title:
Relativistic versus Nonrelativistic Optical Potentials in A(e,e'p)B
  Reactions

abstract:
  We investigate the role of relativistic and nonrelativistic optical
potentials used in the analysis of ($e,e'p$) data. We find that the
relativistic calculations produce smaller ($e,e'p$) cross sections even in the
case in which both relativistic and nonrelativistic optical potentials fit
equally well the elastic proton--nucleus scattering data. Compared to the
nonrelativistic impulse approximation, this effect is due to a depletion in the
nuclear interior of the relativistic nucleon current, which should be taken
into account in the nonrelativistic treatment by a proper redefinition of the
effective current operator.


title:
Reply to "Comment on 'Comparison of potential models with the
  pp-scattering data below 350 MeV.' "

abstract:
  Replying to the above Comment by G.Q.Li and R.Machleidt, we point out that
the supposed "flaws" in our Comparison of NN potential models with the pp-
scattering data [ Phys.Rev.C47,761(1993) ] are in reality not flaws at all.


title:
Cluster Structure of Disoriented Chiral Condensates in Rapidity
  Distribution

abstract:
  We study the creation of disoriented chiral condensates with some initial
boundary conditions that may be expected in the relativistic heavy ion
collisions. The equations of motion in the linear $\sigma$-model are solved
numerically with and without a Lorentz-boost invariance. We suggest that a
distinct cluster structure of coherent pion production in the rapidity
distribution may emerge due to a quench and may be observed in experiments.


title: A Quark Model of Lambdabar-Lambda Production of Pbar-P Interactions

abstract:
  A quark model which includes both scalar and vector contributions to the
reaction mechanism (SV quark model) is used in a DWBA calculation of $\bar
\Lambda \Lambda$ production in $\bar p p$ interractions. Total and differential
cross-sections, polarizations, depolarizations, and spin-correlattion
coefficients are computed for laboratory momenta from threshold to 1695 MeV/c.
The free parameters of the calculation are the scalar and vector strengths, a
quark cluster size parameter,and the parameters of the unknown $\bar \Lambda
\Lambda$ potentials. Good agreement with experiment is found for constructive
interference of the scalar and vector terms, and for $\bar \Lambda \Lambda$
potentials which differ from those suggested by several authors on the basis of
SU(3) arguments. The fit to the data is better than that obtained by other
quark models, which use only scalar $or$ vector annihilation terms. The
agreement with experiment is also better than that found in meson-exchange
models. The recent suggestion[1] that measurement of the depolarization
parameter $D_{nn}$ can be used to discriminatebetween meson-exchange and quark
models is examined in detail. We conclude that a measurement of $D_{nn}$ will
provide a test of which of these models, as presently constructed,is the more
appropriate description of strangeness production in the $\bar p p \ rightarrow
\bar \Lambda \Lambda$ reaction.


title:
Double Beta Decay in pn-QRPA Model with Isospin and SU(4) Symmetry
  Constraints

abstract:
  The transition matrix elements for the $0^{+}\to 0^{+}$ double beta decays
are calculated for $^{48}Ca$, $^{76}Ge $, $^{82}Se$, $^{100}Mo$, $^{128}Te$ and
$^{130}Te$ nuclei, using a ${\delta}$-interaction. As a guide, to fix the
particle-particle interaction strengths, we exploit the fact that the missing
symmetries of the mean field approximation are restored in the random phase
approximation by the residual interaction. Thus, the T=1, S=0 and T=0, S=1
coupling strengths have been estimated by invoking the partial restoration of
the isospin and Wigner SU(4) symmetries, respectively. When this recipe is
strictly applied, the calculation is consistent with the experimental limit for
the $2\nu$ lifetime of $^{48}Ca$ and it also correctly reproduces the $2\nu$
lifetime of $^{82}Se$. In this way, however, the two-neutrino matrix elements
for the remaining nuclei are either underestimated (for $^{76}Ge$ and
$^{100}Mo$) or overestimated (for $^{128}Te$ and $^{130}Te$) approximately by a
factor of 3. With a comparatively small variation ($<10%$) of the spin-triplet
parameter, near the value suggested by the SU(4) symmetry, it is possible to
reproduce the measured $T_{1/2}^{2\nu}$ in all the cases. The upper limit for
the effective neutrino mass, as obtained from the theoretical estimates of
$0\nu$ matrix elements, is $<m_{\nu}>\cong 1$ eV. The dependence of the nuclear
matrix elements on the size of the configuration space has been also analyzed.


title: The Multifragmentation Freeze--Out Volume in Heavy Ion Collisions

abstract:
  The reduced velocity correlation function for fragments from the reaction Fe
+ Au at 100 A~MeV bombarding energy is investigated using the
dynamical--statistical approach QMD+SMM and compared to experimental data to
extract the Freeze--Out volume assuming simultaneous multifragmentation.


title: Interference Effects in Relativistic Deuteron Electrodisintegration

abstract:
  We extend the relativistic plane--wave impulse approximation formalism to
incorporate a specific class of relativistic interference effects for use in
describing inclusive electrodisintegration of $^2$H. The role of these
``exchange'' terms for the various response functions accessible in
parity--conserving and --violating inclusive processes is investigated and
shown, especially for the latter, to have important consequences for
experiment. An extension to a simple quasi--deuteron model is also considered.


title:
What can we learn from a second phi meson peak in ultrarelativistic
  nuclear collisions?

abstract:
  The decay width of a phi meson is reduced from its vacuum value as its mass
decreases in hot hadronic matter as a result of the partial restoration of
chiral symmetry. This reduction is, however, cancelled by collisional
broadening through the reactions $\phi\pi\to KK^*$, $\phi K\to\phi K$,
$\phi\rho\to KK$, and $\phi\phi\to KK$. The resulting phi meson width in hot
hadronic matter is found to be less than about 10 MeV for temperatures below
200 MeV. If hadronic matter has a strong first-order phase transition, this
narrow phi meson with reduced mass will appear as a second peak in the dilepton
spectrum in ultrarelativistic heavy ion collisions. We discuss use of this
second phi peak to determine the transition temperature and the lifetime of the
two-phase coexistence region in the case of a strong first-order phase
transition. We also discuss using the peak to determine the range of
temperatures over which the transition occurs in the case of a smooth but fast
change in the entropy density.


title:
Superdeformed rotational bands in the Mercury region; A Cranked
  Skyrme-Hartree-Fock-Bogoliubov study

abstract:
  A study of rotational properties of the ground superdeformed bands in \Hg{0},
\Hg{2}, \Hg{4}, and \Pb{4} is presented. We use the cranked
Hartree-Fock-Bogoliubov method with the {\skm} parametrization of the Skyrme
force in the particle-hole channel and a seniority interaction in the pairing
channel. An approximate particle number projection is performed by means of the
Lipkin-Nogami prescription. We analyze the proton and neutron quasiparticle
routhians in connection with the present information on about thirty presently
observed superdeformed bands in nuclei close neighbours of \Hg{2}.


title: S-wave $\pi$-Nucleus Repulsion and Dirac Phenomenology

abstract:
  A relativistic $\pi$-nucleon potential is extended to $m^* \neq m$ to
investigate the possibility of generating s-wave $\pi$-nucleus repulsion. We
find that relativity does indeed generate significant repulsion, the exact
amount depending on the details of the calculation. In contradistinction the
$t\rho$ approximation gives very little repulsion.


title: RPA equations and the instantaneous Bethe-Salpeter equation

abstract:
  We give a derivation of the particle-hole RPA equations for an interacting
multi-fermion system by applying the instantaneous approximation to the
amputated two-fermion propagator of the system. In relativistic field theory
the same approximation leads from the fermion-antifermion Bethe-Salpeter
equation to the Salpeter equation. We show that RPA equations and Salpeter
equation are indeed equivalent.


title: On the angular momentum dependence of nuclear level densities

abstract:
  Angular momentum dependence of nuclear level densities at finite temperatures
are investigated in the static path approximation(SPA) to the partition
function using a cranked quadrupole interaction Hamiltonian in the following
three schemes: (i) cranking about x-axis, (ii) cranking about z-axis and (iii)
cranking about z-axis but correcting for the orientation fluctuation of the
axis. Performing numerical computations for an $sd$ and a $pf$ shell nucleus,
we find that the x-axis cranking results are satisfactory for reasonably heavy
nuclei and this offers a computationally faster method to include the angular
momentum dependence at high temperatures in the SPA approach. It also appears
that at high spins inclusion of orientation fluctuation correction would be
important.


title: Semiclassical Quark Model Of the Nuclear Matter Response

abstract:
  The longitudinal response function $R(q,w)$\ of nuclear matter is calculated
in a semiclassical quark model. The model has a many- body string-flip
potential that confines quarks into hadrons and avoids color van der Waals
forces. Molecular dynamics simulations are used to calculate $R(q,w)$\ in one
space dimension for a variety of momentum transfers $q$\ and excitation
energies $w$. The response function decreases with density (compared to a free
hadron response) because of quark exchange between hadrons.


title: Theory of Coupled Pion--Trinucleon Systems

abstract:
  We derive the dynamical equations which consistently couple the four--body
($\pi$NNN) system to the underlying three--nucleon system. Our treatment can be
considered the proper generalization of the Afnan--Blankleider equations for
the coupled NN--$\pi$NN system. The resulting connected--kernel equation
resembles in structure the Yakubovskii--Grassberger--Sandhas equation for the
standard four--body problem, but involves 24 chain--labelled components (rather
than the usual 18 ones) and allows for a consistent evaluation of reaction
amplitudes involving $\pi$ absorption/production.


title: Complex Conjugate Pairs in Stationary Sturmians

abstract:
  Sturmian eigenstates specified by stationary scattering boundary conditions
are particularly useful in contexts such as forming simple separable two
nucleon t matrices, and are determined via solution of generalised eigenvalue
equation using real and symmetric matrices. In general, the spectrum of such an
equation may contain complex eigenvalues. But to each complex eigenvalue there
is a corresponding conjugate partner. In studies using realistic
nucleon--nucleon potentials, and in certain positive energy intervals, these
complex conjugated pairs indeed appear in the Sturmian spectrum. However, as we
demonstrate herein, it is possible to recombine the complex conjugate pairs and
corresponding states into a new, sign--definite pair of real quantities with
which to effect separable expansions of the (real) nucleon--nucleon reactance
matrices.


title:
On the nature of the large-$q$ expansion of the response for a
  non-relativistic confined system

abstract:
  We show the equivalence of a previously derived exact expression for the
response of a non-relativistic system with harmonic forces and an infinite sum
of weighted $\delta$-functions corresponding to the spectrum. We forward
arguments, indicating that the Gersch-Rodriguez-Smith $1/q$-expansion of the
response does not converge and prove that this expansion is an asymptotic
series.


title:
The nuclear component of the EMC effect beyond the Plane Wave Impulse
  Approximation

abstract:
  We study the response of a nucleus composed of nucleons and confined quarks.
Assuming dynamics implied by a non-relativistic cluster model, we prove that
the total response is a convolution of the responses of, respectively, a
nucleus with interacting point-nucleons and an isolated nucleon with confined
quarks. Defining as an intermediary structure functions in terms of the
non-relativistic limit of light-cone variables, we subsequently conjecture a
generalization to the relativistic regime. That result contains a nuclear part
with full inter-nucleon dynamics and allows the study of approximations, as are
the Plane Wave Impulse Approximation and a modification of it. The framework
also permits a clean treatment of the response of a moving composite nucleon in
the nucleus which may be off-shell.


title:
Chaos Driven Decay of Nuclear Giant Resonances: Route to Quantum
  Self-Organization

abstract:
  The influence of background states with increasing level of complexity on the
strength distribution of the isoscalar and isovector giant quadrupole resonance
in $^{40}$Ca is studied. It is found that the background characteristics,
typical for chaotic systems, strongly affects the fluctuation properties of the
strength distribution. In particular, the small components of the wave function
obey a scaling law analogous to self-organized systems at the critical state.
This appears to be consistent with the Porter-Thomas distribution of the
transition strength.


title: Meson phase space density from interferometry

abstract:
  The interferometric analysis of meson correlations provides a measure of the
average phase space density of the mesons in the final state. This quantity is
a useful indicator of the statistical properties of the system, and it can be
extracted with a minimum of model assumptions. Values obtained from recent
measurements are consistent with the thermal value, but do not rule out
superradiance effects.


title:
Dynamical Color Correlations in a $SU(2)_c$ Quark Exchange Model of
  Nuclear Matter

abstract:
  The quark exchange model is a simple realization of an adiabatic
approximation to the strong-coupling limit of Quantum Chromodynamics (QCD): the
quarks always coalesce into the lowest energy set of flux tubes. Nuclear matter
is thus modeled in terms of its quarks. We wish to study the correlations
imposed by total wavefunction antisymmetry when color degrees of freedom are
included. To begin with, we have considered one-dimensional matter with a
$SU(2)$ color internal degree of freedom only. We proceed by constructing a
totally antisymmetric, color singlet {\it Ansatz} characterized by a
variational parameter $\lambda$ (which describes the length scale over which
two quarks in the system are clustered into hadrons) and by performing a
variational Monte Carlo calculation of the energy to optimize $\lambda$ for a
fixed density. We calculate the $q-q$ correlation function as well, and discuss
the qualitative differences between the system at low and high density.


title:
Relativistically generated asymmetry in the missing momentum
  distribution from the $(e,e'p)$ reaction

abstract:
  We calculate the asymmetry in the missing-momentum distribution from the
$(e,e'p)$ reaction in a relativistic formalism. Longitudinal and transverse
response functions are evaluated in parallel kinematics as a function of the
three-momentum transfer to the nucleus. Analytic expressions for the responses
are obtained in a relativistic plane-wave impulse approximation. These
expressions reveal a large asymmetry in the momentum distribution, at the
plane-wave level, induced by the lower components of the bound-state wave
functions. These relativistic effects contaminate any attempt to infer color
transparency from a measurement of the asymmetry in the $(e,e'p)$ reaction.


title:
Searching for Color Coherent Effects at Intermediate $Q^2$ via Double
  Scattering Processes

abstract:
  We propose that measuring the $Q^2$ dependence of the number of final-state
interactions of the recoil protons in quasi-elastic electron scattering from
light nuclei is a new method to investigate Color Coherent effects at {\bf
intermediate} values of $Q^2$ ({$\sim$ few $(GeV/c)^2$}). This is instead of
measuring events without final-state interactions. Our calculations indicate
that such measurements could reveal significant color transparency effects for
the highest of the energies initially available at CEBAF. Measurements that
detect more than one hadron in the final state, which require the use of large
acceptance ($4\pi$) detectors, are required.


title: Properties of the phi meson at finite temperature

abstract:
  We calculate the $\phi$-meson propagator at finite temperature at the
one--loop order. The real and imaginary parts are studied separately in full
kinematic ranges. From this activity we investigate how temperature affects
such things as decay widths and dispersion relations. {}From here we estimate
the thermal rate of lepton pair radiation in a hadron gas proceeding through
$K^{+}K^{-}\to \phi \to \ell^{+}\ell^{-}$ and $\pi\rho\to \phi \to
\ell^{+}\ell^{-}$. We find several interesting things. From the dispersion
relations we learn the effective mass calculated this way increases with
temperature as does the partial width, but only slightly. At $T=200$ MeV, the
mass increases by $\sim$ 4 MeV and the partial width increases by 34\%.
Polarizations are indistinguishable for practical purposes.


title: Baryon-Baryon Interactions

abstract:
  After a short survey of some topics of interest in the study of baryon-baryon
scattering, the recent Nijmegen energy dependent partial wave analysis (PWA) of
the nucleon-nucleon data is reviewed. In this PWA the energy range for both pp
and np is now 0 < Tlab < 350 MeV and a chi^2_{d.o.f.}=1.08 was reached. The
implications for the pion-nucleon coupling constants are discussed. Comments
are made with respect to recent discussions around this coupling constant in
the literature. In the second part, we briefly sketch the picture of the baryon
in several, more or less QCD-based, quark-models that have been rather
prominent in the literature. Inspired by these pictures we constructed a new
soft-core model for the nucleon-nucleon interaction and present the first
results of this model in a chi^2 -fit to the new multi-energy Nijmegen PWA.
With this new model we succeeded in narrowing the gap between theory and
experiment at low energies. For the energies Tlab = 25-320 MeV we reached a
record low chi^2_{p.d.p.} = 1.16. We finish the paper with some conclusions and
an outlook describing the extension of the new model to baryon-baryon
scattering.


title:
Three-body resonances in He-6, Li-6, and Be-6, and the soft dipole mode
  problem of neutron halo nuclei

abstract:
  Using the complex scaling method, the low-lying three-body resonances of
$^6$He, $^6$Li, and $^6$Be are investigated in a parameter-free microscopic
three-cluster model. In $^6$He a 2$^+$, in $^6$Li a 2$^+$ and a 1$^+$, and in
$^6$Be the 0$^+$ ground state and a 2$^+$ excited state is found. The other
experimentally known 2$^+$ state of $^6$Li cannot be localized by our present
method. We have found no indication for the existence of the predicted 1$^-$
soft dipole state in $^6$He. We argue that the sequential decay mode of $^6$He
through the resonant states of its two-body subsystem can lead to peaks in the
excitation function. This process can explain the experimental results in the
case of $^{11}$Li, too. We propose an experimental analysis, which can decide
between the soft dipole mode and the sequential decay mode.


title: Dilepton Production in Nucleon-Nucleon Interactions

abstract:
  Starting from a realistic one--boson--exchange--model fitted to the
amplitudes of elastic nucleon--nucleon scattering and the process
$NN\rightarrow N\Delta$ we perform a fully relativistic and gauge invariant
calculation for the dilepton production in nucleon--nucleon collisions,
including the important effect of propagating the $\Delta$--resonance. We
compare the results of our calculations with the latest experimental data on
dilepton production. We also show how to implement various electromagnetic
formfactors for the hadrons in our calculations without loosing
gauge--invariance and discuss their influence on dilepton spectra.


title: Resistance to Collapse: The Tensor Interaction

abstract:
  We consider negative-parity excitations in $^4\mbox{He}$, $J^{\pi}$=$0^-$ and
$1^-$ with isospin $T$=$0$ and $T$=$1$. We show tha t, in contrast to
one-particle one-hole results, in a shell model diagonalization none of the
above collapses to zero energy as the strength of the tensor interaction is
increased.


title:
Analysis of Subthreshold Antiproton Production in p-Nucleus and
  Nucleus-Nucleus Collisions in the RBUU Approach

abstract:
  We calculate the subthreshold production of antiprotons in the
Lorentz-covariant RBUU approach employing a weighted testparticle method to
treat the antiproton propagation and absorption nonperturbatively. We find that
the pbar differential cross sections are highly sensitive to the baryon and
antiproton selfenergies in the dense baryonic environment. Adopting the baryon
scalar and vector selfenergies from the empirical optical potential for
proton-nucleus elastic scattering and from Dirac-Brueckner calculations at
higher density rho > rho_0 we examine the differential pbar spectra as a
function of the antiproton selfenergy. A detailed comparison with the available
experimental data for p-nucleus and nucleus-nucleus reactions shows that the
antiproton feels a moderately attractive mean-field at normal nuclear matter
density rho_0 which is in line with a dispersive potential extracted from the
free annihilation cross section.


title: Relativistic Coulomb Sum Rules for $(e,e^\prime)$

abstract:
  A Coulomb sum rule is derived for the response of nuclei to $(e,e^\prime)$
scattering with large three-momentum transfers. Unlike the nonrelativistic
formulation, the relativistic Coulomb sum is restricted to spacelike
four-momenta for the most direct connection with experiments; an immediate
consequence is that excitations involving antinucleons, e.g., $N{\bar N}$ pair
production, are approximately eliminated from the sum rule. Relativistic recoil
and Fermi motion of target nucleons are correctly incorporated. The sum rule
decomposes into one- and two-body parts, with correlation information in the
second. The one-body part requires information on the nucleon momentum
distribution function, which is incorporated by a moment expansion method. The
sum rule given through the second moment (RCSR-II) is tested in the Fermi gas
model, and is shown to be sufficiently accurate for applications to data.


title: Missing and Quenched Gamow Teller Strength

abstract:
  Gamow-Teller strength functions in full $(pf)^{8}$ spaces are calculated with
sufficient accuracy to ensure that all the states in the resonance region have
been populated. Many of the resulting peaks are weak enough to become
unobservable. The quenching factor necessary to bring into agreement the low
lying observed states with shell model predictions is shown to be due to
nuclear correlations. To within experimental uncertainties it is the same that
is found in one particle transfer and (e,e') reactions. Perfect consistency
between the observed $^{48}Ca(p,n)^{48}Sc$ peaks and the calculation is
achieved by assuming an observation threshold of 0.75\% of the total strength,
a value that seems typical in several experiments


title: Role of the $a_1$ meson in dilepton production from hot hadronic matter

abstract:
  Dilepton production from hot hadronic matter is studied in an effective
chiral Lagrangian with pions, $\rho$-mesons, and $a_1$ mesons, We find that the
production rates from reactions that involve axial-vector mesons dominate over
contributions from all other reactions when the dilepton invariant mass is
above 1.5 GeV.


title: Correlation Dynamics of Green's Functions

abstract:
  We generalize the methods used in the theory of correlation dynamics and
establish a set of equations of motion for many-body correlation green's
functions in the non-relativistic case. These non-linear and coupled equations
of motion describe the dynamical evolution of correlation green's functions of
different order and transparently show how many-body correlations are generated
by the different interaction terms in a genuine nonperturbative framework. The
nonperturbative results of the conventional green's function theory are
included in the present formalism as two limiting cases (the so-called ladder
diagram summation and ring diagram summation) as well as the familiar
correlation dynamics of density-matrices in the equal time limit. We present
explicit expressions for three- and four-body correlation functions that can be
used to dynamically restore the trace relations for spin-symmetric fermi
systems and study numerically the relative importance of two-, three- and
four-body correlations for nuclear configurations close to the groundstate.


title:
On the energy-shell contributions of the three-particle~-~ three-hole
  excitations

abstract:
  The response functions for the extended second and third random phase
approximation are compared. A second order perturbation calculation shows that
the first-order amplitude for the direct $3p3h$ excitation from the ground
state cancels with those that are engendered by the $1p1h$-$3p3h$ coupling. As
a consequence nonvanishing $3p3h$ effects to the $1p1h$ response involve off
energy shell renormalization only. On shell $3p3h$ processes are absent.


title: Meson Photo- and Electroproduction

abstract:
  Photo- and electroproduction of pions and eta-mesons is studied on the
nucleon. The formalism of such reactions is presented including polarization
degrees of freedom and theoretical approaches are discussed. In particular, the
threshold and $\Delta$-resonance region of pion photoproduction is considered
and recent developments on low energy theorems (LET) and the E2/C2 quadrupole
excitation of the $\Delta$ are presented. For eta photoproduction we show our
calculations for the threshold region of the new Mainz experiment and
demonstrate the sensitivity of this reaction to the elementary $\eta NN$
coupling and the resonance parameters of the $S_{11}(1535)$. In nuclear
applications we point out the importance and advantage of light nuclei as $d$,
$^3H$, $^3He$ and $^4He$ for the isospin structure of the reactions as well as
for medium effects of the nucleon resonances.


title: Simple Formula for Nuclear Charge Radius

abstract:
  A new formula for the nuclear charge radius is proposed, dependent on the
mass number (A) and neutron excess (N-Z) in the nucleus. It is simple and it
reproduces all the experimentally available mean square radii and their
isotopic shifts of even--even nuclei much better than other frequently used
relations.


title: Seeing the QCD phase transition with phi mesons

abstract:
  A double phi peak structure in the dilepton invariant mass spectrum from
ultrarelativistic heavy ion collisions is proposed as a signal for the phase
transition from the quark-gluon plasma to the hadronic matter. The low mass phi
peak results from the decay of phi mesons with reduced in-medium mass during
the transition. Furthermore, the measurement of the transverse momentum
distribution of these low mass phi mesons offers a viable means for determining
the temperature of the phase transition.


title: Electroproductions of Light $\Lambda$- and $\Sigma$-Hypernuclei

abstract:
  Theoretical estimations of production cross sections of light $\Lambda$ and
$\Sigma$ hypernuclei in $(e,e'K^{+})$ reactions at around CEBAF energies are
given. Because of dominant spin-flip amplitudes and large momentum transfers,
unnatural parity states and stretched states of hypernuclei are favorably
excited. They are compared with quasifree hyperon productions.


title: QCD Evolution by Finite Element Methods

abstract:
  A simple, new method for solving for the $Q^2$ evolution of parton
distributions in perturbative QCD using cubic splines is described and applied
to the evolution of nonsinglet quark distributions.


title: Novel soft-photon analysis of $pp\gamma$ below pion-production threshold

abstract:
  A novel soft-photon amplitude is proposed to replace the conventional Low
soft-photon amplitude for nucleon-nucleon bremsstrahlung. Its derivation is
guided by the standard meson-exchange model of the nucleon-nucleon interaction.
This new amplitude provides a superior description of $pp\gamma$ data. The
predictions of this new amplitude are in close agreement with potential-model
calculations, which implies that, contrary to conclusions drawn by others,
off-shell effects are essentially insignificant below pion-production
threshold.


title: Power Moments and Scaling Properties of Nuclear Emulsion Data

abstract:
  Various features of the charge yield in heavy ion collisions are studied.
Considered here are the nuclear emulsion data of $^{84}$Kr, $^{131}$Xe,
$^{197}$Au, $^{238}$U in the energy range of 1 GeV/A. Mean charge yields and
multiplicity distribution of these data indicate that the nuclear fragmentation
at this energy is a multiprocess phenomena. Power moments of the charge
distribution exhibit a scale invariance. While small nuclei (Kr and Xe) show a
nuclear size dependence, large nuclei (Au and U) exhibit scale independence in
their charge distribution.


title: Nuclear Anapole Moments in Single Particle Approximation

abstract:
  Nuclear anapole moments of $\;^{133}$Cs, $\;^{203,205}$Tl, $\;^{207}$Pb,
$\;^{209}$Bi are treated in the single-particle approximation. Analytical
results are obtained for the oscillator potential without spin-orbit
interaction. Then the anapole moments are calculated numerically in a
Woods-Saxon potential which includes spin-orbit interaction. The results
obtained demonstrate a remarkable stability of nuclear anapole moment
calculations in the single-particle approximation.


title: Suppression of Hadroproduction in Nuclei

abstract:
  We argue that nuclei are not transparent for fast projectile partons. Color
transparency is effective for final state interactions in heavy particle
production, though nuclear filtering of initial partons can reduce the cross
sections. We show that short-ranged initial state interactions, which have been
neglected so far, can be important in hadroproduction on nuclei. With the
present scenario of hadroproduction a qualitative description of data can be
obtained.


title: Antisymmetrization of a Mean Field Calculation of the T-Matrix

abstract:
  The usual definition of the prior(post) interaction $V(V^\prime )$ between
projectile and target (resp. ejectile and residual target) being contradictory
with full antisymmetrization between nucleons, an explicit antisymmetrization
projector ${\cal A}$ must be included in the definition of the transition
operator, $ T\equiv V^\prime{\cal A}+V^\prime{\cal A}GV. $ We derive the
suitably antisymmetrized mean field equations leading to a non perturbative
estimate of $T$. The theory is illustrated by a calculation of forward
$\alpha$-$\alpha$ scattering, making use of self consistent symmetries.


title:
The E2 contribution to the 8B -> p + 7Be Coulomb dissociation cross
  section

abstract:
  We have calculated the E1 and E2 contributions to the low-energy B-8 + Pb-208
-> p + Be-7 + Pb-208 Coulomb dissociation cross sections using the kinematics
of a recent experiment at RIKEN. Using a potential model description of the
Be-7 (p,gamma) B-8 reaction, we find that the E2 contributions cannot a priori
be ignored in the analysis of the data. Its inclusion reduces the extracted
Be-7 (p,gamma) B-8 S-factor at solar energies by about 25%.


title:
The inverse Laplace transform as the ultimate tool for transverse mass
  spectra

abstract:
  New high statistics data from the second generation of ultrarelativistic
heavy-ion experiments open up new possibilities in terms of data analysis. To
fully utilize the potential we propose to analyze the $m_\perp$-spectra of
hadrons using the inverse Laplace transform. The problems with its inherent
ill-definedness can be overcome and several applications in other fields like
biology, chemistry or optics have already shown its feasability. Moreover, the
method also promises to deliver upper bounds on the total information content
of the spectra, which is of big importance for all other means of analysis.
Here we compute several Laplace inversions from different thermal scenarios,
both analytically and numerically, to test the efficiency of the method.
Especially the case of a two component structure, related to a possible first
order phase transition to a quark gluon plasma, is closer investigated and it
is shown that at least a signal to noise ratio of $10^4$ is necessary to
resolve two individual components.


title: Can the $\Sigma^- nn$ System be Bound?

abstract:
  Motivated by the $\Sigma$-hypernuclear states reported in ($K^-,\pi^{\pm}$)
experiments, we have explored the possibility that there exists a
particle-stable $\Sigma^- nn$ bound state. For the J\"ulich \~A
hyperon-nucleon, realistic-force model, our calculations yield little reason to
expect a positive-parity bound state in either the $J = \frac{1}{2}$ or the $J
= \frac{3}{2}$ channels.


title:
Complete 0 hbar omega calculations of Gamow-Teller strengths for nuclei
  in the iron region

abstract:
  Gamow-Teller strengths for selected nuclei in the iron region (A~56) have
been investigated via shell-model Monte Carlo calculations with realistic
interactions in the complete fp basis. Results for all cases show significant
quenching relative to single-particle estimates, in quantitative agreement with
(n,p) data. The J=1,T=0 residual interaction and the f_{7/2}-f_{5/2} spin-orbit
splitting are shown to play major roles in the quenching mechanism. Calculated
B(E2, 2^+_1 -> 0^+_1) values are in fair agreement with experiment using
effective charges of e_p=1.1e and e_n=0.1e.


title: The y-scaling in the Delta-region

abstract:
  A scaling variable for electron scattering off nuclei in the Delta-region is
shown to exist. A scaling law for a large variety of scattering data with
different kinematics is found. This property turns out to be very sensitive to
the reaction mechanism. We will show that this outcome follows from drastic
medium induced modifications on the momentum and energy dependence of the Delta
width.


title:
The Nucleon-Nucleon Potential in the Chromo-Dielectric Soliton Model:
  Statics

abstract:
  We study the N-N interaction in the framework of the chromo-dielectric
soliton model. Here, the long-range parts of the nonabelian gluon
self-interactions are assumed to give rise to a color-dielectric function which
is parameterized in terms of an effective scalar background field. The
six-quark system is confined in a deformed mean field through an effective
non-linear interaction between the quarks and the scalar field. The CDM is
covariant, respects chiral invariance, leads to absolute color confinement and
is free of the spurious long range Van der Waals forces which trouble
non-relativistic investigations employing a confining potential. Six-quark
molecular-type configurations are generated as a function of deformation and
their energies are evaluated in a coupled channel analysis. By using molecular
states instead of cluster model wave functions, all important six-quark
configurations are properly taken into account. The corresponding Hamiltonian
includes the effective interaction between the quarks and the scalar background
field and quark-quark interactions generated through one gluon exchange treated
in Coulomb gauge. When evaluating the gluonic propagators, the inhomogeneity
and deformation of the dielectric medium are taken into account. Results for
the adiabatic nucleon-nucleon potential are presented, and the various
contributions are discussed. Finally, an outlook is given on how, in the next
stage of our investigation, the dynamical effects will be incorporated by
employing the generator coordinate method.


title: Systematics of Gamow-Teller strengths in mid-fp-shell nuclei

abstract:
  We show that the presently available data on the Gamow-Teller (GT) strength
in mid-fp-shell nuclei are proportional to the product of the numbers of
valence protons and neutron holes in the full fp-shell. This observation leads
to important insights into the mechanism for GT quenching and to a simple
parametrization of the Gamow-Teller strengths important for electron capture by
fp-shell nuclei in the early stage of supernovae.


title: Covariant three-body equations in phi^3 field theory

abstract:
  We derive four-dimensional relativistic three-body equations for the case of
a field theory with a three-point interaction vertex. These equations describe
the coupled 2->2, 2->3, and 3->3 processes, and provide the means of
calculating the kernel of the 2->2 Bethe-Salpeter equation. Our equations
differ from all previous formulations in two essential ways. Firstly, we have
overcome the overcounting problems inherent in earlier works. Secondly, we have
retained all possible two-body forces when one particle is a spectator. In this
respect, we show how it is necessary to also retain certain three-body forces
as these can give rise to (previously overlooked) two-body forces when used in
a 2->3 process. The revealing of such hidden two-body forces gives rise to a
further novel feature of our equations, namely, to the appearance of a number
of subtraction terms. In the case of the piNN system, for example, the NN
potential involves a subtraction term where two pions, exchanged between the
nucleons, interact with each other through the pi-pi t-matrix. The necessity of
an input pi-pi interaction is surprising and contrasts markedly with the
corresponding three-dimensional description of the piNN system where no such
interaction explicitly appears. This illustrates the somewhat unexpected result
that the four-dimensional equations differ from the three-dimensional ones even
at the operator level.


title: Convolution approach to the piNN system

abstract:
  The unitary NN-piNN model contains a serious theoretical flaw: unitarity is
obtained at the price of having to use an effective piNN coupling constant that
is smaller than the experimental one. This is but one aspect of a more general
renormalization problem whose origin lies in the truncation of Hilbert space
used to derive the equations. Here we present a new theoretical approach to the
piNN problem where unitary equations are obtained without having to truncate
Hilbert space. Indeed, the only approximation made is the neglect of connected
three-body forces. As all possible dressings of one-particle propagators and
vertices are retained in our model, we overcome the renormalization problems
inherent in previous piNN theories. The key element of our derivation is the
use of convolution integrals that have enabled us to sum all the possible
disconnected time-ordered graphs. We also discuss how the convolution method
can be extended to sum all the time orderings of a connected graph. This has
enabled us to calculate the fully dressed NN one pion exchange potential. We
show how such a calculation can be used to estimate the size of the connected
three-body forces neglected in the new piNN equations. Early indications are
that such forces may be negligible.


title: Algebraic models of hadron structure: I. Nonstrange baryons

abstract:
  We introduce an algebraic framework for the description of baryons. Within
this framework we study a collective string-like model and show that this model
gives a good overall description of the presently available data. We discuss in
particular masses and electromagnetic couplings, including the transition form
factors that can be measured at new electron facilities.


title: Pseudo SU(3) Model and Abnormal Parity States

abstract:
  The most important features of the pseudo SU(3) model are reviewed. This
description of heavy deformed nuclei is based on pseudo spin symmetry, and is
able to correctly predict the collective spectra and their transition
amplitudes, using appropriate effective charges. It also gives a very good
description of the exotic double beta decay, a hard test of any nuclear model.
The simplest pseudo SU(3) assumptions describe nucleons in the abnormal parity
states as having seniority zero. This idea is very useful as a mathematical
simplification, and is also able to give a nice description of the backbending
phenomena, but has been challenged in a recent study about effective charges
and $BE2(0^+_1 \rightarrow 2^+_1)$ systematics. We carefully checked this
statement and conclude that the seniority zero approach is a formal way of
assign abnormal parity nucleons a passive role. The contribution of the
abnormal parity nucleons to the nuclear quadrupole moments is finite but only a
fraction of their asymptotic Nilsson values.


title: Meson Condensation in Dense Matter Revisited

abstract:
  The results for meson condensation in the literature vary markedly depending
on whether one uses chiral perturbation theory or the current-algebra-plus-PCAC
approach. To elucidate the origin of this discrepancy, we re-examine the role
of the sigma-term in meson condensation. We find that the resolution of the
existing discrepancy requires a knowledge of terms in the Lagrangian that are
higher order in density than hitherto considered.


title:
Shadowing, Binding and Off-Shell Effects in Nuclear Deep Inelastic
  Scattering

abstract:
  We present a unified description of nuclear deep inelastic scattering (DIS)
over the whole region $0<x<1$ of the Bjorken variable. Our approach is based on
a relativistically covariant formalism which uses analytical properties of
quark correlators. In the laboratory frame it naturally incorporates two
mechanisms of DIS: (I) scattering from quarks and antiquarks in the target and
(II) production of quark-antiquark pairs followed by interactions with the
target. We first calculate structure functions of the free nucleon and develop
a model for the quark spectral functions. We show that mechanism (II) is
responsible for the sea quark content of the nucleon while mechanism (I)
governs the valence part of the nucleon structure functions. We find that the
coherent interaction of $\bar qq$ pairs with nucleons in the nucleus leads to
shadowing at small $x$ and discuss this effect in detail. In the large $x$
region DIS takes place mainly on a single nucleon. There we focus on the
derivation of the convolution model. We point out that the off-shell properties
of the bound nucleon structure function give rise to sizable nuclear effects.


title:
Theoretical Interpretation of the NE18 Experiment on Nuclear
  Transparency in A(e,e'p) Scattering

abstract:
  The spectral function, measured in $A(e,e'p)$ reactions, is distorted by the
final-state interaction of the struck proton with the residual nucleus. This
causes a broadening of the observed transverse-momentum distribution which is
large even in the $d(e,e'p)$ reaction. We discuss the effects of this
$p_{\perp}$-broadening on the nuclear transparency measured in the recent NE18
experiment. Within conventional Glauber theory we can describe the
measurements. Transparency effects are thus small in agreement with our earlier
predictions.


title: Fragmentation model and quark/hadron system

abstract:
  Nuclear multifragmentation process can be viewed as a recombination of
nucleons into clusters of various sizes. In a combinatorial analysis, various
moments of cluster size distribution appear to be quite simple in terms of
canonical partition functions. This simple model can also describe a branching
phenomena and a clusterization phenomena. The possibility of applying this
fragmentation model in describing a hadronization of quark-gluon system and a
strangeness production is discussed.


title: Hydrodynamical assessment of 200 AGeV collisions

abstract:
  We are analyzing the hydrodynamics of 200 A GeV S+S collisions using a new
approach which tries to quantify the uncertainties arising from the specific
implementation of the hydrodynamical model. Based on a previous
phenomenological analysis we use the global hydrodynamics model to show that
the amount of initial flow, or initial energy density, cannot be determined
from the hadronic momentum spectra. We additionally find that almost always a
sizeable transverse flow deve- lops, which causes the system to freeze out,
thereby limiting the flow velocity in itself. This freeze-out dominance in turn
makes a distinction between a plasma and a hadron resonance gas equation of
state very difficult, whereas a pure pion gas can easily be ruled out from
present data. To complete the picture we also analyze particle multiplicity
data, which suggest that chemical equilibrium is not reached with respect to
the strange particles. However, the over- population of pions seems to be at
most moderate, with a pion chemical potential far away from the Bose
divergence.


title: On the Lorentz structure of the confinement potential

abstract:
  We investigate the Lorentz structure of the confinement potential through a
study of the meson spectrum using Salpeter's instantaneous approximation to the
Bethe-Salpeter equation. The equivalence between Salpeter's and a
random-phase-approximation (RPA) equation enables one to employ the same
techniques developed by Thouless, in his study of nuclear collective
excitations, to test the stability of the solutions. The stablity analysis
reveals the existence of imaginary eigenvalues for a confining potential that
transforms as a Lorentz scalar. Moreover, we argue that the instability
persists even for very large values of the constituent quark mass. In contrast,
we find no evidence of imaginary eigenvalues for a timelike vector potential
--- even for very small values of the constituent mass.


title: Microscopic multicluster description of the neutron-rich helium isotopes

abstract:
  The neutron halo structure of $^{6}$He and of $^{8}$He is studied in a
microscopic three-body and five-body model, respectively. Various cluster
arrangements are included to embody a variety of correlations between the
clusters. The intercluster wave function is determined with the stochastic
variational method. The $^{6}$He and $^{8}$He energies are reproduced with the
same effective force very well. The radii and densities are compared with the
results of empirical analyses. The calculated difference of the neutron and
proton radii exceeds 0.8 fm, confirming the thick neutron skin. The two-neutron
removal spectroscopic amplitudes are calculated and used for evaluating the
momentum distribution and the $\beta$ decay spectrum, which are sensitive to
the halo structure. A fair agreement with experiment is obtained.


title: Hadron widths in mixed-phase matter

abstract:
  We derive classically an expression for a hadron width in a two-phase region
of hadron gas and quark-gluon plasma (QGP). The presence of QGP gives hadrons
larger widths than they would have in a pure hadron gas. We find that the
$\phi$ width observed in a central Au+Au collision at $\sqrt{s}=200$
GeV/nucleon is a few MeV greater than the width in a pure hadron gas. The part
of observed hadron widths due to QGP is approximately proportional to
$(dN/dy)^{-1/3}$.


title: Capture of Solar and Higher-Energy Neutrinos by Iodine 127

abstract:
  We discuss and improve a recent treatment of the absorption of solar
neutrinos by ${}^{127}$I, in connection with a proposed solar neutrino
detector. With standard-solar-model fluxes and an in-medium value of -1.0 for
the axial-vector coupling constant $g_A$, we obtain a ${}^8$B-neutrino cross
section of 3.3$\times 10^{-42}$, about 50\% larger than in our previous work,
and a ${}^7$Be cross section that is less certain but nevertheless also larger
than before. We then apply the improved techniques to higher incoming energies
that obtain at the LAMPF beam dump, where an experiment is underway to finalize
a calibration of the ${}^{127}$I with electron neutrinos from muon decay. We
find that forbidden operators, which play no role in solar-neutrino absorption,
contribute nonnegligibly to the LAMPF cross section, and that the preliminary
LAMPF mean value is significantly larger than our prediction.


title:
Role of the Low-Lying Isoscalar Dipole Modes in the Polarization
  Potential

abstract:
  An analysis of the real and imaginary part of the polarization potential in
terms of the relative contributions of the single collective states for the $
^{208}Pb + ^{208}Pb $ system has been done. The polarization potential has been
calculated within the Feshbach formalism taking into account the collective
states calculated with the Wigner function moments method. The contribution of
the isoscalar giant dipole resonance states has been estimated being of the
order of 10 - 20 \% of the total at relatively low incident energy.


title: Fission fragment orientation and gamma ray emission anisotropy

abstract:
  Experimental data on angular distributions of gamma rays emitted from binary
and ternary spontaneous fission of $^{252}{\rm Cf}$ are analyzed. Their
difference indicates that the alignment of fragments is higher in ternary
fission than in binary one. The consequences of possible relation between the
mechanism of ternary fission and the excitation of collective modes during the
saddle-to-scission stage are discussed.


title: On the Momentum Dependence of the Nucleon - Nucleus Optical Potential

abstract:
  The momentum dependence of the mean-field contribution to the real part of
the optical model potential is investigated employing realistic nucleon-nucleon
interactions. Within a non-relativistic approach a momentum dependence
originates from the non-locality of the Fock exchange term. Deducing the real
part of the optical model from a relativistic Dirac Brueckner Hartree Fock
approximation for the self-energy of the nucleons yields an additional momentum
dependence originating from the non-relativistic reduction of the self-energy.
It is demonstrated that large Fock terms are required in the non-relativistic
approach to simulate these relativistic features. A comparison is made between
a local density approximation for the optical model and a direct evaluation in
finite nuclei.


title:
P,T-Violating Nuclear Matrix Elements in the One-Meson Exchange
  Approximation

abstract:
  Expressions for the P,T-violating NN potentials are derived for $\pi$, $\rho$
and $\omega$ exchange. The nuclear matrix elements for $\rho$ and $\omega$
exchange are shown to be greatly suppressed, so that, under the assumption of
comparable coupling constants, $\pi$ exchange would dominate by two orders of
magnitude. The ratio of P,T-violating to P-violating matrix elements is found
to remain approximately constant across the nuclear mass table, thus
establishing the proportionality between time-reversal-violation and
parity-violation matrix elements. The calculated values of this ratio suggest a
need to obtain an accuracy of order $ 5 \times 10^{-4}$ for the ratio of the
PT-violating to P-violating asymmetries in neutron transmission experiments in
order to improve on the present limits on the isovector pion coupling constant.


title: A Fully Isotopic Model of Fragmentation

abstract:
  A general model for the fragmentation of a two-component system (e.g. protons
and neutrons) is proposed and solved exactly. The extension of this model to
any number of components is also shown to be exactly solvable. A connection
between this models and the permutation group is discussed. The notion of
isotopic equivalence is defined in order to evaluate the equivalence of these
models to earlier one-component models. All the one-component models considered
in earlier papers are shown to be equivalent to a particular class of
two-component models. A simplified model applicable to the case of nuclear
fragmentation is introduced and analyzed. Modifications to this model to
include effects such as pairing and Coulomb interactions are discussed.


title: Anomalous Crossing Frequency in Odd Proton Nuclei

abstract:
  A generic explanation for the recently observed anomalous crossing
frequencies in odd proton rare earth nuclei is given. As an example, the proton
${1\over 2} [541]$ band in $^{175}$Ta is discussed in detail by using the
angular momentum projection theory. It is shown that the quadrupole pairing
interaction is decisive in delaying the crossing point and the changes in
crossing frequency along the isotope chain are due to the different neutron
shell fillings.


title: Quantum Size Effects in Classical Hadrodynamics

abstract:
  We discuss future directions in the development of classical hadrodynamics
for extended nucleons, corresponding to nucleons of finite size interacting
with massive meson fields. This new theory provides a natural covariant
microscopic approach to relativistic nucleus-nucleus collisions that includes
automatically spacetime nonlocality and retardation, nonequilibrium phenomena,
interactions among all nucleons, and particle production. The present version
of our theory includes only the neutral scalar ($\sigma$) and neutral vector
($\omega$) meson fields. In the future, additional isovector pseudoscalar
($\pi^+$,~$\pi^-$,~$\pi^0$), isovector vector ($\rho^+$,~$\rho^-$,~$\rho^0$),
and neutral pseudoscalar ($\eta$) meson fields should be incorporated. Quantum
size effects should be included in the equations of motion by use of the
spreading function of Moniz and Sharp, which generates an effective nucleon
mass density smeared out over a Compton wavelength. However, unlike the
situation in electrodynamics, the Compton wavelength of the nucleon is small
compared to its radius, so that effects due to the intrinsic size of the
nucleon dominate.


title: Stochastic Methods for Quantum Scattering

abstract:
  Quantum scattering at zero energy is studied with stochastic methods. A path
integral representation for the scattering cross section is developed. It is
demonstrated that Monte Carlo simulation can be used to compare effective
potentials which are frequently used in multiple scattering with the exact
result.


title: Hard Gammas from Low-Energy Heavy-Ion Collisions

abstract:
  Single-particle radiative mechanism of $\gamma$ emission embedded into the
pre-equilibrium exciton model is used to calculate the $\gamma$ emission from a
decay of $^{160}$Er$^{*}$ created in two different ways. The initial stage of a
reaction is described using momentum-space overlaps of colliding nuclei. We can
reproduce the main features of the observed $\gamma$ energy spectra including
the fact that the spectrum observed in more symmetric combination is slightly
harder than in the other case.


title:
Coulomb plus Nuclear Scattering in Momentum Space for Coupled
  Angular-Momentum States

abstract:
  The Vincent--Phatak procedure for solving the momentum-space Schrodinger
equation with combined Coulomb-plus-short-range potentials is extended to
angular momentum states coupled by an optical potential---as occurs in spin 1/2
times 1/2 scattering. A generalization of the Blatt--Biedenharn phase shift
parameterization is derived and applied to 500 MeV polarized-proton scattering
from He3 and C13. The requisite high-precision partial-wave expansions and
integrations are described.


title:
Comment on: "Transverse-Mass $M_\perp$ Dependence of Dilepton Emission
  from Preequilibrium and Quark-Gluon Plasma in High Energy Nucleus-Nucleus
  Collisions"

abstract:
  In a recent Letter, Geiger presents calculations of the dilepton emission
from the early stage of ultrarelativistic heavy ion collisions using the parton
cascade model (PCM). He shows that the $M_\perp$ scaling is not observed. In
this Comment, we point out that this is largely due to a defect in the PCM.


title:
Nucleon-Nucleon Correlations and Final State Interaction in Inclusive
  Quasi-Elastic Electron Scattering off Nuclei at x>1

abstract:
  Inclusive quasi-elastic electron scattering off nuclei is investigated at
high momentum transfer (Q^2>1 (GeV/c)^2) and x>1 adopting a consistent
treatment of nucleon-nucleon correlations in initial and final states. It is
shown that in case of light as well as complex nuclei the inclusive cross
section at 1.3<x<2 is dominated by the absorption of the virtual photon on a
pair of correlated nucleons and by their elastic rescattering in the continuum,
whereas at x>2 it is governed by the rescattering of the outgoing
off-mass-shell nucleon in the complex optical potential generated by the ground
state of the residual (A-1)-nucleon system.


title: BRST Treatment of the Bohr Collective Hamiltonian at High Spins

abstract:
  The BRST treatment of triaxial systems rotating at high spins is used to
solve perturbatively the $\gamma$-independent Bohr collective hamiltonian.


title: Nuclear Breathing Mode in the Relativistic Mean-Field Theory

abstract:
  The breathing-mode giant monopole resonance is studied within the framework
of the relativistic mean-field (RMF) theory. Using a broad range of parameter
sets, a systematic analysis of constrained incompressibility and excitation
energy of isoscalar monopole states in finite nuclei is performed. A comparison
is made with the incompressibility derived from the semi-infinite nuclear
matter and with constrained nonrelativistic Skyrme Hartree-Fock calculations.
Investigating the dependence of the breathing-mode energy on the nuclear matter
incompressibility, it is shown that dynamical properties of surface respond
differently in the RMF theory than in the Skyrme approach.


title: Polarizing Stored Beams by Interaction with Polarized Electrons

abstract:
  A polarized, internal electron target gradually polarizes a proton beam in a
storage ring. Here, we derive the spin-transfer cross section for $\vec
e\,(p,\vec p\, )e$\ scattering. A recent measurement of the polarizing effect
of a polarized atomic hydrogen target is explained when the effect of the
atomic electrons is included. We also consider the interaction of a stored beam
with a pure electron target which can be realized either by a comoving electron
beam or by trapping of electrons in a potential well. In the future, this could
provide a practical way to polarize antiprotons.


title: Do parton cascade model results approach chemical equilibrium?

abstract:
  This comment is withdrawn, as the figure on which it was based is
inconsistent with other figures in the text and thus probably incorrect. Using
the other figures, I find that the parton cascade model does approach chemical
equilibrium correctly.


title: Covariant Model for Dynamical Quark Confinement

abstract:
  Based on a recent manifestly covariant time-ordered approach to the
relativistic many-body problem, the quark propagator is defined by a nonlinear
Dyson--Schwinger-type integral equation, with a one-gluon loop. The resulting
energy-dependent quark mass is such that the propagator is singularity-free for
real energies, thus ensuring confinement. The self-energy integral converges
without regularization, due to the chiral limit of the quark mass itself.
Moreover, the integral determines the low-energy limit of the quark-gluon
coupling constant, for which a value of $g^2/4\pi =4.712$ is found.


title:
New calculations of the PNC Matrix Element for the $J^{\pi}T$
  0$^{+}1,0^{-}1$ doublet in $^{14}$N

abstract:
  A new calculation of the predominantly isoscalar PNC matrix element between
the $J^{\pi}T$ $0^{+}1,0^{-}1$ (E$_{x} \approx$ 8.7 MeV) states in $^{14}$N has
been carried out in a (0+1+2+3+4)$\hbar \omega$ model space with the
Warburton-Brown interaction. The magnitude of the PNC matrix element of 0.22 to
0.34 eV obtained with the DDH PNC interaction is substantially suppressed
compared with previous calculations in smaller model spaces but shows agreement
with the preliminary Seattle experimental data. The calculated sign is opposite
to that obtained experimentally, and the implications of this are discussed.


title: Scaling Law in Cluster Decay

abstract:
  A recently proposed scaling law for the decay time of alpha particles is
generalized for cluster decay. It is shown that for the decay of even-even
parents, $logT_{1/2}$ depends linearly on the scaling variable
S=(Z$_{c}$Z$_{d})^{0.6}/\sqrt{Q_{c}}$ and on the square root of the reduced
mass of cluster and daughter.


title: Nonperturbative aspects of the quark-photon vertex

abstract:
  The electromagnetic interaction with quarks is investigated through a
relativistic, electromagnetic gauge-invariant treatment. Gluon dressing of the
quark-photon vertex and the quark self-energy functions is described by the
inhomogeneous Bethe-Salpeter equation in the ladder approximation and the
Schwinger-Dyson equation in the rainbow approximation respectively. Results for
the calculation of the quark-photon vertex are presented in both the time-like
and space-like regions of photon momentum squared, however emphasis is placed
on the space-like region relevant to electron scattering. The treatment
presented here simultaneously addresses the role of dynamically generated
$q\bar{q}$ vector bound states and the approach to asymptotic behavior. The
resulting description is therefore applicable over the entire range of momentum
transfers available in electron scattering experiments. Input parameters are
limited to the model gluon two-point function, which is chosen to reflect
confinement and asymptotic freedom, and are largely constrained by the obtained
bound-state spectrum.


title: Quark-Gluon-Plasma Formation at SPS Energies?

abstract:
  By colliding ultrarelativistic ions, one achieves presently energy densities
close to the critical value, concerning the formation of a quark-gluon-plasma.
This indicates the importance of fluctuations and the necessity to go beyond
the investigation of average events. Therefore, we introduce a percolation
approach to model the final stage ($\tau > 1$ fm/c) of ion-ion collisions, the
initial stage being treated by well-established methods, based on strings and
Pomerons. The percolation approach amounts to finding high density domains, and
treating them as quark-matter droplets. In this way, we have a {\bf realistic,
microscopic, and Monte--Carlo based model which allows for the formation of
quark matter.} We find that even at SPS energies large quark-matter droplets
are formed -- at a low rate though. In other words: large quark-matter droplets
are formed due to geometrical fluctuation, but not in the average event.


title: Antiproton-proton partial-wave analysis below 925 MeV/c

abstract:
  A partial-wave analysis of all antiproton-proton scattering data below 925
MeV/c antiproton laboratory momentum is presented. The method used is adapted
from the Nijmegen phase-shift analyses of pp and np scattering data. The
Nijmegen 1993 antiproton-proton database, consisting of 3646 antiproton-proton
scattering data, is presented and discussed. The best fit to this database
results in chi^2_min/Ndata = 1.043. The pseudovector coupling constant of the
charged pion to nucleons is determined to be (f_c)^2 = 0.0732(11) at the pion
pole, where the error is statistical.


title: The Balian-Br\'ezin Method in Relativistic Quantum Mechanics

abstract:
  The method suggested by Balian and Br\'ezin for treating angular momentum
reduction in the Faddeev equations is shown to be applicable to the
relativistic three-body problem.


title:
Threshold Two-Pion Photo- and Electroproduction: More neutrals than
  expected

abstract:
  We present an exploratory study of two pion photo-- and electroproduction off
the nucleon in the threshold region. To calculate the pertinent amplitudes, we
make use of heavy baryon chiral perturbation theory. We show that due to finite
chiral loops the production cross section for final states with two neutral
pions is considerably enhanced. The experimental implications are briefly
discussed.


title: Mesons and the Structure of Nucleons

abstract:
  The role of mesons, particularly the pion, in the structure of nucleons is
reviewed and investigated. Since quark-antiquark pairs are likely to
``transform" into mesons at large distances, mesons are expected to contribute
to nucleon structure. Their effects on the Gottfried sum rule, on the
strangeness content of the nucleon, and on the spin of the nucleon are
discussed.


title: A quark-meson model for nuclear and neutron matter

abstract:
  An explicit quark model, based on a mean field description of non-overlapping
nucleon bags bound by the self-consistent exchange of $\sigma$, $\omega$ and
$\rho$ mesons, is used to investigate the properties of both nuclear and
neutron matter. We establish a clear understanding of the relationship between
this model, which incorporates the internal structure of the nucleon, and QHD.
Finally, we use the model to study the density dependence of the quark
condensate in-medium.


title: Shell model on a random gaussian basis

abstract:
  Pauli-projected random gaussians are used as a representation to solve the
shell model equations. The elements of the representation are chosen by a
variational procedure. This scheme is particularly suited to describe cluster
formation and cluster decay in nuclei. It overcomes the basis-size problem of
the ordinary shell model and the technical difficulties of the
cluster-configuration shell model. The model reproduces the $\alpha$-decay
width of $^{212}$Po satisfactorily.


title: Ground-state Correlation Effects in Extended RPA Calculations

abstract:
  We study normalization problems associated with use of perturbatively
correlated ground-states in extended RPA schemes in the context of a specific
but typical example. The sensitivity of the results to the amount of $2p2h$
admixtures to the correlated ground state is also investigated in terms of a
modification of the standard perturbative approach.


title: Double beta decay transition mechanism

abstract:
  After briefly reviewing $\beta \beta$ decay as a test of the neutrino mass, I
examine the nuclear structure involved in this process. Simple formulas (\`{a}
la Pad\'{e}) are designed for the transition amplitudes and the general
behavior of $\beta \beta$ decay amplitudes in the quasiparticle random phase
approximation are discussed. Results of a calculation for $^{48}Ca$, $^{76}Ge
$, $^{82}Se$, $^{100}Mo$, $^{128}Te$ and $^{130}Te$ nuclei are presented, in
which the particle-particle interaction strengths have been fixed by invoking
the partial restoration of the isospin and Wigner SU(4) symmetries. An upper
limit of $ <m_{\nu}>\approx 1$ eV is obtained for the effective neutrino mass.


title: Off-Shell NN Potential and Triton Binding Energy

abstract:
  The NONLOCAL Bonn-B potential predicts 8.0 MeV binding energy for the triton
(in a charge-dependent 34-channel Faddeev calculation) which is about 0.4 MeV
more than the predictions by LOCAL NN potentials. We pin down origin and size
of the nonlocality in the Bonn potential, in analytic and numeric form. The
nonlocality is due to the use of the correct off-shell Feynman amplitude of
one-boson-exchange avoiding the commonly used on-shell approximations which
yield the local potentials. We also illustrate how this off-shell behavior
leads to more binding energy. We emphasize that the increased binding energy is
not due to on-shell differences (differences in the fit of the NN data or phase
shifts). In particular, the Bonn-B potential reproduces accurately the
$\epsilon_1$ mixing parameter up to 350 MeV as determined in the recent
Nijmegen multi-energy NN phase-shift analysis. Adding the relativistic effect
from the relativistic nucleon propagators in the Faddeev equations, brings the
Bonn-B result up to 8.2 MeV triton binding. This leaves a difference of only
0.3 MeV to experiment, which may possibly be explained by refinements in the
treatment of relativity and the inclusion of other nonlocalities (e.~g.,
quark-gluon exchange at short range). Thus, it is conceivable that a realistic
NN potential which describes the NN data up to 300 MeV correctly may explain
the triton binding energy without recourse to 3-N forces; relativity would play
a major role for this result.


title: Nijmegen Soft-Core Potential Including Two-Meson Exchange

abstract:
  We report on the progress of the construction of the extended soft-core (ESC)
Nijmegen potential. Next to the standard one-boson-exchange parts, the model
includes the pion-meson-exchange potentials due to the parallel and crossed-box
diagrams, as well as the one-pair and two-pair diagrams, vertices for which can
be identified with similar interactions appearing in chiral-symmetric
Lagrangians. Although the ESC potential is still under construction, it already
gives an excellent description of all $N\!N$ scattering data below 350 MeV with
$\chi^{2}/{\rm datum}=1.3$.


title: Pairing correlation in nuclear matter from Skyrme force

abstract:
  The properties of pairing correlation in nuclear matter are investigated by
using various versions of Skyrme forces. Truncation of states involving pairing
correlation, necessary due to zero range nature of the Skyrme force, is
discussed in detail. A plateau appears in pairing gap versus cutoff for each
force. We propose to choose the cutoff parameter in the middle of the plateau
so that the parameterization is independent of nuclides.


title:
Theory of parity violation in compound nuclear states; one particle
  aspects

abstract:
  In this work we formulate the reaction theory of parity violation in compound
nuclear states using Feshbach's projection operator formalism. We derive in
this framework a complete set of terms that contribute to the longitudinal
asymmetry measured in experiments with polarized epithermal neutrons. We also
discuss the parity violating spreading width resulting from this formalism. We
then use the above formalism to derive expressions which hold in the case when
the doorway state approximation is introduced. In applying the theory we limit
ourselves in this work to the case when the parity violating potential and the
strong interaction are one-body. In this approximation, using as the doorway
the giant spin-dipole resonance and employing well known optical potentials and
a time-reversal even, parity odd one-body interaction we calculate or estimate
the terms we derived. In our calculations we explicitly orthogonalize the
continuum and bound wave functions. We find the effects of orthogonalization to
be very important. Our conclusion is that the present one-body theory cannot
explain the average longitudinal asymmetry found in the recent polarized
neutron experiments. We also confirm the discrepancy, first pointed out by
Auerbach and Bowman, that emerges, between the calculated average asymmetry and
the parity violating spreading width, when distant doorways are used in the
theory.


title: A Revisit of SO(6) Dynamical Symmetry in Nuclear Structure

abstract:
  According to the analysis based on the fermion dynamical symmetry model,
nuclei previously regarded as SO(6)-like (e.g. $^{128}$Xe and $^{196}$Pt) are
shown to be more akin to the transitional nuclei between SO(7) and SO(6)
symmetries.


title:
On the $M_T$ scaling of dilepton spectra in high energy heavy ion
  collisions

abstract:
  The so-called $M_T$ scaling for dilepton spectra at RHIC energies is
examined. It is seen that a proper accounting of the complete set of dilepton
producing processes forces us to abandon the proposed scaling around $M_T$ =
2.6 GeV, which has been put forward as a possible signature of the presence of
quark-matter. Any substantial transverse expansion in the QGP phase itself will
also offset this scaling behaviour. The rates of lepton pair production are
time--integrated in Bjorken hydrodynamics and the different sources are
compared against each other.


title:
Full determination of transition matrix elements in the $\vec{d}
  (\vec{p},pp)n$ reaction

abstract:
  It is shown that in the $d(p,pp)n$ reaction with a colinear geometry and the
two outgoing protons in a singlet state, the only two independent T-matrix
elements can be determined from spin correlation experiments. These matrix
elements are strongly dependent on the deuteron helicity amplitudes, which are
expected to vanish for $1.4fm^{-1}<p<1.7fm^{-1}$.\vspace{10 mm}\\


title: On the mean free paths of pions and kaons in hot hadronic matter

abstract:
  Pion and kaon mean free paths within a thermal hadronic background are
calculated using relativistic kinetic theory. Free cross sections are used
which include contributions from $\rho$, $K^{*}$, $\Delta$ and heavier
resonances. Given pion to baryon ratios appropriate for the breakup stage of a
$200\cdot A$GeV relativistic-heavy-ion collision, we find for temperatures less
than 100 MeV, kaons have a shorter mean free path than pions, while for higher
breakup temperatures the reverse is true. Since breakup temperatures should be
in the neighborhood of 100 MeV, this suggests that kaon interferometry samples
the same emission distribution as pion interferometry.


title: Response Function of Hot Nuclear Matter

abstract:
  We investigate the response function of hot nuclear matter to a small
isovector external field using a simplified Skyrme interaction reproducing the
value of the symmetry energy coefficient.
  We consider values of the momentum transfer corresponding to the dipole
oscillation in heavy nuclei. We find that while at zero temperature the
particle hole interaction is almost repulsive enough to have a sharp (zero
sound type) collective oscillation, such is no longer the case at temperatures
of a few MeV. As a result a broadening of the dipole resonance occurs, leading
to its quasi disappearence by the time the temperature reaches 5 MeV. The
sensivity of the temperature evolution of the width when modifying the residual
interaction strength is also examined.


title: Spin Force Dependence Of Nucleon Structure Functions

abstract:
  Deep inelastic structure functions for the nucleon are obtained in a
constituent quark model on the light cone. In the Bjorken limit the parton
model is derived. Structure functions from the hadronic tensor at the scale
$\mu \sim 0.25$ GeV are evolved from (0.6 GeV$)^{2}$ to $-q^{2}\sim 15$
GeV$^{2}$. The model incorporates the quark boosts, is designed to describe
form factors and structure functions, and to provide a link between the parton
and constituent quark models. The main effect of the spin force between quarks
is described in terms of smaller (and lighter) scalar $u-d$ quark pairs in the
nucleon. To account for the negative slope of $F^{n}_{2}(x)/F^{p}_{2}(x)$,
attraction between scalar $u-d$ quark pairs and incorporation of boosts are
required. The two-body spin force between quarks from color magnetism also
leads to a negative slope. The polarization asymmetry $A^{p}_{1}$ is in fair
agreement with the EMC data in the valence quark region. Revised
hep-ph/9401342, Phys. Rev. D.


title: Direct Capture at Low Energies

abstract:
  The importance of direct capture for (n,$\gamma$)--reactions on
intermediate-- and heavy--mass target nuclei occuring in the s-- and r--process
is investigated. It is shown that the direct mechanism is non--negligible for
magic and neutron rich target nuclei. For some double magic and neutron rich
nuclei in the r--process direct capture is even the dominant reaction
mechanism.


title:
SDG fermion-pair algebraic SO(12) and Sp(10) models and their boson
  realizations

abstract:
  It is shown how the boson mapping formalism may be applied as a useful
many-body tool to solve a fermion problem. This is done in the context of
generalized Ginocchio models for which we introduce S-, D-, and G-pairs of
fermions and subsequently construct the sdg-boson realizations of the
generalized Dyson type. The constructed SO(12) and Sp(10) fermion models are
solved beyond the explicit symmetry limits. Phase transitions to rotational
structures are obtained, also in situations where there is no underlying SU(3)
symmetry.


title: A Large Solid Angle Study of Pion Absorption on He3

abstract:
  Measurements have been made of pi+ absorption on He3 at T_pi+ = 118, 162, and
239 MeV using the Large Acceptance Detector System (LADS). The nearly 4pi solid
angle coverage of this detector minimizes uncertainties associated with
extrapolations over unmeasured regions of phase space. The total absorption
cross section is reported. In addition, the total cross section is divided into
components in which only two or all three nucleons play a significant role in
the process. These are the first direct measurements of the total and three
nucleon absorption cross sections.


title: The $\eta$NN Coupling in Eta Photoproduction

abstract:
  Low-energy eta photoproduction on the nucleon is studied in an effective
Lagrangian approach that contains Born terms, vector meson and nucleon
resonance contributions. The resonance sector includes the $S_{11}(1535)$,
$P_{11}(1440)$ and $D_{13}(1520)$ states whose couplings are fixed by
independent electromagnetic and hadronic data. The available $(\gamma,\eta)$
data are employed to discuss the difference between pseudoscalar and
pseudovector Born terms and to determine the magnitude of the $\eta NN$
coupling constant. We present multipoles that are most sensitive to the various
model ingredients and demonstrate how these multipoles may be accessed in
polarization observables. Cross section calculations are presented for eta
photoproduction on light nuclei.


title:
Critical Enhancement of the In-medium Nucleon-Nucleon Cross Section at
  low Temperatures

abstract:
  The in-medium nucleon-nucleon cross section is calculated starting from the
thermodynamic T-matrix at finite temperatures. The corresponding
Bethe-Salpeter-equation is solved using a separable representation of the Paris
nucleon-nucleon-potential. The energy-dependent in-medium N-N cross section at
a given density shows a strong temperature dependence. Especially at low
temperatures and low total momenta, the in-medium cross section is strongly
modified by in-medium effects. In particular, with decreasing temperature an
enhancement near the Fermi energy is observed. This enhancement can be
discussed as a precursor of the superfluid phase transition in nuclear matter.


title:
Nuclear Matrix Elements of Axial-Charge Exchange Currents Derived in
  Heavy-Fermion Chiral Perturbation Theory

abstract:
  We calculate shell-model matrix elements of the axial-charge exchange current
operators that have been obtained up to the next-to-leading order from
heavy-fermion chiral perturbation theory. It is found that loop corrections to
the soft one-pion-exchange contribution are small (around 10 \%) and have no
significant dependence on the nuclear mass number or on the valence-nucleon
orbits. These results render further support to the chiral-filtering
conjecture.


title: From Regular to Chaotic States in Atomic Nuclei

abstract:
  An interesting aspect of nuclear dynamics is the co--existence, in atomic
nuclei, of regular and chaotic states. In the first part of the present work,
we review the state of the art of nuclear dynamics and use a schematic shell
model to show how a very simple and schematic nucleon--nucleon interaction can
produce an order$\to$chaos transition. The second part is devoted to a
discussion of the wave function behaviour and decay of chaotic states using
some simple models (to be published in Rivista Nuovo Cimento).


title: pi-NN Coupling Constants from NN Elastic Data between 210 and 800 Mev

abstract:
  High partial waves for $pp$ and $np$ elastic scattering are examined
critically from 210 to 800 MeV. Non-OPE contributions are compared with
predictions from theory. There are some discrepancies, but sufficient agreement
that values of the $\pi NN$ coupling constants $g_0^2$ for $\pi ^0$ exchange
and $g^2_{c}$ for charged $\pi $ exchange can be derived. Results are $g^2_0 =
13.91 \pm 0.13 \pm 0.07$ and $g^2_c
  = 13.69 \pm 0.15 \pm 0.24$, where the first error is statistical and the
second is an estimate of the likely systematic error, arising mostly from
uncertainties in the normalisation of total cross sections and
$d\sigma/d\Omega$.


title: Varied Signature Splitting Phenomena in Odd Proton Nuclei

abstract:
  Varied signature splitting phenomena in odd proton rare earth nuclei are
investigated. Signature splitting as functions of $K$ and $j$ in the angular
momentum projection theory is explicitly shown and compared with those of the
particle rotor model. The observed deviations from these rules are due to the
band mixings. The recently measured $^{169}$Ta high spin data are taken as a
typical example where fruitful information about signature effects can be
extracted. Six bands, two of which have not yet been observed, were calculated
and discussed in detail in this paper. The experimentally unknown band head
energies are given.


title: Microscopic mass formulae

abstract:
  By assuming the existence of a pseudopotential smooth enough to do
Hartree-Fock variations and good enough to describe nuclear structure, we
construct mass formulae that rely on general scaling arguments and on a
schematic reading of shell model calculations. Fits to 1751 known binding
energies for N,Z$\geq 8$ lead to RMS errors of 614 keV with 14 parameters and
388 keV with 28 parameters. The latter is easily reduced to a 20 parameter form
at 423 keV.


title:
Vibrations versus collisions and the iterative structure of two-body
  dynamics

abstract:
  We adopt a truncated version of two-body dynamics by neglecting three-body
correlations, as is supported by microscopic numerical calculations.
Introducing orthogonal channel correlations for the pp- and the ph-channel and
integrating the latter in terms of vibrational RPA-states we derive a retarded
two-body equation. Its solution is nonperturbative with respect to loops,
ladders and mixed contributions. In the stationary limit we obtain an equation
for a generalised effective interaction which iterates both the G-matrix and
the polarisation matrix. An in-medium scattering approach transparently
demonstrates the collisional damping of the vibrations.


title: Systematics of $\alpha$--nucleus optical potentials

abstract:
  Double--folded optical $\alpha$--nucleus potentials can be used to calculate
elastic scattering cross sections in a wide mass-- and energy region. Because
of the systematic behavior of the potential parameters we are able to obtain
reliable optical potentials for astrophysically relevant reactions even without
scattering data in low--energy region. As example we analyze the capture
reaction ${^{144}{\rm Sm}}(\alpha,\gamma){^{148}{\Gd}}$.


title: Direct mechanism in solar nuclear reactions

abstract:
  A short overview of the direct reaction mechanism and the models used for the
analysis of such processes is given. Nuclear reactions proceeding through the
direct mechanism and involved in solar hydrogen burning are discussed. The
significance of these nuclear reactions with respect to the solar neutrino
problem is investigated.


title: Two-Loop Calculations with Vertex Corrections in the Walecka Model

abstract:
  Two-loop corrections with scalar and vector form factors are calculated for
nuclear matter in the Walecka model. The on-shell form factors are derived from
vertex corrections within the framework of the model and are highly damped at
large spacelike momenta. The two-loop corrections are evaluated first by using
the one-loop parameters and mean fields and then by refitting the total
energy/baryon to empirical nuclear matter saturation properties. The modified
two-loop corrections are significantly smaller than those computed with bare
vertices. Contributions from the anomalous isoscalar form factor of the nucleon
are included for the first time. The effects of the implicit density dependence
of the form factors, which arise from the shift in the baryon mass, are also
considered. Finally, necessary extensions of these calculations are discussed.


title: Two-body Pion Absorption on $^3He$ at Threshold

abstract:
  It is shown that a satisfactory explanation of the ratio of the rates of the
reactions $^3He(\pi^-,nn)$ and $^3He(\pi^-,np)$ for stopped pions is obtained
once the effect of the short range two-nucleon components of the axial charge
operator for the nuclear system is taken into account. By employing realistic
models for the nucleon-nucleon interaction in the construction of these
components of the axial charge operator, the predicted ratios agree with the
empirical value to within 10-20\%.


title: Classical Lagrangian Model of the Pauli Principle

abstract:
  A classical Lagrangian model of the Pauli potential is introduced. It is
shown that the kinematic kinetic energy ($\sum \frac{1}{2} m v^2$) in the model
approximately reproduces the energy of a free Fermi gas at low temperatures and
at densities relevant in nuclear collisions with moderate beam energies.
Differences between canonical and kinematic quantities are pointed out. The
Pauli potential can be used in transport simulations.


title: N-Body Theory Revisited and its Extension to the pinnn-NNN Problem^*

abstract:
  In order to approach the pion--multinucleon problem, we have found it
convenient to reformulate the general N--body theory starting from the fully
unclusterized (i.e., N <- N) amplitude. If we rewrite such an amplitude in
terms of new unknowns which can be later identified as the amplitudes for all
the (N-1) <- (N-1) cluster processes, and repeat recursively the procedure up
to the treatment of the 2 <- 2 cluster processes, we obtain very naturally the
hierarchy of equations which ranges from the N--body fully--disconnected
Lippmann--Schwinger equation to the N--body connected--kernel
Yakubovskii--Grassberger--Sandhas one. This revisitation turns out to be very
useful when considering the modifications required in case one of the bodies is
a pion and the remaining are nucleons, with the pion being allowed to disappear
and reappear through the action of a pion--nucleon vertex. In fact, we obtain a
new set of coupled pion-- multinucleon equations which allow a consistent and
simultaneous treatment of pion scattering and absorption. For the piNNN system,
the kernel of these coupled equations is shown to be connected after three
iterations.


title: Bose-Enhancement and Pauli-Blocking Effects in Transport Models

abstract:
  The ability of semi-classical transport models to correctly simulate Pauli
blocking and Bose enhancement is discussed. In the context of simple quantum
mechanical systems, it is shown that using $(1 \pm f)$ enhancements is
inadequate to describe systems far from equilibrium. The relaxation of $(1 +
f)$ descriptions toward equilibrium is studied both in the context of simple
models, including a hot pion gas confined to a box. We give simple estimates
for the characteristic number of collisions for a system to relax toward
equilibrium.


title:
Effects of N$^{*}$(1440) resonance on subthreshold kaon, antikaon and
  antiproton production

abstract:
  We study the effects of $N^{*}(1440)$ resonance on the production of kaons,
antikaons and antiprotons in heavy-ion collisions at subthreshold energies.
Using free-space widths for the $\Delta(1232)$ and the $N^{*}(1440)$ resonance
and free-space thresholds for particle production, it is found that the
$N^{*}$-baryon interactions contribute about 10\%, 25\% and 80\% to the yield
of kaon, antikaon and antiproton, respectively. Doubling the widths of
resonances due to possible medium effects, both the total and the $N^{*}$
induced antiproton yield decrease by about a factor of 3. Using a reduced
antiproton production threshold in a nuclear medium as a result of dropping
in-medium nucleon and antiproton masses, the total and the $N^{*}$ induced
antiproton yield increase by a factor of 35 and 27, respectively, and the
contribution of the $N^{*}$ induced collisions is reduced to about 50\% of the
total.


title: Freeze-out Configuration in Multifragmentation

abstract:
  The excitation energy and the nuclear density at the time of breakup are
extracted for the $\alpha + ^{197}Au$ reaction at beam energies of 1 and 3.6
GeV/nucleon. These quantities are calculated from the average relative velocity
of intermediate mass fragments (IMF) at large correlation angles as a function
of the multiplicity of IMFs using a statistical model coupled with many-body
Coulomb trajectory calculations. The Coulomb component $\vec{v}_{c}$ and
thermal component $\vec{v}_{0}$ are found to depend oppositely on the
excitation energy, IMFs multiplicity, and freeze-out density. These
dependencies allow the determination of both the volume and the mean excitation
energy at the time of breakup. It is found that the volume remained constant as
the beam energy was increased, with a breakup density of about $\rho_{0}/7$,
but that the excitation energy increased $25\%$ to about 5.5 MeV/nucleon.


title: Near-threshold $K^{+}$ Production in Heavy-ion Collisions

abstract:
  Within a hadronic transport model we study in detail contributions to kaon
yields and momentum spectra from various baryon (resonance)-baryon (resonance)
and $\pi N$ interactions in heavy-ion collisions at beam energies near the
free-space kaon production threshold. It is found that the finite lifetime of
baryon resonances affects significantly the shape of kaon spectra, and the high
energy parts of the kaon spectra are dominated by kaons from $\pi N\rightarrow
\Lambda K^{+}$ processes. $N^{*}(1440)$ resonances are found to contribute
about 10\% to the kaon yield. Effects of boosting the Fermi momentum
distributions of the two colliding nuclei into their center of mass frame,
centrality of the reaction as well as the nuclear equation of state on kaon
yields and spectra are also discussed. Model calculations on $K^{+}$, $\pi^{+}$
and $\pi^{-}$ spectra for the reaction of Au+Au at $E_{beam}/A= 1.0$ GeV are
compared with the experimental data from the KaoS collaboration.


title: Charm Production at RHIC to O(\ALPHA_S^3)

abstract:
  We present results on rapidity and transverse momentum distributions of
inclusive charm quark production in heavy-ion collisions at RHIC, including the
next-to-leading order, $O(\alpha_s^3)$, radiative corrections and the nuclear
shadowing effect. We find the effective, nuclear K-factor to be $K(y)\approx
1.4$ for $\mid y\mid \leq 3$ in the rapidity distribution, while $1\leq
K(p_{T}) \leq 3$ for $1GeV\leq p_T \leq 6GeV$ in the $p_T$ distribution. We
incorporate multiple parton scatterings in our calculation of the fraction of
all central events that contain at least one charm quark pair. We obtain the
effective $A$-dependence of the charm cross sections. Finally, we comment on
the possibility of detecting the quark-gluon plasma signal as an enhanced charm
production in heavy-ion collisions at RHIC.


title: Testing QCD Sum Rule Techniques on the Lattice

abstract:
  Results for the first test of the ``crude'' QCD continuum model, commonly
used in QCD Sum Rule analyses, are presented for baryon correlation functions.
The QCD continuum model is found to effectively account for excited state
contributions to the short-time regime of two-point correlation functions and
allows the isolation of ground state properties. Confusion in the literature
surrounding the physics represented in point-to-point correlation functions is
also addressed. These results justify the use of the ``crude'' QCD continuum
model and lend credence to the results of rigorous QCD Sum Rule analyses.


title:
Probing Short Range Nucleon Correlations in High Energy Hard
  Quasielastic pd Reactions

abstract:
  We show that the strong dependence of the amplitude for $NN$ hard scattering
on the collision energy can be used to magnify the effects of short range
nucleon correlations in quasielastic $pd$ scattering. Under specific
kinematical conditions the effect of initial and final state interactions can
be accounted for by rescaling the cross section calculated within the plane
wave impulse approximation. The feasibility to investigate the role of
relativistic effects in the deuteron wave function is demonstrated by comparing
the predictions of different formalisms. Binding effects due to short range
correlations in deuteron are discussed as well.


title: Escape and Spreading Properties of Charge-Exchange Resonances in Bi 208

abstract:
  The properties of charge-exchange excitations of ${}^ {208}$Pb with $\Delta L
= 0$, i.e., the isobaric analog and Gamow-Teller resonances, are studied within
a self-consistent model making use of an effective force of the Skyrme type.
The well-known isobaric analog case is used to assess the reliability of the
model. The calculated properties of the Gamow-Teller resonance are compared
with recent experimental measurements with the aim of better understanding the
microscopic structure of this mode.


title: Thermal properties of Fe-54

abstract:
  We study the thermal properties of Fe-54 with the Brown-Richter interaction
in the complete 1p0f model space. Monte Carlo calculations show a peak in the
heat capacity and rapid increases in both the moment of inertia and M1 strength
near a temperature of 1.1 MeV that are associated with the vanishing of
proton-proton and neutron-neutron monopole pair correlations; neutron-proton
correlations persist to higher temperatures. Our results are consistent with a
Fermi gas level density whose back-shift vanishes with increasing temperature.


title:
Momentum--dependent nuclear mean fields and collective flow in heavy ion
  collisions

abstract:
  We use the Boltzmann-Uehling-Uhlenbeck model to simulate the dynamical
evolution of heavy ion collisions and to compare the effects of two
parametrizations of the momentum--dependent nuclear mean field that have
identical properties in cold nuclear matter. We compare with recent data on
nuclear flow, as characterized by transverse momentum distributions and flow
($F$) variables for symmetric and asymmetric systems. We find that the precise
functional dependence of the nuclear mean field on the particle momentum is
important. With our approach, we also confirm that the difference between
symmetric and asymmetric systems can be used to pin down the density and
momentum dependence of the nuclear self consistent one--body potential,
independently. All the data can be reproduced very well with a
momentum--dependent interaction with compressibility K = 210 MeV.


title: Neutrino Capture Cross Sections for Ar-40 and beta-decay of Ti-40

abstract:
  Shell-model calculations of solar neutrino absorption cross sections for
$^{40}$Ar, the proposed component of the ICARUS detector, are presented. It is
found that low-lying Gamow-Teller transitions lead to a significant enhancement
of the absorption rate over that expected from the Fermi transition between the
isobaric analog states, leading to an overall absorption rate of 6.7 SNU. We
also note that the pertinent Gamow-Teller transitions in $^{\sss 40}$Ar are
experimentally accessible from the $\beta$-decay of the mirror nucleus $^{\sss
40}$Ti. Predictions for the branching ratios to states in $^{\sss 40}$Sc are
presented, and the theoretical halflife of 53~ms is found to be in good
agreement with the experimental value of $56^{+18}_{-12}$~ms.


title: The One-Boson-Exchange Potential Model Approach

abstract:
  A review is given of the present situation in YN scattering. Special
attention is given to the handling of SU(3) in the various meson exchanges. The
importance of the almost always ignored contribution of the Pomeron is
reiterated.


title:
The Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear
  matter

abstract:
  The quark-meson coupling model which we have developed previously is extended
to incorporate the $\delta$ meson. It is then used to study the Nolen-Schiffer
anomaly and isospin symmetry breaking in nuclear matter. We find that, in
combination with the {\it u-d\/} mass difference, the difference between quark
scalar densities in protons and neutrons generates an effective neutron-proton
mass difference of the right magnitude. Finally we find that isospin symmetry
breaking in the quark condensates can be directly related to the $\delta$ meson
field.


title: Comment on "No-core calculations" of the spectra of light nuclei

abstract:
  We comment upon a recent work by Zheng, Barrett, Jaqua, Vary and McCarthy,
concerning calculations of spectra of light nuclei with no core. It is
demonstrated that the omission of particle-particle ladder diagrams in their
calculations, explains the large differences between results obtained with
various model spaces.


title:
Generator Coordinate Calculations for the Breathing-Mode Giant Monopole
  Resonance in Relativistic Mean Field Theory

abstract:
  The breathing-mode giant monopole resonance (GMR) is studied within the
framework of the relativistic mean-field theory using the Generator Coordinate
Method (GCM). The constrained incompressibility and the excitation energy of
isoscalar giant monopole states are obtained for finite nuclei with various
sets of Lagrangian parameters. A comparison is made with the results of
nonrelativistic constrained Skyrme Hartree-Fock calculations and with those
from Skyrme RPA calculations. In the RMF theory the GCM calculations give a
transition density for the breathing mode, which resembles much that obtained
from the Skyrme HF+RPA approach and also that from the scaling mode of the GMR.
From the systematic study of the breathing-mode as a function of the
incompressibility in GCM, it is shown that the GCM succeeds in describing the
GMR energies in nuclei and that the empirical breathing-mode energies of heavy
nuclei can be reproduced by forces with an incompressibility close to $K = 300$
MeV in the RMF theory.


title: Many-Body Currents and the Strange-Quark Content of 4he

abstract:
  Meson-exchange current (MEC) contributions to the parity-violating (PV)
asymmetry for elastic scattering of polarized electrons from $^4$He are
calculated over a range of momentum transfer using Monte Carlo methods and a
variational $^4$He ground state wavefunction. The results indicate that MEC's
generate a negligible contribution to the asymmetry at low-$|\qv|$, where a
determination of the nucleon's mean square strangeness radius could be carried
out at CEBAF. At larger values of momentum transfer -- beyond the first
diffraction minimum -- two-body corrections from the $\rho$-$\pi$ \lq\lq
strangeness charge" operator enter the asymmetry at a potentially observable
level, even in the limit of vanishing strange-quark matrix elements of the
nucleon. For purposes of constraining the nucleon's strangeness electric form
factor, theoretical uncertainties associated with these MEC contributions do
not appear to impose serious limitations.