title:
Extended Hauser-Feshbach Method for Statistical Binary-Decay of
  Light-Mass Systems

abstract:
  An Extended Hauser-Feshbach Method (EHFM) is developed for light heavy-ion
fusion reactions in order to provide a detailed analysis of all the possible
decay channels by including explicitly the fusion-fission phase-space in the
description of the cascade chain. The mass-asymmetric fission component is
considered as a complex-fragment binary-decay which can be treated in the same
way as the light-particle evaporation from the compound nucleus in
statistical-model calculations. The method of the phase-space integrations for
the binary-decay is an extension of the usual Hauser-Feshbach formalism to be
applied to the mass-symmetric fission part. The EHFM calculations include
ground-state binding energies and discrete levels in the low excitation-energy
regions which are essential for an accurate evaluation of the phase-space
integrations of the complex-fragment emission (fission). In the present
calculations, EHFM is applied to the first-chance binary-decay by assuming that
the second-chance fission decay is negligible. In a similar manner to the
description of the fusion-evaporation process, the usual cascade calculation of
light-particle emission from the highly excited complex fragments is applied.
This complete calculation is then defined as EHFM+CASCADE. Calculated
quantities such as charge-, mass- and kinetic-energy distributions are compared
with inclusive and/or exclusive data for the $^{32}$S+$^{24}$Mg and
$^{35}$Cl+$^{12}$C reactions which have been selected as typical examples.
Finally, the missing charge distributions extracted from exclusive measurements
are also successfully compared with the EHFM+CASCADE predictions.


title:
Soft transverse expansion in Pb(158 AGeV) on Pb collisions:
  preequilibrium motion or 1st order phase transition?

abstract:
  Transverse expansion of centrally produced matter in Pb on Pb collisions at
beam energies around 158 AGeV appears to be rather `soft'. Two possible reasons
-- an extended preequilibrium stage and a first order phase transition from a
quark-gluon-plasma into hadronic matter -- are discussed. The softening of
transverse expansion caused by preequilibrium dynamics is estimated with the
aid of the transport model RQMD which does not contain a first order phase
transition. It is found that the anisotropy of transverse flow in non-central
reactions is very different in the preequilibrium and hydrodynamic scenarios
even if the latter are based on a strong 1st order transition.


title: Pion Suppression in Nuclear Collisions

abstract:
  The pion multiplicity per participating nucleon in central nucleus-nucleus
collisions at the energies 2-15 A GeV is significantly smaller than in
nucleon-nucleon interactions at the same collision energy. This effect of pion
suppression is argued to appear due to the evolution of the system produced at
the early stage of heavy-ion collisions towards a local thermodynamic
equilibrium and further isentropic expansion.


title: Confinement and scaling in deep inelastic processes

abstract:
  We show that parton confinement in the final state generates large $1/Q^2$
(higher twist) corrections to Bjorken scaling. For treatment of these
non-perturbative effects, we derive a new expansion in powers of $1/Q^2$ for
the structure function that is free of infra-red singularities and which
reduces corrections to the leading term. The leading term represents scattering
from an off-mass-shell parton, which keeps the same virtual mass in the final
state. This term appears as a function of a new variable $\bar x(x,Q^2)$, which
coincides with the Bjorken variable x for $Q^2\to\infty$. Analysis of the data
shows excellent scaling at large x, where power corrections are dominant. The
approach accommodates also the QCD logarithmic corrections and the behavior of
the structure functions is well reproduced within a wide kinematical range.
Since the new scaling variable $\bar x(x,Q^2)$ incorporates the higher twist
effects, it allows us to extract the ratio $F_2^n(x)/F_2^p(x)$ for $x\to 1$
from the available data at moderate Q^2.


title: Meson-exchange contributions to the nuclear charge operator

abstract:
  The role of the meson-exchange current correction to the nuclear charge
operator is studied in electron scattering processes involving the excitation
of medium and heavy nuclei to energies up to the quasi-elastic peak. The effect
of these contributions in the quasi-free electron scattering process is a
reduction of at most a 3% in the longitudinal response at the energy of the
peak, a value which is below the experimental error and must not be taken into
account in calculations in this energy region. On the other hand, the
excitation of low-lying nuclear levels of neutronic character shows, with
respect to the protonic ones, a considerable effect due to the inclusion of the
two-body term in the charge operator. More realistic calculations, such as
those performed in the random-phase approximation framework, give rise to a
mixing of one particle-one hole configurations of both kinds which reduce these
effects. However, it has been found that the excitation of some of these levels
is sizeably affected by the meson-exchange contribution. More precise
experimental data concerning some of these states, such as e.g. the high-spin
states in 208Pb, could throw some light in the problem of a more feasible
determination of these effects and, as a consequence, could provide an
alternative procedure to obtain the charge neutron form factor.


title:
P-Wave Polarization of the $\rho$-Meson and the Dilepton Spectrum in
  Dense Matter

abstract:
  We study the $p$-wave polarization operator of the $\rho$-meson due to $\rho
N$ interactions via the $N^*$ (1720) and $\Delta (1905)$ resonances and compute
the corresponding production rate for $e^+e^-$-pairs at finite temperature and
baryon density. At high baryon density we find a significant shift of the
spectrum to lower invariant masses.


title:
Ghost poles in the nucleon propagator in the linear-sigma model approach
  and its role in pion-nucleon low-energy theorems

abstract:
  Complex mass poles, or ghost poles, are present in the Hartree-Fock solution
of the Schwinger-Dyson equation for the nucleon propagator in renormalizable
models with Yukawa-type meson-nucleon couplings, as shown many years ago by
Brown, Puff, and Wilets (BPW). These ghosts violate basic theorems of quantum
field theory and their origin is related to the ultraviolet behavior of the
model interactions. Recently, Krein et.al, proved that the ghosts disappear
when vertex corrections are included in a self-consistent way, softening the
interaction sufficiently in the ultraviolet region. In previous studies of
pion-nucleon scattering using "dressed" nucleon propagator and bare vertices,
did by Nutt and Wilets in the 70's (NW), it was found that if these poles are
explicitly included, the value of the isospin-even amplitude A+ is satisfied
within 20% at threshold. The absence of a theoretical explanation for the
ghosts and the lack of chiral symmetry in these previous studies led us to
re-investigate the subject using the approach of the linear-sigma model and
study the interplay of low-energy theorems for pion-nucleon scattering and
ghost poles. For bare interaction vertices we find that ghosts are present in
this model as well and that the A+ value is badly described. As a first
approach to remove these complex poles, we dress the vertices with
phenomenological form factors and a reasonable agreement with experiment is
achieved. In order to fix the two cutoff parameters, we use the A+ value for
the chiral limit (m_pion -> 0) and the experimental value of the isoscalar
scattering length. Finally, we test our model by calculating the phase shifts
for the S waves and we find a good agreement at threshold.


title:
The longitudinal and transverse responses in the inclusive electron
  scattering

abstract:
  The splitting between the charge-longitudinal and spin-transverse responses
is explained in a model whose inputs are the effective interactions in the
particle-hole channels in the first order boson loop expansion. The interplay
between $\omega$-meson exchange and box diagrams mainly governs the
longitudinal response, while in the transverse one the direct $\Delta$
excitations almost cancel the one-loop correction and the response is ruled by
the $\rho$-meson rescattering.


title:
Coherent eta-photoproduction from nuclei in a relativistic impulse
  approximation approach

abstract:
  We study coherent eta-photoproduction from nuclei in a relativistic impulse
approximation approach. For the elementary production amplitude we use a
standard relativistic parameterization based on a set of four Lorentz- and
gauge-invariant amplitudes. The photonuclear amplitude is evaluated without
recourse to a nonrelativistic reduction; the full relativistic structure of the
amplitude is maintained. On general arguments we show that the coherent process
is sensitive to only one of the elementary amplitudes. Moreover, we show that
the nuclear structure information is fully contained in the ground-state tensor
density. The tensor density is evaluated in a mean-field approximation to the
Walecka model and it is shown to be sensitive to relativistic effects.
Distortion effects are incorporated through an eta-nucleus optical potential
that is computed in a simple t-rho approximation.


title:
Calculations of scattering lengths in four-nucleon system on the basis
  of cluster reduction method for Yakubovsky equations

abstract:
  The cluster reduction method for the Yakubovsky equations in configuration
space is used for calculations of zero-energy scattering in four-nucleon
system. The main idea of the method consists in making use of expansions for
the Yakubovsky amplitudes onto the basis of the Faddeev components for the
two-cluster sub-Hamiltonian eigenfunctions. The expansions reduce the original
equations to ones for the functions depending on the relative coordinates
between the clusters. On the basis of the resulting equations the N-(NNN)
zero-energy scattering problems are solved numerically with the MT I-III model
for N-N forces and neglecting the Coulomb interaction between protons.


title: On the validity of the O(18) coupling scheme in N~Z nuclei

abstract:
  Wave-functions from the newly proposed O(18) coupling scheme in IBM-3 are
compared with those from a numerical calculation fitted to some Ni, Zn, Ge and
Se nuclei.


abstract:
  We present a unitary and gauge-invariant model with coupled channels, which
provides a consistent description of pion photoproduction off nucleons in the
E$_{0+}$ channel and eta-meson photoproduction off protons and deuterons. An
effective field theory with hadrons and photons is constructed, which includes
non-resonant Born terms as well as the S$_{11}$(1535) and S$_{11}$(1650) baryon
resonances. Due to the coupling between the channels, the production of
eta-mesons is strongly affected by the S$_{11}$(1650) although its direct
coupling to the $\eta$N channel is negligible. The rho- and omega-meson
exchange terms are important for achieving a consistent description of both
pion- and photon-induced reactions.


title: What can we learn from three-pion interferometry ?

abstract:
  We address the question which additional information on the source shape and
dynamics can be extracted from three-particle Bose-Einstein correlations. For
chaotic sources the true three-particle correlation term is shown to be
sensitive to the momentum dependence of the saddle point of the source and to
its asymmetries around that point. For partially coherent sources the
three-pion correlator allows to measure the degree of coherence without
contamination from resonance decays. We derive the most general Gaussian
parametrization of the two- and three-particle correlator for this case and
discuss the space-time interpretation of the corresponding parameters.


title: On the Gerasimov-Drell-Hearn sum rule for the deuteron

abstract:
  The Gerasimov-Drell-Hearn sum rule is evaluated for the deuteron by explicit
integration up to a photon energy of 550 MeV including contributions from the
photodisintegration channel and from coherent and incoherent single pion
production as well. The photodisintegration channel converges fast enough in
this energy range and gives a large negative contribution, essentially from the
$^1S_0$ resonant state near threshold. Its absolute value is about the same
size than the sum of proton and neutron GDH values. It is only partially
cancelled by the single pion production contribution. But the incoherent
channel has not reached convergence at 550 MeV.


title: Coherence length of neutron superfluids

abstract:
  The coherence length of superfluid neutron matter is calculated from the
microscopic BCS wavefunction of a Cooper pair in momentum space making use of
the Bonn meson-exchange potential. We find that the coherence length is
proportional to the Fermi momentum-to pairing gap ratio, in good agreement with
simple estimates used in the literature, and we establish the appropriate
fitting constants using our numerical data. Our calculations can be applied to
the problem of inhomogeneous superfluidity of hadronic matter in the crust of a
neutron star.


title: Polarized deuteron structure functions at small x

abstract:
  We investigate shadowing corrections to the polarized deuteron structure
functions g_1^d and b_1. In the kinematic domain of current fixed target
experiments we observe that shadowing effects in g_1^d are approximately twice
as large as for the unpolarized structure function F_2^d. Furthermore, we find
that b_1 is surprisingly large at x < 0.1 and receives dominant contributions
from coherent double scattering.


title: Three-potential formalism for the three-body Coulomb scattering problem

abstract:
  We propose a three-potential formalism for the three-body Coulomb scattering
problem. The corresponding integral equations are mathematically well-behaved
and can succesfully be solved by the Coulomb-Sturmian separable expansion
method. The results show perfect agreements with existing low-energy $n-d$ and
$p-d$ scattering calculations.


title: Three-alpha structures in C-12

abstract:
  We search for three-alpha resonances in C-12 by using the complex scaling
method in a microscopic cluster model. All experimentally known low-lying
natural-parity states are localized. For the first time we unambiguously show
that the 0+_2 state in C-12, which plays an important role in stellar
nucleosynthesis, is a genuine three-alpha resonance.


title:
On the S-wave piD-scattering length in the relativistic field theory
  model of the deuteron

abstract:
  The S-wave scattering length of the strong pion-deuteron (pi D) scattering is
calculated in the relativistic field theory model of the deuteron suggested in
[1,2].The theoretical result agrees well with the experimental data. The
important role of the Delta-resonance contribution to the elastic pi
D-scattering is confirmed.


title: New representation of orbital motion with arbitrary angular momenta

abstract:
  A new formulation is presented for a variational calculation of $N$-body
systems on a correlated Gaussian basis with arbitrary angular momenta. The
rotational motion of the system is described with a single spherical harmonic
of the total angular momentum $L$, and thereby needs no explicit coupling of
partial waves between particles. A simple generating function for the
correlated Gaussian is exploited to derive the matrix elements. The formulation
is applied to various Coulomb three-body systems such as $e^-e^-e^+, tt\mu,
td\mu$, and $\alpha e^-e^-$ up to $L=4$ in order to show its usefulness and
versatility. A stochastic selection of the basis functions gives good results
for various angular momentum states.


title:
Resonance Production on Nuclei at High Energies: Nuclear-Medium Effects
  and Space-Time Picture

abstract:
  The influence of nuclear matter on the properties of coherently produced
resonances is discussed. It is shown that, in general, the mass distribution of
resonance decay products has a two-component structure corresponding to decay
outside and inside the nucleus. The first (narrow) component of the amplitude
has a Breit-Wigner form determined by the vacuum values of mass and width of
the resonance. The second (broad) component corresponds to interactions of the
resonance with the nuclear medium. It can be also described by a Breit-Wigner
shape with parameters depending e.g. on the nuclear density and on the cross
section of the resonance-nucleon interaction. The resonance production is
examined both at intermediate energies, where interactions with the nucleus can
be considered as a series of successive local rescatterings, and at high
energies, $E>E_{crit}$, where a change of interaction picture occurs. This
change of mechanisms of the interactions with the nucleus is typical for the
description within the Regge theory approach and is connected with the nonlocal
nature of the reggeon interaction.


title: Transport coefficients for shape degrees in terms of Cassini ovaloids

abstract:
  Previous computations of the potential landscape with the shapes
parameterized in terms of Cassini ovaloids are extended to collective dynamics
at finite excitations. Taking fission as the most demanding example of large
scale collective motion, transport coefficients are evaluated along a fission
path. We concentrate on those for average motion, namely stiffness C, friction
\gamma and inertia M. Their expressions are formulated within a locally
harmonic approximation and the help of linear response theory. Different
approximations are examined and comparisons are made both with previous
studies, which involved different descriptions of single particle dynamics, as
well as with macroscopic models. Special attention is paid to an appropriate
definition of the deformation of the nuclear density and its relation to that
of the single particle potential. For temperatures above 3 MeV the inertia
agrees with that of irrotational flow to less than a factor of two, but shows
larger deviations below, in particular in its dependence on the shape. Also
friction exhibits large fluctuations along the fission path for small
excitations. They get smoothed out above 3 - 4 MeV where \gamma attains values
in the range of the wall formula. For T > (or=) 2 MeV the inverse relaxation
time \beta = \gamma /M turns out to be rather insensitive to the shape and
increases with T.


title: Reply to Baur's and Bertulani's Comment

abstract:
  Shortcomings of a momentum-space treatment of strong absorption, as discussed
in the previous Comment [nucl-th/9611025], are only of concern at low
projectile energies, $\gamma$< 1.5. At intermediate and high energies, for
which the quantum-mechanical equivalent-photon spectrum is intended, the
quantum-mechanical cross sections are reduced relative to the semi-classical
results whether one treats strong effects via a momentum-space or an
impact-parameter (spatial) cut-off. At these energies the origin of the
discrepancy between the predictions of full quantuym-mechanical and the
semi-classical calulations cannot be traced to differences in the treatment of
strong-interaction effects. Rather, they arise from quantum effects neglected
in the semi-classical calculations.


title:
Hadronic Annihilation Decay Rates of P-wave Heavy Quarkonia with Both
  Relativistic and QCD Radiative Corrections

abstract:
  Hadronic annihilation decay rates of P-wave heavy quarkonia are given to
next-to-leading order in both $\alpha_s$ and $v^2$. They include ten
nonperturbative parameters, which can be rigorously defined as the matrix
elements of color-singlet and color-octet operators in NRQCD. We expect these
papameters will be determined from lattice calculations in future.


title: The Deconfinement Phase Transition in Asymmetric Matter

abstract:
  We study the phase transition of asymmetric hadronic matter to a quark-gluon
plasma within the framework of a simple two-phase model. The analysis is
performed in a system with two conserved charges (baryon number and isospin)
using the stability conditions on the free energy, the conservation laws and
Gibbs' criteria for phase equilibrium. The EOS is obtained in a separate
description for the hadronic phase and for the quark-gluon plasma. For the
hadrons, a relativistic mean-field model calibrated to the properties of
nuclear matter is used, and a bag-model type EOS is used for the quarks and
gluons. The model is applied to the deconfinement phase transition that may
occur in matter created in ultra-relativistic collisions of heavy ions. Based
on the two-dimensional coexistence surface (binodal), various phase separation
scenarios and the Maxwell construction through the mixed phase are discussed.
In the framework of the two-phase model the phase transition in asymmetric
matter is continuous (second-order by Ehrenfest's definition) in contrast to
the discontinuous (first-order) transition of symmetric systems.


title: Variational Field Theoretic Approach to Relativistic Scattering

abstract:
  Nonperturbative polaron variational methods are applied, within the so-called
particle or worldline representation of relativistic field theory, to study
scattering in the context of the scalar Wick - Cutkosky model. Important
features of the variational calculation are that it is a controlled
approximation scheme valid for arbitrary coupling strengths, the Green
functions have all the cuts and poles expected for the exact result at any
order in perturbation theory and that the variational parameters are
simultaneously sensitive to the infrared as well as the ultraviolet behaviour
of the theory. We generalize the previously used quadratic trial action by
allowing more freedom for off-shell propagation without a change in the
on-shell variational equations and evaluate the scattering amplitude at first
order in the variational scheme. Particular attention is paid to the
$s$-channel scattering near threshold because here non-perturbative effects can
be large. We check the unitarity of a our numerical calculation and find it
greatly improved compared to perturbation theory and to the zeroth order
variational results.


title: Algebraic model of baryon resonances

abstract:
  We discuss recent calculations of electromagnetic form factors and strong
decay widths of nucleon and delta resonances. The calculations are done in a
collective constituent model of the nucleon, in which the baryons are
interpreted as rotations and vibrations of an oblate top.


title: Scalar mesons nonet in a scaled effective Lagrangian

abstract:
  A scaled SU(3) Nambu - Jona-Lasinio Lagrangian is used to compute the mass of
the nine scalar mesons in the vacuum and the mass of the gluball. It is shown
that a suitable choice of the vacuum gluon condensate allows to reproduce the
experimental masses of the scalar mesons except for the {$K^*_{0}$}(1430). This
choice corresponds to a weak coupling between the gluon and quark condensates,
giving a {$f_{0}$}(1500) or a {$f_{J}$}(1710) which is nearly a pure glueball.


title:
Symmetries of anisotropic harmonic oscillators with rational ratios of
  frequencies and their relations to U(N) and O(N+1)

abstract:
  The concept of bisection of a harmonic oscillator or hydrogen atom, used in
the past in establishing the connection between U(3) and O(4), is generalized
into multisection (trisection, tetrasection, etc). It is then shown that all
symmetries of the N-dimensional anisotropic harmonic oscillator with rational
ratios of frequencies (RHO), some of which are underlying the structure of
superdeformed and hyperdeformed nuclei, can be obtained from the U(N) symmetry
of the corresponding isotropic oscillator with an appropriate combination of
multisections. Furthermore, it is seen that bisections of the N-dimensional
hydrogen atom, which possesses an O(N+1) symmetry, lead to the U(N) symmetry,
so that further multisections of the hydrogen atom lead to the symmetries of
the N-dim RHO. The opposite is in general not true, i.e. multisections of U(N)
do not lead to O(N+1) symmetries, the only exception being the occurence of
O(4) after the bisection of U(3).


title: Symmetries in nuclei and molecules

abstract:
  Recent progress in two different fronts is reported. First, the concept of
bisection of a harmonic oscillator (HO) or hydrogen atom (HA), used in the past
in establishing the connection between U(3) and O(4), is generalized into
multisection (trisection, tetrasection, etc). It is then shown that all
symmetries of the N-dim anisotropic HO with rational ratios of frequencies
(RHO), some of which are underlying the structure of superdeformed and
hyperdeformed nuclei, can be obtained from the U(N) symmetry of the
corresponding isotropic HO with an appropriate combination of multisections.
Furthermore, it is seen that bisections of the N-dim HA, which possesses an
O(N+1) symmetry, lead to the U(N) symmetry, so that further multisections of
the HA lead to the symmetries of the N-dim RHO. Second, it is shown that there
is evidence that the recently observed in superdeformed nuclear bands $\Delta
I=4$ bifurcation is also occuring in rotational bands of diatomic molecules. In
addition there is evidence that a $\Delta I=8$ bifurcation, of the same order
of magnitude as the $\Delta I=4$ one, is observed in superdeformed nuclear
bands and rotational bands of diatomic molecules.


title: Investigations of the broken SU(3) symmetry in deformed even-even nuclei

abstract:
  A collective vector-boson model with broken SU(3) symmetry is applied to
several deformed even-even nuclei. The model description of ground and $\gamma$
bands together with the corresponding B(E2) transition probabilities is
investigated within a broad range of SU(3) irreducible representations (irreps)
$(\lambda ,\mu )$. The SU(3)-symmetry characteristics of rotational nuclei are
analyzed in terms of the bandmixing interactions.


title: Lepton-Pair Production in Virtual Compton Scattering off the Proton

abstract:
  We show that lepton-pair production in Virtual Compton Scattering offers,
through interference with the well-known Bethe-Heitler process, a sensitive
probe to learn the longitudinal response of resonances and the electromagnetic
nucleon form factors. This interference can be measured directly in terms of an
asymmetry. The role of off-shell effects in the N-N-$\gamma$ vertices is
investigated as well. An additional N-N-$\gamma -\gamma$ contact term in the
amplitude, included to ensure gauge invariance of the model, cancels a
substantial part of the off-shell effects.


title:
Formation of Deeply Bound 1s Pionic States in the $^{206}$Pb(d,$^3$He)
  Reaction

abstract:
  Recently, deeply bound pionic states were found experimentally in (d,$^3$He)
reactions on $^{208}$Pb. The observed spectrum showed an excellent agreement
with the DWIA calculation and the dominant peak was attributed to the pionic 2p
state contribution. We studied theoretically $^{206}$Pb(d,$^3$He) reactions
within the same model, and found that it is very likely to observe the pionic
1s state as an isolated peak in the $^{206}$Pb(d,$^3$He) reaction with feasible
energy resolution and statistics.


title: Shell Model for Warm Rotating Nuclei

abstract:
  In order to provide a microscopic description of levels and E2 transitions in
rapidly rotating nuclei with internal excitation energy up to a few MeV, use is
made of a shell model which combines the cranked Nilsson mean-field and the
residual surface delta two-body force. The damping of collective rotational
motion is investigated in the case of a typical rare-earth nucleus, namely \Yb.
It is found that rotational damping sets in at around 0.8 MeV above the yrast
line, and the levels which form rotational band structures are thus limited. We
predict at a given rotational frequency existence of about 30 rotational bands
of various lengths, in overall agreement with the experimental findings. The
onset of the rotational damping proceeds quite gradually as a function of the
internal excitation energy. The transition region extends up to around 2 MeV
above yrast and it is characterized by the presence of scars of discrete
rotational bands which extend over few spin values and stand out among the
damped transitions, and by a two-component profile in the $E_\gamma -E_\gamma$
correlation. The important role played by the high-multipole components of the
two-body residual interaction is emphasized.


title: ``Pressure Equilibration'' in Ultrarelativistic Heavy Ion Collisions

abstract:
  We study the time scale for pressure equilibration in heavy ion collisions at
AGS energies within the three-fluid hydrodynamical model and a microscopic
cascade model (UrQMD). We find that kinetic equilibrium is reached in both
models after a time of 5 fm/c (center-of-mass time). Thus, observables which
are sensitive to the early stage of the reaction differ considerably from the
expectations within the instant thermalization scenario (one-fluid
hydrodynamical model).


title: Equilibration in Heavy Ion Collisions at LHC and at RHIC

abstract:
  We consider the evolution of a parton plasma created in Au+Au collisions at
LHC and at RHIC energies. Using Boltzmann equation, relaxation time
approximation and perturbative QCD, we show the physics of both thermal and
chemical equilibration in a transparent manner. In particular, we show
inelastic processes are, contrary to common assumption, more important than
elastic processes, the state of equilibration of the system can compensate for
some powers of $\a_s$ for the purpose of equilibration, the two-stage
equilibration scenario is, barring any unknown non-perturbative effects,
inevitable and is an intrinsic feature of perturbative QCD, and gluon
multiplication is the leading process for entropy generation.


title:
Self-consistent description of $\Lambda$ hypernuclei in the quark-meson
  coupling model

abstract:
  The quark-meson coupling (QMC) model, which has been successfully used to
describe the properties of both finite nuclei and infinite nuclear matter, is
applied to a study of $\Lambda$ hypernuclei. With the assumption that the
(self-consistent) exchanged scalar, and vector, mesons couple only to the u and
d quarks, a very weak spin-orbit force in the $\Lambda$-nucleus interaction is
achieved automatically. This is a direct consequence of the SU(6) quark model
wave function of the $\Lambda$ used in the QMC model. Possible implications and
extensions of the present investigation are also discussed.


title:
Equation of state of asymmetric nuclear matter and collisions of
  neutron-rich nuclei

abstract:
  The ratio of pre-equilibrium neutrons to protons from collisions of
neutron-rich nuclei is studied as a function of their kinetic energies. This
ratio is found to be sensitive to the density dependence of the nuclear
symmetry energy, but is independent of the compressibility of symmetric nuclear
matter and the in-medium nucleon-nucleon cross sections. The experimental
measurement of this ratio thus provides a novel means for determining the
nuclear equation of state of asymmetric nuclear matter.


title:
Chemical and mechanical instabilities in hot, isospin-asymmetric nuclear
  matter

abstract:
  Using phenomenological equations of state, we study the chemical and
mechanical instabilities in hot isospin-asymmetric nuclear matter. Both
instabilities are found to depend strongly on the isospin asymmetry of the
nuclear matter. For a chemically and mechanically stable asymmetric nuclear
matter, a lower neutron excess is found in the liquid phase than in the gas
phase. Furthermore, the neutron excess in the mixed phase at densities between
that of the liquid and the gas phases is limited by certain maximum value.
Also, for the nuclear equations of state considered here the boundary of
chemical instability in the pressure-density plane is found to be more extended
than that of mechanical instability. However, locations of these boundaries
depend sensitively on both the bulk compressibility of nuclear matter and the
density dependence of the symmetry energy.


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

abstract:
  It is shown that data on pion and strangeness production in central
nucleus-nucleus collisions are consistent with the hypothesis of a Quark Gluon
Plasma formation between 15 A GeV/c (BNL AGS) and 160 A GeV/c (CERN SPS)
collision energies. The experimental results interpreted in the framework of a
statistical approach indicate that the effective number of degrees of freedom
increases by a factor of about 3 in the course of the phase transition and that
the plasma created at CERN SPS energy may have a temperature of about 280 MeV
(energy density $\approx$ 10 GeV/fm^3). Experimental studies of central Pb+Pb
collisions in the energy range 20-160 A GeV/c are urgently needed in order to
localize the threshold energy, and study the properties of the QCD phase
transition.


title: A Comment on the Radiative Decays of the $\Lambda (1405)$

abstract:
  We examine the radiative decays of the Lambda (1405) to octet baryons, Lambda
+ gamma and Sigma + gamma. In the limit of SU(3) symmetry the decay rates for
these two modes are related, and we compute the leading correction to the
relation in chiral perturbation theory. Such measurements will allow the sign
of the strong coupling $g_{\Lambda^*}$ to be determined. The SU(3) violating
radiative decay to the baryon decuplet Sigma* + gamma dominated by one-loop
graphs is also discussed. Experiments planned for the Jefferson Laboratory
should be able to measure some, if not all, of the processes considered.


title: $\eta-\eta^{\prime}$ Mixture in Chiral Bag

abstract:
  The $\eta-\eta^{\prime}$ mixture is discussed in the chiral bag model to
calculate the pseudoscalar octet-singlet mixing angle consistent with the
experimental data. The color anomaly is taken into account with the modified
boundary conditions, which shows the relation between the $\eta^{\prime}$ mass
and the gluon condensate inside the chiral bag. We show, however, that
$\eta-\eta^{\prime}$ mixing angle can follow the Cheshire Cat Principle, i.e.,
insensitivity to the bag radius.


title: (Anti-) Deuteron Coalescence in Ultrarelativistic Heavy Ion Collisions

abstract:
  In the frame of the Wigner function formalism, we derive a coalescence model
to use with a hydrodynamical picture of the reaction zone


title: Particle Interferometry in Heavy-Ion Collisions

abstract:
  By measuring hadronic single-particle spectra and two-particle correlations
in heavy-ion collisions, the size and dynamical state of the collision fireball
at freeze-out can be reconstructed. I discuss the relevant theoretical methods
and their limitations. By applying the formalism to recent pion correlation
data from Pb+Pb collisions at CERN we demonstrate that the collision zone has
undergone strong transverse growth before freeze-out (by a factor 2-3 in each
direction), and that it expands both longitudinally and transversally. From the
thermal and flow energy density at freeze-out the energy density at the onset
of transverse expansion can be estimated from conservation laws. It comfortably
exceeds the critical value for the transition to color deconfined matter.


title: QRPA and its extensions in a solvable model

abstract:
  An exactly solvable model is introduced, which is equivalent to the exact
shell-model treatment of protons and neutrons in a single j-shell for
Fermi-type excitations. Exact energies, quasiparticle numbers and double beta
decay Fermi amplitudes are computed and compared with the results of both the
standard quasiparticle random phase approximation (QRPA) and the renormalized
one (RQRPA), and also with those corresponding to the hamiltonian in the
quasiparticle basis (qp). A zero excitation energy state is found in the exact
case, occuring at a value of the residual particle-particle interaction at
which the QRPA collapse. The RQRPA and the qp solutions do not include this
zero-energy eigenvalue in their spectra, probably due to spurious correlations.


title:
Polarization observables in dp backward elastic scattering at high and
  intermediate energies

abstract:
  The tensor analyzing power $T_{20}$ and the polarization transfer
coefficients $\kappa_0 (= 3/2 K_y^y)$ and $K_{xz}^y$ are investigated for dp
backward elastic scattering by the invariant-amplitude method. Discrepancies
between the conventional calculations and the experimental data on $T_{20}$ and
$\kappa_0$ at high and intermediate energies are mostly dissolved by including
imaginary parts in the amplitudes. The quantity $K_{xz}^y$ is shown to be
useful in criticizing nuclear force assumptions.


title: Probing nuclear expansion dynamics with $\pi^-/\pi^+$-spectra

abstract:
  We study the dynamics of charged pions in the nuclear medium via the ratio of
differential $\pi^-$- and $\pi^+$-spectra in a coupled-channel BUU (CBUU)
approach. The relative energy shift of the charged pions is found to correlate
with the pion freeze-out time in nucleus-nucleus collisions as well as with the
impact parameter of the heavy-ion reaction. Furthermore, the long-range Coulomb
force provides a 'clock' for the expansion of the hot nuclear system. Detailed
comparisons with experimental data for $Au + Au$ at 1 GeV/A and $Ni + Ni$ at
2.0 GeV/A are presented.


title: Recent Progress in Quantum Hadrodynamics

abstract:
  Quantum hadrodynamics (QHD) is a framework for describing the nuclear
many-body problem as a relativistic system of baryons and mesons. Motivation is
given for the utility of such an approach and for the importance of basing it
on a local, Lorentz-invariant lagrangian density. Calculations of nuclear
matter and finite nuclei in both renormalizable and nonrenormalizable,
effective QHD models are discussed. Connections are made between the effective
and renormalizable models, as well as between relativistic mean-field theory
and more sophisticated treatments. Recent work in QHD involving nuclear
structure, electroweak interactions in nuclei, relativistic transport theory,
nuclear matter under extreme conditions, and the evaluation of loop diagrams is
reviewed.


title:
Long-range correlations in finite nuclei: comparison of two
  self-consistent treatments

abstract:
  Long-range correlations, which are partially responsible for the observed
fragmentation and depletion of low-lying single-particle strength, are studied
in the Green's function formalism. The self-energy is expanded up to second
order in the residual interaction. We compare two methods of implementing
self-consistency in the solution of the Dyson equation beyond Hartree-Fock, for
the case of the 16O nucleus. It is found that the energy-bin method and the
BAGEL method lead to globally equivalent results. In both methods the final
single-particle strength functions are characterized by exponential tails at
energies far from the Fermi level.


title: Nucleon self-energy in the relativistic Brueckner approach

abstract:
  The formalism of the relativistic (or Dirac-) Brueckner approach in infinite
nuclear matter is described. As nucleon-nucleon interaction the one-boson
exchange potentials Bonn A,B,C and for comparison the Walecka model are used.
The T-matrix is determined from the Thompson equation and is projected onto
five covariant amplitudes. By the restriction to positive energy states an
ambiguity arises in the relativistic Brueckner approach which is discussed here
in terms of the pseudo-scalar and the pseudo-vector projection. The influence
of the coupling of the nucleon via the T-matrix as an effective two-nucleon
interaction to the nuclear medium is expressed by the self-energy. In
particular we investigate the scalar and vector components of the self-energy
for the different one-boson exchange potentials and discuss their density and
momentum dependence. We estimate the uncertainty of the self-energy due to the
pseudo-scalar and the pseudo-vector choice. Usually the momentum dependence of
the self-energy is thought to be weak, however, we find that this depends on
the one-boson exchange potentials. For the Bonn potentials, in contrast to the
$\sigma\omega$-potential, the momentum dependence is strikingly strong above as
well as below the Fermi surface. We compare with the results of other groups
and study the effects on the equation of state and the nucleon optical
potential.


title: Exact Q-Deformed Dyson Expansion for the Nuclear J=5/2 Shell

abstract:
  The quon algebra, which interpolates between the Bose and Fermi algebras and
depends on a free paramenter $q$, is used to generate a deformed Dyson boson
expansion of the quadrupole operator. Then we obtain a quadrupole-quadrupole
hamiltonian, for a single j-shell, in terms of this deformed bosonic operator.
The hamiltonian is diagonalized and its eigenvalues are compared with the ones
obtained from the fermionic quadrupole-quadrupole hamiltonian. The deformation
parameter helps in achieving the correct energy levels, what cannot be
encountered in practice with the usual non-deformed Dyson expansion.


title: J/\psi-dissociation by a color electric flux tube

abstract:
  We adress the question of how a $c-\bar{c}$-state (a $J/\psi $) can be
dissociated by the strong color electric fields when moving through a color
electric flux tube. The color electric flux tube and the dissociation of the
heavy quarkonia state are both described within the Friedberg-Lee color
dielectric model. We speculate on the importance of such an effect with respect
to the observed $J/\psi $-suppression in ultrarelativistic heavy ion
collisions.


title:
Phase transition and thermodynamics of a hot and dense system in a
  scaled NJL model

abstract:
  The chiral phase transition of a hot and dense system of quarks is studied
within a modified SU(3) NJL lagrangian that implements the QCD scale anomaly.
The u- and s-quark condensates can feel or not the same chiral restoration
depending on the considered region of the 3-dimension space T_c(\mu_uc,\mu_sc).
The temperature behaviour of the pressure and of the energy and entropy
densities of the u- and s-quark system is investigated. At high temperature,
the non-vanishing bare s-quark mass only modifies slightly the usual behaviour
associated with an ideal quark gas.


title: Low-Mass $e^+e^-$ Pairs from in-Medium $\rho$ Meson Propagation

abstract:
  Based on a realistic model for the rho meson in free space we investigate
it's medium modifications in a hot hadron gas generated by hadronic
rescattering processes, i.e. renormalization of intermediate two-pion states as
well as direct rho meson scattering off hadrons. Within the vector dominance
model the resulting in-medium rho spectral function is applied to calculate
$e^+e^-$ spectra as recently measured in heavy-ion collisions at CERN-SpS
energies in the CERES experiment.


title: Origin of subthreshold K^+ production in heavy ion collisions

abstract:
  We investigate the origin of subthreshold $K^+$ production in heavy ion
collisions at intermediate energies. In particular we study the influence of
the pion induced $K^+$ creation processes. We find that this channel shows a
strong dependence on the size of the system, i.e., the number of participating
nucleons as well as on the incident energy of the reaction. In an energy region
between 1--2 GeV/nucleon the pion induced processes essentially contribute to
the total yield and can even become dominant in reactions with a large number
of participating nucleons. Thus we are able to reproduce recent measurements of
the KaoS Collaboration for 1 GeV/nucleon Au on Au reactions adopting a
realistic momentum dependent nuclear mean field.


title: Subthreshold K+ Meson Production in Proton-Nucleus Reactions

abstract:
  The inclusive K+ mesons production in proton-nucleus collisions in the near
threshold and subthreshold energy regimes is analyzed with respect to the
one-step (pN->K+YN, Y=Lambda,Sigma) and the two-step (pN->NNpi, NN2pi;
piN->K+Y) incoherent production processes on the basis of an appropriate new
folding model, which takes properly into account the struck target nucleon
removal energy and momentum distribution (nucleon spectral function), extracted
from recent quasielastic electron scattering experiments and from many-body
calculations with realistic models of the NN interaction. Comparison of the
model calculations of the K+ double differential cross sections for the
reaction p+C at 1.2, 1.5 and 2.5 GeV beam energies with the existing
experimental data from the SATURNE experiment is given, illustrating both the
relative role of the primary and secondary production channels at considered
incident energies and those features of the cross sections which are sensitive
to the high momentum and high removal energy part of the nucleon spectral
function that is governed by nucleon-nucleon short-range and tensor
correlations. In--medium modifications of the available for pion and hyperon
production invariant energies squared due to the respective optical potentials
are needed to account for the experimental data on K+ production in the energy
region under consideration.


title:
Meson-nucleon vertex corrections to the vacuum polarization in the
  cutoff field theory and tensor coupling

abstract:
  At zero-density, meson-nucleon vertex corrections to vacuum polarization are
studied in the $\sigma-\omega$ model with the cutoff. It is shown that the
properties of the vertex corrections to vacuum polarization are somewhat
different from those described by the ordinary renormalization procedures when
the cutoff is small (< 5 GeV). The low-energy effective Lagrangian is
constructed in the framework of the renormalization group method. The weak
tensor and derivative couplings of meson-nucleon interactions may be needed in
the low-energy effective theory of mesons and nucleons.


title: Hadrons in Dense Matter

abstract:
  Physical reason behind the mass-shift of vector mesons ($\rho$, $\omega$,
$\phi$) in nuclear matter is discussed in the Walecka model and in QCD sum
rules. Using analytic formulas for the mass-shift valid at low densities, it is
shown that the energy dependent part of the sels-energy (wave function
renomalization) in medium is a main source for the negative mass-shift, while
the energy independent part (the plasma frequency) has relatively a small
effect. Future experiments in GSI ($\pi^- + A \to X + \omega$ ) and KEK-PS ($p
+ A \to X + \phi$ ) to detect the twin peak structure of vector mesons in
$e^+e^-$ spectrum are reviewed. Also, it is proposed a new possible experiment
using a $S (strangeness) = 1$ vector meson $K^{*}(892)$ with its radiative
decay $K^{*+}(892) \to K^+ + \gamma$.


title:
Systematic study of Coulomb distortion effects in exclusive (e,e'p)
  reactions

abstract:
  A technique to deal with Coulomb electron distortions in the analysis of
(e,e'p) reactions is presented. Thereby, no approximations are made. The
suggested technique relies on a partial-wave expansion of the electron wave
functions and a multipole decomposition of the electron and nuclear current in
momentum space. In that way, we succeed in keeping the computational times
within reasonable limits. This theoretical framework is used to calculate the
quasielastic (e,e'p) reduced cross sections for proton knockout from the
valence shells in $^{16}$O, $^{40}$Ca, $^{90}$Zr and $^{208}$Pb. The
final-state interaction of the ejected proton with the residual nucleus is
treated within an optical potential model. The role of electron distortion on
the extracted spectroscopic factors is discussed.


title:
Equation of State of Hadronic matter and Electromagnetic Radiation from
  Relativisitic Heavy Ion Collisions

abstract:
  We study the radiation of thermal photons and dileptons likely to be produced
in relativistic heavy ion collisions. We find that the thermal photon
multiplicity scales with the charged pion multiplicity as $dN_{ch}/dy)^\alpha$
with $\alpha\sim 1.2$ for a transversely expanding system, contrary to the
general belief of a quadratic dependence. The scaling is shown to be valid,
both for real and virtual photons. The coefficient of proportionality at a
given energy may help us identify the appropriate equation of state of hot
hadronic matter produced in such collisions.


title: Bose-Einstein Correlations of Pion Wavepackets

abstract:
  A wavepacket model for a system of free pions, which takes into account the
full permutation symmetry of the wavefunction and which is suitable for any
phase space parametrization is developed. The properties of the resulting mixed
ensembles and the two-particle correlation function are discussed. A physical
interpretation of the chaoticity lambda as localizat of the pions in the source
is presented.
  Two techniques to generate test-particles, which satisfy the probability
densities of the wavepacket state, are studied:
  1. A Monte Carlo procedure in momentum space based on the standard Metropolis
technique.
  2. A molecular dynamic procedure using Bohm's quantum theory of motion.
  In order to reduce the numerical complexity, the separation of the
wavefunction into momentum space clusters is discussed. In this context th
influence of an unauthorized factorization of the state, i. e. the omissio of
interference terms, is investigated. It is shown that the correlation radius
remains almost uneffected, but the chaoticity parameter decreases
substantially. A similar effect is observed in systems with high multiplic
where the omission of higher order corrections in the analysis of two-part
correlations causes a reduction of the chaoticity and the radius.
  The approximative treatment of the Coulomb interaction between pions and
source is investigated. The results suggest that Coulomb effects on the co
radii are not symmetric for pion pairs of different charges. For negative the
radius, integrated over the whole momentum spectrum, increases substan while
for positive pions the radius remains almost unchanged.


title:
Combined analysis of the reactions $pp \to pp$, $\pi d\to \pi d$, and
  $\pi d\to pp$

abstract:
  Results are presented for a combined analysis of the reactions $pp\to pp$,
$\pi d\to \pi d$ and $\pi d\to pp$ over the $\sqrt{s}$ interval from pion
threshold to approximately 2.4 GeV. These results for $\pi d\to pp$ and $\pi d$
elastic scattering are superior to our previous analyses of these reactions. In
particular, the overall phase in $\pi d\to pp$ has now been determined.
Comparisons are made with previous (separate and combined) analyses of this
two-nucleon system.


title:
Periodic-Orbit Bifurcation and Shell Structure in Reflection-Asymmetric
  Deformed Cavity

abstract:
  Shell structure of the single-particle spectrum for reflection-asymmetric
deformed cavity is investigated. Remarkable shell structure emerges for certain
combinations of quadrupole and octupole deformations. Semiclassical
periodic-orbit analysis indicates that bifurcation of equatorial orbits plays
an important role in the formation of this new shell structure.


title: Structure of the Vacuum in Nuclear Matter - A Nonperturbative Approach

abstract:
  We compute the vacuum polarisation correction to the binding energy of
nuclear matter in the Walecka model using a nonperturbative approach. We first
study such a contribution as arising from a ground state structure with
baryon-antibaryon condensates. This yields the same results as obtained through
the relativistic Hartree approximation of summing tadpole diagrams for the
baryon propagator. Such a vacuum is then generalized to include quantum effects
from meson fields through scalar-meson condensates. The method is applied to
study properties of nuclear matter and leads to a softer equation of state
giving a lower value of the incompressibility than would be reached without
quantum effects. The density dependent effective sigma mass is also calculated
including such vacuum polarisation effects.


title:
Old and New Facets of y-Scaling: the Universal Features of Nuclear
  Structure Functions and Nucleon Momentum Distributions

abstract:
  Some systematic general features of y-scaling structure functions, which are
essentially independent of detailed dynamics, are pointed out. Their physical
interpretation in terms of general characteristics, such as a mean field
description and nucleon-nucleon correlations, is given and their relationship
to the momentum distributions illustrated. A new scaling variable is proposed
which allows a direct expression of the scaling function in term of an integral
over the momemtum distributions thereby avoiding explicit consideration of
binding corrections.


title:
Spectral Distribution Studies of fp shell nuclei with modified
  Kuo--Brown Interaction

abstract:
  The structure of nuclei in the lower half of fp shell is investigated by the
spectral distribution method using the modified Kuo-Brown interaction. This
interaction recently showed success in reproducing observed properties through
detailed shell model studies. Spectral distribution studies avoid explicit
diagonalization and hold promise for applications to astrophysics.


title:
The Linear Correlation Coefficient vs. the Cross Term in Bose-Einstein
  Correlations

abstract:
  We investigate the nature of the new cross term for Gaussian
parameterizations of Bose-Einstein correlations of identical particles emitted
from purely chaotic hadron sources formed by relativistic heavy ion collisions.
We find that this additional parameter in the so-called Bertsch
parameterization can be expressed in terms of a linear ``out-longitudinal''
correlation coefficient for emission of bosons and two already known ``radius''
parameters, $R_l$ and $R_o$. The linear correlation coefficient is of
kinematical nature and can be used to determine the widths of longitudinal
momentum distributions.


title:
Predictions for the 4 GeV TJNAF inclusive electron scattering experiment
  and for FSI effects in EMC ratios

abstract:
  We express nuclear structure functions $F_i^A$ as generalized convolutions of
the structure function of a nucleon and of a nucleus, composed of
point-nucleons. In computations of the latter we include Final State
Interactions and results for $F_2^A$ are compared with a few directly measured
data on C and Fe. The above $F_i^A$ are primarily used for predictions of the
TJNAF 89-008 inclusive scattering experiment of 4 GeV electrons on various
targets. Those cover a broad angular, and correspondingly wide $x,Q^2$ range,
where the nucleon-inelastic part dominates large sections of the covered
kinematics. The same model has been applied to the study of hitherto neglected
Final State Interaction effects in the nuclear component in EMC ratios in the
region $0.85\lesssim x\lesssim 0.25$.


title:
Constraints on Parity-Even Time Reversal Violation in the
  Nucleon-Nucleon System and Its Connection to Charge Symmetry Breaking

abstract:
  Parity-even time reversal violation (TRV) in the nucleon-nucleon interaction
is reconsidered. The TRV $\rho$-exchange interaction on which recent analyses
of measurements are based is necessarily also charge-symmetry breaking (CSB).
Limits on its strength $\bar{g}_\rho$ relative to regular $\rho$-exchange are
extracted from recent CSB experiments in neutron-proton scattering. The result
$\bar{g}_\rho\le 6.7\times 10^{-3}$ (95% CL) is considerably lower than limits
inferred from direct TRV tests in nuclear processes. Properties of
$a_1$-exchange and limit imposed by the neutron EDM are briefly discussed.


title: Normalization of the covariant three-body bound state vertex function

abstract:
  The normalization condition for the relativistic three nucleon Bethe-Salpeter
and Gross bound state vertex functions is derived, for the first time, directly
from the three body wave equations. It is also shown that the relativistic
normalization condition for the two body Gross bound state vertex function is
identical to the requirement that the bound state charge be conserved, proving
that charge is automatically conserved by this equation.


title:
Polarization Observables in Phi Meson Photoproduction and the
  Strangeness Content of the Proton

abstract:
  The contributions of direct knockout processes, in addition to the
diffractive production and one-pion-exchange processes associated with the
phi-rho-pi and phi-gamma-pi couplings, to the polarization observables of the
phi photoproduction from proton are calculated. We make use of Pomeron-photon
analogy and a relativistic harmonic oscillator quark model. We find that some
of the double polarization observables are very sensitive to a possible (s
s-bar) admixture in the proton. It arises from the difference in the spin
structures of the three different amplitudes. This suggests that such
measurements could be very useful to probe the strangeness content in the
proton.


title: Properties of Hadrons in the Nuclear Medium

abstract:
  This review is devoted to the discussion of hadron properties in the nuclear
medium and its relation to the partial restoration of chiral symmetry. Special
attention is given to disentangle in-medium effects due to conventional
many-body interactions from those due to the change of the chiral condensate.
In particular, we shall discuss medium effects on the Goldstone bosons (pion,
kaon and eta), the vector mesons (rho, omega, phi), and the nucleon. Also, for
each proposed in-medium effect the experimental consequence and results will be
reviewed.


title:
Comparison of Fermion SU(3) and Boson SU(3) models for scissors mode
  excitations

abstract:
  For a $Q \cdot Q$ interaction the energy weighted sum rule for isovector
orbital magnetic dipole transitions is proportional to the difference $\sum
B(E2, isoscalar) - \sum B(E2, isovector)$, not just to $\sum B(E2, physical)$.
This fact is important in ensuring that one gets the correct limit as one goes
to nuclei, some of which are far from stability, for which one shell (neutron
or proton) is closed. In $0p$ shell calculations for the even-even Be isotopes
it is shown that the Fermion SU(3) model and Boson SU(3) model give different
results for the energy weighted scissors mode strengths.


title: First-forbidden beta decay of 17N and 17Ne

abstract:
  It is shown that differences, due to charge-dependent effects, in the 17N and
17Ne ground-state wave functions account for the fact that the experimentally
measured branch for the beta+ decay of 17Ne to the first excited state of 17F
is roughly a factor of two larger than expected on the basis of nuclear matrix
elements which reproduce the corresponding beta- branch in the decay of 17N.


title: Nuclear Polarizabilities and Logarithmic Sum Rules

abstract:
  The electric polarizability and logarithmic mean-excitation energy are
calculated for the deuteron using techniques introduced in atomic physics.
These results are then used to improve limits on the atomic-deuterium frequency
shift due to nuclear polarization in the unretarded dipole limit, as well as
confirming previous results.


title: Emission of Gamma Rays by X-ray Electron-Nuclear Double Transitions

abstract:
  This is a paper about induced gamma emission. The X-ray electron-nuclear
double transitions (XENDT) are processes in which a transition effected by an
inner atomic electron takes place simultaneously with a nuclear electromagnetic
transition. We give expressions for the cross sections of electric and magnetic
XENDTs of various multipole orders. We calculate the rate of deexcitation of
isomeric nuclei induced by XENDTs for the case when the holes in the atomic
shells are produced by incident ionizing electrons and find that the induced
nuclear deexcitation rate becomes comparable to the natural decay rate for
ionizing fluxes of the order of $10^{14}$ W cm$^{-2}$. We show that for E1 and
M1 nuclear processes for which there is a matching between the electron and the
nuclear transition energies, the XENDTs can be used to produce pulses of
M\"{o}ssbauer radiation, with yields of the order of $10^4$ Bq mA$^{-1}$.


title: General Relativistic Mean Field Theory for Rotating Nuclei

abstract:
  We formulate a general relativistic mean field theory for rotating nuclei
starting from the special relativistic $\sigma - \omega$ model Lagrangian. The
tetrad formalism is adopted to generalize the model to the accelerated frame.


title:
Emission of gamma rays shifted from resonant absorption by
  electron-nuclear double transitions in ^{151}Eu^{2+}:CaF_2

abstract:
  We show that the emission of a gamma-ray photon by a nucleus can be
influenced by a microwave magnetic field acting on the atomic electrons. We
study theoretically these electron-nuclear double transitions (ENDTs) for
^{151}Eu nuclei in a CaF_2 lattice at low temperature, in the presence of a
static magnetic field and of a microwave magnetic field. The ENDTs acquire a
significant intensity for certain resonance frequencies. The ENDTs are of
interest for the identification of the position of the lines in complex
M\"{o}ssbauer spectra.


title: Nucleon flow and dilepton production in heavy-ion collisions

abstract:
  Nucleon flow in Au+Au collisions at 1 GeV/nucleon region and dilepton spectra
in S+Au collisions at SPS energies are analysed in the relativistic transport
model. They are shown to be sensitive to the nucleon vector and scalar
potentials, respectively, and are thus useful probes of these potentials in
dense matter. A recently developed effective Lagrangian with self-interactions
of vector as well as scalar fields is found to describe both data reasonably
well.


title: Adiabatic quantum tunneling in heavy-ion sub-barrier fusion

abstract:
  High precision measurements of the fusion excitation functions for the
reactions ^{40}Ca + ^{194}Pt, ^{192}Os clearly demonstrate that projectile
excitation significantly modifies the potential barrier distribution. In sharp
contrast, fusion of ^{16}O + ^{144}Sm appears to show no influence of the
projectile excitation on the shape of the barrier distribution. These
apparently conflicting conclusions are reconciled in this work, using realistic
coupled--channels calculations, which show that high energy states produce an
adiabatic potential renormalisation. This result indicates that adiabatic
effects restrict, in a natural way, the states which influence the shape of a
fusion barrier distribution. The analysis of barrier distributions thus offers
a criterion for the relevance of the `counter term' prescription in the
Caldeira-Leggett approach.


title: Fluctuations of Spatial Patterns as a Measure of Classical Chaos

abstract:
  In problems where the temporal evolution of a nonlinear system cannot be
followed, a method for studying the fluctuations of spatial patterns has been
developed. That method is applied to well-known problems in deterministic chaos
(the logistic map and the Lorenz model) to check its effectiveness in
characterizing the dynamical behaviors. It is found that the indices $\mu _q$
are as useful as the Lyapunov exponents in providing a quantitative measure of
chaos.


title:
The longitudinal and transverse responses in the inclusive electron
  scattering: a functional approach

abstract:
  The splitting between the charge-longitudinal and spin-transverse responses
is explained in a model whose inputs are the effective interactions in the
particle-hole channels in the frame of the first order boson loop expansion. It
is shown that the interplay between $\omega$-meson exchange and box diagrams
(two-meson exchange with simultaneous excitation of one or two nucleons to
$\Delta$'s) mainly rules the longitudinal response, while in the transverse one
the direct $\Delta$ excitations almost cancel the one-loop correction and the
response is mainly governed by the $\rho$-meson rescattering inside the
nucleus. It is also shown that a small variation in the nuclear densities may
explain the observed discrepancies between different nuclei.


title: Fixed-Velocity Chiral Sum Rules for Nuclear Matter

abstract:
  Infinite sets of sum rules involving the excitations of infinite nuclear
matter are derived using only completeness, the current algebra implicit in
QCD, and relativistic covariance. The sum rules can be used for
isospin-asymmetric nuclear matter, including neutron matter. They relate the
chiral condensate and the isospin density to weighted sums over states with
fixed velocity relative to the nuclear matter ground state.


title:
Treatment of baryonic resonances in the RQMD approach including
  scalar-vector mean fields

abstract:
  In the relativistic Quantum Molecular Dynamics (RQMD) approach baryons are
described within the framework of covariant hamilton constraint dynamics. The
inclusion of a relativistic mean field results in a quasiparticle picture for
the baryons. This requires to distinguish between canonical and kinetic
variables of the particles. As resonances we include the $\Delta$(1232) and the
$N^*$(1440) resonance. The resonance masses are distributed according
Breit-Wigner functions. However, the scalar self energy leads to a shift in the
masses and introduces an additional medium dependence. Consequences of this
description on resonance and pion dynamics are discussed.


title:
A self-consistent treatment of the dynamics of stable and unstable
  collective modes

abstract:
  We address the dynamics of damped collective modes in terms of first and
second moments. The modes are introduced in a self-consistent fashion with the
help of a suitable application of linear response theory. Quantum effects in
the fluctuations are governed by diffusion coefficients D_{\mu\nu}. The latter
are obtained through a fluctuation dissipation theorem generalized to allow for
a treatment of unstable modes. Numerical evaluations of the D_{\mu\nu} are
presented. We discuss briefly how this picture may be used to describe global
motion within a locally harmonic approximation.


title: Meson Exchange Currents in Kaon Scattering on the Lightest Nuclei

abstract:
  The K^+ scattering on the lightest nuclei, d, 3He and 4He is studied in the
framework of multiple scattering theory. Effects from MEC tied to the
K^+N-->KNpi reaction are evaluated. We found that at momentum transfers Q^2<0.5
(GeV/c)^2 contributions from MEC are much smaller than kaon rescattering
corrections. This makes the conventional multiple scattering picture a reliable
tool to study these reactions in this kinematical domain and to extract the
K^+n scattering amplitude from the K^+d data. At larger transferred momentum
MEC can become more relevant.


title:
Treatment of the $\Delta$ current in electromagnetic two-nucleon
  knockout reactions

abstract:
  The contribution of the $\Delta$(1232) isobar to the electromagnetic current
of the two-nucleon system and its role in ($\gamma$,NN) processes is
investigated. The difference between the genuine $\Delta$-excitation current
and that part of the current connected to the deexcitation of a preformed
$\Delta$ in the target nucleus is stressed. The latter cannot lead to a
resonant behaviour of matrix elements for energies in the $\Delta$ region. The
reaction $^{16}O(\gamma,pp)^{14}C$, where the $\Delta$ contribution is dominant
at intermediate energies, is considered. The large variations found in the
cross sections for different treatments stress the need for a proper treatment
of the $\Delta$ current for a clear understanding of the reaction mechanism of
two-nucleon emission processes.


title: Flux-Bubble Models and Mesonic Molecules

abstract:
  It has been shown that the string-flip potential model reproduces most of the
bulk properties of nuclear matter, with the exception of nuclear binding.
Furthermore, it was postulated that this model with the inclusion of the
colour-hyperfine interaction should produce binding. In some recent work a
modified version of the string-flip potential model was developed, called the
flux-bubble model, which would allow for the addition of perturbative QCD
interactions. In attempts to construct a simple $q\bar q$ nucleon system using
the flux-bubble model (which only included colour-Coulomb interactions)
difficulties arise with trying to construct a many-body variational wave
function that would take into account the locality of the flux-bubble
interactions. In this paper we look at a toy system, a mesonic molecule, in
order to understand these difficulties. {\it En route}, a new variational wave
function is proposed that may have a sufficient impact on the old string-flip
potential model results that the inclusion of perturbative effects may not be
needed.


title:
Baryon Resonance Extraction from Pi Nucleon Data using a Multichannel
  Unitary Model

abstract:
  We present organization and solutions for a new analysis of all $\pi N$
elastic and the major inelastic channels to extract detailed characteristics of
the contributing baryon resonances. This work is based on the work of R.
Cutkosky and collaborators at CMU about 20 years ago. The model features
analyticity at the amplitude level and unitarity. Results are similar to
previous analyses for strongly excited states, but can vary considerably from
previous analyses when the states are weak, the data is poor, or there is a
strong model dependence. We emphasize the S_{11}(1535) resonance which has
particularly strong model dependence.


title:
Solution of few-body problems with the stochastic variational method: I.
  Central forces

abstract:
  This paper presents a fortran program to solve diverse few-body problems with
the stochastic variational method. Depending on the available computational
resources the program is applicable for $N=2-3-4-5-6-...$-body systems with
$L=0$ total orbital momentum. The solution with the stochastic variational
method is ``automatic'' and universal. One defines the system (number of
particles, masses, symmetry, interaction, etc. ) and the program finds the
ground state energy and wave function. The examples include nuclear (alpha
particle: four-body, $^6$He: six-body), atomic (td$\mu^-$ and $e^+e^-e^+e^-$)
and subnuclear (the nucleon and the delta in a nonrelativistic quark model)
systems. The solutions are accurate for excited states as well, and even the
Efimov-states can be studied. The program is available from the author
(e-mail:varga@rikaxp.riken.go.jp).


title:
Progress in the Development of Global Medium-Energy Nucleon-Nucleus
  Optical Model Potentials

abstract:
  Two existing global medium-energy nucleon-nucleus phenomenological optical
model potentials are described and compared with experiment and with each
other. The first of these employs a Dirac approach (second-order reduction)
that is global in projectile energy and projectile isospin and applies to the
target nucleus 208-Pb. Here the standard S-V (isoscalar-scalar,
isoscalar-vector) model has been extended to include the corresponding
isovector components by introduction of a relativistic Lane model. The second
of these employs a relativistic equivalent to the Schroedinger equation and is
global in projectile energy, projectile isospin, and target (Z,A). Here,
particular attention is given to predictions for the integrated scattering
observables - neutron total cross sections and proton total reaction cross
sections - and their sensitivity to the absorptive parts of the potential.
Finally, current work is described and the influence of the nuclear bound state
problem (treated in relativistic mean field theory) on the Dirac scattering
problem is mentioned.


title:
A Light Front Treatment of the Nucleus-Implications for Deep Inelastic
  Scattering

abstract:
  A light front treatment of the nuclear wave function is developed and
applied, using the mean field approximation, to infinite nuclear matter. The
nuclear mesons are shown to carry about a third of the nuclear plus momentum,
p+; but their momentum distribution has support only at p+ =0, and the mesons
do not contribute to nuclear deep inelastic scattering. This zero mode effect
occurs because the meson fields are independent of space-time position.


title:
Three-Body Resonances in Framework of the Faddeev Configuration Space
  Approach

abstract:
  Algorithm, based on explicit representations for analytic continuation of the
T-matrix Faddeev components on unphysical sheets, is worked out for
calculations of resonances in the three-body quantum problem. According to the
representations, poles of the T--matrix, scattering matrix and resolvent on
unphysical sheets, interpreted as resonances, coincide with those complex
energy values where appropriate truncations of the scattering matrix have zero
as eigenvalue. Scattering amplitudes on the physical sheet, necessary to
construct scattering matrix, are calculated on the basis of the Faddeev
differential equations. Effectiveness of the algorithm developed is
demonstrated for example of searching for resonances in the system $nnp$ and in
a model three-boson system.


title:
Fermi and Gamow-Teller Strength in Charge Exchange with Radioactive
  Beams

abstract:
  At forward angles, and bombarding energies E > 200 MeV, the (p,n) and (n,p)
reactions are thought to be directly proportional to the Gamow-Teller
transition strengths in the nuclei. Assuming that this relationship also holds
for charge exchange induced by high-energy heavy ions, it would be very useful
in studies with radioactive beams. Contrary to this expectation, we show that
the determination of Gamow-Teller and Fermi matrix elements from heavy-ion
charge-exchange at forward angles is very inaccurate.


title: Pion photoproduction in the delta resonance region

abstract:
  We have updated our multipole analyses to incorporate new data from the
low-energy and delta resonance regions. We note a slight decrease in our
estimate of the delta photo-decay amplitudes. This agrees with results found in
Compton scattering. Our values are also in good agreement with a previous RPI
determination. We have reexamined our determinations of the E2/M1 ratio at the
resonance energy and at the pole. We find an E2/M1 ratio (at the pole) which is
in good agreement with recent the Mainz value.


title: Delays, Unstable Particles, and Transport Theory

abstract:
  Delays associated with elementary interaction processes are investigated. The
case of broad resonances is discussed in the context of reaction simulations.


title: $\Sigma$ Like Term in Pion Electroproduction Near Threshold

abstract:
  Sum of the time component of $\Sigma$ term and the induced pseudo scalar term
in axial current is shown to be the t-channel pion pole in Born terms for pion
electroproduction near threshold. We also show that this $\Sigma$ term
represents the charged pseudo scalar quark density matrix elements in nucleon
and manifests itself in the $L_0^+$ amplitude on this reaction.


title:
Equilibrium shapes and high-spin properties of the neutron-rich A~100
  nuclei

abstract:
  Shapes and high-spin properties of nuclei from the neutron-rich (N>56)
zirconium region are calculated using the Nilsson-Strutinsky method with the
cranked Woods-Saxon average potential and monopole pairing residual
interaction. The shape coexistence effects and the competition between
rotationally-aligned 1h11/2 neutron and 1g9/2 proton bands is discussed.
Predictions are made for the low-lying superdeformed bands in this mass region,
characterized by the intruder states originating from the N=5 and 6 oscillator
shells.


title:
Application of the Kerman-Klein method to the solution of a spherical
  shell model for a deformed rare-earth nucleus

abstract:
  Core-particle coupling models are made viable by assuming that core
properties such as matrix elements of multipole and pairing operators and
excitation spectra are known independently. From the completeness relation, it
is seen, however, that these quantities are themselves algebraic functions of
the calculated core-particle amplitudes. For the deformed rare-earth nucleus
158Gd, we find that these sum rules are well-satisfied for the ground state
band, implying that we have found a self-consistent solution of the non-linear
Kerman-Klein equations.


title: Mott mechanism and anomalous charmonium suppression

abstract:
  We investigate a scenario where conditions for Mott dissociation of
charmonium are fulfilled locally in ultrarelativistic heavy ion collisions at
the short time scales before hadronization and study possible consequences to
be drawn from observation of ``anomalous'' thresholds in the J/\psi suppression
pattern. We suggest that for a compilation of experiments with different
kinematics, variables presently in use to display the observed suppression
pattern should be rescaled by the $\gamma$ factor of the $c\bar c$ state
relative to the participant center of mass. This systematics can be tested by
inverse kinematics experiments as, e.g., Pb-S collisions and by sampling data
sets in p_T and y of the dimuon pairs.


title: Vacuum polarization Contribution to the Astrophysical S-Factor

abstract:
  We study the effect of vacuum polarization in nuclear reactions of
astrophysical interest. This effect has the opposite sign compared to the
screening by the atomic electrons. It is shown that vacuum polarization further
increases the longstanding differences between the experimental data of
astrophysical nuclear reactions at very low energies and the theoretical
calculations which aim to include electron screening, albeit by a small amount.


title: Hadrons in Medium - Observables

abstract:
  The observable consequences of a lowering of the restmasses of vector mesons
on dilepton spectra in the SIS energy regime (HADES) and on photoabsorption
cross sections on nuclei are studied in a transporttheoretical framework. We
also investigate the consequences of a mass-shift of kaons in dense matter and
compare with recent SIS data. The need for a detailed understanding of the
elementary processes is underlined.


title: Neutron-proton pairing in the BCS approach

abstract:
  We investigate the BCS treatment of neutron-proton pairing involving
time-reversed orbits. We conclude that an isospin-symmetric hamiltonian,
treated with the help of the generalized Bogolyubov transformation, fails to
describe the ground state pairing properties correctly. In order for the np
isovector pairs to coexist with the like-particle pairs, one has to break the
isospin symmetry of the hamiltonian by artificially increasing the strength of
np pairing interaction above its isospin symmetric value. We conjecture that
the np isovector pairing represents part (or most) of the congruence energy
(Wigner term) in nuclear masses.


title:
Specialists' Meeting on the Nucleon-Nucleus Optical Model up to 200 MeV:
  Conclusions and Recommendations

abstract:
  Contains the conclusions and recommendations from this meeting regarding
future experimental and theoretical work on the medium-energy nucleon-nucleus
optical model.


title: Electroinduced two-nucleon knockout and correlations in nuclei

abstract:
  We present a model to calculate cross sections for electroinduced two-nucleon
emission from finite nuclei. Short-range correlations in the wave functions and
meson-exchange contributions to the photoabsorption process are implemented.
Effects of the short-range correlations are studied with the aid of a
perturbation expansion method with various choices of the Jastrow correlation
function. The model is used to investigate the relative importance of the
different reaction mechanisms contributing to the A(e,e$'$pn) and A(e,e$'$pp)
process. Representative examples for the target nuclei $^{12}$C and $^{16}$O
and for kinematical conditions accessible with contemporary high-duty cycle
electron accelerators are presented. A procedure is outlined to calculate the
two-nucleon knockout contribution to the semi-exclusive (e,e$'$p) cross
section. Using this technique we investigate in how far semi-exclusive
(e,e$'$p) reactions can be used to detect high-momentum components in the
nuclear spectral function.


title: Deuteron Electroweak Disintegration

abstract:
  We study the deuteron electrodisintegration with inclusion of the neutral
currents focusing on the helicity asymmetry of the exclusive cross section in
coplanar geometry. We stress that a measurement of this asymmetry in the quasi
elastic region is of interest for an experimental determination of the weak
form factors of the nucleon, allowing one to obtain the parity violating
electron neutron asymmetry. Numerically, we consider the reaction at low
momentum transfer and discuss the sensitivity of the helicity asymmetry to the
strangeness radius and magnetic moment. The problems coming from the finite
angular acceptance of the spectrometers are also considered.


title: The Role of Gluon Depletion in J/psi Suppression

abstract:
  The depletion of gluons as the parton flux traverses a nucleus in a heavy-ion
collision can influence the production rate of heavy-quark states. Thus the
suppression of $J/\psi$ can be due to gluon depletion in the initial state in
addition to nuclear and hadronic absorption in the final state. A formalism is
developed to describe the depletion effect. It is shown that, without
constraints from other experimental facts beside the $J/\psi$ suppression data
in $pA$ and $AB$ collisions, it is not possible to determine the relative
importance of depletion vs absorption. Possible relevance to the enhanced
suppression seen in the $Pb - Pb$ data is mentioned but not studied.


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

abstract:
  We suggest that the error quoted in the Mainz determination of the E2/M1
ratio (at the resonance energy) should be enlarged. A term dropped in
expressions used by this group could be significant.


title: Particle Production from SIS to SPS Energies

abstract:
  The production and propagation of mesons ($\pi, \eta, \rho, \omega, \Phi, K,
\bar{K}, J/\Psi$) in proton-nucleus and nucleus-nucleus collisions from 1 - 200
GeV/u is studied within the covariant transport approach HSD, which explicitly
allows to investigate selfenergy effects of the hadrons at finite baryon
density. Whereas the experimental pion and $K^+$ spectra can be described
without introducing any selfenergies for the mesons, the $K^-$ yield in Ni + Ni
collisions is underestimated by a factor of 5 - 7 at 1.66 and 1.85 GeV/u.
However, introducing density dependent antikaon masses in line with effective
chiral Lagrangians a satisfactory agreement with the data is achieved. A
dropping of the $\rho$-meson mass with baryon density, as suggested by QCD
sumrule studies, is proposed to explain the dilepton spectra for S + Au and Pb
+ Au at SPS energies, which indicates independently that a partial restoration
of chiral symmetry might be found already in the present experiments.


title: The Origin of the Wigner Energy

abstract:
  Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a
sharp slope discontinuity at N=Z. This cusp (Wigner energy), reflecting an
additional binding in nuclei with neutrons and protons occupying the same shell
model orbitals, is usually attributed to neutron-proton pairing correlations. A
method is developed to extract the Wigner term from experimental data. Both
empirical arguments and shell-model calculations suggest that the Wigner term
can be traced back to the isospin T=0 part of nuclear interaction. Our
calculations reveal the rather complex mechanism responsible for the nuclear
binding around the N=Z line. In particular, we find that the Wigner term cannot
be solely explained in terms of correlations between the neutron-proton J=1,
T=0 (deuteron-like) pairs.


title: Effects of Relativistic Dynamics in $pp \to pp \pi^0$ near Threshold

abstract:
  The cross-section for threshold $\pi^0$ production in proton-proton
collisions is evaluated in the framework of the covariant spectator
description. The negative energy intermediate states are included
non-perturbatively and seen to yield a considerably smaller contribution, when
compared to perturbative treatments. A family of OBE-models with different
off-shell scalar coupling is considered.


title: Broken SU(3) symmetry in deformed even-even nuclei

abstract:
  A collective vector-boson model with broken SU(3) symmetry, in which the
ground state band and the lowest $\gamma$ band belong to the same irreducible
representation but are non-degenerate, is applied to several deformed even-even
nuclei. The model description of ground and $\gamma$ bands together with the
corresponding B(E2) transition probabilities is investigated within a broad
range of SU(3) irreducible representations $(\lambda,\mu)$. The calculations
show that the $(\lambda,\mu)$ characteristics of rotational nuclei depend to a
great extent on the magnitude of the SU(3) splitting between the ground and
$\gamma$ bands. It is found that for weakly split spectra, the ground--$\gamma$
band coupling scheme is realized relevantly within narrow regions of
``favored'' $(\lambda,\mu)$ multiplets, while in the cases of strong splitting
a description in which the ground band is situated alone in an irreducible
representation is favored. The obtained results are analyzed in terms of the
bandmixing interactions. The possibility for a transition between the different
collective SU(3) schemes is discussed.


title:
Coherent $\eta$-photoproduction on $^4$He and $^{12}$C in the
  near-threshold region

abstract:
  Coherent $\eta$ meson photoproduction on $^4$He and $^{12}$C is considered in
the near-threshold region. The elementary $\eta$ photoproduction operator
includes contributions from the $S_{11}(1535)$ and $D_{13}(1520)$ resonances as
well as $t$-channel vector meson exchange and the nucleon pole terms. Due to
the suppression of the dominant $S_{11}(1535)$ resonance for spin and isospin
saturated nuclei, the reaction is mainly governed by $\omega$ exchange.
Furthermore, the influence of Fermi motion and of different prescriptions for
the choice of the invariant reaction energy $W_{\gamma N}$ in the elementary
amplitude is studied.


title:
Towards a fully self-consistent spectral function of the nucleon in
  nuclear matter

abstract:
  We present a calculation of nuclear matter which goes beyond the usual
quasi-particle approximation in that it includes part of the off-shell
dependence of the self-energy in the self-consistent solution of the
single-particle spectrum. The spectral function is separated in contributions
for energies above and below the chemical potential. For holes we approximate
the spectral function for energies below the chemical potential by a
$\delta$-function at the quasi-particle peak and retain the standard form for
energies above the chemical potential. For particles a similar procedure is
followed. The approximated spectral function is consistently used at all levels
of the calculation. Results for a model calculation are presented, the main
conclusion is that although several observables are affected by the inclusion
of the continuum contributions the physical consistency of the model does not
improve with the improved self-consistency of the solution method. This in
contrast to expectations based on the crucial role of self-consistency in the
proofs of conservation laws.


title: Kaon Photoproduction on the Nucleon : Status and Future Prospects

abstract:
  Kaon photo- and electroproduction off the nucleon is investigated in the
framework of an isobaric model up to energies of about 1 GeV above threshold
for all six isospin channels. The hadronic coupling constants in the model are
determined by fitting to the available experimental data. We give a brief
status report on the state of these models and discuss problems to be attacked
in the future. We include hadronic form factors and show that they are
essential for a proper description of the dynamics even though their inclusion
has to be done carefully in order to preserve gauge invariance. We also
investigate the effects of the K0 electromagnetic form factors for two quark
models on the longitudinal and transverse differential cross sections. It is
found that only the reaction n(e,e'K0)\Lambda is sufficiently sensitive to
extract the K0 form factor.


title: Nuclear and Neutron Matter Calculations with Different Model Spaces

abstract:
  In this work we investigate the so-called model-space Brueckner-Hartree-Fock
(MBHF) approach for nuclear matter as well as for neutron matter and the
extension of this which includes the particle-particle and hole-hole (PPHH)
diagrams. A central ingredient in the model-space approach for nuclear matter
is the boundary momentum $k_M$ beyond which the single-particle potential
energy is set equal to zero. This is also the boundary of the model space
within which the PPHH diagrams are calculated. It has been rather uncertain
which value should be used for $k_M$. We have carried out model-space nuclear
matter and neutron matter calculations with and without PPHH diagrams for
various choices of $k_M$ and using several modern nucleon-nucleon potentials.
Our results exhibit a saturation region where the nuclear and neutron matter
matter energies are quite stable as $k_M$ varies. The location of this region
may serve to determine an "optimum" choice for $k_M$. However, we find that the
strength of the tensor force has a significant influence on binding energy
variation with $k_M$. The implications for nuclear and neutron matter
calculations are discussed.


title:
APEX: Positive evidence for sharp 800 keV pairs from heavy ion
  collisions near the Coulomb barrier

abstract:
  The best fit to the published APEX U+Th data describes a sharp line of 123
pairs of width 23 keV at 793$\pm$7 keV; also, the data impose a positive
99.0%CL lower bound of 23 sharp pairs. It is therefore untenable to argue from
the APEX data against the existence of sharp pairs. Data-only ratios APEX/EPOS
pair counts show empirically that the two experiments' pair data are mutually
consistent and of comparable statistical potency: conflicts, if any, can be
resolved only by other independent evidence. A perspective is offered on the
current status of the Sharp Lepton Problem, and alternative non-heavy-ion
experimental approaches to it are recommended.


title:
Repulsive Core of NN S-Wave Scattering in a Quark Model with a Condensed
  Vacuum

abstract:
  We work in a chiral invariant quark model, with a condensed vacuum,
characterized by only one parameter. Bound state equations for the nucleon and
Delta are solved in order to obtain an updated value of their radii and masses.
Nucleon-nucleon S-Wave scattering is studied in the RGM framework both for
isospin T=1 and T=0. The phase shifts are calculated and an equivalent local
potential, which is consistent with K-N scattering, is derived. The result is a
reasonable microscopic short range repulsion in the nucleon-nucleon
interaction.


title:
Binding and Off-Mass-Shell Effects in Deep Inelastic Scattering on
  Deuteron

abstract:
  The role of relativistic off-mass-shell kinematics in the deep inelastic
scattering on deuteron is analyzed. It is shown that the relativistic impulse
approximation reproduces effects from the binding, Fermi motion, and
two-nucleon contribution. The nonrelativistic limit of the deuteron structure
function is in agreement with the nonrelativistic calculations.


title: The Eta-Nucleon Scattering Length and Effective Range

abstract:
  The coupled eta N, pi N system is described by a K-matrix method. The
parameters in this model are adjusted to get an optimal fit to pi N -> pi N, pi
N -> eta N and gamma N -> eta N data in an energy range of about 100MeV each
side of the eta threshold. In the notation T^(-1)+iq_(eta) = 1/a + (r_0)/2
q^2_(eta) + s q^4_(eta), q_(eta) being the momentum in the eta N
center-of-mass, the resulting effective range parameters for eta N scattering
are found to be a(fm) = 0.75(4)-i0.27(3), r_0(fm) = -1.50(13)-i0.24(4) and
s(fm^3) = -0.10(2)-i0.01(1)


title: Excess of pions with chiral symmetry restoration

abstract:
  We study the effect of the chiral phase transition on pion production in hot
hadronic matter. The phase of restored chiral symmetry is characterized by the
appearance of the scalar $\sigma$-meson as a chiral partner of the pion as well
as by the degeneracy of the vector and axial-vector mesons. We find rapid
thermal and chemical equilibration of these degrees of freedom in the symmetric
phase. Provided that the chiral transition temperature is not considerably
high, the presence of a chirally symmetric phase will result in $\sim 1.6$
times more thermal pions in the final state.


title: Rho-meson mass in light nuclei

abstract:
  The quark-meson coupling (QMC) model is applied to a study of the mass of the
$\rho$-meson in helium and carbon nuclei. The average mass of a $\rho$-meson
formed in $^{3,4}$He and $^{12}$C is expected to be around 730, 690 and 720
MeV, respectively.


title: Liquid-Gas Phase Transition in Nuclear Equation of State

abstract:
  A canonical ensemble model is used to describe a caloric curve of nuclear
liquid-gas phase transition. Allowing a discontinuity in the freeze out density
from one spinodal density to another for a given initial temperature, the
nuclear liquid-gas phase transition can be described as first order. Averaging
over various freeze out densities of all the possible initial temperatures for
a given total reaction energy, the first order characteristics of liquid-gas
phase transition is smeared out to a smooth transition. Two experiments, one at
low beam energy and one at high beam energy show different caloric behaviors
and are discussed.


title:
Bloom-Gilman duality of inelastic structure functions in nucleon and
  nuclei

abstract:
  The Bloom-Gilman local duality of the inelastic structure function of the
proton, the deuteron and light complex nuclei is investigated using available
experimental data in the squared four-momentum transfer range from 0.3 to 5
(GeV/c)**2. The results of our analysis suggest that the onset of the
Bloom-Gilman local duality is anticipated in complex nuclei with respect to the
case of the protonand the deuteron. A possible interpretation of this result in
terms of a rescaling effect is discussed with particular emphasis to the
possibility of reproducing the damping of the nucleon-resonance transitions
observed in recent electroproduction data off nuclei.


title: Fermionic Molecular Dynamics

abstract:
  A quantum molecular model for fermions is investigated which works with
antisymmetrized many-body states composed of localized single-particle wave
packets. The application to the description of atomic nuclei and collisions
between them shows that the model is capable to address a rich variety of
observed phenomena. Among them are shell effects, cluster structure and
intrinsic deformation in ground states of nuclei as well as fusion, incomplete
fusion, dissipative binary collisions and multifragmentation in reactions
depending on impact parameter and beam energy. Thermodynamic properties studied
with long time simulations proof that the model obeys Fermi-Dirac statistics
and time averaging is equivalent to ensemble averaging. A first order
liquid-gas phase transition is observed at a boiling temperature of $T \approx
5 MeV$ for finite nuclei of mass $16...40$.


title: PCAC in Nuclear Medium and the Lovelace-Shapiro-Veneziano formula

abstract:
  A simple way to enforce the Adler zero condition for pion amplitudes in the
nuclear medium is to use the Lovelace quantization condition but with modified
Regge Slope $\alpha'$ This latter is related to change in the gluon condensate.
Increasing nuclear density leads to a relative increase in the Regge Slope
$\alpha'$ Denoting this increase by a scale factor $\lambda$, the drop in the
$\rho$-mass, $\Delta-N$ mass difference, increase in $\pi\pi$ scattering
length, decrease of pion decay constant etc. are simply related to $\lambda$.


title: Magnetic Dipole Sum Rules for Odd-Mass Nuclei

abstract:
  Sum rules for the total- and scissors-mode M1 strength in odd-A nuclei are
derived within the single-j interacting boson-fermion model. We discuss the
physical content and geometric interpretation of these sum rules and apply them
to ^{167}Er and ^{161}Dy. We find consistency with the former measurements but
not with the latter.


title: Kaon Interferometry as Signal for the QCD Phase Transition at RHIC

abstract:
  Pion and kaon correlations in relativistic nuclear collisions are studied in
the framework of boost-invariant, cylindrically symmetric hydrodynamics. It is
investigated how the inverse widths of the two-particle correlation functions
in out- and side-direction depend on the average transverse momentum of the
particle pair, the initial energy density, and the equation of state of the
system. The QCD transition leads to a time delay in the expansion of the system
and consequently to an enhancement of the ratio of inverse widths in out- and
side-direction. This time-delay signal is found to be particularly strong for
large average transverse momenta of order 1 GeV and initial energy densities
accessible at RHIC. Neutral kaon pair correlation functions, which are not
influenced by final state Coulomb effects and less contaminated by resonance
decays than pion correlation functions, seem to be the ideal tool to detect
this collective time-delay signature of the QCD transition.


title:
Ground state properties of the $\beta$ stable nuclei in various mean
  field theories

abstract:
  The separation energies of neutrons and protons, binding energies, mean
square charge radii, electric quadrupole moments and deformation parameters of
the proton and neutron distributions are evaluated for $\beta$ stable even-even
nuclei with $16 \leq A \leq 256$. We compare the theoretical estimates obtained
within the Hartree-Fock plus BCS model with a few sets of Skyrme forces,
relativistic mean-field theory and frequently used Saxon-Woods and Nilsson
potentials with experimental data.


title: Stochastic Methods for Zero Energy Quantum Scattering

abstract:
  We investigate the use of stochastic methods for zero energy quantum
scattering based on a path integral approach. With the application to the
scattering of a projectile from a nuclear many body target in mind, we use the
potential scattering of a particle as a test for the accuracy and efficiency of
several methods. To be able to deal with complex potentials, we introduce a
path sampling action and a modified scattering observable. The approaches
considered are the random walk, where the points of a path are sequentially
generated, and the Langevin algorithm, which updates an entire path. Several
improvements are investigated. A cluster algorithm for dealing with scattering
problems is finally proposed, which shows the best accuracy and stability.


title: On the Dirac Structure of the Nucleon Selfenergy in Nuclear Matter

abstract:
  The relativistic structure of the self-energy of a nucleon in nuclear matter
is investigated including the imaginary and real components which arise from
the terms of first and second order in the NN interaction. A parameterized form
of Brueckner $G$ matrix is used for the NN interaction. The effects of the
terms beyond the DBHF approximation on quasiparticle energies and the optical
potential for nucleon-nucleus scattering are discussed.