title: The "Hole" In He

abstract:
  The measurement and analysis of electron scattering from He-3 and He-4 by
Sick and collaborators reported 20 years ago remains a matter of current
interest. By unfolding the measured free-proton charge distribution, they
deduced a depression in the central point nucleon density, which is not found
in few-body calculations based on realistic potentials. We find that using wave
functions from such calculations we can obtain good fits to the He charge
distributions under the assumption that the proton charge size expands toward
the center of the nucleus. The relationship to 6-quark Chromo-Dielectric Model
calculations, is discussed. The expansion is larger than than the predictions
of mean field bag calculations by others or our CDM calculations in the
independent pair approximation. There is interest here in the search for a
"smoking gun" signal of quark substructure.


title:
Model calculations of doubly closed shell nuclei in CBF theory III. j-j
  coupling and isospin dependence

abstract:
  Correlated Basis Function theory and Fermi Hypernetted Chain technique are
extended to study medium-heavy, doubly closed shell nuclei in j-j coupling
scheme, with different single particle wave functions for protons and neutrons
and isospin dependent two-body correlations. Central semirealistic interactions
are used. Ground state energies, one-body densities, distribution functions and
momentum distributions are calculated for 12C, 16O, 40Ca, 48Ca and 208Pb
nuclei. The values of the ground state energies provided by isospin dependent
correlations are lower than those obtained with isospin independent
correlations. In finite nuclear systems, the two--body Euler equations provide
correlation functions variationally more effective than those obtained with the
same technique in infinite nuclear matter.


title: Pion and photon induced reactions on the nucleon in a unitary model

abstract:
  We present a relativistic calculation of pion scattering, pion
photoproduction and Compton scattering on the nucleon in the energy region of
the \Del-resonance (upto 450 MeV photon lab energy), in a unified framework
which obeys the unitarity constraint. It is found that the recent data on the
cross section for nucleon Compton scattering determine accurately the
parameters of the electromagnetic nucleon--\Del\ coupling. The calculated
pion-photoproduction partial-wave amplitudes agree well with the recent Arndt
analysis.


title: Onset of Rotational Damping in Superdeformed Nuclei

abstract:
  We discuss damping of the collective rotational motion in $A\sim 150$
superdeformed nuclei by means of a shell model combining the cranked Nilsson
mean-filed and the surface-delta two-body residual force. It is shown that,
because of the shell structure associated with the superdeformed mean-field,
onset energy of the rotational damping becomes $E_x \sim 2-3 $ MeV above yrast
line, which is much higher than in normal deformed nuclei. The mechanism of the
shell structure effect is investigated through detailed analysis of level
densities in superdeformed nuclei. It is predicted the onset of damping varies
in different supedeformed nuclei along with variation in the single-particle
structure at the Fermi surface.


title: A Quantum-Mechanical Equivalent-Photon Spectrum for Heavy-Ion Physics

abstract:
  In a previous paper, we calculated the fully quantum-mechanical cross section
for electromagnetic excitation during peripheral heavy-ion collisions. Here, we
examine the sensitivity of that cross section to the detailed structure of the
projectile and target nuclei. At the transition energies relevant to nuclear
physics, we find the cross section to be weakly dependent on the projectile
charge radius, and to be sensitive to only the leading momentum-transfer
dependence of the target transition form factors. We exploit these facts to
derive a quantum-mechanical ``equivalent-photon spectrum'' valid in the
long-wavelength limit. This improved spectrum includes the effects of
projectile size, the finite longitudinal momentum transfer required by
kinematics, and the response of the target nucleus to the off-shell photon.


title: Oscillations of the static meson fields at finite baryon density

abstract:
  The spatial dependence of static meson correlation functions at finite baryon
density is studied in the Nambu -- Jona - Lasinio model. In contrast to the
finite temperature case, we find that the correlation functions at finite
density are not screened but exhibit long-range oscillations. The observed
phenomenon is analogous to the Friedel oscillations in a degenerate electron
gas.


title: Modified Quark-Meson Coupling Model for Nuclear Matter

abstract:
  The quark-meson coupling model for nuclear matter, which describes nuclear
matter as non-overlapping MIT bags bound by the self-consistent exchange of
scalar and vector mesons, is modified by introducing medium modification of the
bag constant. We model the density dependence of the bag constant in two
different ways: one invokes a direct coupling of the bag constant to the scalar
meson field, and the other relates the bag constant to the in-medium nucleon
mass. Both models feature a decreasing bag constant with increasing density. We
find that when the bag constant is significantly reduced in nuclear medium with
respect to its free-space value, large canceling isoscalar Lorentz scalar and
vector potentials for the nucleon in nuclear matter emerge naturally. Such
potentials are comparable to those suggested by relativistic nuclear
phenomenology and finite-density QCD sum rules. This suggests that the
reduction of bag constant in nuclear medium may play an important role in low-
and medium-energy nuclear physics.


title: Possible Production of the Sigma Meson in Nuclei

abstract:
  It should be a typical subject in this workshop to explore possible change of
hadron properties in association with that of QCD vacuum due to an
environmental change. In this report, we first summarize what hadrons are
expected to show such a change and how they do. Then we propose several
experiments including the ones utilizing electron and photon beams for
examining possible restoration of chiral symmetry in nuclei and the possible
existence of the sigma meson. The experiments are based on the observation that
the sigma meson may decrease the mass and the width along with the partial
restoration of chiral symmetry in the medium.


title:
Occupation probability of harmonic-oscillator quanta for microscopic
  cluster-model wave functions

abstract:
  We present a new and simple method of calculating the occupation probability
of the number of total harmonic-oscillator quanta for a microscopic
cluster-model wave function. Examples of applications are given to the recent
calculations including $\alpha+n+n$-model for $^6$He, $\alpha+t+n+n$-model for
$^9$Li, and $\alpha+\alpha+n$-model for $^9$Be as well as the classical
calculations of $\alpha+p+n$-model for $^6$Li and $\alpha+\alpha+\alpha$-model
for $^{12}$C. The analysis is found to be useful for quantifying the amount of
excitations across the major shell as well as the degree of clustering. The
origin of the antistretching effect is discussed.


title: On the asymptotical equations in the harmonic oscillator representation

abstract:
  In the harmonic oscillator representation, the Schrodinger equation has a
form of a set of infinite number of algebraical equations which are labeled by
the radial quantum number "n". It is shown that at n>>1 these equations are
significantly simplified and become an algebraical analogue of the original
differential Schrodinger equation. This result is generalized to the case of
multi-channel systems being studied in the framework of the resonating group
method.


title: Meson-hyperon couplings in the bound-state approach to the Skyrme model

abstract:
  Strong pion and kaon couplings to hyperons are given in the bound-state
approach to the Skyrme model.


title: A Non-Perturbative Treatment of the Pion in the Linear Sigma-Model

abstract:
  Using a non-perturbative method based on the selfconsistent Quasi-particle
Random-Phase Approximation (QRPA) we describe the properties of the pion in the
linear $\sigma$-model. It is found that the pion is massless in the chiral
limit, both at zero- and finite temperature, in accordance with Goldstone's
theorem.


title:
Variation of transport coefficients for average fission dynamics with
  temperature and shape

abstract:
  We study slow collective motion at finite thermal excitations on the basis of
linear response theory applied to the locally harmonic approximation. The
transport coefficients for average motion, friction \gamma, inertia M and the
local stiffness C are computed along a fission path of Th-224 within a
quasi-static picture. The inverse relaxation time \beta=\gamma/M and the
effective damping rate \eta=\gamma/(2\sqrt{M|C|}) are found to increase with
temperature, but do not change much with the collective variable. The values
found for \eta and \beta as well as their behavior with temperature are in
accord with experimental findings.


title: The Nuclear response in the isoscalar channel

abstract:
  The nuclear response is evaluated in the frame of the bosonic loop expansion
in a purely nucleonic dynamical scheme, which seems to be reliable in handling
those channels where a direct excitation of a $\Delta$-resonance is not
allowed. It is shown that the response strongly depends upon the effective
interaction in the spin-transverse isovector channel. New experiments at CEBAF
on parity-violating electron scattering could further constrain the form of the
effective interaction.


title: Electromagnetic Couplings of Nucleon Resonances

abstract:
  An effective Lagrangian calculation of pion photoproduction including all
nucleon resonances up to $\sqrt s = 1.7$ GeV is presented. We compare our
results to recent calculations and show the influence of different width
parametrizations and offshell cutoffs on the photoproduction multipoles. We
determine the electromagnetic couplings of the resonances from a new fit to the
multipole data.


title:
Coulomb-Sturmian separable expansion approach: Three-body Faddeev
  calculations for Coulomb-like interactions

abstract:
  We demonstrate the feasibility and efficiency of the Coulomb-Sturmian
separable expansion method for generating accurate solutions of the Faddeev
equations. Results obtained with this method are reported for several benchmark
cases of bosonic and fermionic three-body systems. Correct bound-state results
in agreement with the ones established in the literature are achieved for
short-range interactions. We outline the formalism for the treatment of
three-body Coulomb systems and present a bound-state calculation for a
three-boson system interacting via Coulomb plus short-range forces. The
corresponding result is in good agreement with the answer from a recent
stochastic-variational-method calculation.


title: Self-energy of Lambda in finite nuclei

abstract:
  The self--energy of the strange baryon $\Lambda$ in $^{17}$O is calculated
using a microscopic many--body approach which accounts for correlations beyond
the mean--field or Hartree--Fock approximation. The non-locality and
energy-dependence of the $\Lambda$ self--energy is discussed and the effects on
the bound and scattering states are investigated. For the nucleon--hyperon
interaction, we use the potential models of the J\"{u}lich and Nijmegen groups.


title:
Searching for the Nuclear Liquid-Gas Phase Transition in Au + Au
  Collisions at 35 MeV/nucleon

abstract:
  Within the framework of Classical Molecular Dynamics, we study the collision
Au + Au at an incident energy of 35 MeV/nucleon. It is found that the system
shows a critical behaviour at peripheral impact parameters, revealed through
the analysis of conditional moments of charge distributions, Campi Scatter
Plot, and the occurrence of large fluctuations in the region of the Campi plot
where this critical behaviour is expected. When applying the experimental
filters of the MULTICS-MINIBALL apparatus, it is found that criticality signals
can be hidden due to the inefficiency of the experimental apparatus. The
signals are then recovered by identifying semi-peripheral and peripheral
collisions looking to the velocity distribution of the largest fragment, then
by selecting the most complete events.


title: Amplitude analysis of the $\overline{N}N \to K^-K^+$ reaction

abstract:
  A simple partial wave amplitude analysis of $\overline{p}p \rightarrow
K^-K^+$ has been performed for data in the range $p_{\rm lab}$ = 360 -- 1000
MeV/$c$. In this low momentum interval only partial wave amplitudes with $J$
equal to 0, 1 and 2 are needed to obtain a good fit to the experimental data.
This maximal $J$ = 2 value is smaller than what is required for the data of the
reaction $\overline{p}p \rightarrow \pi^-\pi^+$ in the same momentum interval.


title: $^{35}$Cl+$^{12}$C Asymmetrical fission excitation functions

abstract:
  The fully energy-damped yields from the $^{35}$Cl+$^{12}$C reaction have been
systematically investigated using particle-particle coincidence techniques at a
$^{35}$Cl bombarding energy of $\sim$ 8 MeV/nucleon. The fragment-fragment
correlation data show that the majority of events arises from a binary-decay
process with rather large numbers of secondary light-charged particles emitted
from the two excited exit fragments. No evidence is observed for ternary
break-up events. The binary-process results of the present measurement, along
with those of earlier, inclusive experimental data obtained at several lower
bombarding energies are compared with predictions of two different kinds of
statistical model calculations. These calculations are performed using the
transition-state formalism and the Extended Hauser-Feshbach method and are
based on the available phase space at the saddle point and scission point of
the compound nucleus, respectively. The methods give comparable predictions and
are both in good agreement with the experimental results thus confirming the
fusion-fission origin of the fully-damped yields. The similarity of the
predictions for the two models supports the claim that the scission point
configuration is very close to that of the saddle point for the light $^{47}$V
mass-asymmetry-dependent fission barriers needed in the transition-state
calculation.


title: Triplet pairing in beta-stable neutron star matter

abstract:
  $^{3}P_{2}$ pairing in neutron matter is investigated using the Bonn
potential models. We find pairing energy gaps in pure neutron matter comparable
to the results of previous investigators when the attractive tensor coupling is
included. However, taking into account that in a neutron star we have matter at
$\beta$ equilibrium, we find that the $^{3}P_{2}$-$^{3}F_{2}$ energy gap is
reduced considerably.


title: Matter radii of light halo nuclei

abstract:
  We re-examine the matter radii of diffuse halo nuclei, as deduced from
reaction cross section measurements at high energy. Careful consideration is
given to the intrinsic few-body structure of these projectiles and the
adiabatic nature of the projectile-target interaction. Using $^{11}$Li,
$^{11}$Be and $^{8}$B as examples we show that data require significantly
larger matter radii than previously reported. The revised value for $^{11}$Li
of 3.55 fm is consistent with three-body models with significant $1s$-intruder
state components, which reproduce experimental $^{9}$Li momentum distributions
following $^{11}$Li breakup, but were hitherto thought to be at variance with
cross section data.


title: Coherent Pion Pairs from Heavy-Ion Collisions

abstract:
  The degree to which a nucleus can act as a source for coherent pion pairs is
investigated for intermediate-energy heavy-ion collisions. Creation through
both isovector and isoscalar channels is considered. Two experimental signals
are proposed for evidence of two-pion coherent production, two-pion enhancement
and the focusing of outgoing pions along the beam axis.


title:
Excess electron pairs from heavy-ion collisions at CERN and a more
  complete picture of thermal production

abstract:
  The low-mass dielectron signal from heavy-ion collisions at the CERN--SPS
reported by the {\em CERES} collaboration is in excess of estimated hadronic
decays suggestive of possible contribution from two-pion annihilation or other
hadronic reactions. In the absence of dramatic medium modifications,
annihilation alone is unable to account for the data. We explore the role of
pion plus resonance scattering [$\pi\rho\to a_{1}(1260) \to \pi e^+e^-$] which
has favorable kinematics to populate masses between $2m_{\pi}$ and $m_{\rho}$.
While it seems to account for some of the remaining excess beyond annihilation,
it fails to allow quantitative interpretation of data.


title: Collision broadening of rho meson in a dropping mass scenario

abstract:
  Vector mesons containing light quarks are thought to have their masses
reduced in dense nuclear matter, sacrificing some of their energy to the scalar
field which becomes appreciable at finite baryon density. Model calculations
find masses which fall by a couple tens of percents in normal nuclear matter,
and by several hundred MeV in dense matter. We estimate the collision rate for
rho mesons in such a scenario and at finite temperature. Compared to its
free-mass value, the collision rate changes by nearly a factor of two both
above and below, depending on the density. This collision broadening effect
could be important for estimates of low-mass dilepton production in heavy-ion
collisions.


title: Extensive Hartree-Fock + BCS calculation with Skyrme SIII force

abstract:
  We have performed deformed Hartree-Fock+BCS calculations with the Skyrme SIII
force for the ground states of even-even nuclei with 2 <= Z <= 114 and N
ranging from outside the proton drip line to beyond the experimental frontier
in the neutron-rich side. We obtained spatially localized solutions for 1029
nuclei, together with the second minima for 758 nuclei. The single-particle
wavefunctions are expressed in a three-dimensional Cartesian-mesh
representation, which is suitable to describe nucleon skins, halos, and exotic
shapes as well as properties of ordinary stable nuclei. After explaining some
of the practical procedures of the calculations, we compare the resulting
nuclear masses with experimental data and the predictions of other models. We
also discuss the quadrupole (m=0, 2) and hexadecapole (m=0, 2, 4) deformations,
the skin thicknesses, the halo radii, and the energy difference between the
oblate and the prolate solutions. Our results can be obtained via computer
network.


title: $\eta$-Deuteron Scattering

abstract:
  Eta-deuteron scattering lengths are calculated. A summation of the multiple
scattering series is carried out and the result is checked against more
involved calculations. The necessity to go beyond the fixed nucleon
approximation is emphasized. It is shown that a quasibound or virtual state in
the $\eta$-deuteron system may occur within the range of $\eta$-nucleon
scattering lengths suggested by other experiments.


title: Backbending in 50Cr

abstract:
  The collective yrast band and the high spin states of the nucleus 50Cr are
studied using the spherical shell model and the HFB method. The two
descriptions lead to nearly the same values for the relevant observables. A
first backbending is predicted at I=10\hbar corresponding to a collective to
non-collective transition. At I=16\hbar a second backbending occurs, associated
to a configuration change that can also be interpreted as an spherical to
triaxial transition.


title: Inclusion of Quantum Fluctuations in Wave Packet Dynamics

abstract:
  We discuss a method by which quantum fluctuations can be included in
microscopic transport models based on wave packets that are not energy
eigenstates. By including the next-to-leading order term in the cumulant
expansion of the statistical weight, which corresponds to the wave packets
having Poisson energy distributions, we obtain a much improved global
description of the quantum statistical properties of the many-body system. In
the case of atomic nuclei, exemplified by 12C and 40Ca, the standard
liquid-drop results are reproduced at low temperatures and a phase
transformation to a fragment gas occurs as the temperature is raised. The
treatment can be extended to dynamical scenarios by means of a Langevin force
emulating the transitions between the wave packets. The general form of the
associated transport coefficients is derived and it is shown that the
appropriate microcanonical equilibrium distribution is achieved in the course
of the time evolution. Finally, invoking Fermi's golden rule, we derive
specific expressions for the transport coefficients and verify that they
satisfy the fluctuation-dissipation theorem.


title: Superfluidity in beta-stable neutron star matter

abstract:
  In this work we present results for pairing gaps in $\beta$--stable neutron
star matter with electrons and muons using a relativistic
Dirac--Brueckner--Hartree--Fock approach, starting with modern meson--exchange
models for the nucleon--nucleon interaction. Results are given for
superconducting $^1S_0$ protons and $^3P_2$ and $^1D_2$ neutron superfluids. A
comparison is made with recent non--relativistic calculations and the
implications for neutron star cooling are discussed.


title: Spin polarised nuclear matter and its application to neutron stars

abstract:
  An equation of state(EOS) of nuclear matter with explicit inclusion of a
spin-isospin dependent force is constructed from a finite range, momentum and
density dependent effective interaction. This EOS is found to be in good
agreement with those obtained from more sophisticated models for unpolarised
nuclear matter. Introducing spin degrees of freedom, it is found that at
density about 2.5 times the density of normal nuclear matter the neutron matter
undergoes a ferromagnetic transition. The maximum mass and the radius of the
neutron star agree favourably with the observations. Since finding quark matter
rather than spin polarised nuclear matter at the core of neutron stars is more
probable, the proposed EOS is also applied to the study of hybrid stars. It is
found using the bag model picture that one can in principle describe both the
mass and size as well as the surface magnetic field of hybrid stars
satisfactorily.


title: Near threshold eta production in proton-proton collisions

abstract:
  The total cross section for the near threshold eta production in
proton-proton collisions has been investigated with the assumption that the
production mechanism is due to the emission of a meson x (pi, eta, sigma) from
one of the nucleons followed by a x N --> eta N transition on the second one.
The x N --> eta N amplitudes are generated from the unitary multi-channel
multi-resonance model which has recently been constructed in analyzing the pi N
scattering and pi N --> eta N reaction. The initial and final pp distortions
are calculated from a coupled-channel pi-NN model which describes the NN
scattering data up to about 2 GeV. With the x-NN vertex functions taken from
the Bonn potential, the predicted total cross sections of threshold pp --> eta
pp reaction are in good agreement with the data. In contrast to previous works,
we find that the eta-exchange plays an important role. The effect of the
two-pion exchange, simulated by sigma- exchange, is found to be significant but
not as dominant as the vector meson-exchange introduced in previous works.


title: Shell-like Structures in an expanding Quark-Antiquark Plasma

abstract:
  The particle density distribution emerging from the solution of the Vlasov
equation for relativistic, non-interacting particles with spherically symmetric
initial conditions is shown to exhibit a shell-like structure for late fixed
times in the center-of-mass (CM) frame of the system. A similar phenomenon was
recently observed employing the test-particle method to solve the Vlasov
equation for quarks with Nambu-Jona-Lasinio-type interactions, and was
attributed to the attractive forces among the particles. Contrary to this
claim, it is demonstrated here that this effect is of purely relativistic
origin and is sensitive only to the mass of the particles and their initial
phase-space distribution.


title:
Angular Distributions for Knockout and Scattering of Protons in the
  Eikonal Approximation

abstract:
  The advent of new electron accelerators with few-GeV beam energies makes the
(e,e'p) reaction a promising tool for investigating new aspects of the
electromagnetic interaction. To this purpose it is crucial to set the scale of
Final-State Interactions (FSI) at high ejectile energies. We have analyzed the
constraints which allow for a meaningful generalization to (e,e'p) of the
Glauber method used in elastic (p,p) scattering. The FSI dominance at large
deflection angles produces in the distributions a universal behaviour
resembling the coherent diffractive scattering between the ejected proton and
the (residual) nucleus. It is argued that the comparison between (e,e'p) and
(p,p), when a meaningful one, may represent a convenient tool to disentangle
(exotic) effects due to FSI from those related to the (hard) electromagnetic
vertex.


title: What Do We Learn from Atomic Physics about Fundamental Symmetries?

abstract:
  Valuable information on interactions violating $P$- and $T$-invariance can be
extracted from atomic experiments. The hypothesis of a large weak matrix
element between single-particle states in heavy nuclei, $\sim 100$ eV, is ruled
out by measurements of parity nonconservation in atoms. Experimental upper
limit on the electric dipole moment of the $^{199}$Hg atom strictly constrains
parameters of $CP$-violation models. Upper limit on the $T$-odd, $P$-even
admixture to nuclear forces is set: $\alpha_T\,<\,10^{-11}$.


title: Scaling Behavior in Soliton Models

abstract:
  In the framework of chiral soliton models we study the behavior of static
nucleon properties under rescaling of the parameters describing the effective
meson theory. In particular we investigate the question of whether the
Brown--Rho scaling laws are general features of such models. When going beyond
the simple Skyrme model we find that restrictive constraints need to be imposed
on the mesonic parameters in order to maintain these scaling laws. Furthermore,
in the case when vector mesons are included in the model it turns out that the
isoscalar form factor no longer scales according to these laws. Finally we note
that, in addition to the exact scaling laws of the model, one may construct
approximate {\it local scaling laws}, which depend of the particular choice of
Lagrangian parameters.


title: Nucleon-Nucleon Scattering from Effective Field Theory

abstract:
  We perform a nonperturbative calculation of the 1S0 NN scattering amplitude
using an effective field theory (EFT) expansion. The expansion we advocate is a
modification of what has been used previously; it is no a chiral expansion in
powers of the pion mass. We use dimensional regularization throughout and the
MS-bar subtraction scheme; our final result depends only on physical
observables. We show that the EFT expansion of the quantity |p|cot delta(p)
converges at momenta much greater than the scale that characterizes the
derivative expansion of the EFT Lagrangian. Our conclusions are optimistic
about the applicability of an EFT approach to the quantitative study of nuclear
matter.


title: Virtual Compton scattering off nuclei in the $\Delta$-resonance region

abstract:
  Virtual Compton scattering in the $\Delta$-resonance region is considered in
the case of a target nucleus. The discussion involves generalized
polarizabilities and is developed for zero-spin nuclei, focusing on the new
information coming from virtual Compton scattering in comparison with real
Compton scattering.


title:
Solving the four-dimensional $NN-\pi NN$ equations for scalars below
  meson-production threshold

abstract:
  The four-dimensional $NN-\pi NN$ equations are adapted to the case of scalar
particles with a $\phi^2\sigma$ interaction Lagrangian, and solved for energies
below the $\sigma$-production threshold. This is achieved in the approximation
where $\phi\sigma$ scattering is dominated by the $s$-channel $\phi$-pole term.
The importance of the removal of double-counting is investigated, and a
detailed comparison of the results of a covariant coupled-channels formulation
and the Bethe-Salpeter equation in the ladder and ladder plus crossed-box
approximations is presented. A brief discussion of the extension of the method
to energies above the $\sigma$-production threshold is given.


title:
Sensitivity of nucleon-nucleus scattering to the off-shell behavior of
  on-shell equivalent NN potentials

abstract:
  The sensitivity of nucleon-nucleus elastic scattering to the off-shell
behavior of realistic nucleon-nucleon interactions is investigated when
on-shell equivalent nucleon-nucleon potentials are used. The study is based on
applications of the full-folding optical model potential for an explicit
treatment of the off-shell behavior of the nucleon-nucleon effective
interaction. Applications were made at beam energies between 40 and 500 MeV for
proton scattering from 40Ca and 208Pb. We use the momentum-dependent Paris
potential and its local on-shell equivalent as obtained with the
Gelfand-Levitan and Marchenko inversion formalism for the two nucleon
Schroedinger equation. Full-folding calculations for nucleon-nucleus scattering
show small fluctuations in the corresponding observables. This implies that
off-shell features of the NN interaction cannot be unambiguously identified
with these processes. Inversion potentials were also constructed directly from
NN phase-shift data (SM94) in the 0-1.3 GeV energy range. Their use in
proton-nucleus scattering above 200 MeV provide a superior description of the
observables relative to those obtained from current realistic NN potentials.
Limitations and scope of our findings are presented and discussed.


title: The Effect of Nuclear Shape

abstract:
  The effect of projectile shape on cross sections and momentum distributions
of fragments from heavy ion reactions is studied. We propose a new approach
that implements the underlying symmetries of each isotope with a few parameters
directly in the density. Various densities and their nuclear structure are then
analyzed in the reactions of $^{12}$C and $^{11}$Li, $^{11}$Be, and $^{11}$C on
a carbon target.


title:
Multiple Scattering Theory for the Photoproduction of Vector Mesons off
  Nuclei

abstract:
  The integrated cross section for the incoherent photoproduction of vector
mesons on nuclei $\gamma^* A \to VX$, $X\not=A$, is calculated within Glauber
theory and as a function of the photon energy. The inverse of the longitudinal
momentum transfer is called coherence length $l_c$ and depends on the
virtuality and the energy of the photon. Nuclear transmission factors strongly
depend on $l_c/R_A$ ($R_A$ is the nuclear radius) and this effect may interfere
with the search for color transparency effects.


title:
The position and the residues of the delta resonance pole in pion
  photoproduction

abstract:
  We have analyzed the $M_{1+}^{(3/2)}$ and $E_{1+}^{(3/2)}$ multipole
amplitudes of pion photoproduction in the framework of fixed-$t$ dispersion
relations. Applying the speed plot technique to our results for these
multipoles, we have determined the position and the residues of the $\Delta$
(1232) resonance pole. The pole is found at total $c.m.$ energy $W = (1211 -
50i)$ MeV on the second Riemann sheet, and the ratio of the electric and
magnetic residues is $R_{\Delta} = - 0.035 - 0.046 i$, resulting in an E2/M1
ratio for the "dressed" delta resonance of $- 3.5 \%$.


title: Path Integral Variational Methods for Strongly Correlated Systems

abstract:
  We introduce a new approach to highly correlated systems which generalizes
the Fermi Hypernetted Chain and Correlated Basis Function techniques. While the
latter approaches can only be applied to systems for which a nonrelativistic
wave function can be defined, the new approach is based on the variation of a
trial hamiltonian within a path integral framework and thus can also be applied
to relativistic and field theoretical problems. We derive a diagrammatic scheme
for the new approach and show how a particular choice of the trial hamiltonian
corresponds exactly to the use of a Jastrow correlated ansatz for the wave
function in the Fermi Hypernetted Chain approach. We show how our new approach
can be used to find upper bounds to ground state energies in systems which the
FHNC cannot handle, including those described by an energy-dependent effective
hamiltonian. We demonstrate our approach by applying it to a quantum field
theoretical system of interacting pions and nucleons.


title: Hyperon-rich matter

abstract:
  The phase diagram of nuclear matter is extended to strangeness and
antimatter. It offers fascinating features for heavy ion physics and
astrophysics. We will discuss some regions of this phase diagram as strange
matter at zero temperature, hypermatter at high densities and the antiworld at
high densities and strangeness fraction.


title: Can dileptons be observed in heavy ion collisions at RHIC?

abstract:
  Both dilepton and charm production at RHIC are considered to be important
signatures for Quark-Gluon Plasma production. Recently it was argued by
S.Gavin, P.L.McGaughey,P.V. Ruuskanen and R.Vogt that the background from
semileptonic correlated charm decays is so large that it makes dilepton
measurements virtually impossible. We show that this conclusion in fact is in
fact reversed if the energy loss due to secondary interaction of charmed quarks
is included.


title: Quest for deconfined quark phase: A new avenue

abstract:
  Stability of droplets of $ud$ matter, {\it viz} udilets, is studied using
non-relativistic and relativistic bag models. It is found that there is a
strong possibility for forming hypercharged metastable udilets with charge
fraction $Z/A \ge 1$ in semicentral relativistic heavy ion collisions. It is
then speculated that protons hadronised from these hypercharged udilets may be
contributing towards the directed sideward flow observed recently in
experiment. This exotic state with large charge to mass ratio presents an
unique possibility for the spontaneous emission of positrons due to the
`sparking' of the vacuum.


title:
Nuclear $\beta$- and $\gamma$- Collective Bands in the SU$_q$(2) Rotator
  Model

abstract:
  The SU$_q$(2) rotator model is used for describing the $\beta_1$- and
$\gamma_1$-bands of even-even rare earth and actinide collective nuclei. Good
results are obtained in nuclei with valence pair number $N>10$. It is shown
that in the excited bands the violation of the exact SU(2) symmetry is
generally stronger than in the ground state bands, indicating the presence of a
nonadiabatic perturbation caused by the excited vibrational degrees of freedom.
The physical content of the parameter $q$ is discussed. Predictions of the
SU$_q$(2) model for B(E2) intraband transitions in excited bands are presented
and the need for specific experimental data is pointed out.


title:
Transverse momentum dependence of transverse flow in relativistic
  heavy-ion collisions

abstract:
  The strength of transverse flow is examined as a function of transverse
momentum $p_t$ using a simple, transversely moving thermal model and a more
realistic, relativistic transport model (ART). It is shown that the $p_t$
dependence reveals useful information about the collective flow that is
complementary to that obtained from the standard in-plane transverse momentum
analysis. Interesting features of using the $p_t$ dependence to study the
equation of state of the superdense hadronic matter formed in relativistic
heavy-ion collisions are demonstrated.


title:
Isospin dependence of collective flow in heavy-ion collisions at
  intermediate energies

abstract:
  Within the framework of an isospin-dependent Boltzmann-Uehling-Uhlenbeck
(BUU) model using initial proton and neutron densities calculated from the
nonlinear relativistic mean-field (RMF) theory, we compare the strength of
transverse collective flow in reactions $^{48}Ca+^{58}Fe$ and
$^{48}Cr+^{58}Ni$, which have the same mass number but different neutron/proton
ratios. The neutron-rich system ($^{48}Ca+^{58}Fe$) is found to show
significantly stronger negative deflection and consequently has a higher
balance energy, especially in peripheral collisions. NOTE ADDED IN PROOF: The
new phenomenon predicted in this work has just been confirmed by an experiment
done by G.D. Westfall et al. using the NSCL/MSU radioactive beam facility and a
spartan soccer. A paper by R. Pak et al. is submitted to PRL to report the
experimental result.


title:
Space-time extensions from space-time densities and Bose-Einstein
  correlations

abstract:
  Using a (3+1)-dimensional solution of the relativistic Euler-equations for
$Pb+Pb$ at 160 $AGeV$, space-time extensions of kaon emission zones are
calculated from space-time densities and compared to the inverse widths of
two-kaon Bose-Einstein correlation functions. The comparison shows a
satisfactory agreement and it is concluded that because of the Gaussian shape
of the kaon correlation functions, the space-time parameters of the kaon source
can be calculated directly from space-time densities. In the case of intensity
interferometry of identical pions this simplification is not recommended when
applying Gaussian fits because of the present strong effects of resonance
decays. The whole discussion is based on the assumption that hadron emission in
ultra-relativistic heavy-ion collisions is purely chaotic or that coherence is
at least negligible.


title: Effective T-odd P-even hadronic interactions from quark models

abstract:
  Tests of time reversal symmetry at low and medium energies may be analyzed in
the framework of effective hadronic interactions. Here, we consider the quark
structure of hadrons to make a connection to the more fundamental degrees of
freedom. It turns out that for P-even T-odd interactions hadronic matrix
elements evaluated in terms of quark models give rise to factors of 2 to 5.
Also, it is possible to relate the strength of the anomalous part of the
effective rho-type T-odd P-even tensor coupling to quark structure effects.


title: The deformation of the interacting nucleon in the Skyrme model

abstract:
  Changes in the nucleon shape are investigated by letting the nucleon deform
under the strong interactions with another nucleon. The parameters of the axial
deformations are obtained by minimizing the static energy of the two nucleon
system at each internucleon distance $ R $. It is shown that the intrinsic
quadrupole moment of the interacting proton, $Q_{p}$, is about $0.02 fm^2$ at
distances near $R \sim 1.25 $ fm.


title: Pairing and Isospin Symmetry in Proton-Rich Nuclei

abstract:
  Unlike their lighter counterparts, most odd-odd N=Z nuclei with mass A > 40
40 have ground states with isospin T=1, suggesting an increased role for the
isovector pairing interaction. A simple SO(5) seniority-like model of this
interaction reveals a striking and heretofore unnoticed interplay between
like-particle and neutron-proton isovector pairing near N=Z that is reflected
in the number of each kind of pair as a function of A and T. Large scale
shell-model calculations exhibit the same trends, despite the simultaneous
presence of isoscalar pairs, deformation, and other correlations.


title: Probing Nucleon Strangeness with Neutrinos: Nuclear Model Dependences

abstract:
  The extraction of the nucleon's strangeness axial charge, Delta_s, from
inclusive, quasielastic neutral current neutrino cross sections is studied
within the framework of the plane-wave impulse approximation. We find that the
value of Delta_s can depend significantly on the choice of nuclear model used
in analyzing the quasielastic cross section. This model-dependence may be
reduced by one order of magnitude when Delta_s is extracted from the ratio of
total proton to neutron yields. We apply this analysis to the interpretation of
low-energy neutrino cross sections and arrive at a nuclear theory uncertainty
of plus/minus 0.03 on the value of Delta_s expected to be determined from the
ratio of proton and neutron yields measured by the LSND collaboration. This
error compares favorably with estimates of the SU(3)-breaking uncertainty in
the value of Delta_s extracted from inclusive, polarized deep-inelastic
structure function measurements. We also point out several general features of
the quasielastic neutral current neutrino cross section and compare them with
the analogous features in inclusive, quasielastic electron scattering.


title:
Relativistic heavy ion collisions with realistic non-equilibrium mean
  fields

abstract:
  We study the influence of non-equilibrium phase space effects on the dynamics
of heavy ion reactions within the relativistic BUU approach. We use realistic
Dirac-Brueckner-Hartree-Fock (DBHF) mean fields determined for
two-Fermi-ellipsoid configurations, i.e. for colliding nuclear matter, in a
local phase space configuration approximation (LCA). We compare to DBHF mean
fields in the local density approximation (LDA) and to the non-linear Walecka
model. The results are further compared to flow data of the reaction $Au$ on
$Au$ at 400 MeV per nucleon measured by the FOPI collaboration. We find that
the DBHF fields reproduce the experiment if the configuration dependence is
taken into account. This has also implications on the determination of the
equation of state from heavy ion collisions.


title: Nuclear G-Matrix Elements from Nonlocal Potentials

abstract:
  We study effects of nonlocality in the nuclear force on the G-matrix elements
for finite nuclei. Nuclear G-matrix elements for $\O16$ are calculated in the
harmonic oscillator basis from a nonlocal potential which models quark exchange
effects between two nucleons. We employ a simple form of potential that gives
the same phase shifts as a realistic local nucleon potential. The G-matrix
elements calculated from the nonlocal potential show moderate increase in
repulsion from those derived from the local potential.


title: Dynamical Formation of Disoriented Chiral Condensates

abstract:
  We study the dynamical formation of disoriented chiral condensates in very
high energy nucleus-nucleus collisions using Bjorken hydrodynamics and
relativistic nucleation theory. It is the dynamics of the first order
confinement phase transition which controls the evolution of the system. Every
bubble or fluctuation of the new, hadronic, phase obtains its own chiral
condensate with a probability determined by the Boltzmann weight of the finite
temperature effective potential of the linear sigma model. We evaluate domain
size and chiral angle distributions, which can be used as initial conditions
for the solution of semiclassical field equations.


title:
Semi-inclusive Deep Inelastic Electron Scattering off the Deuteron and
  the Neutron to Proton Structure Function Ratio

abstract:
  The production of slow nucleons in semi-inclusive deep inelastic electron
scattering off the deuteron is investigated in the region $x \gsim 0.3$. It is
shown that within the spectator mechanism the semi-inclusive cross section
exhibits a scaling property even at moderate values of $Q^2$ ($\sim$ few
$(GeV/c)^2$) accessible at present facilities, like $CEBAF$. Such a scaling
property can be used as a model-independent test of the dominance of the
spectator mechanism itself and provides an interesting tool to investigate the
neutron structure function. The possibility of extracting model-independent
information on the neutron to proton structure function ratio from
semi-inclusive experiments is illustrated. The application of the spectator
scaling to semi-inclusive processes off complex nuclei is outlined.


title: Probing Hadronic Polarizations with Dilepton Anisotropies

abstract:
  We investigate the production of $e^+e^-$ pairs from $p + Be$ and
nucleus-nucleus collisions from 2 GeV/A to 200 GeV/A within a covariant
transport approach and focus on the dilepton angular anisotropies as a function
of the dilepton invariant mass. Whereas the low mass regime yields information
about the Dalitz decays of the $\Delta, \eta$ and $\omega$, above M $\approx
$0.5 GeV the angular anisotropies provide additional information about the
$\pi^+\pi^- \to \rho^0 \to e^+e^-$ channel in the medium. The anisotropy
coefficient is found to change its sign for M $>$ 0.5 GeV in case of
nucleus-nucleus reactions when increasing the bombarding energy from 2 GeV/A to
200 GeV/A which sheds some light on the $\pi \pi \to \rho$ dynamics.


title: Pion Transparency in 500 MeV C(pi,pi') Reactions?

abstract:
  The question whether there is a pion transparency in 500 MeV $C(\pi,
\pi^{'})$ scatterings is studied using a semiclassical, hadronic transport
model. The double differential cross sections of this reaction measured at
LAMPF can be largely accounted for, if one uses energy-dependent, anisotropic
angular distributions which are fitted to pion-nucleon scattering data for the
decay of $\Delta(1232)$ and $N^*(1440)$ resonances. The remaining discrepancy
between the data and the calculation sets a limit on effects of more exotic
processes.


title: Ground-state Spectrum of Light-quark Mesons

abstract:
  A confining, Goldstone theorem preserving, separable Ansatz for the ladder
kernel of the two-body Bethe-Salpeter equation is constructed from
phenomenologically efficacious $u$, $d$ and $s$ dressed-quark propagators. The
simplicity of the approach is its merit. It provides a good description of the
ground-state isovector-pseudoscalar, vector and axial-vector meson spectrum;
facilitates an exploration of the relative importance of various components of
the two-body Bethe-Salpeter amplitudes, showing that sub-leading Dirac
components are quantitatively important in the isovector-pseudoscalar meson
channels; and allows a scrutiny of the domain of applicability of ladder
truncation studies. A colour-antitriplet diquark spectrum is obtained.
Shortcomings of separable Ans\"atze and the ladder kernel are highlighted.


title: Ground--state energies and widths of $^5$He and $^5$Li

abstract:
  We extract energies and widths of the ground states of $^5$He and $^5$Li from
recent single--level R--matrix fits to the spectra of the $^3$H$({\rm
d},\gamma$)$^5$He and the $^3$He$({\rm d},\gamma$)$^5$Li reactions. The widths
obtained differ significantly from the formal R--matrix values but they are
close to those measured as full widths at half maxima of the spectra in various
experiments. The energies are somewhat lower than those given by usual
estimates of the peak positions. The extracted values are close to the
S--matrix poles calculated previously from the multi--term analyses of the
N-$^4$He elastic scattering data.


title: Meson Transition Form Factors From A QCD Model Field Theory

abstract:
  We discuss form factors and coupling constants for the $\gamma^* \pi^0
\gamma$, $\rho\pi\pi$ and $\gamma \pi \rho$ interactions generated by a model
field theory that produces finite size $\bar{q}q$ meson modes. The approach
implements dressing of the vertices and propagators consistent with dynamical
chiral symmetry breaking, gauge invariance, quark confinement and perturbative
QCD.


title: Virtual Compton scattering off the nucleon at low energies

abstract:
  We investigate the low-energy behavior of the four-point Green's function
$\Gamma^{\mu\nu}$ describing virtual Compton scattering off the nucleon.
  Using Lorentz invariance, gauge invariance, and crossing symmetry, we derive
the leading terms of an expansion of the operator in the four-momenta $q$ and
$q'$ of the initial and final photon, respectively.
  The model-independent result is expressed in terms of the electromagnetic
form factors of the free nucleon, i.e., on-shell information which one obtains
from electron-nucleon scattering experiments.
  Model-dependent terms appear in the operator at $O(q_\alpha q'_\beta)$,
whereas the orders $O(q_\alpha q_\beta)$ and $O(q'_\alpha q'_\beta)$ are
contained in the low-energy theorem for $\Gamma^{\mu\nu}$, i.e., no new
parameters appear.
  We discuss the leading terms of the matrix element and comment on the use of
on-shell equivalent electromagnetic vertices in the calculation of ``Born
terms'' for virtual Compton scattering.


title:
Virtual Compton Scattering and Generalized Polarizabilities of the
  Proton

abstract:
  Threshold photon electroproduction off the proton allows one to measure new
electromagnetic observables which generalise the usual polarisabilities. There
are -- a priori -- ten "generalised polarisabilities", functions of the virtual
photon mass. The purpose of this paper is to lay down the appropriate formalism
to extract these quantities from the photon electroproduction cross sections.
We also give a first estimate of the generalised polarisabilities in the non
relativistic quark model.


title:
Virtual Compton Scattering from the Proton and the Properties of Nucleon
  Excited States

abstract:
  We calculate the $N^*$ contributions to the generalized polarizabilities of
the proton in virtual Compton scattering. The following nucleon excitations are
included: $N^*(1535)$, $N^*(1650)$, $N^*(1520)$, $N^*(1700)$, $\Delta(1232)$,
$\Delta^*(1620)$ and $\Delta^*(1700)$. The relationship between nucleon
structure parameters, $N^*$ properties and the generalized polarizabilities of
the proton is illustrated.


title:
Nuclear halo effects in neutron-capture reactions of astrophysical
  interest

abstract:
  The halo effect in the final states of astrophysically relevant direct
neutron--capture reactions by neutron--rich nuclei is discussed. As an example,
we calculate the cross sections for $^{18}$O(n,$\gamma$)$^{19}$O at
thermonuclear and thermal energies.


title:
Microscopic description of Gamow-Teller transitions in middle pf--shell
  nuclei by a realistic shell model calculation

abstract:
  GT transitions in $N=28\sim 30$ nuclei are studied in terms of a large-scale
realistic shell-model calculation, by using Towner's microscopic parameters.
$B({\rm GT})$ values to low-lying final states are reproduced with a reasonable
accuracy. Several gross properties with respect to the GT transitions are
investigated with this set of the wavefunctions and the operator. While the
calculated total GT$^-$ strengths show no apparent disagreement with the
measured ones, the calculated total GT$^+$ strengths are somewhat larger than
those obtained from charge-exchange experiments. Concerning the Ikeda sum-rule,
the proportionality of $S_{\rm GT}$ to $(N-Z)$ persists to an excellent
approximation, with a quenching factor of 0.68. For the relative GT$^-$
strengths among possible isospin components, the lowest isospin component
gathers greater fraction than expected by the squared CG coefficients of the
isospin coupling. It turns out that these relative strengths are insensitive to
the size of model space. Systematics of the summed $B({\rm GT})$ values are
discussed for each isospin component.


title: The nuclear binding and the EMC effect in the deuteron

abstract:
  Influence of the nuclear binding in the deuteron deep inelastic structure
function $F_2(x,Q^2)$ is investigated. The description is based on the
Bethe-Salpeter formalism in the ladder approximation and the operator product
expansion within an effective meson-nucleon theory. It is shown that the
binding in a fully relativistic treatment can be simply parametrised and its
origin can be understood in terms of conventional nuclear degrees of freedom. A
numerical estimate of the EMC effect in the deuteron is given.


title: Probing hadron structure by real and virtual photons

abstract:
  The importance of subnuclear degrees of freedom in photon absorption and
electron scattering by nuclei is discussed. After a short introduction into the
basic properties of one-photon processes and a very brief survey on the nuclear
response in the various regions of energy and momentum transfers, the
particular role of subnuclear degrees of freedom in terms of meson and isobar
degrees of freedom is considered. Their importance is illustrated by several
reactions on the deuteron which are currently under study at c.w.\ electron
machines like MAMI in Mainz.


title:
A Relativistic Thomas-Fermi Description of Collective Modes in Droplets
  of Nuclear Matter

abstract:
  Isoscalar collective modes in a relativistic meson-nucleon system are
investigated in the framework of the time-dependent Thomas-Fermi method. The
energies of the collective modes are determined by solving consistently the
dispersion relations and the boundary conditions. The energy weighted sum rule
satisfied by the model allows the identification of the giant ressonances. The
percentage of the energy weighted sum rule exhausted by the collective modes is
in agreement with experimental data, but the energies come too high.


title:
Properties of nuclear matter in cut-off field theory and renormalization
  group methods

abstract:
  The properties of nuclear matter are studied in the cut-off field theory. It
is found that, under the Hartree approximation, the small cut-off makes the
equations of state hard, especially at higher densities. The theory is modified
in the framework of the renormalization group methods with arbitrary cut-off
$\Lambda^\prime$. It is found that the expansion in terms of the $\sigma$ meson
field is more favorable than the naive expansion of the inverse of
$\Lambda^\prime$, when we do not use very large $\Lambda^\prime$.


title:
Strangeness and Metastable Neutron Stars: What Might have Happened to
  SN1987A

abstract:
  Immediately after they are born, neutron stars are characterized by an
entropy per baryon of order unity and by the presence of trapped neutrinos. If
the only hadrons in the star are nucleons, these effects slightly reduce the
maximum mass relative to cold, catalyzed matter. However, if negatively charged
particles in the form of hyperons, a kaon condensate, or quarks are also
present, these effects result in an increase in the maximum mass of $\sim
0.2{\rm M}_{\odot}$ compared to that of a cold, neutrino-free star. This could
lead to the delayed formation of a black hole; such a scenario is consistent
with our present knowledge of SN1987A.


title: On the $\alpha-$decay of deformed actinide nuclei

abstract:
  $\alpha-$decay through a deformed potential barrier produces significant
mixing of angular momenta when mapped from the nuclear interior to the outside.
Using experimental branching ratios and either semi-classical or
coupled-channels transmission matrices, we have found that there is a set of
internal amplitudes which are essentially constant for all even--even actinide
nuclei. These same amplitudes also give good results for the known anisotropic
$\alpha-$particle emission of the favored decays of odd nuclei in the same mass
region.
  PACS numbers: 23.60.+e, 24.10.Eq, 27.90.+b


title: Two-pion exchange potential and the $\pi N$ amplitude

abstract:
  We discuss the two-pion exchange potential which emerges from a box diagram
with one nucleon (the spectator) restricted to its mass shell, and the other
nucleon line replaced by a subtracted, covariant $\pi N$ scattering amplitude
which includes $\Delta$, Roper, and $D_{13}$ isobars, as well as contact terms
and off-shell (non-pole) dressed nucleon terms. The $\pi N$ amplitude satisfies
chiral symmetry constraints and fits $\pi N$ data below $\sim$ 700 MeV pion
energy. We find that this TPE potential can be well approximated by the
exchange of an effective sigma and delta meson, with parameters close to the
ones used in one-boson-exchange models that fit $NN$ data below the pion
production threshold.


title: Effects of Strong Interaction on the Electromagnetic Dissociation

abstract:
  We investigate effects of strong interactions on the electromagnetic
dissociation of nuclei in heavy ion collisions. We start from the eikonal
approach to the equivalent photon method to describe the electromagnetic
contributions to the cross section of peripheral collisions. We summarize some
results of this approach and characterize recent experiments in "universal
plots". In the second part of this work, we give a straight forward method to
include transitions induced by the strong interactions between the ions. We
introduce different methods to obtain the nuclear transition potential, and
study the behavior of the resulting nuclear contributions.


title: Photoinduced two-proton knockout and ground-state correlations in nuclei

abstract:
  A factorized and analytical form for the A($\gamma$,pp) and A(e,e$'$pp) cross
section is proposed. In the suggested scheme the two-proton knockout cross
sections can be directly analyzed in terms of the ground-state correlation
functions. Central, spin-spin and tensor correlations are considered. In the
longitudinal channel, the (e,e$'$pp) cross section is predicted to exhibit a
peculiar sensitivity to ground-state correlation effects.


title: Nucleus-Nucleus Collisions at Highest Energies

abstract:
  The microscopic phasespace approach URQMD is used to investigate the stopping
power and particle production in heavy systems at SPS and RHIC energies. This
framework bridges with one model consistently the entire available range of
energies from below SIS to CERN, even for the heaviest system Pb+Pb. URQMD is a
hadronic transport model based on the propagation of hadrons on classical
trajectories in the framework of Lorentz-invariant dynamics. It includes
secondary interactions e.g. annihilation of produced mesons leading to the
formation of resonances and the excitation of strings. The collision term
contains 50 different baryon species (including nucleon, delta and hyperon
resonances with masses up to 2 GeV) and 25 different meson species (including
strange meson resonances), which are supplemented by their corresponding
antiparticle and all isospin-projected states. Within this approach we find no
gap in the baryon rapidity distribution even at RHIC. For CERN (SPS) energies
URQMD shows a pile up of baryons and a supression of multi-nucleon clusters
(e.g. He) at midrapidity.


title:
Polarized Deep-Inelastic Scattering from Nuclei -- A Relativistic
  Approach

abstract:
  A covariant formulation of spin-dependent deep-inelastic scattering from
nuclei is presented. In the relativistic impulse approximation the inclusive
nuclear cross section is described in terms of the amplitude for forward,
virtual-photon scattering from an off-mass-shell nucleon. The general structure
of the off-shell nucleon hadronic tensor is derived, and the leading behavior
of the off-shell nucleon structure functions computed in the Bjorken limit. The
formalism, which is valid for nucleons bound inside nuclei with spin 1/2 or 1,
is applied to the case of the deuteron.


title:
Baryon Stopping and Strangeness Production in Ultra-Relativistic Heavy
  Ion Collisions

abstract:
  The stopping behaviour of baryons in massive heavy ion collisions (at SPS,
RHIC and LHC) is investigated within different microscopic models. At
SPS-energies the predictions range from full stopping to virtually total
transparency. Experimental data are indicating strong stopping. The initial
baryo-chemical potentials and temperatures at collider energies and their
impact on the formation probability of strange baryon clusters and strangelets
are discussed.


title: Nucleon-Antinucleon Interaction from the Skyrme Model

abstract:
  We calculate the nucleon-antinucleon static potential in the Skyrme model
using the product ansatz and including some finite $N_C$ (number of colors)
corrections. The mid and long range part of the spin-spin and tensor force are
correctly given in both iso-spin channels while the central interaction has
insufficient mid-range attraction. This is a well known problem of the product
ansatz that should be repaired with better Skyrme dynamics.


title: Theory of Weak Hypernuclear Decay

abstract:
  The weak nonmesonic decay of Lambda-hypernuclei is studied in the context of
a one-meson-exchange model. Predictions are made for the decay rate, p/n
stimulation ratio and the asymmetry in polarized hypernuclear decay.


title: Quenching of $1^+$ excitations in the double giant resonance

abstract:
  The electromagnetic excitation of the two-phonon isovector giant dipole
resonance in relativistic projectiles incident on heavy targets can be proceed
via several intermediate $1^-$ one-phonon giant resonance states. In two step
electric dipole transitions the population of $0^+$, $1^+$, and $2^+ $
two-phonon states are possible. We calculate the amplitude distribution of
$1^-$ excitations with an RPA formalism, and use it to calculate the
electromagnetic excitation of two-phonon states in second order perturbation
theory and coupled-channels. We show that a conspiracy between angular momentum
coupling and the strength of the electromagnetic fields suppresses
contributions of $1^+$ states to the total cross sections.


title: The CP-odd nucleon interaction and the value of T-violation in nuclei

abstract:
  The relations between the value of T- and P-violating correlations in neutron
scattering and different models of CP violation are discussed. It is shown that
a specific structure of CP-odd interactions gives the possibility to obtain the
essential information about CP-odd interaction at the quark-gluon level from
nuclear experimental data. The up-to-date estimations for CP- violating nucleon
coupling constants show that CP violation in neutron scattering is sensitive to
many models of CP violation.


title: Continuum study of deconfinement at finite temperature

abstract:
  Deconfinement and chiral symmetry restoration are explored in a confining,
renormalisable, Dyson-Schwinger equation model of two-flavour QCD. An order
parameter for deconfinement is introduced and used to establish that, in the
chiral limit, deconfinement and chiral symmetry restoration are coincident at
$T_c\approx 150\,$MeV. The transitions are second order and each has the same
critical exponent: $\beta\approx 0.3$. The deconfinement transition is found to
exhibit sensitivity to the current-quark mass. $f_\pi$ and $m_\pi$ change by no
more than 10\% for $T<0.7\,T_c$, however, as $T\to T_c$, thermal fluctuations
cause the pion bound state contribution to the four-point quark-antiquark
correlation function to disappear.


title: Neutron--Antineutron Oscillations at the Surface of Nuclei

abstract:
  We discuss some aspects of possible neutron--antineutron oscillations in
nuclei. The phenomenon occurs mostly at the surface of nuclei, and hence {\sl
i)} is not very sensitive to medium corrections and {\sl ii)} makes use of the
antinucleon-nucleus interaction in a region probed by experiments at CERN.


title:
Rescattering effects in coherent pion photoproduction on the deuteron in
  the $\Delta$ resonance region

abstract:
  Within a dynamical model, rescattering effects are studied in coherent pion
photoproduction on the deuteron in the $\Delta$(1232) resonance region. The
model consists of a system of coupled equations for the N$\Delta$, NN$\pi$ and
NN channels. Pion rescattering leads in general to a significant reduction of
total and differential cross sections resulting in a better description of
experimental data. Only a few polarization observables are sensitive to
rescattering effects. In particular $T_{20}$ allows an analysis of the reaction
mechanism for specific kinematics. The question how rescattering affects the
sensitivity to the E2 excitation of the $\Delta$ resonance is also studied.


title:
Meson-exchange Model for $\pi N$ scattering and $\gamma N -> \pi N$
  reaction

abstract:
  An effective Hamiltonian consisting of bare $\Delta \leftrightarrow\pi N$,
$\gamma N$ vertex interactions and energy-independent meson-exchange $\pi N
\leftrightarrow \pi N, \gamma N$ transition operators is derived by applying a
unitary transformation to a model Lagrangian with $N,\Delta,\pi$, $\rho$,
$\omega$, and $\gamma$ fields. With appropraite phenomenological form factors
and coupling constants for $\rho$ and $\Delta$, the model can give a good
description of $\pi N$ scattering phase shifts up to the $\Delta$ excitation
energy region. It is shown that the best reproduction of the recent LEGS data
of the photon-asymmetry ratios in $\gamma p \rightarrow \pi ^0 p$ reactions
provides rather restricted constraints on the coupling strengths $G_E$ of the
electric $E2$ and $G_M$ of the magnetic $M1$ transitions of the bare $\Delta
\leftrightarrow \gamma N$ vertex and the less well-determined coupling constant
$g_{\omega NN}$ of $\omega$ meson. Within the ranges that $G_M = 1.9 \pm 0.05$,
$G_E = 0.0 \pm 0.025$, and $7 \leq g_{\omega NN}\leq 10.5$, the predicted
differential cross sections and photon-asymmetry ratios are in an overall good
agreement with the data of $\gamma p \rightarrow \pi ^0 p$, $\gamma p
\rightarrow \pi ^+ n$, and $\gamma n\rightarrow \pi ^- p$ reactions from 180
MeV to the $\Delta$ excitation region. The predicted $M_{1^+}$ and $E_{1^+}$
multipole amplitudes are also in good agreement with the empirical values
determined by the amplitude analyses. The constructed effective Hamiltonian is
free of the nucleon renormlization problem and hence is suitable for nuclear
many-body calculations. We have also shown that the assumptions made in the
$K$-matrix method, commonly used in extracting empirically the $\gamma N
\rightarrow \Delta$ transition amplitudes from the data, are consistent with


title:
Interplay of Interference Effects in Production of $J/\Psi$ and $\Psi'$
  off Nuclei

abstract:
  Our main observations are: (i) The effective path length of the $c\bar c$
wave packet, which is produced in the nucleus, grows with the energy of the
produced charmonium. The variation is controlled by the coherence length
$l_c=2E_{\Psi}/M^2_{\Psi}$. (ii) A colorless $c\bar c$ wave packet produced in
$pp$-interaction is a specific linear combination of the $J/\Psi$ and $\Psi'$
states, and interacts substantially weaker that any of its components. The time
evolution of this wave packet is controlled by the formation length,
$l_f=2E_{\Psi}/(M^2_{\Psi'} - M^2_{\Psi})$. Exact formulas incorporating with
these effects are derived. The interplay of the two phenomena results in a
nontrivial energy- and $x_F$-dependence of the nuclear suppression of the
charmonium production in proton-nucleus and nucleus-nucleus collisions and
explains some of the experimentally observed effects.


title:
Multiple electromagnetic electron positron pair production in
  relativistic heavy ion collisions

abstract:
  We calculate the cross sections for the production of one and more
electron-positron pairs due to the strong electromagnetic fields in
relativistic heavy ion collisions. Using the generating functional of fermions
in an external field we derive the N-pair amplitude. Neglecting the
antisymmetrisation in the final state we find that the total probability to
produce N pairs is a Poisson distribution. We calculate total cross sections
for the production of one pair in lowest order and also include higher-order
corrections from the Poisson distribution up to third order. Furthermore we
calculate cross sections for the production of up to five pairs including
corrections from the Poisson distribution.


title: Perturbation of Embedded Eigenvalue by a Near-Lying Resonance

abstract:
  The case of quantum-mechanical system (including electronic molecules) is
considered where Hamiltonian allows a separation, in particular by the Faddeev
method, of a weakly coupled channel. Width (i.e. the imaginary part) of the
resonance generated by a discrete spectrum eigenvalue of the separated channel
is studied in the case where main part of the Hamiltonian gives itself another
resonance. It is shown that if real parts of these resonances coincide and, at
the same time, a coupling between the separated and main channels is
sufficiently small then the width of the resonance generated by the separated
(molecular) channel is inversely proportional to the width of the main
(nuclear) channel resonance. This phenomenon being a kind of universal law, may
play an important role increasing the ``cold fusion'' probability in electronic
molecules whose nuclear constituents have narrow pre-threshold resonances.


title:
Influence of the pion-nucleon interaction on the collective pion flow in
  heavy ion reactions

abstract:
  We investigate the influence of the real part of the in-medium pion optical
potential on the pion dynamics in intermediate energy heavy ion reactions at 1
GeV/A. For different models, i.e. a phenomenological model and the
$\Delta$--hole model, a pionic potential is extracted from the dispersion
relation and used in Quantum Molecular Dynamics calculations. In addition with
the inelastic scattering processes we thus take care of both, real and
imaginary part of the pion optical potential. A strong influence of the real
pionic potential on the pion in-plane flow is observed. In general such a
potential has the tendency to reduce the anticorrelation of pion and nucleon
flow in non-central collisions.


title:
Phase Transition in Warm Nuclear Matter with Alternative Derivative
  Coupling Models

abstract:
  An analysis is performed of the liquid-gas phase transition of nuclear matter
obtained from different versions of scalar derivate coupling suggested by
Zimanyi and Moszkowski (ZM) and the results are compared with those obtained
from the Walecka model. We present the phase diagram for the models and one of
them, the ZM3 model, has the lowest critical temperature $T_c=13.6$ MeV with
the lowest critical density $\rho_c=0.037$ f$m^{-3}$ and pressure $p_c=0.157$
MeV f$m^{-3}$.
  These results are in accord with recent observations from energetic heavy-ion
collisions, which suggest a small liquid-gas phase region.


title:
Unitary ambiguity in the extraction of the E2/M1 ratio for the $\gamma
  N\leftrightarrow\Delta$ transition

abstract:
  The resonant electric quadrupole amplitude in the transition $\gamma
N\leftrightarrow\Delta(1232)$ is of great interest for the understanding of
baryon structure. Various dynamical models have been developed to extract it
from the corresponding photoproduction multipole of pions on nucleons. It is
shown that once such a model is specified, a whole class of unitarily
equivalent models can be constructed, all of them providing exactly the same
fit to the experimental data. However, they may predict quite different
resonant amplitudes. Therefore, the extraction of the E2/M1($\gamma
N\leftrightarrow\Delta$) ratio (bare or dressed) which is based on a dynamical
model using a largely phenomenological $\pi N$ interaction is not unique.


title: Quasifree pion photoproduction on the deuteron in the $\Delta$ region

abstract:
  Photo production of pions on the deuteron is studied in the spectator nucleon
model. The Born terms of the elementary production amplitude are determined in
pseudovector $\pi$N coupling and supplied with a form factor. The $\Delta$
resonance is considered both in the $s$ and the $u$ channel. The parameters of
the $\Delta$ resonance and the cutoff of the form factors are fixed on the
leading photoproduction multipoles. Results for total and differential cross
sections are compared with experimental data. Particular attention is paid to
the role of Pauli correlations of the final state nucleons in the quasifree
case. The results are compared with those for pion photoproduction on the
nucleon.


title:
Probing the Phase Boundary between Hadronic Matter and the
  Quark-Gluon-Plasma in Relativistic Heavy Ion Collisions

abstract:
  We discuss recent data on particle production with emphasis on the degree of
thermal and chemical equilibration achieved. The data are interpreted in terms
of a resonance gas model. The phase boundary constructed between the resonance
gas and the quark-gluon plasma is shown to be very close to the deduced
parameters characterizing the hadronic fireball at freeze-out.


title: A New Microscopic Approach to the Rotational Intensity Relations

abstract:
  The intensity relations for electromagnetic transition rates in the
rotational coupling scheme have been a basic tool to understand the properties
of nuclear collective rotations. In particular the correction terms to the
leading-order relation give the response of the intrinsic motion to the
Coriolis and centrifugal forces. We propose a simple and systematic method to
calculate the matrix elements of intrinsic operators entering the generalized
intensity relations that uses the microscopic cranking formalism. Examples are
given to show the usefulness of the method.


title:
Quasi-gaussian fixed points and factorial cumulants in nuclear
  multifragmentation

abstract:
  We re-analyze the conditions for the phenomenon of intermittency
(self-similar fluctuations) to occur in models of multifragmentation. Analyzing
two different mechanisms, the bond-percolation and the ERW (Elattari, Richert
and Wagner) statistical fragmentation models, we point out a common
quasi-gaussian shape of the total multiplicity distribution in the critical
range. The fixed-point property is also observed for the multiplicity of the
second bin. Fluctuations are studied using scaled factorial cumulants instead
of scaled factorial moments. The second-order cumulant displays the
intermittency signal while higher order cumulants are equal to zero, revealing
a large information redundancy in scaled factorial moments. A practical
criterion is proposed to identify the gaussian feature of light-fragment
production, distinguishing between a self-similarity mechanism (ERW) and the
superposition of independent sources (percolation).


title:
Self-consistent description of finite nuclei based on a relativistic
  quark model

abstract:
  Relativistic Hartree equations for spherical nuclei have been derived from a
relativistic quark model of the structure of bound nucleons which interact
through the (self-consistent) exchange of scalar ($\sigma$) and vector
($\omega$ and $\rho$) mesons. The coupling constants and the mass of the
$\sigma$-meson are determined from the properties of symmetric nuclear matter
and the rms charge radius in $^{40}$Ca. Calculated properties of static,
closed-shell nuclei from $^{16}$O to $^{208}$Pb are compared with experimental
data and with results of Quantum Hadrodynamics (QHD). The dependence of the
results on the nucleon size and the quark mass is investigated. Several
possible extensions of the model are also discussed.


title: The exclusive (e,e$'$p) reaction at high missing momenta

abstract:
  The reduced (e,e$'$p) cross section is calculated for kinematics that probe
high missing momenta. The final-state interaction is handled within a
non-relativistic many-body framework. One- and two-body nuclear currents are
included. Electron distortion effects are treated in an exact distorted wave
calculation. It is shown that at high missing momenta the calculated (e,e$'$p)
cross sections exhibit a pronounced sensitivity to ground-state correlations of
the RPA type and two-body currents. The role of these mechanisms is found to be
relatively small at low missing momenta.


title: Few-Body Quantum Problem in the Boundary-Condition Model

abstract:
  Systems of three and four quantum particles in the boundary-condition model
are considered. The Faddeev-Yakubovsky approach is applied to construct the
Fredholm-type integral equations for these systems in framework of the
Potential theory. The boundary-value problems are formulated for the
Faddeev-Yakubovsky components of wave functions.


title:
Realistic shell model calculation of $2\nu\beta\beta$ nuclear matrix
  elements and role of shell structure in intermediate states

abstract:
  We discuss two conditions needed for correct computation of $2\nu \beta\beta$
nuclear matrix-elements within the realistic shell-model framework. An
algorithm in which intermediate states are treated based on Whitehead's moment
method is inspected, by taking examples of the double GT$^+$ transitions
$\mbox{$^{36}$Ar}\rightarrow\mbox{$^{36}$S}$,
$\mbox{$^{54}$Fe}\rightarrow\mbox{$^{54}$Cr}$ and $\mbox{$^{58}$Ni}
\rightarrow\mbox{$^{58}$Fe}$. This algorithm yields rapid convergence on the
$2\nu\beta\beta$ matrix-elements, even when neither relevant GT$^+$ nor GT$^-$
strength distribution is convergent. A significant role of the shell structure
is pointed out, which makes the $2\nu\beta \beta$ matrix-elements highly
dominated by the low-lying intermediate states. Experimental information of the
low-lying GT$^\pm$ strengths is strongly desired. Half-lives of
$T^{2\nu}_{1/2}({\rm EC}/{\rm EC};
\mbox{$^{36}$Ar}\rightarrow\mbox{$^{36}$S})=1.7\times 10^{29}\mbox{yr}$,
$T^{2\nu}_{1/2}({\rm EC}/{\rm EC};\mbox{$^{54}$Fe}\rightarrow
\mbox{$^{54}$Cr})=1.5\times 10^{27}\mbox{yr}$,$T^{2\nu}_{1/2}({\rm EC} /{\rm
EC};\mbox{$^{58}$Ni}\rightarrow\mbox{$^{58}$Fe})=6.1\times 10^{24}\mbox{yr}$and
$T^{2\nu}_{1/2}(\beta^+/{\rm EC};\mbox{$^{58}$Ni}
\rightarrow\mbox{$^{58}$Fe})=8.6\times 10^{25}\mbox{yr}$ are obtained from the
present realistic shell-model calculation of the nuclear matrix-elements.


title: Electromagnetic Production of Kaons on the Nucleon

abstract:
  Kaon photo- and electroproduction in all six isospin channels are
investigated by means of an isobaric model. It is found that existing models
can only partially describe the current experimental data. Moreover, the
extracted coupling constants are mostly inconsistent with the prediction of
SU(3) symmetry or the information from hadronic reactions. In order to further
analyze this problem, we introduce a form factor at the hadronic vertices $KNY$
(with $Y=\Lambda~ \textrm{or}~ \Sigma$) and study its behavior qualitatively.
Our result suggests the need of more accurate experiments, especially in the
charged $\Sigma$ and the neutral $K^0$ channels.


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

abstract:
  The quark-meson coupling (QMC) model for nuclear matter, which describes
nuclear matter as non-overlapping MIT bags bound by the self-consistent
exchange of scalar and vector mesons is modified by the introduction of a
density dependent bag constant. It is found that when the bag constant is
significantly reduced in nuclear medium with respect to its free space value,
large canceling isoscalar Lorentz scalar and vector potentials for the nucleon
in nuclear matter emerge naturally. Such potentials are comparable to those
suggested by relativistic nuclear phenomenology. This suggests that the
modification of the bag constant in the nuclear medium may play an important
role in low- and medium-energy nuclear physics.


title: New QCD Sum Rules for Nucleon Axial Vector Coupling Constants

abstract:
  New QCD sum rules for the nucleon axial-vector current coupling constants are
derived. One set is derived from a generalized correlator of spin-1/2
interpolating fields, and the other with a mixed correlator of spin-1/2 and
spin-3/2 fields. Using a recently-developed Monte-Carlo based uncertainty
analysis and techniques for determining the optimal interpolating fields, the
predicative ability of QCD sum rules for axial-vector current coupling
constants are determined. We find the previous studies of this matrix element
are based on an invalid sum rule. A combined analysis of this sum rule together
with the nucleon mass sum rules yields $g_A=1.48\pm^{1.06}_{0.65}$. The
relative error of approximately 60% is large compared to a 10% error for the
nucleon mass obtained from the same input parameters.


title: Dynamics of Strangeness Production and Strange Matter Formation

abstract:
  The dynamics of a hadronizing quark matter drop is investigated with a
hybrid-like model, which takes into account equilibrium as well as
non-equilibrium features of the process. We study the the particle rates from
the hadronizing plasma, which have to be put in relation to the whole time
evolution of the system. The impact of finite-size effects on the distillation
process is considered. $H^0$-Dibaryon yields are estimated. Microscopic
calculations of hypercluster formation at AGS and SPS are presented.


title: Dilepton Production at SPS-energy Heavy Ion Collisions

abstract:
  The production of dileptons is studied within a hadronic transport model. We
investigate the sensitivity of the dilepton spectra to the initial
configuration of the hadronic phase in a ultrarelativistic heavy ion collision.
Possible in medium correction due to the modifications of pions and the pion
form factor in a hadronic gas are discussed.


title: Exotic Decays of Strangelets

abstract:
  The stability of strange matter depends on the implicit assumption that
baryon number is conserved. We examine the relevant effective operators which
allow strangelets to decay by violating the conservation of baryon number. From
the experimental lower limit of 10$^{25}$ years on the stability of nuclei, we
find a lower limit of the order 10$^6$ years on the stability of strangelets
against such exotic decays.


title:
Extracting the equation of state from a microscopic non-equilibrium
  model

abstract:
  We study the thermodynamic properties of infinite nuclear matter with the
Ultrarelativistic Quantum Molecular Dynamics (URQMD), a semiclassical transport
model, running in a box with periodic boundary conditions. It appears that the
energy density rises faster than $T^4$ at high temperatures of $T\approx
200-300$~MeV. This indicates an increase in the number of degrees of freedom.
Moreover, We have calculated direct photon production in Pb+Pb collisions at
160~GeV/u within this model. The direct photon slope from the microscopic
calculation equals that from a hydrodynamical calculation without a phase
transition in the equation of state of the photon source.


title: Neutrino induced transitions between the ground states of the A=12 triad

abstract:
  Neutrino induced reactions on $^{12}$C, an ingredient of liquid
scintillators, have been studied in several experiments. We show that for
currently available neutrino energies, $E_{\nu} \le$ 300 MeV, calculated
exclusive cross sections $^{12}$C$_{gs}(\nu,l)$$^{12}$N$_{gs}$ for both muon
and electron neutrinos are essentially model independent, provided the
calculations simultaneously describe the rates of several other reactions
involving the same states or their isobar analogs. The calculations agree well
with the measured cross sections, which can be therefore used to check the
normalization of the incident neutrino spectrum and the efficiency of the
detector.


title: Nonlinearities of the Vlasov equation in the spinodal region

abstract:
  We estimate the importance of the nonlinear terms in the Vlasov equation for
the development of the unstable modes. The results allow to identify the region
of wavelength where the linear evolution is justified.


title: Anisotropic Transverse Flow and the HBT Correlation Function

abstract:
  Utilizing the Lorentz invariance of the correlation function we study the
effects of anisotropic transverse flow on the HBT correlation function. In
particular we show that directed flow would evidence itself by non zero
``side--long'' and ``side--out'' terms in the correlation function. We also
show that the study of ratios of the correlation functions evaluated on
different event subsamples and/or different Lorentz systems provides
information on the source dimensions and velocity which could be less biased by
corrections of different kinds. We present a fitting technique appropriate for
HBT analysis which does not require binning and is especially useful for
multidimensional fitting.


title:
On the Extraction of the Neutron Spin Structure Functions and the
  Gerasimov -- Drell -- Hearn Integral from $^3\vec {He}(\vec e, e')X$ data

abstract:
  Nuclear effects in polarized inelastic electron scattering off polarized
$^3He$ are discussed; in the kinematics of future experiments at CEBAF, Fermi
motion effects are found to be much larger than in deep inelastic scattering.
It is shown that improperly describing nuclear dynamics would lead to the
extraction of unreliable neutron spin structure functions. On the other hand
side, a simple and workable equation relating the Gerasimov -- Drell -- Hearn
Integral for the neutron to the corresponding quantity for $^3He$ is proposed.


title:
Can we learn anything new from polarization observables of the deuteron
  disintegration near threshold?

abstract:
  We discuss polarization characteristics of the deuteron disintegration near
the threshold energy. Due to the small relative energy of the outgoing $np$
pair, the dominant amplitude for this process is a 1+ -> 0^+ transition.
Relativistic covariance requires only one electromagnetic transition form
factor for this amplitude. Subsequently this leads to substantial
simplifications in the formulas of the polarization observables and allows to
draw conclusions independent of the details of the interaction.


title: Mass and width of the $d'$ resonance in nuclei

abstract:
  We calculated the mass and width of the $d'$ resonance inside nuclei within a
nucleon-$\Delta$ model by including the self-energy of the $\Delta$ in the
$N\Delta$ propagator. We found that in the nuclear medium the width of the $d'$
is increased by one order of magnitude while its mass changes only by a few
MeV. This broadening of the width of the $d'$ resonance embedded in nuclei is
consistent with the experimental observations so that the $d'$ can be
understood as a $N\Delta$ resonance. Thus, given the freedom between either
isospin 0 or isospin 2 for the $d'$, our results give weigth to the isospin-2
assignment.


title: The Multichannel Quark Model

abstract:
  We discuss the non-relativistic multichannel quark model and describe the
techniques developed to solve the resulting equations. We then investigate some
simple solutions to demonstrate how the model unifies meson-meson scattering
with meson spectroscopy, thereby greatly extending the domain of applicability
of the naive quark model. In the limits of narrow resonance widths and no quark
exchange, it reproduces the standard quark model spectroscopy and Breit-Wigner
phase description. Outside those limits s-channel resonance masses are lowered
by their two-meson couplings, the line-shapes of wide resonances are
significantly altered, and the equivalent Breit-Wigner masses and widths show
an energy dependence. Because meson-meson interactions are due to coherent
s-channel resonance production and t-channel quark exchange (though other
interactions can readily be added), the multichannel equations model
experimental resonance production and decay in a way that the usual eigenvalue
equations cannot.


title: Strong Pionic Decays From a Spectroscopic Quark Model

abstract:
  From a refined non-relativistic quark model that fits the baryonic low-energy
spectrum the study of strong pion decay processes within an elementary emission
model scheme points out the need of incorporating size-contributing components
into the baryon wave functions. In particular the effect of a (qqq qantiq)
component is investigated in the framework of a quark pair creation model.


title:
The Time-Delay Signature of Quark-Gluon-Plasma Formation in Relativistic
  Nuclear Collisions

abstract:
  The hydrodynamic expansion of quark-gluon plasmas with spherical and
longitudinally boost-invariant geometries is studied as a function of the
initial energy density. The sensitivity of the collective flow pattern to
uncertainties in the nuclear matter equation of state is explored. We
concentrate on the effect of a possible finite width, $\Delta T \sim 0.1 T_c$,
of the transition region between quark-gluon plasma and hadronic phase.
Although slow deflagration solutions that act to stall the expansion do not
exist for $\Delta T > 0.08 T_c$, we find, nevertheless, that the equation of
state remains sufficiently soft in the transition region to delay the
propagation of ordinary rarefaction waves for a considerable time. We compute
the dependence of the pion-interferometry correlation function on $\Delta T$,
since this is the most promising observable for time-delayed expansion. The
signature of time delay, proposed by Pratt and Bertsch, is an enhancement of
the ratio of the inverse width of the pion correlation function in
out-direction to that in side-direction. One of our main results is that this
generic signature of quark-gluon plasma formation is rather robust to the
uncertainties in the width of the transition region. Furthermore, for
longitudinal boost-invariant geometries, the signal is likely to be maximized
around RHIC energies, $\sqrt{s} \sim 200$ AGeV.


title: Validity of Certain Soft Photon Amplitudes

abstract:
  Certain soft photon amplitudes which have been recently suggested as
alternatives to the usual Low form of the soft photon approximation are studied
and it is demonstrated that problems exist in their relation to the
corresponding non-radiative amplitude. The non-radiative amplitude, which is an
input to soft photon calculations, is in certain cases required to be evaluated
outside of its physical phase space region. Also, for the case of two-body
identical particle bremsstrahlung processes, the symmetrized or antisymmetrized
form of these soft photon amplitudes cannot be written in terms of the
symmetrized or antisymmetrized amplitude for the non-radiative process. It is
found that the usual Low form of the soft photon theorem is essentially
unaffected by these problems.


title: Kaon Interferometry

abstract:
  Two-kaon and two-pion correlation functions for an expanding thermalized
source are compared. In the Yano-Koonin-Podgoretskii parametrization of the
correlation function, the HBT radius parameters are shown to obey M_\bot-
scaling in the absence of collective transverse flow. This scaling is broken by
transverse flow. An accurate comparison of pion and kaon correlations can thus
resolve issue whether the observed M_\bot-dependence of the transverse radius
parameter is due to transverse collective flow or other transverse gradients.
Effects from resonance decays are shortly discussed.


title:
Pseudoscalar meson photoproduction: from known to undiscovered
  resonances

abstract:
  The role of dynamics in spin observables for pseudoscalar meson
photoproduction is investigated using a density matrix approach in a multipole
truncated framework. Extraction of novel rules for $\gamma p \rightarrow \pi^+
n,~ K^+ \Lambda$ and $\eta p$ reactions based on resonance dominance, and on
other broad and reasonable dynamical assumptions, are discussed. Observables
that are particularly sensitive to missing nucleonic resonances predicted by
quark-based approaches, are singled out.


title: Boson-fermion mapping and dynamical supersymmetry in fermion models

abstract:
  We show that a dynamical supersymmetry can appear in a purely fermionic
system. This ``supersymmetry without bosons" is constructed by application of a
recently introduced boson-fermion Dyson mapping from a fermion space to a space
comprised of collective bosons and ideal fermions. In some algebraic fermion
models of nuclear structure, particular Hamiltonians may lead to collective
spectra of even and odd nuclei that can be unified using the dynamical
supersymmetry concept with Pauli correlations exactly taken into account.


title:
Regularization, Renormalization and Range: The Nucleon-Nucleon
  Interaction from Effective Field Theory

abstract:
  Regularization and renormalization is discussed in the context of low-energy
effective field theory treatments of two or more heavy particles (such as
nucleons). It is desirable to regulate the contact interactions from the outset
by treating them as having a finite range. The low energy physical observables
should be insensitive to this range provided that the range is of a similar or
greater scale than that of the interaction. Alternative schemes, such as
dimensional regularization, lead to paradoxical conclusions such as the
impossibility of repulsive interactions for truly low energy effective theories
where all of the exchange particles are integrated out. This difficulty arises
because a nonrelativistic field theory with repulsive contact interactions is
trivial in the sense that the $S$ matrix is unity and the renormalized coupling
constant zero. Possible consequences of low energy attraction are also
discussed. It is argued that in the case of large or small scattering lengths,
the region of validity of effective field theory expansion is much larger if
the contact interactions are given a finite range from the beginning.


title:
Transverse Shocks in the Turbulent Gluon Plasma Produced in
  Ultra-Relativistic A+A

abstract:
  Mini-jet production in ultra-relativistic nuclear collisions leads to initial
conditions characterized by large fluctuations of the local energy density (hot
spots) and of the collective flow field (turbulence). Assuming that local
equilibrium is reached on a small time scale, $\sim 0.5$ fm/c, the transverse
evolution of those initial conditions is computed using hydrodynamics. We find
that a new class of collective flow phenomena (hadronic volcanoes) could arise
under such conditions. This could be observable via enhanced azimuthal
fluctuations of the transverse energy flow, $d^2E_\perp/d\phi dy$.


title:
The Isovector Quadrupole-Quadrupole Interaction Used in Shell Model
  Calculations with $\Delta N=2$ Excitations

abstract:
  The effect of the ``$B$'' term in the interaction $-\chi Q\cdot
Q(1+B\vec{\tau}(1)\cdot \vec{\tau}(2))$, which was previously considered in the
$0p$ shell, is now studied in a larger space which includes $\Delta N=2$
excitations. We still get a collapse of low-lying states below the conventional
$J=0^+$ ground state when $B$ is made sufficiently negative.


title: Triton Binding Energy and Minimal Relativity

abstract:
  For relativistic three-body calculations, essentially two different
approaches are in use: field theory and relativistic direct interactions.
Results for relativistic corrections of the triton binding energy obtained from
the two approaches differ even in their sign, which is rather puzzling. In this
paper, we discuss the origin of such discrepancy. We show that the use of an
invariant two-body amplitude, as done in the field-theoretic approach,
increases the triton binding energy by about 0.30 MeV. This may explain a large
part of the discrepancy.


title:
Superdeformed Bands of Odd Nuclei in A=190 Region in the Quasiparticle
  Picture

abstract:
  We study the properties of the superdeformed (SD) bands of 195Pb and 193Hg by
the cranked Hartree-Fock-Bogoliubov method. Our calculations reproduce the flat
behavior of the dynamical moment of inertia of two of the SD bands of 195Pb
measured recently. We discuss possible configuration assignments for the
observed bands 3 and 4 of 195Pb. We also calculate the two interacting SD bands
of 193Hg. Our analysis confirms the superiority of a density-dependent pairing
force over a seniority pairing interaction.


title: Partial Dynamical Symmetry in Deformed Nuclei

abstract:
  We discuss the notion of partial dynamical symmetry in relation to nuclear
spectroscopy. Explicit forms of Hamiltonians with partial $SU(3)$ symmetry are
presented in the framework of the interacting boson model of nuclei. An
analysis of the resulting spectrum and electromagnetic transitions demonstrates
the relevance of such partial symmetry to the spectroscopy of axially deformed
nuclei.


title:
Density dependence of resonance broadening and shadowing effects in
  nuclear photoabsorption

abstract:
  Medium effects as a function of the mass number $A$ are studied in the total
photonuclear cross section from the $\Delta$-resonance region up to the region
where shadowing effects are known to exist. A consistent picture is obtained by
simply assuming a density dependence of the different mechanisms of resonance
broadening and shadowing. The $\Delta$-mass shift is found to increase with
$A$.


title:
Virtual Compton Scattering and Generalized Polarizabilities of the
  Nucleon in Heavy Baryon Chiral Perturbation Theory

abstract:
  The spin-independent part of the virtual Compton scattering (VCS) amplitude
from the nucleon is calculated within the framework of heavy baryon chiral
perturbation theory (HBChPT). The calculation is performed to third order in
external momenta according to chiral power counting. The relation of the
tree-level amplitudes to what is expected from the low-energy theorem is
discussed. We relate the one-loop results to the structure coefficients of a
low-energy expansion for the model-dependent part of the VCS amplitude recently
defined by Fearing and Scherer. Finally we discuss the connection of our
results with the generalized polarizabilities of the nucleon defined by
Guichon, Liu and Thomas.


title:
Ambiguities in the partial-wave analysis of pseudoscalar-meson
  photoproduction

abstract:
  Ambiguities in pseudoscalar-meson photoproduction, arising from incomplete
experimental data, have analogs in pion-nucleon scattering. Amplitude
ambiguities have important implications for the problems of amplitude
extraction and resonance identification in partial-wave analysis. The effect of
these ambiguities on observables is described. We compare our results with
those found in earlier studies.


title:
The hadron-quark transition with a lattice of nonlocal confining
  solitons

abstract:
  We use a lattice of nonlocal confining solitons to describe nuclear matter in
the Wigner-Seitz approximation. The average density is varied by changing the
size of the Wigner-Seitz cell. At sufficiently large density quark energy bands
develop. The intersection of the filled valence band with the next empty band
at a few times standard nuclear density signals a transition from a color
insulator to a color conductor and is identified with the critical density for
quark deconfinement.


title: $\Delta I=1$ axial-vector mixing and charge symmetry breaking

abstract:
  Phenomenological Lagrangians that exhibit (broken) chiral symmetry as well as
isospin violation suggest short-range charge symmetry breaking (CSB)
nucleon-nucleon potentials with a $\mbox{\boldmath $\sigma$}_1
\!\cdot\!\mbox{\boldmath $\sigma$}_2$ structure. This structure could be
realized by the mixing of axial-vector ($1^+$) mesons in a single-meson
exchange picture. The Coleman-Glashow scheme for $\Delta I_{z}=1$ charge
symmetry breaking applied to meson and baryon $SU(2)$ mass splittings suggests
a universal scale. This scale can be extended to $\Delta I=1$ nonstrange CSB
transitions $\langle a_1^\circ|H_{em}|f_1\rangle$ of size $-0.005$ GeV$^2$. The
resulting nucleon-nucleon axial-vector meson exchange CSB potential then
predicts $\Delta I=1$ effects which are small.