title: On the possibility of fusion reactions in water molecules

abstract:
  The probability of nuclear transitions $p+p+{}^{16}{O} \, \rightarrow \,
{}^{18}{Ne}\, (4.522,1^-)$ in molecular water is estimated. Due to the
practically exact agreement of the energy of the $Ne$ resonance and of the
$p+p+{}^{16}{O}$ threshold, the transition probability is found to be
considerably enhanced. This indicates the possibility of nuclear fusion in
rotationally excited $H_2O$ molecules in the state $1^-$.


title: Non-perturbative Gluons and Pseudoscalar Mesons in Baryon Spectroscopy

abstract:
  We study baryon spectroscopy including the effects of pseudoscalar meson
exchange and one gluon exchange potentials between quarks, governed by
$\alpha_s$. The non-perturbative, hyperspherical method calculations show that
one can obtain a good description of the data by using a quark-meson coupling
constant that is compatible with the measured pion-nucleon coupling constant,
and a reasonably small value of $\alpha_s$.


title: On the IMF Multiplicity in Au+Au Reactions

abstract:
  Intermediate mass fragment (IMF) multiplicity has been investigated for Au+Au
reactions at incident energies of 100, 250 and 400 MeV/A. From the analysis of
the impact-parameter-dependence of the IMF multiplicity using our QMD plus
statistical evaporation model, we found that 1) statistical decay process
modifies the results greatly, and 2) the Fermi motion plays a role to increase
the IMF multiplicity for whole impact-parameter range.


title: Neural Networks for Impact Parameter Determination

abstract:
  An accurate impact parameter determination in a heavy ion collision is
crucial for almost all further analysis. The capabilities of an artificial
neural network are investigated to that respect. A novel input generation for
the network is proposed, namely the transverse and longitudinal momentum
distribution of all outgoing (or actually detectable) particles. The neural
network approach yields an improvement in performance of a factor of two as
compared to classical techniques. To achieve this improvement simple network
architectures and a 5 by 5 input grid in (p_t,p_z) space are sufficient.


title: Does The 3N-Force Have A Hard Core?

abstract:
  The meson-nucleon dynamics that generates the hard core of the RuhrPot
two-nucleon interaction is shown to vanish in the irreducible 3N force. This
result indicates a small 3N force dominated by conventional light
meson-exchange dynamics and holds for an arbitrary meson-theoretic Lagrangian.
The resulting RuhrPot 3N force is defined in the appendix. A completely
different result is expected when the Tamm-Dancoff/Bloch-Horowitz procedure is
used to define the NN and 3N potentials. In that approach, (e.g. full Bonn
potential) both the NN {\it and} 3N potentials contain non-vanishing
contributions from the coherent sum of meson-recoil dynamics and the
possibility of a large hard core requiring explicit calculation cannot be ruled
out.


title:
Pion production in proton-proton collisions in a covariant one boson
  exchange model

abstract:
  Motivated by the renewed interest in studying the pion production on nuclei
with protons at few GeV incident energies, we investigate the pion production
in proton-proton collisions over an energy range of 300 $MeV$ to 2 $GeV$.
Starting from a realistic one-boson exchange model with parameters fitted to
the amplitudes of the elastic nucleon-nucleon scattering, we perform fully
covariant calculations for the total, double and triple differential
cross-sections of the $p(p,n\pi^+)p$ and $p(p,p\pi^0)p$ reactions. The
calculations incorporate the exchange of $\pi, \rho,\omega$ and $\sigma$ mesons
and treat nucleon and delta isobar as intermediate states. We obtain a
reasonably good agreement with the experimental data in the entire range of
beam energies. The form of the covariant delta propagator, the cut-off
parameter for the $\pi NN$ and $\pi N\Delta$ vertex form factors and the energy
dependence of the delta isobar decay width is investigated.


title:
Relativistic deformed mean-field calculation of binding energy
  differences of mirror nuclei

abstract:
  Binding energy differences of mirror nuclei for A=15, 17, 27, 29, 31, 33, 39
and 41 are calculated in the framework of relativistic deformed mean-field
theory. The spatial components of the vector meson fields and the photon are
fully taken into account in a self-consistent manner. The calculated binding
energy differences are systematically smaller than the experimental values and
lend support to the existency of the Okamoto--Nolen-Schiffer anomaly found
decades ago in nonrelativistic calculations. For the majority of the nuclei
studied, however, the results are such that the anomaly is significantly
smaller than the one obtained within state-of-the-art nonrelativistic
calculations.


title: Photoproduction of vector mesons off nucleons near threshold

abstract:
  We propose a simple meson-exchange model of the photoproduction of $\rho$-
and $\omega$-mesons off protons near threshold ($E_\gamma$ less than 2 GeV).
This model provides a good description of the available data and implies a
large $\rho$-nucleon interaction in the scalar channel ($\sigma$-exchange). We
use this phenomenological interaction to estimate the leading contribution to
the self-energy of $\rho$-mesons in matter. The implications of our calculation
for experimental studies of the $\rho$-meson mass in nuclei are discussed.


title: Quarkonium Interactions in QCD

abstract:
  Contents: 1. Introduction 2. Operator Product Expansion for Quarkonium
Interactions 3. Scale Anomaly, Chiral Symmetry and Low-Energy Theorems 4.
Quarkonium Interactions in Matter 5. Conclusions and Outlook


title: Isospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules

abstract:
  We use QCD sum rules for the three point function of a pseudoscalar and two
nucleonic currents in order to estimate the charge dependence of the pion
nucleon coupling constant $g_{NN\pi}$ coming from isospin violation in the
strong interaction. The effect can be attributed primarily to the difference of
the quark condensates $<{\bar u}u>$ and $<{\bar d}d>$. For the splitting
$(g_{pp\pi_0} - g_{nn\pi_0}) / g_{NN\pi}$ we obtain an interval of $1.2 *
10^{-2}$ to $3.7 * 10^{-2}$, the uncertainties coming mainly from the input
parameters. The charged pion nucleon coupling is found to be the average of
$g_{pp\pi_0}$ and $g_{nn\pi_0}$. Electromagnetic effects are not included.


title:
Chiral symmetry amplitudes in the s-wave isoscalar and isovector
  channels and the $\sigma, f_0(980), a_0 (980)$ scalar mesons

abstract:
  We use a nonpertubative approach which combines coupled channel Lippmann
Schwinger equations with meson-meson potentials provided by the lowest order
chiral Lagrangian. By means of one parameter, a cut off in the momentum of the
loop integrals, which results of the order of 1 GeV, we obtain singularities in
the S-wave amplitudes corresponding to the $\sigma$, f_0 and a_0 resonances.
The $\pi \pi \to \pi \pi, \pi \pi \to K \bar{K}$ phase shifts and
inelasticities in the T = 0 scalar channel are well reproduced as well as the
$\pi^0 \eta$ and $K \bar{K}$ mass distributions in the T = 1 channel.
Furthermore, the total and partial decay widths of the f_0 and a_0 resonances
are properly reproduced including also the decay into the $\gamma \gamma$
channel. The results seem to indicate that chiral symmetry constraints at low
energy and unitarity in coupled channels is the basic information contained in
the meson-meson interaction below $\sqrt{s} \simeq 1.2 GeV$.


title: Pomeron exchange and exclusive electroproduction of rho-mesons in QCD

abstract:
  A Pomeron-exchange model of exclusive electroproduction of $\rho$-mesons is
examined using a dressed-quark propagator. It is shown that by representing the
photon-$\rho$-meson-Pomeron coupling by a nonperturbative, confined-quark loop,
one obtains predictions for $\rho$-meson electroproduction that are in good
agreement with experiment.


title: Semiclassical treatment of the Dirac sea contribution for finite nuclei

abstract:
  Dirac sea corrections for bulk properties of finite nuclei are computed
within a self-consistent scheme in the $\sigma$-$\omega$ model. The valence
part is treated in the Hartree approximation whereas the sea contribution is
evaluated semiclassically up to fourth order in $\hbar$. Numerically, we find a
quick convergence of the semiclassical expansion; the fourth order contributing
much less than one percent to the binding energy per nucleon.


title: The Doppler Paradigm and the APEX-EPOS-ORANGE Quandary

abstract:
  The experimental detection of the sharp lines of the \ee Puzzle is viewed as
a struggle against Doppler broadening. Gedanken experiments which are realistic
in zeroth order of detail are analyzed to show that the ORANGE and EPOS/I
geometries select narrower slices of a Doppler broadened line than spherically
inclusive (APEX and EPOS/II --like) apparati. Roughly speaking, the latter
require event-by-event Doppler reconstruction simply to regain an even footing
with the former. This suggests that APEX' or EPOS/II's coincident pair
distributions must be statistically superior to those of EPOS/I or ORANGE in
order to support a comparable inference about sharp structure. Under present
circumstances, independent alternative data is invaluable. Therefore, a
corroboration of Sakai's 330.1 keV ($<$ 3 keV wide) electron line in few MeV
$e^+$ or $e^-$ bombardments of U and Th targets could prove crucial.


title: The eta-meson light nucleus resonances and quasi-bound states

abstract:
  The position and movement of poles of the amplitude for elastic eta-meson
scattering off the light nuclei d, t, ^3He, and ^4He are studied. It is found
that, within the existing uncertainties for the elementary eta-N interaction,
all these nuclei can support a quasi-bound state. The values of the eta-nucleus
scattering lengths corresponding to the critical eta-N interaction which
produces a quasi--bound state are given.


title: Neutral Meson Photoproduction in $SU_f(3)$ $\chi$PT

abstract:
  We present the results for the electric dipole amplitude for $\gamma N \to
\pi^0 N$ at threshold at the $O(p^2)$ level in SU$_f$(3) chiral perturbation
theory. We find that the SU$_f$(3) results differ only slightly from the
SU$_f$(2) results. At the $O(p^3)$ level one encounters new, unknown
counterterms to fix which one is likely to need the threshold photoproduction
data themselves, thus losing predictive power. We suggest, instead, that the
{\it difference} between the proton and neutron $\pi^0$ photoproduction
amplitudes may provide a test of the convergence properties of the $\chi$PT in
the present context. We urge that the neutron's electric dipole amplitude be
measured.


title: Finite-size Effects in Multiquark Droplets; An Anatomical Study

abstract:
  Strutinsky's averaging(SA) method is applied to multiquark droplets to
systematically extract the smooth part of the exact quantal energy and thereby
the shell correction energies. It is shown within the bag model that the
semi-phenomenological density of states expression given upto curvature order
is almost equivalent to the SA method. A comparative study of the bag model and
the relativistic harmonic oscillator potential for quarks is done to
investigate the quark mass dependence of the finite-size effects. It is found
that there is an important difference between these two cases, which may be
related to the presence/non-presence of the net spin-orbit effect.


title:
Medium modifications of the nucleon--deuteron break--up cross section in
  the Faddeev approach

abstract:
  The three--nucleon scattering problem in a nuclear medium is considered
within the Faddeev technique. In particular the deuteron break--up cross
section that governs the formation and the break--up reactions of deuterons
(NNN <-> Nd) in a nuclear environment is calculated at finite temperatures and
densities. A significant enhancement of the in--medium break--up cross section
with increasing density has been found.


title:
Astrophysical S-factor of the $^7$Be($p,\gamma)^8$B reaction from
  Coulomb dissociation of $^8$B

abstract:
  The Coulomb dissociation method to obtain the astrophysical S-factor,
$S_{17}(0)$, for the $^7$Be($p,\gamma)^8$B reaction at solar energies is
investigated by analysing the recently measured data on the breakup reaction
$^{208}$Pb$(^8$B,$^7$Be$~p)^{208}$Pb at 46.5 MeV/A beam energy. Breakup cross
sections corresponding to E1, $E2$ and $M1$ transitions are calculated with a
theory of Coulomb excitation that includes the effects of the Coulomb recoil as
well as relativistic retardation. The interplay of nuclear and Coulomb
contributions to the breakup process is studied by performing a full quantum
mechanical calculation within the framework of the distorted-wave Born
Approximation. In the kinematical regime of the present experiment, both
nuclear as well as Coulomb-nuclear interference processes affect the pure
Coulomb breakup cross sections very marginally. The $E2$ cross sections are
strongly dependent on the model used to describe the structure of $^8$B. The
value of $S_{17}(0)$ is deduced with and without $E2$ and $M1$ contributions
added to the $E1$ cross sections and the results are discussed.


title: Magnetic moment of the deuteron as probe of relativistic corrections

abstract:
  The calculation of the magnetic moment of the deuteron in the framework of
the Bethe--Salpeter approach is performed. The relativistic corrections are
calculated analytically and estimated numerically. It is shown that the main
contributions are due to partial waves with positive energies and $P$--waves. A
comparison with the non-relativistic schemes of calculations including mesonic
exchange currents is made.


title:
Excitation functions in central Au+Au collisions from SIS/GSI to
  AGS/Brookhaven

abstract:
  Using the relativistic transport model (ART), we predict the energy
dependence of the stopping power, maximum baryon and energy densities, the
population of resonance matter as well as the strength of the transverse and
radial flow for central Au+Au reactions at beam momentum from 2 to 12 GeV/c
available at Brookhaven's AGS. The maximum baryon and energy densities are
further compared to the predictions of relativistic hydrodynamics assuming the
formation of shock waves. We also discuss the Fermi-Landau scaling of the pion
multiplicity in these reactions.


title: Assessment of Triton Potential Energy

abstract:
  An assessment is made of the dominant features contributing to the triton
potential energy, with the objective of understanding qualitatively their
origins and sensitivities. Relativistic effects, short-range repulsion, and
OPEP dominance are discussed. A determination of the importance of various
regions of nucleon-nucleon separation is made numerically.


title: Nuclear Properties for Astrophysical Applications

abstract:
  We tabulate the ground-state odd-proton and odd-neutron spins and parities,
proton and neutron pairing gaps, binding energy, one- and two-neutron
separation energies, quantities related to beta-delayed one- and two-neutron
emission probabilities, beta-decay energy release and half-life with respect to
Gamow-Teller decay, one- and two-proton separation energies, and alpha-decay
energy release and half-life for 8979 nuclei ranging from oxygen-16 to Z = 136,
A = 339 and extending from the proton drip line to the neutron drip line.
Single-particle level diagrams and other quantities are also presented in
graphical form. The starting point of our present work is a study of nuclear
ground-state masses and deformations based on the finite-range droplet model
and folded-Yukawa single-particle potential published in a previous issue of
Atomic Data and Nuclear Data Tables. The beta-delayed neutron-emission
probabilities and Gamow-Teller beta-decay rates are obtained from a
quasi-particle random-phase approximation with single-particle levels and wave
functions at the calculated nuclear ground-state shapes as input quantities.


title: Standard Neutrino Spectrum from B-8 Decay

abstract:
  We present a systematic evaluation of the shape of the neutrino energy
spectrum produced by beta-decay of $^8$B. We place special emphasis on
determining the range of uncertainties permitted by existing laboratory data
and theoretical ingredients (such as forbidden and radiative corrections). We
review and compare the available experimental data on the
$^8$B$(\beta^+){}^8$Be$(2\alpha)$ decay chain. We analyze the theoretical and
experimental uncertainties quantitatively. We give a numerical representation
of the best-fit (standard-model) neutrino spectrum, as well as two extreme
deviations from the standard spectrum that represent the total (experimental
and theoretical) effective $\pm3\sigma$ deviations. Solar neutrino experiments
that are currently being developed will be able to measure the shape of the
$^8$B neutrino spectrum above about 5 MeV. An observed distortion of the $^8$B
solar neutrino spectrum outside the range given in the present work could be
considered as evidence, at an effective significance level greater than three
standard deviations, for physics beyond the standard electroweak model. We use
the most recent available experimental data on the Gamow--Teller strengths in
the $A=37$ system to calculate the $^8$B neutrino absorption cross section on
chlorine: $\sigma_{\rm Cl}=(1.14\pm0.11)\times10^{-42}$~cm$^2$ ($\pm3\sigma$
errors). The chlorine cross section is also given as a function of the neutrino
energy. The $^8$B neutrino absorption cross section in gallium is $\sigma_{\rm
Ga}=(2.46^{+2.1}_{-1.1})\times10^{-42}$ cm$^2$ ($\pm3\sigma$ errors).


title:
The Neutron Spin Structure Function from the Deuteron Data in the
  Resonance Region

abstract:
  Nuclear effects in the spin-dependent structure function $g_1$ of the
deuteron are studied in the kinematics of future experiments at CEBAF, ($\nu
\leq 3~GeV, ~Q^2 \leq 2~GeV^2$). The magnitude of nuclear effects is found to
be significantly larger than the one occurring in deep inelastic scattering
($\nu\to \infty, ~Q^2\to \infty$). A possibility to measure the neutron
structure functions in the CEBAF experiments with deuterium is analysed. It is
found that disregarding or improperly treating nuclear effects in the region of
nucleon resonances would lead to the ``extraction" of an unreliable function. A
procedure aimed at correctly extracting the neutron structure function from the
deuterium data is illustrated and conclusions about the experimental study of
the $Q^2$ dependence of the Gerasimov-Drell-Hearn Sum Rule for the neutron are
drawn.


title:
Collective T- and P- Odd Electromagnetic Moments in Nuclei with Octupole
  Deformations

abstract:
  Parity and time invariance violating forces produce collective P- and T- odd
moments in nuclei with static octupole deformation. Collective Schiff moment,
electric octupole and dipole and also magnetic quadrupole appear due to the
mixing of rotational levels of opposite parity and can exceed single-particle
moments by more than a factor of 100. This enhancement is due to two factors,
the collective nature of the intrinsic moments and the small energy separation
between members of parity doublets. The above moments induce T- and P- odd
effects in atoms and molecules. Experiments with such systems may improve
substantially the limits on time reversal violation.


title: Temperature Dependence of Pair Correlations in Nuclei in the Iron-Region

abstract:
  We use the shell model Monte Carlo approach to study thermal properties and
pair correlations in $^{54,56,58}$Fe and in $^{56}$Cr. The calculations are
performed with the modified Kuo-Brown interaction in the complete $1p0f$ model
space. We find generally that the proton-proton and neutron-neutron $J=0$
pairing correlations, which dominate the ground state properties of even-even
nuclei, vanish at temperatures around 1 MeV. This pairing phase transition is
accompanied by a rapid increase in the moment of inertia and a partial
unquenching of the M1 strength. We find that the M1 strength totally unquenches
at higher temperatures, related to the vanishing of isoscalar proton-neutron
correlations, which persist to higher temperatures than the pairing between
like nucleons. The Gamow-Teller strength is also correlated to the isoscalar
proton-neutron pairing and hence also unquenches at a temperature larger than
that of the pairing phase transition.


title: Kaon loops in pion photoproduction: Facts and fancy

abstract:
  We show that a recent claim of huge kaon loop corrections to the electric
dipole amplitude in neutral pion photoprodcution at threshold is incorrect. The
difference between the two and three flavor chiral perturbation theory
calculation is marginal and thus previous claims of a good understanding of
this reaction remain valid.


title: Using Faddeev Differential Equations to Calculate Three-Body Resonances

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


title: Color singlet suppression of quark-gluon plasma formation

abstract:
  The rate of quark-gluon plasma droplet nucleation in superheated hadronic
matter is calculated within the MIT bag model. The requirements of color
singletness and (to less extent) fixed momentum suppress the nucleation rate by
many orders of magnitude, making thermal nucleation of quark-gluon plasma
droplets unlikely in ultrarelativistic heavy-ion collisions if the transition
is first order and reasonably described by the bag model.


title:
Exchange Current Corrections to Neutrino-Nucleus Scattering. I. Nuclear
  Matter

abstract:
  Relativistic exchange current corrections to the impulse approximation in low
and intermediate energy neutrino--nucleus scattering are presented assuming
non--vanishing strange quark form factors for constituent nucleons. Two--body
exchange current operators which treat {\em all} $SU(3)$ vector and axial
currents on an equal footing are constructed by generalizing the soft--pion
dominance method of Chemtob and Rho. For charged current reactions, exchange
current corrections can reduce the impulse approximation results by 5 to 10 \%
depending on the nuclear density. A finite strange quark form factor may change
the total cross section for neutral current scattering by 20\% while exchange
current corrections are found to be sensitive to the nuclear density.
Implications on the current LSND experiment to extract the strange quark axial
form factor of the nucleon are discussed.


title: Derivative-Coupling Models and the Nuclear-Matter Equation of State

abstract:
  The equation of state of saturated nuclear matter is derived using two
different derivative-coupling Lagrangians. We show that both descriptions are
equivalent and can be obtained from the sigma-omega model through an
appropriate rescaling of the coupling constants. We introduce generalized forms
of this rescaling to study the correlations amongst observables in infinite
nuclear matter, in particular, the compressibility and the effective nucleon
mass.


title:
A Study of the $\pi B \to Y K $ reactions for Kaon Production in Heavy
  Ion Collisions

abstract:
  Parametrizations of total cross sections sufficient for all channels of the
$\pi B \rightarrow Y K$ reactions are completed using a resonance model. As
well as discussing the $\pi N \rightarrow \Lambda K$ reactions, which were not
presented in our previous publications, we present the differential cross
section for $\pi N \rightarrow \Lambda K$. This report also aims at presenting
supplementary discussions to our previous work.


title: Shell Model Monte Carlo Methods

abstract:
  We review quantum Monte Carlo methods for dealing with large shell model
problems. These methods reduce the imaginary-time many-body evolution operator
to a coherent superposition of one-body evolutions in fluctuating one-body
fields; the resultant path integral is evaluated stochastically. We first
discuss the motivation, formalism, and implementation of such Shell Model Monte
Carlo (SMMC) methods. There then follows a sampler of results and insights
obtained from a number of applications. These include the ground state and
thermal properties of {\it pf}-shell nuclei, the thermal and rotational
behavior of rare-earth and $\gamma$-soft nuclei, and the calculation of double
beta-decay matrix elements. Finally, prospects for further progress in such
calculations are discussed.


title:
Renormalized QRPA and double beta decay: a critical analysis of double
  Fermi transitions

abstract:
  The proton-neutron monopole Lipkin model, which exhibits some properties
which are relevant for those double beta decay ($\beta \beta$) transitions
mediated by the Fermi matrix elements, is solved exactly in the proton-neutron
two-quasiparticle space. The exact results are compared with the ones obtained
by using the Quasiparticle Random Phase (QRPA) and renormalized QRPA (RQRPA)
approaches. It is shown that the RQRPA violates the Ikeda Sum Rule and that
this violation may be common to any extension of the QRPA where scattering
terms are neglected in the participant one-body operators as well as in the
Hamiltonian. This finding underlines the need of additional developments before
the RQRPA could be adopted as a reliable tool to compute $\beta \beta$
processes.


title: The Breathing Modes of the $B=2$ Skyrmion and the Spin-Orbit Interaction

abstract:
  The coupling of the breathing and rotational modes of the skyrmion-skyrmion
system leads to a nucleon-nucleon spin-orbit interaction of short range, as
well as to spin-orbit potentials for the transitions $NN \to N(1440)N$, $NN \to
NN(1440)$ and $NN \to N(1440)N(1440)$. The longest range behaviour of these
spin-orbit potentials is calculated in closed form.


title:
Detection of Atmospheric Neutrinos and Relativistic Nuclear Structure
  Effects

abstract:
  Neutrino-nucleus cross sections for the detection of atmospheric neutrinos
are calculated in relativistic impulse and random phase approximations. Pion
production is estimated via inclusive Delta-hole nuclear excitations. The
number of pion events can confuse the identification of the neutrino flavor. As
a further source of pions we calculate coherent pion production (where the
nucleus remains in the ground state). We examine how these nuclear structure
effects influence atmospheric neutrino experiments and study possible
improvements in the present detector simulations.


title: The Okamoto-Nolen-Schiffer anomaly without rho-omega mixing

abstract:
  We examine the effect of isospin-violating meson-nucleon coupling constants
and of $\pi$-$\eta$ mixing on the binding-energy differences of mirror nuclei
in a model that possesses no contribution from $\rho$-$\omega$ mixing. The
${}^{3}$He-${}^{3}$H binding-energy difference is computed in a nonrelativistic
approach using a realistic wave function. We find the ${}^{3}$He-${}^{3}$H
binding-energy difference very sensitive to the short-distance behavior of the
nucleon-nucleon potential. We conclude that for the typically hard Bonn form
factors such models can not account for the observed binding-energy difference
in the three-nucleon system. For the medium-mass region (A=15--41) the
binding-energy differences of mirror nuclei are computed using a relativistic
mean-field approximation to the Walecka model. We obtain large binding-energy
differences---of the order of several hundred keV---arising from the
pseudoscalar sector. Two effects are primarily responsible for this new
finding: a) the inclusion of isospin breaking in the pion-nucleon coupling
constant, and b) the in-medium enhancement of the small components of the
bound-state wave functions. We look for off-shell ambiguities in these results
and find them to be large.


title:
Relativistic Hydrodynamics for Heavy--Ion Collisions: Freeze--Out and
  Particle Spectra

abstract:
  We investigate freeze--out in hydrodynamic models for relativistic heavy--ion
collisions. In particular, instantaneous freeze--out across a hypersurface of
constant temperature (``isothermal'' freeze--out) is compared with that across
a hypersurface at constant time in the center-of-momentum frame
(``isochronous'' freeze--out). For one--dimensional (longitudinal) expansion
the rapidity distributions are shown to differ significantly in the two
scenarios, while the transverse momentum spectra are remarkably similar. We
also investigate the rapidity distribution in greater detail and show that the
Gaussian-like shape of this distribution commonly associated with the Landau
expansion model in general emerges only if one neglects contributions from
time-like parts of the isothermal freeze--out hypersurface.


title:
Goldstone Theorem and Diquark Confinement Beyond Rainbow-Ladder
  Approximation

abstract:
  The quark Dyson-Schwinger equation and meson Bethe-Salpeter equation are
studied in a truncation scheme that extends the rainbow-ladder approximation
such that, in the chiral limit, the isovector, pseudoscalar meson remains
massless. Quark-quark (diquark) correlations, which are bound in rainbow-ladder
approximation, are destabilised by repulsive contributions that only appear at
higher order in the Bethe-Salpeter kernel. The net effect of higher order terms
on the meson bound-state masses is small.


title: Chiral symmetry in nuclei

abstract:
  The role of the quark condensate in low-energy QCD and its behaviour in
nuclear matter are discussed. Partial restoration of chiral symmetry, as
indicated by a reduction of the quark condensate in matter, could significantly
alter the properties of nucleons and mesons. Various signals of these effects
are discussed: enhancement of the axial charge of a nucleon, lepton pair
production and $\overline K$-nucleus attraction. (Talk presented at the Nuclear
Physics Study Weekend on Extreme States of Nuclei, Abingdon, October 1995)


title:
Collective Coordinates and the Absence of Yukawa Coupling in the
  Classical Skyrme Model

abstract:
  In systems with constraints, physical states must be annihilated by the
constraints. We make use of this rule to construct physical asymptotic states
in the Skyrme model. The standard derivation of the Born terms with asymptotic
physical states shows that there is no Yukawa coupling for the Skyrmion. We
propose a remedy tested in other solitonic models: A Wilsonian action obtained
after integrating the energetic mesons and where the Skyrmion is a quantum
state should have a Yukawa coupling.


title:
Application of a Two-Parameter Quantum Algebra to Rotational
  Spectroscopy of Nuclei

abstract:
  A two-parameter quantum algebra $U_{qp}({\rm u}_2)$ is briefly investigated
in this paper. The basic ingredients of a model based on the $U_{qp}({\rm
u}_2)$ symmetry, the $qp$-rotator model, are presented in detail. Some general
tendencies arising from the application of this model to the description of
rotational bands of various atomic nuclei are summarized.

categories: nucl-th math-ph math.MP math.QA q-alg quant-ph


title: Realistic Interactions and Dilepton production off pp-collisions

abstract:
  We present a model for dilepton production of proton-proton collisions using
a realist T-matrix that by incorporating Delta-isobar degrees of freedom fits
the NN-scattering data up to 2 GeV. The results we find differ in details from
earlier work that use less sophisticated interactions but the overall agreement
with these calculations is good.


abstract:
  Non-equilibrium modifications of the nuclear equation of state are assessed
in the framework of Extended Irreversible Thermodynamics. The expected size of
the non-equilibrium corrections to quantities like the nuclear-matter
incompressibility $K$ and the liquid-vapor critical temperature $T_c$ are
compared to the uncertainties associated at present with the usual equilibrium
values. The quantitative estimates are obtained in situations characterized by
a stationary planar shear flow of realistic magnitude, or by a stationary
temperature gradient.


title: Quark-hadron phase transition with surface fluctuation

abstract:
  The effect of surface fluctuation on the observables of quark-hadron phase
transition is studied. The Ginzburg-Landau formalism is extended by the
inclusion of an extra term in the free energy that depends on the vertical
displacements from a flat surface. The probability that a bin has a particular
net displacement is determined by lattice simulation, where the physics input
is color confinement. The surface fluctuation from bin to bin is related to
multiplicity fluctuation, which in turn is measured by the factorial moments.
It is found that both the F-scaling behavior and the scaling exponent are
essentially unaffected by the inclusion of surface fluctuation.


title:
Analysis of proton-induced fragment production cross sections by the
  Quantum Molecular Dynamics plus Statistical Decay Model

abstract:
  The production cross sections of various fragments from proton-induced
reactions on $^{56}$Fe and $^{27}$Al have been analyzed by the Quantum
Molecular Dynamics (QMD) plus Statistical Decay Model (SDM). It was found that
the mass and charge distributions calculated with and without the statistical
decay have very different shapes. These results also depend strongly on the
impact parameter, showing an importance of the dynamical treatment as realized
by the QMD approach. The calculated results were compared with experimental
data in the energy region from 50 MeV to 5 GeV. The QMD+SDM calculation could
reproduce the production cross sections of the light clusters and
intermediate-mass to heavy fragments in a good accuracy. The production cross
section of $^{7}$Be was, however, underpredicted by approximately 2 orders of
magnitude, showing the necessity of another reaction mechanism not taken into
account in the present model.


title:
Model--space approach to $^{1}S_{0}$ neutron and proton pairing with the
  Bonn meson--exchange potentials

abstract:
  In this work we calculate neutron and proton energy gaps in neutron star
matter, using the Bonn meson--exchange interactions and a model--space approach
to the gap equation. This approach allows a consistent calculation of energy
gaps and single particle energies with the model--space
Brueckner--Hartree--Fock (MBHF) method, without double counting of
two--particle correlations. Neutron energy gaps are calculated at zero and
finite temperature. Proton energy gaps are calculated at beta equilibrium, and
it is shown that the inclusion of muons has a significant effect. The results
are compared with those of other works, and the implications for neutron star
physics are briefly discussed.


title: Medium Effects on Binary Collisions with the Delta Resonance

abstract:
  To facilitate the relativistic heavy-ion calculations based on transport
equations, the binary collisions involving a $\Delta$ resonance in either the
entrance channel or the exit channel are investigated within a Hamiltonian
formulation of $\pi NN$ interactions. An averaging procedure is developed to
define a quasi-particle $\Delta^*$ and to express the experimentally measured
$NN\rightarrow \pi NN$ cross section in terms of an effective $NN\rightarrow
N\Delta^\ast$ cross section. In contrast to previous works, the main feature of
the present approach is that the mass and the momentum of the produced
$\Delta^*$'s are calculated dynamically from the bare $\Delta \leftrightarrow
\pi N$ vertex interaction of the model Hamiltonian and are constrained by the
unitarity condition. The procedure is then extended to define the effective
cross sections for the experimentally inaccessible $N\Delta^\ast \rightarrow
NN$ and $N\Delta^\ast \rightarrow N\Delta^\ast$ reactions. The predicted cross
sections are significantly different from what are commonly assumed in
relativistic heavy-ion calculations. The $\Delta$ potential in nuclear matter
has been calculated by using a Bruckner-Hartree-Fock approximation. By
including the mean-field effects on the $\Delta$ propagation, the effective
cross sections of the $NN\rightarrow N\Delta^\ast$, $N\Delta^\ast \rightarrow
NN$ and $N\Delta^\ast \rightarrow N\Delta^\ast$ reactions in nuclear matter are
predicted. It is demonstrated that the density dependence is most dramatic in
the energy region close to the pion production threshold.


title: Quarks in Finite Nuclei

abstract:
  We describe the development of a theoretical description of the structure of
finite nuclei based on a relativistic quark model of the structure of the bound
nucleons which interact through the (self-consistent) exchange of scalar and
vector mesons.


title: Coherent $\pi^0$ and $\eta$ Photoproduction on the Deuteron

abstract:
  Coherent pion photoproduction, $d(\gamma,\pi^0)d$, is calculated in a coupled
channels approach in momentum space using an elementary production operator
that includes Born terms, vector meson exchange and $M1/E2$ $\Delta$-resonance
excitation. The final state interaction is treated in the KMT multiple
scattering approach that describes $\pi d$ elastic scattering well.
Differential cross sections are found to agree well with existing ($\gamma,
\pi^0$) data. The polarization observables $\Sigma , iT_{11}$ and the tensor
analyzing powers are predicted for forthcoming experiments. A number of
transparent relationships between polarization observables and the elementary
production operator is derived. Finally, calculations are performed for
coherent eta photoproduction, $d (\gamma, \eta)d$, in the threshold region
which agree well with a very recent Mainz experiment.


title: Elastic Pion Scattering on the Deuteron in a Multiple Scattering Model

abstract:
  Pion elastic scattering on deuterium is studied in the KMT multiple
scattering approach developed in momentum space. Using a Paris wave function
and the same methods and approximations as commonly used in pion scattering on
heavier nuclei excellent agreement with differential cross section data is
obtained for a wide range of pion energies. Only for $T_{\pi}>250$ MeV and very
backward angles, discrepancies appear that are reminiscent of disagreements in
pion scattering on $^3$He, $^3$H, and $^4$He. At low energies the second order
corrections have been included. Polarization observables are studied in detail.
While tensor analyzing powers are well reproduced, vector analyzing powers
exhibit dramatic discrepancies.


title: From Chiral Lagrangians to Landau Fermi Liquid Theory of Nuclear Matter

abstract:
  A simple relation between the effective parameters of chiral Lagrangians in
medium as predicted by BR scaling and Landau Fermi liquid parameters is
derived. This provides a link between an effective theory of QCD at mean-field
level and many-body theory of nuclear matter. It connects in particular the
scaling vector-meson mass probed by dileptons produced in heavy-ion collisions
(e.g., CERES of CERN-SPS) to the scaling nucleon-mass relevant for low-energy
spectroscopic properties, e.g., the nuclear gyromagnetic ratios $\delta g_l$
and the effective axial-vector constant $g_A^\star$.


title:
Spin Structure Function of the Deuteron in the Resonance Region and the
  GDH Sum Rule for the Neutron

abstract:
  The nuclear effects in the spin-dependent structure function $g_1$ of the
deuteron are studied in the kinematics of future experiments at CEBAF, ($\nu
\leq 3~GeV, ~Q^2 \leq 2~GeV^2$). The magnitude of the nuclear effects is found
to be significantly larger than the one occurring in deep inelastic scattering
($\nu\to \infty, ~Q^2\to \infty$). We discuss the mechanism leading to large
effects in the region of the nucleon resonances. A possibility to measure the
neutron structure functions in the CEBAF experiments with deuterium is
analysed, and conclusions about the experimental study of the $Q^2$ dependence
of the Gerasimov-Drell-Hearn Sum Rule for the neutron are drawn.


title: Can Gluons Trace Baryon Number?

abstract:
  QCD as a gauge non-Abelian theory imposes severe constraints on the structure
of the baryon wave function. We point out that, contrary to a widely accepted
belief, the traces of baryon number in a high-energy process can reside in a
non-perturbative configuration of gluon fields, rather than in the valence
quarks. We argue that this conjecture can be tested experimentally, since it
can lead to substantial baryon asymmetry in the central rapidity region of
ultra-relativistic nucleus-nucleus collisions.


title: Delta production in $\bar{p}$d-annihilation at rest

abstract:
  We study the $\Delta$-excitation in $\overline{p}d$ annihilation at rest. The
invariant spectra of the $\pi^+p$ and $\pi^-p$ systems selecting the protons
with momenta above 400 MeV/c are analyzed. The calculations reproduces
reasonably the experimental data.


title:
Astrophysical Reaction Rates for $^{10}$B(p,$\alpha$)$^{7}$Be and
  $^{11}$B(p,$\alpha$)$^{8}$Be From a Direct Model

abstract:
  The reactions $^{10}$B(p,$\alpha$)$^{7}$Be and $^{11}$B(p,$\alpha$)$^{8}$Be
are studied at thermonuclear energies using DWBA calculations. For both
reactions, transitions to the ground states and first excited states are
investigated. In the case of $^{10}$B(p,$\alpha$)$^{7}$Be, a resonance at
$E_{Res}=10$ keV can be consistently described in the potential model, thereby
allowing the extension of the astrophysical $S$-factor data to very low
energies. Strong interference with a resonance at about $E_{Res}=550$ keV
require a Breit-Wigner description of that resonance and the introduction of an
interference term for the reaction $^{10}$B(p,$\alpha_1$)$^{7}$Be$^*$. Two
isospin $T=1$ resonances (at $E_{Res1}=149$ keV and $E_{Res2}=619$ keV)
observed in the $^{11}$B+p reactions necessitate Breit-Wigner resonance and
interference terms to fit the data of the $^{11}$B(p,$\alpha$)$^{8}$Be
reaction. $S$-factors and thermonuclear reaction rates are given for each
reaction. The present calculation is the first consistent parametrization for
the transition to the ground states and first excited states at low energies.


title:
Chaoticity and Dissipation of Nuclear Collective Motion in a Classical
  Model

abstract:
  We analyze the behavior of a gas of classical particles moving in a
two-dimensional "nuclear" billiard whose multipole-deformed walls undergo
periodic shape oscillations. We demonstrate that a single particle Hamiltonian
containing coupling terms between the particles' motion and the collective
coordinate induces a chaotic dynamics for any multipolarity, independently on
the geometry of the billiard. The absence of coupling terms allows us to
recover qualitatively the "wall formula" predictions. We also discuss the
dissipative behavior of the wall motion and its relation with the
order-to-chaos transition in the dynamics of the microscopic degrees of
freedom.


title: Quark-meson coupling model for finite nuclei

abstract:
  A Quark-Meson Coupling (QMC) model is extended to finite nuclei in the
relativistic mean-field or Hartree approximation. The ultra-relativistic quarks
are assumed to be bound in non-overlapping nucleon bags, and the interaction
between nucleons arises from a coupling of vector and scalar meson fields to
the quarks. We develop a perturbative scheme for treating the spatial
nonuniformity of the meson fields over the volume of the nucleon as well as the
nucleus. Results of calculations for spherical nuclei are given, based on a fit
to the equilibrium properties of nuclear matter. Several possible extensions of
the model are also considered.


title: The Pauli principle, QRPA and the two-neutrino double beta decay

abstract:
  We examine the violation of the Pauli exclusion principle in the
Quasiparticle Random Phase Approximation (QRPA) calculation of the two-neutrino
double beta decay matrix elements, which has its origin in the quasi-boson
approximation. For that purpose we propose a new renormalized QRPA with
proton-neutron pairing method (full-RQRPA) for nuclear structure studies, which
includes ground state correlation beyond the QRPA. This is achieved by using of
renormalized quasi-boson approximation, in which the Pauli exclusion principle
is taken into account more carefully. The full-RQRPA has been applied to
two-neutrino double beta decay of $^{76}Ge$, $^{82}Se$, $^{128}Te$ and
$^{130}Te$. The nuclear matrix elements have been found significantly less
sensitive to the increasing strength of particle-particle interaction in the
physically interesting region in comparison with QRPA results. The strong
differences between the results of both methods indicate that the Pauli
exclusion principle plays an important role in the evaluation of the double
beta decay. The inclusion of the Pauli principle removes the difficulties with
the strong dependence on the particle-particle strength $g_{pp}$ in the QRPA on
the two-neutrino double beta decay.


title: Reaction rate for two--neutron capture by $^4$He

abstract:
  Recent investigations suggest that the neutrino--heated hot bubble between
the nascent neutron star and the overlying stellar mantle of a type--II
supernova may be the site of the r--process. In the preceding $\alpha$--process
building up the elements to $A \approx 100$, the $^4$He(2n,$\gamma$)$^6$He--
and $^6$He($\alpha$,n)$^9$Be--reactions bridging the instability gap at $A=5$
and $A=8$ could be of relevance. We suggest a mechanism for
$^4$He(2n,$\gamma$)$^6$He and calculate the reaction rate within the
$\alpha$+n+n approach. The value obtained is about a factor 1.6 smaller than
the one obtained recently in the simpler direct--capture model, but is at least
three order of magnitude enhanced compared to the previously adopted value. Our
calculation confirms the result of the direct--capture calculation that under
representative conditions in the $\alpha$--process the reaction path proceeding
through $^6$He is negligible compared to $^4$He($\alpha$n,$\gamma$)$^9$Be.


title: Description of deformed nuclei in the sdg boson model

abstract:
  We present a study of deformed nuclei in the framework of the sdg interacting
boson model utilizing both numerical diagonalization and analytical $1/N$
expansion techniques. The focus is on description of high-spin states which
have recently become computationally accessible through the use of computer
algebra in the $1/N$ expansion formalism. A systematic study is made of
high-spin states in rare-earth and actinide nuclei.


title: The influence of negative-energy states on proton-proton bremsstrahlung

abstract:
  We investigate the effect of negative-energy states on proton-proton
bremsstrahlung using a manifestly covariant amplitude based on a T-matrix
constructed in a spectator model. We show that there is a large cancellation
among the zeroth-order, single- and double-scattering diagrams involving
negative-energy nucleonic currents. We thus conclude that it is essential to
include all these diagrams when studying effects of negative-energy states.


title:
How reliable is the mean-field Nuclear Matter description for supporting
  Chiral Effective Lagrangians?

abstract:
  The link between non-linear chiral effective Lagrangians and the Walecka
model description of bulk nuclear matter [1] is questioned. This fact is by
itself due to the Mean Field Approximation (MFA) which in nuclear mater makes
the picture of a nucleon-nucleon interaction based on scalar(vector) meson
exchange, equivalent to the description of a nuclear matter based on attractive
and repulsive contact interactions. We present a linear chiral model where this
link between the Walecka model and an underlying to chiral symmetry realization
still holds, due to MFA.


title: Many Body Corrections to Nuclear Anapole Moment

abstract:
  The many body contributions to the nuclear anapole moment of $^{133}$Cs,
$^{205}$Tl, $^{207,209}$PB, and $^{209}$Bi from the core polarization are
calculated in the random-phase approximation with the effective residual
interaction. Strong reduction of a valence nucleon contribution was found
provided by the core polarization effects. The contribution of the core
particles to the anapole moment compensates this reduction to large extent
keeping the magnitude of nuclear anapole moment close to its initial single
particle value.


title: Neutron/Proton Structure Function Ratio at Large x

abstract:
  We re-examine the large-x neutron/proton structure function ratio extracted
from the latest deuteron data, taking into account the most recent developments
in the treatment of Fermi motion, binding and nucleon off-shell effects in the
deuteron. Our findings suggest that as x->1 the ratio of the neutron to proton
structure functions (F_2^n/F_2^p) is consistent with the perturbative QCD
expectation of 3/7, but larger than the value of 1/4 obtained in earlier
analyses.


title:
Dynamical chaos and critical behavior in Vlasov simulations of nuclear
  multifragmentation

abstract:
  We discuss the presence of both dynamical chaos and signals of a
second--order phase transition in numerical Vlasov simulations of nuclear
multifragmentation. We find that chaoticity and criticality are strongly
related and play a crucial role in the process of fragments formation. This
connection is not limited to our model and seems a rather general feature.


title: Evaporation of light particles from a hot, deformed and rotating nucleus

abstract:
  The dependence of the transmission coefficient on the deformation, the
collective rotation and excitation energy of the compound nucleus emitting
light particles is introduced in the framework of Wei{\ss}kopf's evaporation
theory. The competition between fission and particle evaporation is treated by
a~Langevin equation for the fission variable coupled to the emission process.
Detailed calculations are presented on the decay of different Gd and Yb
isotopes at an excitation energy of about 250~MeV. These calculations
demonstrate the importance of the effects of nuclear deformation and of the
initial spin distribution on the evaporation.


title: Relativistic analysis of the 208Pb(e,e'p)207Tl reaction at high momentum

abstract:
  The recent 208Pb(e,e'p)207Tl data from NIKHEF-K at high missing momentum
(p_m>300 MeV/c) are compared to theoretical results obtained with a fully
relativistic formalism previously applied to analyze data on the low missing
momentum (p_m < 300 MeV/c) region. The same relativistic optical potential and
mean field wave functions are used in the two p_m-regions. The spectroscopic
factors of the various shells are extracted from the analysis of the low-p_m
data and then used in the high-p_m region. In contrast to previous analyses
using a nonrelativistic mean field formalism, we do not find a substantial
deviation from the mean field predictions other than that of the spectroscopic
factors, which appear to be consistent with both low- and high-p_m data. We
find that the difference between results of relativistic and nonrelativistic
formalisms is enhanced in the p_m<0 region that will be interesting to explore
experimentally.


title: In medium effects on the $\phi$ meson

abstract:
  The temperature dependence of the $\phi$ meson mass and its decay width
($\phi \rightarrow K \bar{K}$)have been studied from an effective non-linear
chiral Lagrangian in $SU(3)$. Effective mass has been obtained from the pole
position of the full propagator. The width has also been calculated. It has
been found that the mass decreases with temperature very slowly whereas the
decay width increases quite sharply. Possible consequence on the QGP signals is
discussed.


title: Neutron halos in heavy nuclei -- relativistic mean field approach

abstract:
  Assuming a~simple spherical relativistic mean field model of the nucleus, we
estimate the width of the antiproton--neutron annihilation ($\Gamma_n$) and the
width of antiproton--proton ($\Gamma_p$) annihilation, in an antiprotonic atom
system. This allows us to determine the halo factor $f$, which is then
discussed in the context of experimental data obtained in measurements recently
done on LEAR utility at CERN. Another quantity which characterizes the
deviation of the average nuclear densities ratio from the corresponding ratio
of the homogeneous densities is introduced too. It was shown that it is also a
good indicator of the neutron halo. The results are compared to experimental
data as well as to the data of the simple liquid droplet model of the nuclear
densities. The single particle structure of the nuclear density tail is
discusssed also.


title: Theoretical Predictions for Pionium Searches

abstract:
  Characteristic properties of pionium $A_{2\pi}$ and associated low energy
s--wave cross sections $\sigma(\pi^0\pi^0\to \pi^0\pi^0)$,
$\sigma(\pi^+\pi^-\to\pi^0\pi^0)$ and $\sigma(\pi^0\pi^0\to \pi^+\pi^-)$ are
investigated with a coupled channels potential model. Some experimental results
and conclusions are to be reconsidered.


title:
Quasi-elastic and inelastic inclusive electron scattering from an oxygen
  jet target

abstract:
  The results of an experiment on inclusive electron scattering from an oxygen
jet target, performed in a wide range of energy and momentum transfer covering
both quasi-elastic and $\Delta$(1232) resonance regions, are reported. In the
former region the theoretical predictions, obtained including effects of
nucleon-nucleon correlations in both initial and final states, give a good
description of the experimental data. In the inelastic region a broadening as
well as a damping of the resonant part of the cross section with respect to the
free nucleon case is observed. The need of more detailed calculations including
nuclear structure effects on the electroproduction cross section of nucleon
resonances is highlighted.


title:
Average over energy effect of parity nonconservation in neutron
  scattering on heavy nuclei

abstract:
  Using semiclassical approximation we consider parity nonconservation (PNC)
averaged over compound resonances. We demonstrate that the result of the
averaging crucially depends on the properties of residual strong
nucleon-nucleon interaction. Natural way to elucidate this problem is to
investigate experimentally PNC spin rotation with nonmonachromatic neutron
beam: $E \sim \Delta E \sim 1MeV$. Value of the effect can reach $\psi \sim
10^{-5}-10^{-4}$ per mean free path.


title: The role of the $S_{31}$ $\pi N$ partial wave in the three-nucleon force

abstract:
  We re-examine the contribution of the $\pi N$ $S_{31}$ channel to the
three-nucleon force for an energy dependent separable potential. Despite the
lack of cancellation between the $S_{31}$ and the $P_{11}$ and $P_{33}$
channels, the total contribution of the three-nucleon force to the triton
binding is still small.


title: Thermal hadron production in Si-Au collisions

abstract:
  The most abundantly produced hadron species in $Si\!-\!Au$ collisions at the
BNL-AGS (nucleons, pions, kaons, antikaons and hyperons) are shown to be in
accord with emission from a thermal resonance gas source of temperature
$T\simeq 110$ MeV and baryochemical potential $\mu_B \simeq 540$ MeV,
corresponding to about 1/3 standard nuclear density. Our analysis takes the
isopin asymmetry of the initial state fully into account.


title: Chiral Lagrangians and Quark Condensate in Nuclei

abstract:
  We study the evolution with density of the quark condensate in the nuclear
medium with interacting nucleons and including the short range correlations. We
work with two chiral models, the linear sigma model and the non-linear one. For
the last one we use two versions, one which does not satisfy PCAC, and another
one which does. We show that the quark condensate, as other observables, is
independent on the variant selected. The application to physical pions excludes
the linear sigma model as a credible one. In the non-linear models our
conclusions are: first there is no systematic reaction imposed by chiral
symmetry against symmetry restoration, second, if one keeps only the s-wave
pion-nucleon interaction, the quark condensate evolves essentially linearly
with density, as if the nucleons were non interacting. The main correction
arises from the p-wave pion-nucleon interaction. Last, in the s-wave optical
potential, chiral symmetry tolerates but does not impose two body terms. On the
other hand the effect of correlations linked to the isospin symmetric amplitude
is negligible.


title:
Comment on ``Strangeness enhancement in $p+A$ and S$+A$ interactions at
  energies near 200 $A$ GeV"

abstract:
  We argue that the recent analysis of strangeness production in nuclear
collisions at 200 $A$ GeV/$c$ performed by Topor Pop {\it et al.} \cite{To:95}
is flawed. The conclusions are based on an erroneous interpretation of the data
and the numerical model results. The term ``strangeness enhancement" is used in
a misleading way.


title:
Realistic Expanding Source Model for Invariant One-Particle Multiplicity
  Distributions and Two-Particle Correlations in Relativistic Heavy-Ion
  Collisions

abstract:
  We present a realistic expanding source model with nine parameters that are
necessary and sufficient to describe the main physics occuring during
hydrodynamical freezeout of the excited hadronic matter produced in
relativistic heavy-ion collisions. As a first test of the model, we compare it
to data from central Si + Au collisions at p_lab/A = 14.6 GeV/c measured in
experiment E-802 at the AGS. An overall chi-square per degree of freedom of
1.055 is achieved for a fit to 1416 data points involving invariant pi^+, pi^-,
K^+, and K^- one-particle multiplicity distributions and pi^+ and K^+
two-particle correlations. The 99-percent-confidence region of parameter space
is identified, leading to one-dimensional error estimates on the nine fitted
parameters and other calculated physical quantities. Three of the most
important results are the freezeout temperature, longitudinal proper time, and
baryon density along the symmetry axis. For these we find values of 92.9 +/-
4.4 MeV, 8.2 +/- 2.2 fm/c, and 0.0222 + 0.0096 / - 0.0069 fm^-3, respectively.


title: Relativistic bound-state equations in three dimensions

abstract:
  Firstly, a systematic procedure is derived for obtaining three-dimensional
bound-state equations from four-dimensional ones. Unlike ``quasi-potential
approaches'' this procedure does not involve the use of delta-function
constraints on the relative four-momentum. In the absence of negative-energy
states, the kernels of the three-dimensional equations derived by this
technique may be represented as sums of time-ordered perturbation theory
diagrams. Consequently, such equations have two major advantages over
quasi-potential equations: they may easily be written down in any Lorentz
frame, and they include the meson-retardation effects present in the original
four-dimensional equation. Secondly, a simple four-dimensional equation with
the correct one-body limit is obtained by a reorganization of the generalized
ladder Bethe-Salpeter kernel. Thirdly, our approach to deriving
three-dimensional equations is applied to this four-dimensional equation, thus
yielding a retarded interaction for use in the three-dimensional bound-state
equation of Wallace and Mandelzweig. The resulting three-dimensional equation
has the correct one-body limit and may be systematically improved upon. The
quality of the three-dimensional equation, and our general technique for
deriving such equations, is then tested by calculating bound-state properties
in a scalar field theory using six different bound-state equations. It is found
that equations obtained using the method espoused here approximate the wave
functions obtained from their parent four-dimensional equations significantly
better than the corresponding quasi-potential equations do.


title: Realistic Expanding Source Model for Relativistic Heavy-Ion Collisions

abstract:
  We introduce a new realistic expanding source model for invariant
one-particle multiplicity distributions and two-particle correlations in nearly
central relativistic heavy-ion collisions that contains nine adjustable
parameters, which are necessary and sufficient to properly characterize the
gross properties of the source during its freezeout from a hydrodynamical fluid
into a collection of noninteracting, free-streaming hadrons. These nine
physically relevant parameters fall into three categories of three parameters
each, with the first category corresponding to the source's longitudinal
motion, the second category corresponding to its transverse motion, and the
third category corresponding to its intrinsic properties. As an initial
application, we apply our model to the analysis of invariant pi^+, pi^-, K^+,
and K^- one-particle multiplicity distributions and pi^+ and K^+ two-particle
correlations for nearly central Si + Au collisions at p_lab/A = 14.6 GeV/c. In
a minimization with 1416 data points, the resulting chi-square is 1484.6, which
corresponds to an acceptable chi-square per degree of freedom of 1.055. We list
the values of the nine parameters determined this way plus several additional
calculated freezeout quantities of physical interest, along with their
uncertainties at 99% confidence limits.


title:
The production of residual nuclei in peripheral high energy
  nucleus-nucleus interactions

abstract:
  A formation zone intranuclear cascade model is applied to peripheral
nucleus-nucleus collisions. We calculate the excitation energies of
prefragments, treat their further nuclear disintegration and introduce a model
for nuclear deexcitation by photon emission. Results are compared to data on
target associated particle production in nucleus-nucleus collisions. We discuss
implications of these models to the description of particle production in the
fragmentation regions. Special emphasis is put on applications for air showers
induced by cosmic ray nuclei and for residual nucleus production at heavy ion
colliders.


title: Lifetimes and Sizes from Two-Particle Correlation Functions

abstract:
  We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the
two-particle correlation function for azimuthally symmetric expanding sources.
We derive model-independent expressions for the YKP fit parameters and discuss
their physical interpretation. We use them to evaluate the YKP fit parameters
and their momentum dependence for a simple model for the emission function and
propose new strategies for extracting the source lifetime. Longitudinal
expansion of the source can be seen directly in the rapidity dependence of the
Yano-Koonin velocity.


title: Non-trivial aspects of the onset of nuclear collectivity: Static moments

abstract:
  We consider several topics concerning static magnetic dipole and electric
quadrupole moments ($\mu$ and $Q$) as signatures of the onset of nuclear
collectivity. Having previously noted that in $^{50}\mbox{Cr}$ there is an
abrupt change of sign in $Q$ of yrast states with $J^{\pi}=10^+, 12^+$, and
$14^+$ relative to lower $J$ states, we discuss whether these states are oblate
or prolate. We next show that configuration mixing leads to much larger changes
in $Q$ than in $\mu$. We then look for other bands of interest in
$^{50}\mbox{Cr}$. Finally we discuss the Jolos-von Brentano relationship which
relates $Q$ of $2^+_1$ states to $B({\rm E2})$'s for transitions from and to
the $2^+_1$ states.


title:
Application of a semi-microscopic core-particle coupling method to the
  backbending in odd deformed nuclei

abstract:
  In two previous papers, the Kerman-Klein-Donau-Frauendorf (KKDF) model was
used to study rotational bands of odd deformed nuclei. Here we describe
backbending for odd nuclei using the same model. The backbending in the
neighboring even nuclei is described by a phenomenological two band model, and
this core is then coupled to a large single-particle space, as in our previous
work. The results obtained for energies and M1 transition rates are compared
with experimental data for 165Lu and for energies alone to the experimental
data for 179W. For the case of 165Lu comparison is also made with previous
theoretical work.


title: Low-energy M1 strength in the Li-7(p,gamma_0)Be-8 reaction

abstract:
  The Li-7(p,gamma_0)Be-8 reaction is studied in a microscopic cluster model.
All relevant subsystem properties are well reproduced. The calculated
astrophysical S factor is in good agreement with the experimental data,
although some M1 strength is missing in the 1+;1 resonance region. There is no
contribution from the 1+;0 state. We estimate an M1 strength of 3.5% at 80 keV.
By assuming the experimental resonance parameters and channel spin ratio for
the first 1+ state that M1 strength is 6.3%, in good agreement with an R matrix
analysis. The large (20%) M1 strength determined from a transition matrix
element analysis may be caused by assuming a vanishing 0p3/2 spectroscopic
factor, which is not supported by shell model calculations.


title: Strong decays of nucleon and delta resonances

abstract:
  We study the strong couplings of the nucleon and delta resonances in a
collective model. In the ensuing algebraic treatment we derive closed
expressions for decay widths which are used to analyze the experimental data
for strong decays into the pion and eta channels.


title: A Mean Field Theory of the Chiral Phase Transition

abstract:
  The recent discussions by Koci\'c and Kogut on the nature of the chiral phase
transition are reviewed. The mean-field nature of the transition suggested by
these authors is supported in random matrix theory by Verbaarschot and Jackson
which reproduces many aspects of QCD lattice simulations. In this paper, we
point out physical arguments that favor a mean-field transition, not only for
zero density and high temperature, but also for finite density. We show, using
the Gross-Neveu model in 3 spatial dimensions in mean-field approximation, how
the phase transition is constructed. In order to reproduce the lowering of the
$\rho=0$, $T=0$ vacuum evaluated in lattice calculations, we introduce
{nucleons} rather than constituent quarks in negative energy states, down to a
momentum cut-off of $\Lambda$. We also discuss Brown-Rho scaling of the hadron
masses in relation to the QCD phase transition, and how this scaling affects
the CERES and HELIOS-3 dilepton experiments.


title:
Deriving the quark condensate within a finite Fermi system from the
  generating functional of chiral perturbation theory

abstract:
  The generating functional of heavy baryon chiral perturbation theory at order
O(Q^2) in the mean field approximation (with a pseudoscalar source coupling
which is consistent with the PCAC-Ward identities on the current quark level)
has been exploited to derive Migdal's in--medium pion propagator. It is shown
that the prediction for the density dependence of the quark condensate obtained
on the composite hadron level by embedding PCAC within the framework of
Migdal's approach to finite Fermi systems is identical to that resulting from
QCD.


title:
Feynman Graphs and Generalized Eikonal Approach to High Energy Knock-Out
  Processes

abstract:
  The cross section of hard semi-exclusive $A(e,e'N)(A-1)$ reactions for fixed
missing energy and momentum is calculated within the eikonal approximation.
Relativistic dynamics and kinematics of high energy processes are unambiguously
accounted for by using the analysis of appropriate Feynman diagrams. A
significant dependence of the final state interactions on the missing energy is
found, which is important for interpretation of forthcoming color transparency
experiments. A new, more stringent kinematic restriction on the region where
the contribution of short-range nucleon correlations is enhanced in
semi-exclusive knock-out processes is derived. It is also demonstrated that the
use of light-cone variables leads to a considerable simplification of the
description of high-energy knock-out reactions.


title:
Front Form Spinors in Weinberg-Soper Formalism and Melosh
  Transformations for any Spin

abstract:
  Using the Weinberg-Soper formalism we construct the front form
$(j,0)\oplus(0,j)$ spinors. Explicit expressions for the generalised Melosh
transformations up to spin two are obtained. The formalism, without explicitly
invoking any wave equations, reproduces spin one half front-form results of
Melosh, Lepage and Brodsky, and Dziembowski.


title:
Temperature Dependence of Hadron Masses from the Zimanyi-Moszkowski
  Model

abstract:
  An extended version of the Zimanyi-Moskowski (ZM) model has been used to
calculate the temperature dependence of the hadronic masses. The calculation of
meson masses in the Random Phase Approximation (RPA) gives an increase in the
$\sigma$, $\omega$ and $\pi$ effective masses with temperature.


title: Neutron Structure Functions From Nuclear Data

abstract:
  The spin-averaged structure function of the neutron, F_2^n, is extracted from
recent deuteron data, taking into account the small but significant corrections
due to nuclear effects in the deuteron. At small x, the F_2D/F_2p ratio
measured by the New Muon and Fermilab E665 Collaborations is interpreted to
suggest a small amount of shadowing in deuterium, which acts to enhance F_2^n
for x < 0.1. A careful treatment of Fermi motion, binding and nucleon off-shell
effects in the deuteron also indicates that the neutron/proton structure
function ratio as x -> 1 is consistent with the perturbative QCD expectation of
3/7, but larger than the traditional value of 1/4.


title: Bethe-Salpeter Amplitudes and Static Properties of the Deuteron

abstract:
  Extended calculations of the deuteron's static properties, based on the
numerical solution of the Bethe-Salpeter equation, are presented. A formalism
is developed, which provides a comparative analysis of the covariant amplitudes
in various representations and nonrelativistic wave functions. The magnetic and
quadrupole moments of the deuteron are calculated in the Bethe-Salpeter
formalism and the role of relativistic corrections is discussed.


title: Foundations of the Constituent Quark Model

abstract:
  'Constituent quarks' means massive quarks, in contrast to the nearly massless
u,d,s quarks of the QCD lagrangian. The dynamical or constituent masses appear
owing to the spontaneous chiral symmetry breaking in QCD. A realistic mechanism
of the chiral symmetry breaking is provided by instantons. Therefore, I review
the present status of the QCD instanton vacuum, emphasizing the mechanism of
chiral symmetry breaking and of the generation of the constitutent quark mass.
I end up with the Nambu--Jona-Lasinio-type effective theory to which QCD is
reduced at low momenta.


title:
Connection between Effective Chiral Lagrangians and Landau-Migdal Fermi
  Liquid Theory of Nuclear Matter

abstract:
  I discuss in this lecture how to make a connection between effective chiral
Lagrangians -- low-energy effective theory of QCD -- and Landau Fermi liquid
theory extended by Migdal to nuclear matter. The practical purpose of such a
connection is to provide a link between certain observables in relativistic
heavy-ion processes and those in low-energy spectroscopy, giving a new insight
into how chiral dynamics manifests itself in nuclear systems.


title:
Nuclear Matter Properties in Derivative Coupling Models Beyond Mean -
  Field Approximation

abstract:
  The structure of infinite nuclear matter is studied with two of the Zimanyi -
Moszkowski (ZM) models in the framework of a relativistic approximation which
takes into account Hartree terms and beyond and is compared with the results
which come out of the relativistic Hartree - Fock approach in the linear
Walecka model. The simple treatment applied to these models can be used in
substitution to the more complicated Dirac - Brueckner - Hartree - Fock method
to perform future calculations in finite nuclei.


title:
Relativistic Calculations for Photonuclear Reactions (III): A Consistent
  Relativistic Analysis of the (e,e'p) and (gamma,p) Reactions

abstract:
  Relativistic calculations for the quasifree electron scattering process (e,
e'p) and the direct knockout contribution to (gamma, p) reactions are
presented. The spectroscopic factors determined from the former reaction are
used to fix the magnitude of the knockout contribution to the (gamma, p)
reaction at 60 MeV. The results obtained for several nuclei indicate that the
knockout contributions are much larger in magnitude and hence closer to the
data than predicted in an earlier comparison based on non-relativistic
calculations. We discuss the sensitivity of the results to the choice of
parameters for the binding and final state interactions. We find these
uncertainties to be more pronounced at the larger missing momenta explored by
the (gamma, p) reaction. The implications of the present results for the size
of contributions due to meson exchange currents are discussed.


title:
Photofission and Quasi-Deuteron-Nuclear State as Mixing of Bosons and
  Fermions

abstract:
  The empirical-phenomenological quasi-deuteron photofission description is
theoretically justified within the semiclassical, intermediate statistics
model. The transmutational fermion (nucleon) - boson (quasi-deuteron) potential
plays an essential role in the present context and is expressed in terms of
thermodynamical and of microscopical quantities, analogous to those commonly
used in the superfluid nuclear model.


title:
Momentum Distributions of Particles from Three--Body Halo Fragmentation:
  Final State Interactions

abstract:
  Momentum distributions of particles from nuclear break-up of fast three-body
halos are calculated consistently, and applied to $^{11}$Li. The same two-body
interactions between the three particles are used to calculate the ground state
structure and the final state of the reaction processes. We reproduce the
available momentum distributions from $^{11}$Li fragmentation, together with
the size and energy of $^{11}$Li, with a neutron-core relative state containing
a $p$-state admixture of 20\%-30\%. The available fragmentation data strongly
suggest an $s$-state in $^{10}$Li at about 50 keV, and indicate a $p$-state
around 500 keV.


title:
Time development of a density perturbation in the unstable nuclear
  matter

abstract:
  We present the solution of the time development of an unstable initial
density perturbation in the linearized Vlasov equation, completing the previous
analysis in the literature. The additional contributions found are usually
damped and can be neglected at large times in the unstable region. The work
clarifies also the problem of the normalization of the solution with respect to
the initial perturbation of the density.


title: Mean-field calculations of quasi-elastic responses in 4He

abstract:
  We present calculations of the quasi-elastic responses functions in 4He based
upon a mean-field model used to perform analogous calculations in heavier
nuclei. The meson exchange current contribution is small if compared with the
results of calculations where short-range correlations are explicitly
considered. It is argued that the presence of these correlations in the
description of the nuclear wave functions is crucial to make meson exchange
current effects appreciable.


title: Sidewise dispersion relations and the structure of the nucleon vertex

abstract:
  We revisit sidewise dispersion relations as a method to relate the nucleon
off-shell form factor to observable quantities, namely the meson-nucleon
scattering phase shifts. It is shown how for meson-nucleon scattering a
redefinition of the intermediate fields leaves the scattering amplitude
invariant, but changes the behavior of the off-shell form factor as expressed
through dispersion relations, thus showing representation dependence. We also
employ a coupled-channel unitary model to test the validity of approximations
concerning the influence of inelastic channels in the sidewise dispersion
relation method.


title:
Influence of Different Collective Coordinates on Spontaneous Fission
  Process in Fm Isotopes

abstract:
  We study the role of different collective degrees of freedom in spontaneous
fission process of even--even Fm isotopes. To find a proper collective space we
examine a reach collection of nuclear shape parameters $\{\beta_{\lambda}\}$,
with $\lambda$=2,3,4,5,6 and 8; as well as the paring degrees of freedom i.e.
proton $\Delta_{p}$ and neutron $\Delta_{n}$ pairing gaps. On the basis of the
multidimensional dynamic--programming method (MDPM) the optimal collective
space $\{\beta_{2}, \beta_{4}, \beta_{6}, \Delta_{p}, \Delta_{n}\}$ for Fm
isotopes was found.


title: Some New Aspects of Bimodal Fission in 258Fm Isotope

abstract:
  Using the multidimensional dynamic--programming method (MDPM) in the
four--dimensional deformation space $\{\beta_{\lambda}\}$ with $\lambda$=2, 4,
35 and 6 we were able to study evolution of the action integral for the
fissioning nucleus $^{258}$Fm. We found the second minimum on the
cross--section of the action integral for $\beta_2 \approx 1$ , what we
interpret as the dynamical evidence of the bimodal fission in this heavy Fm
isotope.


title:
The Dynamical Structure of the Delta-Resonance and its Effect on Two-
  and Three-Nucleon Systems

abstract:
  The pion-nucleon interaction in the P33 partial wave is assumed to proceed
simultaneously through the excitation of the Delta-isobar and through a
phenomenologically introduced non-resonant background potential. The
introduction of the background potential allows a more realistic
parameterization of the pion-nucleon-Delta vertex compared with the previously
used one without background. It also modifies the propagation of the
Delta-isobar in the nuclear medium and gives rise to novel effective
nucleon-Delta interactions. Their consequences on predictions for observables
in the two-nucleon system at intermediate energies and in the three-nucleon
bound state are studied.


title: Femtometer Toroidal Structures in Nuclei

abstract:
  The two-nucleon density distributions in states with isospin $T=0$, spin
$S$=1 and projection $M_S$=0 and $\pm$1 are studied in $^2$H, $^{3,4}$He,
$^{6,7}$Li and $^{16}$O. The equidensity surfaces for $M_S$=0 distributions are
found to be toroidal in shape, while those of $M_S$=$\pm$1 have dumbbell shapes
at large density. The dumbbell shapes are generated by rotating tori. The
toroidal shapes indicate that the tensor correlations have near maximal
strength at $r<2$ fm in all these nuclei. They provide new insights and simple
explanations of the structure and electromagnetic form factors of the deuteron,
the quasi-deuteron model, and the $dp$, $dd$ and $\alpha d$ $L$=2 ($D$-wave)
components in $^3$He, $^4$He and $^6$Li. The toroidal distribution has a
maximum-density diameter of $\sim$1 fm and a half-maximum density thickness of
$\sim$0.9 fm. Many realistic models of nuclear forces predict these values,
which are supported by the observed electromagnetic form factors of the
deuteron, and also predicted by classical Skyrme effective Lagrangians, related
to QCD in the limit of infinite colors. Due to the rather small size of this
structure, it could have a revealing relation to certain aspects of QCD.


title:
Is it Possible to Describe Short-range NN Correlations in Nuclei on the
  Basis of Nucleonic Degrees of Freedom Only ?

abstract:
  Assuming that NN interaction is modified inside a nucleus by a specific way,
phenomenological effective broad core (BC) NN potential is constructed. It is
shown that increase in the width of repulsive core lets us describe the Coulomb
form factors of few-body nuclei on the basis of nucleonic degrees of freedom
only.


title:
Relativistic Mean-Field Theory and the High-Density Nuclear Equation of
  State

abstract:
  The properties of high-density nuclear and neutron matter are studied using a
relativistic mean-field approximation to the nuclear matter energy functional.
Based on ideas of effective field theory, nonlinear interactions between the
fields are introduced to parametrize the density dependence of the energy
functional. Various types of nonlinearities involving scalar-isoscalar
($\sigma$), vector-isoscalar ($\omega$), and vector-isovector ($\rho$) fields
are studied. After calibrating the model parameters at equilibrium nuclear
matter density, the model and parameter dependence of the resulting equation of
state is examined in the neutron-rich and high-density regime. It is possible
to build different models that reproduce the same observed properties at normal
nuclear densities, but which yield maximum neutron star masses that differ by
more than one solar mass. Implications for the existence of kaon condensates or
quark cores in neutron stars are discussed.


title: Fluctuation dynamics and formation of exotic shape

abstract:
  To study the role of fluctuation in the collisional dynamics, Boltzmann-
Langevin formalism is applied in a two dimensional scenario. The importance of
collective flow towards the formation of hollow structure is exhibited in our
simulation result. The observation of large clusters along the transverse
direction indicates the non-equilibrium aspects of the fragmentation process in
the late stage of the reaction.


title: The effective g_A in the pf-shell

abstract:
  We have calculated the Gamow-Teller matrix elements of 64 decays of nuclei in
the mass range A=41--50. In all the cases the valence space of the full
pf-shell is used. Agreement with the experimental results demands the
introduction of an average quenching factor, q=0.744 +/- 0.015, slightly
smaller but statistically compatible with the $sd$-shell value, thus indicating
that the present number is close to the limit for large A.


title: Some remarks on off-shell scattering in the eikonal approximation

abstract:
  Using the Abel inversion for the eikonal phase as function of the interaction
we derive simple integral relations between half and on-shell eikonal phases. A
frequently used short-range approximation for the half off-shell phase and
profile appears supported by the above-mentioned relation. We work out some
examples and also address the half off-shell eikonal phase pertinent to a
diffractive amplitude. The latter is relevant for a calculation of selected
transparencies ${\cal T}$ of nuclei for a proton, knocked-out in selected
semi-inclusive (SI) $A(e,e'p)X$ reactions. Some numerical results for ${\cal
T}$ are given.


title: Long-Range Correlations and the Momentum Distribution in Nuclei

abstract:
  The influence of correlations on the momentum distribution of nucleons in
nuclei is evaluated starting from a realistic nucleon-nucleon interaction. The
calculations are performed directly for the finite nucleus $\,^{16}$O making
use of the Green's function approach. The emphasis is focused on the
correlations induced by the excitation modes at low energies described within a
model-space of shell-model configurations including states up to the sdg shell.
Our analysis demonstrates that these long-range correlations do not produce any
significant enhancement of the momentum distribution at high missing momenta
and low missing energies. This is in agreement with high resolution $(e,e'p)$
experiments for this nucleus. We also try to simulate the corresponding effects
in large nuclei by quenching the energy-spacing between single-particle orbits.
This yields a sizable enhancement of the spectral function at large momenta and
small energy. Such behavior could explain the deviation of the momentum
distribution from the mean field prediction, which has been observed in
$(e,e'p)$ experiments on heavy nuclei like $^{208}$Pb.


title: Composition and Structure of Protoneutron Stars

abstract:
  We investigate the structure of neutron stars shortly after they are born,
when the entropy per baryon is of order 1 or 2 and neutrinos are trapped on
dynamical timescales. In all cases, the thermal effects for an entropy per
baryon of order 2 or less are small when considering the maximum neutron star
mass. Neutrino trapping, however, significantly changes the maximum mass due to
the abundance of electrons. When matter is allowed to contain only nucleons and
leptons, trapping decreases the maximum mass by an amount comparable to, but
somewhat larger than, the increase due to finite entropy. When matter is
allowed to contain strongly interacting negatively charged particles, in the
form of strange baryons, a kaon condensate, or quarks, trapping instead results
in an increase in the maximum mass of order $0.2M_\odot$, which adds to the
effects of finite entropy. The presence of negatively-charged particles has two
major implications. First, the value of the maximum mass will decrease during
the early evolution of a neutron star as it loses trapped neutrinos, so that if
a black hole forms, it either does so immediately after the bounce or it is
delayed for a neutrino diffusion timescale of $\sim 10$ s. The latter case is
most likely if the maximum mass of the hot star with trapped neutrinos is near
$1.5M_\odot$. In the absence of negatively-charged hadrons, black hole
formation would be due to accretion and therefore is likely to occur only
immediately after bounce. Second, the appearance of hadronic negative charges
results in a general softening of the equation of state that may be observable
in the neutrino luminosities and average energies. Further, these additional
negative charges decrease the electron fraction and may be observed in the
relative excess of electron neutrinos compared to other neutrinos.


title: Light Vector Mesons in Nuclear Matter

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


title:
Reply to Comment of Gazdzicki and Heinz on Strangeness Enhancement in
  $p+A$ and $S+A$

abstract:
  The Comment of Gazdzicki and Heinz is flawed because their assumed baryon
stopping power in $pA$ is inconsistent with data and because they ignored half
the analysis based on the VENUS model. The Comment continues the misleading
presentation of strangeness enhancement by focusing on ratios of integrated
yields. Those ratios discard essential experimental information on the rapidity
dependence of produced $\Lambda$ and obscure discrepancies between different
data sets. Our conclusion remains that the NA35 minimum bias data on
$p+S\rightarrow\Lambda +X $ indicate an anomalous enhancement of central
rapidity strangeness in few nucleon reactions that points to non-equilibrium
dynamics as responsible for strangeness enhancement in nuclear reactions.


title: Realistic effective interactions for halo nuclei

abstract:
  We study halo nuclei using a two-frequency shell-model approach employing
wave functions of two different oscillator constants $\hbar\omega_{in}$ and
$\hbar\omega_{out}$, the former for the inner orbits and the latter for the
halo (outer) orbits. An initial application has been made for the halo nuclei
$^6$He and $^6$Li, with $0s_{1/2}$ taken as the inner and ( $0p_{3/2}$,
$0p_{1/2}$) as the halo orbits. Starting from the Paris NN interaction, we have
derived a G-matrix folded-diagram effective interaction for this two-frequency
model space, using an essentially exact treatment for the Pauli exclusion
operator for the G-matrix. While keeping $\hbar\omega_{in}$ fixed, we have
performed calculations with different choices for $\hbar\omega_{out}$, treating
it as a variation parameter. For $\hbar\omega_{in}=19.7 MeV$ and
$\hbar\omega_{out}=8.2 MeV$, our calculated valence energies for $^6$He and
$^6$Li are -2.77 and -3.55 Mev, respectively, both in good agreement with
experiments. The importance of certain three-body-force diagrams is discussed.


title:
Structure of Low-Energy Collective $0^{-}$-States in Doubly Magic Nuclei
  and Matrix Elements of the P-odd and P- and T-odd Weak Interaction

abstract:
  The structure of the collective low-energy $J^{\pi}=0^{-}$ (T=0 and T=1)
modes is studied for a doubly magic nucleus in a schematic analytic model of
RPA. The $0^{-}$ phonon states ($T= 0,1$) lie at energies $E_{T=0}(0^{-}) \alt
\omega$ and $E_{T=1}(0^{-}) > \omega$, where $\omega$ is the oscillator
frequency. The matrix elements of P-odd and P- and T-odd weak one-body
potentials connecting the ground state to these $0^{-}$-states, $W_{coll}$, are
enhanced by the factor $\sim 2 (\frac{\omega}{E})^{1/2}A^{1/3} \sim 10$ as
compared to the single-particle value $w_{sp}$ what can result in values
$|W_{coll}| \sim 20-30 eV$ if standard values of DDH parameters are used for
$w_{sp}$. Similar enhancement arises in the P- and T-odd case.


title:
Angular and energy dependence of $(e,e^{\prime})$ cross sections for
  orbital 1$^+$ excitations

abstract:
  The main features of the $(e,e^{\prime})$ cross sections of low-lying orbital
excitations with $K^{\pi} = 1^+$ in heavy deformed nuclei are studied in RPA on
the example of $^{156}$Gd. The dependence of the DWBA E2 and M1 cross sections
on the scattering angle $0^{\circ} < \theta < 180 ^{\circ}$ and incident
electron energy $E_i < 210$ MeV is analyzed in PWBA. The cross section is
larger for M1 than for E2 transitions at any angle if $E_i < 30$ MeV. The
longitudinal (Coulomb) C2 excitation dominates the E2 response for $5^{\circ} <
\theta < 170 ^{\circ}$. Only transverse M1 and E2 excitations compete for
$\theta > 175 ^{\circ}$ and the former one is dominant for $q < 1.2$ fm$^{-1}$.
The M1 response is almost purely orbital up to $q = 1.4$ fm$^{-1}$ even in
backward scattering. Qualitative PWBA estimates based on the $q$-dependence of
the form factors alone are not able to predict some important features of the
$(e,e^{\prime})$ cross sections stemming from the strong magnetic and orbital
character of the studied 1$^+$ excitations. The expectation for M1 over E2
dominance in backward scattering should not be extended to higher momentum
transfers and incident energies.


title:
A nonlinear approach to NN interactions using self-interacting meson
  fields

abstract:
  Motivated by the success of models based on chiral symmetry in NN
interactions we investigate self-interacting scalar, pseudoscalar and vector
meson fields and their impact for NN forces. We parametrize the corresponding
nonlinear field equations and get analytic wavelike solutions. A probability
amplitude for the propagation of particle states is calculated and applied in
the framework of a boson-exchange NN potential. Using a proper normalization of
the meson fields makes all self-scattering amplitudes finite. The same
normalization is able to substitute for the phenomenological form factors used
in conventional boson exchange potentials and thus yields an phenomenological
understanding of this part of the NN interaction. We find an empirical scaling
law which relates the meson self-interaction couplings to the pion mass and
self-interaction coupling constant. Our model yields np phase shifts comparable
to the Bonn B potential results and deuteron properties, in excellent agreement
with experimental data.


title:
Effects of the Spin-Orbit and Tensor Interactions on the $M1$ and $E2$
  Excitations in Light Nuclei

abstract:
  The effects of varying the spin-orbit and tensor components of a realistic
interaction on $M1$ excitation rates and $B(E2)'s$ are studied on nuclei in the
$0p$ and $1s-0d$ shells. Not only the total $M1$ but also the spin and orbital
parts separately are studied. The single-particle energies are first calculated
with the same interaction that is used between the valence nucleons. Later this
stringent condition is relaxed somewhat and the $1s$ level is raised relative
to $0d$. For nuclei up to $^{28}Si$, much better results i.e stronger $B(M1)$
rates are obtained by increasing the strength of the spin-orbit interaction
relative to the free value. This is probably also true for $^{32}S$, but
$^{36}Ar$ presents some difficulties. The effects of weakening the tensor
interaction are also studied. On a more subtle level, the optimum spin-orbit
interaction in the lower half of the $s-d$ shell, as far as $M1$ excitations
are concerned, is substantially larger than the difference
$E(J=3/2^+)_1-E(J=5/2^+)_1=5.2~MeV$ in $^{17}O$. A larger spin-orbit splitting
is also needed to destroy the triaxiality in $^{22}Ne$. Also studied are how
much $M1$ orbital and spin strength lies in an observable region and how much
is buried in the grass at higher energies. It is noted that for many nuclei the
sum $B(M1)_{orbital}+B(M1)_{spin}$ is very close to $B(M1)_{total}$, indicating
that the summed cross terms are very small.


title: Numerical Approximation to the Thermodynamic Integrals

abstract:
  We approximate boson thermodynamic integrals as polynomials in two variables
chosen to give the correct limiting expansions and to smoothly interpolate into
other regimes. With 10 free parameters, an accuracy of better than 0.009\% is
achieved for the pressure, internal energy density and the number density. We
also revisit the fermion case, originally addressed by Eggleton, Faulkner and
Flannery (1973), and substantially improve the accuracy of their fits.


title: Final State Charge Exchange Interactions in the $^{12}C(e,e'p)$ Reaction

abstract:
  The $^{12}C(e,e'p)$ reaction is analyzed in a model which explicitly includes
final state interactions due to the coupling of the proton and neutron emission
channels. We find that the effects of the final state interactions due to
charge exchange reactions are important to get a good description of the
symmetry properties of the recently measured Mainz spectral functions. We
discuss the possible role the off-shell effects may play for the correct
interpretation of spectral functions at large positive missing momenta.


title: q- Deformed Boson Expansions

abstract:
  A deformed boson mapping of the Marumori type is derived for an underlying
$su(2)$ algebra. As an example, we bosonize a pairing hamiltonian in a two
level space, for which an exact treatment is possible. Comparisons are then
made between the exact result, our q- deformed boson expansion and the usual
non - deformed expansion.


title: Quantum Correlations in Nuclear Mean Field Theory Through Source Terms

abstract:
  Starting from full quantum field theory, various mean field approaches are
derived systematically. With a full consideration of external source
dependence, the stationary phase approximation of an action gives a nuclear
mean field theory which includes quantum correlation effects (such as
particle-hole or ladder diagram) in a simpler way than the
Brueckner-Hartree-Fock approach. Implementing further approximation, the result
can be reduced to Hartree-Fock or Hartree approximation. The role of the source
dependence in a mean field theory is examined.


title: Flow at AGS Energies: A Barometer for High Density Effects?

abstract:
  Preliminary data on transverse energy `flow' and event asymmetries reported
by the E877(814) collaborations are compared to ARC model calculations for
Au+Au at full AGS beam energy. ARC triple differential cross-sections for
protons and pions are presented. Proton flow is produced in ARC, with the
maximum in-plane momentum about 120 MeV/c. For central events the directed
momentum for pions is near zero, consistent with experiment. Pion momentum
opposite to the nucleons' is evident in a peripheral sample, however,
indicating that this pion `anti-flow' involves absorption by `spectator'
matter. `Squeeze-out' of protons in central events at mid-rapidity is suggested
by the ARC distributions.


title:
Structure of the mirror nuclei $^9$Be and $^9$B in a microscopic cluster
  model

abstract:
  The structure of the mirror nuclei $^9$Be and $^9$B is studied in a
microscopic $\alpha+ \alpha+ n$ and $\alpha+ \alpha+ p$ three-cluster model
using a fully antisymmetrized 9-nucleon wave function. The two-nucleon
interaction includes central and spin-orbit components and the Coulomb
potential. The ground state of $^9$Be is obtained accurately with the
stochastic variational method, while several particle-unbound states of both
$^9$Be and $^9$B are investigated with the complex scaling method.The
calculation for $^9$Be supports the recent identification for the existence of
two broad states around 6.5 MeV, and predicts the $\frac{3}{2}^{-}_2$ and
$\frac{5}{2}^{-}_2$ states at about 4.5 MeV and 8 MeV, respectively. The
similarity of the calculated spectra of $^9$Be and $^9$B enables one to
identify unknown spins and parities of the $^9$B states. Available data on
electromagnetic moments and elastic electron scatterings are reproduced very
well. The enhancement of the $E$1 transition of the first excited state in
$^9$Be is well accounted for. The calculated density of $^9$Be is found to
reproduce the reaction cross section on a Carbon target. The analysis of the
beta decay of $^9$Li to $^9$Be clearly shows that the wave function of $^9$Be
must contain a small component that cannot be described by the simple $\alpha+
\alpha+ n$ model. This small component can be well accounted for by extending a
configuration space to include the distortion of the $\alpha$-particle to $t+p$
and $h+n$ partitions.


title: Double neutral pion photoproduction at threshold

abstract:
  We consider the chiral expansion of the threshold amplitude for the reaction
$\gamma p \to \pi^0 \pi^0 p$ to order ${\cal O}(M_\pi^2)$. We substantiate a
claim that this photoproduction channel is significantly enhanced close to
threshold due to pion loops. A precise measurement of the corresponding cross
sections is called for which allows to test chiral perturbation theory.


title:
Relativistic view on the nuclear effects in the deep inelastic
  scattering on deuteron

abstract:
  We analyze nuclear effects in the deep inelastic scattering on deuteron in
the framework of the covariant approach. It is shown that this approach gives
us the way to investigate the role of relativistic effects in the deep
inelastic scattering (DIS) on deuteron, such as the relativistic kinematics and
the off-mass-shell behavior of the Compton amplitude of nucleon in the
consistent manner. We have obtained that taking into account of the nucleon
amplitude off-mass-shell behavior gives us an analog of the interaction
corrections in nonrelativistic models.