title:
Antisymmetrized molecular dynamics with quantum branching processes for
  collisions of heavy nuclei

abstract:
  Antisymmetrized molecular dynamics (AMD) with quantum branching processes is
reformulated so that it can be applicable to the collisions of heavy nuclei
such as Au + Au multifragmentation reactions. The quantum branching process due
to the wave packet diffusion effect is treated as a random term in a
Langevin-type equation of motion, whose numerical treatment is much easier than
the method of the previous papers. Furthermore a new approximation formula,
called the triple-loop approximation, is introduced in order to evaluate the
Hamiltonian in the equation of motion with much less computation time than the
exact calculation. A calculation is performed for the Au + Au central
collisions at 150 MeV/nucleon. The result shows that AMD almost reproduces the
copious fragment formation in this reaction.


title:
Relativistic Hartree-Bogoliubov description of the deformed ground-state
  proton emitters

abstract:
  Ground-state properties of deformed proton-rich odd-Z nuclei in the region
$59 \leq Z \leq 69$ are described in the framework of Relativistic Hartree
Bogoliubov (RHB) theory. One-proton separation energies and ground-state
quadrupole deformations that result from fully self-consistent microscopic
calculations are compared with available experimental data. The model predicts
the location of the proton drip-line, the properties of proton emitters beyond
the drip-line, and provides information about the deformed single-particle
orbitals occupied by the odd valence proton.


title: Particle ratios at SPS, AGS and SIS

abstract:
  Ratios of integrated particle yields provide the best method for determining
the temperature and the chemical potential. The chemical freeze-out parameters
obtained at CERN/SPS, BNL/AGS and GSI/SIS energies all correspond to a unique
value of 1 GeV per hadron in the local rest frame of the system, independent of
the beam energy and of the target and beam particles.


title: The strong $\rho NN$ coupling derived from QCD

abstract:
  We study the two point correlation function of two nucleon currents
sandwiched between the vacuum and the rho meson state. The light cone QCD sum
rules are derived both for $\rho NN$ vector and tensor couplings
simultaneously. The contribution from the excited states and the continuum is
subtracted cleanly through the double Borel transform with respect to the two
external momenta, $p_1^2$, $p^2_2=(p-q)^2$. Our results are $g_\rho =(2.5\pm
0.2)$, $\kappa_\rho =(8.0\pm 2.0), in good agreement with the values used in
the nuclear forces.


title: The $\pi NN$ and $\pi NN(1535)$ couplings in QCD

abstract:
  The light cone QCD sum rules are derived for the $\pi NN$ coupling $g_{\pi
NN}$ and $\pi NN(1535)$ coupling $g_{\pi NN^\ast}$. The contribution from the
excited states and continuum is subtracted cleanly through double Borel
transformation. We first improve the original sum rule for $g_{\pi NN}$ and
determine the value of the pion wave function at the middle point $\phi_\pi
(u_0 ={1\over 2})=(1.5\pm 0.2)$ at $\mu =1$GeV, which is a fundamental
nonperturbative quantity like the quark condensate. Our calculation shows that
the $\pi N N(1535)$ coupling is strongly suppressed.


abstract:
  Deuteron Compton scattering below pion photoproduction threshold is
considered in the framework of the non-relativistic diagrammatic approach with
the Bonn OBE potential. The complete gauge-invariant set of diagrams is taken
into account which includes resonance diagrams without and with rescattering
and diagrams with one- and two-body seagulls. The obtained results are compared
with predictions of other models and with experimental data. A possibility of
determining isospin-averaged electromagnetic polarizabilities of the nucleon is
discussed.


title: Damping of giant resonances in asymmetric nuclear matter

abstract:
  The giant collective modes in asymmetric nuclear matter are investigated
within a dynamic relaxation time approximation. We derive a coupled dispersion
relation and show that two sources of coupling appear: (i) a coupling of
isoscalar and isovector modes due to different mean-fields acting and (ii) an
explicit new coupling in asymmetric matter due to collisional interaction. We
show that the latter one is responsible for a new mode arising besides
isovector and isoscalar modes.


title: Relativistic mean-field description of the dynamics of giant resonances

abstract:
  The relativistic mean-field theory provides a framework in which the nuclear
many-body problem is described as a self-consistent system of nucleons and
mesons. In the mean-field approximation, the self-consistent time evolution of
the nuclear system describes the dynamics of collective motion: nuclear
compressibility from monopole resonances, regular and chaotic dynamics of
isoscalar and isovector collective vibrations.


title: On isovector meson exchange currents in the Bethe-Salpeter approach

abstract:
  We investigate the nonrelativistic reduction of the Bethe-Salpeter amplitude
for the deuteron electrodisintegration near threshold energies. To this end,
two assumptions have been used in the calculations: 1) the static approximation
and 2) the one iteration approximation. Within these assumptions it is possible
to recover the nonrelativistic result including a systematic extension to
relativistic corrections. We find that the so-called pair current term can be
constructed from the $P$-wave contribution of the deuteron Bethe-Salpeter
amplitude. The form factor that enters into the calculation of the pair current
is constrained by the manifestly gauge independent matrix elements.


title:
Exotic Shapes in ^{32}S suggested by the Symmetry-Unrestricted Cranked
  Hartree-Fock Calculations

abstract:
  High-spin structure of ^{32}S is investigated by means of the cranked
Skyrme-Hartree-Fock method in the three-dimensional Cartesian-mesh
representation. Some interesting suggestions are obtained: 1) An internal
structure change (toward hyperdeformation) may occur at I>20 in the
superdeformed band, 2) A non-axial Y_{31} deformed band may appear in the yrast
line with 4<I<14.


title: omega -> pi pi decay in nuclear medium

abstract:
  We calculate the width for the omega -> pi pi decay in nuclear medium. Chiral
dynamics and low-density approximation are used. At densities around twice the
nuclear saturation density we estimate the partial width for the decay of the
longitudinal mode to be of the order of a few tens of MeV, and for the
transverse mode a few times less.


title:
Relativistic Structure of the Deuteron: 1.Electro-disintegration and
  y-scaling

abstract:
  Realistic solutions of the spinor-spinor Bethe-Salpeter equation for the
deuteron with realistic interaction kernel including the exchange of pi, sigma,
omega, rho, eta and delta mesons, are used to systematically investigate
relativistic effects in inclusive quasi-elastic electron-deuteron scattering
within the relativistic impulse approximation. Relativistic y-scaling is
considered by generalising the non relativistic scaling function to the
relativistic case, and it is shown that y-scaling does occur in the usual
relativistic scaling variable resulting from the energy conservation in the
instant form of dynamics. The present approach of y-scaling is fully covariant,
with the deuteron being described by eight components, viz. the 3S_1^{++},
3S_1^{--}, 3D_1^{++}, 3D_1^{--}, 3P_1^{+-}, 3P_1^{-+}, 1P_1^{+-}, 1P_1^{-+}
waves. It is demonstrated that if the negative relative energy states 1P_1,
3P_1 are disregarded, the concept of covariant momentum distributions N(p_0,p),
with p_0=M_D/2-\sqrt{p^2+m^2}, can be introduced, and that calculations of
lectro-disintegration cross section in terms of these distributions agree
within few percents with the exact calculations which include the 1P_1, 3P_1
states, provided the nucleon three momentum |p|\<= 1 GeV/c; in this momentum
range, the asymptotic relativistic scaling function is shown to coincide with
the longitudinal covariant momentum distribution.


title:
Low-energy scattering in four nucleon systems. Method of Cluster
  Reduction

abstract:
  A method using an expansion of the four-body Yakubovsky wave function
components onto the basis of the Faddeev-equation solutions for the two-cluster
sub-Hamiltonian eigenfunctions is exploited for computations of low-energy
scattering parameters in four nucleon systems. Results of calculations of
low-energy scattering parameters in $n-{^3}$H, $n-{^3}$He are presented.


title: Experiments with $\Xi^-$ atoms

abstract:
  Experiments with $\Xi^-$ atoms are proposed in order to study the nuclear
interaction of $\Xi$ hyperons. The production of $\Xi^-$ in the ($K^{-}$,
$K^{+}$) reaction, the $\Xi^-$ stopping in matter, and its atomic cascade are
incorporated within a realistic evaluation of the results expected for $\Xi^-$
X-ray spectra across the periodic table, using an assumed $\Xi$-nucleus optical
potential $V_{opt}$. Several optimal targets for measuring the
strong-interaction shift and width of the X-ray transition to the `last' atomic
level observed are singled out: F, Cl, I, Pb. The sensitivity of these
observables to the parameters of $V_{opt}$ is considered. The relevance of such
experiments is discussed in the context of strangeness -2 nuclear physics and
multistrange nuclear matter. Finally, with particular reference to searches for
the $H$ dibaryon, the properties of $\Xi^-d$ atoms are also discussed. The role
of Stark mixing, its effect on $S$ and $P$ state capture of $\Xi^-$ by the
deuteron, together with estimates of the resulting probability for producing
the $H$ dibaryon are considered in detail.


title: Kaon squeeze-out in heavy ion reactions

abstract:
  The squeeze-out phenomenon of $K^+$ and $K^-$ mesons, i.e. the azimuthal
asymmetry of $K^+$ and $K^-$ mesons emitted at midrapidity in heavy ion
reactions, is investigated for beam energies of 1-2 A.GeV. It is found that the
squeeze-out signal is strongly affected by in-medium potentials of these
mesons. The repulsive $K^+$-nucleus potential gives rise to a pronounced
out-of-plane emission of $K^+$'s at midrapidity. With the $K^+$ potential we
reproduce well the experimental data of the $K^+$ azimuthal distribution. It is
found that the attractive $K^-$-nucleus potential cancels to a large extent the
influence of rescattering and reabsorption of the $K^-$ mesons on the
projectile and target residuals (i.e. shadowing). This results in an
azimuthally isotropic emission of the midrapidity $K^-$ mesons with transverse
momentum up to 0.8 GeV/c. Since it is well accepted that the shadowing alone
would lead to a significant out-of-plane preference of particle emission, in
particular at high transverse momenta, the disappearance of the out-of-plane
preference for the $K^-$ mesons can serve as an unambiguous signal of the
attractive $K^-$ potential. We also apply a covariant formalism of the kaon
dynamics to the squeeze-out phenomenon. Discrepancies between the theory and
the experiments and possible solutions are discussed.


title: Fluid Dynamics for Relativistic Nuclear Collisions

abstract:
  I give an introduction to the basic concepts of fluid dynamics as applied to
the dynamical description of relativistic nuclear collisions.


title:
Restoration of the Broken D2-Symmetry in the Mean Field Description of
  Rotating Nuclei

abstract:
  Signature effects observed in rotational bands are a consequence of an
inherent D2-symmetry. This symmetry is naturally broken by the mean field
cranking approximation when a tilted (non-principal) axis orientation of the
nuclear spin becomes stable. The possible tunneling forth and back between the
two symmetry-related minima in the double-humped potential-energy surface
appears as a typical bifurcation of the rotational band. We describe this
many-body process in which all nucleons participate by diagonalizing the
nuclear Hamiltonian within a selected set of tilted and non-tilted cranking
quasiparticle states. This microscopic approach is able to restore the broken
D2 symmetry and reproduce the quantum fluctuations between symmetry- related
HFB states which emerge as splitting of the band energies and in parallel
staggering in intraband M1 transitions.


title: The Few-Body Coulombian Problem

abstract:
  Recent advances in the treatment of scattering of charged composite particles
are reviewed. In a first part I report on developments of the theory.
Specifically I describe the recent completion of the derivation of the
co-ordinate space asymptotic behaviour of the wave function for three charged
particles in the continuum. This knowledge is increasingly being made use of in
attempts to `derive' three-Coulomb particle wave functions to be used in all of
configuration space which are solutions of the Schroedinger equation, though
not everywhere but at least in one or preferably all of the asymptotic regions.
Their practical application in approximate calculations of ionisation and
breakup processes is pointed out. The asymptotic three-charged particle wave
functions find further use in investigations of asymptotic and analytic
properties of matrix elements of the three-body Coulomb resolvent. An important
example is the nonperturbative derivation, valid for all energies, of the
large-distance behaviour of the optical potential. In the second part I
describe renewed attempts to establish the few-body approach as a valuable tool
for calculating (energetic) atomic collision processes. At the end I briefly
touch upon the recent successful above-breakup-threshold calculation of
proton-deuteron elastic scattering for a realistic potential.


title: Dynamics and Instabilities of Nuclear Fermi Liquid

abstract:
  The kinetic theory of the Fermi liquid is applied to finite nuclei. The
nuclear collective motion is treated in terms of the observable variables:
particle density, current density, pressure etc. The nuclear dynamics is
influenced strongly by the Fermi-surface distortion (FSD) effect. The
relaxation of collective motion and the width of giant multipole resonances in
hot nuclei show a saturated behaviour with temperature caused by the memory
effect in the collision integral. The development of the bulk and surface
instabilities of the nuclear Fermi-liquid is sensitive to the dynamic effects
such as the FSD and the relaxation processes. The instability growth rate is
reduced due to the FSD effect and depends on the multipolarity of the particle
density and surface fluctuations.


title:
Relativistic current densities for bound spin-orbit partners and the
  longitudinal-transverse response in (e,e'p) processes

abstract:
  Scalar, baryon and vector--current densities in coordinate and momentum space
are calculated within a relativistic mean--field model. The role of the low
components of the bound nucleon wave function is investigated in detail for
different spin--orbit partner shells. We show that the relative importance of
the negative--energy projection components can be explained from the different
quantum numbers involved in the relativistic wave function. This fact has
proved to be important in the analysis of various electron scattering
observables even for low--medium values of the bound nucleon momentum.


title: Stability of the E2/M1 ratio at the T-matrix pole

abstract:
  We show how the stability of the E2/M1 ratio, evaluated at the T-matrix pole,
can be understood given a much wider variation at the K-matrix pole.


title: Not Strange but Bizarre Physics from the SAMPLE Experiment

abstract:
  Since the report of the SAMPLE Collaboration suggesting the strange-quark
contribution to nucleon magnetic moments, G_M^s(0), may be greater than zero,
numerous models have appeared supporting positive values for G_M^s(0). In this
paper the bizarre physics associated with G_M^s(0) > 0 is illustrated. Using
new lattice QCD results, our best estimate for G_M^s(0) shifts slightly from
G_M^s(0) = -0.75 +/- 0.30 mu_N, to G_M^s(0) = -0.62 +/- 0.26 mu_N.


title:
On the macroscopic limit of nuclear collective motion and its relation
  to chaotic behavior

abstract:
  In this note we concentrate on slow collective motion of isoscalar type at
small but finite excitations, as given in nuclear fission, for instance. We
report on microscopic results of transport coefficients, review how they depend
on temperature and address the interplay of one and two body viscosity. We
examine how transport properties might be influenced by chaotic behavior of
nucleonic dynamics.


title: Reaction rates from Coulomb dissociation: Core excitation effects

abstract:
  A process, involving the 7Be core excitation in the Coulomb breakup of 8B
into p + 7Be has been investigated. From the experimental results recently
obtained in RIKEN we have derived the mixing amplitude of the
  | 7Be(1/2-) X (1p_{3/2}); 2+> configuration in the ground state of 8B.
Implications on the evaluation of the S17 at stellar energies are discussed.


title: The $np \to \Lambda p$ reaction within a one-meson-exchange model

abstract:
  With the advent of high precision proton accelerators, such as COSY in
J\"ulich, or with medium energy accelerators like RCNP at Osaka, it may become
possible to perform a direct study of the strangeness changing hadronic $np \to
\Lambda p$ process. In this work we study this reaction using a
one-meson-exchange weak potential and realistic $NN$ and $YN$ strong
interactions to distort both the initial $np$ and the final $\Lambda p$ states.
The calculated cross sections are very sensitive to the different mesons
included in the weak transition, as well as to the strong $YN$ interaction
model that generates the distorted final state.


title: Production and decay of eta-mesic nuclei

abstract:
  Using the Green function method, binding effects on produced eta-mesons in
the two-stage reaction \gamma + A \to N + \eta + (A-1) \to N + (\pi N) + (A-2)
are studied. The energy spectrum of the correlated pi-N pairs which arise from
decays of etas inside the nucleus is strongly affected by an attractive
eta-nucleus optical potential. Its resonant behavior gives a clear signal of
formating intermediate eta-mesic nuclei.


title: Tensor interaction in Hartree--Fock calculations

abstract:
  The contribution of the tensor interaction in Hartree-Fock calculations for
closed shell nuclei is studied. The investigation is done neglecting the
spin-orbit component of the force. As expected from nuclear matter estimates we
find that the effect of the tensor interaction is negligible in the case of
spin-isospin saturated nuclei and also for medium and heavy nuclei with closed
shells. In light nuclei with only one of the two spin- orbit partners filled,
such as 12C and 14C, the tensor interaction plays an important role.


title: Low-mass dileptons and dropping rho meson mass

abstract:
  Using the transport model, we have studied dilepton production from heavy-ion
collisions at Bevalac energies. It is found that the enhanced production of
low-mass dileptons observed in the experiment by the DLS collaboration cannot
be explained by the dropping of hadron masses, in particular the $\rho$-meson
mass, in dense matter.


title: Pion and Kaon dissociation in hot quark medium

abstract:
  Pion and kaon dissociation in a medium of hot quark matter is studied in the
Nambu Jona-Lasinio model. The decay width of pion and kaon are found to be
large but finite at temperatures much higher than the so called critical
temperature of chiral or deconfinement transition, kaon decay width being
larger. Consequently, pions and even kaons (with a lower density compared to
pions) should coexist with quarks and gluons at such high temperatures. The
implication of the above result in the study of Quark-Gluon plasma is
discussed.


title: Isospin equilibration in relativistic heavy-ion collisions

abstract:
  We study the mixing and the kinetic equilibration of projectile and target
nucleons in relativistic heavy-ion collisions in the energy regime between
150~AMeV and 2~AGeV in a coupled-channel BUU (CBUU) approach. We find that
equilibrium in the projectile-target degrees of freedom is in general not
reached even for large systems at low energy where elastic nucleon-nucleon
collisions dominate. Inelastic nucleon excitations are more favorable for
equilibration and their relative abundance increases both with energy and mass.
Experimentally, the projectile/target admixture can be determined by measuring
the degree of isospin equilibration in isospin asymmetric nuclear collisions.
For one of the most promising systems currently under investigation,
${}^{96}_{44}{\rm Ru}+{}^{96}_{40}{\rm Zr}$, we investigate the influence of
the equation of state and the inelastic in-medium cross section.


title:
On the treatment of $NN$ interaction effects in meson production in $NN$
  collisions

abstract:
  We clarify under what circumstances the nucleon--nucleon final state
interaction fixes the energy dependence of the total cross--section for the
reaction $NN \to NNx$ close to production threshold, where $x$ can be any meson
whose interaction with the nucleon is not too strong. We strongly criticize the
procedure used recently by several authors to include the final state
interaction in the reactions under discussion. In addition, we give a formula
that allows one to estimate the effect of the initial state interaction for the
production of heavy mesons.


title: Binding energy of $\Lambda$ hypernuclei from realistic YN interactions

abstract:
  s- and p-wave $\Lambda$ single-particle enrgies are obtained for a variety of
$\Lambda$ hypernuclei from the relevant self-energy constructed within the
framework of a perturbative many-body approach. Results are presented for
present realistic hyperon-nucleon interactions such as J\"{u}lich B and
Nijmegen SC models. Effects of the non-locality and energy-dependence of the
self-energy on the bound states are investigated.


title:
Hyperfine Anomaly of Be Isotopes and Anomalous Large Anomaly in
  $^{11}$Be

abstract:
  A new result of investigations of the hyperfine structure (hfs) anomaly in Be
isotopes is presented. The hfs constant for $^{11}$Be is obtained by using the
core plus neutron type wave function: $ |2s_{1\over 2}>+|1d_{5\over2}\times 2^+
; {1/2}^{+}> $. A large hfs anomaly of $^{11}$Be is found, which is mainly due
to a large radius of the halo single particle state.


title: Spreading Width for Decay out of a Superdeformed Band

abstract:
  The attenuation factor F responsible for the decay out of a superdeformed
(SD) band is calculated with the help of a statistical model. This factor is
given by 1/F = (1 + Gamma(down) / Gamma(S)). Here, Gamma(S) is the width for
the collective E2 transition within the superdeformed band, and Gamma(down) is
the spreading width which describes the mixing between a state in the SD band
and the normally deformed (ND) states of equal spin. The attenuation factor F
is independent of the statistical E1 decay widths Gamma(N) of the ND states
provided that the Gamma(N) are much larger than both Gamma(down) and Gamma(S).
This condition is generically met. Previously measured values of F are used to
determine Gamma(down).


title: Superscaling in inclusive electron-nucleus scattering

abstract:
  We investigate the degree to which the scaling functions $F(\psi')$ derived
from cross sections for inclusive electron-nucleus quasi-elastic scattering
define the same function for different nuclei. In the region where the scaling
variable $\psi'< 0$, we find that this superscaling is experimentally realized
to a high degree.


title: Addendum to the Weak Parity-Violating Pion-Nucleon Coupling

abstract:
  We have made a needed correction to our earlier paper (nucl-th/9511002),
which contains a sign error. With this correction, the weak parity-violating
pion-nucleon coupling is about 3 x 10^(-7).


title: Chiral Symmetry and Three-Nucleon Forces

abstract:
  After a brief review of the role three-nucleon forces play in the few-nucleon
systems, the chiral-perturbation-theory approach to these forces is discussed.
Construction of the (nominal) leading- and subleading-order Born terms and
pion-rescattering graphs contributing to two-pion-exchange three-nucleon forces
is reviewed, and comparisons are made of the types of such forces that are used
today. It is demonstrated that the short-range $c$-term of the Tucson-Melbourne
force is unnatural in terms of power counting and should be dropped. The class
of two-pion-exchange three-nucleon forces then becomes rather uniform.


title:
Microscopic Nuclear Level Densities from Fe to Ge by the Shell Model
  Monte Carlo Method

abstract:
  We calculate microscopically total and parity-projected level densities for
$\beta$-stable even-even nuclei between Fe and Ge, using the shell model Monte
Carlo methods in the complete $(pf+0g_{9/2})$-shell. A single-particle level
density parameter $a$ and backshift parameter $\Delta$ are extracted by fitting
the calculated densities to a backshifted Bethe formula, and their systematics
are studied across the region. Shell effects are observed in $\Delta$ for
nuclei with Z=28 or N=28 and in the behavior of $A/a$ as a function of the
number of neutrons. We find a significant parity-dependence of the level
densities for nuclei with $A \alt 60$, which diminishes as $A$ increases.


title:
Invariant amplitudes for coherent electromagnetic pseudoscalar
  production from a spin-one target

abstract:
  A set of 13 linearly independent invariant amplitudes for the electromagnetic
production of a pseudoscalar particle from a spin-one particle is derived which
respect Lorentz and gauge invariance. The $T$-matrix can be represented by a
linear superposition of these amplitudes with invariant functions as
coefficients, which depend on the Mandelstam variables only. Their explicit
form is determined by the underlying dynamics. Nine of these amplitudes are
purely transverse and describe photoproduction. The remaining four appear in
electroproduction in addition, describing charge and longitudinal current
contributions. Furthermore, a reduction of these amplitudes to operators acting
in non-relativistic spin space is given.


title:
Full $0\hbar\omega$ shell model calculation of the binding energies of
  the $1f_{7/2}$ nuclei

abstract:
  Binding energies and other global properties of nuclei in the middle of the
$pf$ shell, such as M1, E2 and Gamow-Teller sum rules, have been obtained using
a new Shell Model code (NATHAN) written in quasi-spin formalism and using a
$j-j$-coupled basis. An extensive comparison is made with the recently
available Shell Model Monte Carlo results using the effective interaction KB3.
The binding energies for -nearly- all the $1f_{7/2}$ nuclei are compared with
the measured (and extrapolated) results.


title: Nuclear Forces and Nuclear Structure

abstract:
  After a historical review, I present the progress in the field of realistic
NN potentials that we have seen in recent years. A new generation of very
quantitative (high-quality/high-precision) NN potentials has emerged. These
potentials will serve as reliable input for microscopic nuclear structure
calculations and will allow for a systematic investigation of off-shell
effects. The issue of three-nucleon forces is also discussed.


title: Bose-Einstein Correlations and the Equation of State of Nuclear Matter

abstract:
  Within a relativistic hydrodynamic framework, we use four different equations
of state of nuclear matter to compare to experimental spectra from CERN/SPS
experiments NA44 and NA49. Freeze-out hypersurfaces and Bose-Einstein
correlation functions for identical pion pairs are discussed. We find that
two-pion Bose-Einstein interferometry measures the relationship between the
temperature and the energy density in the equation of state during the late
hadronic stage of the fireball expansion. Little sensitivity of the
light-hadron data to a quark-gluon plasma phase-transition is seen.


title: A momentum subtraction scheme for two--nucleon effective field theory

abstract:
  We introduce a momentum subtraction scheme which obeys the power counting of
Kaplan, Savage, and Wise (KSW), developed for systems with large scattering
lengths, $a$. Unlike the power divergence subtraction scheme, coupling
constants in this scheme obey the KSW scaling for all $\mu_R > 1/a$. We comment
on the low-energy theorems derived by Cohen and Hansen. We conclude that there
is no obstruction to using perturbative pions for momenta $p>m_\pi$.


title:
Surface properties in a relativistic mean field approach with
  vector-vector and scalar-vector self-interactions

abstract:
  Nuclear matter and surface properties are carefully studied for a model based
on an effective hadronic lagrangian with vector-vector and scalar-vector
self-interactions. The results of the model are compared with those of the
successful standard non-linear $\sigma-\omega$ model.


title: Low density instability in a nuclear Fermi liquid drop

abstract:
  The instability of a Fermi-liquid drop with respect to bulk density
distortions is considered. It is shown that the presence of the surface
strongly reduces the growth rate of the bulk instability of the finite
Fermi-liquid drop because of the anomalous dispersion term in the dispersion
relation. The instability growth rate is reduced due to the Fermi surface
distortions and the relaxation processes. The dependence of the bulk
instability on the multipolarity of the particle density fluctuations is
demonstrated for two nuclei $^{40}Ca$ and $^{208}Pb$.


title:
A comparative study of super- and highly-deformed bands in the A ~ 60
  mass region

abstract:
  Super- and highly-deformed rotational bands in the A ~ 60 mass region are
studied within cranked relativistic mean field theory and the
configuration-dependent shell-correction approach based on the cranked Nilsson
potential. Both approaches describe the experimental data well. Low values of
the dynamic moments of inertia J^(2) compared with the kinematic moments of
inertia J^(1) seen both in experiment and in calculations at high rotational
frequencies indicate the high energy cost to build the states at high spin and
reflect the limited angular momentum content in these configurations.


title:
Computing probabilities of very rare events for Langevin processes: a
  new method based on importance sampling

abstract:
  Langevin equations are used to model many processes of physical interest,
including low-energy nuclear collisions. In this paper we develop a general
method for computing probabilities of very rare events (e.g. small fusion
cross-sections) for processes described by Langevin dynamics. As we demonstrate
with numerical examples as well as an exactly solvable model, our method can
converge to the desired answer at a rate which is orders of magnitude faster
than that achieved with direct simulations of the process in question.


title:
Relationships between two--particle overlap functions and the two--body
  density matrix for many-fermion systems

abstract:
  Relationships are obtained connecting the two-nucleon overlap function of the
eigenstates in the (A-2) particle system with the asymptotic behavior of the
two-body density matrix for the ground state of the A-particle system.This
makes it possible to calculate the two-body overlap functions, spectroscopic
factors and separation energies on the basis of a realistic two-body density
matrix. The procedure can be used in describing the (e,e'NN) and (\gamma, NN)
reactions where the two--body overlap functions are a key ingredient in the
analysis.


title:
Emission times and opacities from interferometry in non-central
  Relativistic Nuclear Collisions

abstract:
  The nuclear overlap zone in non-central relativistic heavy ion collisions is
azimuthally very asymmetric. By varying the angle between the axes of
deformation and the transverse direction of the pair momenta, the transverse
HBT radii oscillate in a characteristic way. It is shown that these
oscillations allow determination of source sizes, deformations as well as the
opacity and duration of emission of the source created in any non-central high
energy nuclear collisions. The behavior of the physical quantities with
centrality of the collisions is discussed --- in particular changes caused by a
possible phase transition to a quark-gluon plasma.


title: Nucleation Process in Asymmetric Nuclear Matter

abstract:
  An extended version of the non linear Walecka model, with rho mesons and
eletromagnetic field is used to investigate the possibility of phase
transitions in hot (warm) nuclear matter, giving rise to droplet formation.
Surface properties of asymmetric nuclear matter as the droplet surface energy
and its thickness are also examined.


title: Nuclear liquid-gas phase transition within the lattice gas model

abstract:
  We study the nuclear liquid-gas phase transition on the basis of a
two-component lattice gas model. A Metropolis type of sampling method is used
to generate microscopic states in the canonical ensemble. The effective
equation of state and fragment mass distributions are evaluated in a wide range
of temperatures and densities. A definition of the phase coexistence region
appropriate for mesoscopic systems is proposed. The caloric curve resulting
from different types of freeze-out conditions are presented.


title: Dynamics of dissipative binary collisions

abstract:
  In this paper we discuss the reaction mechanisms that occur in the overlap
zone for semi-peripheral heavy ion collisions at intermediate energies. In
particular we focus on the development of neck instabilities, that could
determine a possible increase of dynamical fluctuations. As observed in recent
experimental data, at beam energies just above 10 MeV/A the most relevant
expected consequence is the possibility to obtain large variances in the
projectile-like and target-like observables. With increasing beam energy we
pass to a mid-rapidity fragment production. In this way we predict a smooth
transition from a deep-inelastic to a fragmentation reaction mechanism.


title: Supernova electron capture rates for 55Co and 56Ni

abstract:
  We have calculated the Gamow-Teller strength distributions for the ground
states and first excited states in 55Co and 56Ni. These calculations have been
performed by shell model diagonalization in the pf shell using the KB3
interaction. The Gamow-Teller distributions are used to calculate the electron
capture rates for typical presupernova conditions. Our 55Co rate is noticeably
smaller than the presently adopted rate as it is dominated by weak low-lying
transitions rather than the strong Gamow-Teller (GT) resonance which is located
at a higher excitation energy in the daughter than usually parametrized.
Although our 56Ni rate agrees with the presently adopted rate, we do not
confirm the conventional parametrization of the GT centroid. Our results
support general trends suggested on the basis of shell model Monte Carlo
calculations.


title: Supernova electron capture rates on odd-odd nuclei

abstract:
  At densities between 10^8 and 10^10} g/cm^3 electron capture in a
presupernova collapse is believed to mainly occur on odd-odd nuclei. We have
derived the rates for six of the most important electron capturing nuclei,
{54,56,58}Mn and {56,58,60}Co, based on calculations of the Gamow-Teller
strength distributions for the ground states and first excited states. These
calculations have been performed by shell model diagonalization in the pf shell
using a recently modified version of the KB3 interaction. The shell model rates
are noticeably smaller than the presently adopted rates as the latter have been
derived by placing the Gamow-Teller (GT) resonance at too low excitation
energies.


title:
Subbarrier heavy ion fusion enhanced by nucleon transfer and subbarrier
  fusion of nuclei far from the line of \beta-stability

abstract:
  We discuss a model for the description of subbarrier fusion of heavy ions
which takes into account the coupling to the low-energy surface vibrational
states and to the few-nucleon transfer with arbitrary reaction Q-value. The
fusion reactions ^{28,30}Si+^{58,62,64}Ni, ^{40}Ca+^{90,96}Zr,
^{28}S+^{94,100}Mo, ^{16,18,20,22,24}O+^{58}Ni and
^{28}Si+^{124,126,128,130,132}Sn are analyzed in detail. The model describes
rather well the experimental fusion cross section and mean angular momentum for
reactions between nuclei near the \beta-stability line. It is shown that these
quantities are significantly enhanced by few-nucleon transfer with large
positive Q-value. A shape independent parameterization of the heavy ion
potential at distances smaller then the touching point is proposed.


title: Effective theory for the two-nucleon system

abstract:
  We apply the method of unitary transformations to a model two-nucleon
potential and construct from it an effective potential in a subspace of momenta
below a given cut-off $\Lambda$. The S-matrices in the full space and in the
subspace are shown to be identical. We solve numerically the Schr\"odinger
equation in the small momentum space and recover exactly the bound and
scattering states of the full theory. We then expand the heavy repulsive meson
exchange of the effective potential in a series of local contact terms and
discuss the question of naturalness of the corresponding coupling constants.
Using our exact effective theory we address further issues related to the
chiral perturbation theory approach of the two-nucleon system. The coordinate
space representation of the effective potential is also considered.


title: Determination of the forward Compton scattering amplitudes for C and Pb

abstract:
  The forward Compton scattering amplitude for carbon and lead have been
calculated from total photoabsorption cross section data by using dispersion
relations. The results show a large difference between the scattering
amplitudes for nuclei and the free nucleon, above the $\Delta $ region. The
forward Compton scattering cross sections have been calculated and compared
with the available data. The Weise sum rule is discussed together with the
prediction of a recent theoretical model.


title: On the Origin of Nuclear Superfluidity

abstract:
  The induced pairing interaction arising from the exchange of collective
surface vibrations among nucleons moving in time reversal states close to the
Fermi energy is found to lead to values of the pairing gap which are similar to
those experimentally observed.


title: The current status of Vud

abstract:
  The value of the $V_{ud}$ matrix element of the Cabibbo-Kobayashi-Maskawa
(CKM) matrix can be derived from nuclear superallowed beta decays, neutron
decay, and pion beta decay. We survey current world data for all three. Today,
the most precise value of $V_{ud}$ comes from the nuclear decays; however, the
precision is limited not by experimental error but by the estimated uncertainty
in theoretical corrections. The neutron data are approximately a factor of four
poorer in precision but this could change dramatically in the near future as
planned experiments come to fruition. The nuclear result (and the most recent
of the neutron decay results) differ at the 98% confidence level from the
unitarity condition for the CKM matrix. We examine the reliability of the small
calculated corrections that have been applied to the data, and assess the
likelihood of even higher quality nuclear data becoming available to confirm or
deny the discrepancy. Some of the required experiments depend upon the
availability of intense radioactive beams. Others are possible today.


title:
Scaling Of Chiral Lagrangians And Landau Fermi Liquid Theory For Dense
  Hadronic Matter

abstract:
  We discuss the Fermi-liquid properties of hadronic matter derived from a
chiral Lagrangian field theory in which Brown-Rho (BR) scaling is incorporated.
We identify the BR scaling as a contribution to Landau's Fermi liquid
fixed-point quasiparticle parameter from "heavy" isoscalar meson degrees of
freedom that are integrated out from a low-energy effective Lagrangian. We show
that for the vector (convection) current, the result obtained in the chiral
Lagrangian approach agrees precisely with that obtained in the
semi-phenomenological Landau-Migdal approach. This precise agreement allows one
to determine the Landau parameter that enters in the effective nucleon mass in
terms of the constant that characterizes BR scaling. When applied to the weak
axial current, however, these two approaches differ in a subtle way. While the
difference is small numerically, the chiral Lagrangian approach implements
current algebra and low-energy theorems associated with the axial response that
the Landau method misses and hence is expected to be more predictive.


title: Wigner energy, odd-even mass staggering and the time-odd mean-fields

abstract:
  Various properties of single-particle Hartree-Fock ground-state solutions in
$N\sim Z$ nuclei are investigated. The emphasis is on a role of single-particle
mean-field in odd-even mass staggering. It is shown that, unlike in traditional
scenario originating from the Fermi gas or macroscopic models, the symmetry
energy contribution to odd-even mass staggering is nearly cancelled by the
contribution coming from the average level density. It allows to construct
indicators probing both pairing as well as mean-field components to the
odd-even mass staggering. The impact of the single-particle Hartree-Fock field
on Wigner energy and residual $pn$ interaction in odd-odd nuclei is also
discussed.


title: Channel Coupling in $A(\vec{e},e' \vec{N})B$ Reactions

abstract:
  The sensitivity of momentum distributions, recoil polarization observables,
and response functions for nucleon knockout by polarized electrons to channel
coupling in final-state interactions is investigated using a model in which
both the distorting and the coupling potentials are constructed by folding
density-dependent effective interactions with nuclear transition densities.
Calculations for $^{16}$O are presented for 200 and 433 MeV ejectile energies,
corresponding to proposed experiments at MAMI and TJNAF, and for $^{12}$C at 70
and 270 MeV, corresponding to experiments at NIKHEF and MIT-Bates. The relative
importance of charge exchange decreases as the ejectile energy increases, but
remains significant for 200 MeV. Both proton and neutron knockout cross
sections for large recoil momenta, $p_m > 300$ MeV/c, are substantially
affected by inelastic couplings even at 433 MeV. Significant effects on the
cross section for neutron knockout are also predicted at smaller recoil
momenta, especially for low energies. Polarization transfer for proton knockout
is insensitive to channel coupling, even for fairly low ejectile energies, but
polarization transfer for neutron knockout retains nonnegligible sensitivity to
channel coupling for energies up to about 200 MeV. The present results suggest
that possible medium modifications of neutron and proton electromagnetic form
factors for $Q^2 \gtrsim 0.5 (GeV/c)^2$ can be studied using recoil
polarization with relatively little sensitivity due to final state
interactions.


title:
Light-Baryon Spectroscopy and the Electromagnetic Form Factors in the
  Quark Model

abstract:
  The momentum distributions of the constituent quarks inside the nucleon and
the prominent electroproduced nucleon resonances are investigated in the two
most sophisticated, available quark potential models, based respectively on the
assumption of the valence + gluon dominance and on the exchange of the
pseudoscalar Goldstone-bosons arising from the spontaneous breaking of chiral
symmetry. It is shown that both models predict a large, similar content of
high-momentum components, due to the short-range part of the interquark
interaction, which affect the behaviour of both elastic and transition
electromagnetic form factors at large values of the momentum transfer. The
electromagnetic form factors are calculated within a relativistic approach
formulated on the light-front, adopting a one-body current with constituent
quark form factors. The results suggest that soft, non-perturbative effects can
play a relevant role for explaining the existing data on elastic as well as
transition form factors (at least) for Q**2 ~ 10 - 20 (GeV/c)**2.


title: Coalescence and flow in ultra-relativistic heavy ion collisions

abstract:
  Using a density matrix approach to describe the process of coalescence, we
calculate the coalescence probabilities and invariant momentum spectra for
deuterons and antideuterons. We evaluate our expressions with a
hydrodynamically motivated parametrization for the source at freeze-out which
implements rapid collective expansion of the collision zone formed in heavy ion
collisions. We find that the coalescence process is governed by the same
lengths of homogeneity which can be extracted from HBT interferometry. They
appear in the absolute cluster yield via an effective volume factor as well as
in a quantum mechanical correction factor which accounts for the internal
structure of the deuteron cluster. Our analysis provides a new interpretation
for the parameters in the popular phenomenological coalescence model and for
the effective overlap volume in Hagedorn's model for cluster production in pp
collisions. Using source parameters extracted from a recent HBT analysis of
two-pion correlations, we successfully describe deuteron and antideuteron
production data from Pb+Pb collisions at the CERN SPS as measured by the NA44
and NA52 collaborations. We also confirm the recent finding by Polleri et al.
that the different measured slopes of nucleon and deuteron transverse mass
spectra require a transverse density profile of the source which is closer to a
box than to a Gaussian shape.


title: NN Interactions in QCD: Old and New Techniques

abstract:
  Since QCD is believed to be the underlying theory of the strong interaction,
it is appropriate to study techniques that take into account more features of
its rich and complex structure. We begin by discussing aspects of physics that
are ill-reproduced by the usual one- or two-meson exchange approaches and
identify the source of the deficiencies of these models. We then reveal
promising methods for curing some of these ills, such as new quark potential
models, baryon chiral perturbation theory, soluble strongly-interacting field
theories, and large N_c QCD.


title: Impressionism and Surrealism in Multiparticle Dynamics

abstract:
  Invited talk at the CORR98 meeting on Correlations, M\'atrah\'aza, June 1998,
to appear in the proceedings of the meeting in World Scientific. This talk is
dedicated to the memory of Peter Carruthers.


title:
Renormalization schemes and the range of two-nucleon effective field
  theory

abstract:
  The OS and PDS renormalization schemes for the effective field theory with
nucleons and pions are investigated. We explain in detail how the
renormalization is implemented using local counterterms. Fits to the NN
scattering data are performed in the 1S0 and 3S1 channels for different values
of mu_R. An error analysis indicates that the range of the theory with
perturbative pions is consistent with 500 MeV.


title: Production of e+e- pairs in proton-deuteron capture to 3He

abstract:
  The process p+d \leftrightarrow 3He + \gamma* at intermediate energies is
described using a covariant and gauge-invariant model, and a realistic pd3He
vertex. Both photodisintegration of 3He and proton-deuteron capture with
production of e+e- pairs are studied, and results for cross sections and
response functions are presented. The effect of time-like formfactors on the
dilepton cross sections is investigated as well.


title:
Two Pion Production in Nucleon-Nucleon Collisions at Intermediate
  Energies

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 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.


title:
Symmetric and asymmetric nuclear matter in the Thomas-Fermi model at
  finite temperatures

abstract:
  The properties of warm symmetric and asymmetric nuclear matter are
investigated in the frame of the Thomas-Fermi approximation using a recent
modern parametrization of the effective nucleon-nucleon interaction of Myers
and Swiatecki. Special attention is paid to the liquid-gas phase transition,
which is of special interest in modern nuclear physics. We have determined the
critical temperature, critical density and the so-called flash temperature.
Furthermore the equation of state for cold neutron star matter was calculated.


title:
Expansion and evaporation of hot nuclei: Comparison between
  semi-classical and quantal mean-field approaches

abstract:
  We present a general discussion of the mean field dynamics of finite nuclei
prepared under extreme conditions of temperature and pressure. We compare the
prediction of semi-classical approximation with complete quantum simulations.
Many features of the dynamics are carefully studied such as the collective
expansion, the evaporation process, the different time-scale... This study
points out many quantitative differences between quantum and semi-classical
approaches. Part of the differences are related to numerical features inherent
in semi-classical simulations but most of them are a direct consequence of the
non treatment of nuclei as quantal objects. In particular, we show that because
of a too strong damping in semi-classical approaches the expansion of hot
nuclei is quenched and the speed of the collective motion reduced.


title: Giant Octupole Resonance Simulation

abstract:
  Using a pseudo-particle technique we simulate large-amplitude isoscalar giant
octupole excitations in a finite nuclear system. Dependent on the initial
conditions we observe either clear octupole modes or over-damped octupole modes
which decay immediately into quadrupole ones. This shows clearly a behavior
beyond linear response. We propose that octupole modes might be observed in
central collisions of heavy ions.


title:
Formation and Decay of Chiral Condensates in Relativistic Heavy Ion
  Collisions

abstract:
  We discuss the various physics aspects of hypothetical, coherent excitations
of the pion field caused by spontaneously generated local distortions of the
chiral order parameter. Such distortions, which may occur in the expansion of a
hot fireball created in relativistic nuclear collisions, may be influenced or
even triggered by the interaction with strong electromagnetic fields through
the axial anomaly. We suggest that semiperipheral collisions may provide the
best environment for the formation of these disoriented chiral condensates.


title:
Enhancement of $\pi A \to \pi\pi A$ Threshold Cross Sections by
  In-Medium $\pi\pi$ Final State Interactions

abstract:
  We address the problem of pion production in low energy $\pi$-nucleus
collisions. For the production mechanism we assume a simple model consisting of
a coherent sum of single pion exchange and the excitation---followed by the
decay into two pions and a nucleon---of the $N^*(1440)$ resonance. The
production amplitude is modified by the final state interaction between the
pions calculated using the chirally improved J\"ulich meson exchange model
including the polarization of the nuclear medium by the pions. The model
reproduces well the experimentally observed $\pi A \to \pi\pi A$ cross
sections, especially the enhancement with increasing $A$ of the $\pi^+\pi^-$
mass distribution in the threshold region.


title: Multifragmentation in Xe(50A MeV)+Sn Confrontation of theory and data

abstract:
  We compare in detail central collisions Xe(50A MeV) + Sn, recently measured
by the INDRA collaboration, with the Quantum Molecular Dynamics (QMD) model in
order to identify the reaction mechanism which leads to multifragmentation. We
find that QMD describes the data quite well, in the projectile/target region as
well as in the midrapidity zone where also statistical models can be and have
been employed. The agreement between QMD and data allows to use this dynamical
model to investigate the reaction in detail. We arrive at the following
observations: a) the in medium nucleon nucleon cross section is not
significantly different from the free cross section, b) even the most central
collisions have a binary character, c) most of the fragments are produced in
the central collisions and d) the simulations as well as the data show a strong
attractive in-plane flow resembling deep inelastic collisions e) at midrapidity
the results from QMD and those from statistical model calculations agree for
almost all observables with the exception of ${d^2 \sigma \over dZdE}$. This
renders it difficult to extract the reaction mechanism from midrapidity
fragments only. According to the simulations the reaction shows a very early
formation of fragments, even in central collisions, which pass through the
reaction zone without being destroyed. The final transverse momentum of the
fragments is very close to the initial one and due to the Fermi motion. A
heating up of the systems is not observed and hence a thermal origin of the
spectra cannot be confirmed.


title: Configuration Mixing Effects in Isoscalar Giant Dipole Resonance

abstract:
  Based on an explicit verification of the coupling matrix elements between the
1p1h and 2p2h states we propose a new method of selecting the most important
2p2h states responsible for fragmentation effects. In this way the
dimensionality of the problem is reduced, such that the computation becomes
feasible and the spreading of the strength is realistic, as verified by some
tests of convergence. Calculations in $^{208}$Pb show that due to sizable
mixing effects only about 50% of the total isoscalar giant dipole resonance
(ISGDR) $3\hbar\omega$ strength is located in the energy region between 20 and
25 MeV. This is the energy region which currently is available in experiment.
Even above 30 MeV we find about 10% of the total strength. This indicates that
the current experimantal evaluations of the ISGDR centroid energy may
significantly underestimate its value.


title: Heavy Meson Observables and Dyson-Schwinger Equations

abstract:
  Dyson-Schwinger equation (DSE) studies show that the b-quark mass-function is
approximately constant, and that this is true to a lesser extent for the
c-quark. These observations provide the basis for a study of the leptonic and
semileptonic decays of heavy pseudoscalar mesons using a ``heavy-quark'' limit
of the DSEs. When exact, this limit reduces the number of independent form
factors. Semileptonic decays with light mesons in the final state are also
accessible because the DSEs provide a description of light-quark propagation
characteristics and light-meson structure. A description of B-meson decays is
straightforward, however, the study of decays involving the D-meson indicates
that c-quark mass-corrections are quantitatively important.


title: Relativistic mean-field description of nuclei at the drip lines

abstract:
  We present a review of recent applications of the relativistic mean-field
theory to the structure of nuclei close to the drip-lines. For systems with
extreme isospin values, the relativistic Hartree-Bogoliubov model provides a
unified and self-consistent description of mean-field and pairing correlations.
The model has been applied in studies of structure phenomena that include:
formation of neutron skin and of neutron halos in light nuclei in the mass
region above the s-d neutron shell, the strong isospin dependence of the
effective spin-orbit interaction and the resulting modification of surface
properties, the suppression of the spherical N=28 shell gap for neutron-rich
nuclei and the related phenomenon of deformation and shape coexistence, the
proton drip-line in the spherical nuclei $14\leq Z \leq 28$, and ground-state
proton radioactivity in the region of deformed nuclei $59 \leq Z \leq 69$.


title:
Dimensional versus cut-off renormalization and the nucleon-nucleon
  interaction

abstract:
  The role of dimensional regularization is discussed and compared with that of
cut-off regularization in some quantum mechanical problems with ultraviolet
divergence in two and three dimensions with special emphasis on the
nucleon-nucleon interaction. Both types of renormalizations are performed for
attractive divergent one- and two-term separable potentials, a divergent tensor
potential, and the sum of a delta function and its derivatives. We allow
energy-dependent couplings, and determine the form that these couplings should
take if equivalence between the two regularization schemes is to be enforced.
We also perform renormalization of an attractive separable potential superposed
on an analytic divergent potential.


title: The E2/M1 Ratio, a Status Report

abstract:
  Recent determinations of the E2/M1 ratio are reviewed. Many aspects of these
studies have been questioned. Here we focus on the selection of a database,
methods used in the extraction of this ratio, and interpretation(s) of the
results.


title: KbarN interaction and Kaons in the nuclear medium

abstract:
  The s-wave meson-nucleon interaction in the S=-1 sector is studied by means
of a coupled-channel Lippmann Schwinger equation, using the lowest order chiral
Lagrangian and a cut off to regularize the loop integrals. The position and
width of the Lambda(1405) resonance and the K^- p scattering cross sections at
low energies are well reproduced. The inclusion of the eta Lambda, eta Sigma^0
channels in the coupled system is found very important and allows a solution in
terms of only the lowest order Lagrangian. The model is applied to calculate
the in-medium K^- self-energy to which we add a small p-wave piece resulting
from the coupling to hyperon particle-nucleon hole excitations. The K^- feels
an attraction of about -100 MeV at normal nuclear density. The Lambda(1405)
resonance shifts to energies above the $K^-p$ threshold and ends up dissolving
as density increases. It remains to be seen how these effects persist when the
dressing of the Kbar and the pi mesons is incorporated self-consistently in the
calculation.


title:
Effective field theory approaches to pion production in proton-proton
  collisions

abstract:
  I critically review the status of computations of threshold pion production
in proton-proton collisions in the framework of effective field theory
approaches or variants thereof. I also present the results of a novel
diagrammatic scheme.


title: Charmed Mesic Nuclei: Bound D and $\bar{D}$ states with ^{208}Pb

abstract:
  We show that the D^- meson will form narrow bound states with ^{208}Pb. Mean
field potentials for the D^0, D^0-bar and D^- in ^{208}Pb are calculated
self-consistently using the quark-meson coupling (QMC) model in local density
approximation. The meson-^{208}Pb bound state energies are then calculated by
solving the Klein-Gordon equation with these potentials. The experimental
confirmation and comparison with the D^0-bar and D^0 will provide distinctive
information on the nature of the interaction between the charmed meson and
matter.


title: Exchange currents in radiative hyperon decays and hyperon charge radii

abstract:
  Radiative decays of decuplet hyperons and octet hyperon charge radii are
evaluated in a chiral constituent quark model emphasizing the role of exchange
currents. Exchange currents largely cancel for the M1 decay amplitudes, while
they dominate the E2 amplitude. Due to the pseudoscalar meson cloud the charge
radii of Sigma^- and Xi^- are almost as large as the proton radius, in
agreement with recent experimental results from SELEX. Strangeness suppression
is weakened by exchange currents for several observables.


title: Spin Dependent Parton Distributions in a Bound Nucleon

abstract:
  The determination of the spin distribution functions for the neutron requires
an understanding of the changes induced by a nuclear medium. We present the
first estimates of the changes induced in the spin-dependent, valence parton
distributions of the proton and neutron bound in $^3$He and $^6$Li. For $^3$He
the result is quite reassuring, in that the off-shell correction to $g_{1n}$ is
very small. On the other hand, in $^6$Li the corrections to the spin
distributions in the bound proton are sufficiently large that they should be
taken into account if one aims for a precision of better than 10%. We provide a
simple parametrization of the off-shell changes in the valence spin
distributions of $^3$He and $^6$Li, which can be used with any conventional
estimate of nuclear binding and Fermi motion corrections.


title:
Multipole Analyses for p(gamma,pi) and p(gamma,gamma) in the region of
  the P33 delta Resonance

abstract:
  Multipole analyses of the p(g,pi0), p(g,pi+) and p(g,g) reactions are carried
out using different data sets. With sufficient constraints from polarization
observables, the ratio of E2/M1 transition amplitudes for N->delta (EMR)
appears to be largely insensitive to differences between recent p(g,pi0) cross
section measurements. We deduce a current best estimate of EMR = -(2.85 +/-0.34
+/-0.21)%. Back angle Compton cross sections require a value for the backward
spin polarizability that is significantly lower than previous expectations,
with a magnitude that is coupled to the (g,pi) cross sections.


title:
The weak strangeness production reaction $pn \to p\Lambda$ in a
  one-boson-exchange model

abstract:
  The weak production of Lambdas in nucleon-nucleon scattering is studied in a
meson-exchange framework. The weak transition operator for the $NN \to N
\Lambda$ reaction is identical to a previously developed weak
strangeness-changing transition potential $\Lambda N \to NN$ that describes the
nonmesonic decay of hypernuclei. The initial $NN$ and final $YN$ state
interaction has been included by using realistic baryon-baryon forces that
describe the available elastic scattering data. The total and differential
cross sections as well as the parity-violating asymmetry are studied for the
reaction $pn \to p\Lambda$. These observables are found to be sensitive to the
choice of the strong interaction potential and the structure of the weak
transition potential.


title:
Tensor Polarized Gamma-Deuteron Compton Scattering in Effective Field
  Theory

abstract:
  The differential cross section for gamma-deuteron Compton scattering from a
tensor polarized deuteron is computed in an effective field theory. The first
non-vanishing contributions to this differential cross section are the
interference terms between the leading electric coupling diagrams and the
subleading single potential pion exchange diagrams or the subleading magnetic
moment coupling diagrams. At 90 degree photon scattering angle, only the pion
term contributes at this order to the tensor polarized differential cross
section. This provides a clean way to study the photon pion dynamics in the two
nucleon sector. The effect is measurable for photon energies between 40 and 80
MeV provided the uncertainty in the measured cross sections are less than 7%.


title: A Precursor of Chiral Symmetry Restoration in the Nuclear Medium

abstract:
  Spectral enhancement near the 2m_{\pi} threshold in the I=J=0 channel in
nuclei is shown to be a distinct signal of the partial restoration of chiral
symmetry. The relevance of this phenomenon with the possible detection of
2\pi^{0} and 2\gamma in hadron-nucleus and photo-nucleus reactions is
discussed.


title: Fock terms in the quark-meson coupling model

abstract:
  The mean field description of nuclear matter in the quark-meson coupling
model is improved by the inclusion of exchange contributions (Fock terms). The
inclusion of Fock terms allows us to explore the momentum dependence of
meson-nucleon vertices and the role of pionic degrees of freedom in matter. It
is found that the Fock terms maintain the previous predictions of the model for
the in-medium properties of the nucleon and for the nuclear incompressibility.
The Fock terms significantly increase the absolute values of the
single-particle, four-component scalar and vector potentials, a feature that is
relevant for the spin-orbit splitting in finite nuclei.


title: Uncertainties in the Solar Neutrino Flux

abstract:
  I discuss three issues relevant to solar neutrino flux measurements: cross
section uncertainties in pp chain reactions, uncertainties in the GALLEX/SAGE
response to 7Be and 51Cr neutrinos, and the implications of helioseismology for
nonstandard suns with mixed cores. A few comments are also offered on electron
neutrino to tauon neutrino oscillations, cosmologically interesting neutrino
masses, and recent proposals for supernova neutrino observatories.


title: Unified relativistic description of piNN and gamma-piNN

abstract:
  We present a unified description of the relativistic piNN and gamma-piNN
systems where the strong interactions are described non-perturbatively by
four-dimensional integral equations. A feature of our approach is that the
photon is coupled in all possible ways to the strong interaction contributions.
Thus the hadronic processes NN -> NN, NN -> pid, pid -> pid, etc. and
corresponding electromagnetic processes NN -> gamma-NN, gamma-d -> NN, gamma-d
-> pid, ed -> ed, ed -> e'pid, etc., are described simultaneously within the
one model of strong interactions. Our formulation obeys two and three-body
unitarity, and as photons are coupled everywhere in the strong interaction
model, gauge invariance is implemented in the way prescribed by quantum field
theory. Our formulation is also free from the overcounting and undercounting
problems plaguing four-dimensional descriptions of piNN-like systems. The
unified description is achieved through the use of the recently introduced
gauging of equations method.


title: Nuclear surface properties in relativistic effective field theory

abstract:
  We perform Hartree calculations of symmetric and asymmetric semi-infinite
nuclear matter in the framework of relativistic models based on effective
hadronic field theories as recently proposed in the literature. In addition to
the conventional cubic and quartic scalar self-interactions, the extended
models incorporate a quartic vector self-interaction, scalar-vector
non-linearities and tensor couplings of the vector mesons. We investigate the
implications of these terms on nuclear surface properties such as the surface
energy coefficient, surface thickness, surface stiffness coefficient, neutron
skin thickness and the spin-orbit force.


title: Rescattering effects in coherent eta-photoproduction on the deuteron

abstract:
  Rescattering effects in coherent eta photoproduction on the deuteron are
studied in the region of the S_11(1535) resonance. For the elementary reaction
mechanism on the nucleon, an effective isobar model with inclusion of
resonances and Born terms is used. The resonance parameters are fixed by
considering pion photoproduction only. For the coherent eta production on the
deuteron we have considered the impulse approximation taking into account the
P_11(1440), D_13(1520), and S_11(1535) resonances, rescattering, and meson
exchange currents. For the rescattering mechanism a coupled channel model
including the dominant S_11(1535) resonance is used.


title: Structure of the ^3He in Backward Elastic p ^3He-Scattering

abstract:
  Backward elastic $p ^3He$-scattering at incident proton kinetic energies
$T_p>1$ GeV is investigated in the framework of the np-pair transfer mechanism
and triangular diagram of one-pion exchange with a subprocess $pd\to ^3He\pi^0$
using a realistic three-body wave function of the $^3He$ nucleus.
  It is found that the $np-$pair transfer mechanism dominates owing to a rich
high momentum component of the $^3He$ wave function.
  We show that the experimental cross section of this process is defined mainly
by the values of the Faddeev component of the $^3He$ wave function, $\phi
^{23}({\bf q}_{23}, {\bf p}_1)$, at high relative momenta $q_{23}> 0.6 GeV/c$
of the NN-pair in the $^1S_0$-state and at low spectator momenta $p_1\leq 0.1$
GeV/c. The spin-spin correlation parameter is calculated in the framework of
the dominating mechanism for the case of polarized target and beam.
Rescatterings in the initial and final states are taken into account.
Comparison with the $pd\to dp$ process is performed.


title: J/\Psi production in \pi N collisions

abstract:
  We calculate the total cross section for $\pi N \to J/\Psi N$ based on
$\rho$-meson exchange. On the basis of this calculation we predict a maximal
reaction rate arising from the OZI-violating $J/\Psi{\leftrightarrow}\rho\pi$
vertex in tree-level. Our estimate for the maximum reaction rate is still one
order of magnitude smaller than the existing predictions which were based on
the other OZI-violating mechanisms.


title: Final state interaction in near-threshold meson production

abstract:
  We address the question what information, other than the Final State
Interaction parameters, one can extract from data on near-threshold meson
production.


title: The $\omega NN$ couplings derived from QCD sum rules

abstract:
  The light cone QCD sum rules are derived for $\omega NN$ vector and tensor
couplings simultaneously. The vacuum gluon field contribution is taken into
account. Our results are $g_\omega =(18\pm 8), \kappa_\omega=(0.8\pm 0.4)$.


title: Spin polarizabilities of the nucleon

abstract:
  Spin polarizabilities of the nucleon are discussed in the framework of
fixed-t and backward-angle dispersion relations, chiral perturbation theory,
and the non-relativistic quark model. Calculations with the dispersion
relations generally confirm findings from HBChPT and disagree with a recent
experimental result from LEGS for the backward spin polarizability.


title: Response function beyond mean field of neutron-rich nuclei

abstract:
  The damping of single-particle and collective motion in exotic isotopes is a
new topic and its study may shed light on basic problems of nuclear dynamics.
For instance, it is known that nuclear structure calculations are not able, as
a rule, to account completely for the empirical single-particle damping. In
this contribution, we present calculations of the single-particle self-energy
in the case of the neutron-rich light nucleus $^{28}$O, by taking proper care
of the continuum, and we show that there are important differences with the
case of nuclei along the valley of stability.


title: Squeezed Correlations and Spectra for Mass-Shifted Bosons

abstract:
  Huge back-to-back correlations are shown to arise for thermal ensembles of
bosonic states with medium-modified masses. The effect is experimentally
observable in high energy heavy ion collisions.


title:
Time-Dependent Hartree-Fock simulation of the expansion of abraded
  nuclei

abstract:
  A recent interpretation of the caloric curve based on the expansion of the
abraded spectator nucleus is re-analysed in the framework of the Time-Dependent
Hartree-Fock (TDHF) evolution. It is shown that the TDHF dynamics is more
complex than a single monopolar collective motion at moderate energy. The
inclusion of other important collective degrees of freedom may lead to the
dynamical creation of hollow structure. Then, low density regions could be
locally reached after a long time by the creation of these exotic density
profiles. In particular the systematic of the minimum density reached during
the expansion (the so-called turning points) appears to be different.


title:
Local Thermal and Chemical Equilibration and the Equation of State in
  Relativistic Heavy Ion Collisions

abstract:
  Thermodynamical variables and their time evolution are studied for central
relativistic heavy ion collisions from 10.7 to 160 AGeV in the microscopic
Ultrarelativistic Quantum Molecular Dynamics model (UrQMD). The UrQMD model
exhibits drastic deviations from equilibrium during the early high density
phase of the collision. Local thermal and chemical equilibration of the
hadronic matter seems to be established only at later stages of the quasi-
isentropic expansion in the central reaction cell with volume 125 fm$^{3}$.
distributions at all collision energies for $t\geq 10 fm/c$ with a unique
Baryon energy spectra in this cell are approximately reproduced by Boltzmann
rapidly dropping temperature. At these times the equation of state has a simple
form: $P \cong (0.12-0.15) \epsilon$. At 160 AGeV the strong deviation from
chemical equilibrium is found for mesons, especially for pions, even at the
late stage of the reaction. The final enhancement of pions is supported by
experimental data.


title: Quantal Extension of Mean-Field Dynamics

abstract:
  A method is presented for numerical implementation of the extended TDHF
theory in which two-body correlations beyond the mean-field approximation are
incorporated in the form of a quantal collision term. The method is tested in a
model problem in which the exact solution can be obtained numerically. Whereas
the usual TDHF fails to reproduce the long time evolution, a very good
agreement is found between the extended TDHF and the exact solution.


title:
Problems with Extraction of the Nucleon to Delta(1232) Photonic
  Amplitudes

abstract:
  We investigate the model dependence and the importance of choice of database
in extracting the {\it physical} nucleon-Delta(1232) electromagnetic transition
amplitudes, of interest to QCD and baryon structure, from the pion
photoproduction observables. The model dependence is found to be much smaller
than the range of values obtained when different datasets are fitted. In
addition, some inconsistencies in the current database are discovered, and
their affect on the extracted transition amplitudes is discussed.


title: Weak Form Factors of the Nucleon

abstract:
  We limit ourselves basically to the SU(2) flavor sector of the CKM matrix, as
probed in processes like nuclear $\beta$-decay, normal and radiative muon
capture and neutrino reactions. Current interests in this primarily stem from
our aspirations to interpret the weak form factors of the nucleon in the
framework of QCD. Given a standard set of known form factors, we can look also
in these processes for possible physics signals beyond the standard model.


title: Beating of monopole modes in nuclear dynamics

abstract:
  Time-dependent Hartree-Fock simulations of the evolution of excited gold
fragments have been performed. The observed dynamics appears more complex than
the collective expansion picture. The minimum density is often not reached
during the first density oscillation because of the beating of several
collective compression modes.


title: Quantum and statistical fluctuations in dynamical symmetry breaking

abstract:
  Dynamical symmetry breaking in an expanding nuclear system is investigated in
semi-classical and quantum framework by employing a collective transport model
which is constructed to mimic the collective behavior of expanding systems. It
is shown that the fluctuations in collective coordinates during the expansion
are developed mainly by the enhancement of the initial fluctuations by the
driving force, and that statistical and quantum fluctuations have similar
consequences. It is pointed out that the quantal fluctuations may play an
important role in the development of instabilities by reducing the time needed
to break the symmetry, and the possible role of quantal fluctuations in
spinodal decomposition of nuclei is discussed.


title:
Finite Temperature Nuclear Response in Extended Random-Phase
  Approximation

abstract:
  The nuclear collective response at finite temperature is investigated for the
first time in the quantum framework of the small amplitude limit of the
extended TDHF approach, including a non-Markovian collision term. It is shown
that the collision width satisfies a secular equation. By employing a Skyrme
force, the isoscalar monopole, isovector dipole and isoscalar quadrupole
excitations in $^{40}Ca$ are calculated and important quantum features are
pointed out. The collisional damping due to decay into incoherent 2p-2h states
is small at low temperatures but increases rapidly at higher temperatures.


title: Virial corrections to simulations of heavy ion reactions

abstract:
  Within QMD simulations we demonstrate the effect of virial corrections on
heavy ion reactions. Unlike in standard codes, the binary collisions are
treated as non-local so that the contribution of the collision flux to the
reaction dynamics is covered. A comparison with standard QMD simulations shows
that the virial corrections lead to a broader proton distribution bringing
theoretical spectra closer towards experimental values. Complementary BUU
simulations reveal that the non-locality enhances the collision rate in the
early stage of the reaction. It suggests that the broader distribution appears
due to an enhanced pre-equilibrium emission of particles.


title: On the possibility of $f_0$ observation in low energy $pp$ collisions

abstract:
  Within the meson-exchange model we calculate $f_0$-meson production cross
section in $\piN$ and $NN$ reactions and investigate the possibility for $f_0$
observation via the $K\bar{K}$ decay mode in $pp$ collisions. Our studies
indicate that an extraction of the $f_0$ signal is unlikely due to the large
background from other reaction channels.


title: Having a BLAST with Excited Baryons

abstract:
  We discuss the role BLAST can play in the valuable kinematic window of low W
and low Q^2.


title: Elastic Scattering of Pions From the Three-nucleon System

abstract:
  We examine the scattering of charged pions from the trinucleon system at a
pion energy of 180 MeV. The motivation for this study is the structure seen in
the experimental angular distribution of back-angle scattering for pi+ 3He and
pi- 3H but for neither pi- 3He nor pi+ 3H. We consider the addition of a double
spin flip term to an optical model treatment and find that, though the
contribution of this term is non-negligible at large angles for pi+ 3He and pi-
3H, it does not reproduce the structure seen in the experiment.


title: Approaches to threshold meson production

abstract:
  Near-threshold data on meson production in nucleon-nucleon scattering are
analysed in the short-range limit which permits a quantitative comparison of
the production in two and three-body final states. The relative strengths of
different meson productions are broadly in line with the predictions of
one-meson-exchange models and it is deviations from these which are indications
of extra physics.


title: Questions on the Quark Model: Panel Discussion

abstract:
  We discuss the effect of model space truncation on current conservation in
quark model calculations.


title:
Monte-Carlo Study of Bound States in a Few-Nucleon System - Method of
  Continued Fractions -

abstract:
  We propose a new type of Monte-Carlo method which enables us to study the
excited state of many-body systems.


title: Prediction of Thermonuclear Reaction Rates in Astrophysics

abstract:
  Recent improvements and remaining problems in the prediction of thermonuclear
rates are reviewed. The main emphasis is on statistical model calculations, but
the challenge to include direct reactions close to the driplines is also
briefly addressed. Further theoretical as well as experimental investigations
are motivated.


title:
Phase space density and chiral symmetry restoration in relativistic
  heavy ion collisions

abstract:
  The effect of altered hadron masses is studied for its effect with regard to
final-state hadronic observables. It is shown that the final phase space
densities of pions and kaons, which can be inferred experimentally, are
sensitive to in-medium properties of the excited matter at earlier stages of
the collision, but that the sensitivity is significantly moderated by
interactions that change the effective numbers of pions and kaons during the
latter part of the collision.


title: Dispersion Relation of the Rho-Meson at Finite Temperature and Density

abstract:
  The rho-meson mass shift, width broadening, and spectral density at finite
temperature and nucleon density are estimated using a general formula which
relates the self-energy to the real and imaginary parts of the forward
scattering amplitude on the constituents of the medium. We saturate the
scattering amplitude at low energies with resonances, while at high energies a
Regge approach is taken in combination with vector meson dominance;
experimental data is used wherever possible. The main result is that the
rho-meson becomes increasingly broad with increasing nucleon density. The
spectral density is suppressed in the resonance region 600 < M < 900 MeV and
enhanced in the subresonance region M < 600 MeV.


title:
Investigation of N-N* Electromagnetic Form Factors within a Front-Form
  CQM

abstract:
  The helicity amplitudes for the transitions $N-S_{11}$ and $N-S_{31}$ are
presented. The amplitudes have been obtained within our front-form CQM model,
based on hadron eigenstates of a relativistic mass operator and CQ current with
Dirac and Pauli form factors.


title:
A Poincar\'e Covariant Current Operator for Low and High Energy
  Phenomena

abstract:
  Within front-form dynamics and in the Breit frame where initial and final
three-momenta of the system are directed along the $z$ axis, Poincar\'e
covariance constrains the current operator only through kinematical rotations
around the $z$ axis. Therefore, in this frame the current can be taken in the
one-body form. Applications to deep inelastic structure functions in an exactly
solvable model and to the deuteron magnetic form factor are presented.


title: Effective field theory for lambda-sigma^0 mixing in nuclear matter

abstract:
  We extend the effective field theory approach which successfully describes
ordinary nuclei and nuclear matter to incorporate strangeness in nuclear
structure. Central object is a chiral effective Lagrangian involving the baryon
octet, the Goldstone boson octet, the vector meson octet and a light scalar
singlet. According to the rules of effective field theory, we include all
interaction terms (up to a given order of truncation) that are consistent with
the underlying symmetries of QCD. We develop a mean-field approximation and
study nuclear matter as a simple model for multi-strange systems. A D-type
Yukawa coupling between baryons and vector mesons leads to lambda-sigma^0
flavor mixing in the nuclear medium. We study flavor oscillations in the
nuclear matter ground state which are closely related to the phenomenon of
neutrino oscillations.


title: Strange Messages: Chemical and Thermal Freeze-out in Nuclear Collisions

abstract:
  Thermal models are commonly used to interpret heavy-ion data on particle
yields and spectra and to extract the conditions of chemical and thermal
freeze-out in heavy-ion collisions. I discuss the usefulness and limitations of
such thermal model analyses and review the experimental and theoretical
evidence for thermalization in nuclear collisions. The crucial role of
correlating strangeness production data with single particle spectra and
two-particle correlation measurements is pointed out. A consistent dynamical
picture for the heavy-ion data from the CERN SPS involves an initial
prehadronic stage with deconfined color and with an appreciable isotropic
pressure component. This requires an early onset of thermalization.


title: The triple-alpha process and its anthropic significance

abstract:
  Through the triple-alpha process practically all of the carbon in our
universe is synthesized as the ash of helium burning in red giants. The
triple-alpha process proceeds trough the ground state of 8Be and though the
02+-state in 12C. We investigate the dependence of 02+-state and the production
of carbon as a function of the strength of the underlying nucleon-nucleon
interaction. This is performed by using the complex scaling method in a
microscopic cluster model.


title: Covariant formulation of pion-nucleon scattering

abstract:
  A covariant model of elastic pion-nucleon scattering based on the
Bethe-Salpeter equation is presented. The kernel consists of s- and u-channel
nucleon and delta poles, along with rho and sigma exchange in the t-channel. A
good fit is obtained to the s- and p-wave phase shifts up to the two-pion
production threshold.


title: J/Psi Absorption Scenarios in Nuclear Collisions

abstract:
  We study the production of $c \bar{c}$ pairs and dimuons from hard collisions
in nuclear reactions within the covariant transport approach HSD. Adopting 6 mb
for the $c \bar{c}$-baryon cross section the data on $J/\Psi$ suppression in p
+ A reactions are reproduced in line with calculations based on the Glauber
model. Furthermore, using $J/\Psi$ absorption cross sections with mesons above
the $D\bar{D}$ threshold in the order of 1.5 - 3 mb we find that all data on
$J/\Psi$ suppression from NA38/NA50 can be described without assuming the
formation of a quark-gluon plasma. Alternatively, we also investigate an
'early'-comover absorption scenario where the $c \bar{c}$ pairs are dissociated
in the color electric fields of neighboring strings. Again we find good
agreement with the experimental data with an estimate for the string radius of
$R_s \approx 0.2-0.25 fm$.


title:
Scaling properties of the longitudinal and transversal asymmetries of
  the $\vec{n}\vec{d}$ total cross section

abstract:
  The longitudinal and transversal asymmetries of the total $\vec{n}\vec{d}$
cross section are calculated. Four modern nucleon-nucleon interactions: AV18,
CD Bonn, NijmI and NijmII, give different predictions for these observables.
When the three-nucleon Hamiltonian is supplemented by the $2\pi$-exchange
Tucson-Melbourne three-nucleon force (3NF), individually adjusted with each
particular NN potential to reproduce the experimental triton binding energy,
all predictions practically coincide. We propose to check this scaling behavior
experimentally in order to get a clear signal for 3NF effects in the low energy
three-nucleon continuum. Connected to that is the proposal to measure the
energy at which the longitudinal asymmetry goes through zero. This energy is
shifted by about 400 keV when 3NF's are acting.


title: Single Particle and Collective Structure for Nuclei near Sn-132

abstract:
  A new Nilsson single-particle structure is proposed for neutron-rich nuclei
near $^{132}$Sn. In general, a large reduction in spin-orbit interaction is
required and the neutron $N = 82$ gap persists in the new set of parameters.
The ground state deformations for several isotopic chains are studied with this
set and compared with the results of the standard set and with measured ones.
Collective bands in two even-even, neutron-rich nuclei are calculated using the
Projected Shell Model with the new set of parameters and improved agreement
with existing data is found.


title: Restoration of Isospin Symmetry in Highly Excited Nuclei

abstract:
  Explicit relations between the isospin mixing probability, the spreading
width $\Gamma_{IAS}^{\downarrow}$ of the Isobaric Analog State (IAS) and the
statistical decay width $\Gamma_c$ of the compound nucleus at finite excitation
energy, are derived by using the Feshbach projection formalism. The temperature
dependence of the isospin mixing probability is discussed quantitatively for
the first time by using the values of $\Gamma_{IAS}^{\downarrow}$ and of
$\Gamma_c$ calculated by means of microscopic models. It is shown that the
mixing probability remains essentially constant up to a temperature of the
order of 1 MeV and then decreases to about 1/4 of its zero temperature value,
at higher temperature than $\approx$ 3 MeV, due to the short decay time of the
compound system.


title:
A New Type of Shape Instability of Hot Nuclei and Prompt Nuclear
  Fragmentation

abstract:
  A novel mechanism of prompt nuclear fragmentation is proposed. Assuming
micro-canonical or canonical equilibrium, it is shown that a strong enhancement
of the accessible phase space volume, due to the diffuceness of the nuclear
surface, leads to dynamical instabilities of hot nuclei and to prompt
fragmentation. Equations are derived for the transition temperature T_T, for
which the thermodynamical surface tension vanishes, as well as for the
thermodynamical fissility parameter chi_td.


title: Charmonium Production at the SPS

abstract:
  We reexamine the production of J/Psi and other charmonium states for a
variety of target-projectile choices at the SPS, in particular for the
interesting comparison between S+U at 200 GeV/c and Pb+Pb at 158 GeV/c as
observed in the experiments NA38 and NA50 respectively. The result is a
description of the NA38 and NA50 data in terms of a conventional,
quasi-hadronic picture. The apparently anomalous suppression found in the most
massive Pb+Pb system arises in the present simulation from three sources:
destruction in the initial nucleon-nucleon cascade phase, use of coupled
channels to exploit the larger breakup in the less bound Chi and Psi' states,
and comover interaction in the final low energy phase.


title:
Solar proton burning, photon and anti-neutrino disintegration of the
  deuteron in the relativistic field theory model of the deuteron

abstract:
  The relativistic field theory model of the deuteron (RFMD) is applied to the
calculation of the astrophysical factor S_{pp}(0) for the process of the solar
proton burning p + p -> D + e^+ + \nu_e and the cross sections for the
disintegration of the deuteron by photons gamma + D -> n + p and anti-neutrinos
\bar{\nu}_e + D -> e^+ + n + n. Our theoretical value of the astrophysical
factor S_{pp}(0) = 4.02 x 10^{-25} MeV b agrees with the classical result
obtained by Bahcall and Kamionkowski S_{pp}(0) = 3.89 x 10^{-25} MeV b in the
potential model approach (PMA). The cross sections for the disintegration of
the deuteron by photons and anti-neutrinos calculated near thresholds are in
good agreement with the PMA. An extrapolation of the cross sections for
energies far from thresholds is suggested and related to the inclusion of form
factors describing spatial smearing of the deuteron and the NN system. The
extrapolated cross section for the disintegration of the deuteron by
anti-neutrinos agrees with that calculated in the PMA in the anti-neutrino
energy region from threshold up to 10 MeV. The extrapolated cross section
averaged over the reactor anti-neutrino energy spectrum is obtained in
agreement with the experimental data. It is shown that the RFMD enables to
describe elastic low-energy NN scattering in accordance with low-energy nuclear
phenomenology.


title: Microscopic Structure of Rotational Damping

abstract:
  The damping of collective rotational motion is studied microscopically,
making use of shell model calculations based on the cranked Nilsson deformed
mean-field and on residual two-body interactions, and focusing on the shape of
the gamma-gamma correlation spectra and on its systematic behavior. It is shown
that the spectral shape is directly related to the damping width of collective
rotation, \Gammarot, and to the spreading width of many-particle many-hole
configurations, \Gammamu. The rotational damping width is affected by the shell
structure, and is very sensitive to the position of the Fermi surface, besides
mass number, spin and deformation. This produces a rich variety of features in
the rotational damping phenomena.


title:
Non-axial Octupole Deformations of N=Z Nuclei in $A \sim 60-80$ Mass
  Region

abstract:
  By performing a fully three dimensional Hartree-Fock calculation with use of
the Skyrm forces, we demonstrate possibility of exotic deformations violating
both the reflection and the axial symmetries of N=Z nuclei in $A \sim 60-80$
mass region. The \Ytwo tetrahedral shape predicted in excited \Zr arises from a
shell gap at $N,Z = 40$ which is enhanced for the tetrahedron deformation.
Softness toward the \Ythree triangular deformation of the oblate state in \Se
is also predicted.


title:
Effects of the ground state correlations on the structure of vibrational
  states

abstract:
  A method to treat the ground state correlations beyond the RPA is presented.
A set of nonlinear equations taking into account effects of the ground state
correlations on the pairing and phonon-phonon coupling is derived. The
influence of such correlations on properties of the vibrational states in
spherical nuclei is studied.


title: The Reaction $pp \to pp\phi$ and the Validity of the OZI Rule

abstract:
  The reaction $pp \to pp \phi$ is investigated within a relativistic
meson-exchange model of hadronic interactions. The possibility of extracting
the $NN\phi$ coupling constant from a study of this process is explored. A
combined analysis of $\omega-$ and $\phi$-meson production in proton-proton
collisions utilizing recent data on these reactions is carried out and yields
values for $g_{NN\phi}$ that are compatible with the OZI rule.


title: The role of the $P_{11}(1710)$ in the $NN{\to}N{\Sigma}K$ reaction

abstract:
  Using the resonance model, which was successfully applied for the study of
the $pp{\to}p{\Lambda}K^+$ reaction, we investigate $NN{\to}N{\Sigma}K$
reactions that should provide cleaner information about resonance excitations
and meson exchange contributions. For this purpose we demonstrate that the
invariant mass distribution for the ${\Sigma}K$ system, as well as the Dalitz
plot for the $NN{\to}N{\Sigma}K$ reaction, provide direct information about the
${\Sigma}K$ production mechanism, which can be tested in the near future by
experiments at COSY.


title:
Covariant representations of the relativistic Brueckner T-matrix and the
  nuclear matter problem

abstract:
  We investigate nuclear matter properties in the relativistic Brueckner
approach. The in-medium on-shell T-matrix is represented covariantly by five
Lorentz invariant amplitudes from which we deduce directly the nucleon
self-energy. We discuss the ambiguities of this approach and the failure of
previously used covariant representations in reproducing the nucleon
self-energies on the Hartree-Fock level. To enforce correct Hartree-Fock
results we develop a subtraction scheme which treats the bare nucleon-nucleon
potential exactly in accordance to the different types of meson exchanges. For
the remaining ladder kernel, which contains the higher order correlations, we
employ then two different covariant representations in order to study the
uncertainty inherent in the approach. The nuclear matter bulk properties are
only slightly sensitive on the explicit representation used for the kernel.
However, we obtain new Coester lines for the various Bonn potentials which are
shifted towards the empirical region of saturation. In addition the nuclear
equation-of-state turns out to be significantly softer in the new approach.


title: Weak Magnetism in Two Neutrino Double Beta Decay

abstract:
  We have extended the formalism for the two-neutrino double beta decay by
including the weak-magnetism term, as well as other second-forbidden
corrections. The weak magnetism diminishes the calculated half-lives in $\sim
10%$, independently of the nuclear structure. Numerical computations were
performed within the pn-QRPA, for $^{76}Ge$, $^{82}Se$, $^{100} Mo$, $^{128}Te$
and $^{130}Te$ nuclei. No one of the second-forbidden corrections modifies
significantly the spectrum shapes. The total reduction in the calculated half
lives varies from 6% up to 32%, and strongly depend on the nuclear interaction
in the particle-particle $S=1,T=0$ channel. We conclude that the higher order
effects in the weak Hamiltonian would hardly be observed in the two-neutrino
double beta experiments.


title:
Comparison of triton bound state properties using different separable
  representations of realistic potentials

abstract:
  The quality of two different separable expansion methods ({\sl W} matrix and
Ernst-Shakin-Thaler) is investigated. We compare the triton binding energies
and components of the triton wave functions obtained in this way with the
results of a direct two-dimensional treatment. The Paris, Bonn {\sl A} and Bonn
{\sl B} potentials are employed as underlying two-body interactions, their
total angular momenta being incorporated up to $j \leq 2$. It is found that the
most accurate results based on the Ernst-Shakin-Thaler method agree within 1.5%
or better with the two-dimensional calculations, whereas the results for the
{\sl W}-matrix representation are less accurate.


title:
Compton Scattering on the Charged Pion and the Process \gamma\gamma \to
  \pi^0 \pi^0

abstract:
  The Compton scattering on a charged pion and the process \gamma\gamma \to
\pi^0\pi^0 are studied using the dispersion relations. Unknown parameters of
the S-wave \pi\pi interaction, represented as a board Breit-Wignar resonance,
and a sum and a difference of the \pi^0 meson polarizabilities are found from a
fit to the experimental data for the process \gamma+\gamma \to \pi^0+\pi^0.
This fit gives \alpha+\beta=0.98\pm 0.03 and \alpha-\beta=-1.6\pm 2.2. The
found parameters of the S-wave \pi\pi interaction are used for the calculation
of the cross section of the Compton scattering on \pi^{\pm} meson. The analysis
of the obtained results shows that the experimental data for the elastic
\gamma\pi scattering in the energy region up to 1 GeV together with the data
for the process \gamma+\gamma \to \pi^0+\pi^0 could be used both for a
determination of the pion polarizability values with quite high accuracy and
for study of the S-wave \pi\pi interaction.


title:
2-Nucleon 1-Loop Corrections to Pion Double Charge Exchange within Heavy
  Baryon Chiral Perturbation Theory

abstract:
  One-loop corrections at the two-nucleon level to Pion Double Charge exchange
(DCX) scattering off a nuclear target at threshold, are calculated within the
framework of Heavy Baryon Chiral Perturbation Theory (HBChPT). An estimate for
the (2-nucleon) 1-loop correction is obtained in the static limit and using an
impulse approximation. We find a small (1.6%) increase relative to the leading
order tree graphs.


title: One loop corrections to quantum hadrodynamics with vector mesons

abstract:
  The renormalized elastic $\pi\pi$ scattering amplitude to one loop is
calculated in the chiral limit in the $\sigma$ model and in a Quantum
Hadrodynamic model (QHD-III) with vector mesons. It is argued that QHD-III
reduces to the linear $\sigma$ model in the limit that the vector meson masses
become large. The pion decay constant is also calculated to 1-loop in the
$\sigma$ model, and at tree level in QHD-III; it is shown that the coefficient
of the tree level term in the scattering amplitude equals $F_\pi^{-2}$. The
1-loop correction of $F_\pi$ in QHD-III violates strong isospin current
conservation. Thus,it is concluded that QHD-III can, at best, only describe the
strongly interacting nuclear sector.