of the soft radiations are found to originate from pion driven
processes at SPS and RHIC energies, while at the LHC energies the quark and the
pion driven processes contribute by a similar amount. The study of the
transverse mass distribution is seen to provide interesting details of the
evolution. We also find a unique universal behaviour for the ratio of $M^2$
weighted transverse mass distribution for $M=$ 0.1 GeV to that for $M=$ 0.2 and
0.3 GeV, as a function of $M_T$, for SPS, RHIC, and LHC energies, in the
absence of transverse expansion of the system. A deviation from this universal
behaviour is seen as a clear indication of the flow.


title:
Importance of the direct knockout mechanism in relativistic calculations
  for (gamma, p) reactions

abstract:
  Results of relativistic calculations of the direct knockout (DKO) mechanism
for the photon induced removal of a proton from a target nucleus over a wide
range of energies and nuclei are presented. Spectroscopic factors used in the
calculations are fixed from consistent analyses of the quasifree electron
scattering process (e,e'p). The results indicate that within the uncertainties
of the model, the knockout contributions are generally close to the
experimental data for missing momenta below approximately 500 MeV/c. This is in
disagreement with nonrelativistic analyses which often find that the direct
knockout contribution can be quite small compared to the data and that meson
exchange corrections can be important. The present study suggests that meson
exchange current contributions may not be as large when treated in a
relativistic framework. We also point out some difficulties we encountered in
analyzing the data for a 12C target at photon energies below 80 MeV.


title: Propagation of Charm Quarks in Equilibrating Quark Gluon Plasma

abstract:
  We study the propagation of charm quarks, produced from the initial fusion of
partons, in an equilibrating quark-gluon plasma which may be formed in the wake
of relativistic collisions of gold nuclei. Initial conditions are taken from a
self screened parton cascade model and the chemical equilibration is assumed to
proceed via gluon multiplication and quark production. The energy loss suffered
by the charm quarks is obtained by evaluating the drag force generated by the
scattering with quarks and gluons in the medium. We find that the charm quarks
may loose only about 10% of their initial energy in conditions likely to be
attained at the Relativistic Heavy Ion Collider, while they may loose up to 40%
of their energy while propagating in the plasma created at Large Hadron
Collider. We discuss the implications for signals of quark gluon plasma.


title:
Parton cascade description of relativistic heavy-ion collisions at CERN
  SPS energies ?

abstract:
  We examine Pb+Pb collisions at CERN SPS energy 158 A GeV, by employing the
earlier developed and recently refined parton-cascade/cluster-hadronization
model and its Monte Carlo implementation. This space-time model involves the
dynamical interplay of perturbative QCD parton production and evolution, with
non-perturbative parton-cluster formation and hadron production through cluster
decays. Using computer simulations, we are able to follow the entwined
time-evolution of parton and hadron degrees of freedom in both position and
momentum space, from the instant of nuclear overlap to the final yield of
particles. We present and discuss results for the multiplicity distributions,
which agree well with the measured data from the CERN SPS, including those for
K mesons. The transverse momentum distributions of the produced hadrons are
also found to be in good agreement with the preliminary data measured by the
NA49 and the WA98 collaboration for the collision of lead nuclei at the CERN
SPS. The analysis of the time evolution of transverse energy deposited in the
collision zone and the energy density suggests an existence of partonic matter
for a time of more than 5 fm.


title: Nucleon-nucleon elastic scattering analysis to 2.5 GeV

abstract:
  A partial-wave analysis of NN elastic scattering data has been completed.
This analysis covers an expanded energy range, from threshold to a laboratory
kinetic energy of 2.5 GeV, in order to include recent elastic pp scattering
data from the EDDA collaboration. The results of both single-energy and
energy-dependent analyses are described.


title:
In-medium dependence and Coulomb effects of the pion production in heavy
  ion collisions

abstract:
  The properties of the high energy pions observed in heavy ion collisions, in
particular in the system Au on Au at 1 GeV/nucleon are investigated. The
reaction dynamics is described within the Quantum Molecular Dynamics (QMD)
approach. It is shown that high energy pions freeze out early and originate
from the hot, compressed matter. $N^*$--resonances are found to give an
important contribution toward the high energy tail of the pion. Further the
role of in-medium effects in the description of charged pion yields and spectra
is investigated using a microscopic potential derived from the Brueckner
G-matrix which is obtained with the Reid soft-core potential. It is seen that
the high energy part of the spectra is relatively more suppressed due to
in-medium effects as compared to the low energy part. A comparision to
experiments further demonstrates that the present calculations describe
reasonably well the neutral (TAPS) and charged (FOPI) pion spectra. The
observed energy dependence of the $\pi^-/\pi^+$ ratio, i.e. deviations from the
isobar model prediction, is due to Coulomb effects and again indicate that high
energy pions probe the hot and dense phase of the reaction. These findings are
confirmed independently by a simple phase space analysis.


title: Lasers as a Bridge between Atomic and Nuclear Physics

abstract:
  This paper reviews the application of optical and UV laser radiation to
several topics in low-energy nuclear physics. We consider the laser-induced
nuclear anti-Stokes transitions, the laser-assisted and the laser-induced
internal conversion, and the Electron Bridge and Inverse Electron Bridge
mechanisms as tools for deexciting and exciting of low-lying nuclear isomeric
states. A study of the anomalous, by low-lying, nuclear isomeric states (on an
example of the $^{229}$Th nucleus) is presented in detail.


title: Nuclear Saturation with in-Medium Meson Exchange Interactions

abstract:
  We show that the assumption of dropping meson masses together with
conventional many-body effects, implemented in the relativistic Dirac-Brueckner
formalism, explains nuclear saturation. We use a microscopic model for
correlated $2\pi$ exchange and include the standard many-body effects on the
in-medium pion propagation, which initially increase the attractive
nucleon-nucleon ($NN$) potential with density. For the vector meson exchanges
in both the $\pi\pi$ and $NN$ sector, we assume Brown-Rho scaling which---in
concert with `chiral' $\pi\pi$ contact interactions---reduces the attraction at
higher densities.


title: Deformed Strangelets at Finite Temperature

abstract:
  Considering the confinement of massless $u$ and $d$ quarks and massive $s$
quarks in an axially symmetric quadrupole shaped deformable bag, the stability
properties of color-singlet strangelets at finite temperatures are studied for
the baryon number $A \leq$ 100. It is found that, in general, at each $A$ the
energy of the strangelet is the lowest for the spherical shape. However, it is
interesting to find shell structures for the deformed shapes at some new $A$
values, not found for the spherical shape. This should be of relevance for the
experimental search of strangelets. The color projected (singlet) calculation
shows that even for the deformed shapes the shell structures vanish only for
the temperature, $T \ga$ 30 MeV. On the other hand, from a somewhat crude
estimate we also find that at a fixed entropy per baryon (instead of a fixed
temperature) of the order of unity or higher these shell structures disappear.


title: Strange Form Factors of Baryons

abstract:
  The strange magnetic form factor of proton is calculated in a model
independent way to confirm the recent experimental result of the SAMPLE
Collaboration. We consider a set of six inertia parameters to realize the
magnetic moments of the baryon octet. We show that the strange form factor of
proton is a positive quantity, i.e. +0.37 n.m.. Its positiveness is analyzed in
terms of the vacuum fluctuation coupled to the vector current along the
strangeness direction.


title: The pd <--> pi+ t reaction around the Delta resonance

abstract:
  The pd <--> pi+ t process has been calculated in the energy region around the
Delta-resonance with elementary production/absorption mechanisms involving one
and two nucleons. The isobar degrees of freedom have been explicitly included
in the two-nucleon mechanism via pi-- and rho-exchange diagrams. No free
parameters have been employed in the analysis since all the parameters have
been fixed in previous studies on the simpler pp <--> pi+ d process. The
treatment of the few-nucleon dynamics entailed a Faddeev-based calculation of
the reaction, with continuum calculations for the initial p-d state and
accurate solutions of the three-nucleon bound-state equation. The integral
cross-section was found to be quite sensitive to the NN interaction employed
while the angular dependence showed less sensitivity. Approximately a 4% effect
was found for the one-body mechanism, for the three-nucleon dynamics in the p-d
channel, and for the inclusion of a large, possibly converged, number of
three-body partial states, indicating that these different aspects are of
comparable importance in the calculation of the spin-averaged observables.


title:
An Unified Approach To Pseudo Scalar Meson Photoproductions Off Nucleons
  In The Quark Model

abstract:
  An unified approach to the pseudo scalar meson ($\pi, \eta$, and $K$)
photoproduction off nucleons are presented. It begins with the low energy QCD
Lagrangian, and the resonances in the s- and u- channels are treated in the
framework of the quark model
  The duality hypothesis is imposed to limit the number of the t-channel
exchanges. The CGLN amplitudes for each reaction are evaluated, which include
both proton and neutron targets. The important role by the S-wave resonances in
the second resonance region is discussed, it is particularly important for the
$K, \eta$ and $\eta^\prime$ photoproductions.


title:
The piNNN--NNN problem. Connectedness, transition amplitudes and
  quasi-particle approximation

abstract:
  In this paper we review the present status of the piNNN--NNN problem. In
particular, we re-consider the chain-labelled approach recently proposed by us,
and identify a class of graphs, previously overlooked, which prevents the
kernel of the corresponding piNNN--NNN equations from being connected. We
propose some pproximate schemes, yielding connected-kernel equations. A
generalization of the residue method allows to relate the transition amplitudes
for the coupled piNNN--NNN system to the chain-labelled formalism. The
quasi-particle approach is extended to the present situation, where
emission/absorption of particles is allowed. The open problems for the
piNNN--NNN system in the light of the present and of previous approaches are
finally discussed.


title:
Initial Conditions in the One-Fluid Hydrodynamical Description of
  Ultrarelativistic Nuclear Collisions

abstract:
  We present a phenomenological model for the initial conditions needed in a
one-fluid hydrodynamical description of ultrarelativistic nuclear collisions at
CERN--SPS. The basic ingredient is the parametrization of the baryon stopping,
i.e. the rapidity distribution, as a function of the thickness of the nuclei.
We apply the model to S + S and Pb + Pb collisions and find after
hydrodynamical evolution reasonable agreement with the data.


title: Hypermatter in chiral field theory

abstract:
  We investigate the properties of hadronic matter and nuclei be means of a
generalized $SU(3)\times SU(3)$ $\sigma$ model with broken scale invariance. In
mean-field approximation, vector and scalar interactions yield a saturating
nuclear equation of state. Finite nuclei can be reasonably described, too. The
condensates and the effective baryon masses at finite baryon density and
temperature are discussed.


title:
Matrix Elements between Nuclear Compound States and Dynamical
  Enhancement of the Weak Interaction

abstract:
  A method to calculate the mean squared matrix element of weak interaction
between compound states is developed. The result is expressed in terms of
matrix elements of the nucleon-nucleon strong and weak interactions times the
Fermi distribution functions at finite temperature. Numerical calculations for
$^{233}$Th are in excellent agreement with recent measurements of parity
nonconservation effects in neutron capture. In fact, our calculations prove
that the factor of dynamical enhancement (ratio of compound-nucleus effect to
single-particle one) really exceeds 100, thus making it unnesessary to assume a
value of the weak constant bigger than standard one ($g\simeq 10^{8} \epsilon
\sim 1\div 4$).


title: QCD Scales and Chiral Symmetry in Finite Nuclei

abstract:
  We report on our progress in the calculation of nuclear ground-state
properties using effective Lagrangians whose construction is constrained by QCD
scales and chiral symmetry. Good evidence is found that QCD and chiral symmetry
apply to finite nuclei.


title:
Renormalization of the P- and T-odd nuclear potentials by the strong
  interaction and enhancement of P-odd effective field

abstract:
  Approximate analytical formulas for the self-consistent renormalization of
P,T-odd and P-odd weak nuclear potentials by the residual nucleon-nucleon
strong interaction are derived. The contact spin-flip nucleon-nucleon
interaction reduces the constant of the P,T-odd potential 1.5 times for the
proton and 1.8 times for the neutron. Renormalization of the P-odd potential is
caused by the velocity dependent spin-flip component of the strong interaction.
In the standard variant of $\pi + \rho$-exchange, the conventional strength
values lead to anomalous enhancement of the P-odd potential. Moreover, the
$\pi$-meson exchange contribution seems to be large enough to generate an
instability (pole) in the nuclear response to a weak potential.


title: Light Front Treatment of Nuclei and Deep Inelastic Scattering

abstract:
  A light front treatment of the nuclear wave function is developed and
applied, using the mean field approximation, to infinite nuclear matter. The
nuclear mesons are shown to carry about a third of the nuclear plus momentum;
but their momentum distribution has support only at for vanishingly small
values of the plus momentum, so the mesons do not contribute to nuclear deep
inelastic scattering. This zero mode effect occurs because the meson fields are
independent of space-time position.


title: Spin-Polarization Response Functions in High-Energy (e,e'p) Reactions

abstract:
  Spin-polarization response functions are examined for high-energy
$(\vec{e},e'\vec{p})$ reaction by computing the full 18 response functions for
the proton kinetic energy $T_{p'}=$ 0.515 GeV and 3.179 GeV with an 16O target.
The Dirac eikonal formalism is applied to account for the final-state
interactions. The formalism is found to yield the response functions in good
agreement with those calculated by the partial-wave expansion method at 0.515
GeV. We identify the response functions that depend on the spin-orbital
potential in the final-state interactions, but not on the central potential.
Dependence on the Dirac- or Pauli-type current of the nucleon is investigated
in the helicity-dependent response functions, and the normal-component
polarization of the knocked-out proton, $P_n$, is computed.


title: Electromagnetic Form Factors of the Nucleon in an Improved Quark Model

abstract:
  Nucleon electromagnetic form factors are studied in the cloudy bag model
(CBM) with center-of-mass and recoil corrections. This is the first
presentation of a full set of nucleon form factors using the CBM. The center of
mass motion is eliminated via several different momentum projection techniques
and the results are compared. It is found that the shapes of these form factors
are significantly improved with respect to the experimental data if the Lorentz
contraction of the internal structure of the baryon is also appropriately taken
into account.


title: On the Shell Structure of Nuclear Bubbles

abstract:
  We investigate the shell structure of spherical nuclear bubbles in simple
phenomenological shell model potentials. The shell correction energies for
doubly magic bubbles may be as large as -40 MeV and probably imply a very long
lifetime against spontaneous fission. Beta-stability occurs for ratios of the
neutron number N to the proton number Z which differ markable from the
beta-stability valley of ordinary compact nuclei. The alpha-decay probability
is shown to be very small for proton rich bubbles with a moderately large outer
radius. Metastable islands of nuclear bubbles are shown to exist for nucleon in
the range A=450 - 3000.


title: Deuteron life-time in hot and dense nuclear matter near equilibrium

abstract:
  We consider deuteron formation in hot and dense nuclear matter close to
equilibrium and evaluate the life-time of the deuteron fluctuations within the
linear response theory. To this end we derive a generalized linear Boltzmann
equation where the collision integral is related to equilibrium correlation
functions. In this framework we then utilize finite temperature Green functions
to evaluate the collision integrals. The elementary reaction cross section is
evaluated within the Faddeev approach that is suitably modified to reflect the
properties of the surrounding hot and dense matter.


title: Electromagnetic probes of dense matter in heavy-ion collisions

abstract:
  Dilepton and photon production in heavy-ion collisions at SPS energies are
studied in the relativistic transport model that incorporates self-consistently
the change of hadron masses in dense matter. It is found that the dilepton
spectra in proton-nucleus reactions can be well described by the conventional
mechanism of Dalitz decay and direct vector meson decay. However, to provide a
quantitative explanation of the observed dilepton spectra in central heavy-ion
collisions requires contributions other than these direct decays and also
various medium effects. Introducing a decrease of vector meson masses in hot
dense medium, we find that these heavy-ion data can be satisfactorily
explained. Furthermore, the single photon spectra in our calculations with
either free or in-medium meson masses do not exceed the upper bound deduced
from the experiments by the WA80 Collaboration.


title:
Measurement and analysis of neutron capture reaction rates of light
  neutron-rich nuclei

abstract:
  Several neutron capture cross sections of light neutron-rich nuclei were
measured in the astrophysically relevant energy region of 5 to 200 keV. The
experimental data are compared to calculations using the direct capture model.
The results are used for the calculation of neutron capture cross sections of
unstable isotopes. Furthermore, neutron sources with energies below E_n \approx
10 keV are discussed.


title: Chiral Lagrangian for strange hadronic matter

abstract:
  A generalized Lagrangian for the description of hadronic matter based on the
linear $SU(3)_L \times SU(3)_R$ $\sigma$-model is proposed. Besides the baryon
octet, the spin-0 and spin-1 nonets, a gluon condensate associated with broken
scale invariance is incorporated. The observed values for the vacuum masses of
the baryons and mesons are reproduced. In mean-field approximation, vector and
scalar interactions yield a saturating nuclear equation of state. We discuss
the difficulties and possibilities to construct a chiral invariant baryon-meson
interaction that leads to a realistic equation of state. It is found that a
coupling of the strange condensate to nucleons is needed to describe the
hyperon potentials correctly. The effective baryon masses and the appearance of
an abnormal phase of nearly massless nucleons at high densities are examined. A
nonlinear realization of chiral symmetry is considered, to retain a Yukawa-type
baryon-meson interaction and to establish a connection to the Walecka-model.


title:
Polarization Observables in $A(d,p)$ Breakup and Quark Degrees of
  Freedom in the Deuteron

abstract:
  The differential cross section, the tensor analyzing power, $T_{20}$, and the
polarization transfer, $\kappa_0$, in $^{12}C(d,p)$ breakup at relativistic
energy are calculated within a model which incorporates multiple scattering and
Pauli principle at quark level. It is shown that the rescattering and quark
exchange affect drastically the polarization observables for kinematical region
corresponding to high internal momentum in the deuteron.


title:
Lepton pair production in heavy ion collisions and hadronic
  phenomenology

abstract:
  We first review the calculations of low invariant mass dilepton production in
relativistic heavy ion collisions, using effective hadronic Lagrangians. We go
through some of the theoretical techniques used in this kinematical region and
we consider some of the appropriate experimental measurements. Moving up to the
intermediate invariant mass region, we point out some of the uncertainties that
show up in theoretical estimates. Those originate mainly from off-shell
effects. Finally, as an application of hadronic chiral Lagrangians at finite
temperature, we compute the mass shifts and mixing of the omega and phi mesons
due to scattering from thermal pions.


title: A (p/E) Calculation of Strong Pionic Decays of Baryons

abstract:
  Strong pionic decays of baryons are studied in a non-relativistic quark model
framework via a convergent (p/E) expansion of the transition operator. Results
are compared to the ones obtained within a more conventional (p/m) expansion.


title: Light Front Treatment of Nuclei: Formalism and Simple Applications

abstract:
  A relativistic light front treatment of nuclei is developed by performing
light front quantization for a chiral Lagrangian. The energy momentum tensor
and the appropriate Hamiltonian are obtained. Three illustrations of the
formalism are made. (1) Pion-nucleon scattering at tree level is shown to
reproduce soft pion theorems. (2) The one boson exchange treatment of
nucleon-nucleon scattering is developed and shown (by comparison with previous
results of the equal time formulation) to lead to a reasonable description of
nucleon-nucleon phase shifts. (3) The mean field approximation is applied to
infinite nuclear matter, and the plus momentum distributions of that system are
studied. The mesons are found to carry a significant fraction of the plus
momentum, but are inaccessible to experiments.


title: How to Renormalize the Schrodinger Equation

abstract:
  These lectures illustrate the key ideas of modern renormalization theory and
effective field theories in the context of simple nonrelativistic quantum
mechanics and the Schr\"odinger equation. They also discuss problems in QED,
QCD and nuclear physics for which rigorous potential models can be derived
using renormalization techniques. They end with an analysis of nucleon-nucleon
scattering based effective theory.


title: Relativistic Structure of the Nucleon Self-Energy in Asymmetric Nuclei

abstract:
  The Dirac structure of the nucleon self-energy in asymmetric nuclear matter
cannot reliably be deduced from the momentum dependence of the single-particle
energies. It is demonstrated that such attempts yield an isospin dependence
with even a wrong sign. Relativistic studies of finite nuclei have been based
on such studies of asymmetric nuclear matter. The effects of these isospin
components on the results for finite nuclei are investigated.


title:
Relativistic Hartree-Bogoliubov theory in coordinate space: finite
  element solution for a nuclear system with spherical symmetry

abstract:
  A C++ code for the solution of the relativistic Hartree-Bogoliubov theory in
coordinate space is presented. The theory describes a nucleus as a relativistic
system of baryons and mesons. The RHB model is applied in the self-consistent
mean-field approximation to the description of ground state properties of
spherical nuclei. Finite range interactions are included to describe pairing
correlations and the coupling to particle continuum states. Finite element
methods are used in the coordinate space discretization of the coupled system
of Dirac-Hartree-Bogoliubov integro-differential eigenvalue equations, and
Klein-Gordon equations for the meson fields. The bisection method is used in
the solution of the resulting generalized algebraic eigenvalue problem, and the
biconjugate gradient method for the systems of linear and nonlinear algebraic
equations, respectively.


title:
Covariant and ligth-front approaches to the rho-meson eletromagnetic
  form factors

abstract:
  The rho-meson eletromagnetic form factors are calculated, both in covariant
and light-front framework with constituintes quarks. The effect of the
breakdown rotational symmetry for the one-body current operador in the
null-plane is investigate by comparing calculations within ligth-front and
covariant approaches.


title:
The importance of initial-final state correlations for the formation of
  fragments in heavy ion collisions

abstract:
  Using quantum molecular dynamics simulations, we investigate the formation of
fragments in symmetric reactions between beam energies of E=30AMeV and 600AMeV.
After a comparison with existing data we investigate some observables relevant
to tackle equilibration: dsigma/dErat, the double differential cross section
dsigma/pt.dpz.dpt,... Apart maybe from very energetic E>400AMeV and very
central reactions, none of our simulations gives evidence that the system
passes through a state of equilibrium. Later, we address the production
mechanisms and find that, whatever the energy, nucleons finally entrained in a
fragment exhibit strong initial-final state correlations, in coordinate as well
as in momentum space. At high energy those correlations resemble the ones
obtained in the participant-spectator model. At low energy the correlations are
equally strong, but more complicated; they are a consequence of the Pauli
blocking of the nucleon-nucleon collisions, the geometry, and the excitation
energy. Studying a second set of time-dependent variables (radii,
densities,...), we investigate in details how those correlations survive the
reaction especially in central reactions where the nucleons have to pass
through the whole system. It appears that some fragments are made of nucleons
which were initially correlated, whereas others are formed by nucleons
scattered during the reaction into the vicinity of a group of previously
correlated nucleons.


title: Quark Gluon Plasma Diagnostics in a Successive Equilibrium Scenario

abstract:
  The relativistic Fokker Planck equation has been used to study the evolution
of the quark distribution in the quark gluon phase expected to be formed in
ultra-relativistic heavy ion collisions. The effect of thermal masses for
quarks and gluons is incorporated to take account of the in-medium properties.
We find that the kinetic equilibrium is achieved before the system reaches the
critical temperature of quark hadron phase transition. We find that chemical
equilibrium is not achieved during this time. We have evaluated the
electromagnetic probes of quark gluon plasma from the non-equilibrated quark
gluon phase and compared them with those in completely equilibrated scenario.
The hard QCD production rates for the electromagnetic ejectiles as well as the
heavy quark production rates are also calculated.


title: Is there a Pronounced Giant Dipole Resonance in ^4He?

abstract:
  A four-nucleon calculation of the total ^4He photodisintegration cross
section is performed. The full final-state interaction is taken into account
for the first time. This is achieved via the method of the Lorentz integral
transform. Semi-realistic NN interactions are employed. Different from the
known partial two-body ^4He(\gamma,n)^3He and ^4He(\gamma,p)^3H cross sections
our total cross section exhibits a pronounced giant resonance. Thus, in
contrast to older $(\gamma,np)$ data, we predict quite a strong contribution of
the $(\gamma,np)$ channel at the giant resonance peak energy.


title: Strangeness and Pion Production as Signals of QCD Phase Transition

abstract:
  A systematic analysis of data on strangeness and pion production in
nucleon-nucleon and central nucleus-nucleus collisions is presented. It is
shown that at all collision energies the pion/baryon and strangeness/pion
ratios indicate saturation with the size of the colliding nuclei. The energy
dependence of the saturation level suggests that the transition to the Quark
Gluon Plasma occurs between 15 AGeV/c (BNL AGS) and 160 AGeV/c (CERN SPS)
collision energies. The experimental results interpreted in the framework of a
statistical approach show that the effective number of degrees of freedom
increases in the course of the phase transition and that the plasma created at
CERN SPS energies may have a temperature of about 280 MeV (energy density 10
GeV/fm-3). The presence of the phase transition can lead to the non-monotonic
collision energy dependence of the strangeness/pion ratio. After an initial
increase the ratio should drop to the characteristic value for the QGP. Above
the transition region the ratio is expected to be collision energy independent.
Experimental studies of central Pb+Pb collisions in the energy range 20--160
AGeV/c are urgently needed in order to localize the threshold energy, and study
the properties of the QCD phase transition.


title:
Extracting the Equation of State of Nuclear Matter through
  Hydrodynamical Analysis

abstract:
  Predominantly preliminary single and double inclusive momentum spectra of 158
AGeV Pb+Pb collisions, recently measured by the NA44 and NA49 Collaborations,
are reproduced using the relativistic hydrodynamical model HYLANDER-C. Two
different equations of state, which both contain a phase transition to a
quark-gluon plasma, can be used to reproduce the (preliminary) data. The
space-time geometries in the two calculations differ strongly. However, the
Bose-Einstein correlation functions of identical pion pairs do not show such a
strong, but still a significant sensitivity to the effects of the equations of
state.


title: The multifragmentation of spectator matter

abstract:
  We present the first microscopic calculation of the spectator fragmentation
observed in heavy ion reactions at relativistic energies which reproduces the
slope of the kinetic energy spectra of the fragments as well as their
multiplicity, both measured by the ALADIN collaboration. In the past both have
been explained in thermal models, however with vastly different assumptions
about the excitation energy and the density of the system. We show that both
observables are dominated by dynamical processes and that the system does not
pass a state of thermal equilibrium. These findings question the recent
conjecture that in these collisions a phase transition of first order, similar
to that between water and vapor, can be observed.


title:
Antisymmetrization in the Multicluster Dynamic Model of Nuclei and the
  Nucleon Exchange Effects

abstract:
  A modified version of the Multicluster Dynamic Model of nuclei is proposed to
construct completely antisymmetrized wave functions of multicluster systems. An
overlap kernel operator is introduced to renormalize the total wave function
after antisymmetrization between nucleons in different clusters. A
group-theoretical method is developed to analyze the role of the exchange
effects arising in the calculation of the various observables of multicluster
systems due to this antisymmetrization.
  The Antisymmetrized version of the Multicluster Dynamic Model is applied to
the six-nucleon systems treating them as alpha-2N ones.The static and dynamic
characteristics of the six-nucleon systems manifested in electron and pi-meson
scattering, muon capture, beta-decay, pion photoproduction, etc., are
calculated.


title: Kaon Productions Off Nucleons And The Structure of Baryon Resonances

abstract:
  The recent Investigations in the chiral quark model show that kaon
productions of nucleon play an important role in understanding the structure of
baryons. The evidences of a third $S_{11}$ resonance in the second resonance
region and two narrow states around 2 GeV suggest a set of the molecular type
baryons with hidden strangeness. Confirming these states requires further
theoretical and experimental studies of the strangeness production.


title: Extended BCS Theories

abstract:
  Extensions of the Hartree-Fock-Bogoliubov theory are worked out which are
tailored for, (i) the consistent evaluation of fluctuations and correlations
and (ii) the restoration through projection of broken symmetries. For both
purposes we rely on a single variational principle which optimizes the
characteristic function. The Bloch equation is used as a constraint to define
the equilibrium state, and the trial quantities are a density operator and a
Lagrangian multiplier matrix which is akin to an observable. The conditions of
stationarity are respectively a Schr\"odinger-like equation and a Heisenberg--
like equation with an imaginary time running backwards. General conditions for
the trial spaces are stated that warrant the preservation of thermodynamic
relations. When the trial spaces are chosen to be of the
independent-quasi-particle type, the ensuing coupled equations provide an
extension of the Hartree-Fock-Bogoliubov approximation, which optimizes the
characteristic function. Variational expressions for thermodynamic quantities
or characteristic functions are also obtained with projected trial states,
whether an invariance symmetry is broken or not. In particular, the projection
on even or odd particle number is worked out for a pairing Hamiltonian, which
leads to new equations replacing the BCS ones. Qualitative differences between
even and odd systems, depending on the temperature $T$, the level density and
the strength of the pairing force, are investigated analytically and
numerically.


title: Electromagnetic Form Factors of the Nucleon

abstract:
  We reanalyze the world data on the electromagnetic form factors of the
nucleon. The calculations are performed in the framework of an algebraic model
of the nucleon combined with vector meson dominance.


title: In-medium electron-nucleon scattering

abstract:
  In-medium nucleon electromagnetic form factors are calculated in the quark
meson coupling model. The form factors are typically found to be suppressed as
the density increases. For example, at normal nuclear density and $Q^2 \sim 0.3
{ GeV}^2$, the nucleon electric form factors are reduced by approximately 8%
while the magnetic form factors are reduced by only 1 - 2%. These variations
are consistent with current experimental limits but should be tested by more
precise experiments in the near future.


title:
Multipole Expansion of Bremsstrahlung in Intermediate Energy Heavy Ion
  Collisions

abstract:
  Using a multipole expansion of the radiated field generated by a classical
electric current, we present a way to interprete the bremsstrahlung spectra of
low energy heavy ion collisions. We perform the calculation explicitely for the
system ^{12}C+ ^{12}C at 84AMeV and compare the result with the experimental
data of E. Grosse et al. Using simple model assumptions for the electromagnetic
source current we are able to describe the measured data in terms of coherent
photon emission. In this context, the information contained in the measured
data is discussed.


title: Peripheral Nucleon-Nucleon Phase Shifts and Chiral Symmetry

abstract:
  Within the one-loop approximation of baryon chiral perturbation theory we
calculate all one-pion and two-pion exchange contributions to the
nucleon-nucleon interaction. In fact we construct the elastic NN-scattering
amplitude up to and including third order in small momenta. The phase shifts
with orbital angular momentum $L\geq2 $ and the mixing angles with $J\geq2$ are
given parameterfree and thus allow for a detailed test of chiral symmetry in
the two-nucleon system. We find that for the D-waves the $2\pi$-exchange
corrections are too large as compared with empirical phase shifts, signaling
the increasing importance of shorter range effects in lower partial waves. For
higher partial waves, especially for G-waves, the model independent
$2\pi$-exchange corrections bring the chiral prediction close to empirical NN
phase shifts. We propose to use the chiral NN phase shifts with $L\geq 3$ as
input in a future phase shift analysis. Furthermore, we compute the irreducible
two-pion exchange NN-potentials in coordinate space. They turn out to be of
van-der-Waals type, with exponential screening of two-pion mass range.


title: Theoretical study of the N N --> N N pi pi reaction

abstract:
  We have developed a model for the N N --> N N pi pi reaction and evaluated
cross sections for the different charged channels. The low energy part of those
channels where the pions can be in an isospin zero state is dominated by N*
excitation, driven by an isoscalar source recently found experimentally,
followed by the decay N* --> N (pi pi, T=0, s-wave). At higher energies, and in
channels where the pions are not in T=0, Delta excitation mechanisms become
relevant. A rough agreement with the experimental data is obtained in most
channels. Repercussions of the present findings for the ABC effect and the p p
--> p p pi0 reaction close to threshold are also suggested.


title:
Role of the Coulomb interaction in the flow and the azimuthal
  distribution of kaons from heavy ion reactions

abstract:
  Coulomb final-state interaction of positive charged kaons in heavy ion
reactions and its impact on the kaon transverse flow and the kaon azimuthal
distribution are investigated within the framework of QMD (Quantum Molecular
Dynamics) model. The Coulomb interaction is found to tend to draw the flow of
kaons away from that of nucleons and lead to a more isotropic azimuthal
distribution of kaons in the target rapidity region. The recent FOPI data have
been analyzed by taking into accout both the Coulomb interaction and a kaon
in-medium potential of the strong interaction. It is found that both the
calculated kaon flows with only the Coulomb interaction and with both the
Coulomb interaction and the strong potential agree within the error bars with
the data. The kaon azimuthal distribution exhibits asymmetries of similar
magnitude in both theoretical approaches. This means, the inclusion of the
Coulomb potential makes it more difficult to extract information of the kaon
mean field potential in nuclear matter from the kaon flow and azimuthal
distribution data.


title: Baryon Number Transport in High Energy Nuclear Collisions

abstract:
  Recent SPS data on the rapidity distribution of protons in p+S, p+Au and S+S
collisions at 200 AGeV and preliminary Pb+Pb collisions at 160 AGeV are
compared to HIJING and VENUS calculations as well as to predictions based on
the Multi-Chain Model (MCM). The preliminary Pb data suggest that a linear
dependence of the proton rapidity shift as a function of the nuclear thickness,
as first observed in p+A reactions, may apply up to Pb+Pb reactions. The
observed rapidity dependence of produced hyperons in both p+A and A+A reactions
however cannot be explained in terms of such models without introducing
additional non-linear effects.


title: Nuclear Matter Properties of the Modified Quark Meson Coupling Model

abstract:
  We explore in more detail the modified quark meson coupling (MQMC) model in
nuclear matter. Based on previous studies two different functional forms for
the density dependence of the bag constant are discussed. For uniform matter
distributions the MQMC model can be cast in a form identical to QHD by a
redefinition of the sigma meson field. It is then clear that modifications
similar to those introduced in QHD will permit the reproduction of all nuclear
matter properties including the compressibility. After calibrating the model
parameters at equilibrium nuclear matter density, the model and parameter
dependence of the resulting equation of state is examined. Nucleon properties
and scaling relations between the bag constant and the effective nucleon mass
are discussed.


title: Can only flavor-nonsinglet H dibaryons be stable against strong decays?

abstract:
  Using the QCD sum rule approach, we show that the flavor-nonsinglet $H$
dibaryon states with J$^{\pi} = 1^+$, J$^{\pi} = 0^+$, I=1 (27plet) are nearly
degenerate with the J$^{\pi} = 0^+$, I=0 singlet $H_0$ dibaryon, which has been
predicted to be stable against strong decay, but has not been observed. Our
calculation, which does not require an instanton correction, suggests that the
$H_0$ is slightly heavier than these flavor-nonsinglet $H$s over a wide range
of the parameter space. If the singlet $H_0$ mass lies above the $\Lambda
\Lambda$ threshold (2231~MeV), then the strong interaction breakup to $\Lambda
\Lambda$ would produce a very broad resonance in the $\Lambda \Lambda$
invariant mass spectrum which would be very difficult to observe. On the other
hand, if these flavor-nonsinglet J=0 and 1 $H$ dibaryons are also above the
$\Lambda \Lambda$ threshold, but below the $\Xi^0n$ breakup threshold (2254
MeV), then because the direct, strong interaction decay to the $\Lambda
\Lambda$ channel is forbidden, these flavor-nonsinglet states might be more
amenable to experimental observation. The present results allow a possible
reconciliation between the reported observation of $\Lambda \Lambda$
hypernuclei, which argue against a stable $H_0$, and the possible existence of
$H$ dibaryons in general.


title: Gauging the spectator equations

abstract:
  We show how to derive relativistic, unitary, gauge invariant, and charge
conserving three-dimensional scattering equations for a system of hadrons
interacting with an electromagnetic field. In the method proposed, the
spectator equations describing the strong interactions of the hadrons are
gauged using our recently introduced gauging of equations method. A key
ingredient in our model is the on-mass-shell particle propagator. We discuss
how to gauge this on-mass-shell propagator so that both the Ward-Takahashi and
Ward identities are satisfied. We then demonstrate our gauging procedure by
deriving the gauge-invariant three-dimensional expression for the deuteron
photodisintegration amplitude within the spectator approach.


title: Gauging the three-nucleon spectator equation

abstract:
  We derive relativistic three-dimensional integral equations describing the
interaction of the three-nucleon system with an external electromagnetic field.
Our equations are unitary, gauge invariant, and they conserve charge. This has
been achieved by applying the recently introduced gauging of equations method
to the three-nucleon spectator equations where spectator nucleons are always on
mass shell. As a result, the external photon is attached to all possible places
in the strong interaction model, so that current and charge conservation are
implemented in the theoretically correct fashion. Explicit expressions are
given for the three-nucleon bound state electromagnetic current, as well as the
transition currents for the scattering processes
  \gamma He3 -> NNN, Nd -> \gamma Nd, and \gamma He3 -> Nd. As a result, a
unified covariant three-dimensional description of the NNN-\gamma NNN system is
achieved.


title:
Incompleteness of Representation Theory: Hidden symmetries and Quantum
  Non-Integrability

abstract:
  Representation theory is shown to be incomplete in terms of enumerating all
integrable limits of quantum systems. As a consequence, one can find exactly
solvable Hamiltonians which have apparently strongly broken symmetry. The
number of these hidden symmetries depends upon the realization of the
Hamiltonian.

categories: nucl-th cond-mat.stat-mech hep-th nlin.SI solv-int


title: Meson-induced correlations of nucleons in nuclear Compton scattering

abstract:
  The non-resonant (seagull) contribution to the nuclear Compton amplitude at
low energies is strongly influenced by nucleon correlations arising from meson
exchange. We study this problem in a modified Fermi gas model, where nuclear
correlation functions are obtained with the help of perturbation theory. The
dependence of the mesonic seagull amplitude on the nuclear radius is
investigated and the influence of a realistic nuclear density on this amplitude
is dicussed. We found that different form factors appear for the static part
(proportional to the enhancement constant $\kappa $) of the mesonic seagull
amplitude and for the parts, which contain the contribution from
electromagnetic polarizabilities.


title: Decay of hot, rotating, compound nuclei

abstract:
  The fusion process and the competition between fission and n, p and
alpha-particle emission is studied. The calculations are performed for nuclei
at excitation energies from 80 MeV up to about 300 MeV. The nuclear fission is
described by a Langevin equation coupled to the Master equation for particle
evaporation. A significant influence of the initial spin distribution on the
prescission particles multiplicities is found.


title: Isospin Splitting in the Pion-Nucleon Couplings from QCD Sum Rules

abstract:
  We use QCD sum rules for the three point function of a pseudoscalar and two
nucleonic currents in order to estimate the charge dependence of the pion
nucleon coupling constant coming from isospin violation in the strong
interaction. The effect can be attributed primarily to the difference of the
quark condensates <ubar u> and <dbar d>. Assuming that the pi0 is a pure
isostate we obtain for the splitting between the coupling of proton and neutron
to the neutral pion an interval of [0.008 ; 0.023], the uncertainties coming
mainly from the input parameters. In order to obtain the coupling to a physical
pi0 we have to take pi - eta mixing into account leading to an interval of
[0.012 ; 0.037]. The charged pion nucleon coupling is found to be the average
of the two neutral ones. Electromagnetic effects are not included.


title:
Kaons in dense matter, kaon production in heavy-ion collisions, and kaon
  condensation in neutron stars

abstract:
  The recent past witnesses the growing interdependence between the physics of
hadrons, the physics of relativistic heavy-ion collisions, and the physics of
compact objects in astrophysics. A notable example is the kaon which plays
special roles in all the three fields. In this paper, we first review the
various theoretical investigations of kaon properties in nuclear medium,
focusing on possible uncertainties in each model. We then present a detailed
transport model study of kaon production in heavy-ion collisions at SIS
energies. We shall discuss especially the elementary kaon and antikaon
production cross sections in hadron-hadron interactions, that represent one of
the most serious uncertainties in the transport model study of particle
production in heavy-ion collisions. The main purpose of such a study is to
constrain kaon in-medium properties from the heavy-ion data. This can provide
useful guidances for the development of theoretical models of the kaon in
medium. In the last part of the paper, we apply the kaon in-medium properties
extracted from heavy-ion data to the study of neutron star properties. Based on
a conventional equation of state of nuclear matter that can be considered as
one of the best constrained by available experimental data on finite nuclei, we
find that the maximum mass of neutron stars is about 2$M_\odot$, which is
reduced to about 1.5$M_\odot$ once kaon condensation as constrained by
heavy-ion data is introduced.


title: New Source Term for QGP Formation in the Background-Field Model

abstract:
  We consider pair production in a space-time-dependent background field and
derive a source term, i.e., production rate in the one-particle phase space.
Such a source term is required in Boltzmann-equation-based models of
quark-gluon plasma formation and evolution. We compare the source term derived
here with the one that has been used in the literature so far. Significant
differences are observed.


title: Gauging the three-nucleon system

abstract:
  We show how to attach an external photon to a system of three strongly
interacting nucleons described by three-body scattering equations. Our method
involves the idea of gauging the scattering equations themselves, and results
in electromagnetic amplitudes where the external photon is effectively coupled
to every part of every strong interaction diagram in the model. Current
conservation is therefore implemented in the theoretically correct fashion. In
this way we obtain the expressions needed to calculate all possible
electromagnetic processes of the three-nucleon system including the
electromagnetic form factors of the three-body bound state, pd -> pd gamma,
gamma He3 -> pd, gamma He3 -> ppn, etc. As the photon is coupled everywhere in
the strong interaction model, a unified description of the NNN-gamma NNN system
is obtained. An interesting aspect of our results is the natural appearance of
subtraction terms needed to avoid the overcounting of diagrams. We have also
applied the gauging of equations method to the four-dimensional description of
the piNN system which, because of the possibility of pion absorption, has
overcounting problems all of its own, and is therefore much more complicated
than the NNN case discussed here. Despite these complications, the gauging
procedure itself is very simple and leads easily to a unified description of
the piNN-gamma piNN system.


title: Fusion barrier distributions in systems with finite excitation energy

abstract:
  Eigen-channel approach to heavy-ion fusion reactions is exact only when the
excitation energy of the intrinsic motion is zero. In order to take into
account effects of finite excitation energy, we introduce an energy dependence
to weight factors in the eigen-channel approximation. Using two channel
problem, we show that the weight factors are slowly changing functions of
incident energy. This suggests that the concept of the fusion barrier
distribution still holds to a good approximation even when the excitation
energy of the intrinsic motion is finite. A transition to the adiabatic
tunneling, where the coupling leads to a static potential renormalization, is
also discussed.


title: The complex Kohn variational method applied to N-d scattering

abstract:
  The three-nucleon ground state and the N--d scattering states are obtained
using variational principles. The wave function of the system is decomposed
into angular-spin-isospin channels and the corresponding two dimensional
spatial amplitudes are expanded in a correlated polynomial basis. For the
scattering states, the complex form of the Kohn variational principle is used
to determine the $S$--matrix. Special attention is given to the convergence
pattern of the phase-shift and mixing parameters. The calculations have been
performed using realistic local NN potentials and three-nucleon forces.
Important features of the method are anomaly-free solutions and the low
dimensionality of the matrices involved allowing for the inclusion of a large
number of states. Very precise and stable numerical results have been obtained.


title: Enhanced J/psi suppression due to gluon depletion

abstract:
  The nonlinear effect of gluon depletion in the collision of large nuclei can
be large. It is due to multiple scatterings among comoving partons initiated by
primary scattering of partons in the colliding nuclei. The effect can give rise
to substantial suppression of $J/\psi$ production in very large nuclei, even if
the linear depletion effect is insignificant for the collisions of nuclei of
smaller sizes. This mechanism offers a natural explanation of the enhanced
suppression in the Pb-Pb data recently observed by NA50.


title:
The Systematics of Fundamental Particles and Unstable Nuclear Systems
  Using the Concept of Continuity and Discreteness

abstract:
  In this review, a new method is proposed based on Cantor's theory of
Cardinality to analyze the experimental data on unstable nuclear systems which
includes fundamental particles and their flavours, $\beta$-decay including spin
and parity, $\alpha$-decay and the systematics of the energy levels of light
nuclei. The method also derives a formula for the Binding Energies of unstable
nuclei. All this is based on the theory of discreteness and continuity.


title: N-d scattering above the deuteron breakup threshold

abstract:
  The complex Kohn variational principle and the (correlated) Hyperspherical
Harmonics technique are applied to study the N--d scattering above the deuteron
breakup threshold. The configuration with three outgoing nucleons is explicitly
taken into account by solving a set of differential equations with outgoing
boundary conditions. A convenient procedure is used to obtain the correct
boundary conditions at values of the hyperradius $\approx 100$ fm. The
inclusion of the Coulomb potential is straightforward and does not give
additional difficulties. Numerical results have been obtained for a simple
s-wave central potential. They are in nice agreement with the benchmarks
produced by different groups using the Faddeev technique. Comparisons are also
done with experimental elastic N--d cross section at several energies.


title:
The Equilibration of a Parton Plasma Created In Relativistic Heavy Ion
  Collisions

abstract:
  We study the equilibration of a parton plasma in terms of its parton
compositions and its state of thermalization. In studying the evolution of the
plasma, one has to assume a small value of the strong coupling constant. This
value is by no means fixed. By varying this only parameter in our calculation,
we show the dependence of equilibration on its magnitude. It is shown that both
kinetic and parton equilibration are faster with increasing coupling but the
plasma cools much more rapidly resulting in shortened lifetime. The degree of
equilibration improves significantly for quarks and antiquarks but not so for
gluons and the total generated entropy is reduced. With a coupling depending on
the average parton energy, there is additional acceleration in the
equilibration during the evolution.


title: Two-phonon background for the double giant resonance

abstract:
  The direct excitation of a "sea" of two-phonon configurations above 15 MeV
from the ground state is considered. It is concluded that these configurations
form a flat physical background in photoexcitation cross sections and Coulomb
excitation in heavy ion reactions at relativistic energies. The contribution of
the background to the total cross section in Coulomb excitation of Pb-208 in
the DGDR energy region is about 15%. This shows that It should be considered
while drawing out conclusions on anharmonicities effects for the DGDR.


title: Study of bound and scattering states in three-nucleon systems

abstract:
  A variational technique to describe the ground and scattering states below
the break-up threshold for a three-nucleon system is developed. The method
consists in expanding the wave function in terms of correlated Harmonic
Hyperspherical functions suitable to handle the large repulsion contained in
the nuclear potential at short distances; three body forces have also been
considered. The inclusion of the pp Coulomb repulsion in the p-d processes does
not cause any particular problem, since no partial wave decomposition of the
interaction is performed. Accurate numerical results are given for ground state
properties and scattering lenghts, phase shifts and mixing parameters at three
different energies of the incident nucleon. The agreement with other available
results and with experimental analyses is higlly satisfactory.


title:
Description of Nuclear Structure Effects in Subbarrier Fusion by the
  Interacting Boson Model

abstract:
  Recent theoretical developments in using the Interacting Boson Model to
describe nuclear structure effects in fusion reactions below the Coulomb
barrier are reviewed. Methods dealing with linear and all orders coupling
between the nuclear excitations and the translational motion are discussed, and
the latter is found to lead to a better description of the barrier distribution
data. A systematic study of the available data (cross sections, barrier and
spin distributions) in rare-earth nuclei is presented.


title: Dilepton Production in Relativistic Heavy Ion Collisions

abstract:
  The present status of our understanding of low mass dilepton production in
relativistic heavy ion collisions is discussed. The focus of the discussion
will be the sensitivity of dilepton measurements to in medium changes of
hadrons and the restoration of chiral symmetry. We will finally discuss how the
presence of strong long wavelength pion modes, i.e. disoriented chiral
condensates can be seen in the dilepton spectrum.


title: Thermodynamic properties of a simple, confining model

abstract:
  We study the equilibrium thermodynamics of a simple, confining, DSE-model of
2-flavour QCD at finite temperature and chemical potential. The model has two
phases: one characterised by confinement and dynamical chiral symmetry
breaking; and the other by their absence. The phase boundary is defined by the
zero of the vacuum-pressure difference between the confined and deconfined
phases. Chiral symmetry restoration and deconfinement are coincident with the
transition being of first order, except for $\mu=0$, where it is second order.
Nonperturbative modifications of the dressed-quark propagator persist into the
deconfined domain and lead to a dispersion law modified by a
dynamically-generated, momentum-dependent mass-scale. This entails that the
Stefan-Boltzmann limit for the bulk thermodynamic quantities is attained only
for large values of temperature and chemical potential.


title:
^1S_0 pairing correlations in relativistic nuclear matter and the
  two-nucleon virtual state

abstract:
  We use the Gorkov formulation of the Dirac-Hartree-Fock-Bogoliubov
approximation to nuclear pairing to study the ^1S_0 nucleon-nucleon
correlations in nuclear matter. We find the short-range correlations of the
^1S_0 pairing fields to be almost identical to those of the two-nucleon virtual
state. We obtain mutually consistent results for the pairing fields, using
several different sets of effective interaction parameters, when we demand that
each of these sets places the virtual-state pole at its physical location.


title:
Influence of final state interaction on incoherent \eta-photoproduction
  on the deuteron near threshold

abstract:
  Incoherent $\eta$-photoproduction on the deuteron is studied for photon
energies from threshold up to 720 MeV. The elementary $\gamma N \to \eta N$
amplitude is constructed in the frame of a conventional isobar model. Effects
of final state interaction are investigated and their role in the cross section
as well as in polarization observables is found to be important. Inclusion of
such effects leads to a satisfactory agreement with experimental data in the
near threshold region. In addition, recent experimental results on the coherent
reaction $d(\gamma,\eta)d$ are discussed.


title: Are There Low-Lying Intruder States in ^8Be?

abstract:
  We allow up to $4 \hbar\omega$ excitations in $^8Be$ relative to the basic
configuration $(0s)^4(0p)^4$ in order to see if there are low-lying intruder
states in $^8Be$. We use three interactions $-\chi Q \cdot Q, -\chi Q \cdot Q$
+ spin-orbit, and a realistic (x,y) interaction, where for $x=1,y=1$ one gets
values for the spin-orbit and tensor interactions which correspond closely to
those of a non-relativistic $G$ matrix such as Bonn A. For the three
interactions considered, if we allow up to $2 \hbar \omega$ excitations we get
the energy of the lowest $J=0^+$ intruder state to be at 32.1 MeV, 30.1 MeV and
33.8 MeV, respectively. If we allow up to $4 \hbar\omega$ excitations the
corresponding values are 26.5 MeV, 26.5 MeV and 28.7 MeV. We thus support the
statement made by E. Warburton in his 1986 $R$ matrix analysis of the
$\beta^{\mp}$-delayed alpha spectra from the decay of $^8Li$ and $^8B$ that
``satisfactory fits are obtained without introducing intruder states below
26-MeV excitations'' (Phys. Rev. C 33, 303(1986)). In $^{10}Be$ however, with
the first two ``$Q \cdot Q$'' interactions, we get (with up to $2 \hbar \omega$
excitations) low-lying intruder states at 9.7 MeV and 11.9 MeV respectively.
Thus the presence of low-lying intruder states in $^{10}Be$ (the $0^+_2$ state
at 6.179 MeV may or may not be an intruder) does not imply that there are
low-lying intruder states in $^8Be$.


title:
Possible solution to basic problems regarding the coupling constants
  $G_V$ and $G_A$

abstract:
  The existing experimental evidence on the vector and axial-vector coupling
constants, $G_V$ and $G_A$, for neutron $\beta$-decay exhibits two prominent
problems: (i) the unitarity for the first row of the CKM matrix seems violated;
(ii) one obtains different values of $G_A/G_V$ according to whether one uses as
input the neutron lifetime or neutron-decay correlation observables. We show
that the in-medium modification of $G_A$ can influence both the inner and outer
radiative corrections used in deducing $G_V$ from the super-allowed Fermi
transitions and that this effect may resolve the long-standing problems (i) and
(ii) simultaneously.


title: Aspects of Chiral Symmetry

abstract:
  This article is an attempt to a pedagogical introduction and review into the
elementary concepts of chiral symmetry in nuclear physics. Effective chiral
models such as the linear and nonlinear sigma model will be discussed as well
as the essential ideas of chiral perturbation theory. Some applications to the
physics of ultrarelativistic heavy ion collisions will be presented.


title: Photon production in heavy-ion collisions at SPS energies

abstract:
  Single photon spectra in heavy-ion collisions at SPS energies are studied in
the relativistic transport model that incorporates self-consistently the change
of hadron masses in dense matter. We separate the total photon spectrum into
`background' arising from the radiative decays of $\pi^0$ and $\eta$ mesons,
and the `themal' one from other sources. For the latter we include
contributions from radiative decays of $\rho$, $\omega$, $\eta'$, and $a_1$,
radiative decays of baryon resonances, as well as two-body processes such as
$\pi\pi \to \rho\gamma$ and $\pi\rho \to \pi\gamma$. It is found that more than
95% of all photons come from the decays of $\pi^0$ and $\eta$ mesons, while the
thermal photons account for less than 5% of the total photon yield. The thermal
photon spectra in our calculations with either free or in-medium meson masses
do not exceed the upper bound set by the experimental measurment of the WA80
Collaboration.


title: The Three-Nucleon System Near the N-d Threshold

abstract:
  The three-nucleon system is studied at energies a few hundred keV above the
N-d threshold. Measurements of the tensor analyzing powers $T_{20}$ and
$T_{21}$ for p-d elastic scattering at $E_{c.m.}=432$ keV are presented
together with the corresponding theoretical predictions. The calculations are
extended to very low energies since they are useful for extracting the p-d
scattering lengths from the experimental data. The interaction considered here
is the Argonne V18 potential plus the Urbana three-nucleon potential. The
calculation of the asymptotic D- to S-state ratio for $^3$H and $^3$He, for
which recent experimental results are available, is also presented.


title:
Hadron and hadron-cluster production in a hydrodynamical model including
  particle evaporation

abstract:
  We discuss the evolution of the mixed phase at RHIC and SPS within
boostinvariant hydrodynamics. In addition to the hydrodynamical expansion, we
also consider evaporation of particles off the surface of the fluid. The
back-reaction of the evaporation process on the dynamics of the fluid shortens
the lifetime of the mixed phase. In our model this lifetime of the mixed phase
is <12 fm/c in Au+Au at RHIC and <6.5 fm/c in Pb+Pb at SPS, even in the limit
of vanishing transverse expansion velocity. Strangeness separation occurs,
especially in events (or at rapidities) with relatively high initial net baryon
and strangeness number, enhancing the multiplicity of MEMOs (multiply strange
nuclear clusters). If antiquarks and antibaryons reach saturation in the course
of the pure QGP or mixed phase, we find that at RHIC the ratio of antideuterons
to deuterons may exceed 0.3 and even anti-helium to helium>0.1. Due to
fluctuations, at RHIC even negative baryon number at midrapidity is possible in
individual events, so that the antibaryon and antibaryon-cluster yields exceed
those of the corresponding baryons and clusters.


title:
Condensation of Dibaryons in Nuclear Matter and Its Possible Signatures
  in Heavy Ion Collisions

abstract:
  We consider the thermodynamics of the matter made up of equal number of
neutrons and protons and of scalar dibaryons. They interact via the exchange of
scalar and vector mesons. The interaction is taken into account in the mean
field approximation. The condensation of dibaryons in this matter and the phase
transition of matter to quark matter are considered. Possible signatures of
dibaryons in Heavy Ion Collisions are speculated on.


title:
Constraints to Coupling Constants of the Omega- and Sigma-Mesons with
  Dibaryons

abstract:
  The effect of narrow dibaryon resonances to nuclear matter and structure of
neutron stars is investigated in the mean-field theory (MFT) and in the
relativistic Hartree approximation (RHA). The existence of massive neutron
stars imposes constraints to the coupling constants of the omega- and
sigma-mesons with dibaryons. We conclude that the experimental candidates to
dibaryons d1(1920) and d'(2060) if exist form in nuclear matter a Bose
condensate stable against compression. This proves stability of the ground
state for nuclear matter with a Bose condensate of the light dibaryons.


title: Small Effects in Astrophysical Fusion Reactions

abstract:
  We study the combined effects of vacuum polarization, relativity,
Bremsstrahlung, and atomic polarization in nuclear reactions of astrophysical
interest. It is shown that these effects do not solve the longstanding
differences between the experimental data of astrophysical nuclear reactions at
very low energies and the theoretical calculations which aim to include
electron screening.


title:
Probing anharmonic properties of nuclear surface vibration by heavy-ion
  fusion reactions

abstract:
  Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O
and ^{144}Sm by the $sd-$ and $sdf-$ interacting boson model, we show that
heavy-ion fusion reactions are strongly affected by anharmonic properties of
nuclear surface vibrations and nuclear shape, and thus provide a powerful
method to study details of nuclear structure and dynamics.


title:
Importance of Non-Linear Couplings in Fusion Barrier Distributions and
  Mean Angular Momenta

abstract:
  The effects of higher order coupling of surface vibrations to the relative
motion on heavy-ion fusion reactions at near-barrier energies are investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. It is shown that the shape of fusion
barrier distributions and the energy dependence of the average angular momentum
of the compound nucleus can significantly change when the higher order
couplings are included. The role of octupole vibrational excitation of ^{16}O
in the ^{16}O + ^{144}Sm fusion reaction is also discussed using the all order
coupled-channels equations.


title:
Branching ratio change in K- absorption at rest and the nature of the
  Lambda(1405)

abstract:
  We investigate in-medium corrections to the branching ratio in K- absorption
at rest and their effect on the (positively and negatively) charged pion
spectrum. The in-medium corrections are due to Pauli blocking, which arises if
the Lambda(1405) is assumed to be a $\bar{K}$-nucleon bound state and leads to
a density and momentum dependent mass shift of the Lambda(1405). Requiring that
the optical potential as well as the branching ratio are derived from the same
elementary T-matrix, we find that the in-medium corrected, density dependent
T-matrix gives a better description of the K- absorption reaction than the
free, density-independent one. This result suggests that the dominant component
of the Lambda(1405) wave function is the $\bar{K}N$ bound state.


title: Charm Quark Production in Non-central Heavy Ion Collisions

abstract:
  The effect of gluon shadowing on charm quark production in large impact
parameter ultrarelativistic heavy ion collisions is investigated. Charm
production cross sections are calculated for a range of non-central impact
parameters which can be accurately inferred from the global transverse energy
distribution. We show that charm production is a good probe of the local parton
density which determines the effectiveness of shadowing. The spatial dependence
of shadowing can only be studied in heavy ion collisions.


title:
Fine-Tuning Two-Particle Interferometry I: Effects from Temperature
  Gradients in the Source

abstract:
  A comprehensive model study of Bose-Einstein correlation radii in heavy ion
collisions is presented. The starting point is a longitudinally and
transversally expanding fireball, represented at freeze-out by an azimuthally
symmetric emission function. The freeze-out temperature is allowed to feature
transverse and temporal gradients. Their effects on the correlation radii are
studied. In particular, we evaluate numerically their dependence on the
transverse mass of the particle pairs and check a recent suggestion, based on
analytical approximations, that for certain reasonable source parameters all
three correlation radii satisfy simultaneously a 1/\sqrt{M_\perp} scaling.


title: Modern nucleon-nucleon potentials and symmetry energy in infinite matter

abstract:
  We study the symmetry energy in infinite nuclear matter employing a
non-relativistic Brueckner-Hartree-Fock approach and using various new
nucleon-nucleon (NN) potentials, which fit np and pp scattering data very
accurately. The potential models we employ are the recent versions of the
Nijmegen group, Nijm-I, Nijm-II and Reid93, the Argonne $V_{18}$ potential and
the CD-Bonn potential. All these potentials yield a symmetry energy which
increases with density, resolving a discrepancy that existed for older NN
potentials. The origin of remaining differences is discussed.