title: Baryon Mapping of Quark Systems

abstract:
  We discuss a mapping procedure from a space of colorless three-quark clusters
into a space of elementary baryons and illustrate it in the context of a
three-color extension of the Lipkin model recently developed. Special attention
is addressed to the problem of the formation of unphysical states in the mapped
space. A correspondence is established between quark and baryon spaces and the
baryon image of a generic quark operator is defined both in its Hermitian and
non-Hermitian forms. Its spectrum (identical in the two cases) is found to
consist of a physical part containing the same eigenvalues of the quark
operator in the cluster space and an unphysical part consisting only of zero
eigenvalues. A physical subspace of the baryon space is also defined where the
latter eigenvalues are suppressed. The procedure discussed is quite general and
applications of it can be thought also in the correspondence between systems of
2n fermions and n bosons.


title: Antiprotonic studies of nuclear neutron haloes

abstract:
  Nuclear capture of antiprotons from atomic states is studied. Partial widths
for single nucleon capture events leading to cold residual nuclei are
calculated. Recent CERN experiments that compare the neutron and proton
captures are analysed. Nuclear density distributions at extreme nuclear surface
are calculated and tested against the experimental results.


title: Proton momentum distribution in nuclei beyond Helium-4

abstract:
  Proton momentum distributions of the $^{12}C$, $^{16}O$, $^{40}Ca$, $^{56}Fe$
and $^{208}$Pb nuclei are calculated by a model using the natural orbital
representation and the experimental data for the momentum distribution of the
$^{4}He$ nucleus. The model allows realistic momentum distributions to be
obtained using only hole-state natural orbitals (or mean-field single-particle
wave functions as a good approximation to them). To demonstrate the model two
different sets of wave functions were employed and the predictions were
compared with the available empirical data and other theoretical results.


title:
Nuclear Gluon Shadowing via Continuum Lepton Pairs in $p+A$ at $\sqrt
  s=200$ AGeV

abstract:
  The dilepton spectra from open charm decay in $p+A$ reactions at $\sqrt
s=200$ AGeV are proposed to constrain gluon shadowing in nuclei. We show that
the required measurements are feasible at RHIC.


title: Quantum Algebraic Symmetries in Nuclei and Molecules

abstract:
  Various applications of quantum algebraic techniques in nuclear and molecular
physics are briefly reviewed. Emphasis is put in the study of the symmetries of
the anisotropic quantum harmonic oscillator with rational ratios of
frequencies, which underly the structure of superdeformed and hyperdeformed
nuclei, the Bloch--Brink $\alpha$-cluster model and possibly the shell
structure in deformed atomic clusters.


title: Quantum Algebraic Symmetries in Nuclear Structure

abstract:
  Various applications of quantum algebraic techniques in nuclear structure
physics, such as the su$_q$(2) rotator model and its extensions, the use of
deformed bosons in the description of pairing correlations, and the
construction of deformed exactly soluble models (Interacting Boson Model,
Moszkowski model) are briefly reviewed. Emphasis is put in the study of the
symmetries of the anisotropic quantum harmonic oscillator with rational ratios
of frequencies, which underlie the structure of superdeformed and hyperdeformed
nuclei, the Bloch--Brink $\alpha$-cluster model and possibly the shell
structure in deformed atomic clusters.


title: Temperature dependence of the response function of hot nuclear matter

abstract:
  The description of collective motion in nuclei at finite temperature using
the framework of the random phase approximation is discussed. We focus on the
special case of the isovector response function of hot nuclear matter using
various effective Skyrme interactions.


title: Muons and emissivities of neutrinos in neutron star cores

abstract:
  In this work we consider the role of muons in various URCA processes relevant
for neutrino emissions in the core region of neutron stars. The calculations
are done for $\beta$--stable nuclear matter with and without muons. We find
muons to appear at densities $\rho = 0.15$ fm$^{-3}$, slightly around the
saturation density for nuclear matter $\rho_0 =0.16$ fm$^{-3}$. The direct URCA
processes for nucleons are forbidden for densities below $\rho = 0.5$
fm$^{-3}$, however the modified URCA processes with muons $(n+N\rightarrow p+N
+\mu +\overline{\nu}_{\mu}, p+N+\mu \rightarrow n+N+\nu_{\mu}$), where $N$ is a
nucleon, result in neutrino emissivities comparable to those from
$(n+N\rightarrow p+N +e +\overline{\nu}_e, p+N+e \rightarrow n+N+\nu_e$). This
opens up for further possibilities to explain the rapid cooling of neutrons
stars. Superconducting protons reduce however these emissivities at densities
below $0.4$ fm$^{-3}$.


title:
The dependence of the nuclear charge form factor on short range
  correlations and surface fluctuation effects

abstract:
  We investigate the effects of fluctuations of the nuclear surface on the
harmonic oscillator elastic charge form factor of light nuclei, while
simultaneously approximating the short-range correlations through a Jastrow
correlation ~factor. Inclusion of surface-fluctuation effects within this
description, by truncating the cluster expansion at the two-body part, is found
to improve somewhat the fit to the elastic charge form-factor of $^{16}O$ and
$^{40}Ca$. However, the convergence of the cluster expansion is expected to
deteriorate. An additional finding is that the surface-fluctuation correlations
produce a drastic change in the asymptotic behavior of the point-proton form
factor, which now falls off quite slowly (i.e. as $const. \cdot q^{-4}$) at
large values of the momentum transfer $q$.


title: Making Nuclei Out Of The Skyrme Crystal

abstract:
  A new method for approximating Skyrme solutions is developed. It consists of
cutting sections out of the Skyrme crystal and smoothly interpolating between
the boundary and spatial infinity. Several field configurations are
constructed, and their energies calculated. The surface energy (per unit area)
of an infinite flat plane of the crystal is also calculated, and the result
used to derive a formula analogous to the semi-empirical mass formula of
nuclear physics. This formula can be used to give some idea of what the Skyrme
model predicts about volume and surface energies of the nucleus over a broad
range of baryon numbers.


title: Weak Hypernuclear Decay

abstract:
  Because of Pauli suppression effects the $N\pi$ decay of the free $\Lambda$
is not of importance in hypernuclei with $A\geq 10$. Rather the decay of such
hypernuclei proceeds via the nucleon-stimulated mode $\Lambda N\rightarrow NN$,
analysis of which presents a considerable theoretical challenge and about which
there exists only a limited amount of experimental information. Herein we
confront existing data wih various theoretical analyses which have been
developed.


title: Cross section of $^{36}S(n,\gamma)^{37}S$

abstract:
  At the Karlsruhe pulsed 3.75 MV Van de Graaff accelerator the
$^{36}S(n,\gamma)^{37}S(5.05 min)$ cross section was measured by the fast
cyclic activation technique via the 3.103 MeV $\gamma$-ray line of the
$^{37}$S-decay. Samples of elemental sulfur enriched in $^{36}$S by 5.933 %
were irradiated between two gold foils which served as capture standards. The
capture cross section was measured at the neutron energies 25, 151, 176, and
218 keV, respectively. The $^{36}S(n,\gamma)^{37}S$-cross section in the
thermonuclear and thermal energy range has been calculated using the
direct-capture (DC) model combined with the folding procedure used for the
determination of the potentials. The non-resonant experimental data for this
reaction can be reproduced excellently using this method. The input parameters
of the DC-calculation (masses, Q-values, nuclear density distributions,
spectroscopic factors, spin-parity assignments and excitation energies of the
low-lying states of the residual nucleus) have been taken from the available
experimental data.


title: Quantum Chaos in A=46--50 Atomic Nuclei

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


title: QCD Sum Rules for Skeptics

abstract:
  A new Monte-Carlo based uncertainty analysis is introduced to quantitatively
determine the predictive ability of QCD sum rules. A comprehensive analysis of
ground state rho-meson and nucleon spectral properties is performed. Many of
the findings contradict the conventional wisdom of both practitioners and
skeptics alike. Associations between the phenomenological fit parameters are
particularly interesting as they reveal how the sum rules resolve the spectral
properties. The use of derivative sum rules for the determination of rho-meson
spectral properties is shown to be a very unfavorable approach. Most prior
nucleon sum rule analyses are based on a sum rule which is found to be invalid;
the results are suspect, and should be reevaluated. The ``Ioffe formula'',
argued by many to qualitatively encapsulate a description of the nucleon mass
in terms of the chiral symmetry breaking order parameter is misleading at best.
QCD Sum Rules are found to be self-consistent without contributions from direct
instantons. This implies that instanton effects are adequately accounted for in
the nonperturbative vacuum condensates. This in-depth examination of QCD sum
rule self consistency paints a favorable picture for further quantitative
refinements of the QCD sum rule approach.


title: SMMC method for two-neutrino double beta decay

abstract:
  Shell Model Monte Carlo (SMMC) techniques are used to calculate two-neutrino
double beta decay matrix elements. We validate the approach against direct
diagonalization for $^{48}$Ca in the complete $pf$-shell using the KB3
interaction. The method is then applied to the decay of $^{76}$Ge in the
$(0f_{5/2},1p,0g_{9/2})$ model space using a newly calculated realistic
interaction. Our result for the matrix element is $0.13\pm0.05$ MeV$^{-1}$, in
agreement with the experimental value.


title:
Nucleon Structure Functions at Moderate Q**2: Relativistic Constituent
  Quarks and Spectator Mass Spectrum

abstract:
  We present a model description of the nucleon valence structure function
applicable over the entire region of the Bjorken variable x, and above moderate
values of Q**2 (> 1 GeV**2). We stress the importance of describing the
complete spectrum of intermediate states which are spectator to the
deep-inelastic collision. At a scale of 1 GeV**2 the relevant degrees of
freedom are constituent quarks and pions. The large-x region is then described
in terms of scattering from constituent quarks in the nucleon, while the
dressing of constituent quarks by pions plays an important role at intermediate
x values. The correct small-x behavior, which is necessary for the proper
normalization of the valence distributions, is guaranteed by modeling the
asymptotic spectator mass spectrum according to Regge phenomenology.


title:
Equation of State of an Interacting Pion Gas with Realistic $\pi$--$\pi$
  Interactions

abstract:
  Within the finite-temperature Greens-function formalism we study the equation
of state of a hot interacting pion gas at zero chemical potential. Employing
realistic $\pi\pi$ meson-exchange interactions we selfconsistently calculate
the in-medium single-pion selfenergy and the $\pi\pi$ scattering amplitude in
the quasiparticle approximation. These quantities are then used to evaluate the
thermodynamic potential, $\Omega_\pi$(T), from which the state variables:
pressure-, entropy- and energy-density can be derived. In contrast to earlier
calculations based on the low-energy Weinberg Lagrangian we find an overall
increase as compared to the free-gas results. We also consider the possibility
of a dropping $\rho$-meson mass as suggested by the 'Brown-Rho Scaling' law.


title:
On the nature of nuclear dissipation, as a hallmark for collective
  dynamics at finite excitation

abstract:
  We study slow collective motion of isoscalar type at finite excitation. The
collective variable is parameterized as a shape degree of freedom and the mean
field is approximated by a deformed shell model potential. We concentrate on
situations of slow motion, as guaranteed, for instance, by the presence of a
strong friction force, which allows us to apply linear response theory. The
prediction for nuclear dissipation of some models of internal motion are
contrasted. They encompass such opposing cases as that of pure independent
particle motion and the one of "collisional dominance". For the former the wall
formula appears as the macroscopic limit, which is here simulated through
Strutinsky smoothing procedures. It is argued that this limit hardly applies to
the actual nuclear situation. The reason is found in large collisional damping
present for nucleonic dynamics at finite temperature $T$. The level structure
of the mean field as well as the $T$-dependence of collisional damping
determine the $T$-dependence of friction. Two contributions are isolated, one
coming from real transitions, the other being associated to what for infinite
matter is called the "heat pole". The importance of the latter depends strongly
on the level spectrum of internal motion, and thus is very different for
"adiabatic" and "diabatic" situations, both belonging to different degrees of
"ergodicity".


title:
Temperatures and Non-ideal Expansion in Ultrarelativistic
  Nucleus-Nucleus Collisions

abstract:
  The hadronic phase space distributions calculated with the transport model
RQMD for central S(200 AGeV) on S and Pb(160AGeV) on Pb collisions are analyzed
to study the deviations from ideal hydrodynamical evolution. After the
preequilibrium stage, which lasts for approximately 4 (2) fm/c in Pb+Pb (S+S)
the source stays in approximate kinetic equilibrium for about 2 fm/c at a
temperature close to 140 MeV. The interactions of mesons last until around 14
(5) fm/c during which time strong transverse flow is generated. The
interactions in the hadronic resonance gas are not sufficiently strong to
maintain ideal fluid expansion. While pions acquire average transverse fluid
velocities around 0.47-0.58 c, heavier particles like protons and kaons cannot
keep up with the pionic fluid, since their average velocities are smaller by
about 20 to 30 \%. Although kinetic equilibrium breaks down in the final dilute
stage of $AA$ collisions, the system resembles a thermal system at a
temperature of 130 MeV, if the free streaming of hadrons after freeze-out is
suppressed. This freeze-out temperature is consistent with estimates based on
mean free paths and expansion rates in a thermal fireball but lower than values
derived from fits to measured particle ratios and transverse momentum spectra.
The processes in RQMD to which the differences can be attributed to are the
non-ideal expansion of the hadronic matter and the absence of chemical
equilibrium at freeze-out.


title: Quasifree Pion Electroproduction from Nuclei in the $\Delta$ Region

abstract:
  We present calculations of the reaction $A(e,e^\prime \pi N)B$ in the
distorted wave impulse approximation. The reaction allows for the study of the
production process in the nuclear medium without being obscured by the details
of nuclear transition densities. First, a pion electroproduction operator
suitable for nuclear calculations is obtained by extending the Blomqvist-Laget
photoproduction operator to the virtual photon case. The operator is gauge
invariant, unitary, reference frame independent, and describes the existing
data reasonably well. Then it is applied in nuclei to predict nuclear cross
sections under a variety of kinematic arrangements. Issues such as the effects
of gauge-fixing, the interference of the $\Delta$ resonance with the
background, sensitivities to the quadrupole component of the $\Delta$
excitation and to the electromagnetic form factors, the role of final-state
interactions, are studied in detail. Methods on how to experimentally separate
the various pieces in the coincidence cross section are suggested. Finally, the
model is compared to a recent SLAC experiment.


title:
Rare-Earth Nuclei: Radii, Isotope-Shifts and Deformation Properties in
  the Relativistic Mean Field Theory

abstract:
  A systematic study of the ground-state properties of even-even rare earth
nuclei has been performed in the framework of the Relativistic Mean-Field (RMF)
theory using the parameter set NL-SH. Nuclear radii, isotope shifts and
deformation properties of the heavier rare-earth nuclei have been obtained,
which encompass atomic numbers ranging from Z=60 to Z=70 and include a large
range of isospin. It is shown that RMF theory is able to provide a good and
comprehensive description of the empirical binding energies of the isotopic
chains. At the same time the quadrupole deformations $\beta_{2}$ obtained in
the RMF theory are found to be in good agreement with the available empirical
values. The theory predicts a shape transition from prolate to oblate for
nuclei at neutron number N=78 in all the chains. A further addition of neutrons
up to the magic number 82 brings about the spherical shape. For nuclei above
N=82, the RMF theory predicts the well-known onset of prolate deformation at
about N=88, which saturates at about N=102. The deformation properties display
an identical behaviour for all the nuclear chains. A good description of the
above deformation transitions in the RMF theory in all the isotopic chains
leads to a successful reproduction of the anomalous behaviour of the empirical
isotopic shifts of the rare-earth nuclei. The RMF theory exhibits a remarkable
success in providing a unified and microscopic description of various empirical
data.


title: Optimized $\delta$ expansion for the Walecka model

abstract:
  The optimized $\delta$-expansion is used to study vacuum polarization effects
in the Walecka model. The optimized $\delta$-expansion is a nonperturbative
approach for field theoretic models which combines the techniques of
perturbation theory and the variational principle. Vacuum effects on
self-energies and the energy density of nuclear matter are studied up to ${\cal
O}(\delta^2)$. When exchange diagrams are neglected, the traditional
Relativistic Hartree Approximation (RHA) results are exactly reproduced and,
using the same set of parameters that saturate nuclear matter in the RHA, a new
stable, tightly bound state at high density is found.


title:
Mesonic and Binding Contributions to the EMC Effect in a Relativistic
  Many Body Approach

abstract:
  We revise the conventional nuclear effects of Fermi motion, binding and
pionic effects in deep inelastic lepton scattering using a relativistic
formalism for an interacting Fermi sea and the local density approximation to
translate results from nuclear matter to finite nuclei. In addition we also
consider effects from rho-meson renormalization in the nucleus. The use of
nucleon Green's functions in terms of their spectral functions offers a precise
way to account for Fermi motion and binding. On the other hand the use of many
body Feynman diagrams in a relativistic framework allows one to avoid using
prescriptions given in the past to introduce relativistic corrections in a non
relativistic formalism. We show that with realistic nucleon spectral functions
and meson nucleus selfenergies one can get a reasonable description of the EMC
effect for x > 0.15, outside the shadowing region.


title: NN Potentials from Nonlinear Quantum Field Theory

abstract:
  We investigate self-interacting scalar, pseudoscalar and vector meson fields
and their influence on NN interactions. Due to the self--interaction one has to
solve nonlinear field equations which allow solitary wave solutions. A
propability amplitude for the propagation of these solutions is calculated
which can be applied in a One-Boson-Exchange Potential (OBEP). Using proper
normalization as an alternative to the usual renormalization scheme one obtains
amplitudes with the same momentum dependence as the conventional
Feynman-propagators multiplied with the form factors of the Bonn-B OBEP. From
this the usage of form factors might be replaced by the application of solitary
wave exchange. In addition the parameters entering the different meson
propagators show a connection in form of a simple scaling law which relates all
parameters to the pion self-interaction coupling constant.


title: Parity Violation and the Nucleon-Nucleon System

abstract:
  The status of the field of nuclear parity violation---both experimental and
theoretical---is reviewed, with special emphasis on those results which have
been obtained since the 1985 review article by Adelberger and Haxton.


title: The (e,e'p) Reaction and the Transition to the Eikonal Regime

abstract:
  The reliability of the models describing the Final-State Interactions (FSI)
in (e,e$'$p) scattering at high proton energies is an important issue in view
of the experiments planned at CEBAF. One of the most popular approaches
adopted, the Glauber method, involves the linearization of the wave equation
for the ejected proton travelling through the residual nucleus. We have studied
the consequences of such an assumption for the case of the
$^{12}\mathrm{C(e,e}'\mathrm{p)}^{11}\hbox{\rm B}^*$ reaction at high proton
momenta by comparing the results with the predictions obtained when the
second-order differential equation for the proton wave is solved exactly for
each partial wave. We find that the two methods give well-correlated angular
distributions for momenta in the range 1-4 GeV/c, i.e. for kinematics relevant
to the transition to the eikonal regime.


title: Valid QCD Sum Rules for Vector Mesons in Nuclear Matter

abstract:
  QCD sum rules for vector mesons (rho, omega, phi) in nuclear matter are
reexamined with an emphasis on the reliability of various sum rules. Monitoring
the continuum contribution and the convergence of the operator product
expansion plays a crucial role in determining the validity of a sum rule. The
uncertainties arising from less than precise knowledge of the condensate values
and other input parameters are analyzed via a Monte-Carlo error analysis. Our
analysis leaves no doubt that vector-meson masses decrease with increasing
density. This resolves the current debate over the behavior of the vector-meson
masses and the sum rules to be used in extracting vector meson properties in
nuclear matter. We find a ratio of rho-meson masses of $m_{\rho^*}/m_\rho =
0.78\pm0.08$ at nuclear matter saturation density.


title:
Statistical properties of antisymmetrized molecular dynamics for
  non-nucleon-emission and nucleon-emission processes

abstract:
  Statistical properties of the antisymmetrized molecular dynamics (AMD) are
classical in the case of nucleon emission processes, while they are quantum
mechanical for the processes without nucleon emission. We first clarify that
there coexist mutually opposite two statistics in the AMD framework: One is the
classical statistics of the motion of wave packet centroids and the other is
the quantum statistics of the motion of wave packets which is described by the
AMD wave function. We prove the classical statistics of wave packet centroids
by using the framework of the microcanonical ensemble of the nuclear system. We
show that the quantum statistics of wave packets emerges from the classical
statistics of wave packet centroids. It is emphasized that the temperature of
the classical statistics of wave packet centroids is different from the
temperature of the quantum statistics of wave packets. We then explain that the
statistical properties of AMD for nucleon emission processes are classical
because nucleon emission processes in AMD are described by the motion of wave
packet centroids. When we improve the description of the nucleon emission
process so as to take into account the momentum fluctuation due to the wave
packet spread, the AMD statistical properties for nucleon emission processes
change drastically into quantum statistics. Our study of nucleon emission
processes can be conversely regarded as giving another kind of proof of the
fact that the statistics of wave packets is quantum mechanical while that of
wave packet centroids is classical.


title: Photoproduction of Etas and N$^*$(1535) Electrostrong Properties

abstract:
  From the new Mainz data of eta photoproduction off protons\cite{ref1} and
deuterons\cite{ref2}, we can extract, via the effective Lagrangian approach
(ELA)\cite{ref3}, the electrostrong parameters $\xi_{p}$ and $\xi_{n}$ for the
N$^*$(1535) excitation. These parameters are, in units of $10^{-4} MeV^{-1}$,
$(2.20\pm 0.15)$ and $(-1.86\pm 0.20)$ respectively. They yield the ratio of
the helicity amplitudes for the excitation of N$^*$(1535) by photons off
neutrons and protons to be $A^{n}_{1/2}/A^{p}_{1/2}=-0.84\pm 0.15$, a quantity
of fundamental importance in the baryon structure. Best estimates in the quark
model are close to this ratio.


title: The Weak Parity-Violating Pion-Nucleon Coupling (Revised)

abstract:
  We use QCD sum rules to obtain the weak parity-violating pion-nucleon
coupling constant $f_{\pi NN}$. We find that $f_{\pi NN}\approx 2\times
10^{-8}$, about an order of magnitude smaller than the ``best estimates'' based
on quark models. This result follows from the cancellation between perturbative
and nonperturbative QCD processes not found in quark models, but explicit in
the QCD sum rule method. Our result is consistent with the experimental upper
limit found from $^{18}$F parity-violating measurements.


title: 1/N_c- expansion of the quark condensate at finite temperature

abstract:
  Previously the quark and meson properties in a many quark system at finite
temperature have been studied within effective QCD approaches in the Hartree
approximation. In the present paper we consider the influence of the mesonic
correlations on the quark self-energy and on the quark propagator within a
systematic $1/N_c$- expansion. Using a general separable ansatz for the
nonlocal interaction, we derive a selfconsistent equation for the $1/N_c$
correction to the quark propagator. For a separable model with cut-off
formfactor, we obtain a decrease of the condensate of the order of 20\% at zero
temperature. A lowering the critical temperature for the onset of the chiral
restoration transition due to the inclusion of mesonic correlations is obtained
what seems to be closer to the results from lattice calculations.


title: Coulomb potential from a particle in uniform ultrarelativistic motion

abstract:
  The Coulomb potential produced by an ultrarelativistic particle (such as a
heavy ion) in uniform motion is shown in the appropriate gauge to factorize
into a longitudinal Dirac delta function of (z - t) times the simple two
dimensional potential solution in the transverse direction. This form makes
manifest the source of the energy independence of the interaction.


title:
$A$--Dependence of $\Lambda\Lambda$ Bond Energies in Double---$\Lambda$
  Hypernuclei

abstract:
  The $A$-dependence of the bond energy $\Delta B_{\Lambda\Lambda}$ of the
${\Lambda\Lambda}$ hypernuclear ground states is calculated in a three-body
${\Lambda + \Lambda + {^{A}Z}}$ model and in the Skyrme-Hartree-Fock approach.
Various ${\Lambda\Lambda}$ and $\Lambda$-nucleus or ${\Lambda N}$ potentials
are used and the sensitivity of $\Delta B_{\Lambda\Lambda}$ to the interactions
is discussed. It is shown that in medium and heavy ${\Lambda\Lambda}$
hypernuclei, $\Delta B_{\Lambda\Lambda}$ is a linear function of
$r_{\Lambda}^{-3}$, where $r_\Lambda$ is rms radius of the hyperon orbital. It
looks unlikely that it will be possible to extract ${\Lambda\Lambda}$
interaction from the double-$\Lambda$ hypernuclear energies only, the
additional information about the $\Lambda$-core interaction, in particular, on
$r_{\Lambda}$ is needed.


title: Consistent Construction of Realistic One-Body Density Matrix in Nuclei

abstract:
  A phenomenological method based on the natural orbital representation is
applied to construct the ground state one-body density matrix which describes
correctly both density and momentum distributions in $^{4}He$, $^{16}O$ and
$^{40}Ca$ nuclei. The parameters of the matrix are fixed by a best fit to the
experimental density distribution and to the correlated nucleon momentum
distribution. The method allows the natural orbitals, the occupation
probabilities and the depletion of the Fermi sea to be obtained. Ground-state
characteristics of $^{4}He$, $^{16}O$ and $^{40}Ca$ nuclei, such as rms radii
and mean kinetic energies are calculated, as well.


title: New QCD Sum Rules for Nucleons in Nuclear Matter

abstract:
  Two new QCD sum rules for nucleons in nuclear matter are obtained from a
mixed correlator of spin-1/2 and spin-3/2 interpolating fields. These new sum
rules, which are insensitive to the poorly known four-quark condensates,
provide additional information on the nucleon scalar self-energy. These new sum
rules are analyzed along with previous spin-1/2 interpolator-based sum rules
which are also insensitive to the poorly known four-quark condensates. The
analysis indicates consistency with the expectations of relativistic nuclear
phenomenology at nuclear matter saturation density. However, a weaker density
dependence near saturation is suggested. Using previous estimates of in-medium
condensate uncertainties, we find $M^* = 0.64^{+0.13}_{-0.09}$ GeV and
$\Sigma_v = 0.29^{+0.06}_{-0.10}$ GeV at nuclear matter saturation density.


title: Delta excitation in antiproton-deutron annihilation

abstract:
  The $\Delta$-excitation in $\overline{p}d$ annihilation at rest was studied.
The annihilation amplitude from the statistical model and the $\pi N$ amplitude
from the resonance model were adopted in our calculations. We analyze the
invariant mass of the $\pi^+p$ and $\pi^-p$ systems selecting the protons with
momenta above 400 MeV/c and with respect to the different final reaction
channels. Our model reproduces reasonably the experimental data.


title:
Nucleon and pion electromagnetic structure and constituent quark form
  factors

abstract:
  We have evaluated nucleon and pion electromagnetic form factors using for the
first time eigenfunctions of a light-front mass operator, reproducing a large
set of energy levels, and constituent quark form factors in the one-body
current. The comparison with the experimental data yields valuable information
on the electromagnetic structure of light constituent quarks and on the
different role played by their Dirac and Pauli form factors.


title: Restoration of Overlap Functions and Spectroscopic Factors in Nuclei

abstract:
  An asymptotic restoration procedure is applied for analyzing bound--state
overlap functions, separation energies and single--nucleon spectroscopic
factors by means of a model one--body density matrix emerging from the Jastrow
correlation method in its lowest order approximation for $^{16}O$ and $^{40}Ca$
nuclei . Comparison is made with available experimental data and mean--field
and natural orbital representation results.


title:
Correlated $\pi\pi$ and $K\bar K$ exchange in the baryon-baryon
  interaction

abstract:
  A dynamical model for correlated two-pion and two-kaon exchange in the
baryon- baryon interaction is presented, both in the scalar-isoscalar
($\sigma$) and the vector-isovector ($\rho$) channel. The correlations between
the two pseudoscalar mesons are taken into account by means of $\pi\pi - K\bar
K$ amplitudes derived from a meson-exchange model, which is in line with the
empirical $\pi\pi$ data. It is found that correlated $K\bar K$ exchange plays
an important role in the $\sigma$-channel for baryon-baryon states with non-
vanishing strangeness. The strength of correlated $\pi\pi$ plus $K\bar K$
exchange in the $\sigma$-channel decreases with the strangeness of the baryon-
baryon system becoming more negative. The results for correlated $\pi\pi$-
exchange in the vector-isovector channel deviate from what is expected in the
naive SU(3) picture for genuine $\rho$-exchange. Shortcomings of a simplified
description in terms of sharp mass $\sigma$- and $\rho$-exchange are pointed
out.


title: Electromagnetic Form Factors of Charged and Neutral Kaons

abstract:
  The charged and neutral kaon form factors are calculated as a
phenomenological application of the QCD Dyson-Schwinger equations. The results
are compared with the pion form factor calculated in the same framework and
yield \mbox{$F_{K^\pm}(Q^2) > F_{\pi^\pm}(Q^2)$} on
\mbox{$Q^2\in[0,3]$~GeV$^2$}; and a neutral kaon form factor that is similar in
form and magnitude to the neutron charge form factor. These results are
sensitive to the difference between the kaon and pion Bethe-Salpeter amplitude
and the $u$- and $s$-quark propagation characteristics.


title: Multipole analysis of spin observables in vector meson photoproduction

abstract:
  A multipole analysis of vector meson photoproduction is formulated as a
generalization of the pseudoscalar meson case. Expansion of spin observables in
the multipole basis and behavior of these observables near threshold and
resonances are examined.


title: An Analysis of the Use of the Cluster Separability in Scattering Theory

abstract:
  In the framework of the Time Dependent Scattering Theory we discuss three
forms of Cluster Separability as well as the conditions for the representation
of the scattering system dynamics implied by their respective use.


title: Photoproduction of $\eta$-mesons off protons and deuterons

abstract:
  An effective field theory with hadrons and photons is constructed, where the
hadronic parameters are determined by fitting elastic $\pi$N scattering data.
The predicted pion-induced $\eta$-production on the nucleon agrees well with
the data. The hadronic model is then used to describe the final-state
interaction in photoinduced processes. We present a consistent description of
pion photoproduction in the E$_0^+$-channel and of the total cross sections for
photoinduced $\eta$-production on the proton as well as on the deuteron.


title: Low-energy QCD: Chiral coefficients and the quark-quark interaction

abstract:
  A detailed investigation of the low-energy chiral expansion is presented
within a model truncation of QCD. The truncation allows for a phenomenological
description of the quark-quark interaction in a framework which maintains the
global symmetries of QCD and permits a $1/N_c$ expansion. The model dependence
of the chiral coefficients is tested for several forms of the quark-quark
interaction by varying the form of the running coupling, $\alpha (q^2)$, in the
infrared region. The pattern in the coefficients that arises at tree level is
consistent with large $N_c$ QCD, and is related to the model truncation.


title:
Nucleon-Nucleon Correlations and Multiquark Cluster Effects in Deep
  Inelastic Electron Scattering off Few-Nucleon Systems at $x>1$

abstract:
  Inclusive $A(e,e')X$ and semi-inclusive $A(e,e'N)X$ deep inelastic electron
scattering processes off few-nucleon systems are investigated at $x > 1$,
showing some of the relevant features of the cross section which are sensitive
to the effects arising from nucleon-nucleon correlations and possible exotic
multiquark cluster configurations at short internucleon separations.


title:
Where is the Baseline for Color Transparency Studies with Moderate
  Energy Electron Beams?

abstract:
  Study of color transparency (CT) effects at moderate energies is more
problematic than is usually supposed. Onset of CT can be imitated by other
mechanisms, which contain no explicit QCD dynamics. In the case of the
$(e,e'p)$ reaction the standard inelastic shadowing well known in the pre-QCD
era, causes a substantial growth of nuclear transparency with $Q^2$ and a
deviation from the Glauber model, analogous to what is assumed to be a signal
of CT.
  In the case of exclusive virtual photoproduction of vector mesons, CT is
expected to manifest itself as an increase of nuclear transparency with $Q^2$
in production of the ground states and as an abnormal nuclear enhancement for
the radial excitations. We demonstrate that analogous $Q^2$-dependence can be
caused at moderate energies by the variation of so called coherence length,
which is an interference effect, even in the framework of the vector dominance
model.
  One should disentangle the real and the mock CT effects in experiments
planned at CEBAF, at the HERMES spectrometer, or at the future electron
facility ELFE.


title:
Nuclear Compton scattering in the $\Delta$-resonance region with
  polarized photons

abstract:
  Nuclear Compton scattering in the $\Delta$-resonance region is reconsidered
within the framework of the $\Delta$-hole model. The different role of the
resonant and non-resonant contributions to the transition amplitudes is
discussed and their effect is investigated by comparing the results of
calculation with recent data also taken with polarized photons.


title: Parity-violating alpha-decay of the 3.56-MeV J,T=0+,1 state of Li-6

abstract:
  We study the parity-violating alpha+d decay of the lowest 0+ state of Li-6 in
a microscopic three-cluster model. The initial bound and the final scattering
states are described consistently within the same model. The parity-violating
decay width is calculated in perturbation theory using the parity-nonconserving
nucleon-nucleon interaction of Desplanques, Donoghue, and Holstein (DDH). We
find that the decay width is sensitive to dynamical degrees of freedom which
are beyond the alpha+p+n model, for example, alpha excitation and breakup. In
our full model, which contains breathing excitations of the alpha particle and
H-3 + He-3 rearrangement, the parity-nonconserving decay width is
Gamma=3.97x10^{-9} eV, using the DDH coupling constants.


title:
Recovering Relativistic Nuclear Phenomenology from the Quark-Meson
  Coupling Model

abstract:
  The quark-meson coupling (QMC) model for nuclear matter, which describes
nuclear matter as non-overlapping MIT bags bound by the self-consistent
exchange of scalar and vector mesons is modified by the introduction of a
density dependent bag constant. The density dependence of the bag constant is
related to that of the in-medium effective nucleon mass through a scaling
ansatz suggested by partial chiral symmetry restoration in nuclear matter. This
modification overcomes drawbacks of the QMC model and leads to the recovery of
the essential features of relativistic nuclear phenomenology. This suggests
that the modification of the bag constant in the nuclear medium may play an
important role in low- and medium-energy nuclear physics.


title: Pion flow and antiflow in relativistic heavy-ion collisions

abstract:
  Within the framework of a relativistic transport model (ART) for heavy-ion
collisions at AGS energies, we study the transverse flow of pions with respect
to that of nucleons using two complementary approaches. It is found that in
central collisions pions develop a weak flow as a result of the flow of baryon
resonances from which they are produced. On the other hand, they have a weak
antiflow in peripheral collisions due to the shadowing of spectators.
Furthermore, it is shown that both pion flow and antiflow are dominated by
those with large transverse momenta.


title:
Electromagnetic Structure of Mesons in a Light-Front Constituent Quark
  Model

abstract:
  The elastic and transition electromagnetic form factors of mesons are
investigated within a light-front constituent quark model. The general formulae
for the space-like matrix elements of the one-body component of the
electromagnetic current, including both Dirac and Pauli form factors of the
constituent quarks, are presented. Our results for the pion charge form factor
and the $\pi \rho$ transition form factor are reported and compared with those
obtained within various relativistic approaches in a range of values of the
four-momentum transfer accessible to $CEBAF$.


title:
Non-adiabatic effect in electron screening in fusion reactions at
  astrophysical energies

abstract:
  We calculate the electron screening effect in low energy nuclear fusion
reactions by taking non-adiabaticity of the tunnleing process into account. In
order to investigate deviations from the adiabatic limit, we use the dynamical
norm method, which has recently been developed by the present authors. Using
$d$+D reaction as an example, we show that the screening energy never exceeds
those estimated in the adiabatic approximation. Our calculations indicate that
the non-adiabatic effect is important both in classically allowed and
classically forbidden processes.


title: Program for Generating Tables of SU(3) Coupling Coefficients

abstract:
  A C-Language program which tabulates the isoscalar factors and Clebsch-Gordan
coefficients for products of representations in SU(3) is presented. These are
efficiently computed using recursion relations, and the results are presented
in exact precision as square roots of rational numbers. Output is in LaTeX
format.


title:
Further application of a semi-microscopic core-particle coupling method
  to the properties of Gd155,157, and Dy159

abstract:
  In a previous paper a semi-microscopic core-particle coupling method that
includes the conventional strong coupling core-particle model as a limiting
case, was applied to spectra and electromagnetic properties of several
well-deformed odd nuclei. This work, coupled a large single-particle space to
the ground state bands of the neighboring even cores. In this paper, we
generalize the theory to include excited bands of the cores, such as beta and
gamma bands, and thereby show that the resulting theory can account for the
location and structure of all bands up to about 1.5 MeV.


title: Direct Neutron Capture for Magic-Shell Nuclei

abstract:
  In neutron capture for magic--shell nuclei the direct reaction mechanism can
be important and may even dominate. As an example we investigated the reaction
$^{48}$Ca(n,$\gamma)^{49}$Ca for projectile energies below 250\,keV in a direct
capture model using the folding procedure for optical and bound state
potentials. The obtained theoretical cross sections are in agreement with the
experimental data showing the dominance of the direct reaction mechanism in
this case. The above method was also used to calculate the cross section for
$^{50}$Ca(n,$\gamma)^{51}$Ca.


title: Analysis of Chiral Mean-Field Models for Nuclei

abstract:
  An analysis of nuclear properties based on a relativistic energy functional
containing Dirac nucleons and classical scalar and vector meson fields is
discussed. Density functional theory implies that this energy functional can
include many-body effects that go beyond the simple Hartree approximation.
Using basic ideas from effective field theory, a systematic truncation scheme
is developed for the energy functional, which is based on an expansion in
powers of the meson fields and their gradients.
  Chiral models are analyzed by considering specific lagrangians that realize
the spontaneously broken chiral symmetry of QCD in different ways and by
studying them at the Hartree level. Models that include a light scalar meson
playing a dual role as the chiral partner of the pion and the mediator of the
intermediate-range nucleon-nucleon interaction, and which include a
"Mexican-hat" potential, fail to reproduce basic ground-state properties of
nuclei. In contrast, chiral models with a nonlinear realization of the symmetry
are shown to contain the full flexibility inherent in the general energy
functional and can therefore successfully describe nuclei.


title: Salty Water Cerenkov Detectors

abstract:
  The addition of certain solutes to a water Cerenkov detector will introduce
new charge-current channels for the detection of $\nu_e$s. The experimental
conditions necessary to exploit such signals - large volumes and very low
backgrounds - should be reached for the first time in SuperKamiokande and SNO.
I compare some of the more attractive possibilities ($^7$Li, $^{11}$B,
$^{35}$Cl) in terms of counting rate, reliability of the cross section,
specificity of signal, and potential for distinguishing competing solutions to
the solar neutrino puzzle.


title: RPA Description of the Electric Polarizability of the Nucleon

abstract:
  Excited states of the nucleon are described as RPA configurations on a
mean--field ground state taken from the MIT bag model. A residual interaction
of a structure as in the Nambu--Jona--Lasinio model is used. The particle-hole
states are coupled to good total angular momentum and isospin. Valence
excitations of particle-hole type and quark--antiquark ($q\overline{q}$) states
from the Dirac--sea are included. The dependence of the baryon spectrum and
multipole response functions on the coupling constant $G$ is studied. At
critical values of $G$ the 3q--ground state becomes degenerate with strongly
collective $q\overline{q}$ modes. The model is used to calculate the electric
polarizability of the neutron $\alpha_N$. Without residual interaction
$\alpha_N=7\cdot 10^{-4}fm^3$ is found. With residual interaction the value
increases to $\alpha_N=(7-11)\cdot 10^{-4}fm^3$. The measured value of
$\alpha_N$ is reproduced within experimental error bars.


title: New QCD Sum Rules for In-Medium Nucleons

abstract:
  New QCD sum rules for nucleons in nuclear matter are derived from a mixed
correlation function of spin-1/2 and spin-3/2 interpolating fields. These sum
rules allow a determination of the scalar self-energy of the nucleon
independent of the poorly known four-quark condensates. An analysis of these
new sum rules in concert with previous nucleon sum rules from spin-1/2
interpolators indicates consistency with the expectations of relativistic
mean-field phenomenology. We find $M^* = 0.68 \pm 0.08$ GeV and $\Sigma_v =
0.31 \pm 0.06$ GeV at nuclear matter saturation density.


title:
Signal for supernova $\nu_\mu$ and $\nu_\tau$ neutrinos in water
  \v{C}erenkov detectors

abstract:
  We suggest that photons with energies between 5 and 10 MeV, generated by the
($\nu,\nu'p\gamma$) and ($\nu,\nu'n\gamma$) reactions on $^{16}$O, constitute a
signal which allows a unique identification of supernova $\nu_\mu$ and
$\nu_\tau$ neutrinos in water \v{C}erenkov detectors. We calculate the yield of
such $\gamma$ events and estimate that a few hundred of them would be detected
in Superkamiokande for a supernova at 10 kpc distance.


title: Can Plane Wave Modes be Physical Modes in Soliton Models?

abstract:
  I show that plane waves may not be used as asymptotic states in soliton
models because they describe unphysical states. When asymptotic states are
taken to be physical there is no T-matrix of $\cO(1)$.


title: Quantum Solitons Lead to Yukawa Coupling

abstract:
  Recently, it was shown that zero modes in semiclassical soliton models do not
lead to Yukawa couplings. We show that taking into account the contributions of
the quantum soliton into the renormalization scheme, which cannot be done in
semiclassical treatments, leads to a Yukawa coupling. A similar analysis should
be possible for the Skyrmion, renewing the hope, that this model will lead to a
correct description of hadron physics.


title:
Limits of Time-Reversal Violating Interaction from Compound Nuclear
  Experiments

abstract:
  Mean square matrix elements of the time reversal invariance violating (TRIV)
interaction between the compound nuclear states are calculated within the
statistical model, using the explicit form of the TRIV interaction via the
$\rho$-meson exchange. From the comparison of the calculated values with the
data known for $p+ ^{27}Al \Leftrightarrow ^{24}Mg + \alpha$ reaction, and for
$\gamma$-correlation measurements in $^{113}Cd(n,\gamma)^{114}Cd$ process, the
bounds on the TRIV constant are obtained ${\bar g}_{\rho} \alt 1.8 \times
10^{-2}$ and ${\bar g}_{\rho} \alt 1.1 \times 10^{-2}$. The sensitivity of the
recently proposed detailed balance test experiments on isolated resonances in
$^{32}S$ to the value of ${\bar g}_{\rho}$ is shown to be as high as to reach
values ${\bar g}_{\rho} \sim 10^{-4}$.


title: Roper Excitation in Alpha-Proton Scattering

abstract:
  We study the Roper excitation in the $(\alpha,\alpha')$ reaction. We consider
all processes which may be relevant in the Roper excitation region, namely,
Roper excitation in the target, Roper excitation in the projectile, and double
$\Delta$ excitation processes. The theoretical investigation shows that the
Roper excitation in the proton target mediated by an isoscalar exchange is the
dominant mechanism in the process. We determine an effective isoscalar
interaction by means of which the experimental cross section is well
reproduced. This should be useful to make predictions in related reactions and
is a first step to construct eventually a microscopic $NN \rightarrow NN^*$
transition potential, for which the present reaction does not offer enough
information.


title: Z=110--111 Elements and the Stability of Heavy and Superheavy Elements

abstract:
  The recent discovery of isotopes with Z=110--111 suggests evidence for (1) a
monopole--monopole interaction that does not appear explicitly in
Nilsson--Strutinsky mass systematics, and (2) a competition between $SU(2)$ and
$SU(3)$ dynamical symmetries that has been predicted for this region. Our
calculations suggest that these new isotopes are near spherical, and may
represent a true island of superheavy nuclei, but shifted downward in neutron
number by these new physical effects.


title:
Deep Inelastic Lepton Scattering in Nuclei at x > 1 and the Nucleon
  Spectral Function

abstract:
  The nuclear structure function F_2A(x) has been studied in the Bjorken limit
for (l, l') scattering on nuclei in the region of x > 1 and was found to be
very sensitive to the information contained in the nucleon spectral function in
nuclei, particularly the correlations between momenta and energies in the
region of large momenta. Calculations were done in a local density
approximation using two different spectral functions for nuclear matter.
Results are compared to those obtained for a spectral function which has been
evaluated directly for the finite nucleus, ^{16}O, under consideration. For
values of x around 1.5 and larger the quasiparticle contribution is negligible,
thus stressing the sensitivity of the present reaction to the dynamical
properties of nuclei beyond the shell model approach. Several approximations
which are usually employed in studies of the EMC effect have been analyzed and
their inaccuracy in this region is demonstrated. The results stress the fact
that the nuclear structure function contains important information on nuclear
dynamical correlations. Therefore further measurements of F_2A(x) in that
region and for many nuclei would be most welcome.


title:
The Nucleon Spectral Function at Finite Temperature and the Onset of
  Superfluidity in Nuclear Matter

abstract:
  Nucleon selfenergies and spectral functions are calculated at the saturation
density of symmetric nuclear matter at finite temperatures. In particular, the
behaviour of these quantities at temperatures above and close to the critical
temperature for the superfluid phase transition in nuclear matter is discussed.
It is shown how the singularity in the thermodynamic T-matrix at the critical
temperature for superfluidity (Thouless criterion) reflects in the selfenergy
and correspondingly in the spectral function. The real part of the on-shell
selfenergy (optical potential) shows an anomalous behaviour for momenta near
the Fermi momentum and temperatures close to the critical temperature related
to the pairing singularity in the imaginary part. For comparison the selfenergy
derived from the K-matrix of Brueckner theory is also calculated. It is found,
that there is no pairing singularity in the imaginary part of the selfenergy in
this case, which is due to the neglect of hole-hole scattering in the K-matrix.
From the selfenergy the spectral function and the occupation numbers for finite
temperatures are calculated.


title: Amplitude ambiguities in pseudoscalar meson photoproduction

abstract:
  We consider the problem of determining amplitudes from observables for the
case of pseudoscalar meson photoproduction. We find a number of surprisingly
simple constraints which give necessary conditions for a complete set of
measurements. These results contradict one of the selection rules derived
previously.


title: Do we have three $S_{11}$ resonances in the second resonance region?

abstract:
  We review the status of the $S_{11}$ N$^*$ resonances in light of some recent
theoretical and phenomenological results. Whereas the quark model predicts two
such resonances around 1.6 GeV, there is considerable evidence for a third
$S_{11}$ resonance in this energy range. This suggests that a $K\Sigma$ or
$K\Lambda$ quasi-bound state may indeed exist below the kaon production
threshold. We show that kaon production experiments, in particular $K^0$
photoproduction off nucleons, would be very sensitive to the existence of the
third $S_{11}$ resonance.


title: Nucleation Rate of Hadron Bubbles in Baryon-Free Quark-Gluon Plasma

abstract:
  We evaluate the factor $\kappa$ appearing in Langer's expression for the
nucleation rate extended to the case of hadron bubbles forming in zero baryon
number cooled quark-gluon plasma. We consider both the absence and presence of
viscosity and show that viscous effects introduce only small changes in the
value of $\kappa$


title:
Spectral Decorrelation of Nuclear Levels in the Presence of Continuum
  Decay

abstract:
  The fluctuation properties of nuclear giant resonance spectra are studied in
the presence of continuum decay. The subspace of quasi-bound states is
specified by one-particle one-hole and two-particle two-hole excitations and
the continuum coupling is generated by a scattering ensemble. It is found that,
with increasing number of open channels, the real parts of the complex
eigenvalues quickly decorrelate. This appears to be related to the transition
from power-law to exponential time behavior of the survival probability of an
initially non-stationary state.


title:
Meson-meson correlations in baryon-baryon and antibaryon-baryon
  interactions

abstract:
  Recent work of the J\"ulich group about the role of meson-meson correlations
in baryon-baryon and antibaryon-baryon interactions is reviewed.


title: Charm Correlation as a Diagnostic Probe of Quark Matter

abstract:
  The use of correlation between two open-charm mesons is suggested to give
information about the nature of the medium created in heavy-ion collisions.
Insensitivity to the charm production rate is achieved by measuring normalized
cumulant. The acollinearity of the D momenta in the transverse plane is a
measure of the medium effect. Its dependence on nuclear size or E_T provides a
signature for the formation of quark matter.


title:
Microscopic Structure of High-Spin Vibrational Excitations in
  Superdeformed 190,192,194Hg

abstract:
  Microscopic RPA calculations based on the cranked shell model are performed
to investigate the quadrupole and octupole correlations for excited
superdeformed bands in 190Hg, 192Hg, and 194Hg. The K=2 octupole vibrations are
predicted to be the lowest excitation modes at zero rotational frequency. At
finite frequency, however, the interplay between rotation and vibrations
produces different effects depending on neutron number: The lowest octupole
phonon is rotationally aligned in 190Hg, is crossed by the aligned
two-quasiparticle bands in 192Hg, and retains the K=2 octupole vibrational
character up to the highest frequency in 194Hg. The gamma vibrations are
predicted to be higher in energy and less collective than the octupole
vibrations. From a comparison with the experimental dynamic moments of inertia,
a new interpretation of the observed excited bands invoking the K=2 octupole
vibrations is proposed, which suggests those octupole vibrations may be
prevalent in SD Hg nuclei.


title:
On the Staggering Effect of Dynamical Moments of Inertia in
  Superdeformed Bands

abstract:
  The possibility of the appearance of the C$_{4}$ symmetry in the rotational
bands is studied within the particle-rotor model. Allowing for a slight
triaxiality of the rotor it is shown that the lowest states of the system for a
sufficiently high spin possess the symmetry which allows to distinguish states
differing by two units of angular momentum.


title: Nuclear Flow in Consistent Boltzmann Algorithm Models

abstract:
  We investigate the stochastic Direct Simulation Monte Carlo method (DSMC) for
numerically solving the collision-term in heavy-ion transport theories of the
Boltzmann-Uehling-Uhlenbeck (BUU) type. The first major modification we
consider is changes in the collision rates due to excluded volume and
shadowing/screening effects (Enskog theory). The second effect studied by us is
the inclusion of an additional advection term. These modifications ensure a
non-vanishing second virial and change the equation of state for the scattering
process from that of an ideal gas to that of a hard-sphere gas. We analyse the
effect of these modifications on the calculated value of directed nuclear
collective flow in heavy ion collisions, and find that the flow slightly
increases.


title: Nuclear Production of Charmonium at ELFE Energies

abstract:
  I discuss the diffractive production of charmonium from nuclei and the
anomalous nuclear attenuation --- termed ``color transparency'' --- attributed
to such processes, focusing on the few tens of GeV energy regime germane to the
ELFE project. A critical review of color transparency calculations is
presented, and the major sources of uncertainty are emphasized.


title:
Nuclear correlation and finite interaction-range effects in high-energy
  $(e,e'p)$ nuclear transparency

abstract:
  Nuclear transparency is calculated for high-energy, semi-inclusive $(e,e'p)$
reactions, by accounting for all orders of Glauber multiple-scattering and by
using realistic finite-range $p N$ interaction and (dynamically and
statistically) correlated nuclear wave functions. The nuclear correlation
effect is reduced due to the $p N$ finite-range effect. The net effect is
small, and depends sensitively on details of the nuclear correlations in finite
nuclei, which are poorly known at present.


title:
Mean-field description of ground-state properties of drip-line nuclei:
  Pairing and continuum effects

abstract:
  Ground-state properties of exotic even-even nuclei with extreme
neutron-to-proton ratios are described in the framework of the self-consistent
mean-field theory with pairing formulated in coordinate space. This theory
properly accounts for the influence of the particle continuum, which is
particularly important for weakly bound systems. The pairing properties of
nuclei far from stability are studied with several interactions emphasizing
different aspects, such as the range and density dependence of the effective
interaction. Measurable consequences of spatially extended pairing fields are
presented, and the sensitivity of the theoretical predictions to model details
is discussed.


title: 3D Solution of Hartree-Fock-Bogoliubov Equations for Drip-Line Nuclei

abstract:
  We investigate the possibility of describing triaxial quadrupole deformations
for nuclei close to the two-neutron drip line by the Hartree-Fock Bogoliubov
method taking into account resonances in the continuum. We use a Skyrme
interaction to describe the Hartee-Fock hamiltonian and a density-dependent
zero-range interaction to evaluate the pairing field. The mean-field equations
are solved in a three-dimensional cubic mesh. We study the stability of the
two-neutron separation energies and of the description of the nuclear surface
as a function of the number of active mean-field orbitals and of the size of
the mesh. The even Ni isotopes are used as a test case and the accuracy as a
function of quadrupole deformation is studied by performing constrained
calculations. A first application to the study of the two-neutron separation
energies in Ni isotopes up to the drip line is presented.


title: Symmetry Breaking for Rho Meson in Neutron Matter

abstract:
  Qualitative changes in the collective excitation spectra of the $\rho$-meson
triplet in neutron matter is studied, with particular emphasis on the breaking
of the discrete $p\leftrightarrow n$ symmetry. The appearance of additional
branches in the dispersion characteristics, the mass splitting among the charge
states, the splitting between longitudinal and transverse modes of the
$\rho^{\pm}$ mesons and the appearance of `island' modes (or loops) in the
time-like region are some of the features that are exposed.


title: QCD Scales in Finite Nuclei

abstract:
  The role of QCD scales and chiral symmetry in finite nuclei is examined. The
Dirac-Hartree mean-field coupling constants of Nikolaus, Hoch, and Madland
(NHM) are scaled in accordance with the QCD-based prescription of Manohar and
Georgi. Whereas the nine empirically-based coupling constants of NHM span
thirteen orders of magnitude, the scaled coupling constants are almost all {\it
natural}, being dimensionless numbers of order one. We speculate that this
result provides good evidence that QCD and chiral symmetry apply to finite
nuclei.


title: Strange Neutral Currents in Nuclei

abstract:
  We examine the effects on the nuclear neutral current Gamow-Teller (GT)
strength of a finite contribution from a polarized strange quark sea. We
perform nuclear shell model calculations of the neutral current GT strength for
a number of nuclei likely to be present during stellar core collapse. We
compare the GT strength when a finite strange quark contribution is included to
the strength without such a contribution. As an example, the process of neutral
current nuclear de-excitation via $\nu {\overline{\nu}}$ pair production is
examined for the two cases.


title:
Limit on T-Violating P-Conserving $\rho N N$ Interaction from the
  $\gamma$ Decay of $^{57}$Fe

abstract:
  We use the experimental limit on the interference of M1 and E2 multipoles in
the $\gamma$-decay of $^{57}$Fe to bound the time-reversal-violating
parity-conserving $\rho N N$ vertex. Our approach is a large-basis shell-model
calculation of the interference. We find an upper limit on the parameter
$\bar{g}_{\rho}$, the relative strength of the T-violating $\rho N N$ vertex,
of close to $10^{-2}$, a value similar to the best limits from other kinds of
experiments.


title: Quark Delocalization, Color Screening and Dibaryons

abstract:
  The quark delocalization and color screening model, a quark potential model,
is used for a systematic search of dibaryon candidates in the $u,d$ and $s$
three flavor world. Color screening which appears in unquenched lattice gauge
calculations and quark delocalization (which is similar to electron
delocalization in molecular physics) are both included. Flavor symmetry
breaking and channel coupling effects are studied. The model is constrained not
only by baryon ground state properties but also by the $N$-$N$ scattering phase
shifts. The deuteron and zero energy di-nucleon resonance are both reproduced
qualitatively. The model predicts two extreme types of dibaryonic systems:
``molecular'' like the deuteron, and highly delocalized six-quark systems among
which only a few narrow dibaryon resonances occur in the $u,d$ and $s$ three
flavor world. Possible high spin dibaryon resonances are emphasized.


title:
Energy Loss, Electron Screening, and the Astrophysical 3He(d,p)4He cross
  section

abstract:
  We reanalyze the low-energy 3He(d,p)4He cross section measurements of
Engstler et al. using recently measured energy loss data for proton and
deuteron beams in a helium gas. Although the new 3He(d,p)4He S-factors are
significantly lower than those reported by Engstler et al. they clearly show
the presence of electron screening effects. From the new S-factors we find an
electron screening energy in agreement with the adiabatic limit.


title: Quantum Algebraic Symmetries in Nuclear and Molecular Physics

abstract:
  Various applications of quantum algebraic techniques in nuclear structure
physics and molecular physics are briefly reviewed. Contains 81 references.


title: Quantum Algebras in Nuclear Structure

abstract:
  Quantum algebras are a mathematical tool which provides us with a class of
symmetries wider than that of Lie algebras, which are contained in the former
as a special case. After a self-contained introduction to the necessary
mathematical tools ($q$-numbers, $q$-analysis, $q$-oscillators, $q$-algebras),
the su$_q$(2) rotator model and its extensions, the construction of deformed
exactly soluble models (Interacting Boson Model, Moszkowski model), the use of
deformed bosons in the description of pairing correlations, and the symmetries
of the anisotropic quantum harmonic oscillator with rational ratios of
frequencies, which underly the structure of superdeformed and hyperdeformed
nuclei, are discussed in some detail. A brief description of similar
applications to molecular structure and an outlook are also given.


title:
Towards a New Strategy of Searching for QCD Phase Transition in Heavy
  Ion Collisions

abstract:
  We reconsider the Hung and Shuryak arguments in favour of searching for the
deconfinement phase transition in heavy ion collisions {\em downward} from the
nominal SPS energy, at $E_{lab} \approx 30 \ GeV/A$ where the fireball lifetime
is the longest one. Using the recent lattice QCD data and the mixed phase
model, we show that the deconfinement transition might occur at the bombarding
energies as low as $E_{lab}=3 - 5 \ GeV/A$. Attention is drawn to the study of
the mixed phase of nuclear matter in the collision energy range $E_{lab}= 2-10
\ GeV/A$.


title: Second Order Phase Transitions : From Infinite to Finite Systems

abstract:
  We investigate the Equation of State (EOS) of classical systems having 300
and 512 particles confined in a box with periodic boundary conditions. We show
that such a system, independently on the number of particles investigated, has
a critical density of about 1/3 the ground state density and a critical
temperature of about $2.5~ MeV$. The mass distribution at the critical point
exhibits a power law with $\tau = 2.23$. Making use of the grand partition
function of Fisher's droplet model, we obtain an analytical EOS around the
critical point in good agreement with the one extracted from the numerical
simulations.


title:
Model for Resonance Enhancement of P- and T-noninvariant Effects in
  Neutron Reactions

abstract:
  We consider a simplified model for resonant neutron-nucleus interaction with
coupled channels. An analytical solution is given for two coupled channels and
arbitrary neutron orbital momentum. A case of a week channel coupling,
corresponding to narrow Breit-Wigner resonance, is analyzed in details. As far
as the total width of a resonance coincides with the neutron width, the model
is directly appropriate only for light nuclei. We study a mixing of two narrow
s- and p-wave resonances by P- and P-,T-noninvariant potentials in the first
order of perturbation theory. As an example a close-lying pair of s- and p-wave
resonances of the $^{35}$Cl nucleus is considered. The favorable possibilities
are shown to exist on thick targets for measurements beyond the resonance
widths. In particular, an interference minimum near s-wave resonance is of
interest for P-odd neutron spin rotation on light spinless nuclei.


title:
Inelastic nucleon contributions in $(e,e^\prime)$ nuclear response
  functions

abstract:
  We estimate the contribution of inelastic nucleon excitations to the
$(e,e^\prime)$ inclusive cross section in the CEBAF kinematic range.
Calculations are based upon parameterizations of the nucleon structure
functions measured at SLAC. Nuclear binding effects are included in a
vector-scalar field theory, and are assumed have a minimal effect on the
nucleon excitation spectrum. We find that for $q\lsim 1$ GeV the elastic and
inelastic nucleon contributions to the nuclear response functions are
comparable, and can be separated, but with roughly a factor of two uncertainty
in the latter from the extrapolation from data. In contrast, for $q\rsim 2$ GeV
this uncertainty is greatly reduced but the elastic nucleon contribution is
heavily dominated by the inelastic nucleon background.


title:
Study of the nucleon-induced preequilibrium reactions in terms of the
  Quantum Molecular Dynamics

abstract:
  The preequilibrium (nucleon-in, nucleon-out) angular distributions of
$^{27}$Al, $^{58}$Ni and $^{90}$Zr have been analyzed in the energy region from
90 to 200 MeV in terms of the Quantum Moleculear Dynamics (QMD) theory. First,
we show that the present approach can reproduce the measured (p,xp') and (p,xn)
angular distributions leading to continuous final states without adjusing any
parameters. Second, we show the results of the detailed study of the
preequilibrium reaction processes; the step-wise contribution to the angular
distribution, comparison with the quantum-mechanical Feshbach-Kerman-Koonin
theory, the effects of momentum distribution and surface refraction/reflection
to the quasifree scattering. Finally, the present method was used to assess the
importance of multiple preequilibrium particle emission as a function of
projectile energy up to 1 GeV.


title: Chiral Perturbation Approach to the pp -> pp pi0 Reaction Near Threshold

abstract:
  The usual theoretical treatments of the near-threshold $pp \rightarrow
pp\pi^0$ reaction are based on various phenomenological Lagrangians. In this
work we examine the relationship between these approaches and a systematic
chiral perturbation method. Our chiral perturbation calculation indicates that
the pion rescattering term should be significantly enhanced as compared with
the traditional phenomenological treatment, and that this term should have
substantial energy and momentum dependence. An important consequence of this
energy-momentum dependence is that, for a representative threshold kinematics
and within the framework of our semiquantitative calculation, the rescattering
term interferes destructively with the Born-term in sharp contrast to the
constructive interference obtained in the conventional treatment. This
destructive interference makes theoretical cross sections for $pp \rightarrow
pp\pi^0$ much smaller than the experimental values, a feature that suggests the
importance of the heavy-meson exchange contributions to explain the
experimental data.


title: Charm Production in Flux Tubes

abstract:
  We argue that the non-perturbative Schwinger mechanism may play an important
role in the hadronic production of charm. We present a flux tube model which
assumes that the colliding hadrons become color charged because of gluon
exchange, and that a single non-elementary flux tube is built up as they
recede. The strong chromoelectric field inside this tube creates quark pairs
(including charmed ones) and the ensuing color screening breaks the tube into
excited hadronic clusters. On their turn these clusters, or `fireballs', decay
statistically into the final hadrons. The model is able to account for the soft
production of charmed, strange and lighter hadrons within a unified framework.


title: Macroscopic Features of Light Heavy-Ion Fission Reactions

abstract:
  Global macroscopic features observed in the fully-damped binary processes in
light di-nuclear systems, such as limiting angular momenta, mean total kinetic
energies and energy thresholds for fusion-fission processes (''fission
thresholds") are presented. Their deduced systematics are consistent with that
obtained for heavier systems and follow a fusion-fission picture which can be
described by a realistic rotating liquid drop model considering diffuse-surface
and finite-nuclear-range effects.


title: Relativistic Hamiltonians in many-body theories

abstract:
  We discuss the description of a many-body nuclear system using Hamiltonians
that contain the nucleon relativistic kinetic energy and potentials with
relativistic corrections. Through the Foldy-Wouthuysen transformation, the
field theoretical problem of interacting nucleons and mesons is mapped to an
equivalent one in terms of relativistic potentials, which are then expanded at
some order in 1/m_N. The formalism is applied to the Hartree problem in nuclear
matter, showing how the results of the relativistic mean field theory can be
recovered over a wide range of densities.


title: Monte Carlo computation of pair correlations in excited nuclei

abstract:
  We present a novel quantum Monte Carlo method based on a path integral in
Fock space, which allows to compute finite-temperature properties of a
many-body nuclear system with a monopole pairing interaction in the canonical
ensemble. It enables an exact calculation of the thermodynamic variables such
as the internal energy, the entropy, or the specific heat, from the measured
moments of the number of hops in a path of nuclear configurations. Monte Carlo
calculations for a single-shell $(h_{11/2})^6$ model are consistent with an
exact calculation from the many-body spectrum in the seniority model.


title:
Lattice gas model for fragmentation: From Argon on Scandium to Gold on
  Gold

abstract:
  The recent fragmentation data for central collisions of Gold on Gold are even
qualitatively different from those for central collisions of Argon on Scandium.
The latter can be fitted with a lattice gas model calculation. Effort is made
to understand why the model fails for Gold on Gold. The calculation suggests
that the large Coulomb interaction which is operative for the larger system is
responsible for this discrepancy. This is demonstrated by mapping the lattice
gas model to a molecular dynamics calculation for disassembly. This mapping is
quite faithful for Argon on Scandium but deviates strongly for Gold on Gold.
The molecular dynamics calculation for disassembly reproduces the
characteristics of the fragmentation data for both Gold on Gold and Argon on
Scandium.


title: Introduction to Chiral Symmetry

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


title: Variational calculation of antiprotonic helium atoms

abstract:
  A few per cent fraction of antiprotons stopped in helium survives for an
enormous time (up to tens of microseconds) in comparison with the usual
lifetime ($10^{-12}s$) of these particles in matter. The explanation is that
antiprotons are captured in the metastable antiprotonic helium atoms $^{3,4}\!
H\! e\bar pe$ carrying an extremely large total angular momentum $L\sim 30-40$.
Initial populations, level lifetimes and very precise values of the transition
energies were obtained in experiments on the resonant laser--induced
annihilation. Analogous long-lived systems were observed in experiments with
negative kaons and pions.
  The purpose of this report is to present the results of calculation of
eigenenergies, radiative transition rates, energy-level splitting due to
relativistic interactions and Auger decay rates of antiprotonic helium atoms
within the variational approach.


title: An Effective Lagrangian Approach to Nuclei

abstract:
  The construction of a general effective lagrangian consistent with the
symmetries of QCD and intended for applications to finite-density systems is
discussed. The low-energy structure of the composite nucleon is described
within the theory from vector-meson dominance. Results are given for finite
nuclei and nuclear matter at one-loop order. All of the coupling constants,
appropriately defined according to naive dimensonal analysis, are found to be
natural.


title:
Hypermatter - Properties and Formation in Relativistic Nuclear
  Collisions

abstract:
  The extension of the Periodic System into hitherto unexplored domains -
antimatter and hypermatter - is discussed. Starting from an analysis of hyperon
and single hypernuclear properties we investigate the structure of
multi-hyperon objects (MEMOs) using an extended relativistic meson field
theory. These are contrasted with multi-strange quark states (strangelets).
Their production mechanism is studied for relativistic collisions of heavy ions
from present day experiments at AGS and SPS to future opportunities at RHIC and
LHC. It is pointed out that absolutely stable hypermatter is unlikely to be
produced in heavy ion collisions. New attention should be focused on short
lived metastable hyperclusters ($\tau \propto 10^{-10}$s) and on intensity
interferometry of multi-strange-baryon correlations.


title:
An Effective Lagrangian with Broken Scale and Chiral Symmetry II: Pion
  Phenomenology

abstract:
  We extend an effective Lagrangian embodying broken scale and chiral symmetry
to include explicit chiral symmetry breaking and an additional chiral invariant
term which allows for an axial coupling constant greater than unity. We also
include a chiral Lagrangian for the isotriplet vector mesons which leads to a
renormalization of the pion field. The properties of nuclear matter and nuclei,
low energy $\pi N$ scattering and the behavior of quantities such as the pion
mass and axial coupling at finite density are discussed.


title: Ion Collisions in Very Strong Electric Fields

abstract:
  A Classical Trajectory Monte Carlo (CTMC) simulation has been made of
processes of charge exchange and ionization between an hydrogen atom and fully
stripped ions embedded in very strong static electric fields ($O(10^{10}$
V/m$)$), which are thought to exist in cosmic and laser--produced plasmas.
Calculations show that the presence of the field affects absolute values of the
cross sections, enhancing ionization and reducing charge exchange. Moreover,
the overall effect depends upon the relative orientation between the field and
the nuclear motion. Other features of a null-field situation, such as scaling
laws, are revisited.


title:
Isoscalar Roper Excitation in $p(\alpha, \alpha')$ Reactions in the $10
  - 15$ $GeV$ Region

abstract:
  Recent experiments at Saturne at $4$ $GeV$ showed that the $(\alpha,\alpha')$
reaction on the proton shows two distinctive peaks, which were associated to
$\Delta$ projectile excitation and Roper target excitation. A subsequent
theoretical analysis has shown that this picture is qualitatively correct but
there are important interference effects between the two mechanisms.
Futhermore, at this energy the ratio of strengths for the Roper and $\Delta$
peak is about $1/4$. In the present paper we show that by going to the $10 -
15$ $GeV$ region the interference effects become negligible, the signal for the
Roper excitation is increased by more than an order of magnitude and the ratio
of cross sections at the peaks for Roper and $\Delta$ excitation becomes of the
order of unity, thus making this range of energies ideal for studies of
isoscalar Roper excitation.


title:
The $p p \to p p\pi^0$ Reaction near Threshold: A Chiral Power Counting
  Approach

abstract:
  We use power-counting arguments as an organizing principle to apply chiral
perturbation theory, including an explicit $\Delta$, to the $p p \rightarrow p
p \pi^0$ reaction near threshold. There are two lowest-order leading mechanisms
expected to contribute to the amplitude with similar magnitudes: an impulse
term, and a $\Delta$-excitation mechanism. We examine formally sub-leading but
potentially large mechanisms, including pion-rescattering and short-ranged
contributions. We show that the pion-rescattering contribution is enhanced by
off-shell effects and has a sign opposite to that of a recent estimate based on
a PCAC pion interpolating field. Our result is that the impulse term interferes
destructively with the pion rescattering and $\Delta$-excitation terms. In
addition, we have modeled the short-ranged interaction using $\sigma$ and
$\omega$ exchange mechanisms. A recoil correction to the impulse approximation
is small. The total amplitude obtained including all of these processes is
found to yield cross sections substantially smaller than the measured ones.


title: Isospin dependent effective interaction in nucleon-nucleus scattering

abstract:
  The isospin-dependent component of the effective nucleon-nucleon interaction
that causes the $\Delta T=1$ (p, p') and (p, n) reactions off nuclei is
studied. It is shown that the corrections to the impulse approximation comes
from the $g$-matrix type correction and the rearrangement term. They are
numerically estimated with the isospin-asymmetric nuclear-matter reaction
matrix approach. The analysis of the isobaric analog transitions
${}^{42}$Ca(p,n)${}^{42}$Sc and ${}^{48}$Ca(p,n)${}^{48}$Sc are presented.


title: Classical and Quantal Irregular Scatterings with Complex Target

abstract:
  One-dimensional scattering by a target with two internal degrees of freedom
is investigated. The damping of resonance peaks and the associated appearance
of the fluctuating background in the quantum inelastic scattering amplitudes
are found. Examination of the analog classical system reveals a disorderly
reaction function, which is then related to the quantum amplitude through a
semiclassical argument.


title: Nuclear Mass Dependence of Chaotic Dynamics in Ginocchio Model

abstract:
  The chaotic dynamics in nuclear collective motion is studied in the framework
of a schematic shell model which has only monopole and quadrupole degrees of
freedom. The model is shown to reproduce the experimentally observed global
trend toward less chaotic motion in heavier nuclei. The relation between
current approach and the earlier studies with bosonic models is discussed.

categories: nucl-th chao-dyn nlin.CD nucl-ex quant-ph


title: Response Function of Asymmetric Nuclear Matter

abstract:
  The charge longitudinal response function is examined in the framework of the
random-phase approximation in an isospin-asymmetric nuclear matter where proton
and neutron densities are different. This asymmetry changes the response
through both the particle-hole interaction and the free particle-hole
polarization propagator. We discuss these two effects on the response function
on the basis of our numerical results in detail.


title: Electron screening in molecular fusion reactions

abstract:
  Recent laboratory experiments have measured fusion cross sections at
center-of-mass energies low enough for the effects of atomic and molecular
electrons to be important. To extract the cross section for bare nuclei from
these data (as required for astrophysical applications), it is necessary to
understand these screening effects. We study electron screening effects in the
low-energy collisions of Z=1 nuclei with hydrogen molecules. Our model is based
on a dynamical evolution of the electron wavefunctions within the TDHF scheme,
while the motion of the nuclei is treated classically. We find that at the
currently accessible energies the screening effects depend strongly on the
molecular orientation. The screening is found to be larger for molecular
targets than for atomic targets, due to the reflection symmetry in the latter.
The results agree fairly well with data measured for deuteron collisions on
molecular deuterium and tritium targets.


title:
Momentum Distribution in Nuclear matter within a Perturbation
  Approximation

abstract:
  It is shown that the norm corrections, introduced to avoid the violation of
the constraints on the depletion of the hole states in the standard
perturbative 2p2h approach, leads in nuclear matter to a dependence of the
momentum distribution with the total nucleon number. This unphysical behavior,
which in turn makes the depletion to be non-extensive, arises from
contributions of disconnected diagrams contained in the norm. It is found that
the extensivity is again recovered when the 4p4h excitations in the ground
state are included, and a reasonable value for the total number of nucleons
promoted above the Fermi level is obtained.


title: The electron-nucleon cross section in $(e,e'p)$ reactions

abstract:
  We examine commonly used approaches to deal with the scattering of electrons
from a bound nucleon. Several prescriptions are shown to be related by gauge
transformations. Nevertheless, due to current non-conservation, they yield
different results. These differences reflect the size of the uncertainty that
persists in the interpretation of $(e,e'p)$ experiments.


title: Quasifree Eta Photoproduction from Nuclei

abstract:
  Quasifree $\eta$ photoproduction from nuclei is studied in the Distorted Wave
Impulse Approximation (DWIA). The elementary eta production operator contains
Born terms, vector meson and nucleon resonance contributions and provides an
excellent description of the recent low energy Mainz measurements on the
nucleon. The resonance sector includes the $S_{11}(1535)$, $P_{11}(1440)$ and
$D_{13}(1520)$ states whose couplings are fixed by independent electromagnetic
and hadronic data. Different models for the $\eta N$ t-matrix are used to
construct a simple $\eta A$ optical potential based on a $t
\rho$-approximation. We find that the exclusive $A(\gamma,\eta N)B$ process can
be used to study medium modifications of the $N^*$ resonances, particularly if
the photon asymmetry can be measured. The inclusive $A(\gamma, \eta)X$ reaction
is compared to new data obtained on $^{12}C$, $^{40}Ca$, and is found to
provide a clear distinction between different models for the $\eta N$ t-matrix.


title: On the Coupling of the $\eta $ Meson to the Nucleon

abstract:
  The pseudoscalar and pseudovector $\eta N$ coupling constants are calculated
from an effective vertex associated with the $a_0(980)\pi N$ triangle diagram.
The predicted values are in agreement with the ones concluded from fitting
$\eta $ photoproduction amplitudes. In this context we stress the importance of
the properties of the scalar meson octet for $\eta $ meson physics.


title: Green Function Monte Carlo Method for Excited States of Quantum System

abstract:
  A novel scheme to solve the quantum eigenvalue problem through the
imaginary-time Green function Monte Carlo method is presented. This method is
applicable to the excited states as well as to the ground state of a generic
system. We demonstrate the validity of the method with the numerical examples
on three simple systems including a discretized sine-Gordon model.


title: Six-quark configurations in the NN system correlated with experiment

abstract:
  The nucleon-nucleon interaction at short range is analyzed in terms of
six-quark configurations on a base of numerical solutions of modified RGM
equations. It is shown that in low partial waves L=0,1 the system has a
two-channel character: the $NN$ channel and the inner six-quark state ("bag")
with specific color-spin structure. Starting from this analysis it is shown
that polarization observables could be a good tool for investigation of a quark
structure of the deuteron.


title:
Equivalent Photon Approach to Simultaneous Excitation in Heavy Ion
  Collision

abstract:
  We apply the Equivalent Photon Approximation to calculate cross sections for
the simultaneous excitation of two heavy ions in relativistic collisions. We
study especially the excitation of two nuclei to a 1- - state and show that the
equations are symmetric with respect to both ions. We also examine the limit in
which the excitation energy of one of the nuclei goes to zero, which gives the
elastic case. Finally a few remarks about the limits of this approach are made.


title:
Rho Mesons in Asymmetric Nuclear Matter: A Renormalization Group
  Approach

abstract:
  The running of the $\rho\bar N N$ couplings in presence of nuclear matter is
studied, and the relevant $\beta$-functions are shown to be different for
$\rho^0$ and $\rho^+$, when the nuclear medium is asymmetric.


title: Dirac-Fock Current and Magnetic-Moment in the Relativistic Approach

abstract:
  We define the Dirac-Fock current to hold the current conservation in the
momentum-dependent Dirac fields, and discuss its effect on the magnetic-moment
in the nuclear matter. It is shown that the Dirac-Fock current can largely
reduce the magnetic-moment even in the isovector case, whose value has been too
big due to the small effective mass in the usual relativistic Hartree
approximation.


title:
Antisymmetrized molecular dynamics of wave packets with stochastic
  incorporation of Vlasov equation

abstract:
  On the basis of the antisymmetrized molecular dynamics (AMD) of wave packets
for the quantum system, a novel model (called AMD-V) is constructed by the
stochastic incorporation of the diffusion and the deformation of wave packets
which is calculated by Vlasov equation without any restriction on the one-body
distribution. In other words, the stochastic branching process in molecular
dynamics is formulated so that the instantaneous time evolution of the averaged
one-body distribution is essentially equivalent to the solution of Vlasov
equation. Furthermore, as usual molecular dynamics, AMD-V keeps the many-body
correlation and can naturally describe the fluctuation among many channels of
the reaction. It is demonstrated that the newly introduced process of AMD-V has
drastic effects in heavy ion collisions of 40Ca + 40Ca at 35 MeV/nucleon,
especially on the fragmentation mechanism, and AMD-V reproduces the
fragmentation data very well. Discussions are given on the interrelation among
the frameworks of AMD, AMD-V and other microscopic models developed for the
nuclear dynamics.


title: Phenomenological Aspects of Isospin Violation in the Nuclear Force

abstract:
  Phenomenological Lagrangians and dimensional power counting are used to
assess isospin violation in the nucleon-nucleon force. The $\pi NN$ coupling
constants (including the Goldberger-Treiman discrepancy), charge-symmetry
breaking, and meson-mixing models are examined. A one-loop analysis of the
isospin-violating $\pi NN$ coupling constants is performed using chiral
perturbation theory. Meson-mixing models and the $^3$He - $^3$H mass difference
are also discussed in the context of naturalness.


title:
Relativistic Effects in the Transverse Flow in the Molecular Dynamics
  Framework

abstract:
  In order to investigate relativistic effects we compare the transverse flow
calculated by using the four versions of the QMD approaches with that of the
full covariant RQMD approach. From the comparison we conclude that the
simplified RQMD (RQMD/S), which uses the common time coordinate to all
particles, can be used instead of RQMD up to 6 GeV/u.


title:
Scaling Properties of Hadron Production in the Ising Model for
  Quark-Hadron Phase Transition

abstract:
  Earlier study of quark-hadron phase transition in the Ginzberg-Landau theory
is reexamined in the Ising model, so that spatial fluctuations during the
transition can be taken into account. Although the dimension of the physical
system is 2, as will be argued, both d=2 and d=4 Ising systems are studied, the
latter being theoretically closer to the Ginzberg-Landau theory. The normalized
factorial moments F_q are used to quantify multiplicity fluctuations, and the
scaling exponent \nu is used to characterize the scaling properties. It is
found by simulation on the Ising lattice that \nu becomes a function of the
temperature T near T_c. The average value of \nu over a range of T<T_c agrees
with the value of 1.3 derived analytically from the Ginzberg-Landau theory.
Thus the implications of the mean-field theory are not invalidated by either
the introduction of spatial fluctuations or the restriction to a 2D system.


title: Nuclear Forces and Chiral Theories

abstract:
  Recent successes in {\it ab initio} calculations of light nuclei (A=2-6) will
be reviewed and correlated with the dynamical consequences of chiral symmetry.
The tractability of nuclear physics evinced by these results is evidence for
that symmetry. The relative importance of three-nucleon forces, four-nucleon
forces, multi-pion exchanges, and relativistic corrections will be discussed in
the context of effective field theories and dimensional power counting. Isospin
violation in the nuclear force will also be discussed in this context.


title: Dimensional Regularization and Nuclear Potentials

abstract:
  It is shown how nucleon-nucleon potentials can be defined in N dimensions,
using dimensional regularization to continue amplitudes. This provides an easy
way to separate out contact ($\delta$-function) terms arising from
renormalization. An example is worked out several ways for the case of two
scalar particles exchanged between nucleons, which involves a very simple loop
calculation. This leads to a Feynman-parameterized representation for the
nucleon-nucleon potential. Alternately, a dispersion representation can be
developed leading to a different, though equivalent, form.


title: Effects of Short Range Correlations on Ca Isotopes

abstract:
  The effect of Short Range Correlations (SRC) on Ca isotopes is studied using
a simple phenomenological model. Theoretical expressions for the charge
(proton) form factors, densities and moments of Ca nuclei are derived. The role
of SRC in reproducing the empirical data for the charge density differences is
examined. Their influence on the depletion of the nuclear Fermi surface is
studied and the fractional occupation probabilities of the shell model orbits
of Ca nuclei are calculated. The variation of SRC as function of the mass
number is also discussed.


title:
Remarks about spin measurements in $\bar{\rm p}{\rm p} \to
  \overline{\Lambda}{\Lambda}$

abstract:
  We comment on the proposed measurement of the spin-depolarisation parameter
$D_{nn}$ in the strangeness-exchange reaction $\bar{\rm p}{\rm p} \rightarrow
\overline{\Lambda}{\Lambda}$. It is shown that the existing data on the
correlation coefficients $C_{ij}$ limit the range allowed for $D_{nn}$.


title: Delta Decay in Nuclear Medium

abstract:
  Proton-nucleus collisions, where the beam proton gets excited to the delta
resonance and then decays to p$\pi ^+$, either inside or outside the nuclear
medium, are studied. Cross-sections for various kinematics for the (p,p$' \pi
^+$) reaction between 500 MeV and 1 GeV beam energy are calculated to see the
effects of the nuclear medium on the propagation and decay of the resonance.
The cross-sections studied include proton energy spectra in coincidence with
the pion, four momentum transfer distributions, and the invariant p$\pi^+$ mass
distributions. We find that the effect of the nuclear medium on these
cross-sections mainly reduces their magnitudes. Comparing these cross-sections
with those considering the decay of the delta outside the nucleus only, we
further find that at 500 MeV the two sets of cross-sections have large
differences, while by 1 GeV the differences between them become much smaller.


title:
Shell Model Study of the Double Beta Decays of $^{76}$Ge, $^{82}$Se and
  $^{136}$Xe

abstract:
  The lifetimes for the double beta decays of $^{76}$Ge, $^{82}$Se and
$^{136}$Xe are calculated using very large shell model spaces. The two neutrino
matrix elements obtained are in good agreement with the present experimental
data. For $<m_{\nu}><1$ eV we predict the following upper bounds to the
half-lives for the neutrinoless mode: $T^{(0\nu)}_{1/2}(Ge) > 1.85\,10^{25}
yr.$, $T^{(0\nu)}_{1/2}(Se) > 2.36\,10^{24} yr.$ and $T^{(0\nu)}_{1/2}(Xe) >
1.21\,10^{25} yr$. These results are the first from a new generation of Shell
Model calculations reaching O(10$^{8}$) dimensions.


title:
Dilepton anisotropy from $p + Be$ and $Ca + Ca$ collisions at BEVALAC
  energies

abstract:
  A full calculation of lepton-pair angular characteristics is carried out for
$e^+e^-$ pairs created in $p + Be$ and $Ca + Ca$ collisions from 1.0 to 2.1
GeV/A. It is demonstrated that the dilepton decay anisotropy depends
sensitively on the different sources and may be used for their disentangling.
Due to the dominance of the $\eta$-and $\Delta$-Dalitz decays and only a small
anisotropy coefficient for $\pi^+\pi^-$ annihilation, the expected anisotropy
coefficients show a decrease with invariant mass of the dilepton pair and
change only moderately when comparing $p + Be$ and $Ca + Ca$ reactions at the
same bombarding energy.


title: Modeling Cluster Production at the AGS

abstract:
  Deuteron coalescence, during relativistic nucleus-nucleus collisions, is
carried out in a model incorporating a minimal quantal treatment of the
formation of the cluster from its individual nucleons by evaluating the overlap
of intial cascading nucleon wave packets with the final deuteron wave function.
In one approach the nucleon and deuteron center of mass wave packet sizes are
estimated dynamically for each coalescing pair using its past light-cone
history in the underlying cascade, a procedure which yields a parameter free
determination of the cluster yield. A modified version employing a global
estimate of the deuteron formation probability, is identical to a general
implementation of the Wigner function formalism but can differ from the most
frequent realisation of the latter. Comparison is made both with the extensive
existing E802 data for Si+Au at 14.6 GeV/c and with the Wigner formalism. A
globally consistent picture of the Si+Au measurements is achieved. In light of
the deuteron's evident fragility, information obtained from this analysis may
be useful in establishing freeze-out volumes and help in heralding the presence
of high-density phenomena in a baryon-rich environment.


title:
Coulomb Breakup Mechanism of Neutron-Halo Nuclei in a Time-Dependent
  Method

abstract:
  The mechanism of the Coulomb breakup reactions of the nuclei with
neutron-halo structure is investigated in detail. A time-dependent
Schr\"odinger equation for the halo neutron is numerically solved by treating
the Coulomb field of a target as an external field. The momentum distribution
and the post-acceleration effect of the final fragments are discussed in a
fully quantum mechanical way to clarify the limitation of the intuitive picture
based on the classical mechanics. The theory is applied to the Coulomb breakup
reaction of $^{11}$Be + $^{208}$Pb. The breakup mechanism is found to be
different between the channels of $j^{\pi}=\frac{1}{2}^{-}$ and
$\frac{3}{2}^{-}$, reflecting the underlying structure of $^{11}$Be. The
calculated result reproduces the energy spectrum of the breakup fragments
reasonably well, but explains only about a half of the observed longitudinal
momentum difference.