title:
Physics of Coulomb Corrections in Hanbury-Brown Twiss Interferometry in
  Ultrarelativistic Heavy Ion Collisions

abstract:
  We discuss the elementary physics of the final state Coulomb interactions in
Hanbury-Brown Twiss interferometry, showing -- with explicit comparison to E877
data for $\pi^+\pi^-$ and $\pi^\pm p$ -- that the Coulomb corrections in the
pair correlation function can be well understood in terms of simple classical
physics. We connect the classical picture with descriptions in terms of Coulomb
wave functions, and investigate the influence of the ``central'' Coulomb
potential on the pair correlation function.


title: Four-Alpha Linear-Chain States in 16O

abstract:
  We study 4$\alpha$ linear-chain states in 16O in comparison with 3$\alpha$
states in 12C by using the Generator Coordinate Method within a microscopic
$N\alpha$-cluster model. It is shown to be very important to solve relative
motion of $\alpha$-clusters by taking into account the orthogonality between
the linear-chain states and other low-lying states including the ground state.
For 12C, the 3$\alpha$ chain state disappears because of this orthogonality.
The $4\alpha$ chain state in 16O, on the other hand, is hardly affected by
low-lying states and persists to remain above the 4$\alpha$ threshold. The
calculated moment of inertia of the $4\alpha$ linear-chain rotational band (88
keV) reproduces the experimentally suggested value qualitatively.


title:
Probing the Fifth State of Matter with Relativistic Heavy Ions: A
  Theoretical Overview

abstract:
  I review the current status of lattice Monte-Carlo computations of the
equation of state of QCD, our current understanding of the thermalization
process at collider energies, and two new theoretical developments, one
pertaining to the ab-initio calculation of the low-$x$ gluon structure of heavy
nuclei, the other to the chaotic behavior of QCD. At the end I give a brief
overview of the status of various quark-gluon plasma signatures.


title: Inclusive versus Exclusive EM Processes in Relativistic Nuclear Systems

abstract:
  Connections are explored between exclusive and inclusive electron scattering
within the framework of the relativistic plane-wave impulse approximation,
beginning with an analysis of the model-independent kinematical constraints to
be found in the missing energy--missing momentum plane. From the interplay
between these constraints and the spectral function basic features of the
exclusive and inclusive nuclear responses are seen to arise. In particular, the
responses of the relativistic Fermi gas and of a specific hybrid model with
confined nucleons in the initial state are compared in this work. As expected,
the exclusive responses are significantly different in the two models, whereas
the inclusive ones are rather similar. By extending previous work on the
relativistic Fermi gas, a reduced response is introduced for the hybrid model
such that it fulfills the Coulomb and the higher-power energy-weighted sum
rules. While incorporating specific classes of off-shellness for the struck
nucleons, it is found that the reducing factor required is largely
model-independent and, as such, yields a reduced response that is useful for
extracting the Coulomb sum rule from experimental data. Finally, guided by the
difference between the energy-weighted sum rules of the two models, a version
of the relativistic Fermi gas is devised which has the 0$^{\rm th}$, 1$^{\rm
st}$ and 2$^{\rm nd}$ moments of the charge response which agree rather well
with those of the hybrid model: this version thus incorporates {\em a priori}
the binding and confinement effects of the stuck nucleons while retaining the
simplicity of the original Fermi gas.


title: Threshold Production of the Hypertriton

abstract:
  The cross section for threshold production of the hypertriton in the reaction
pd->^3_\Lambda H K^+ is calculated in a two-step model and compared to the
break-up process pd -> d\LambdaK^+. The latter process is shown to be dominant
already at 2 MeV above threshold. The amplitude squared at threshold for the pd
-> ^3_\Lambda H K^+ reaction is |f|^2 = 1.0 nb/sr.


title: Semiclassical Expansion for the Angular Momentum

abstract:
  After reviewing the WKB series for the Schr\"odinger equation we calculate
the semiclassical expansion for the eigenvalues of the angular momentum
operator. This is the first systematic semiclassical treatment of the angular
momentum for terms beyond the leading torus approximation.


title:
Microscopic description of light unstable nuclei with the stochastic
  variational method

abstract:
  The structure of the light proton and neutron rich nuclei is studied in a
microscopic multicluster model using the stochastic variational method. This
approach enables us to describe the weakly bound nature of these nuclei in a
consistent way. Applications for various nuclei $^{6-9}$Li, $^7$Be, $^8$B,
$^9$C, $^{9-10}$Be, $^{9-10}$B presented. The paper discusses the relation of
this model to other models as well as the possible extension for p and sd shell
nuclei.


title: Nuclear Transparency to Intermediate-Energy Protons

abstract:
  Nuclear transparency in the (e,e'p) reaction for 135 < Tp < 800 MeV is
investigated using the distorted wave approximation. Calculations using
density-dependent effective interactions are compared with phenomenological
optical potentials. Nuclear transparency is well correlated with proton
absorption and neutron total cross sections. For Tp < 300 MeV there is
considerable sensitivity to the choice of optical model, with the empirical
effective interaction providing the best agreement with transparency data. For
Tp > 300 MeV there is much less difference between optical models, but the
calculations substantially underpredict transparency data and the discrepancy
increases with A. The differences between Glauber and optical model
calculations are related to their respective definitions of the semi-inclusive
cross section. By using a more inclusive summation over final states the
Glauber model emphasizes nucleon-nucleon inelasticity, whereas with a more
restrictive summation the optical model emphasizes nucleon-nucleus
inelasticity; experimental definitions of the semi-inclusive cross section lie
between these extremes.


title: Relations between fusion cross sections and average angular momenta

abstract:
  We study the relations between moments of fusion cross sections and averages
of angular momentum. The role of the centrifugal barrier and the target
deformation in determining the effective barrier radius are clarified. A simple
method for extracting average angular momentum from fusion cross sections is
demonstrated using numerical examples as well as actual data.


title:
Nuclear Clusters as a Probe for Expansion Flow in Heavy Ion Reactions at
  10-15AGeV

abstract:
  A phase space coalescence description based on the Wigner-function method for
cluster formation in relativistic nucleus-nucleus collisions is presented. The
momentum distributions of nuclear clusters d,t and He are predicted for central
Au(11.6AGeV)Au and Si(14.6AGeV)Si reactions in the framework of the RQMD
transport approach. Transverse expansion leads to a strong shoulder-arm shape
and different inverse slope parameters in the transverse spectra of nuclear
clusters deviating markedly from thermal distributions. A clear ``bounce-off''
event shape is seen: the averaged transverse flow velocities in the reaction
plane are for clusters larger than for protons. The cluster yields
--particularly at low $p_t$ at midrapidities-- and the in-plane (anti)flow of
clusters and pions change if suitably strong baryon potential interactions are
included. This allows to study the transient pressure at high density via the
event shape analysis of nucleons, nucleon clusters and other hadrons.


title:
Polarization Phenomena in Small-Angle Photoproduction of e+e- Pairs and
  the GDH Sum Rule

abstract:
  We discuss a possibility to measure the spin-dependent part of the forward
Compton scattering amplitude through interference effects of the Bethe-Heitler
and virtual Compton scattering mechanisms in photoproduction of e+e- pairs at
small angles.


title: Photoabsorption on nuclei

abstract:
  We calculate the total photoabsorption cross section on nuclei in the energy
range from 300 MeV to 1 GeV within the framework of a semi-classical phase
space model. Besides medium modifications like Fermi motion and Pauli blocking
we focus on the collision broadening of the involved resonances. The resonance
contributions to the elementary cross section are fixed by fits to partial wave
amplitudes of pion photoproduction. The cross sections for $N \, R \to N \, N$,
needed for the calculation of collision broadening, are obtained by detailed
balance from a fit to $N \, N \to N \, N \, \pi$ cross sections. We show that a
reasonable collision broadening is not able to explain the experimentally
observed disappearance of the $D_{13}(1520)$-resonance in the photoabsorption
cross section on nuclei.


title: Neutron and proton spectra from the decay of $\Lambda$ hypernuclei

abstract:
  We have determined the spectra of neutrons and protons following the decay of
$\Lambda$ hypernuclei through the one- and two-nucleon induced mechanisms. The
momentum distributions of the primary nucleons are calculated and a Monte Carlo
simulation is used to account for final state interactions. From the spectra we
calculate the number of neutrons ($N_n$) and protons ($N_p$) per $\Lambda$
decay and show how the measurement of these quantities, particularly $N_p$, can
lead to a determination of $\Gamma_n / \Gamma_p$, the ratio of neutron to
proton induced $\Lambda$ decay. We also show that the consideration of the
two-nucleon induced channel has a repercussion in the results, widening the
band of allowed values of $\Gamma_n / \Gamma_p$ with respect to what is
obtained neglecting this channel.


title:
Non-collapsing quasiparticle random phase approximation for nuclear
  double-beta decay

abstract:
  We show how the longstanding problem of the collapse of the charge-exchange
QRPA near the physical value of the force strength can be circumvented. This is
done by including the effect of ground state correlations into the QRPA
equations of motion. The corresponding formalism, called renormalized QRPA, is
briefly outlined and its consequences are discussed in the framework of a
schematic model for the two-neutrino double beta decay in the $^{100}Mo
\rightarrow\, ^{100}Ru$ system. The question of the conservation of the Ikeda
sum rule is also addressed within the new formalism.


title: Suppression of core polarization in halo nuclei

abstract:
  We present a microscopic study of halo nuclei, starting from the Paris and
Bonn potentials and employing a two-frequency shell model approach. It is found
that the core-polarization effect is dramatically suppressed in such nuclei.
Consequently the effective interaction for halo nucleons is almost entirely
given by the bare G-matrix alone, which presently can be evaluated with a high
degree of accuracy. The experimental pairing energies between the two halo
neutrons in $^6$He and $^{11}$Li nuclei are satisfactorily reproduced by our
calculation. It is suggested that the fundamental nucleon-nucleon interaction
can be probed in a clearer and more direct way in halo nuclei than in ordinary
nuclei.


title:
Violation of the Ikeda sum rule and the self-consistency in the
  renormalized quasiparticle random phase approximation and the nuclear
  double-beta decay

abstract:
  The effect of the inclusion of ground state correlations into the QRPA
equation of motion for the two-neutrino double beta ($\beta\beta_{2\nu}$) decay
is carefully analyzed. The resulting model, called renormalized QRPA (RQRPA),
does not collapse near the physical value of the nuclear force strength in the
particle-particle channel, as happens with the ordinary QRPA. Still, the
$\beta\beta_{2\nu}$ transition amplitude is only slightly less sensitive on
this parameter in the RQRPA than that in the plain QRPA. It is argued that this
fact reveals once more that the characteristic behaviour of the
$\beta\beta_{2\nu}$ transition amplitude within the QRPA is not an artifact of
the model, but a consequence of the partial restoration of the spin-isospin
$SU(4)$ symmetry. It is shown that the price paid for bypassing the collapse in
the RQRPA is the violation of the Ikeda sum rule.


title:
Comment on Final State Interactions beyond the Plane Wave Impulse
  Approximation description of inclusive scattering

abstract:
  It is shown that no set of reasonable assumptions leads to a structure
function as a convolution of the PWIA and a FSI contribution.


title: A Factorization of the S-Matrix into Jost Matrices

abstract:
  An effective algebraic approach to $S$--matrix factorization into Jost
matrices is developed in the case of coupled channels. The Jost matrix is given
as a solution of boundary value Riemann -- Hilbert problem. A rational form is
assumed for tangent of mixing angle, while there is no limitations for
approximation of phase shifts.


title:
Relativistic calculation of the triton binding energy and its
  implications

abstract:
  First results for the triton binding energy obtained from the relativistic
spectator or Gross equation are reported. The Dirac structure of the nucleons
is taken into account. Numerical results are presented for a family of
realistic OBE models with off-shell scalar couplings. It is shown that these
off-shell couplings improve both the fits to the two-body data and the
predictions for the binding energy.


title:
Microscopic Nuclear Equation of State with Three-Body Forces and Neutron
  Star Structure

abstract:
  We calculate static properties of non-rotating neutron stars (NS's) using a
microscopic equation of state (EOS) for asymmetric nuclear matter. The EOS is
computed in the framework of the Brueckner--Bethe--Goldstone many--body theory.
We introduce three-body forces in order to reproduce the correct saturation
point of nuclear matter. A microscopic well behaved EOS is derived. We obtain a
maximum mass configuration with $M_{max} = 1.8 M_\odot$, a radius $R = 9.7$ km
and a central density $n_c = 1.34~fm^{-3}$. We find the proton fraction exceeds
the critical value $x^{Urca}$, for the onset of direct Urca processes, at
densities $n \geq 0.45~fm^{-3}$. Therefore, in our model, NS's with masses
above $M^{Urca} = 0.96 M_\odot$ can undergo very rapid cooling depending on
whether or not nucleon superfluidity in the interior of the NS takes place. A
comparison with other microscopic models for the EOS is done, and neutron star
structure is calculated for these models too.


title: Microscopic calculation of expanding nuclear matter

abstract:
  Quantum Molecular Dynamics (QMD) calculations are used to study the expansion
phase in central collisions between heavy nuclei. The final state of such a
reaction can be understood as the result of a entropy conserving expansion
starting from a compact source. The properties of this hypothetic source,
however, are in conflict with the assumptions used in fireball models.
Moreover, this hypothetical source is not formed in the dynamical evolution of
the system.


title:
Collective flow in heavy ion reactions and the properties of excited
  nuclear matter

abstract:
  Quantum Molecular Dynamics (QMD) calculations of central collisions between
heavy nuclei are used to study fragment production and the creation of
collective flow. It is shown that the final phase space distributions are
compatible with the expectations from a thermally equilibrated source, which in
addition exhibits a collective transverse expansion. However, the microscopic
analyses of the transient states in the intermediate reaction stages show that
the event shapes are more complex and that equilibrium is reached only in very
special cases but not in event samples which cover a wide range of impact
parameters as it is the case in experiments. The basic features of a new
molecular dynamics model (UQMD) for heavy ion collisions from the Fermi energy
regime up to the highest presently available energies are outlined.


title: Threshold meson production in nucleon-nucleon collisions

abstract:
  A brief overview on recent model calculations for near threshold pion
production in nucleon-nucleon collisions is given. Results from our own
investigations of the reactions $pp \rightarrow pp\pi ^0$ and $pn \rightarrow
d\pi^0$ are presented. Direct production, heavy meson exchange and pion
rescattering are taken into account. For the latter a T-matrix obtained from a
microscopic model of the $\pi N$ interaction is employed. We obtain a
significant contribution from rescattering, but not enough to describe the data
for $pp \to pp\pi^0$. The missing production rate can be provided by heavy
meson exchanges. For the first time the effect of off--shell rescattering is
investigated for the reaction $pn \rightarrow d\pi^0$. Isoscalar rescattering
in combination with isovector rescattering is able to describe the s-wave
production data. We confirm that heavy meson exchanges are negligible in this
reaction.


title: Links Between Different Models for Multifragmentation

abstract:
  We establish links between three different models for multifragmentation: the
percolation model, the lattice gas model and the statistical multifragmentation
model. There are remarkable similarities between the lattice gas model and the
statistical multifragmentation model. For completeness, we also compare with a
model based upon classical molecular dynamics which gives rather different
results.


title: General introduction to Compton scattering

abstract:
  Real and virtual Compton scattering has been and will be an important tool to
study the structure of hadronic systems. We summarize the status of real
Compton scattering and give an outlook at the new theoretical and experimental
developments in the field of virtual Compton scattering.


title: Hyperon-rich Matter and Kaons in Matter

abstract:
  We discuss the equation of state of neutron stars in the dense interior
considering hyperons and the possible onset of kaon condensation within the
relativistic mean field model. We find that hyperons are favoured in dense
matter and that their appearance make the existence of a kaon condensed phase
quite unlikely. Implications for the recent measurements of kaons in heavy ion
collisions at subthreshold energy are also given.


title: Dimensional Power Counting in Nuclei

abstract:
  Weinberg's dimensional power counting for nuclei is reprised in this primer.
The role of QCD and chiral symmetry in constructing effective Lagrangians is
discussed. The two-scale hypothesis of Manohar and Georgi is combined with
power counting in amplitudes to shed light on the scales of nuclear kinetic and
potential energies, the size of strong-interaction coupling constants, the size
of meson-exchange currents, and the relative sizes of $N$-nucleon forces.
Numerous examples are worked out and compared to conventional nuclear models.


title: Chiral Symmetry and the Nucleon's Vector Strangeness Form Factors

abstract:
  The nucleon's strange-quark vector current form factors are studied from the
perspective of chiral symmetry. It is argued that chiral perturbation theory
cannot yield a prediction for the strangeness radius and magnetic moment.
Arrival at definite predictions requires the introduction of additional,
model-dependent assumptions which go beyond the framework of chiral
perturbation theory. A variety of such model predictions is surveyed, and the
credibility of each is evaluated. The most plausible prediction appears in a
model where the unknown chiral counterterms are identified with $t$-channel
vector meson exchange amplitudes. The corresponding prediction for the mean
square Dirac strangeness radius is $\langle r_s^2\rangle = 0.24$ fm$^2$, which
would be observable in up-coming semileptonic determinations of the nucleon's
strangeness form factors.


title: Meson-Baryon-Baryon Vertex Function and the Ward-Takahashi Identity

abstract:
  Ohta proposed a solution for the well-known difficulty of satisfying the
Ward-Takahashi identity for a photo-meson-baryon-baryon amplitude ($\gamma$MBB)
when a dressed meson-baryon-baryon (MBB) vertex function is present. He
obtained a form for the $\gamma$MBB amplitude which contained, in addition to
the usual pole terms, longitudinal seagull terms which were determined entirely
by the MBB vertex function. He arrived at his result by using a Lagrangian
which yields the MBB vertex function at tree level. We show that such a
Lagrangian can be neither hermitian nor charge conjugation invariant. We have
been able to reproduce Ohta's result for the $\gamma$MBB amplitude using the
Ward-Takahashi identity and no other assumption, dynamical or otherwise, and
the most general form for the MBB and $\gamma$MBB vertices. However, contrary
to Ohta's finding, we find that the seagull terms are not robust. The seagull
terms extracted from the $\gamma$MBB vertex occur unchanged in tree graphs,
such as in an exchange current amplitude. But the seagull terms which appear in
a loop graph, as in the calculation of an electromagnetic form factor, are, in
general, different. The whole procedure says nothing about the transverse part
of the ($\gamma$MBB) vertex and its contributions to the amplitudes in
question.


title:
Exotic Properties of Light Nuclei and their Neutron Capture Cross
  Sections

abstract:
  We have investigated the implications of the neutron halo configuration,
observed in the ground-state of some neutron-rich light nuclei, on neutron
radiative transition processes. In particular, we have studied the influence of
the neutron halo on the direct radiative capture (DRC) process. The energy
dependence as well as the strength of E1 emission due to incident p-wave
neutrons is strongly influenced by the halo configuration of the residual
nucleus capturing state. We have compared the calculated 10Be(n,gamma)11Be DRC
cross section with that derived from the experiment in the inverse kinematics
(Coulomb dissociation of 11Be). We show from the comparison that some important
information on the structure of the halo nucleus 11Be can be derived.


title:
Translationally invariant treatment of pair correlations in nuclei: I.
  Spin and isospin dependent correlations

abstract:
  We study the extension of our translationally invariant treatment of few-body
nuclear systems to heavier nuclei. At the same time we also introduce
state-dependent correlation operators. Our techniques are tailored to those
nuclei that can be dealt with in $LS$ coupling, which includes all nuclei up to
the shell closure at $A=40$. We study mainly $p$-shell nuclei in this paper. A
detailed comparison with other microscopic many-body approaches is made, using
a variety of schematic nuclear interactions. It is shown that our methodology
produces very good energies, and presumably also wave functions, for medium
mass nuclei.


title: Pion Loop Contribution to Rho-Omega Mixing and Mass Splitting

abstract:
  We study the self-energy amplitudes for the rho-omega meson system produced
by an effective field theory model at the quark level characterized by a finite
range quark-quark interaction and an isospin breaking bare quark mass
difference $m_u - m_d$. Dynamical effects associated with confinement and
dressing of quarks and the finite size of the produced $\bar{q}q$ meson modes
are treated. Parameters of this approach, previously constrained by soft pion
physics, are here supplemented in a minimal way to reproduce $m_\omega$ and
$g_{\rho\pi\pi}$. Calculations are carried out up to the one pion loop level
and the predictions for rho-omega mixing, mass splitting, the rho width and the
symmetry breaking omega-pi-pi coupling constant and form factor are presented.
The contribution of the direct $\omega \rightarrow \pi\pi$ process relative to
the $\omega \rightarrow \rho \rightarrow \pi\pi$ process is discussed within
this model.


title:
Meson Exchange and Pion Rescattering Contributions to the Cross Section
  for $pp\to pp\pi^0$

abstract:
  Short range meson-exchange mechanisms such as $\rho\to\omega\pi^0$ contribute
significantly to the amplitude for $pp\rightarrow pp\pi^0$ near threshold in
addition to pion rescattering. The uncertainty of the latter contribution,
which depends on poorly determined parameters, is estimated. Allowing for this
uncertainty and taking the short range meson-exchange contributions into
account makes it possible to reproduce the measured cross section.


title: Nonradiative proton--deuteron fusion in stellar plasma

abstract:
  The nuclear reaction e+p+d -----> He3 + e is considered at thermonuclear
energies. The motion of the electron is treated within the adiabatic
approximation and the pd scattering state is constructed in the form of an
antisymmetrized product of the bound state wave function of the deuteron and of
the wave function of the pd relative motion. The latter is calculated using an
effective pd potential constructed via the Marchenko inverse scattering method.
The bound state wave function of He3 is obtained using Faddeev--type
integrodifferential equations. The reaction rate thus obtained for the solar
interior conditions is approximately 10^{-4} of the corresponding rate for the
radiative capture pd ----> He3 + gamma .


title: Exact method for locating potential resonances and Regge trajectories

abstract:
  We propose an exact method for locating the zeros of the Jost function for
analytic potentials in the complex momentum--plane. We further extend the
method to the complex angular--momentum plane to provide the Regge
trajectories. It is shown, by using several examples, that highly accurate
results for extremely wide as well as for extremely narrow resonances with or
without the presence of the Coulomb interaction can be obtained.


title:
Hydrodynamical Description of 200 A GeV/c S+Au Collisions: Hadron and
  Electromagnetic Spectra

abstract:
  We study relativistic S+Au collisions at 200 A GeV/c using a hydrodynamical
approach. We test various equations of state (EOSs), which are used to describe
the strongly interacting matter at densities attainable in the CERN-SPS heavy
ion experiments. For each EOS, suitable initial conditions can be determined to
reproduce the experimental hadron spectra; this emphasizes the ambiguity
between the initial conditions and the EOS in such an approach. Simultaneously,
we calculate the resulting thermal photon and dielectron spectra, and compare
with experiments. If one allows the excitation of resonance states with
increasing temperature, the electro-magnetic signals from scenarios with and
without phase transition are very similar and are not resolvable within the
current experimental resolution. With regard to the CERES dilepton data, none
of the EOSs considered, in conjunction with the standard leading order dilepton
rates, succeed in reproducing the observed excess of dileptons below the rho
peak. Our work, however, suggests that an improved measurement of the photon
and dilepton spectra has the potential to strongly constrain the EOS.


title: Analysis of Delta I =2 staggering in nuclear rotational spectra

abstract:
  A method is proposed and tested for the analysis of Delta I=2 staggering
observed in nuclear rotational bands. We examine six super- and hyper-deformed
bands, among which that of 149Gd and possibly of 147Gd seem to exhibit real
staggering. However, we emphasize that the presence of staggering may not
necessarily imply the occurrence of bifurcation. It is also shown that a
similar staggering seen in normally deformed bands is a manifestation of band
crossings. A more extensive analysis is planned.


title: Strangeness in Stellar Matter

abstract:
  A protoneutron star is formed immediately after the gravitational collapse of
the core of a massive star. At birth, the hot and high density matter in such a
star contains a large number of neutrinos trapped during collapse. Trapped
neutrinos generally inhibit the presence of exotic matter -- hyperons, a kaon
condensate, or quarks. However, as the neutrinos diffuse out in about 10-15 s,
the threshold for the appearance of strangeness is reduced; hence, the
composition and the structure of the star can change significantly. The effect
of exotic, negatively-charged, strangeness-bearing components is always to
soften the equation of state, and the possibility exists that the star
collapses to a black hole at this time. This could explain why no neutron star
has yet been seen in the remnant of supernova SN1987A, even though one
certainly existed when neutrinos were detected on Feb. 23, 1987. With new
generation neutrino detectors it is feasible to test different theoretical
scenarios observationally.


title:
Competition Between Particle-Hole and Particle-Particle Correlations in
  Forbidden Electron Capture: the Case of $^{123}$Te

abstract:
  The K-electron capture half-life of $^{123}$Te has been recently measured to
be $t^K_{exp}=2.4\times 10^{19}$ yr, and constitutes the longest half-life ever
measured in a single $\beta$-transition of any nuclear species. We have
calculated this second unique forbidden transition within the framework of the
proton-neutron quasi-particle random phase approximation, making use of
Skyrme-type effective interactions. A strong cancellation effect between
particle-hole and particle-particle correlations is found. The model, without
any renormalization of the force, provides a lower limit for the K-electron
capture half-life of $\sim 10^{17}$ yr, which unambiguously rules out the old
experimental values of $10^{13} - 10^{14}$ yr. A few percent increase of the
particle-particle matrix elements of the Skyrme interaction allows to reproduce
the experimental findings.


title:
Inelastic $J/\Psi$ Photoproduction off Nuclei: Gluon Enhancement or
  Double Color Exchange?

abstract:
  The nuclear enhancement observed in inelastic photoproduction of $J/\Psi$
should not be interpreted as evidence for an increased gluon density in nuclei.
The nuclear suppression of the production rate due to initial and final state
interactions is calculated and a novel two-step color exchange process is
proposed, which is able to explain the data.


title: Towards Study of Color Transparency with Medium Energy Electron Beams

abstract:
  Interference between vector mesons electroproduced at different longitudinal
coordinates leads within Glauber approximation to a $Q^2$-dependence of nuclear
effects similar to what is expected to be an onset of color transparency (CT).
We suggest such a mapping of the photon energies and virtualities, which
eliminates the undesirable $Q^2$-variation and allows to measure a net CT
effect. We develop a multichannel evolution equation, which for the first time
incorporates CT and the effects of the coherence length in the exclusive
electroproduction of vector mesons.


title:
Interplay of Soft and Hard Interactions in Nuclear Shadowing at High
  $Q^2$ and Low x

abstract:
  Nuclear shadowing corrections are dominated by soft interaction and grow as
function of $1/x$ more slowly than the single scattering term, which has an
essential contribution from hard interaction. Therefore, we predict vanishing
nuclear shadowing at very low $x$ provided that $Q^2$ is high and fixed. At the
same time, at medium and low $Q^2$, nuclear shadowing grows with $1/x$ as is
well known for soft hadronic interactions.


title: Hadronization in Nuclear Environment

abstract:
  We present a space-time description of hadronization of highly virtual quarks
originating from a deep-inelastic electron scattering (DIS). Important
ingredients of our approach are the time- and energy--dependence of the density
of energy loss for gluon radiation, the Sudakov's suppression of no radiation,
and the effect of color transparency, which suppresses final state interaction
of the produced colorless wave packet. The model is in a good agreement with
available data on leading hadron production off nucleons and nuclei. The
optimal energy range for study of the hadronization dynamics with nuclear
target is found to be a few tens of GeV, particularly energies available in the
experiment HERMES.


title:
Source Function Determined from HBT Correlations by the Maximum Entropy
  Principle

abstract:
  We study the reconstruction of the source function in space-time directly
from the measured HBT correlation function using the Maximum Entropy Principle.
We find that the problem is ill-defined without at least one additional
theoretical constraint as input. Using the requirement of a finite source
lifetime for the latter we find a new Gaussian parametrization of the source
function directly in terms of the measured HBT radius parameters and its
lifetime, where the latter is a free parameter which is not directly measurable
by HBT. We discuss the implications of our results for the remaining freedom in
building source models consistent with a given set of measured HBT radius
parameters.


title:
Microcanonical Thermodynamics, ``Fragmentation Phase Transition'',and
  the Topology of the N-body Phase Space

abstract:
  Microcanonical thermodynamics (MT) is analysed for phase transitions of first
and second order in finite systems. The transiton temperature, the latent heat
and the surface tension of first order transitions can easily be determined by
MT from the caloric equation of state T(E). The outstandig problem of the
physical meaning of its backbending is clarified for the Potts-model. The
fragmentation phase transition for nuclear multifragmentation is examined in
detail. Further experimental signals of the fragmentation transition in hot
nuclei are discussed.


title:
A New Parameterization for the Lagrangian Density of Relativistic Mean
  Field Theory

abstract:
  A new parameterization for an effective non-linear Lagrangian density of
relativistic mean field (RMF) theory is proposed, which is able to provide an
excellent description not only for the properties of stable nuclei but also for
those far from the valley of beta-stability. In addition recently measured
superdeformed mimima in the Hg-region are reproduced with high accuracy.


title:
A Microscopic Energy- and Density-Dependent Effective Interaction and
  its Test by Nucleus-Nucleus Scattering

abstract:
  An effective nucleon-nucleon interaction calculated in nuclear matter from
the Bonn potential has been parametrized in terms of a local density- and
energy-dependent two-body interaction. This allows to calculate the real part
of the nucleus-nucleus scattering potential and to test this effective
interaction over a wide region of densities ($\rho \leq 3\rho_0$) produced
dynamically in scattering experiments. Comparing our calculations with
empirical potentials extracted from data on light and heavy ion scattering by
model-unrestricted analysis methods, we find quantitative agreement with the
exception of proton scattering. The failure in this case may be traced back to
the properties of the effective interaction at low densities, for which the
nuclear matter results are not reliable. The success of the interaction at high
overlap densities confirms the empirical evidence for a soft equation of state
for cold nuclear matter.


title: O(4) Expansion of the ladder Bethe-Salpeter equation

abstract:
  The Bethe-Salpeter amplitude is expanded on a hyperspherical basis, thereby
reducing the original 4-dimensional integral equation into an infinite set of
coupled 1-dimensional ones. It is shown that this representation offers a
highly accurate method to determine numerically the bound state solutions. For
generic cases only a few hyperspherical waves are needed to achieve
convergence, both for the ground state as well as for radially or orbitally
excited states. The wave function is reconstructed for several cases and in
particular it is shown that it becomes independent of the relative time in the
nonrelativistic regime.


title:
Hadronic Ratios and the Number of Projectile Participants. Thermal
  hadron production in Si-Au collisions

abstract:
  We investigate the dependence of hadronic ratios on the number of projectile
participants using a thermal model incorporating exact baryon number and
strangeness conservation. A comparison is made with results from $Au-Au$
collisions obtained at the BNL-AGS.


title: The $\eta^\prime$ Photoproduction off the Nucleon in the quark model

abstract:
  The reaction $\gamma + p\to \eta^\prime + p$ is investigated in the quark
model approach. The quark model predicts that the off-shell contributions from
the resonance $S_{11}(1535)$ dominate the $\etap$ production in the threshold
region. We find that the coulping constant $\alpha_{\etap NN}$ from the fit to
a few total cross section data is small. The results of the total and
differential cross sections are presented at different energies, which can be
tested in the future experiments. If the future total cross data indeed show a
resonance structure around 2 GeV suggested in a recent study, it would be an
evidence of a non $qqq$ structure in its wavefunction.


title:
Yano-Koonin-Podgoretskii Parametrisation of the Hanbury Brown-Twiss
  Correlator

abstract:
  The Yano-Koonin-Podgoretskii (YKP) parametrisation of Hanbury Brown-Twiss
(HBT) two-particle correlation functions opens new strategies for extracting
the emission duration and testing the longitudinal expansion in heavy-ion
collisions. Based on the recently derived model-independent expressions, we
present a detailed parameter study of the YKP parameters for a finite,
hydrodynamically expanding source model of heavy-ion collisions. For the class
of models studied here, we show that the three YKP radius parameters have an
interpretation as longitudinal extension, transverse extension and emission
duration of the source in the YKP frame. This frame is specified by the fourth
fit parameter, the Yano-Koonin velocity which describes to a good approximation
the velocity of the fluid element with highest emissivity and allows to test
for the longitudinal expansion of the source. Deviations from this
interpretation of the YKP parameters are discussed quantitatively.


title:
Quark condensate in nuclear matter based on Nuclear Schwinger-Dyson
  formalism

abstract:
  The effects of higher order corrections of ring diagrams for the quark
condensate are studied by using the bare vertex Nuclear Schwinger Dyson
formalism based on $\sigma$-$\omega$ model. At the high density the quark
condensate is reduced by the higher order contribution of ring diagrams more
than the mean field theory or the Hartree-Fock .


title: The quark condensate at finite temperature

abstract:
  The temperature evolution of the quark condensate is studied using three
different methods. In the spirit of a many-body approach we make an expansion
in the scalar density up to second order. Our result is consistent chiral
perturbation theory to two-loop order.


title:
Heavy Meson Production in Proton-Nucleus Reactions with Empirical
  Spectral Functions

abstract:
  We study the production of $K^+, \rho, \omega$ and $\phi$ mesons in $p +
^{12}C$ reactions on the basis of empirical spectral functions. The high
momentum, high removal energy part of the spectral function is found to be
negligible in all cases close to the absolute threshold. Furthermore, the
two-step process ($pN \rightarrow \pi N N; \pi N \rightarrow N + K^+, \rho,
\omega, \phi$) dominates the cross section at threshold energies in line with
earlier calculations based on the folding model.


title:
How short is too short? Constraining zero-range interactions in
  nucleon-nucleon scattering

abstract:
  We discuss a number of constraints on the effects of zero-range potentials in
quantum mechanics. We show that for such a potential $p \cot(\delta)$, where
$p$ is the momentum of the nucleon in the center of mass frame and $\delta$ is
the S-wave phase shift, must be a monotonically decreasing function of energy.
This implies that the effective range of the potential is non-positive. We also
examine scattering from the sum of two potentials, one of which is a
short-range interaction. We find that if the short-range interaction is of
zero-range then it must be attractive, and the logarithmic derivative of the
radial wave function at the origin must be a monotonically decreasing function
of energy. If the short-range interaction is not of zero range then a
constraint which gives the minimum possible range for it to fit the phase
shifts exists. The implications of these results for effective field theory
treatments of nucleon-nucleon interactions are discussed.


title: Breakup reactions of the halo nuclei Be11 and B8

abstract:
  We calculate the nuclear induced breakup of Be11 and B8 using a more
realistic treatment of the diffraction and stripping processes than in previous
work. The breakup is treated in the eikonal approximation with a profile
function calculated from a realistic optical potential at low energies and from
free nucleon-nucleon cross sections at high energies. This treatment gives a
good description of measured breakup cross sections, as well as the
longitudinal momentum distribution of the core-like fragments, which is
narrower than predicted in the transparent limit. The real part of the
potential is found to be significant and enhances the diffractive breakup at
low energies.


title: Virtual Compton Scattering off the nucleon in the linear sigma model

abstract:
  Virtual Compton scattering off the nucleon has been studied in the one-loop
approximation of the linear sigma model. The three generalized polarizabilities
of the nucleon have been calculated and compared with the existing theoretical
predictions. In particular, we find that only two of the three scalar
polarizabilities are independent observables.


title: Pions in the nuclear medium

abstract:
  We discuss various aspects of pion physics in the nuclear medium. We first
study s-wave pion-nucleus interaction in connection with chiral symmetry
restoration and quark condensate in the nuclear medium. We then adress the
question of p-wave pion-nucleus interaction and collective pionic modes in
nuclei and draw the consequences for in medium $\pi\pi$ correlations especially
in the scalar-isoscalar channel. We finally discuss the modification of the rho
meson mass spectrum at finite density and/or temperature in connection with
relativistic heavy ion collisions.


title:
Role of anharmonicities and non-linearities in heavy ion collisions. A
  microscopic approach

abstract:
  Using a microscopic approach beyond RPA to treat anharmonicities, we mix
two-phonon states among themselves and with one-phonon states. We also
introduce non-linear terms in the external field. These non-linear terms and
the anharmonicities are not taken into account in the "standard" multiphonon
picture. Within this framework we calculate Coulomb excitation of 208Pb and
40Ca by a 208Pb nucleus at 641 and 1000MeV/A. We show with different examples
the importance of the non-linearities and anharmonicities for the excitation
cross section. We find an increase of 10 % for 208Pb and 20 % for 40Ca of the
excitation cross section corresponding to the energy region of the double giant
dipole resonance with respect to the "standard" calculation. We also find
important effects in the low energy region. The predicted cross section in the
DGDR region is found to be rather close to the experimental observation.


title:
Validity of the linear coupling approximation in heavy-ion fusion
  reactions at sub barrier energies

abstract:
  The role of higher order coupling of surface vibrations to the relative
motion in heavy-ion fusion reactions at near-barrier energies is investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. Taking $^{64}$Ni + $^{92,96}$Zr
reactions as examples, it is shown that all order couplings lead to
considerably improved agreement with the experimentally measured fusion cross
sections and average angular momenta of the compound nucleus for such heavy
nearly symmetric systems. The importance of higher order coupling is also
examined for asymmetric systems like $^{16}$O + $^{112}$Cd, $^{144}$Sm, for
which previous calculations of the fusion cross section seemed to indicate that
the linear coupling approximation was adequate. It is shown that the shape of
the barrier distributions and the energy dependence of the average angular
momentum can change significantly when the higher order couplings are included,
even for systems where measured fusion cross sections may seem to be well
reproduced by the linear coupling approximation.


title: Nuclear Shape Fluctuations in Fermi-Liquid Drop Model

abstract:
  Within the nuclear Fermi-liquid drop model, quantum and thermal fluctuations
are considered by use of the Landau-Vlasov-Langevin equation. The spectral
correlation function of the nuclear surface fluctuations is evaluated in a
simple model of an incompressible and irrotational Fermi liquid. The dependence
of the spectral correlation function on the dynamical Fermi-surface distortion
is established. The temperature at which the eigenvibrations become overdamped
is calculated. It is shown that, for realistic values of the relaxation time
parameter and in the high temperature regime, there is a particular eigenmode
of the Fermi liquid drop where the restoring force is exclusively due to the
dynamical Fermi-surface distortion.


title:
Dilepton Enhancement by Thermal Pion Annihilation in the CERES
  Experiment

abstract:
  We compare the recent CERES data on dielectron production in 200 GeV/u S+Au
collisions with the theoretical predictions due to pion annihilation in a
thermal hadronization and a string fragmentation scenario. Both models yield
similar results for the dilepton mass spectrum. A satisfactory description of
the experimental spectrum requires an in-medium reduction of the rho-mass and a
freeze-out temperature of about 150 MeV in the thermal model. We emphasize and
discuss the influence of experimental acceptance and resolution corrections.


title: Virtual Compton scattering off spin-zero particles at low energies

abstract:
  We discuss the low-energy behavior of the virtual Compton scattering
amplitude off a spin-zero target. We first compare various methods of obtaining
a low-energy expression based either on the soft-photon approximation or the
use of Ward-Takahashi identities. We point out that structure-dependent terms
are defined with respect to a low-energy approximation of the pole terms which
commonly is separated from the full amplitude. We derive a general expression
for the structure-dependent terms in an expansion in terms of the momenta $k_1$
and $k_2$ of the initial and final virtual photon, respectively, up to and
including terms of order ${\cal O}(k^4)$. At order ${\cal O}(k^2)$ two terms
appear which are related to the usual electric and magnetic polarizabilities of
real Compton scattering. At order ${\cal O}(k^4)$ we find nine new structures
of which five can only be determined using virtual photons.


title:
Behavior of the giant-dipole resonance in $^{120}$Sn and $^{208}$Pb at
  high excitation energ

abstract:
  The properties of the giant-dipole resonance (GDR) are calculated as a
function of excitation energy, angular momentum, and the compound nucleus
particle decay width in the nuclei $^{120}$Sn and $^{208}$Pb, and are compared
with recent experimental data. Differences observed in the behavior of the
full-width-at-half-maximum of the GDR for $^{120}$Sn and $^{208}$Pb are
attributed to the fact that shell corrections in $^{208}$Pb are stronger than
in $^{120}$Sn, and favor the spherical shape at low temperatures. The effects
shell corrections have on both the free energy and the moments of inertia are
discussed in detail. At high temperature, the FWHM in $^{120}$Sn exhibits
effects due to the evaporation width of the compound nucleus, while these
effects are predicted for $^{208}$Pb.


title: In-medium Production of Kaons at the Mean-Field Level

abstract:
  The in-medium mass and energy of kaons and antikaons are studied within the
Relativistic Mean Field approach and compared with predictions from chiral
models by taking care of kaon-nucleon scattering data. Implications for the
subthreshold production of kaons and antikaons in heavy-ion collisions are
discussed. We find only small corrections due to in-medium effects on the
mean-field level for the relevant production processes for kaons. The
production of kaons is even less favourable at high density due to repulsive
vector interactions. We conclude that one has to go beyond mean-field
approaches and take fluctuations and secondary production processes into
account to explain the recently measured enhancement of kaon production at
subthreshold energies. The situation is different for antikaons where in-medium
effects strongly enhances their production rates. We also see strong in-medium
modifications of the annihilation processes of antikaons and Lambda's which
might be visible in flow measurements. At high density, we predict that the
threshold energy for antikaon and Lambda production and annihilation become
equal leading to similar numbers of antikaons and Lambda's in the dense zone of
a relativistic heavy ion collision.


title: Pionic Decay of a Possible d'-Dibaryon

abstract:
  The pionic decay of a possible d'-dibaryon in the process d' --> pi + N + N
is studied in the microscopic quark shell model and with a single-quark
transition operator describing the transition q --> pi + q'. For the d' with
quantum numbers J^P=0^-, T=0, we employ a six-quark shell-model wave function
with a spatial s^5p [51]_X-configuration with N=1 harmonic oscillator quanta.
It is shown that the pionic decay width depends strongly on the mass and size
of the d'. In the case that the calculated d' mass is close to the experimental
one a small pionic decay width of 0.04 MeV is obtained. This is an order of
magnitude smaller than the experimentally suggested value of 0.5 MeV. Two
possibilities to improve the calculated width are suggested. The effect of the
nonstatic correction term in the transition operator and the influence of the
form factor at the decay vertex on the decay width are also discussed.


title: How to extract physics from HBT radius parameters

abstract:
  I review recent progress in the understanding of the connection between the
space-time structure of the particle emitting source and the form of the
two-particle correlation function in momentum space. Based on a new scheme for
calculating the HBT radius parameters from the emission function, strategies
are suggested to separate for rapidly expanding sources the information on the
spatial and temporal structure of the source. To this end a new fitting
function for the two-particle correlation function is proposed. Its usefulness
is demonstrated for a typical expanding model source, and it is shown how the
dependence of the resulting fit parameters on the momentum of the particle pair
can be used to measure the longitudinal and transverse expansion of the source.


title: Shell Model Study of the Neutron-Rich Nuclei around N=28

abstract:
  We describe the properties of the neutron rich nuclei around N=28 in the
shell mode framework. The valence space comprises the $sd$ shell for protons an
the $pf$ shell for neutrons without any restriction. Good agreement is found
with the available experimental data. The N=28 shell closure, even if eroded
due to the large neutron excess, persists. The calculations predict that
$^{40}$S and $^{42}$S are deformed with $\beta=0.29 $ and $\beta=0.32$
respectively.


title: Virtual versus Real Nuclear Compton Scattering in the Delta(1232) Region

abstract:
  In this paper we calculate the cross section for Virtual Compton Scattering
off nuclei in the delta resonance region. We also calculate the background for
the process from Coherent Bremsstrahlung in nuclei and explore the regions
where the Virtual Compton Scattering cross section dominates. The study also
shows that it is possible to extract the cross section for Real Compton
Scattering from the Virtual Compton one in a wide range of scattering angles.


title: Superheavy Nuclei in the Relativistic Mean Field Theory

abstract:
  We have carried out a study of superheavy nuclei in the framework of the
Relativistic Mean-Field theory. Relativistic Hartree-Bogoliubov (RHB)
calculations have been performed for nuclei with large proton and neutron
numbers. A finite-range pairing force of Gogny type has been used in the RHB
calculations. The ground-state properties of very heavy nuclei with atomic
numbers Z=100-114 and neutron numbers N=154-190 have been obtained. The results
show that in addition to N=184 the neutron numbers N=160 and N=166 exhibit an
extra stability as compared to their neighbors. For the case of protons the
atomic number Z=106 is shown to demonstrate a closed-shell behavior in the
region of well deformed nuclei about N=160. The proton number Z=114 also
indicates a shell closure. Indications for a doubly magic character at Z=106
and N=160 are observed. Implications of shell closures on a possible synthesis
of superheavy nuclei are discussed.


title:
Implications of Recent Data on Non-mesonic Decay of Light
  Lambda-hypernuclei

abstract:
  We analyze the recent data on the non-mesonic decays of light
Lambda-hypernuclei up to ^12_Lambda C using the phenomenological model of Block
and Dalitz. Fitting the spin-isospin dependent Lambda N -> NN reaction rates to
six data points, we predict the remaining data in reasonable consistency. We
find that despite the short-range nature of the Lambda N -> NN interaction, the
non-mesonic decay of p-shell hypernuclei seems to be strongly induced by the
p-shell neutrons. Also, the recent data indicate that the Delta I = 1/2 rule,
well proved at the hadronic level, may not be sacred in the nuclear medium and
the Delta I = 3/2 interactions seem to be needed to describe the non-mesonic
decays of Lambda-hypernuclei.


title:
S-matrix and R-matrix determination of the low-energy He-5 and Li-5
  resonance parameters

abstract:
  We study the low-energy 3/2- and 1/2- states of He-5 and Li-5 in a
microscopic cluster model. The scattering phase shifts of Bond (alpha+n) and of
Schwandt (alpha+p), respectively, are reproduced well. We determine the
resonance parameters by localizing the poles of the analytically continued
S-matrix at complex energies. Our results differ from conventional R-matrix
resonance parameters, which were extracted from experimental data using the
definition of a resonance based on the positions and widths of reaction cross
section peaks. However, they nicely agree with the results of an extended
R-matrix method which works at complex energies.


title:
Constituent quark model for nuclear stopping in high energy nuclear
  collisions

abstract:
  We study the nuclear stopping in high energy nuclear collisions using the
constituent quark model. It is assumed that wounded nucleons with different
number of interacted quarks hadronize in different ways. The probabilities of
having such wounded nucleons are evaluated for proton-proton, proton-nucleus
and nucleus-nucleus collisions. After examining our model in proton-proton and
proton-nucleus collisions and fixing the hadronization functions, it is
extended to nucleus-nucleus collisions. It is used to calculate the rapidity
distribution and the rapidity shift of final state protons in nucleus-nucleus
collisions. The computed results are in good agreement with the experimental
data on $^{32}\mbox{S} +\ ^{32}\mbox{S}$ at $E_{lab} = 200$ AGeV and
$^{208}\mbox{Pb} +\ ^{208}\mbox{Pb}$ at $E_{lab} = 160$ AGeV. Theoretical
predictions are also given for proton rapidity distribution in $^{197}\mbox{Au}
+\ ^{197}\mbox{Au}$ at $\sqrt{s} = 200$ AGeV (BNL-RHIC). We predict that the
nearly baryon free region will appear in the midrapidity region and the
rapidity shift is $\langle \Delta y \rangle = 2.22$.


title:
Glauber theory of initial- and final-state interactions in (p,2p)
  scattering

abstract:
  We develop the Glauber theory description of initial- and final-state
interactions (IFSI) in quasielastic A(p,2p) scattering. We study the
IFSI-distortion effects both for the inclusive and exclusive conditions. In
inclusive reaction the important new effect is an interaction between the two
sets of the trajectories which enter the calculation of IFSI-distorted one-body
density matrix for inclusive (p,2p) scattering and are connected with
incoherent elastic rescatterings of the initial and final protons on spectator
nucleons. We demonstrate that IFSI-distortions of the missing momentum
distribution are large over the whole range of missing momentum both for
inclusive and exclusive reactions and affect in a crucial way the
interpretation of the BNL data on (p,2p) scattering. Our numerical results show
that in the region of missing momentum $p_{m}\lsim 100-150$ MeV/c the
incoherent IFSI increase nuclear transparency by 5-10\%. The incoherent IFSI
become dominant at $p_{m}\gsim 200$ MeV/c.


title: Pion electromagnetic form factor at finite temperature

abstract:
  Temperature effects on the electromagnetic couplings of pions in hot hadronic
matter are studied with an effective chiral Lagrangian. We show that the
Ward-Takahashi identity is satisfied at non-zero temperature in the soft pion
limit. The in-medium electromagnetic form factor of the pion is obtained in the
time-like region and shown to be reduced in magnitude, especially near the
vector-meson resonance region. Finally, we discuss the consequences of this
medium effect on dilepton production from hot hadronic matter.


title:
Derivation and assessment of strong coupling core-particle model from
  the Kerman-Klein-D\"onau-Frauendorf theory

abstract:
  We review briefly the fundamental equations of a semi-microscopic
core-particle coupling method that makes no reference to an intrinsic system of
coordinates. We then demonstrate how an intrinsic system can be introduced in
the strong coupling limit so as to yield a completely equivalent formulation.
It is emphasized that the conventional core-particle coupling calculation
introduces a further approximation that avoids what has hitherto been the most
time-consuming feature of the full theory, and that this approximation can be
introduced either in the intrinsic system, the usual case, or in the laboratory
system, our preference. A new algorithm is described for the full theory that
largely removes the difference in complexity between the two types of
calculation. Comparison of the full and approximate theories for some
representative cases provides a basis for the assessment of the accuracy of the
traditional approach. We find that for well-deformed nuclei, e.g. 157Gd and
157Tb, the core-coupling method and the full theory give similar results.


title: Quasielastic K-nucleus scattering

abstract:
  Quasielastic K^+ - nucleus scattering data at q=290, 390 and 480 MeV/c are
analyzed in a finite nucleus continuum random phase approximation framework,
using a density-dependent particle-hole interaction. The reaction mechanism is
consistently treated according to Glauber theory, keeping up to two-step
inelastic processes. A good description of the data is achieved, also providing
a useful constraint on the strength of the effective particle-hole interaction
in the scalar-isoscalar channel at intermediate momentum transfers. We find no
evidence for the increase in the effective number of nucleons participating in
the reaction which has been reported in the literature.


title: Self-Screened Parton Cascades

abstract:
  The high density of scattered partons predicted in nuclear collisions at very
high energy makes color screening effects significant. We explain how these
screening mechanisms may suppress nonperturbative, soft QCD processes,
permitting a consistent calculation of quark-gluon plasma formation within the
framework of perturbative QCD. We present results of a model calculation of
these effects including predictions for the initial thermalized state for heavy
nuclei colliding at RHIC and LHC.


title: Pbar Annihilation in Au+Au at AGS Energies

abstract:
  Antinucleon production in heavy ion collisions is potentially an excellent
signal for unusual phenomena in hot and dense matter. However, at the low
energies available at the AGS the annihilation process must be handled with
care. In this Comment, we consider the case of Au + Au collisions at
approximately 11 GeV/c, applying the ARC treatment of pbar production and
annihilation to the analysis of experiment E878. It is apparent that classical
screening introduced for Si + Au is crucial in the understanding of data
obtained with the more massive projectile. Unfortunately, there seems no
necessity for invoking unusual behaviour in the Au + Au system.


title: The Chiral Phase Transition

abstract:
  I review the current understanding of the chiral phase transition in QCD,
with particular emphasis on recent results obtained in the instanton liquid
model.


title:
On the missing momentum dependence of the color transparency effects in
  (e,e'p) scattering

abstract:
  We explore the missing momentum dependence of the CT effects in quasielastic
(e,e'p) scattering. We develop the coupled-channel multiple-scattering theory
(CCMST) description of final-state interaction including both the coherent and
incoherent rescatterings of the ejectile state. We demonstrate that the
contribution of the off-diagonal incoherent rescattering does not vanish at low
Q^{2} which is a novel correction to the conventional Glauber theory evaluation
of nuclear transparency. We comment on the nontrivial impact of this correction
on the onset of CT. The sensitivity of the onset of CT to the 3q-nucleon
reggeon amplitudes is discussed for the first time. We present numerical
results for nuclear transparency as a function of the missing momentum for
exclusive (e,e'p) reaction in the kinematical region of Q^{2} \le 40 GeV^{2}
and p_{m} \le 250$ MeV/c. Our evaluations show that at Q^{2}\sim 10 CT effects
are substantial only in antiparallel kinematics at p_{m,z}\sim -250 MeV/c. The
effect is enhanced on light nuclei and could be observed in a high precision
experiment.


title:
K^+ momentum spectrum from (K^-,K^+) reactions in intranuclear cascade
  model

abstract:
  In a framework of intranuclear cascade (INC) type calculation, we study a
momentum spectrum in reactions \KK at a beam momentum of 1.65 GeV/c. INC model
calculations are compared with the relativistic impulse approximation (RIA)
calculations to perform the detailed study of the reaction mechanism. We find
that the INC model can reproduce the experimental data on various targets.
Especially, in the low-momentum region, the forward-angle cross sections of the
$(K^-,K^+)$ reaction on from light to heavy targets are consistently explained
with the two-step strangeness exchange and production processes with various
intermediate mesons, and $\phi$, $a_0$ and $f_0$ productions and their decay
into $K^+K^-$. In the two-step processes, inclusion of meson and hyperon
resonances is found to be essential.


title: The Chromo-Dielectric Soliton Model: Quark Self Energy and Hadron Bags

abstract:
  The chromo-dielectric soliton model (CDM) is Lorentz- and chirally-invariant.
It has been demonstrated to exhibit dynamical chiral symmetry breaking and
spatial confinement in the locally uniform approximation. We here study the
full nonlocal quark self energy in a color-dielectric medium modeled by a two
parameter Fermi function. Here color confinement is manifest. The self energy
thus obtained is used to calculate quark wave functions in the medium which, in
turn, are used to calculate the nucleon and pion masses in the one gluon
exchange approximation. The nucleon mass is fixed to its empirical value using
scaling arguments; the pion mass (for massless current quarks) turns out to be
small but non-zero, depending on the model parameters.


title:
Additivity of Quadrupole Moments in Superdeformed Bands: Single-Particle
  Motion at Extreme Conditions

abstract:
  Quadrupole and hexadecapole moments of superdeformed bands in the
$A$$\sim$150 mass region have been analyzed in the cranking Skyrme-Hartree-Fock
model. It is demonstrated that, independently of the intrinsic configuration
and of the proton and neutron numbers, the charge moments calculated with
respect to the doubly-magic superdeformed core of $^{152}$Dy can be expressed
very precisely in terms of independent contributions from the individual hole
and particle orbitals. This result, together with earlier studies of the
moments of inertia distributions, suggests that many features of the
superdeformed bands in the $A$$\sim$150 mass region can be very well understood
in terms of an almost undisturbed single-particle motion.


title: Shell Structure of the Superheavy Elements

abstract:
  Ground state properties of the superheavy elements (SHE) with Z from 108 to
128 and N from 150 to 192 are investigated using both the Skyrme-Hartree-Fock
method with a density-independent contact pairing interaction and the
macroscopic-microscopic approach with an average Woods-Saxon potential and a
monopole pairing interaction. Detailed analysis of binding energies, separation
energies, shell effects, single proton and neutron states, equilibrium
deformations, alpha-decay energies, and other observables is given.


title: A new effective Lagrangian for nuclear matter

abstract:
  The relativistic mean field model, the Zim\'anyi - Moszkowski (ZM) Lagrangian
describes nuclear matter and stable finite nuclei even in the non-relativistic
limit. It fails, however, to predict the correct non-relativistic spin-orbit
(SO) coupling. In this paper we improve on this matter by an additional tensor
coupling analogous to the anomalous gyromagnetic ratio. It can be adjusted to
describe the SO-term without changing the mean field solution of the
ZM-Lagrangian for nuclear matter.


title: Vlasov dynamics for fermions on phase space lattice

abstract:
  Within the framework of stochastic one-body approach a simulation procedure
to study the Vlasov dynamics for fermi system on phase space lattice is
presented. To deal with fermions on lattice, the phase cell occupancy factors
are taken to be either 1 or 0 in accordance with the Pauli exclusion principle.
This has significant implications. First, the dynamical evolution does not
alter initial temperature of the system and secondly, at finite temperature,
the proper statistical behaviour related to the fluctuations over the samples
is ensured. This method is applied for two distinct cases viz. the monopole
vibration of cold dilute nucleus and the evolution of ring shaped matter
distribution at finite temperature in the presence of radial flow. In the
latter case, fragment multiplicities are found to be depend on the flow
velocity. To check the reliability of the present calculations simulations have
been performed with different choices of the grid size.


title:
Change of MIT Bag Constant in Nuclear Medium and Implication for the EMC
  Effect

abstract:
  The modified quark-meson coupling model, which features a density dependent
bag constant and bag radius in nuclear matter, is checked against the EMC
effect within the framework of dynamical rescaling. Our emphasis is on the
change in the average bag radius in nuclei, as evaluated in a local density
approximation, and its implication for the rescaling parameter. We find that
when the bag constant in nuclear matter is significantly reduced from its
free-space value, the resulting rescaling parameter is in good agreement with
that required to explain the observed depletion of the structure functions in
the medium Bjorken $x$ region. Such a large reduction of the bag constant also
implies large and canceling Lorentz scalar and vector potentials for the
nucleon in nuclear matter which are comparable to those suggested by the
relativistic nuclear phenomenology and finite-density QCD sum rules.


title:
Hydrodynamics and collective behaviour in relativistic nuclear
  collisions

abstract:
  Hydrodynamics is applied to describe the dynamics of relativistic heavy-ion
collisions. The focus of the present study is the influence of a possible
(phase) transition to the quark-gluon plasma in the nuclear matter equation of
state on collective observables, such as the lifetime of the system and the
transverse directed flow of matter. It is shown that such a transition leads to
a softening of the equation of state, and consequently to a time-delayed
expansion which is in principle observable via two-particle correlation
functions. Moreover, the delayed expansion leads to a local minimum in the
excitation function of transverse directed flow around AGS energies.


title:
Isospin Lattice-Gas Model and Liquid-Gas Phase Transition in Asymmetric
  Nuclear Matter

abstract:
  An isospin lattice-gas model, which is a spin-1 Ising model, is employed to
investigate the liquid-gas phase transition in asymmetric nuclear matter. We
consider nuclear matter as a lattice where each lattice site can be either
empty or occupied by a proton or a neutron, with a nearest-neighbor interaction
among the nucleons. With the Bragg-Williams mean field approximation, we
calculate various thermodynamic properties of nuclear matter for different
densities and different proton-neutron asymmetry parameter $s$. Our model
exhibits liquid-gas phase transition below a critical temperature $T_c$, and
predicts a monotonic decreasing of $T_c$ as the magnitude of $s$ is increased.
The dependence of the nuclear matter isotherms on the asymmetry parameter $s$
is discussed.


title: The simplest ``strange'' three-body halo

abstract:
  The recently developed method to solve the Faddeev equations in coordinate
space is used to study the weakly bound halo nucleus, the hypertriton (Lambda +
n + p). The long distances are treated carefully to achieve convergence and
high accuracy. We use several sets of two-body interactions which reproduce the
deuteron properties and provide the low-energy Lambda-nucleon scattering data
close to that of two of Nijmegen potentials. We show that the details of the
potentials are unimportant unless the accuracy of the hypertriton binding
energy is required to be better than 50 keV. We find that the most significant
parameter of the Lambda-nucleon interaction, the singlet s-wave scattering
length, must be within 10% of 1.85 fm, when the Lambda-separation energy from
the deuteron is about 130 keV. Other details of the Lambda-nucleon interaction
are less important for the hypertriton structure. The scattering length and
effective range are computed for scattering of a Lambda-particle on a deuteron.
The folding model reducing the three-body problem to a two-body problem is
investigated in this context and found to be inadequate.


title:
The Effects of Bose-Condensates on Single Inclusive Spectra and
  Bose-Einstein Correlations

abstract:
  The implications of the formation of a Bose condensate on one- and
two-particle spectra are studied for ultrarelativistic nucleus-nucleus
collisions in the framework of a hydrodynamic description. It is found that
single particle spectra are considerably enhanced at low momenta. The
Bose-Einstein correlation function has an intercept below two. For pion pairs
in the central region a two-component structure may appear in the correlation
function, which is different from that found in quantum optics. The chaoticity
parameter is strongly momentum dependent.


title:
The Three-Body Continuum Coulomb Problem and the 3$\alpha$ Structure of
  $^{12}$C

abstract:
  We introduce an approach, based on the coordinate space Faddeev equations, to
solve the quantum mechanical three-body Coulomb problem in the continuum. We
apply the approach to compute measured properties of the first two $0^+$ levels
in $^{12}$C, including the width of the excited level, in a 3$\alpha$-particle
model. We use the two-body interaction which reproduces the low energy
$\alpha$-$\alpha$ scattering data and add a three-body force to account for the
compound state admixture.


title: Resonance model study of strangeness production in pp collisions

abstract:
  Results for the energy dependence of the elementary kaon production cross
sections in proton-proton collisions are reported. Calculations are performed
within an extended version of the resonance model which was used for the
previous studies of elementary kaon production in pion-nucleon and
pion-$\Delta$ collisions. Although the model treatment is within the {\it
empirical} tree level (observed widths for the resonances are used), it is
fully relativistic, and includes all relevant baryon resonances up to 2 GeV.
One of the purposes of this study is to provide the results for the simulation
codes of subthreshold kaon production in heavy ion collisions. This is the
first, consistent study of the elementary kaon production reactions including
both $\pi B$ and $B B$ ($B=N, \Delta$) collisions on the same footing.
Comparisons are made between the calculated results and the existing
semi-empirical parametrizations which are widely used for the simulation codes,
as well as the experimental data.


title: New Observables in Break-up Reactions of Three-body Halos

abstract:
  Momentum distributions of particles from fast three-body halo fragmentation
reactions with polarized beams and outgoing fragments are analyzed by use of
the sudden approximation. The final state interaction between the two
non-disturbed particles is considered. We first give a general and detailed
description of the method. We introduce observable quantities that emphasize
the two-body correlations in the initial three-body structure as well as in the
final two-body system. Using neutron removal from 11Li as an example we
investigate the dependence of the polarization observables on the properties of
the low-lying resonances and virtual states of the 10Li subsystem. These
observables are very sensitive to the l > 0-waves in the wave functions, and
they provide detailed information on the resonance structure of the
neutron-core subsystem.


title:
The Pauli principle in a three-body cluster model and the momentum
  distributions after fragmentation of 6He and 11Li

abstract:
  We investigate two simple prescriptions to account for the Pauli principle in
a three-body cluster model employing a new method based on an adiabatic
hyperspherical expansion to solve the Faddeev equations in coordinate space.
The resulting wave functions are computed and compared. They are furthermore
tested on halo nuclei by calculations of momentum distributions and invariant
mass spectra arising after fragmentation of fast $^6$He and $^{11}$Li in
collisions with light targets. The prescriptions are very accurate and the
available measured quantities are remarkably well reproduced when final state
interactions are included.


title: Three-body Halos. IV. Momentum Distributions after Fragmentation

abstract:
  Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated incorporating effects of final state interactions. The
same two-body interactions between the particles are used to calculate both the
ground state structure and the final state of the reaction processes. The
ground state wave function reproduces size and energy of the halo nucleus.
First we give a general and detailed description of the method. Then we
investigate the effect of final state interactions in neutron removal and core
break-up reactions for one- and two-dimensional momentum distributions. We
compute specifically core and neutron momentum distributions from 11Li
fragmentation and compare those with available experimental data. We conclude
that 11Li must have a neutron-core relative state containing a p-state
admixture of 20\%-30\%. The fragmentation data also strongly suggest that 10Li
has an s-state at about 50 keV and a p-state around 500 keV.


title: Three-Body Halo Fragmentation: Polarization effects

abstract:
  Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated for polarized beam and outgoing fragments. These momentum
distributions are combined in observable quantities which emphasize the
two-body correlations in the initial three-body structure as well as in the
final two-body system. Applying the formalism to 11Li we find a sensitive
dependence on the p-wave content and on the position of the p-resonances in
10Li. Polarization experiments are then a new tool to study correlations in
nuclear halos.


title: Square-well solution to the three-body problem

abstract:
  The angular part of the Faddeev equations is solved analytically for s-states
for two-body square-well potentials. The results are, still analytically,
generalized to arbitrary short-range potentials for both small and large
distances. We consider systems with three identical bosons, three non-identical
particles and two identical spin-1/2 fermions plus a third particle with
arbitrary spin. The angular wave functions are in general linear combinations
of trigonometric and exponential functions. The Efimov conditions are obtained
at large distances. General properties and applications to arbitrary potentials
are discussed. Gaussian potentials are used for illustrations. The results are
useful for numerical calculations, where for example large distances can be
treated analytically and matched to the numerical solutions at smaller
distances. The saving is substantial.


title: A Chiral Effective Lagrangian for Nuclei

abstract:
  An effective hadronic lagrangian consistent with the symmetries of quantum
chromodynamics and intended for applications to finite-density systems is
constructed. The degrees of freedom are (valence) nucleons, pions, and the
low-lying non-Goldstone bosons, which account for the intermediate-range
nucleon-nucleon interactions and conveniently describe the nonvanishing
expectation values of nucleon bilinears. Chiral symmetry is realized
nonlinearly, with a light scalar meson included as a chiral singlet to describe
the mid-range nucleon-nucleon attraction. The low-energy electromagnetic
structure of the nucleon is described within the theory using vector-meson
dominance, so that external form factors are not needed. The effective
lagrangian is expanded in powers of the fields and their derivatives, with the
terms organized using Georgi's ``naive dimensional analysis''. Results are
presented for finite nuclei and nuclear matter at one-baryon-loop order, using
the single-nucleon structure determined within the model. Parameters obtained
from fits to nuclear properties show that naive dimensional analysis is a
useful principle and that a truncation of the effective lagrangian at the first
few powers of the fields and their derivatives is justified.


title: The role of chiral symmetry in two-pion exchange nuclear potential

abstract:
  We evaluate the two pion exchange contribution to the nucleon-nucleon
potential in configuration space using a "minimal chiral model" containing only
pions and nucleons. We argue that this model has nowadays a rather firm
conceptual basis, which entitles it to become a standard ingredient of any
modern potential. The main features of this model is that the scalar-isoscalar
component of the interaction is relatively small, due to cancellations between
large terms, and fails to reproduce the intermediate range attraction in the
central channel. We show that chiral symmetry is the responsible for these
large cancellations in the two-pion exchange nucleon-nucleon interaction, which
are similar to those occuring in free pion-nucleon scattering. Another feature
of the model is that these results do not depend on how chiral symmetry is
implemented.


title: Light Vector Mesons at Finite Baryon Density

abstract:
  We summarize the current theoretical and experimental status of the spectral
changes of vector mesons ($\rho$, $\omega$, $\phi$) at finite baryon density.
Various approaches including QCD sum rules, effective theory of hadrons and bag
models show decreasing of the vector meson masses in nuclear matter.
Possibility to detect the mass shift through lepton pairs in $\gamma-A$, $p-A$
and $A-A$ reactions are also discussed.


title: QCD Sum Rule for S_{11}(1535)

abstract:
  We propose a new interpolating field for S$_{11}$(1535) to determine its mass
from QCD sum rules. In the nonrelativistic limit, this interpolating field
dominantly reduces to two quarks in the s-wave state and one quark in the
p-wave state. An optimization procedure, which makes use of a duality relation,
yields the interpolating field which overlaps strongly with the negative-parity
baryon and at the same time does not couple at all to the low lying
positive-parity baryon. Using this interpolating field and applying the
conventional QCD sum rule analysis, we find that the mass of S$_{11}$ is
reasonably close to the experimentally known value, even though the precise
determination depends on the poorly known quark-gluon condensate. Hence our
interpolating field can be used to investigate the spectral properties of
S$_{11}$(1535).


title: From $K^+$ in heavy-ion collisions to $K^-$ in kaonic atoms

abstract:
  Kaon production and kaon flow in heavy-ion collisions at SIS energies are
analyzed using the relativistic transport model. The experimental data are
found to be consistent with the scenario that kaon scalar (before being cut
down by the range term) and vector mean field potentials are about 1/3 of that
of nucleons in the Walecka model. This also explains the strong attraction
found for $K^-$ in kaonic atoms, and gives information on the possibility of
$K^-$ condensation in dense matter.


title:
Effects of in-medium vector meson masses on low-mass dileptons from SPS
  heavy-ion collisions

abstract:
  Using a relativistic transport model to describe the expansion of the
fire-cylinder formed in the initial stage of heavy-ion collisions at SPS/CERN
energies, we study the production of dileptons with mass below about 1 GeV from
these collisions. The initial hadron abundance and their momentum distributions
in the fire-cylinder are determined by following the general features of the
results from microscopic models based on the string dynamics and further
requiring that the final proton and pion spectra and rapidity distributions are
in agreement with available experimental data. For dilepton production, we
include the Dalitz decay of $\pi ^0$, $\eta$, $\eta^\prime$, $\omega$ and $a_1$
mesons, the direct decay of primary $\rho ^0$, $\omega$ and $\phi$ mesons, and
the pion-pion annihilation that proceeds through the $\rho^0$ meson, the
pion-rho annihilation that proceeds through the $a_1$ meson, and the
kaon-antikaon annihilation that proceeds through the $\phi$ meson. We find that
the modification of vector meson properties, especially the decrease of their
mass due to the partial restoration of chiral symmetry, in hot and dense
hadronic matter, provides a quantitative explanation of the recently observed
enhancement of low-mass dileptons by the CERES collaboration in central S+Au
collisions and by the HELIOS-3 collaboration in central S+W collisions.


title: Competition Between T=0 and T=1 Pairing in Proton-Rich Nuclei

abstract:
  A cranked mean-field model with two-body T=1 and T=0 pairing interactions is
presented. Approximate projection onto good particle-number is enforced via an
extended Lipkin-Nogami scheme. Our calculations suggest the simultaneous
presence of both T=0 and T=1 pairing modes in N=Z nuclei. The transitions
between different pairing phases are discussed as a function of neutron/proton
excess, T$_z$, and rotational frequency, $\hbar\omega$. The additional binding
energy due to the T=0 $np$-pairing correlations, is suggested as a possible
microscopic explanation of the Wigner energy term in even-even nuclei.


title: Virtual Compton Scattering off the Nucleon in Chiral Perturbation Theory

abstract:
  We investigate the spin-independent part of the virtual Compton scattering
(VCS) amplitude off the nucleon within the framework of chiral perturbation
theory. We perform a consistent calculation to third order in external momenta
according to Weinberg's power counting. With this calculation we can determine
the second- and fourth-order structure-dependent coefficients of the general
low-energy expansion of the spin-averaged VCS amplitude based on gauge
invariance, crossing symmetry and the discrete symmetries. We discuss the
kinematical regime to which our calculation can be applied and compare our
expansion with the multipole expansion by Guichon, Liu and Thomas. We establish
the connection of our calculation with the generalized polarizabilities of the
nucleon where it is possible.


title:
Influence of spin-rotation measurements on partial-wave analyses of
  elastic pion-nucleon scattering

abstract:
  Recent measurements of spin-rotation parameters in elastic $\pi^+ p$
scattering are in marked disagreement with predictions of the
Carnegie-Mellon$-$Berkeley and Karlsruhe-Helsinki analyses. Using the method of
Barrelet, we show how this discrepancy can be removed. We then show how this
Barrelet transformation alters the partial-wave amplitudes. The effect of
unitarity and analyticity constraints is also considered.


title: Full pf shell study of A = 47 and A = 49 nuclei

abstract:
  Complete diagonalizations in the pf major shell, lead to very good agreement
with the experimental data (level schemes, transitions rates, and static
moments) for the A=47 and A=49 isotopes of Ca, Sc, Ti, V, Cr, and Mn.
Gamow-Teller and M1 strength functions are calculated. The necessary monopole
modifications to the realistic interactions are shown to be critically tested
by the spectroscopic factors for one particle transfer from 48Ca, reproduced in
detail by the calculations. The collective behaviour of 47Ti, and of the mirror
pairs 47V-47Cr and 49Cr-49Mn is found to follow at low spins the particle plus
rotor model. It is then analysed in terms of the approximate quasi-SU(3)
symmetry, for which some new results are given.


title: $^3$He Transport in the Sun and the Solar Neutrino Problem

abstract:
  Recent solar neutrino experiments have shown that both $\phi(^8$B) and the
neutrino flux ratio $\phi(^7$Be)/$\phi(^8$B) are substantially below their
standard solar model values, leading some to discount the possibility of an
astrophysical solution to the solar neutrino puzzle. We test this conclusion
phenomenologically and find that the discrepancies can be significantly reduced
by a distinctive pattern of core mixing on timescales characteristic of $^3$He
equilibration.


title: Microscopic Calculation of the $^4{\rm He}$ System

abstract:
  We report on a consistent, microscopic calculation of the bound and
scattering states in the 4He system employing a realistic nucleon-nucleon
potential in the framework of the resonating group model (RGM). We present for
comparison with these microscopic RGM calculations the results from a
charge-independent, Coulomb-corrected R-matrix analysis of all types of data
for reactions in the A=4 system. Comparisons are made between the phase shifts,
and with a selection of measurements from each reaction, as well as between the
resonance spectra obtained from both calculations. In general, the comparisons
are favorable, but distinct differences are observed between the RGM
calculations and some of the polarisation data. The partial-wave decomposition
of the experimental data produced by the R-matrix analysis shows that these
differences can be attributed to just a few S-matrix elements, for which
inadequate tensor-force strength in the N-N interaction used appears to be
responsible.


title:
On the direct nucleon decay of high-spin subbarrier single-particle
  states in near-magic nuclei

abstract:
  The description of the direct nucleon decay of high-spin subbarrier
one-particle states in near-magic nuclei is attempted using a simple optical
model and the simplest version of the coupled-channel approach. The branching
ratios for the direct decay of the several single-neutron states in $^{209}Pb$
and $^{91}Zr$ to the ground state and to the low-lying collective states of
$^{208}Pb$ and $^{90}Zr$, respectively, are evaluated. Results are compared
with recent experimental data.


title: On the $m_\perp$-dependence of Bose-Einstein correlation radii

abstract:
  Within a theoretical study using both HYLANDER and RQMD, we revisit
Bose-Einstein correlation measurements of 200AGeV S+S and 160AGeV Pb+Pb.
Transverse flow does not show up in the Bose-Einstein measurements. The
decrease of the effective transverse radius parameters with increasing
transverse average momentum of the particle pair is largely due to the effect
of resonance decays.


title:
Lambda flow in heavy-ion collisions: the role of final-state
  interactions

abstract:
  Lambda flow in Ni+Ni collisions at SIS energies is studied in the
relativistic transport model (RVUU 1.0). It is found that for primordial
lambdas the flow is considerably weaker than proton flow. The inclusion of
final-state interactions, especially the propagation of lambdas in mean-field
potential, brings the lambda flow close to that of protons. An accurate
determination of lambda flow in heavy-ion experiments is shown to be very
useful for studying lambda properties in dense matter.


title:
Nuclear gluon shadowing via dileptons from open charm decay in $p+A$ at
  $\sqrt s=200$ AGeV

abstract:
  Opposite-sign lepton pairs ($ee$,$e\mu$ and $\mu\mu$) from open charm decay
are proposed as a measure of nuclear shadowing effects. Via an approximate
scaling the ratio of the dilepton spectra from $p+A$ to those from $pp$
reflects the shadowing function well. We show that the required measurements
are feasible at the Relativistic Heavy ion Collider (RHIC) by considering the
backgrounds according to the proposed PHENIX detector geometry.


title: Approximate symmetries in nuclei and the $2\nu\beta\beta$-decay rate

abstract:
  A nonstandard method for calculating the nuclear $2\nu\beta\beta$ - decay
amplitude is proposed. The method is based on the explicit use of those
approximate symmetries of a nuclear hamiltonian, which correspond to the
operators of allowed $\beta$ -- transitions. Within the framework of the
proposed method the mentioned amplitude is calculated for a wide range of
nuclei. The model parameters used in calculations are taken from independent
data. Calculated \bb half-lifes are compared with known experimental data.


title: Strangeness Production via Parton Cascade

abstract:
  We study pre-equilibrium strangeness production at RHIC energies in a new
parton cascade. Starting with the turbulent glue HIJING initial conditions we
investigate the interplay between mini-jet and soft beam jet gluons for
strangeness production prior to hadronization, and show the importance of soft
beam jet gluons in the strangeness production.


title:
Investigation of the neutron structure function via semi-inclusive deep
  inelastic electron scattering off the deuteron

abstract:
  The production of slow nucleons in semi-inclusive deep inelastic electron
scattering off the deuteron is investigated in the region $x \gsim 0.3$ for
kinematical conditions accessible at $HERA$. Within the spectator mechanism the
semi-inclusive cross section exhibits a scaling property, which can be used as
a model-independent test of the dominance of the spectator mechanism itself,
providing in this way an interesting tool to investigate the neutron structure
function. The possibility of extracting model-independent information on the
neutron to proton structure function ratio from semi-inclusive experiments is
also illustrated.


title: Magnetically Catalyzed Fusion

abstract:
  We calculate the reaction cross-sections for the fusion of hydrogen and
deuterium in strong magnetic fields as are believed to exist in the atmospheres
of neutron stars. We find that in the presence of a strong magnetic field ($B
\gsim 10^{12}$G), the reaction rates are many orders of magnitude higher than
in the unmagnetized case. The fusion of both protons and deuterons are
important over a neutron star's lifetime for ultrastrong magnetic fields ($B
\sim 10^{16}$G). The enhancement may have dramatic effects on thermonuclear
runaways and bursts on the surfaces of neutron stars.


title:
Evaluation of the mean intensity of the P-odd mixing of nuclear compound
  states

abstract:
  A temperature version of the shell-optical-model approach for describing the
low-energy compound-to-compound transitions induced by external single-particle
fields is given. The approach is applied to evaluate the mean intensity of the
P-odd mixing of nuclear compound states. Unified description for the mixing and
electromagnetic transitions allows one to evaluate the mean intensity without
the use of free parameters. The valence-mechanism contribution to the mentioned
intensity is also evaluated. Calculation results are compared with the data
deduced from cross sections of relevant neutron-induced reactions.


title: Tagged nuclear structure functions with $HERMES$

abstract:
  The production of slow nucleons in semi-inclusive deep inelastic electron
scattering off nuclei, $A(e, e'N)X$, is analyzed for kinematical conditions
accessible at $HERA$ with the $HERMES$ detector. The sensitivity of the
semi-inclusive cross section to possible medium-dependent modifications of the
nucleon structure function is illustrated.


title: Strong decays of qqq baryons

abstract:
  We study strong decays of nonstrange baryons by making use of the algebraic
approach to hadron structure. Within this framework we derive closed
expressions for decay widths in an elementary-meson emission model and use
these to analyze the experimental data for N* -> N + pi, N* -> Delta + pi, N*
-> N + eta, Delta* -> N + pi, Delta* -> Delta + pi and Delta* -> Delta + eta
decays.


title: Multiquark Systems in a Constituent Quark Model with Chiral Dynamics

abstract:
  We discuss the stability of multiquark systems within the recent model of
Glozman et al. where the chromomagnetic hyperfine interaction is replaced by
pseudoscalar-meson exchange. We find that such an interaction binds a heavy
tetraquark system $QQ\bar q\bar q$ ($Q=c, b$ and $q=u, d)$ by $0.2-0.4$ GeV.
This is at variance with results of previous models where $cc\bar q\bar q$ is
unstable.


title: Chiral Transparency

abstract:
  Color transparency is the vanishing of initial and final state interactions,
predicted by QCD to occur in high momentum transfer quasielastic nuclear
reactions. For specific reactions involving nucleons, the initial and final
state interactions are expected to be dominated by exchanges of pions. We argue
that these interactions are also suppressed in high momentum transfer nuclear
quasielastic reactions; this is ``chiral transparency". We show that studies of
the $e ^3He \to e'\Delta^{++} nn$ reaction could reveal the influence of chiral
transparency.


title: Variation of hadron masses in finite nuclei

abstract:
  Using a self-consistent, Hartree description for both infinite nuclear matter
and finite nuclei based on a relativistic quark model (the quark-meson coupling
model), we investigate the variation of the masses of the non-strange vector
mesons, the hyperons and the nucleon in infinite nuclear matter and in finite
nuclei.


title:
Generalized polarizabilities and the spin-averaged amplitude in virtual
  Compton scattering off the nucleon

abstract:
  We discuss the low-energy behavior of the spin-averaged amplitude of virtual
Compton scattering (VCS) off a nucleon.
  Based on gauge invariance, Lorentz invariance and the discrete symmetries, it
is shown that to first order in the frequency of the final real photon only two
generalized polarizabilities appear.
  Different low-energy expansion schemes are discussed and put into
perspective.


title: Quark Degrees of Freedom in Finite Nuclei

abstract:
  Properties of finite nuclei are investigated based on relativistic Hartree
equations which have been derived from a relativistic quark model of the
structure of bound nucleons. Nucleons are assumed to interact through the
(self-consistent) exchange of scalar ($\sigma$) and vector ($\omega$ and
$\rho$) mesons at the quark level. The coupling constants and the mass of the
$\sigma$-meson are determined from the properties of symmetric nuclear matter
and the rms charge radius in $^{40}$Ca. Calculated properties of static,
closed-shell nuclei, as well as symmetric nuclear matter are compared with
experimental data and with the results of Quantum Hadrodynamics (QHD).


title: Local gauge invariance implies Siegert's hypothesis

abstract:
  The nonrelativistic Ward-Takahashi identity, a consequence of local gauge
invariance in quantum mechanics, shows the necessity of exchange current
contributions in case of nonlocal and/or isospin-dependent potentials. It also
implies Siegert's hypothesis: in the nonrelativistic limit, two-body charge
densities identically vanish. Neither current conservation, which follows from
global gauge invariance, nor the constraints of (lowest order) relativity are
sufficient to arrive at this result. Furthermore, a low-energy theorem for
exchange contributions is established.


title:
Coherent eta photoproduction on the deuteron in the $S_{11}$ resonance
  region

abstract:
  Coherent eta photoproduction on the deuteron is studied in the $S_{11}$
resonance region neglecting eta rescattering and two-body processes. For the
elementary reaction on the nucleon, we have considered the dominant
$S_{11}(1535)$ resonance and as background the nucleon pole terms as well as
$\rho$ and $\omega$ meson exchange. We have studied the influence of different
choices for the neutron resonance amplitude, different prescriptions for fixing
the invariant mass of the resonance amplitude and different methods for
deriving the elementary production amplitude for an arbitrary reference frame.


title:
QCD sum rules for \rho, \omega, \phi meson-nucleon scattering lengths
  and the mass shifts in nuclear medium

abstract:
  A new QCD sum rule analysis on the spin-isospin averaged $\rho$, $\omega$ and
$\phi$ meson-nucleon scattering lengths is presented. By introducing the
constraint relation on the the low energy limit of the vector-current nucleon
forward scattering amplitude, we get $a_\rho=-0.47\pm 0.05$ fm,
$a_\omega=-0.41\pm 0.05$ fm and $a_\phi=-0.15\pm 0.02$ fm, which suggests that
these V-N interactions are attractive. It is also proved that the previous
studies on the mass shift of these vector mesons in the nuclear medium are
essentially the ones obtained from these scattering lengths in the linear
density approximation.