title:
Molecular dynamics approach: from chaotic to statistical properties of
  compound nuclei

abstract:
  Statistical aspects of the dynamics of chaotic scattering in the classical
model of $\alpha$-cluster nuclei are studied. It is found that the dynamics
governed by hyperbolic instabilities which results in an exponential decay of
the survival probability evolves to a limiting energy distribution whose
density develops the Boltzmann form. The angular distribution of the
corresponding decay products shows symmetry with respect to $\pi/2$ angle. Time
estimated for the compound nucleus formation ranges within the order of
$10^{-21}$s.


title:
Hard Constituent Quarks and Electroweak Properties of Pseudoscalar
  Mesons

abstract:
  The high momentum components generated in the wave function of pseudoscalar
mes* by the one-gluon-exchange interaction are investigated within a
relativistic constituent quark model. Adopting the light-cone formalism, the
sensitivity of the weak decay constant and the charge form factor to hard
constituent quarks is illustrated.


title: Large Angle K+-Deuteron Scattering as a Probe for Meson Exchange Effects

abstract:
  Meson exchange contributions have been suggested as one class of medium
effects which might explain the continuing discrepancy between experimental
results and theoretical predictions for K+-nucleus scattering. These exchange
effects are negligible for near-forward K+-deuteron scattering because of the
large size of the deuteron, but at large angles they might be expected to be
significant compared to the weak double scattering. Detailed calculations,
however, show that the quadrupole and magnetic contributions from single
scattering are large enough to dominate both double scattering and exchange
contributions even at large momentum transfers. The exchange contributions
become significant only if the target deuteron is highly aligned so that the
single scattering contributions are greatly reduced.


title: Nuclear Magnetic Quadrupole Moments in Single Particle Approximation

abstract:
  A static magnetic quadrupole moment of a nucleus, induced by T- and P-odd
nucleon-nucleon interaction, is investigated in the single-particle
approximation. Models are considered allowing for analytical solution. The
problem is also treated numerically in a Woods-Saxon potential with spin-orbit
interaction. The stability of results is discussed.


title: Collective Flow from the Intranuclear Cascade Model

abstract:
  The phenomenon of collective flow in relativistic heavy ion collisions is
studied using the hadronic cascade model ARC. Direct comparison is made to data
gathered at the Bevalac, for Au+Au at $p=1-2$ GeV/c. In contrast to the
standard lore about the cascade model, collective flow is well described
quantitatively without the need for explicit mean field terms to simulate the
nuclear equation of state. Pion collective flow is in the opposite direction to
nucleon flow as is that of anti-nucleons and other produced particles. Pion and
nucleon flow are predicted at AGS energies also, where, in light of the higher
baryon densities achieved, we speculate that equation of state effects may be
observable.


title: Large-space shell-model calculations for light nuclei

abstract:
  An effective two-body interaction is constructed from a new Reid-like $NN$
potential for a large no-core space consisting of six major shells and is used
to generate the shell-model properties for light nuclei from $A$=2 to 6. (For
practical reasons, the model space is partially truncated for $A$=6.) Binding
energies and other physical observables are calculated and compare favorably
with experiment.


title:
Model for asymptotic $D$-state parameters of light nuclei: Application
  to $^4He$

abstract:
  A simple method for calculating the asymptotic $D$ state observables for
light nuclei is suggested. The method exploits the dominant clusters of the
light nuclei. The method is applied to calculate the $^4He$ asymptotic $D$ to
$S$ normalization ratio $\rho^\alpha$ and the closely related $D$ state
parameter $D_2^\alpha$. The study predicts a correlation between $D_2^\alpha$
and $B_\alpha$, and between $\rho^\alpha$ and $B_\alpha$, where $B_\alpha$ is
the binding energy of $^4He$. The present study yields $\rho^\alpha \simeq
-0.14$ and $D_2^\alpha \simeq -0.12$ fm$^2$ consistent with the correct
experimental $\eta^D$ and the binding energies of the deuteron, triton, and the
$\alpha$ particle, where $\eta^d$ is the deuteron $D$ state to $S$ state
normalization ratio.


title: Laboratory Mesurements in Nuclear Astrophysics

abstract:
  After reviewing some of the basic concepts, nomenclatures and
parametrizations of Astronomy, Astrophysics and Cosmology, we introduce a few
central problems in Nuclear Astrophysics, including the hot-CNO cycle, helium
burning in massive stars, and solar neutrino's. We demonstarte that SECONDARY
(RADIOACTIVE) NUCLEAR BEAMS allow for considerable progress on these problems.


title: Boson-fermion Dyson mapping and supersymmetry in fermion systems

abstract:
  We demonstrate that exact supersymmetry can emerge in a purely fermionic
system. This "supersymmetry without bosons" is unveiled by constructing a novel
boson-fermion Dyson mapping from a fermion space to a space comprised of
collective bosons and ideal fermions. In a nuclear structure context the
collective spectra of even and odd nuclei can then be unified in a
supersymmetric description with Pauli correlations still exactly taken into
account.


title: Cold Kaons from Hot Fireballs

abstract:
  The E814-collaboration has found a component of very low $m_t$ $K^+$ mesons
with a slope parameter of $T \sim 15 \, \rm MeV$. We will present a scenario
which explains the observed slope parameter and which allows us to predict the
expected slope parameter for kaons produced in heavier systems such as Au+Au.
Implications for the restoration of chiral symmetry in relativistic heavy ion
collisions are discussed.(figures are being sent on request)


title:
Comment on E2 Contribution to the 8B ---> p + 7Be Coulomb Dissociation
  Cross Section [K. Langanke and T.D. Shoppa, Phys. Rev. C49(1994)R1771,
  ER(1994)]

abstract:
  The E2 cross section calculated by Langanke and Shoppa for the Riken
experiment on the Coulomb Dissociation of 8B uses E2 nuclear matrix elements
from one specific model. Other nuclear models predict a considerably smaller E2
cross section (by a pproximately a factor of 3 to 4), and Langanke and Shoppa
appear to assume the most optimistic scenario predicting large E2 cross
section. We also note that Barker has already criticised the nuclear model used
by Langanke and Shoppa. A MODEL INDEPENDENT Chi-Square analysis of the Riken
data, suggest the best fit for the current Riken data is obtained with E1
amplitudes only. The upper limit (90% confidence) on the E2 component derived
from our Chi-Square analysis is considerably smaller than used by Langanke and
Shoppa. The MODEL DEPENDENT analysis of Langanke-Shoppa should not be
considered as a correction to the Riken result, as claimed, and their quoted
S17(0) is not substantiated.


title: Two-Meson and Multi-Pion Final States from 600 Gev Pion Interactions

abstract:
  This report describes the transitions pion -> meson_1 + meson_2 and also pion
-> multi-pion for high energy pions interacting with target nuclei (Z,A). The
physics interests are: A) Nuclear inelastic coherent diffraction cross sections
for pions, for studies of size fluctuations in the pion wave function. B)
Radiative widths of excited meson states, for tests of vector dominance and
quark models. C) Experimental determination of the pi- + rho -> pi- + gamma
total reaction rate for gamma production above 0.7 GeV, needed for background
studies of quark-gluon plasma formation experiments. D) Investigation of the
gamma ->3 pi vertex in pion pair production by a pion, for a significantly
improved test of the hypothesis of chiral anomalies. The physics interest and
associated bibliography are summarized here; with particular reference to the
200-600 GeV beams available at FNAL and CERN. Complementary GEANT simulations
and trigger studies are needed.


title:
Anomalous A-dependence of diffractive leptoproduction of radial
  excitation $\rho'(2S)$

abstract:
  We predict a strikingly different $A$ and $Q^{2}$ dependence of quasielastic
leptoproduction of the $\rho^{0}(1S)$-meson and its radial excitation $\rho
'(2S)$ on nuclei. Whereas for the $\rho^{0}$ production nuclear transparency
$T_{A}$ decreases monotonically with $A$, for the $\rho'$ nuclear transparency
$T_{A}$ can have the counterintuitive nonmonotonic $A$-dependence, having the
minimum for light nuclei, and increasing with $A$ for medium and heavy nuclei.
Strong enhancement of the $\rho ' /\rho^{0}$ cross section ratio makes nuclear
targets the $\rho '$-factory. The origin of the anomalous $A$-dependence is in
the interplay of color transparency effects with the nodal structure of the
$\rho '$ wave function. The predicted effects take place at moderate
$Q^{2}\lsim (2-3)$GeV$^{2}$, which can be explored in high statistics
experiments at CEBAF.


title: Hermitian boson mapping and finite truncation

abstract:
  Starting from a general, microscopic fermion-to-boson mapping that preserves
Hermitian conjugation, we discuss truncations of the boson Fock space basis. We
give conditions under which the exact boson images of finite fermion operators
are also finite (e.g., a 1+2-body fermion Hamiltonian is mapped to a 1+2-body
boson Hamiltonian) in the truncated basis. For the most general case, where the
image is not necessarily exactly finite, we discuss how to make practical and
controlled approximations.


title: Toward a Consistent Description of the PNC Experiments in A=18-21 Nuclei

abstract:
  The experimental PNC results in $^{18}$F, $^{19}$F, $^{21}$Ne and the current
theoretical analysis show a discrepancy . If one interprets the small limit of
the experimentally extracted PNC matrix element for $^{21}$Ne as a destructive
interference between the isoscalar and the isovector contribution, then it is
difficult to understand why the isovector contribution in $^{18}$F is so small
while the isoscalar + isovector contribution in $^{19}$F is relatively large.
In order to understand the origin of this discrepancy a comparison of the
calculated PNC matrix elements was performed. It is shown that the $^{18}$F and
$^{21}$Ne matrix elements contain important contributions from 3$\hbar \omega$
and 4$\hbar \omega$ configuration and that the (0+1)$\hbar \omega$ calculations
give distorted results.


title: Chaos and Order in the Shell Model Eigenvectors

abstract:
  The energies and wave functions of stationary many-body states are analyzed
to look for the signatures of quantum chaos. Shell model calculations with the
Wildenthal interaction are performed in the $J-T$ scheme for 12 particles in
the $sd$-shell. The local level statistics are in perfect agreement with the
GOE predictions. The analysis of the amplitudes of the eigenvectors in the
shell model basis with the aid of the informational entropy and moments of the
distribution function shows evidence for local chaos with a localization length
reaching 90\% of the total dimension in the middle of the spectrum. The degree
of chaoticity is sensitive to the the strength of the residual interaction as
compared to the single particle energy spacing.


title: Photon absorption on a neutron-proton pair in $^3$He

abstract:
  The cross section of the reaction $^3$He$(\gamma,pn)p_{spec}$ in the energy
range 150 - 450 MeV has been calculated in a quasifree two-body model and
compared with a recent kinematically complete experiment. In comparison with
free deuteron disintegration the cross section is increased by a factor of
about 1.5 in reasonable agreement with the data for photon energies above 200
MeV. At lower energies the data deviate from the two-body behaviour and thus
suggest a more important role of the spectator requiring a more exact
treatment.


title:
Muon capture, continuum random phase approximation and in-medium
  renormalization of the axial-vector coupling constant

abstract:
  We use the continuum random phase approximation to describe the muon capture
on C-12, O-16 and Ca-40. We reproduce the experimental total capture rates on
these nuclei to better than 10% using the free nucleon weak form factors and
two different residual interactions. However, the calculated rates for the same
residual interactions are significantly lower than the data if the in-medium
quenching of the axial-vector coupling constant is employed.


title:
Quenching of spin operators in the calculation of radiative corrections
  for nuclear beta decay

abstract:
  Calculations of the axial-vector component to the radiative correction for
superallowed Fermi $0^+ \rightarrow 0^+$ nuclear beta decay are here modified
with quenched rather than free-nucleon coupling constants for the axial-vector
and electromagnetic interactions with nucleons. The result increases the
deduced value of $V_{ud}$ but does not restore unitarity in the CKM matrix.


title: Nucleon Properties from Unconventional Interpolating Fields

abstract:
  Interpolating fields, used to excite hadrons from the QCD vacuum in
nonperturbative field-theoretic investigations of hadron properties, are
explored with an emphasis on unconventional nucleon interpolators. The QCD
continuum model for excited state contributions to QCD correlation functions is
a central element in extracting the physics contained in these alternate
correlation functions. The analysis confirms the independence of nucleon
properties obtained from different interpolating fields. However, this
independence comes about in a trivial manner. These results provide a
resolution to the long standing debate over the optimal nucleon interpolating
field to be used in QCD Sum Rule analyses.


title: Gamow-Teller Strength in the Region of $^{100}$Sn

abstract:
  New calculations are presented for Gamow-Teller beta decay of nuclei near
$^{100}$Sn. Essentially all of the $^{100}$Sn Gamow-Teller decay strength is
predicted to go to a single state at an excitation energy of 1.8 MeV in
$^{100}$In. The first calculations are presented for the decays of neighboring
odd-even and odd-odd nuclei which show, in contrast to $^{100}$Sn, surprisingly
complex and broad Gamow-Teller strength distributions. The results are compared
to existing experimental data and the resulting hindrance factors are
discussed.


title: Neutrino Oscillations in Noisy Media

abstract:
  We develop the Redfield equation for delta-correlated gaussian noise and
apply it to the case of two neutrino flavor or spin precession in the presence
of a noisy matter density or magnetic field, respectively. The criteria under
which physical fluctuations can be well approximated by the delta-correlated
gaussian noise for the above cases are examined. Current limits on the possible
neutrino magnetic moment and solar magnetic field suggest that a reasonably
noisy solar magnetic field would not appreciably affect the solar electron
neutrino flux. However, if the solar electron density has fluctuations of a few
percent of the local density and a small enough correlation length, the MSW
effect is suppressed for a range of parameters.


title: Truncation Method for the Shell Model Calculation

abstract:
  A method of truncating the large shell model basis is outlined. It relies on
the order given by the unperturbed energies of the basis states and on the
constancy of their spreading widths. Both quantities can be calculated by a
simple averaging procedure. The method is tested in the sd shell where the JT
dimensions are of the order of a few thousand. It proves to be very effective
in the middle of the fp shell where JT dimensions of the order of a few million
are truncated to a few thousand.


title:
Color transparency after the NE18 and E665 experiments: Outllok and
  perspectives at CEBAF

abstract:
  CEBAF is a high-luminocity factory of virtual photons with variable
virtuality $Q^{2}$ and transverse size. This makes CEBAF, in particular after
the energy upgrade to (8-12)GeV, an ideal facility for uncovering new
phenomena, and opening new windows, at the interface of the perturbative and
nonperturbative QCD. We discuss color transparency as the case for a broad
program on electroproduction of vector mesons
$\rho^{0},\,\omega^{0},\,\phi^{0}$ and their radial excitations
$\rho',\,\omega',\,\phi'$ at CEBAF. We also comment on the second generation of
experiments on color transparency in $^{4}He(e,e'p)$ scattering, which are also
feasible at CEBAF. In 1994, we can make more reliable projections into future
because our understanding of the onset of color transparency has greatly been
augmented by two experiments completed in 1993:\\ i) no effect of CT was seen
in the SLAC NE18 experiment on $A(e,e'p)$ scattering at virtualities of the
exchanged photon $Q^{2} \lsim 7$ GeV$^{2}$, \\ ii) strong signal of CT was
observed in the FNAL E665 experiment on exclusive $\rho^{0}$- meson production
in deep inelastic scattering in the same range of $Q^{2}$. \\ We discuss the
impact of these observations on the CEBAF experimental program. We argue they
both are good news, both were anticipated theoretically, and both rule in the
correct QCD mechanism of the onset of CT.


title:
Orbital and Spin Magnetic Dipole Strength in a shell model calculation
  with $\Delta N$=$2$ excitations: $^8\mbox{Be}$

abstract:
  The magnetic dipole strength and energy-weighted strength distribution is
calculated in $^8\mbox{Be}$, as well as the separate orbit and spin parts. All
$\Delta N$=$2$ excitations over and above (and including) the configuration
$0s^4$$0p^4$ are included. The interaction has a central, two-body spin-orbit
and a tensor part. The energy- independent and energy-weighted {\underline
orbital} strength distribution is remarkably insensitive to the presence or
absence of the spin-orbit or tensor interaction -not so the spin strength. The
energy-weighted strength distribution can be divided into a low enegy and a
high energy part. The high energy orbital part is somewhat less but close to
the low energy part, in fair agreement with a prediction that they be equal by
de Guerra and Zamick and by Nojarov. There is a wide plateau separating the low
energy part from the high energy part.


title: Single-Particle Nondegeneracy and SU(3) Fermion Dynamical Symmetry

abstract:
  It is shown that the SU(3) symmetry of the fermion dynamical symmetry model
is essentially preserved even for highly nondegenerate spherical
single-particle energies. The breaking of SU(3) symmetry by single-particle
energy terms for either normal deformation or superdeformation occurs only
through an indirect Pauli effect and is significant only when the spherical
single-particle splitting within shells is artificially large relative to that
observed experimentally.


title:
Mean-field description of ground-state properties of drip-line nuclei.
  (I) Shell-correction method

abstract:
  A shell-correction method is applied to nuclei far from the beta stability
line and its suitability to describe effects of the particle continuum is
discussed. The sensitivity of predicted locations of one- and two-particle drip
lines to details of the macroscopic-microscopic model is analyzed.


title: ``Chaos" in Nuclear High Spin Spectroscopy

abstract:
  The Projected Shell Model with zero-, two- and four-quasiparticle
configurations is used to investigate the level statistics, i.e. chaoticity, of
high spin spectroscopy. The model can describe many high spin phenomena and
with the present configuration space has sufficient number of levels for
statistical analysis. It is found that the degree of chaoticity has a sensitive
dependence on the classification of levels in question, and that it steadily
increases with excitation energy and angular momentum.


title: S-Wave Pion-Pion Correlations in Dense Nuclear Matter

abstract:
  The s-wave correlated $\pi$-$\pi$ strength distribution in cold nuclear
matter is investigated. The in-medium single pions are renormalized by means of
the usual p-wave couplings to nucleons and $\Delta$'s. Two groups of models for
the $\pi$-$\pi$ interaction are studied. The first one uses phenomenological
models which reproduce the phase shifts but do not respect the soft-pion
theorems. With increasing density a strong accumulation of strength in the
subhreshold region is observed. Slightly above saturation density there even
occurs an instability with respect to s-wave $\pi$-$\pi$ pair condensation.
These effects are strongly moderated or disappear altogether if constraints
from chiral symmetry are built into the $\pi$-$\pi$ interaction.


title:
Off-Shell Rho-Omega Mixing Through Quark Loops With Non-Perturbative
  Meson Vertex And Quark Mass Functions

abstract:
  The momemtum dependence of the off-shell $\rho$-$\omega$ mixing amplitude is
calculated through a two-quark loop diagram, using non-perturbative meson-quark
vertex functions for the $\rho$ and $\omega$ mesons, as well as
non-perturbative quark propagators. Both these quantities are generated
self-consistently through an interlinked BSE-cum-SDE approach with a 3D support
for the BSE kernel with two basic constants which are pre- checked against a
wide cross section of both meson and baryon spectra within a common structural
framework for their respective 3D BSE's. With this pre-calibration, the
on-shell strength works out at -2.434$\delta(m_q^2)$ in units of the change in
"constituent mass squared", which is consistent with the $e^+e^-$ to
$\pi^+\pi^-$ data for a u-d mass difference of ~4 MeV ,while the relative
off-shell strength (0.99 $\pm$ 0.01) lies midway between quark-loop and QCD-SR
results. We also calculate the photon-mediated $\rho$-$\omega$ propagator whose
off-shell structure has an additional pole at $q^2$=0. The implications of
these results vis-a-vis related investigations are discussed.


title: Chaos in Axially Symmetric Potentials with Octupole Deformation

abstract:
  Classical and quantum mechanical results are reported for the single particle
motion in a harmonic oscillator potential which is characterized by a
quadrupole deformation and an additional octupole deformation. The chaotic
character of the motion is srongly dependent on the quadrupole deformation in
that for a prolate deformation virtually no chaos is discernible while for the
oblate case the motion shows strong chaos when the octupole term is turned on.


title: Shape Coexistence Around $^{44}_{16}$S$_{28}$: The Deformed N=28 Region

abstract:
  Masses, deformations, radii, and single-particle properties of the very
neutron-rich Sulfur isotopes are investigated in the framework of the
selfconsistent mean-field theory. The stability of the N=28 magic gap around
$^{44}$S is discussed.


title: Chiral and Gluon Condensates at Finite Temperature

abstract:
  We investigate the thermal behaviour of gluon and chiral condensates within
an effective Lagrangian of pseudoscalar mesons coupled to a scalar glueball.
This Lagrangian mimics the scale and chiral symmetries of QCD. (Submitted to Z.
Phys. C)


title:
Two-nucleon knockout contributions to the $^{12}$C$(e,e'p)$ reaction in
  the dip and {$\Delta$}(1232) regions

abstract:
  The contributions from $^{12}$C$(e,e'pn)$ and $^{12}$C$(e,e'pp)$ to the
semi-exclusive $^{12}$C$(e,e'p)$ cross section have been calculated in an
unfactorized model for two-nucleon emission. We assume direct two-nucleon
knockout after virtual photon coupling with the two-body pion-exchange currents
in the target nucleus. Results are presented at several kinematical conditions
in the dip and $\Delta$(1232) regions. The calculated two-nucleon knockout
strength is observed to account for a large fraction of the measured $(e,e'p)$
strength above the two-nucleon emission threshold.


title:
Secondary phi meson peak as an indicator of QCD phase transition in
  ultrarelativistic heavy ion collisions

abstract:
  In a previous paper, we have shown that a double phi peak structure appears
in the dilepton invariant mass spectrum if a first order QCD phase transition
occurs in ultrarelativistic heavy ion collisions. Furthermore, the transition
temperature can be determined from the transverse momentum distribution of the
low mass phi peak. In this work, we extend the study to the case that a smooth
crossover occurs in the quark-gluon plasma to the hadronic matter transition.
We find that the double phi peak structure still exists in the dilepton
spectrum and thus remains a viable signal for the formation of the quark-gluon
plasma in ultrarelativistic heavy ion collisions.


title: Quasifree photoabsorption on neutron-proton pairs in 3He

abstract:
  Three-body photodisintegration of 3He is calculated in the photon energy
range 200 - 400 MeV assuming quasifree absorption on np pairs both in initial
quasideuteron and singlet configurations. The model includes the normal
nucleonic current, explicit meson exchange currents and the Delta(1232)-isobar
excitation. The total cross section is increased by a factor of about 1.5
compared with free deuteron photodisintegration. Well below and above the Delta
region also some spin observables differ significantly from the ones of free
deuteron disintegration due to the more compressed wave function of the
correlated np pairs in 3He compared to the deuteron. The initial singlet state
causes a significant change in the analyzing power Ay. These differences could
presumably be seen at the conjugate angles where two-body effects are maximized
and where photoreactions could complement similar pion absorption experiments.
Figures by fax or post from janiskanen@phcu.helsinki.fi


title:
Temperature Dependence of the Chiral Condensate from an Interacting Pion
  Gas

abstract:
  By exploiting the fact that the chiral condensate is related to the
derivative of the free-energy density with respect to the bare quark mass we
calculate the temperature dependence of the condensate ratio $\ave{\bar
qq}_T/\ave{\bar qq}_0$ from an iteracting pion gas. When using the Weinberg
Lagrangian at the Hartree level we find a depression of the condensate with
temperature. For $T < 100$ MeV the results are in good agreement with chiral
perturbation theory in the three loop approximation. Near $T_c$, however, there
are marked differences due to non-perturbative nature of our approach.


title:
Nuclear-Spin-Dependent Parity-Nonconserving Effects in Thallium, Lead
  and Bismuth Atoms

abstract:
  Nuclear-spin-dependent P-odd optical activity in atomic Tl, Pb and Bi is
calculated. Its magnitude is expressed analytically through the main
contribution to the optical rotation, which is independent of nuclear spin. The
accuracy of results is discussed.


title: Downloading the Nuclear Structure Shell Model Code OXBASH from INTERNET

abstract:
  This document explains how to download the OXBASH code for nuclear structure
calculations from the NSCL anonymous server and get it running on VAX (VMS),
ALPHA (OpenVMS) and IBM RS/6000 (aix) computers. The physics behind the code is
explained in the OXBASH manual, which is part of the downloading package.
Everybody is welcome to download the code and use it under the conditions
described below.


title:
A Limited Symmetry Found by Comparing Calculated Magnetic Dipole Spin
  and Orbital Strengths in $^4\mbox{He}$

abstract:
  Allowing for $2$$\hbar \omega$ admixtures in $^4\mbox{He}$ we find that the
summed magnetic dipole isovector orbital and spin strengths are equal. This
indicates a symmetry which is associated with interchanging the labels of the
spin with those of the orbit. Where higher admixtures are included, the orbital
sum becomes larger than the spin sum, but the sums over the low energy region
are still nearly the same.


title: Partial Wave Analyses of the pp data alone and of the np data alone

abstract:
  We present results of the Nijmegen partial-wave analyses of all NN scattering
data below Tlab = 500 MeV. We have been able to extract for the first time the
important np phase shifts for both I = 0 and I = 1 from the np scattering data
alone. This allows us to study the charge independence breaking between the pp
and np I = 1 phases. In our analyses we obtain for the pp data chi^2_{min}/Ndf
= 1.13 and for the np data chi^2_{min}/Ndf = 1.12.


title: Charge Independence and Symmetry of Nuclear Forces

abstract:
  Charge independence and symmetry are approximate symmetries of nature. The
observations of the small symmetry breaking effects and the consequences of
those effects are reviewed. The effects of the mass difference between up and
down quarks and the off shell dependence $q^2$ of $\rho^0$-$\omega$ mixing are
stressed. In particular, I argue that models which predict a strong $q^2$
dependence of $\rho^0$-$\omega$ mixing seem also to predict a strong $q^2$
variation for the $\rho^0$-$\gamma^*$ matrix element, in contradiction with
experiment.


title:
RPA calculation of $K^+$-nucleus cross-sections with a density-dependent
  Brueckner-Hartree-Fock NN interaction

abstract:
  In the calculation of the $K^+$-nucleus cross sections, the coupling of the
mesons exchanged between the $K^+$ and the target nucleons to the polarization
of the Fermi and Dirac seas has been taken into account. This polarization has
been calculated in the one-loop approximation but summed up to all orders (RPA
approximation). For this calculation a density-dependent Brueckner-Hartree-Fock
NN interaction providing a good description of both nuclear matter and finite
nuclei has been used. The agreement with experiment is considerably improved.


title: Antiproton Induced Reactions

abstract:
  The various aspects of antiproton physics are shortly reviewed, and its
relevance for the possible discovery of new particles and effects is pointed
out. Then a survey of the nucleon-antinucleon interactions is given. In the
nucleon-antinucleon annihilations, there is a big amount of experimental data
that call for theoretical explanation. Importance of specific spin and isospin
channels for our understanding of antiproton physics is stressed.


title: Photons from axial-vector radiative decay in a hadron gas

abstract:
  Strange and non-strange axial-vector meson radiative decays contribute to
photon production in hadron gas. One- and two-hadron radiative decay modes of
$b_{1}(1235)$, $a_{1}(1260)$ and $K_{1}(1270)$ are studied. At 200 MeV
temperature and for a narrow range in photon energies they contribute more to
the net thermal photon production rate than $\pi\rho\rightarrow \pi\gamma$,
$\pi\pi\rightarrow \rho\gamma$ or $\rho\rightarrow\pi\pi\gamma$. They provide
significant contribution to the rate for photon energies as high as 1.5--2.0
GeV. For higher energies they are less important.


title: Trapping of Projectiles in Fixed Scatterer Calculations

abstract:
  We study multiple scattering off nuclei in the closure approximation. Instead
of reducing the dynamics to one particle potential scattering, the scattering
amplitude for fixed target configurations is averaged over the target
groundstate density via stochastic integration. At low energies a strong
coupling limit is found which can not be obtained in a first order optical
potential approximation. As its physical explanation, we propose it to be
caused by trapping of the projectile. We analyse this phenomenon in mean field
and random potential approximations.
  (PACS: 24.10.-i)


title: Asymmetric nuclear matter and neutron star properties

abstract:
  We calculate properties of neutron stars such as mass and radius using a
relativistic Dirac-Brueckner-hartree-Fock apprach for asymmetric nuclear
matter. For pure neutron matter we find the maximum mass to be 2.4 solar masses
with a radius of 12 km. For a proton fraction of 30% we find a max mass of 2.1
solar masses and a radius of 10.5 km. The implications are discussed.


title: Chiral symmetry in nuclei: partial restoration and its consequences

abstract:
  Partial restoration in nuclear matter of the chiral symmetry of QCD is
discussed together with some of its possible signals. Estimates of corrections
to the leading, linear dependence of the quark condensate are found to be
small, implying a significant reduction of that condensate in matter. The
importance of the pion cloud for the scalar quark density of a single nucleon
indicates a close connection between chiral symmetry restoration and the
attractive two-pion exchange interaction between nucleons. This force is
sufficiently long-ranged that nucleons in nuclear matter will feel a
significant degree of symmetry restoration despite the strong correlations
between them. Expected consequences of this include reductions in hadron masses
and decay constants. Various signals of these effects are discussed, in
particular the enhancement of the axial charge of a nucleon in matter.


title: K$^-$-proton scattering and the $\Lambda (1405)$ in dense matter

abstract:
  The scattering of antikaons with nucleons is studied in the nuclear
environment. Describing the $\lam$ as a $K^-$ proton bound state, we find, that
due to the Pauli blocking of intermediate states, the mass of the $\Lambda
(1405)$ is shifted upwards in energy, above the $K^-$ proton threshold and and
its width is somewhat broadened. As a consequence the s-wave $K^-$--nucleon
scattering length turns attractive at finite nucleon density ($\rho \geq 0.25
\rho_0$) leading to a mean field potential for the $K^-$ of about $\sim -100 \,
\rm MeV$ in nuclear matter at ground state density. Consequences for Heavy Ion
collisions and possible experimental checks for the structure of the $\lam$ are
discussed. (Figures will be sent on request)


title:
Functional approach to the electromagnetic response function: the
  Longitudinal Channel

abstract:
  In this paper we address the (charge) longitudinal electromagnetic response
for a homogeneous system of nucleons interacting via meson exchanges in the
functional framework. This approach warrants consistency if the calculation is
carried on order-by-order in the mesonic loop expansion with RPA-dressed
mesonic propagators. At the 1-loop order and considering pion, rho and omega
exchanges we obtain a quenching of the response, in line with the experimental
results.


title: Forms of Relativistic Dynamics: What Are the Possibilities?

abstract:
  Various methods of constructing solvable few-body models are reviewed, with
an emphasis on direct interactions with few degrees of freedom, as an
alternative to the use of local quantum field theories. Several applications
are discussed.


title:
Classical Hadrodynamics: A New Approach to Ultrarelativistic Heavy-Ion
  Collisions

abstract:
  We discuss a new approach to ultrarelativistic heavy-ion collisions based on
classical hadrodynamics for extended nucleons, corresponding to nucleons of
finite size interacting with massive meson fields. This new theory provides a
natural covariant microscopic approach that includes automatically spacetime
nonlocality and retardation, nonequilibrium phenomena, interactions among all
nucleons and particle production. In the current version of our theory, we
consider $N$ extended unexcited nucleons interacting with massive neutral
scalar ($\sigma$) and neutral vector ($\omega$) meson fields. The resulting
classical relativistic many-body equations of motion are solved numerically
without further approximation for soft nucleon-nucleon collisions at $p_{\rm
lab}$ = 14.6, 30, 60, 100 and 200 GeV/$c$ to yield the transverse momentum
imparted to the nucleons. For the future development of the theory, the
isovector pseudoscalar ($\pi^+$, $\pi^-$, $\pi^0$), isovector scalar
($\delta^+$, $\delta^-$, $\delta^0$), isovector vector ($\rho^+$, $\rho^-$,
$\rho^0$) and neutral pseudoscalar ($\eta$) meson fields that are known to be
important from nucleon-nucleon scattering experiments should be incorporated.
In addition, the effects of quantum uncertainty on the equations of motion
should be included by use of techniques analogous to those used by Moniz and
Sharp for nonrelativistic quantum electrodynamics.


title: Particle-Production Mechanism in Relativistic Heavy-Ion Collisions

abstract:
  We discuss the production of particles in relativistic heavy-ion collisions
through the mechanism of massive bremsstrahlung, in which massive mesons are
emitted during rapid nucleon acceleration. This mechanism is described within
the framework of classical hadrodynamics for extended nucleons, corresponding
to nucleons of finite size interacting with massive meson fields. This new
theory provides a natural covariant microscopic approach to relativistic
heavy-ion collisions that includes automatically spacetime nonlocality and
retardation, nonequilibrium phenomena, interactions among all nucleons, and
particle production. Inclusion of the finite nucleon size cures the
difficulties with preacceleration and runaway solutions that have plagued the
classical theory of self-interacting point particles. For the soft reactions
that dominate nucleon-nucleon collisions, a significant fraction of the
incident center-of-mass energy is radiated through massive bremsstrahlung. In
the present version of the theory, this radiated energy is in the form of
neutral scalar ($\sigma$) and neutral vector ($\omega$) mesons, which
subsequently decay primarily into pions with some photons also. Additional
meson fields that are known to be important from nucleon-nucleon scattering
experiments should be incorporated in the future, in which case the radiated
energy would also contain isovector pseudoscalar ($\pi^+$, $\pi^-$, $\pi^0$),
isovector scalar ($\delta^+$, $\delta^-$, $\delta^0$), isovector vector
($\rho^+$, $\rho^-$, $\rho^0$), and neutral pseudoscalar ($\eta$) mesons.


title: Electromagnetic Meson Form Factors in the Salpeter Model

abstract:
  We present a covariant scheme to calculate mesonic transitions in the
framework of the Salpeter equation for $q\bar{q}$-states. The full Bethe
Salpeter amplitudes are reconstructed from equal time amplitudes which were
obtained in a previous paper\cite{Mue} by solving the Salpeter equation for a
confining plus an instanton induced interaction. This method is applied to
calculate electromagnetic form factors and decay widths of low lying
pseudoscalar and vector mesons including predictions for CEBAF experiments. We
also describe the momentum transfer dependence for the processes
$\pi^0,\eta,\eta'\rightarrow\gamma\gamma^*$.


title: Isolated States

abstract:
  We show that a quantum system with nonlocal interaction can have bound states
of unusual type (isolated states (IS)). IS is a bound state that do not
generate a $S$-matrix pole. IS can have positive as well as negative energy and
can be treated as a generalization of bound states embedded in continuum on the
case of discrete spectrum states. Formation of IS in the spectrum of quantum
system is studied using a simple rank--2 separable potential with harmonic
oscillator formfactors. Some physical applications are discussed, in
particular, we propose separable $NN$ potential that describes not only most
important two-nucleon data (deuteron binding energy and s-wave triplet and
singlet scattering phases) but also the trinucleon binding energy without
making use of three-body forces.


title: Nucleon Structure Functions from Relativistic Constituent Quarks

abstract:
  We investigate deep inelastic lepton scattering from the nucleon within a
constituent quark picture, in which the internal structure of constituent
quarks is modeled by meson and diquark dressing. In a covariant framework this
structure leads to a breakdown of the factorization necessary for a convolution
formulation. We perform our analysis in time-ordered perturbation theory in the
infinite momentum frame where factorization of subprocesses is automatic.
Numerical results are compared with recent data on valence quark distributions
in the proton.


title:
Nuclear Transparency in Quasifree Electron Scattering - Theory and
  Experiment

abstract:
  We make detailed comparisons between the measured $Q^2$ dependency of nuclear
transparency in quasifree electron scattering and theoretical predictions based
on Glauber theory. We also describe a theory-free method to extract $T$ from
data.


title: Construction of high-quality Nucleon-Nucleon potential models

abstract:
  We present an updated version (Nijm93) of the Nijmegen soft-core potential,
which gives a much better description of the np data than the older version
(Nijm78). The chi^2 per datum is 1.87. The configuration-space and
momentum-space versions of this potential are exactly equivalent; a unique
feature among meson-theoretical potentials. We also present three new NN
potential models: a non-local Reid-like Nijmegen potential (NijmI), a local
version (NijmII), and an updated regularized version (Reid93) of the Reid
soft-core potential. These three potentials all have a nearly optimal chi^2 per
datum and can therefore be considered as alternative partial-wave analyses. All
potentials contain the proper charge-dependent one-pion-exchange tail. Fortran
code for the potentials can be obtained via anonymous ftp from
thef-nym.sci.kun.nl


title:
Relativistic treatment of spin-transfer observables in quasielastic
  $(\vec{\bf p},\vec{\bf n})$ scattering

abstract:
  We calculate all spin-transfer observables for the quasielastic
$(\vec{p},\vec{n})$ reaction in a relativistic plane-wave impulse
approximation. The nuclear-structure information is contained in a large set of
nuclear-response functions that are computed in nuclear matter using a
relativistic random-phase approximation to the Walecka model. A reduced value
of the nucleon mass in the medium induces important dynamical changes in the
residual isovector interaction relative to its nonrelativistic counterpart. As
a result, good agreement is found for all spin observables --- including the
spin-longitudinal to spin-transverse ratio --- when compared to the original
($q=1.72$~fm$^{-1}$) NTOF experiment. In contrast, the spin-longitudinal to
spin-transverse ratio is underpredicted at $q=1.2$~fm$^{-1}$ and overpredicted
at $q=2.5$~fm$^{-1}$. We comment on the role of distortions as a possible
solution to this discrepancy.


title: Friedel Oscillations in Relativistic Nuclear Matter

abstract:
  We calculate the low-momentum N-N effective potential obtained in the OBE
approximation, inside a nuclear plasma at finite temperature, as described by
the relativistic $ \sigma $-$ \omega $ model. We analyze the screening effects
on the attractive part of the potential in the intermediate range as density or
temperature increase. In the long range the potential shows Friedel-like
oscillations instead of the usual exponential damping. These oscillations arise
from the sharp edge of the Fermi surface and should be encountered in any
realistic model of nuclear matter.


title:
The nucleon as a relativistic quark-diquark bound state with an exchange
  potential

abstract:
  Treating the quark and diquark as elementary particles, the Bethe-Salpeter
equation for the nucleon is solved numerically. The dependence of the mass on
the diquark mass and on the coupling constants is investigated. The resulting
relativistic quark-diquark-nucleon vertex is presented and discussed.


title:
New Shell Structure Originated from the Combination of Quadrupole and
  Octupole Deformations

abstract:
  Semiclassical analysis of the shell structure for a reflection-asymmetric
deformed oscillator potential with irrational frequency ratio
$\omega_\perp/\omega_z=\sqrt{3}$ is presented. Strong shell effects associated
with bifurcations of short periodic orbits are found, which occur for a
combination of quadrupole and octupole deformations.


title: Anomalous Isotope Shifts in Pb Nuclei in RMF Theory

abstract:
  We have studied the anomalous behaviour of isotopic shifts of Pb nuclei in
the relativistic mean field theory. It has been shown that the relativistic
mean field provides an excellent description of the anomalous kink in the
isotopic shifts about $^{208}$Pb. This is in contrast from density-dependent
Skyrme forces which do not reproduce the observed trend in the empirical data
on the charge radii. We discuss some differences in the description of isotope
shifts in the RMF theory and the Skyrme mean field.


title: A Relativistic Approach to Deep Inelastic Scattering on the Deuteron

abstract:
  A covariant field theoretical approach to deep inelastic scattering on the
deuteron is presented. The deuteron structure function is calculated in terms
of the Bethe-Salpeter amplitude. Numerical calculations for the nucleon
contribution are made with a realistic model of the $NN$-interaction, including
$\pi$-, $\rho$-, $\omega$-, $\eta$-, $\delta$- and $\sigma$-mesons, and results
are compared with previous non-relativistic calculations.


title: Relativistic Deuteron Structure Function

abstract:
  We calculate the unpolarised deep inelastic structure function of a
relativistic deuteron within a covariant framework. An exact treatment of
nucleon off-shell effects is shown to give corrections to the widely-used
convolution model, even in impulse approximation. Neglecting off-shell effects
in the extraction of the neutron structure function from deuterium data
introduces errors of order $1-2\%$.


title:
A transport theory of relativistic nucleon-nucleon collisions with
  confinement

abstract:
  A transport theory is developed on the quark level to describe
nucleon--nucleon collisions. We treat the strong interaction effectively by the
Friedberg-Lee model both in its original and in its modified confining version.
First we study the stability of the static three-dimensional semiclassical
configuration, then we present results of the time evolution given by a Vlasov
equation for the quarks coupled to a Klein-Gordon equation for the mean field.
We find at higher energies that the nucleons are almost transparent, whereas at
lower energies we observe a substantial interaction. At very low energies we
see a fusion of our bags, which is due to the purely attractive nature of the
mean field and hence is an artifact of our model. We test the confinement
mechanism and find that at higher energies the nucleons are restored shortly
after the collision.


title: Quark Hadron Phase Transition and Hybrid Stars

abstract:
  We investigate the properties of hybrid stars consisting of quark matter in
the core and hadron matter in outer region. The hadronic and quark matter
equations of state are calculated by using nonlinear Walecka model and chiral
colour dielectric (CCD) model respectively. We find that the phase transition
from hadron to quark matter is possible in a narrow range of the parameters of
nonlinear Walecka and CCD models. The transition is strong or weak first order
depending on the parameters used. The EOS thus obtained, is used to study the
properties of hybrid stars. We find that the calculated hybrid star properties
are similar to those of pure neutron stars.


title:
Electromagnetic Hadron Mass Differences and Estimation of Isotopic
  Symmetry Violation Parameters of QCD Vacuum from Quark Model

abstract:
  The estimations of the light quark mass differences, $m_d-m_u$, and the light
quark condensate differences, $<\bar DD> - <\bar UU>$, are obtained in the
framework of the \qm\ with QCD vacuum induced \q\ \ia . We consider long - wave
condensate and short - wave \s\ contributions to the electromagnetic \hn\ mass
\di s and show that the latter significantly improve the results on baryon
octet. The results are: $m_d-m_u \approx 3.5\ MeV$ and $<\bar DD> - <\bar UU>
\approx -(0\sim 3)\cdot10^{-3}<\bar UU>$.


title: Soft dipole mode in $^{11}$Li and three body continuum

abstract:
  Properties of the neutron rich $^{11}$Li nucleus are calculated in the
framework of the cluster model $^{9}$Li $+n+n$. The formalism of the harmonic
oscillator representation of the scattering theory is used for the description
of bound and continuum spectrum states in the three-body-democratic-decay
approximation. It is shown that this approach allows one to take into account
adequately the long asymptotic tail of the $^{11}$Li wave function ({\em
neutron halo}) and to reproduce correctly the binding energy, radius and
$^{11}$Li electromagnetic dissociation cross-section on target nuclei. The
shape and the energy position of the $B(E1)$ peak corresponding to the soft
dipole mode are also in agreement with experiment.


title:
Microscopic Model of the Time Like Electromagnetic Form Factor of the
  Nucleon

abstract:
  A microscopic model of the electromagnetic form factor of the nucleon is
developed in a hadronic framework, including pions, nucleons and the
Delta-resonance explicitly. The space like on-shell form factors are reproduced
and predictions for the half off-shell dependence are made. The impact of this
off-shell dependence in the time like sector (q^2 < 1 GeV^2, thus including the
region of vector meson dominance) is of main interest in this investigation.


title: 6Li Inelastic Form Factors in a Cluster Model

abstract:
  Longitudinal and transverse form factors are calculated for the transition
into the low lying excited T=0 and T=1 states of 6Li in the framework of the
resonating group model. All form factors are reproduced simultaneously using
three cluster-wavefunctions. Meson exchange currents yield only minor
corrections and do not lead to any specific structures at large momentum
transfers.


title: Heavy resonance production in high energy nuclear collisions

abstract:
  We estimate freezeout conditions for $s$, $c$, and $b$ quarks in high energy
nuclear collisions. Freezeout is due either to loss of thermal contact, or to
particles ``wandering'' out of the region of hot matter. We then develop a
thermal recombination model in which both single-particle (quark and antiquark)
and two-particle (quark-antiquark) densities are conserved. Conservation of
two-particle densities is necessary because quarks and antiquarks are always
produced in coincidence, so that the local two-particle density can be much
larger than the product of the single-particle densities. We use the freezeout
conditions and recombination model to discuss heavy resonance production at
zero baryon density in high energy nuclear collisions.


title: Phase-Space Exploration in Nuclear Giant Resonance Decay

abstract:
  The rate of phase-space exploration in the decay of isovector and isoscalar
giant quadrupole resonances in $^{40}$Ca is analyzed. The study is based on the
time dependence of the survival probability and of the spectrum of generalized
entropies evaluated in the space of 1p-1h and 2p-2h states. If the 2p-2h
background shows the characteristics typical for chaotic systems, the isovector
excitation evolves almost statistically while the isoscalar excitation remains
largely localized, even though it penetrates the whole available phase space.


title: Can dileptons reveal the in-medium properties of vector mesons?

abstract:
  Dilepton production from both pion-pion and kaon-antikaon annihilation in
heavy-ion collisions is studied using the relativistic transport model. The
formation of a rho meson from pion-pion annihilation and a phi meson from
kaon-antikaon annihilation, their propagation in the medium, and their decay
into dileptons are explicitly treated. Including the medium modifications of
the masses and widths of vector mesons as predicted by the QCD sum-rule
calculations, we study their effects on the dilepton invariant mass spectra
from heavy-ion collisions at SIS/GSI energies.


abstract:
  Antiproton production in Ni+Ni collisions at 1.85 GeV/nucleon is studied in
the relativistic Vlasov-Uehling-Uhlenbeck model. The self-energies of the
antiproton are determined from the nucleon self-energies by the G-parity
transformation. Also, the final-state interactions of the antiproton including
both rescattering and annihilation are explicitly treated. With a soft nuclear
equation of state, the calculated antiproton momentum spectrum is in good
agreement with recent experimental data from the heavy-ion synchrotron at GSI.
The effect due to the reduced nucleon and antinucleon masses in a medium is
found to be more appreciable than in earlier Bevalac experiments with lighter
systems and at higher energies.


title:
The relativistic transport model description of subthreshold kaon
  production in heavy-ion collisions

abstract:
  The relativistic transport model, in which the nucleon effective mass is
connected to the scalar field while its energy is shifted by the vector
potential, is extended to include the kaon degree of freedom. We further take
into account the medium modification of the kaon mass due to the explicit
chiral symmetry breaking. Both the propagation of kaons in the mean-field
potential and the kaon-baryon elastic scattering are explicitly treated in our
study. We find that the attractive kaon scalar mean-field potential in the
dense matter leads to an enhanced kaon yield in heavy-ion collisions at
energies of about 1 GeV/nucleon. The final-state kaon-baryon scattering is seen
to affect significantly the kaon momentum spectra, leading to an enhanced yield
of kaons with large momenta or at large laboratory angles. With a soft nuclear
equation of state and including the attractive kaon scalar potential, the
calculated kaon energy spectra agree with the data from the heavy-ion
synchrotron at GSI.


title: Democratic Decay

abstract:
  Results of some recent investigations of democratic three-body decays of
nuclear systems are discussed. In particular, we consider experimental studies
of three-body ($\alpha+N+N$)-decay of $A=6$ nuclei and $J$-matrix calculations
of monopole excitations in $^{12}$C and $E1$ transitions in $^{11}$Li in the
three-body-continuum cluster models $\alpha + \alpha + \alpha$ and $^{9}$Li + n
+ n, respectively.


title:
Resonance Model of $\pi \Delta \rightarrow Y K$ for Kaon Production in
  Heavy Ion Collisions

abstract:
  The elementary production cross sections $\pi \Delta \rightarrow Y K$
$(Y=\Sigma,\,\, \Lambda)$ and $\pi N \rightarrow Y K$ are needed to describe
kaon production in heavy ion collisions. The $\pi N \rightarrow Y K$ reactions
were studied previously by a resonance model. The model can explain the
experimental data quite well \cite{tsu}. In this article, the total cross
sections $\pi \Delta \rightarrow Y K$ at intermediate energies (from the kaon
production threshold to3 GeV of $\pi \Delta$ center-of-mass energy) are
calculated for the first time using the same resonance model. The resonances,
$N(1710)\,I(J^P) = \frac{1}{2}(\frac{1}{2}^+)$ and $N(1720)\, \frac{1}{2}
(\frac{3}{2}^+)$ for the $\pi \Delta \rightarrow \Sigma K$ reactions, and
$N(1650)\, \frac{1}{2} (\frac{1}{2}^-)$, $N(1710)\, \frac{1}{2}
(\frac{1}{2}^+)$ and $N(1720)\, \frac{1}{2} (\frac{3}{2}^+)$ for the $\pi
\Delta \rightarrow \Lambda K$ reactions are taken into account coherently as
the intermediate states in the calculations. Also t-channel $K^*(892)
\frac{1}{2}(1^-)$ vector meson exchange is included. The results show that
$K^*(892)$ exchange is neglegible for the $\pi \Delta \rightarrow \Sigma K$
reactions, whereas this meson does not contribute to the $\pi \Delta
\rightarrow \Lambda K$ reactions. Furthemore, the $\pi \Delta \rightarrow Y K$
contributions to kaon production in heavy ion collisions are not only
non-neglegible but also very different from the $\pi N \rightarrow Y K$
reactions. An argument valid for $\pi N \rightarrow Y K$ cannot be extended to
$\pi \Delta \rightarrow Y K$ reactions. Therefore, cross sections for $\pi
\Delta \rightarrow Y K$ including correctly the different isospins must be


title:
The Role of the $\Delta(1920)$ Resonance for Kaon Production in Heavy
  Ion Collisions

abstract:
  The long mean free path of $K^+$ mesons in nuclear matter makes this particle
a suitable messenger for the dynamics of nucleus-nucleus reactions at
intermediate energies (100 MeV to 3 GeV per nucleon). A prerequisite for this
is the knowledge of the elementary production cross sections $\pi N \rightarrow
\Sigma K$. Here these cross sections are studied for the first time with the
explicite inclusion of the relevant baryon resonances up to 2 GeV as
intermediate states. The baryon resonances -- $N(1710)\, I(J^P) = \frac{1}{2}
(\frac{1}{2}^+),\, N(1720)\, \frac{1}{2} (\frac{3}{2}^+)$ and $\Delta(1920)\,
\frac{3}{2} (\frac{3}{2}^+)\,$ -- are taken into account coherently in the
calculations of the $\pi N \rightarrow \Sigma K$ process. (We refer to this
model as the `resonance model'.) Also $K^*(892)\frac{1}{2} (1^-)$ vector meson
exchange is included. It is shown that the total cross sections for different
channels of the $\pi N \rightarrow \Sigma k$ reactions, i.e. $\pi^+ p
\rightarrow \Sigma^+ K^+$, $\pi^- p \rightarrow \Sigma^- K^+$, $\pi^+ n
\rightarrow \Sigma^0 K^+$ ($\pi^- p \rightarrow \Sigma^- K^+$) and $\pi^0 p
\rightarrow \Sigma^0 K^+$ differ not only by absolute values but also by their
energy dependence. This shape differences are due to the mixture of the isospin
$I = 3/2$ $\Delta(1920)$ with isospin $I = 1/2$ nucleon resonances. However,
this $I = 3/2$ resonance does not give a contribution to the $\pi N \rightarrow
\Lambda K$ reactions. So the shapes of the total cross sections $\pi N
\rightarrow \Lambda K$ for different isospin projections are the same. In spite
of this, such cross sections averaged over different isospin projections in the
same multiplet


title: Neutrinoless Double Beta Decay in Heavy Deformed Nuclei

abstract:
  The zero neutrino mode of the double beta decay in heavy deformed nuclei is
investigated in the framework of the pseudo SU(3) model, which has provided an
accurate description of collective nuclear structure and predicted half-lives
for the two neutrino mode in good agreement with experiments. In the case of
$^{238}U$ the calculated zero neutrino half-life is at least three orders of
magnitude greater than the two neutrino one, giving strong support of the
identification of the radiochemically determined half-life as being the two
neutrino double beta decay. For $^{150}Nd$ the zero neutrino matrix elements
are of the order of magnitude of, but lesser than, those evaluated using the
QRPA. This result confirms that different nuclear models produce similar zero
neutrino matrix elements, contrary to the two neutrino case. Using these pseudo
SU(3) results and the upper limit for the neutrino mass we estimate the
$\beta\beta_{0\nu}$ half-lives for six nuclei. An upper limit for majoron
coupling constant is extracted from the experimental data.


title: Pionic Content of Rho-N-N and Rho-N-Delta Vertex Functions

abstract:
  The dynamical content of rho-N-N and rho-N-Delta vertex functions is studied
with a mesonic model. A set of coupled integral equations satisfied by these
vertex functions were solved self-consistently. These soulutions indicate that
the dominant mesonic content arises from di-pion dynamics. With the
experimentally determined pion-baryon-baryon coupling constants and ranges as
input, the model predicts a g_{\rho NN} that agrees with the
meson-exchange-potential results. On the other hand, it predicts a smaller
f_{\rho N\Delta} and much softer form factors. Implications of the findings on
the use of phenomenological coupling constants in nuclear reaction studies are
discussed.


title: Constraint Correlation Dynamics of SU(N) Gauge Theories

abstract:
  A constraint correlation dynamics up to 4-point Green functions is proposed
for SU(N) gauge theories which reduces the N-body quantum field problem to the
two-body level. The resulting set of nonlinear coupled equations fulfills all
conservation laws including fermion number, linear and angular momenta as well
as the total energy. Apart from the conservation laws in the space-time degrees
of freedom the Gauss law is conserved as a quantum expectation value
identically for all times. The same holds for the Ward identities as generated
by commutators of Gauss operators. The constraint dynamical equations are
highly non-perturbative and thus applicable also in the strong coupling regime,
as e.g. low-energy QCD problems.


title:
Quantum Effects in the Stochastic Behaviour of Nuclear Matter at Finite
  Excitations\FOOTNOTE

abstract:
  We examine the dynamics of statistical fluctuations in nuclear matter. Linear
response functions for the average phase space density are derived within
Landau theory. Properties of the stochastic forces are deduced from the quantal
fluctuation dissipation theorem, with a suitable generalization to unstable
modes. Sizable quantum effects are found both inside and outside the spinodal
regime.


title: Dynamics of Fragment Formation in the Nuclear Spinodal Region

abstract:
  The Vlasov-Nordheim equation is solved numerically on a lattice for nuclear
matter in two dimensions. We discuss the reliability of the model at normal
density and then study the response of the system to small perturbations. We
find deterministic chaos inside the spinodal zone where fragment formation
occurs. We discuss in detail the dynamical features of this phenomenon in order
to clarify the mechanisms leading to nuclear disassembly in heavy--ion
collisions.


title: Simultaneous Projectile-Target Excitation in Heavy Ion Collisions

abstract:
  We calculate the lowest-order contribution to the cross section for
simultaneous excitation of projectile and target nuclei in relativistic heavy
ion collisions. This process is, to leading order, non-classical and adds
incoherently to the well-studied semi-classical Weizs\"acker-Williams cross
section. While the leading contribution to the cross section is down by only
$1/Z_P$ from the semiclassical process, and consequently of potential
importance for understanding data from light projectiles, we find that phase
space considerations render the cross section utterly negligible.


title:
A Wilson Renormalization Group Approach to Light-Front Tamm-Dancoff
  Scalar Field Theory

abstract:
  A program to utilize the Tamm-Dancoff approximation, on the light-front, to
solve relativistic quantum field theories, is presented. We present a well
defined renormalization program for the Tamm-Dancoff approximation. This
renormalization program utilizes a Minkowski space version of Wilson's
renormalization group. We studied light-front $\phi^{4}$ field theory in 3+1
dimensions, within a two-particle truncation of Fock space. We further
simplified our calculations by considering only one marginal operator and one
irrelevant operator. The renormalization procedure required no more marginal or
relevant operators. We derived an effective, renormalized, Hamiltonian. These
techniques may be germane to the effort to find an effective, low energy,
light-front Hamiltonian for quantum chromodynamics. PACS number(s): 11.10Gh,
11.10Ef


title: On the Macroscopic Limit of Nuclear Dissipation

abstract:
  The Landau-Vlasov equation is applied to a slab of width $L$. This geometry
is introduced to simulate somehow the finiteness of real nuclei but to allow
for analytical solutions, nevertheless. We focus on the damping of low
frequency surface modes and discuss their friction coefficient. For this
quantity we study the macroscopic limit as defined by $L\to \infty$. We
demonstrate that the same result can be obtained for finite $L$ by applying an
appropriate frequency smoothing, if only the smearing interval is sufficiently
large. The apparent, but important consequences are discussed which this result
will have for the understanding of the nature of dissipation in real nuclei.


title: Inversion Potential Analysis of the Nuclear Dynamics in the Triton

abstract:
  We report 3H binding energy calculations using inversion potentials generated
from phase shifts corresponding to contemporary nucleon-nucleon potentials as
well as modern phase shift analyses. We place limits upon local potential
triton binding energy calculations due to the underlying uncertainties in their
fit to the nucleon-nucleon phase shifts: 7.7 +/- 0.2 MeV. We explore the role
of the nonlocality of momentum dependent potentials in the triton binding
energy. In particular, we find the additional binding energy in the case of the
Bonn-B potential is due to a long range nonlocality, which may correspond to a
three-nucleon force when the Hamiltonian is restricted to local interactions.


title: Production of Eta-Mesons in Collisions of Nucleons and Delta-Resonances

abstract:
  We calculate the cross section for the production of $\eta$-mesons via
\mbox{$\Delta N \to N N \eta$} in a relativistic One-Boson-Exchange-Model.
Using this cross section we then determine the probability for the production
of an $\eta$-meson by a $\Delta$-resonance moving in nuclear matter. The result
is compared to prescriptions in BUU-calculations in which \et-production
proceeds both through a direct channel and through the sequential process
$\Delta \to N \pi ; \pi N \to N \eta$.


title: Analysis of $\pi$d elastic scattering data to 500 MeV

abstract:
  An energy-dependent and a set of single-energy partial-wave analyses of
$\pi$d elastic scattering data have been completed. Amplitudes are presented
for pion laboratory kinetic energies up to 500~MeV. These results are compared
with those found in other recent analyses. We comment on the present database
and make suggestions for future work. ( Figures are available from the authors
upon request. )


title: Heavy Quarkonia in the Instantaneous Bethe-Salpeter Model

abstract:
  The heavy quarkonia (Charmonium \(c\bar{c}\) and Bottomonium \(b\bar{b}\))
are investigated in the framework of the instantaneous BS-equation (Salpeter
equation). We parametrize confinement alternatively by a linearly rising scalar
or a vector interaction kernel and take into account the one-gluon-exchange
(OGE) interaction in the instantaneous approximation. Mass spectra as well as
leptonic, two-photon, E1 and M1 decay widths are calculated. Our results show
that a reasonable description of the experimental data can be obtained with
both spin structures for the confining kernel. The relativistic treatment leads
to an improved description compared to nonrelativistic results for the
two-photon width of the \(\eta_c\) and to some extent for the E1-transition
widths. However, characteristic deviations indicate that within a relativistic
framework confinement is not described adequately by a potential.


title: Chiral perturbation in dense matter and meson condensation controversy

abstract:
  An outstanding problem in the study of possible kaon condensation is the
striking discrepancy between the results of chiral perturbation theory and
those of the PCAC-plus-current-algebra approach. I discuss here what causes
this discrepancy and what needs to be done to solve the problem. In addition, I
point out the importance of examining the validity of the non-relativistic
approximation universally employed in the existing treatments of kaon
condensation.


title: An updated analysis of NN elastic scattering data to 1.6 GeV

abstract:
  An energy-dependent and set of single-energy partial-wave analyses of $NN$
elastic scattering data have been completed. The fit to 1.6~GeV has been
supplemented with a low-energy analysis to 400 MeV. Using the low-energy fit,
we study the sensitivity of our analysis to the choice of $\pi NN$ coupling
constant. We also comment on the possibility of fitting $np$ data alone. These
results are compared with those found in the recent Nijmegen analyses. (Figures
may be obtained from the authors upon request.)


title:
Flow of Nucleons and Fragments in 40Ar + 27Al Collisions Studied with
  AMD

abstract:
  Collective transverse momentum flow of nucleons and fragments in intermediate
energy 40Ar + 27Al collisions is calculated with the antisymmetrized molecular
dynamics (AMD). The observed flow and its balance energy are reproduced very
well by the calculation with the Gogny force which corresponds to the soft EOS
of the nuclear matter. Especially the calculated absolute value of the fragment
flow is larger than that of the nucleon flow in the negative flow region, which
can be explained by the existence of two components of flow. In addition to
many similarities, difference in the deuteron flow is found between 12C + 12C
and 40Ar + 27Al collisions, and its origin is investigated by paying attention
to the production mechanism of light fragments. We also investigate the
dependence of the flow of nucleons and fragments on the stochastic collision
cross section and the effective interaction, and conclude that the stiff EOS
without momentum dependence of the mean field is not consistent to the
experimental data.


title:
Effects of nuclear structure on average angular momentum in subbarrier
  fusion

abstract:
  We investigate the effects of nuclear quadrupole and hexadecapole couplings
on the average angular momentum in sub-barrier fusion reactions. This quantity
could provide a probe for nuclear shapes, distinguishing between prolate vs.
oblate quadrupole and positive vs. negative hexadecapole couplings. We describe
the data in the O + Sm system and discuss heavier systems where shape effects
become more pronounced.


title: A gauge invariant unitary theory for pion photoproduction

abstract:
  The Ward-Takahashi identities are central to the gauge invariance of the
photoproduction amplitude. Here we demonstrate that unitarity and in particular
the inclusion of both the $\pi N$ and $\gamma\pi N$ thresholds on equal footing
yields a photoproduction amplitude that satisfies both two-body unitarity and
the generalized Ward-Takahashi identities. The final amplitude is a solution of
a set of coupled channel integral equations for the reactions $\pi
N\rightarrow\pi N$ and $\gamma N\rightarrow\pi N$. % Figures available from the
authors upon request, % e-mail: phchv@pippin.cc.flinders.edu.au % Submitted to
Physical Review C


title: Essential Strangeness in Nucleon Magnetic Moments

abstract:
  Effective quark magnetic moments are extracted from experimental measurements
as a function of the strangeness magnetic moment of the nucleon. Assumptions
made in even the most general quark model analyses are ruled out by this
investigation. Ab initio QCD calculations demand a non-trivial role for strange
quarks in the nucleon. The effective moments from QCD calculations are
reproduced for a strangeness magnetic moment contribution to the proton of 0.11
$\mu_N$, which corresponds to $F_2^s(0) = -0.33\ \mu_N$.


title:
Low energy theorem for scalar and vector interactions of a composite
  spin-1/2 system

abstract:
  Scalar and vector interactions, with the scalar interaction coupled to a
composite spin-1/2 system so as to cause a shift of its mass, are shown to obey
a low-energy theorem which guarantees that the second order interaction due to
z-graphs is the same as for a point Dirac particle. Off-shell and contact
interactions appropriate to the composite system cancel and this is verified in
a model of a composite fermion. The result provides a justification for the use
of the Dirac equation as it has been in relativistic nuclear scattering and
mean field theories.


title: Pion Cloud Contribution to K+ Nucleus Scattering

abstract:
  A careful reanalysis is done of the contribution to $K^{+}$ nucleus
scattering from the interaction of the kaon with the virtual pion cloud. The
usual approximations made in the evaluation of the related kaon selfenergy are
shown to fail badly. We also find new interaction mechanisms which provide
appreciable corrections to the kaon selfenergy. Some of these contribute to the
imaginary part below pion creation threshold. The inclusion of these new
mechanisms in the inelastic part of the optical potential produces a
significant improvement in the differential and total $K^{+}$ nuclear cross
sections. Uncertainties remain in the dispersive part of the optical potential.


title: The Be7(p,gamma)B8 cross section and the properties of Be7

abstract:
  We study the nonresonant part of the $^7$Be($p,\gamma$)$^8$B reaction using a
three-cluster resonating group model that is variationally converged and
virtually complete in the $^4$He+$^3$He+$p$ model space. The importance of
using adequate nucleon-nucleon interaction is demonstrated. We find that the
low-energy astrophysical $S$-factor is linearly correlated with the quadrupole
moment of $^7$Be. A range of parameters is found where the most important
$^7$Be and $^7$Li properties are reproduced simultaneously; the corresponding
$S$-factor at $E_{\rm cm}=20$ keV is $24.6-26.1$ eV$\cdot$b.


title: Loosely bound hyperons in the SU(3) Skyrme model

abstract:
  Hyperon pairs bound in deuteron like states are obtained within the SU(3)
Skyrme model in agreement with general expectations from boson exchange models.
The central binding from the flavor symmetry breaking terms increases with the
strangeness contents of the interacting baryons whereas the kinetic non-linear
$\sigma$-model term fixes the spin and isospin of the bound pair. We give a
complete account of the interactions of octet baryons within the product
approximation to baryon number $B=2$ configurations.


title:
A Microscopic T-Violating Optical Potential: Implications for
  Neutron-Transmission Experiments

abstract:
  We derive a T-violating P-conserving optical potential for neutron-nucleus
scattering, starting from a uniquely determined two-body $\rho$-exchange
interaction with the same symmetry. We then obtain limits on the T-violating
$\rho$-nucleon coupling $\overline{g}_{\rho}$ from neutron-transmission
experiments in $^{165}$Ho. The limits may soon compete with those from
measurements of atomic electric-dipole moments.


title: Color Transparency Effects in Quasi-elastic Nuclear Reactions

abstract:
  Previous work on color transparency is reviewed briefly with an emphasis on
aspects related to an upgrade of CEBAF.


title: Pion interferometry with pion-source-medium interactions

abstract:
  An extended pion source, which can be temporarily created by a high energy
nuclear collision, will also absorb and distort the outgoing pions. We discuss
how this effect alters the interferometric pattern of the two-pion momentum
correlation function. In particular, we show that the two-pion correlation
function decreases rapidly when the opening angle between the pions increases.
The opening-angle dependence should serve as a new means of obtaining
information about the pion source in the analysis of experimental data.


title:
Inclusive Aand Semi-Inclusive Deep Inelastic Scattering at Cebaf at
  Higher Energies

abstract:
  We summarize the discussion on the possibilities of doing inclusive and
semi-inclusive deep inelastic scattering experiments at CEBAF with beam energy
of the order of 10 GeV.


title: Exotic Atom Formation in External Electric Fields

abstract:
  Validity of the coalescence model of exotic atom formation in the ion
collisions is studied . An estimate is given for the rates of P state
production in the electric fields of the colliding ions . Possibilities of
quantum beat effects are indicated . The results may be of interest in the
experimental search for pionium.


title:
The Spin-Dependent Structure Functions of Nuclei in the Meson-Nucleon
  Theory

abstract:
  A theoretical approach to the investigation of spin-dependent structure
functions in deep inelastic scattering of polarized leptons off polarized
nuclei, based on the effective meson-nucleon theory and operator product
expansion method, is proposed and applied to deuteron and $^3He$. The explicit
forms of the moments of the deuteron and $^3He$ spin-dependent structure
functions are found and numerical estimates of the influence of nuclear
structure effects are presented.


title:
Higher Order Processes in Electromagnetic Production of Electron
  Positron Pairs in Relativistic Heavy Ion Collisions

abstract:
  We study higher-order effects in the electromagnetic production of
electron-positron pairs in relativistic heavy ion collisions. Treating the
field of the heavy ions as an external field and neglecting the interaction
among electrons and positrons, we show that the $N$-pair creation amplitude is
the antisymmetrised product of $N$ one-pair creation amplitudes and the vacuum
amplitude. Neglecting contributions coming from exchange terms, we show that
the total probability for $N$ pairs is approximately a Poisson distribution. We
investigate further the structure of the reduced one-pair amplitude,
concentrating especially on multiple-particle corrections. We calculate the
first of these corrections in second order Magnus theory based on our previous
result in second-order Born approximation for impact parameter $b$ zero.
Explicit calculations show that the total probability is increased up to 10 \%
by this correction for realistic collider parameters. The calculations can also
be used to confirm the use of the Poisson distribution for the total
probability.


title:
Simple classification of final state interaction effects in
  $^4He(e,e'p)$ scattering

abstract:
  The radius of interaction between the struck proton and spectator nucleons is
close to the radius of short-distance two-nucleon correlations in nuclear
matter, which makes final state interaction(FSI) an important background to
production of protons with large missing momentum. We present a simple
classification of the dominant FSI effects in $^4He(e,e'p)$ scattering and
identify parts of the phase space dominated by FSI. At large missing momentum,
FSI leads to a striking angular anisotropy of the missing momentum
distribution, which has a prominent peak in transverse kinematics and smaller,
forward-backward asymmetric, peaks in parallel kinematics.


title: Muon to Electron Conversion; A Symbiosis of Particle and Nuclear Physics

abstract:
  $\mu-e$ conversion is the experimentally most interesting lepton flavor
violating process. From a theoretical point of view it is an interesting
interplay of particle and nuclear physics. The effective transition operator,
depending on the gauge model, is in general described in terms of a combination
of four terms of transition operators (isoscalar and isovector, Fermi-like as
well as axial vector-like). The experimentally most interesting ground state to
ground state transition is adequately described in terms of the usual proton
and neutron form factors. These were computed in both the shell model and RPA.
Since it is of interest to know the portion of the strength exhausted by the
coherent (ground state to ground state) transition, the total transition rate
to all final states must also be computed. This was done i) in RPA by
explicitly summing over all final states ii) in the context of the closure
approximation (using shell model and RPA for constructing the initial state)
and iii) in the context of nuclear matter mapped into nuclei via a local
density approximation. We found that, apart from small local oscillations, the
conversion rate keeps increasing from light to heavy nuclear elements. We also
find that the coherent mode is dominant (it exhausts more than 90\% of the sum
rule). Various gauge models are discussed. In general the predicted branching
ratio is much smaller compared to the present experimental limit.


title:
Resonance Model for $\pi$N Scattering and $\eta$-Meson Production in the
  s$_{11}$ Channel

abstract:
  A model for $\pi$N scattering and $\eta$-meson production in the S$_{11}$
channel is presented. The model includes $\pi$N-scattering Born terms as well
as the N$^*${} resonances S$_{11}$(1535) and S$_{11}$(1610). The $T$-matrix is
computed in the $K$-matrix approximation. The parameters of the model are
determined by fitting the elastic $\pi$N-scattering $T$-matrix to empirical
data. We find an excellent fit for all energies up to $\sqrt{s}$ = 1.75 GeV.
Furthermore, a good description of the cross section for $\pi^- + p \rightarrow
\eta + n$ is obtained without further adjustment of parameters.


title: Electromagnetic Form Factor of the Nucleon in the Time-like Region

abstract:
  We explore the possibility to verify vector meson dominance for the nucleon
by measuring the half-off-shell form factor in the vector-meson mass region.
Cross sections for the process $\gamma p \rightarrow p + e^+e^-$ be presented.


title: Fermion to boson mappings revisited

abstract:
  We briefly review various mappings of fermion pairs to bosons, including
those based on mapping operators, such as Belyaev-Zelevinskii, and those on
mapping states, such as Marumori; in particular we consider the work of
Otsuka-Arima-Iachello, aimed at deriving the Interacting Boson Model. We then
give a rigorous and unified description of state-mapping procedures which
allows one to systematically go beyond Otsuka-Arima-Iachello and related
approaches, along with several exact results.


title: Many-body effects in 16O(e,e'p)

abstract:
  Effects of nucleon-nucleon correlations on exclusive $(e,e'p)$ reactions on
closed-shell nuclei leading to single-hole states are studied using
$^{16}O(e,e'p)^{15}N$ ($6.32$ MeV, $3/2^-$) as an example. The quasi-hole wave
function, calculated from the overlap of translationally invariant many-body
variational wave functions containing realistic spatial, spin and isospin
correlations, seems to describe the initial state of the struck proton
accurately inside the nucleus, however it is too large at the surface. The
effect of short-range correlations on the final state is found to be largely
cancelled by the increase in the transparency for the struck proton. It is
estimated that the values of the spectroscopic factors obtained with the DWIA
may increase by a few percent due to correlation effects in the final state.


title: An accurate nucleon-nucleon potential with charge-independence breaking

abstract:
  We present a new high-quality nucleon-nucleon potential with explicit charge
dependence and charge asymmetry, which we designate Argonne $v_{18}$. The model
has a charge-independent part with fourteen operator components that is an
updated version of the Argonne $v_{14}$ potential. Three additional
charge-dependent and one charge-asymmetric operators are added, along with a
complete electromagnetic interaction. The potential has been fit directly to
the Nijmegen $pp$ and $np$ scattering data base, low-energy $nn$ scattering
parameters, and deuteron binding energy. With 40 adjustable parameters it gives
a $\chi^{2}$ per datum of 1.09 for 4301 $pp$ and $np$ data in the range 0--350
MeV.


title:
Limits on the Domain of Coupling Constants for Binding N-Body Systems
  with No Bound Subsystems

abstract:
  We study the domain of coupling constants for which a 3-body or 4-body system
is bound while none of its subsystems is bound. Limits on the size of the
domain are derived from a variant of the Hall--Post inequalities which relate
$N$-body to $(N-1)$-body energies at given coupling. Possible applications to
halo nuclei and hypernuclei are briefly outlined.


title:
Effects of Compression and Collective Expansion on Particle Emission
  from Central Heavy-Ion Reactions

abstract:
  Conditions under which compression occurs and collective expansion develops
in energetic reactions of heavy nuclei, are analyzed, together with their
effects on emitted light baryons and pions. Within transport simulations, it is
shown that shock fronts perpendicular to beam axis form in head-on reactions.
The fronts separate hot compressed matter from normal. As impact parameter
increases, the angle of inclination of the fronts relative to beam axis
decreases, and in-between the fronts a weak tangential discontinuity develops.
Hot matter exposed to the vacuum in directions perpendicular to shock motion
(and parallel to fronts), starts to expand sideways, early within reactions.
Expansion in the direction of shock motion follows after the shocks propagate
through nuclei, but due to the delay does not acquire same strength. Expansion
affects angular distributions, mean-energy components, shapes of spectra and
mean energies of different particles emitted into any one direction, and
further particle yields. Both the expansion and a collective motion associated
with the weak discontinuity, affect the magnitude of sideward flow within
reaction plane. Differences in mean particle energy components in and out of
the reaction plane in semicentral collisions, depend sensitively on the
relative magnitude of shock speed in normal matter and speed of sound in hot
matter.


title: Collapse of Flux Tubes

abstract:
  The dynamics of an idealized, infinite, MIT-type flux tube is followed in
time as the interior evolves from a pure gluon field to a $\overline q \ q$
plasma. We work in color U(1). $\overline q\ q$ pair formation is evaluated
according to the Schwinger mechanism using the results of Brink and Pavel. The
motion of the quarks toward the tube endcaps is calculated by a Boltzmann
equation including collisions. The tube undergoes damped radial oscillations
until the electric field settles down to zero. The electric field stabilizes
the tube against pinch instabilities; when the field vanishes, the tube
disintegrates into mesons. There is only one free parameter in the problem,
namely the initial flux tube radius, to which the results are very sensitive.
Among various quantities calculated is the mean energy of the emitted pions.


title: Collective Excitations and Ground State Correlations

abstract:
  A generalized RPA formalism is presented which treats pp and ph correlations
on an equal footing. The effect of these correlations on the single-particle
Green function is discussed and it is demonstrated that a self-consistent
treatment of the single-particle Green function is required to obtain stable
solutions. A simple approximation scheme is presented which incorporates for
this self-consistency requirement and conserves the number of particles.
Results of numerical calculations are given for $^{16}$O using a G-matrix
interaction derived from a realistic One-Boson-Exchange potential.


title: Comparison of $K^+$ and $e^-$ Quasielastic Scattering

abstract:
  We formulate $K^+$-nucleus quasielastic scattering in a manner which closely
parallels standard treatments of $e^-$-nucleus quasielastic scattering. For
$K^+$ scattering, new responses involving scalar contributions appear in
addition to the Coulomb (or longitudinal) and transverse $(e,e')$ responses
which are of vector character. We compute these responses using both nuclear
matter and finite nucleus versions of the Relativistic Hartree Approximation to
Quantum Hadrodynamics including RPA correlations. Overall agreement with
measured $(e,e')$ responses and new $K^+$ quasielastic scattering data for
$^{40}$Ca at $|\qs|=500$ MeV/c is good. Strong RPA quenching is essential for
agreement with the Coulomb response. This quenching is notably less for the
$K^+$ cross section even though the new scalar contributions are even more
strongly quenched than the vector contributions. We show that this
``differential quenching'' alters sensitive cancellations in the expression for
the $K^+$ cross section so that it is reduced much less than the individual
responses. We emphasize the role of the purely relativistic distinction between
vector and scalar contributions in obtaining an accurate and consistent
description of the $(e,e')$ and $K^+$ data within the framework of our nuclear
structure model.


title: Quantum Statistical Correlations for Slowly Expanding Systems

abstract:
  Quantum statistical correlations and momentum distributions are calculated
for a spherically symmetric, three-dimensionally expanding finite fireballs,
for non-relativistic expansions applying plane-wave approximation. The new
concepts of the geometrical temperature as well as the thermal radius are
presented for the simplest case. The symmetry properties of the correlation
function are shown to reflect the symmetry properties of the emission function.


title: Gribov Confinement and Chiral Perturbation Theory

abstract:
  I discuss the chiral dynamics of Gribov's theory of confinement. At a
critical coupling $\alpha_s^c$ the light quark vacuum undergoes a series of
phase transitions which should be taken into account in the application of
chiral perturbation theory. The Gribov theory offers a simple explanation of
the value of the pion nucleon sigma term without need to invoke a large strange
quark component in the nucleon.


title:
Consistent description of magnetic dipole properties in transitional
  nuclei

abstract:
  It is shown that a consistent description of magnetic dipole properties in
transitional nuclei can be obtained in the interacting boson model-2 by F-spin
breaking mechanism, which is associated with differences between the proton and
neutron deformations. In particular, the long standing anomalies observed in
the $g$-factors of the Os-Pt isotopes are resolved by a proper inclusion of
F-spin breaking.


title:
The $\pi \pi$ S-Wave in the 1 to 2 GeV Region from a $\pi \pi$,
  $\bar{K}K$ and $\rho \rho$($\omega \omega$) Coupled Channel Model

abstract:
  A simple $\pi \pi$, $\bar{K}K$, and $\rho \rho$($\omega \omega$) fully
coupled channel model is proposed to predict the isoscalar S-wave phase shifts
and inelasticities for $\pi \pi$ scattering in the 1.0 to 2.0 GeV region. The
S-matrix is required to exhibit poles corresponding to the established
isoscalar J$^{\pi}$ = 0$^+$ resonances f$_0$(975), f$_0$(1400), and
f$_0$(1710). A dominant feature of the experimental $\pi \pi$ inelasticity is
the clear opening of the $\bar{K}K$ channel near 1 GeV, and the opening of
another channel in the 1.4 - 1.5 GeV region. The success of our model in
predicting this observed dramatic energy dependence indicates that the effect
of multi-pion channels is adequately described by the $\pi \pi$ coupling to the
$\bar{K}K$ channel, the $\rho \rho$(4$\pi$) and $\omega \omega$(6$\pi$)
channels.


title: Temperature dependence of the nuclear symmetry energy

abstract:
  We have studied the properties of A=54 and A=64 isobars at temperatures T
\leq 2 MeV via Monte Carlo shell model calculations with two different residual
interactions. In accord with empirical indications, we find that the symmetry
energy coefficient, b_{sym}, is independent of temperature to within 0.6 MeV
for T \leq 1 MeV. This is in contrast to a recent suggestion of a 2.5 MeV
increase of b_{sym} for this temperature, which would have significantly
altered the supernova explosion scenario.


title:
Nearby Doorways, Parity Doublets and Parity Mixing in Compound Nuclear
  States

abstract:
  We discuss the implications of a doorway state model for parity mixing in
compound nuclear states. We argue that in order to explain the tendency of
parity violating asymmetries measured in $^{233}$Th to have a common sign,
doorways that contribute to parity mixing must be found in the same energy
neighbourhood of the measured resonance. The mechanism of parity mixing in this
case of nearby doorways is closely related to the intermediate structure
observed in nuclear reactions in which compound states are excited. We note
that in the region of interest ($^{233}$Th) nuclei exhibit octupole
deformations which leads to the existence of nearby parity doublets. These
parity doublets are then used as doorways in a model for parity mixing. The
contribution of such mechanism is estimated in a simple model.


title:
The Axial Charge Renormalization in a Relativistic Description of Finite
  Nuclei

abstract:
  Starting from a realistic One-Boson-Exchange model of the nucleon nucleon
interaction the relativistic mean field for nucleons is determined within the
Dirac Brueckner Hartree Fock approach for finite nuclei. The matrix elements of
the axial charge operator evaluated for the solutions of the Dirac equation
with this selfenergy are investigated. These matrix elements are enhanced with
respect to the equivalent non relativistic ones obtained from the solutions of
the Schr\"odinger equation with the non relativistic equivalent potential. The
present results confirm at a qualitative level the results for the axial charge
renormalization obtained with perturbative approaches. However, the results
obtained differ in size from those of the perturbative approach and are nucleus
and state dependent.


title: Nucleation of Quark--Gluon Plasma from Hadronic Matter

abstract:
  The energy densities achieved during central collisions of large nuclei at
Brookhaven's AGS may be high enough to allow the formation of quark--gluon
plasma. Calculations based on relativistic nucleation theory suggest that rare
events, perhaps one in every 10$^2$ or 10$^3$, undergo the phase transition.
Experimental ramifications may include an enhancement in the ratio of pions to
baryons, a reduction in the ratio of deuterons to protons, and a larger source
size as seen by hadron interferometry.


title: Two-Body Correlations in Pionic Systems

abstract:
  In close analogy to fermionic many-body theory the truncation of the bosonic
BBGKY density matrix hierarchy on the two-body level leads to a coupled set of
nonlinear equations of motion for the one-body density matrix and the two-body
correlation function. These equations provide a nonperturbative description of
the nonequilibrium time evolution of particle number conserving bosonic
many-body systems including the dynamical resummation of parquet-like diagrams.
Within this framework we study the properties of a pionic system as a function
of temperature and density with focus on two-body quantities. For each
temperature we find a related pion density for which the relative strength of
the two-body correlation function assumes a maximum and the pionic system is
far from the mean-field limit. Since these correlated phases up to $T$=200 MeV
only appear at rather low pion density, the hot and dense pion gas as generated
in ultrarelativistic nucleus-nucleus collisions should be well described within
mean-field theory; i.e. the HBT analysis of pion sources from $\pi-\pi$
correlations should remain valid even in the case of strongly interacting
pions.


title:
The Determination of Nuclear Level Densities from Experimental
  Information -

abstract:
  A novel Information Theory based method for determining the density of states
from prior information is presented. The energy dependence of the density of
states is determined from the observed number of states per energy interval and
model calculations suggest that the method is sufficiently reliable to
calculate the thermal properties of nuclei over a reasonable temperature range.


title: Comment on ``Specific Heat and Shape Transitions in Light sd Nuclei''

abstract:
  This comment re-examines the origin of structure seen in the computed
specific heat of finite nuclei. In a recent paper, Civitarese and Schvellinger
suggest that such structure is due to model-space truncation in the
calculations. We reaffirm our conclusion that the structure is caused by a
collective-to-non-collective phase transformation at low temperatures, signaled
by a change in the nuclear level density below 10 MeV excitation energy.


title: Chiral Symmetry in Nuclear Physics

abstract:
  The role of chiral symmetry in nuclear physics is summarized. The topics
treated are the chiral bag model for nucleon structure resulting from large
$N_c$ QCD, the pion cloud in chiral perturbation theory for low-energy
electroweak nuclear response functions, ``swelled hadrons" in nuclear matter,
chiral symmetry restoration in terms of the Georgi vector limit and
pseudo-Goldstone meson condensation in nuclear medium.


title: Response Functions from Integral Transforms with a Lorentz Kernel

abstract:
  We propose to calculate inelastic response functions from the inversion of
their integral transform with a Lorentz kernel. The transform can be obtained
using bound-state type methods. Thus one does not need to solve the much more
complicated continuum problem with many open channels. Contrary to other
integral transforms considered in the literature, the inversion leads to
results of excellent accuracy and stability. This is explicitly shown for the
longitudinal deuteron response.


title:
Study of 3he(e,e') Longitudinal Response Functions with the
  Integral-Transform Method

abstract:
  The method of integral transforms is first applied for studying the $^3$He
longitudinal response functions. The transforms are calculated from localized
bound-state-type solutions to an inhomogenous Schr\"odinger-type three-body
equation. Several versions of local $s$-wave spin-dependent potentials
supplemented with a singlet $p$-wave potential and with the proton-proton
Coulomb interaction are used as a two-nucleon input. The conventional charge
density operator is utilized. The three-body equations are solved with a high
acuracy. It is found that the contribution of the $T=3/2$ final states to the
problem is suppressed and it amounts about 15\%. This might be ascribed to
symmetry requirements. The contributions of the $p$-wave $NN$ interaction and
of the Coulomb interaction are found to amount several per cent. Uncertainty
due to different choices of $s$-wave $NN$ forces is of a similar magnitude
provided that the low-energy $NN$ data are properly described. The results are
compared with the integral transforms of the experimental response functions.
For $q=300$ MeV/c experimental and theoretical results coincide within their
uncertainties. For $q=500$ MeV/c a noticeable difference is detected.


title:
Perturbative versus Lattice QCD Energy Density Correlators at High
  Temperatures

abstract:
  Correlators of magnetic and electric field energy density are investigated
for SU($N_c$) gauge theory at high temperatures $T$. At separations $z\leq 2/T$
the correlators are shown to be dominated by a power--law behavior even for
finite gluon screening masses. This continuum behavior is well approximated on
current $4\times 16^3$--lattices in the perturbative limit and leads to a
considerable overestimate of screening masses deduced from fitting the lattice
correlators with conventional exponential forms. The use of extended sources
and sinks to enhance the signal improves the situation for screening masses
$m\gg T$ but leads to a largely uncontrolled error for masses less than $T$. In
fact, we show that recent lattice QCD data of Grossmann et al., from which a
magnetic screening mass $m_M \approx 2.9 \, T$ was deduced, may even be
consistent with a vanishing actual magnetic screening mass.


title: Open Charm as a Probe of Pre-Equilibrium Dynamics in Nuclear Collisions?

abstract:
  The pre-equilibrium contribution to open charm production in nuclear
collisions at $\sqrt{s}=200$ AGeV is calculated using three different models
for the correlations between momentum and space-time coordinates. Ideal
(Bjorken) correlation between the rapidity $y$ and space-time rapidity $\eta$
of mini-jet gluons suppresses greatly the pre-equilibrium yield and even
allowing for the minimal uncertainty correlations leads, in contrast to
previous estimates, only to a small pre-equilibrium charm yield as compared to
initial yield due to gluon fusion. The ``intrinsic'' charm process is
negligible in the mid-rapidity domain.