title:
Modification of The Transition Rate in The Hydrogen Atom placed in
  Finite Space

abstract:
  When a hydrogen atom trapped in finite space formed by two parallel perfectly
conducting plates, the transition rates can be modified. Life-time of the
hydrogen $2P_{1/2}$-state is estimated to be shorter as much as $56.3ps $ with
a separation distance of $b = 1.2 \mu m$ between two plates. Although the
modification is dependent on position of the atom, the life-time can be shorten
or lengthen by adjusting the separation distance even for the case that the
atom is placed at the center between two plates.


title:
How to include a three-nucleon force into Faddeev equations for the 3N
  continuum: a new form

abstract:
  A new, more efficient approach to include a three nucleon force into
three-nucleon continuum calculations is presented. Results obtained in the new
and our old approach are compared both for elastic nucleon-deuteron scattering
as well as for the breakup process. The advantages of the new scheme are
discussed.


title: Double beta decay and the proton-neutron residual interaction

abstract:
  The validity of the pn-QRPA and -RQRPA descriptions of double beta decay
transition amplitudes is analyzed by using an exactly solvable model. It is
shown that the collapse of the QRPA is physically meaningful and that it is
associated with the appearance of a state with zero energy in the spectrum. It
is shown that in the RQRPA this particular feature is not present and that this
approach leads to finite but otherwise spurious results for the double beta
decay transition amplitudes near the point of collapse.


title: Possible solution of the Coriolis attenuation problem

abstract:
  The most consistently useful simple model for the study of odd deformed
nuclei, the particle-rotor model (strong coupling limit of the core-particle
coupling model) has nevertheless been beset by a long-standing problem: It is
necessary in many cases to introduce an ad hoc parameter that reduces the size
of the Coriolis interaction coupling the collective and single-particle
motions. Of the numerous suggestions put forward for the origin of this
supplementary interaction, none of those actually tested by calculations has
been accepted as the solution of the problem. In this paper we seek a solution
of the difficulty within the framework of a general formalism that starts from
the spherical shell model and is capable of treating an arbitrary linear
combination of multipole and pairing forces. With the restriction of the
interaction to the familiar sum of a quadrupole multipole force and a monopole
pairing force, we have previously studied a semi-microscopic version of the
formalism whose framework is nevertheless more comprehensive than any
previously applied to the problem. We obtained solutions for low-lying bands of
several strongly deformed odd rare earth nuclei and found good agreement with
experiment, except for an exaggerated staggering of levels for K=1/2 bands,
which can be understood as a manifestation of the Coriolis attenuation problem.
We argue that within the formalism utilized, the only way to improve the
physics is to add interactions to the model Hamiltonian. We verify that by
adding a magnetic dipole interaction of essentially fixed strength, we can fit
the K=1/2 bands without destroying the agreement with other bands. In addition
we show that our solution also fits 163Er, a classic test case of Coriolis
attenuation that we had not previously studied.


title:
Neutrino-induced neutron spallation and supernova r-process
  nucleosynthesis

abstract:
  In order to explore the consequences of the neutrino irradiation for the
supernova r-process nucleosynthesis, we calculate the rates of charged-current
and neutral-current neutrino reactions on neutron-rich heavy nuclei, and
estimate the average number of neutrons emitted in the resulting spallation.
Our results suggest that charged-current $\nu_e$ captures can be important in
breaking through the waiting-point nuclei at N=50 and 82, while still allowing
the formation of abundance peaks. Furthermore, after the r-process freezes out,
there appear to be distinctive neutral-current and charged-current
postprocessing effects. A subtraction of the neutrino postprocessing effects
from the observed solar r-process abundance distribution shows that two mass
regions, A=124-126 and 183-187, are inordinately sensitive to neutrino
postprocessing effects. This imposes very stringent bounds on the freeze-out
radii and dynamic timescales governing the r-process. Moreover, we find that
the abundance patterns within these mass windows are entirely consistent with
synthesis by neutrino interactions. This provides a strong argument that the
r-process must occur in the intense neutrino flux provided by a core-collapse
supernova.


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

abstract:
  Two new sets of QCD sum rules for the nucleon axial coupling constants are
derived using the external-field technique and generalized interpolating
fields. An in-depth study of the predicative ability of these sum rules is
carried out using a Monte-Carlo based uncertainty analysis. The results show
that the standard implementation of the QCD sum rule method has only marginal
predicative power for the nucleon axial coupling constants, as the relative
errors are large. The errors range from approximately 50 to 100% compared to
the nucleon mass obtained from the same method, which has only 10% to 25%
error. The origin of the large errors is examined. Previous analyses of these
coupling constants are based on sum rules that have poor OPE convergence and
large continuum contributions. Preferred sum rules are identified and their
predictions are obtained. We also investigate the new sum rules with an
alternative treatment of the problematic transitions which are not
exponentially suppressed in the standard treatment. The new treatment provides
exponential suppression of their contributions relative to the ground state.
Implications for other nucleon current matrix elements are also discussed.


title: Frame Dependence of Parton Cascade Results

abstract:
  Frame dependence of parton cascade results is studied for different schemes
of doing cascade simulations. We show that different schemes do not always
agree and results may have strong frame dependence. When the interaction range
is on the order of mean free path and the collisions are done in the two
particle center of mass frame, the results are not sensitive to the global
frame that the collisions are ordered. Effects of different differential cross
sections are also discussed.


title:
$NN \to NN \pi$ reaction near threshold in a covariant
  one-boson-exchange model

abstract:
  We calculate the cross sections for the $p(p,n\pi^{+})p$ and $p(p,p\pi^{0})p$
reactions for proton beam energies near threshold in a covariant
one-boson-exchange model, which incorporates the exchange of $\pi$, $\rho$,
$\sigma$ and $\omega$ mesons and treats both nucleon and delta isobar as
intermediate states. The final state interaction effects have also been
included. The $\omega$ meson exchange is found to contribute significantly at
these energies, which, along with other meson exchanges, provides an excellent
agreement with the data. The cross sections at beam energies $\leq$ 300 MeV are
almost free from the contributions of the $\Delta$ isobar excitation.


title:
Quadrupole and Hexadecapole Correlations in Rotating Nuclei Studied
  within the Single-j Shell Model

abstract:
  The influence of quadrupole and hexadecapole residual interactions on
rotational bands is investigated in a single-j shell model. An exact
shell-model diagonalization of quadrupole-plus-hexadecapole interaction can
sometimes produce a staggering of energy levels in the yrast bands.


title:
Transition from the Seniority to the Anharmonic Vibrator Regime in
  Nuclei

abstract:
  A recent analysis of experimental energy systematics suggests that all
collective nuclei fall into one of three classes -- seniority, anharmonic
vibrational, or rotational -- with sharp phase transitions between them. We
investigate the transition from the seniority to the anharmonic vibrator regime
within a shell model framework involving a single large j-orbit. The
calculations qualitatively reproduce the observed transitional behavior, both
for U(5) like and O(6) like nuclei. They also confirm the preeminent role
played by the neutron-proton interaction in producing the phase transition.


title: Influence of rescattering on the spectra of strange particles

abstract:
  Applying a new method of rescattering which is based on the neural network
technique we study the influence of rescattering on the spectra of strange
particles produced in heavy ion reactions. In contradistinction to former
approaches the rescattering is done explicitly and not in a perturbative
fashion. We present a comparison of our calculations for the system
Ni(1.93AGeV)+Ni with recent data of the FOPI collaboration. We find that even
for this small system rescattering changes the observables considerably but
does not invalidate the role of the kaons as a messenger from the high density
zone. We cannot confirm the conjecture that the kaon flow can be of use for the
determination of the optical potential of the kaon.


title: A functional approach to nuclear electromagnetic response functions

abstract:
  The separated electromagnetic responses $R_L(q,\omega)$ and $R_T(q,\omega)$
for inclusive electron scattering off nuclei are studied within a functional
scheme.


title:
One-body dissipation and chaotic dynamics in a classical simulation of a
  nuclear gas

abstract:
  In order to understand the origin of one-body dissipation in nuclei, we
analyze the behavior of a gas of classical particles moving in a
two-dimensional cavity with nuclear dimensions. This "nuclear" billiard has
multipole-deformed walls which undergo periodic shape oscillations. We
demonstrate that a single particle Hamiltonian containing coupling terms
between the particles' motion and the collective coordinate induces a chaotic
dynamics for any multipolarity, independently on the geometry of the billiard.
If the coupling terms are switched off the "wall formula" predictions are
recovered. We discuss the dissipative behavior of the wall motion and its
relation with the order-to-chaos transition in the dynamics of the microscopic
degrees of freedom.


title:
The Two-Pion Exchange NN-Potential in Nuclear Matter and Nuclear
  Stability

abstract:
  A meson exchange model of the $\pi\pi$ interaction which fits free $\pi\pi$
scattering data is used to calculate the interactions of pions in nuclear
matter as a function of nuclear density. Polarization of the nuclear medium by
the pions results in a marked increase in the s-wave $\pi\pi$ attraction at low
energy. The influence of this effect on the nucleon-nucleon interaction is a
corresponding increase with density of the $NN$ central potential due to the
exchange of two correlated pions, resulting in an $NN$ interaction which fails
to saturate. A possible mechanism for restoring the theoretical stability of
nuclear matter is explored and found to be effective.


title:
Nuclear Matter with a Bose Condensate of Dibaryons in Relativistic
  Mean-Field Theory

abstract:
  If sufficiently light dibaryon resonances exist, a Bose condensate of
dibaryons can occur in nuclear matter before the quark-hadron phase transition.
Within a relativistic mean-field model we show that heterophase
nuclear-dibaryon matter is for a wide set of parameters energetically more
favorable than normal nuclear matter. Production of dibaryons is, however,
relatively suppressed as compared to estimates based on the model of
non-interacting nucleons and dibaryons.


title: A New Look into the Partial Wave Decomposition of Three-Nucleon Forces

abstract:
  We demonstrate that the partial wave decomposition of three-nucleon forces
used up to now in momentum space has to be necessarily unstable at high partial
waves. This does not affect the applications performed up to now, which were
restricted to low partial waves. We present a new way to perform the partial
wave decomposition which is free of that defect. This is exemplified for the
most often used $2\pi$-exchange Tuscon-Melbourne three-nucleon force. For the
lower partial waves the results of the old method are reproduced.


title:
The Delta-Delta Intermediate State in 1S0 Nucleon-Nucleon Scattering
  From Effective Field Theory

abstract:
  We examine the role of the Delta-Delta intermediate state in low energy NN
scattering using effective field theory. Theories both with and without pions
are discussed. They are regulated with dimensional regularization and MSbar
subtraction. We find that the leading effects of the Delta-Delta state can be
absorbed by a redefinition of the contact terms in a theory with nucleons only.
It does not remove the requirement of a higher dimension operator to reproduce
data out to moderate momentum. The explicit decoupling of the Delta-Delta state
is shown for the theory without pions.


title: Kaon Zero-Point Fluctuations in Neutron Star Matter

abstract:
  We investigate the contribution of zero-point motion, arising from
fluctuations in kaon modes, to the ground state properties of neutron star
matter containing a Bose condensate of kaons. The zero-point energy is derived
via the thermodynamic partition function, by integrating out fluctuations for
an arbitrary value of the condensate field. It is shown that the vacuum
counterterms of the chiral Lagrangian ensure the cancellation of divergences
dependent on $\mu$, the charge chemical potential, which may be regarded as an
external vector potential. The total grand potential, consisting of the
tree-level potential, the zero-point contribution, and the counterterm
potential, is extremized to yield a locally charge neutral, beta-equilibrated
and minimum energy ground state. In some regions of parameter space we
encounter the well-known problem of a complex effective potential. Where the
potential is real and solutions can be obtained, the contributions from
fluctuations are found to be small in comparison with tree-level contributions.


title:
Phi meson production cross sections in pion-baryon and baryon-baryon
  interactions

abstract:
  Phi meson production in pion-baryon and baryon-baryon interactions near the
production threshold is studied in a boson-exchange model. Parameters in this
model are either taken from the Bonn model for the nucleon-nucleon potential or
determined from the measured phi meson decay width and the experimental data
for the reactions $\pi^-p\arr \phi n$ and $pp\arr pp\phi$. The isospin-averaged
cross sections for the reactions $\pi N\arr \phi N$, $\pi \Delta \arr \phi N$,
$NN\arr NN\phi$, which are needed in transport models to study phi meson
production in heavy-ion collisions at subthreshold energies, have been
evaluated. For the reactions $N\Delta\arr NN\phi$ and $\Delta\Delta\arr
NN\phi$, which become singular when the exchanged pion is on-shell, the Peierls
method is used to calculate their cross sections. We find that the cross
section for the reaction $\pi N\arr\phi N$ is much larger than the other cross
sections.


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

abstract:
  We critically discuss the recently developed quantum-mechanical equivalent
photon spectrum by Benesh et al. We point out that the key point, the strong
absorption in heavy ion collisions, is not treated adequately. Conclusions
drawn from such a spectrum are invalid. Equivalent photon spectra appropriate
for heavy ions, have been given before in quantal as well as semiclassical
versions and were found to be very satisfactory.


title:
Consistent Treatment of Relativistic Effects in Electrodisintegration of
  the Deuteron

abstract:
  The influence of relativistic contributions to deuteron electrodisintegration
is systematically studied in various kinematic regions of energy and momentum
transfer. As theoretical framework the equation-of-motion and the unitarily
equivalent S-matrix approaches are used. In a (p/M)-expansion, all leading
order relativistic $\pi$-exchange contributions consistent with the Bonn OBEPQ
model are included. In addition, static heavy meson exchange currents including
boost terms, $\gamma\pi\rho/\omega$-currents, and $\Delta$-isobar contributions
are considered. Sizeable effects from the various relativistic two-body
contributions, mainly from $\pi$-exchange, have been found in inclusive form
factors and exclusive structure functions for a variety of kinematic regions.


title: Medium effects in high energy heavy-ion collisions

abstract:
  The change of hadron properties in dense matter based on various theoretical
approaches are reviewed. Incorporating these medium effects in the relativistic
transport model, which treats consistently the change of hadron masses and
energies in dense matter via the scalar and vector fields, heavy-ion collisions
at energies available from SIS/GSI, AGS/BNL, and SPS/CERN are studied. This
model is seen to provide satisfactory explanations for the observed enhancement
of kaon, antikaon, and antiproton yields as well as soft pions in the
transverse direction from the SIS experiments. In the AGS heavy-ion
experiments, it can account for the enhanced $K^+/\pi^+$ ratio, the difference
in the slope parameters of the $K^+$ and $K^-$ transverse kinetic energy
spectra, and the lower apparent temperature of antiprotons than that of
protons. This model also provides possible explanations for the observed
enhancement of low-mass dileptons, phi mesons, and antilambdas in heavy-ion
collisions at SPS energies. Furthermore, the change of hadron properties in hot
dense matter leads to new signatures of the quark-gluon plasma to hadronic
matter transition in future ultrarelativistic heavy-ion collisions at RHIC/BNL.


title:
Density dependence of the MIT bag parameters from the field theory of
  hadrons

abstract:
  A self-consistent description of the MIT bag parameters as functions of the
nuclear matter density is presented. The subnuclear degrees of freedom are
treated in the Quark-Meson Coupling Model, considering the equilibrium
conditions for the bag in the nuclear medium. The hadronic interaction is
described in the framework of the quantum field theory of hadrons through
several models. We have obtained the behavior of the bag radius and the bag
parameters $B$ and $z_0$, taking their derivatives with respect to the mean
field value of the scalar meson as free parameters. A discussion on the
variation range of these derivatives is given.


title: Nuclear Astrophysics in Storage Rings

abstract:
  Nuclear reaction cross sections are usually very small in typical
astrophysical environments. It has been one of the major challenges of
experimental nuclear astrophysics to assess the magnitude of these cross
sections in the laboratory. For a successful experiment high luminosity beams
are needed. Increasing the target width, one also increases the reaction
yields. But, this is of limited use due to multiple scattering in the target.
Storage rings are a very good way to overcome these difficulties. In principle,
they can be tuned to large luminosities, and have the advantage of crossing the
interaction region many times per second (typically one million/s),
compensating low density internal gas targets, or low reaction rates in
beam-beam collisions. Storage rings are also ideal tools for precise
measurements of masses and beta-decay lifetimes of nuclei of relevance for
astrophysics.


title: The Weak Decay of Hypernuclei

abstract:
  The nonmesonic weak decay of $\Lambda$ hypernuclei is studied in a shell
model framework. A complete strangeness-changing weak $\Lambda N \to NN$
transition potential, based on one boson exchange, is constructed by including
the exchange of the pseudoscalar mesons $\pi$, K, $\eta$ as well as the vector
mesons $\rho, \omega$, and K$^*$, whose weak coupling constants are obtained
from soft meson theorems and SU(6)$_w$. General expressions for nucleons in
arbitrary shells are obtained. The transition matrix elements include realistic
$\Lambda$N short-range correlations and NN final state interactions based on
the Nijmegen baryon-baryon potential. The decay rates are found to be
especially sensitive to the inclusion of the strange mesons, K and K$^*$, even
though the role of kaon exchange is found to be reduced with recent couplings
obtained from next-to-leading order Chiral Perturbation Theory. With the weak
couplings used in this study the rates remain dominated by the pion-exchange
mechanism since the contributions of heavier mesons either cancel each other or
are suppressed by form factors and short-range correlations. The total decay
rate therefore remains in agreement with present measurements. However, the
partial rates which are even more sensitive to the inclusion of heavier mesons
cannot be reconciled with the data. The proton asymmetry changes by 50% once
heavier mesons are included and agrees with the available data.


title: Resonance contributions to HBT correlation radii

abstract:
  We study the effect of resonance decays on intensity interferometry for heavy
ion collisions. Collective expansion of the source leads to a dependence of the
two-particle correlation function on the pair momentum K. This opens the
possibility to reconstruct the dynamics of the source from the K-dependence of
the measured HBT radii. Here we address the question to what extent resonance
decays can fake such a flow signal. Within a simple parametrization for the
emission function we present a comprehensive analysis of the interplay of flow
and resonance decays on the one- and two-particle spectra. We discuss in detail
the non-Gaussian features of the correlation function introduced by long-lived
resonances and the resulting problems in extracting meaningful HBT radii. We
propose to define them in terms of the second order q-moments of the correlator
C(q, K). We show that this yields a more reliable characterisation of the
correlator in terms of its width and the correlation strength `lambda' than
other commonly used fit procedures. The normalized fourth-order q-moments
(kurtosis) provide a quantitative measure for the non-Gaussian features of the
correlator. At least for the class of models studied here, the kurtosis helps
separating effects from expansion flow and resonance decays, and provides the
cleanest signal to distinguish between scenarios with and without transverse
flow.


title:
Model-Independent Extraction of the N*(1535) Electrostrong Form Factor
  from Eta Electroproduction

abstract:
  We analyze the existing data on electroproduction of eta mesons in the region
of W~1.5GeV, and extract an electrostrong form factor for the N*(1535)
electroexcitation and decay into the eta-N channel, which is found to be
relatively insensitive to the uncertainties of the effective Lagrangian
approach. this extracted quantity is of interest in the QCD description of
relevant baryons.


title: New Type of Collective Motion for N $\sim$ Z Nuclei

abstract:
  We study a new type of collective motion with alpha-particle type of
correlations and show that it may be relevant for N $\sim$ Z nuclei.


title: Chemical relaxation time of pions in hot hadronic matter

abstract:
  We calculate characteristic time scales for chemical equilibration of pions
in hot hadronic matter using an effective chiral Lagrangian. We find that
inelastic processes involving the vector and axial vector mesons reduce the
chemical equilibration time by a factor of $\sim 10$ compared to the result
previously calculated in chiral perturbation theory. For a temperature of
$T\sim 150 MeV$ we obtain a chemical relaxation time of $\tau_{ch} \simeq 10
fm/c$, which is comparable with typical time scales for a hadronic system
generated in SPS-energy heavy ion collisions. The effect of baryons is also
estimated and found to be negligible for SPS-energies but important for
AGS-energies. We predict, that chemical freeze-out should take place at
considerable higher temperatures $\Delta T \simeq 20 MeV$ than thermal
freeze-out and that the hadronic phase would not sustain a pion chemical
potential larger than $100 MeV$.


title:
Solution of the Skyrme-Hartree-Fock equations in the Cartesian deformed
  harmonic oscillator basis. (I) The method

abstract:
  We describe a method of solving the nuclear Skyrme-Hartree-Fock problem by
using a deformed Cartesian harmonic oscillator basis. The complete list of
expressions required to calculate local densities, total energy, and
self-consistent fields is presented, and an implementation of the
self-consistent symmetries is discussed. Formulas to calculate matrix elements
in the Cartesian harmonic oscillator basis are derived for the nuclear and
Coulomb interactions.


title:
Solution of the Skyrme-Hartree-Fock equations in the Cartesian deformed
  harmonic oscillator basis. (II) The program HFODD

abstract:
  We describe the code HFODD which solves the nuclear Skyrme-Hartree-Fock
problem by using the deformed Cartesian harmonic oscillator basis. The user has
a possibility of choosing among various symmetries of the nuclear HF problem
for rotating or non-rotating nuclei; they vary from the non-axial
parity-invariant nuclear shapes, through those also breaking the intrinsic
parity, towards the least-restrictive case corresponding to only one symmetry
plane. The code provides a solution for a complete superdeformed rotational
band in an A~150 nucleus within one CPU hour of the CRAY C-90 supercomputer or
within two-three CPU hours of a fast workstation.


title:
Dilepton production in proton-nucleus and nucleus-nucleus collisions at
  SPS energies

abstract:
  Dilepton production in proton- and nucleus-induced reactions is studied in
relativistic transport model using initial conditions determined by the string
dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for
dilepton spectra in proton-nucleus reactions can be well described by the
`conventional' mechanism of Dalitz decay and direct vector meson decay.
However, to provide a quantitative explanation of the observed dilepton spectra
in central S+Au and S+W collisions requires contributions other than these
direct decays. Introducing a decrease of vector meson masses in hot and dense
medium, we find that these heavy-ion data can also be satisfactorily explained.
This agrees with our earlier conclusions based on a fire cylinder model. We
also give predictions for Pb+Au collisions at 160 GeV/nucleon using current
CERES mass resolution and acceptance.


title: Transverse Radial Expansion and Directed Flow

abstract:
  The effects of an interplay of radial expansion of the thermalized system
created in a heavy ion collision and directed flow are discussed. It is shown
that the study of azimuthal anisotropy of particle distribution as a function
of rapidity and transverse momentum could reveal important information on both
radial and directed flow.


title:
Light-cone QCD predictions for elastic ed-scattering in the intermediate
  energy region

abstract:
  The contributions of helicity-flip matrix elements to the deuteron form
factors are discussed in the light-cone frame. Normalized $A(Q^2)$, $B(Q^2)$,
$G_Q(Q^2)$ and $T_{20}$ are obtained in a simple QCD-inspired model. We find
that $G_{+-}^+$ plays an important role in $G_Q(Q^2)$. Our numerical results
are consistent with the data in the intermediate energy region.


title: Prospects for spin physics in semi-inclusive processes

abstract:
  I discuss inclusive and semi-inclusive lepton-hadron scattering emphasizing
the importance of polarization in order to study various single or double spin
asymmetries and the importance of particle identification and angular
resolution in the dectection of final state particles to study azimuthal
asymmetries. The observables obtained in this way enable a detailed study of
quark and gluon correlations in hadrons.


title:
Expanding Quark-Gluon Plasmas: Transverse Flow, Chemical Equilibration
  and Electromagnetic Radiation

abstract:
  We investigate the chemical equilibration of the parton distributions in
collisions of two heavy nuclei. We use initial conditions obtained from a
self-screened parton cascade calculation and, for comparison, from the HIJING
model. We consider a one-dimensional, as well as a three-dimensional expansion
of the parton plasma and find that the onset of the transverse expansion
impedes the chemical equilibration. At energies of 100 GeV/nucleon, the results
for one-dimensional and three-dimensional expansion are quite similar except at
large values of the transverse radius. At energies of several TeV/nucleon, the
plasma initially approaches chemical equilibrium, but then is driven away from
it, when the transverse velocity gradients develop. We find that the total
parton multiplicity density remains essentially unaffected by the flow, but the
individual concentrations of quarks, antiquarks, and gluons are sensitive to
the transverse flow. The consequences of the flow are also discernible in the
transverse momenta of the partons and in the lepton pair spectra, where the
flow causes a violation of the so-called $M_T$ scaling.


title:
Dilepton Production from AGS to SPS Energies within a Relativistic
  Transport Approach

abstract:
  We present a nonperturbative dynamical study of $e^+e^-$ production in
proton-nucleus and nucleus-nucleus collisions from AGS to SPS energies on the
basis of the covariant transport approach HSD. For p + Be reactions the
dilepton yield for invariant masses $M \leq 1.4$ GeV is found to be dominated
by the decays of the $\eta, \rho, \omega$ and $\Phi$ mesons at all energies
from 10 -- 450 GeV. For nucleus-nucleus collisions, however, the dilepton yield
shows an additional large contribution from $\pi^+\pi^-$, $K^+K^-$ and $\pi
\rho$ channels. Systematic studies are presented for the 'free' meson mass
scenario in comparison to a 'dropping' meson mass scenario at finite baryon
density. We find that for 'dropping' meson masses the invariant dilepton mass
range 0.35 GeV $\leq M \leq$ 0.65 GeV is increased in comparison to the 'free'
meson mass scenario and that the data of the CERES-collaboration for
nucleus-nucleus collisions can be described much better within the 'dropping'
mass scheme. We study in detail the contributions from the various dilepton
channels as a function of the transverse momentum and rapidity of the lepton
pair as well as a function of the charged particle multiplicity. Furthermore,
various direct photon channels for S + Au at 200 GeV/u are computed and found
to be well below the upper bounds measured by the WA80-collaboration.


title:
Low Energy Pion-Nucleus Interactions: Nuclear Deep Inelastic Scattering,
  Drell-Yan and Missing Pions

abstract:
  The experimental discovery that the nucleus is approximately transparent to
low energy pions is reviewed. The consequences of this for nuclear deep
inelastic scattering and Drell-Yan interactions are discussed. I argue that low
energy nucleus data imply that there is little nuclear enhancement of the pion
cloud of a nucleon, and try to interpret this in terms of nucleon-nucleon
correlations.


title: Pseudo-spin as a Relativistic Symmetry

abstract:
  We show that pseudo - spin symmetry in nuclei could arise from nucleons
moving in a relativistic mean field which has an attractive scalar and
repulsive vector potential nearly equal in magnitude.


title:
Full-Folding Optical Potentials for Elastic Nucleon-Nucleus Scattering
  based on Realistic Densities

abstract:
  Optical model potentials for elastic nucleon nucleus scattering are
calculated for a number of target nuclides from a full-folding integral of two
different realistic target density matrices together with full off-shell
nucleon-nucleon t-matrices derived from two different Bonn meson exchange
models. Elastic proton and neutron scattering observables calculated from these
full-folding optical potentials are compared to those obtained from `optimum
factorized' approximations in the energy regime between 65 and 400 MeV
projectile energy. The optimum factorized form is found to provide a good
approximation to elastic scattering observables obtained from the full-folding
optical potentials, although the potentials differ somewhat in the structure of
their nonlocality.


title: Vacuum Nucleon Loops and Naturalness

abstract:
  Phenomenological studies support the applicability of naturalness and naive
dimensional analysis to hadronic effective lagrangians for nuclei. However,
one-baryon-loop vacuum contributions in renormalizable models give rise to
unnatural coefficients, which indicates that the quantum vacuum is not
described adequately. The effective lagrangian framework accommodates a more
general characterization of vacuum contributions without reference to a Dirac
sea of nucleons.


title:
Thermal Particle and Photon Production in Pb+Pb Collisions with
  Transverse Flow

abstract:
  Particle and photon production is analyzed in the presence of transverse flow
using two approximations to describe the properties of the hadronic medium, one
containing only $\pi, \rho, \omega$, and $\eta$ mesons (simplified equation of
state) and the other containing hadrons and resonances from the particle data
table. Both are considered with and without initial quark gluon plasma
formation. In each case the initial temperature is fixed by requiring
$dN_{ch}/dy \sim$ 550 in the final state. It is shown that most observables are
very sensitive to the equation of state. This is particularly evident when
comparing the results of the simplified equation of state in the scenarios with
and without phase transition. The hadronic gas scenario leads to a
substantially higher rate for the $p_T$-distribution of all particles. In the
complete equation of state with several hundreds of hadronic resonances, the
difference between the scenarios with and without phase transition is rather
modest. Both photon and particle spectra, in a wide $p_T$ range, show very
similar behavior. It is therefore concluded that from the $p_T$ spectra it will
be hard to disentangle quark gluon plasma formation in the initial state. It is
to be stressed however, that there are conceptual difficulties in applying a
pure hadronic gas equation of state at SPS-energies. The phase transition
scenario with a quark gluon plasma present in the initial state seems to be the
more natural one.


title:
The Linear Sigma-Model in the 1/N-Expansion via Dynamical Boson Mappings
  and Applications to $\pi\pi$-Scattering

abstract:
  We present a non-perturbative method for the study of the O(N+1)-version of
the linear sigma-model. Using boson-mapping techniques, in close analogy to
those well-known for fermionic systems, we obtain a systematic 1/N-expansion
for the Hamiltonian which is symmetry-conserving order by order. The leading
order for the Hamiltonian is evaluated explicitly and we apply the method to
$\pi\pi$-scattering, in deriving the T-matrix to leading order.


title: Useful Bases for Problems in Nuclear and Particle Physics

abstract:
  A set of exactly computable orthonormal basis functions that are useful in
computations involving constituent quarks is presented. These basis functions
are distinguished by the property that they fall off algebraically in momentum
space and can be exactly Fourier-Bessel transformed. The configuration space
functions are associated Laguerre polynomials multiplied by an exponential
weight, and their Fourier-Bessel transforms can be expressed in terms of Jacobi
polynomials in $\Lambda^2/(k^2 + \Lambda^2)$. A simple model of a meson
containing a confined quark-antiquark pair shows that this basis is much better
at describing the high-momentum properties of the wave function than the
harmonic-oscillator basis.


title: Chiral Phase Transition at Finite Temperature in the Linear Sigma Model

abstract:
  We study the chiral phase transition at finite temperature in the linear
sigma model by employing a self-consistent Hartree approximation. This
approximation is introduced by imposing self-consistency conditions on the
effective meson mass equations which are derived from the finite temperature
one-loop effective potential. It is shown that in the limit of vanishing pion
mass, namely when the chiral symmetry is exact, the phase transition becomes a
weak first order accompanying a gap in the order parameter as a function of
temperature. This is caused by the long range fluctuations of meson fields
whose effective masses become small in the transition region. It is shown,
however, that with an explicit chiral symmetry breaking term in the Lagrangian
which generates the realistic finite pion mass the transition is smoothed out
irrespective of the choice of coupling strength.


title:
The effect of electro-magnetic formfactors on dilepton production off
  pp-collisions

abstract:
  We investigate the effect of the electric formfactor on dilepton production
off pp-collisions. In the model we use, the formfactor is separated in a
pion-cloud contribution and a Vector Meson Dominance part. We find that the
dilepton spectrum is hardly affected by the pion-cloud part, but significantly
by the VMD contribution. We point out that data with sufficient resolution
would provide a crucial test of the validity of VMD for the nucleon formfactor
in the timelike region.


title: Detectability of Strange Matter in Heavy Ion Experiments

abstract:
  We discuss the properties of two distinct forms of hypothetical strange
matter, small lumps of strange quark matter (strangelets) and of hyperon matter
(metastable exotic multihypernuclear objects: MEMOs), with special emphasis on
their relevance for present and future heavy ion experiments. The masses of
small strangelets up to A = 40 are calculated using the MIT bag model with
shell mode filling for various bag parameters. The strangelets are checked for
possible strong and weak hadronic decays, also taking into account multiple
hadron decays. It is found that strangelets which are stable against strong
decay are most likely highly negative charged, contrary to previous findings.
Strangelets can be stable against weak hadronic decay but their masses and
charges are still rather high. This has serious impact on the present high
sensitivity searches in heavy ion experiments at the AGS and CERN facilities.
On the other hand, highly charged MEMOs are predicted on the basis of an
extended relativistic mean-field model. Those objects could be detected in
future experiments searching for short-lived, rare composites. It is
demonstrated that future experiments can be sensitive to a much wider variety
of strangelets.


title:
Completeness Rules for Spin Observables in Pseudoscalar Meson
  Photoproduction

abstract:
  The number and type of measurements needed to ascertain the amplitudes for
pseudoscalar meson photoproduction are analyzed in this paper. It is found that
8 carefully selected measurements can determine the four transversity
amplitudes without discrete ambiguities. That number of measurements is one
less than previously believed. We approach this problem in two distinct ways:
(1) solving for the amplitude magnitudes and phases directly; and (2) using a
bilinear helicity product formulation to map an algebra of measurements over to
the well-known algebra of the $4\times 4$ Gamma matrices. It is shown that the
latter method leads to an alternate proof that 8 carefully chosen experiments
suffice for determining the transversity amplitudes completely. In addition,
Fierz transformations of the Gamma matrices are used to develop useful linear
and nonlinear relationships between the spin observables. These relationships
not only help in finding complete sets of experiments, but also yield important
constraints between the 16 observables for this reaction.


title: E2 component in subcoulomb breakup of ^{8}B

abstract:
  We calculate the angular distribution and total cross section of the ^{7}Be
fragment emitted in the break up reaction of ^{8}B on ^{58}Ni and ^{208}Pb
targets at the subCoulomb beam energy of 25.8 MeV, within the non-relativistic
theory of Coulomb excitation with proper three-body kinematics. The relative
contributions of the E1, E2 and M1 multipolarities to the cross sections are
determined. The E2 component makes up about 65% and 40% of the ^{7}Be total
cross section for the ^{58}Ni and ^{208}Pb targets respectively. We find that
the extraction of the astrophysical S-factor, S_{17}(0), for the
^{7}Be(p,\gamma)^8B reaction at solar energies from the measurements of the
cross sections of the ^{7}Be fragment in the Coulomb dissociation of ^{8}B at
sub-Coulomb energies is still not free from the uncertainties of the E2
component.


title: Baryon Magnetic Moments in a Relativistic Quark Model

abstract:
  Magnetic moments of baryons in the ground-state octet and decuplet are
calculated in a light-front framework. We investigate the effects of quark mass
variation both in the current operator and in the wavefunctions. A simple fit
uses single oscillator wavefunctions for the baryons and allows the three
flavors of quark to have nonzero anomalous magnetic moments. We find a good fit
to the data without allowing for strange quark contributions to the nucleon
moments. A slightly better fit is obtained by allowing for explicit SU(3)_f
breaking in the wavefunctions through a simple mechanism. The predictions for
magnetic moments in our relativistic model are also much less sensitive to the
values chosen for the constituent quark masses than those of nonrelativistic
models. Relativistic effects can be of order 20% in general, and can alter
familiar relationships between the moments based on SU(3)_f and a
nonrelativistic treatment of spin.


title: Two-Pion Exchange Nucleon-Nucleon Potential: Model Independent Features

abstract:
  A chiral pion-nucleon amplitude supplemented by the HJS subthreshold
coefficients is used to calculate the the long range part of the two-pion
exchange nucleon-nucleon potential. In our expressions the HJS coefficients
factor out, allowing a clear identification of the origin of the various
contributions. A discussion of the configuration space behaviour of the loop
integrals that determine the potential is presented, with emphasis on
cancellations associated with chiral symmetry. The profile function for the
scalar-isoscalar component of the potential is produced and shown to disagree
with those of several semi-phenomenological potentials.


title: Variation of hadron masses in finite nuclei

abstract:
  The quark-meson coupling 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 extended to investigate the change of hadron
properties in finite nuclei. Relativistic Hartree equations for spherical
nuclei have been derived from a relativistic quark model of the structure of
bound nucleons and mesons. Using this unified, self-consistent description of
both infinite nuclear matter and finite nuclei, we investigate the properties
of some closed-shell nuclei, and study the changes in the hadron masses of the
non-strange vector mesons, the hyperons and the nucleon in those nuclei. We
find a new, simple scaling relation for the changes of the hadron masses, which
can be described in terms of the number of non-strange quarks in the hadron and
the value of the scalar mean-field in a nucleus.


title:
Microscopic Structure of High-Spin Vibrational States in Superdeformed
  A=190 Nuclei

abstract:
  Microscopic RPA calculations based on the cranked shell model are performed
to investigate the quadrupole and octupole correlations for excited
superdeformed (SD) bands in even-even A=190 nuclei. The K=2 octupole vibrations
are predicted to be the lowest excitation modes at zero rotational frequency.
The Coriolis coupling at finite frequency produces different effects depending
on the neutron and proton number of nucleus. The calculations also indicate
that some collective excitations may produce J(2) moments of inertia almost
identical to those of the yrast SD band. An interpretation of the observed
excited bands invoking the octupole vibrations is proposed, which suggests
those octupole vibrations may be prevalent in even-even SD A=190 nuclei.


title: Heuristic quantization of the cranking model

abstract:
  We propose a simple and systematic method to quantize the cranking model and
to calculate the matrix elements of intrinsic operators entering the
generalized intensity relations. An example of the application is given to show
the Coriolis coupling effects for B(E3) values of the 3- octupole states in Gd
isotopes.


title: The Dirac-Brueckner Approach

abstract:
  In this review, we give a thorough introduction into the Dirac-Brueckner
approach including the mathematical details of the formalism involved.
Furthermore, we present results for nuclear matter, NN scattering in the
nuclear medium, and finite nuclei.


title:
Dilepton Yield in Heavy-Ion Collisions with Bose Enhancement of Decay
  Width

abstract:
  The excess of low invariant mass dilepton yield in heavy ion collisions
arising from reduction in the rho meson mass at finite temperatures is
partially suppressed because of the effect on the width of the rho meson
induced by Bose enhancement, essentially due to emission of pions in a medium
of the pion gas in the central rapidity region. The sensitivity of the effect
on the initial temperature of the hadronic phase is also examined.


title:
A New Nonlinear Liquid Drop Model. Clusters as Solitons on The Nuclear
  Surface

abstract:
  By introducing in the hydrodynamic model, i.e. in the hydrodynamic equations
and the corresponding boundary conditions, the higher order terms in the
deviation of the shape, we obtain in the second order the Korteweg de Vries
equation (KdV). The same equation is obtained by introducing in the liquid drop
model (LDM), i.e. in the kinetic, surface and Coulomb terms, the higher terms
in the second order. The KdV equation has the cnoidal waves as steady-state
solutions. These waves could describe the small anharmonic vibrations of
spherical nuclei up to the solitary waves. The solitons could describe the
preformation of clusters on the nuclear surface. We apply this nonlinear liquid
drop model to the alpha formation in heavy nuclei. We find an additional
minimum in the total energy of such systems, corresponding to the solitons as
clusters on the nuclear surface. By introducing the shell effects we choose
this minimum to be degenerated with the ground state. The spectroscopic factor
is given by the ratio of the square amplitudes in the two minima.


title:
Nuclear Matter Studies with Density-dependent Meson-Nucleon Coupling
  Constants

abstract:
  Due to the internal structure of the nucleon, we should expect, in general,
that the effective meson nucleon parameters may change in nuclear medium. We
study such changes by using a chiral confining model of the nucleon. We use
density-dependent masses for all mesons except the pion. Within a
Dirac-Brueckner analysis, based on the relativistic covariant structure of the
NN amplitude, we show that the effect of such a density dependence in the NN
interaction on the saturation properties of nuclear matter, while not large, is
quite significant. Due to the density dependence of the $g_{\sigma NN}$, as
predicted by the chiral confining model, we find, in particular, a looping
behavior of the binding energy at saturation as a function of the saturation
density. A simple model is described, which exhibits looping and which is shown
to be mainly caused by the presence of a peak in the density dependence of the
medium modified $\sigma N$ coupling constant at low density.
  The effect of density dependence of the coupling constants and the meson
masses tends to improve the results for $E/A$ and density of nuclear matter at
saturation. From the present study we see that the relationship between binding
energy and saturation density may not be as universal as found in
nonrelativistic studies and that more model dependence is exhibited once medium
modifications of the basic nuclear interactions are considered.


title:
Medium effects in K^+ nucleus interaction from consistent analysis of
  integral and differential cross sections

abstract:
  Self consistency in the analysis of transmission measurements for K^+ on
several nuclei in the momentum range of 500-700 MeV/c is achieved with a
"t_{eff}(rho)rho" potential and new results are derived for total cross
sections. The imaginary part of the t_{eff} amplitude is found to increase
linearly with the average nuclear density in excess of a threshold value. This
phenomenological density dependence of the K^+ nucleus optical potential also
gives rise to good agreement with recent measurements of differential cross
sections for elastic scattering of 715 MeV/c K^+ by Li^6 and C.


title: Exclusive reactions in QCD

abstract:
  We review the theory of hard exclusive scattering in Quantum Chromodynamics.
After recalling the classical counting rules which describe the leading scale
dependence of form factors and exclusive cross-sections at fixed angle, the
pedagogical example of the pion form factor is developped in some detail in
order to show explicitely what factorization means in the QCD framework. The
picture generalizes to many hard reactions which are at the heart of the ELFE
project. We briefly present the concepts of color transparency.


title: Is the eta Meson a Goldstone Boson?

abstract:
  The decoupling of the eta meson from the nucleon, as recently deduced from
analyzing \bar p p collisions and eta photoproduction off the proton at
threshold, is shown to provide an argument against the octet Goldstone boson
nature of the eta meson. This argument concerns the structure of the strong
isoscalar axial vector current. A vanishing eta-N coupling means a vanishing
contribution of the eta-pole term to the hypercharge nucleon axial vector
current. Therefore, no partial conservation of the latter can be achieved. This
new situation invalidates the octet Goldberger--Treiman relation for the eta-N
coupling constant that is indicative of the octet Goldstone boson nature of the
eta meson. In such a case there is no longer a compelling reason for the
standard belief that the eta meson should be coupled to the hadronic vacuum
through the hypercharge axial vector current. Rather, it will be coupled to it
as any ordinary neutral pseudoscalar meson via the neutral axial vector current
of the electroweak theory. As a result of the suggested universal structure of
the weak and strong neutral axial vector currents the eta meson satisfies the
strange analog of the Goldberger-Treiman relation so that it acquires features
of a strange Goldstone boson. Hence the eta-NN vertex constant appears
proportional to $\Delta s$, the fraction of nucleon spin carried by the strange
quark sea, thus explaining its suppression naturally.


title:
Quantum Diffusion and Tunneling with Parametric Banded Random Matrix
  Hamiltonians

abstract:
  The microscopic origin of dissipation of a driven quantum many body system is
addressed in the framework of a parametric banded random matrix approach. We
find noticeable violations of the fluctuation-dissipation theorem and we
observe also that the energy diffusion has a markedly non-Gaussian character.
Within the Feynman-Vernon path integral formalism and in the Markovian limit,
we further consider the time evolution of a slow subsystem coupled to such a
``bath'' of intrinsic degrees of freedom. We show that dissipation leads to
qualitative modifications of the time evolution of the density matrix of the
slow subsystem. In either the spatial, momentum or energy representation the
density distribution acquires very long tails and tunneling is greatly
enhanced.

categories: nucl-th chao-dyn cond-mat.mes-hall nlin.CD


title:
Microscopic analysis of quadrupole collective motion in Cr-Fe nuclei: I.
  Renormalization of collective states and interacting-boson-model parameters

abstract:
  We present a new method by which wavefunctions with simple structure are
renormalized so as to contain more complicated structure. This method, called
$H^n$-cooling method, is applied to the study of the quadrupole collective
motion of $^{56}$Fe, $^{54}$Cr, $^{58}$Fe and $^{56}$Cr. The shell-model
wavefunctions of lowest-lying states of these nuclei are well treated by this
method. By using the wavefunctions obtained via the $H^n$-cooling method, IBM-2
parameters are derived from a realistic shell-model hamiltonian and transition
operators. The Majorana interaction becomes sizably repulsive, primarily as an
effect of the renormalization. The bosonic E2 effective-charges are enhanced
due to the renormalization, while a quenching occurs in the M1 and M3
parameters for proton bosons. It is shown that the $\chi$ parameters take
similar values in the hamiltonian and in the E2 operator.


title: Meson Photoproductions of Nucleon In the Quark Model

abstract:
  The meson photoproductions off nucleons in the chiral quark model are
described. The role of the S-wave resonances in the second resonance region is
discussed, and it is particularly important for the Kaon, $\eta$ and $\eta'$
photoproductions.


title: Stochastic variational method with noncentral forces

abstract:
  This paper extends the application of the stochastic variational method to
noncentral interactions. Several examples are presented for three- and
four-nucleon systems with realistic nuclear forces. The correlated Gaussians
easily cope with the strong short range repulsion of the potential and the
stochastic variational method efficiently selects the most important spin,
isospin and orbital angular momentum components of the wave function. The
examples confirm the usefulness and accuracy of the method.


title: Microscopic origins of effective charges in the shell model

abstract:
  We use a large-scale 6 hbar Omega calculation for Li6 with microscopically
derived two-body interaction to construct the 0 hbar Omega 0p-shell effective
hamiltonian, electric quadrupole, and magnetic dipole operators. While the E2
and M1 6 hbar Omega operators are one-body operators with free nucleon charges,
the effective operators are two-body operators with substantially different
renormalization for the isoscalar and isovector matrix elements, especially for
the E2 operator. We show that these operators can be very well approximated by
one-body operators provided that effective proton and neutron charges are used.
The obtained effective charges are compatible with those used in
phenomenological shell-model studies. The two-body part of the effective
operators is estimated.


title: Deformed nuclear halos

abstract:
  Deformation properties of weakly bound nuclei are discussed in the deformed
single-particle model. It is demonstrated that in the limit of a very small
binding energy the valence particles in specific orbitals, characterized by a
very small projection of single-particle angular momentum onto the symmetry
axis of a nucleus, can give rise to the halo structure which is completely
decoupled from the rest of the system. The quadrupole deformation of the
resulting halo is completely determined by the intrinsic structure of a weakly
bound orbital, irrespective of the shape of the core.


title: A chiral bag model approach to delta electroproduction

abstract:
  Helicity amplitudes for the $\gamma^* N \to \Delta$ transition are calculated
using the cloudy bag model. A correction for center-of-mass motion is carried
out using a modified Peierls-Thouless projection method. This reduces the
magnitude of the transition amplitudes at small momentum transfer and enhances
them at modest momentum transfers. Our calculation shows that the pion cloud
contributes substantially to the transition helicity amplitudes, with the final
result giving reasonable agreement with the corresponding experimental values.


title: Nucleon and Delta in a covariant quark-diquark model

abstract:
  We develop a formally covariant quark-diquark model of the nucleon. The
nucleon is treated as a bound state of a constituent quark and a diquark
interacting via a quark exchange. We include both scalar and axial-vector
diquarks. The underlying Bethe-Salpeter equation is transformed into a pair of
coupled Salpeter equations. The space- and timelike electromagnetic form
factors of the nucleon are calculated in the Mandelstam formalism for squared
momentum transfers up to 3 (GeV/c)^2 above threshold. The model is applied also
to the Delta(3/2).


title:
Comparison of the Near-Threshold Production of eta- and K-Mesons in
  Proton-Proton Collisions

abstract:
  The pp -> pp eta and pp -> pLambda K^+ reactions near threshold are dominated
by the first and second S_11 resonance respectively. It is shown that a
one-pion-exchange model exciting these isobars reproduces well the ratio of the
production cross sections. The consequences for this and other channels are
discussed.


title: Feedback from Freeze-out in Hydrodynamics

abstract:
  Most hydrodynamical calculations used in heavy-ion physics ignore the effect
of freeze-out matter carrying energy and momentum away from the expanding
fluid. In a simple one-dimensional model we compare calculated energy density
and velocity profiles, with and without interaction between fluid-like and
freeze-out parts of the system, in order to estimate the importance of this
effect.


title: The Nucleon-Nucleon Potential in the 1/N_c Expansion

abstract:
  The nucleon-nucleon potential is analysed using the 1/N_c expansion of QCD.
The NN potential is shown to have an expansion in 1/N_c^2, and the strengths of
the leading order central, spin-orbit, tensor, and quadratic spin-orbit forces
(including isospin dependence) are determined. Comparison with a successful
phenomenological potential (Nijmegen) shows that the large-N_c analysis
explains many of the qualitative features observed in the nucleon-nucleon
interaction. The 1/N_c expansion implies an effective Wigner supermultiplet
symmetry for light nuclei. Results for baryons containing strange quarks are
presented in an appendix.


abstract:
  Saturation properties and liquid-gas phase transition of nucleus are analysed
in the framework of Hatree-Fock theory. We modify Hill-Wheller formula with a
finite-size-effect parameter by fitting the zero-temperature properties of
nucleus. Employing Gogny effective interaction and phenomenological expression
of Coulomb energy, we give the critical temperature of liquid-gas phase
transition of nucleus being about 12 MeV, which agrees with the result
extracted from heavy-ion collision experiments. It is pointed out that a
phenomenological formula of surface energy of hot nucleus is not avaliable in
the region where nucleon density is far away from the normal density.


title: An Inconsistency in the Simulation of Bose-Einstein Correlations

abstract:
  We show that the formalism commonly used to implement Bose-Einstein
correlations in Monte-Carlo simulations can lead to values of the two-particle
correlator significantly smaller than unity, in the case of sources with strong
position-momentum correlations. This is more pronounced when the phase space of
the emitted particles is strongly reduced by experimental acceptance or
kinematic analysis selections. It is inconsistent with general principles
according to which the Bose-Einstein correlator is larger than unity. This
inconsistency seems to be rooted in the fact that quantum mechanical
localization properties are not taken into account properly.


title: Shape transitions in proton-neutron systems

abstract:
  We explore the possibility of shape transitions in proton-neutron systems
driven by deformation differences between proton and neutron fluids. Within the
framework of the proton-neutron interacting boson model, we show that such
dynamic shape transitions cannot occur in well deformed nuclei but are a
possibility in transitional nuclei. Likely candidates in the Os-Pt isotopes are
discussed and predictions of the model are compared with the existing data.


title: Color Transparency at ELFE

abstract:
  We review the presentations given in the Color Transparency parallel session
held during the second ELFE workshop.


title:
Medium effects in the production and decay of $\omega$- and
  $\rho$-resonances in pion-nucleus interactions

abstract:
  The $\omega$- and $\rho$-resonance production and their dileptonic decay in
$\pi^- A$ reactions at GSI energies are calculated within the intranuclear
cascade (INC) approach. The invariant mass distribution of the dilepton pair
for each resonance is found to have two components which correspond to the
decay of the resonances outside and inside the target nucleus. The latter
components are strongly distorted by the nuclear medium due to
resonance-nucleon scattering and a possible mass shift at finite baryon
density. These medium modifications are compared to background sources in the
dilepton spectrum from $\pi N$ bremsstrahlung and the Dalitz decays of
$\Delta$'s and $\eta$ mesons produced in the reaction.


title: Relativistic Description of Exclusive Deuteron Breakup Reactions

abstract:
  The exclusive deuteron break-up reaction is analyzed within a covariant
approach based on the Bethe-Salpeter equation with realistic meson-exchange
interaction. Relativistic effects in the cross section, tensor analyzing power
and polarization transfer are investigated in explicit form. Results of
numerical calculations are presented for kinematical conditions in forthcoming
p + D reactions at COSY.


title:
Mesonic and Binding Contributions to the EMC Effect in a Relativistic
  Many-body Approach

abstract:
  Starting from a covariant relativistic formalism which uses nucleon and pion
propagators in a nuclear medium, we revise the traditional effects of Fermi
motion, binding and mesonic corrections to the EMC effect. The calculations are
done in a very accurate way, using precise nucleon spectral functions and meson
self-energies and a good reproduction of the EMC data is obtained outside the
shadowing region which is not explored.


title: Lepton Scattering on Nuclei at x > 1 and the Nucleon Spectral Function

abstract:
  We analyze the processes of deep inelastic and quasielastic scattering in the
region of x > 1. These processes are found to be very sensitive to the
information contained in the nucleon spectral function in nuclei, particularly
to the correlations between energy and momentum. Calculations are done using
two spectral functions for nuclear matter and one for finite nuclei, ^{16}O.
Several approximations are also analyzed and are shown to be inaccurate in this
region. These results stress the fact that the region of x > 1 contains
important information on nuclear dynamical correlations.


title:
Quasielastic Versus Inelastic and Deep Inelastic Lepton Scattering in
  Nuclei at x > 1

abstract:
  We have made a thorough investigation of the nuclear structure function W_2A
in the region of 0.8 < x < 1.5 and Q^2 < 20 GeV^2, separating the quasielastic
and inelastic plus deep inelastic contributions. The agreement with present
experimental data is good giving support to the results for both channels.
Predictions are made in yet unexplored regions of x and Q^2 to assert the
weight of the quasielastic or inelastic channels. We find that at Q^2 < 4 GeV^2
the structure function is dominated by the quasielastic contributions for x <
1.5, while for values of Q^2 > 15 GeV^2 and the range of x studied the
inelastic channels are over one order of magnitude bigger than the quasielastic
one. The potential of the structure function at x > 1 as a source of
information on nuclear correlations is stressed once more.


title: Algebraic Approach to Baryon Structure

abstract:
  We present an algebraic approach to the internal structure of baryons in
terms of three constituents. We investigate a collective model in which the
nucleon is regarded as a rotating and vibrating oblate top with a prescribed
distribution of charges and magnetization. We contrast the collective and
single-particle descriptions of baryons and compare the predictions of the
model with existing data on masses, electromagnetic elastic and transition form
factors and strong decays widths.


title: Delta electroproduction in a chiral bag model approach

abstract:
  We study the \gamma^* N -> \Delta transition amplitudes in a recoil corrected
cloudy bag model approach. A modified Peierls-Thouless projection method is
used to construct the Galilean invariant baryon states. The pionic contribution
is found to be significant. The effect of the recoil correction is to reduce
the magnitude of the transition amplitudes at small momentum transfer and to
enhance them at modest momentum transfers.


title: Dissipative Effects in Photon Diagnostics of Quark Gluon Plasma

abstract:
  The effects of dissipation on the space time evolution of matter formed in
ultra-relativistic heavy ion collision is discussed. The thermal photon spectra
for RHIC and LHC energies with viscous flow is considered. The effects of
viscosity in the thermal single photon spectra is seen to be important in QGP
phase as compared to the hadronic phase. Recently available data from WA80
group at SPS energies for $S+Au$ collision are compared with theoretical
calculations. The experimental data do not appear to be compatible with the
formation of matter in the pure hadronic phase.


title:
Single- and double-beta decay Fermi-transitions in an exactly solvable
  model

abstract:
  An exactly solvable model suitable for the description of single and
double-beta decay processes of the Fermi-type is introduced. The model is
equivalent to the exact shell-model treatment of protons and neutrons in a
single j-shell. Exact eigenvalues and eigenvectors are compared to those
corresponding to the hamiltonian in the quasiparticle basis (qp) and with the
results of both the standard quasiparticle random phase approximation (QRPA)
and the renormalized one (RQRPA). The role of the scattering term of the
quasiparticle hamiltonian is analyzed. The presence of an exact eigenstate with
zero energy is shown to be related to the collapse of the QRPA. The RQRPA and
the qp solutions do not include this zero-energy eigenvalue in their spectra,
probably due to spurious correlations. The meaning of this result in terms of
symmetries is presented.


title:
A Precise Determination of the Pion-Nuclear Coupling Parameter from Weak
  Processes in ^3He

abstract:
  We utilize precise weak interaction experiments on atomic muon capture and
beta decay in the A = 3 nuclei, and take into account the effects of nuclear
"anomalous thresholds" to extract the pseudoscalar pi-^3He-^3H coupling
parameter, G^{eff}(m_\pi^2) = 45.8+- 2.4. This is an order of magnitude
improvement in precision over that from the use of pion-nuclear scattering data
and dispersion relations.


title: Neutrinoless Double Beta Decay within QRPA with Proton-Neutron Pairing

abstract:
  We have investigated the role of proton-neutron pairing in the context of the
Quasiparticle Random Phase approximation formalism. This way the neutrinoless
double beta decay matrix elements of the experimentally interesting A= 48, 76,
82, 96, 100, 116, 128, 130 and 136 systems have been calculated. We have found
that the inclusion of proton-neutron pairing influences the neutrinoless double
beta decay rates significantly, in all cases allowing for larger values of the
expectation value of light neutrino masses. Using the best presently available
experimental limits on the half life-time of neutrinoless double beta decay we
have extracted the limits on lepton number violating parameters.


title:
Non-collapsing renormalized QRPA with proton-neutron pairing for
  neutrinoless double beta decay

abstract:
  Using the renormalized quasiparticle random phase approximation (RQRPA), we
calculate the light neutrino mass mediated mode of neutrinoless double beta
decay of Ge76, Mo100, Te128 and Te130. Our results indicate that the simple
quasiboson approximation is not good enough to study the neutrinoless double
beta decay, because its solutions collapse for physical values of g_pp. We find
that extension of the Hilbert space and inclusion of the Pauli Principle in the
QRPA with proton-neutron pairing, allows us to extend our calculations beyond
the point of collapse, for physical values of the nuclear force strength. As a
consequence one might be able to extract more accurate values on the effective
neutrino mass by using the best available experimental limits on the half-life
of neutrinoless double beta decay.


title:
Possibility of observation of supernarrow dibaryons with symmetric wave
  function in $\gamma d --> \pi^{\pm}+\gamma NN$ reactions

abstract:
  The possibility of obsevation of supernarrow dibaryons with symmetric wave
function in reactions $\gamma +d to \pi^+ +\gamma +nn$ and $\gamma +d to \pi^-
+\gamma +pp$ is studied. These dibaryons satisfy the condition $(-1)^{T+S}P=+1$
(where T is the isospin, S is the internal spin and P is the dibaryon parity)
and their decay into two nucleons is suppressed by the Pauly principle. In the
present paper the method of a dibaryon masses reconstruction over the dibaryon
decay products (\gamma nn) and (\gamma pp) is analysed. The Monte-Carlo
simulation is used to choose the optimal location of the detectors, to estimate
the contribution of the main background processes and to calculate the expected
yields of the dibaryon production. It is shown that 100 hours of the exposition
time at the microtron MAMI (Mainz) is quite enough to determine whether or not
the supernarrow dibaryons with symmetric wave function exist.


title: Soft Electromagnetic Radiations from Relativistic Heavy Ion Collisions

abstract:
  The production of low mass dileptons and soft photons from thermalized Quark
Gluon Plasma (QGP) and hadronic matter in relativistic heavy ion collisions is
evaluated. A boost invariant longitudinal and cylindrically symmetric
transverse expansion of the systems created in central collision of lead nuclei
at CERN SPS, BNL RHIC, and CERN LHC, and undergoing a first order phase
transition to hadronic matter is considered. A large production of low mass (M<
0.3 GeV) dileptons, and soft photons (p_T< 0.4 GeV) is seen to emanate from the
bremsstrahlung of quarks and pions. We find an increase by a factor of 2--4 in
the low mass dilepton and soft photon yield as we move from SPS to RHIC
energies, and an increase by an order of magnitude as we move from SPS to LHC
energies. Most of the soft radiations are found to originate from pion driven
processes at SPS and RHIC energies, while at the LHC energies the quark and the
pion driven processes contribute by a similar amount. The study of the
transverse mass distribution is seen to provide interesting details of the
evolution. We also find a unique universal behaviour for the ratio of M^2
weighted transverse mass distribution for M= 0.1 GeV to that for M= 0.2 and 0.3
GeV, as a function of M_T, for SPS, RHIC, and LHC energies, in the absence of
transverse expansion of the system. A deviation from this universal behaviour
is seen as a clear indication of the flow.


title: Antikaon production in nucleon-nucleon reactions near threshold

abstract:
  The antikaon production cross section from nucleon-nucleon reactions near
threshold is studied in a meson exchange model. We include both pion and kaon
exchange, but neglect the interference between the amplitudes. In case of pion
exchange the antikaon production cross section can be expressed in terms of the
antikaon production cross section from a pion-nucleon interaction, which we
take from the experimental data if available. Otherwise, a $K^*$-resonance
exchange model is introduced to relate the different reaction cross sections.
In case of kaon exchange the antikaon production cross section is related to
the elastic $KN$ and $\bar KN$ cross sections, which are again taken from
experimental measurements. We find that the one-meson exchange model gives a
satisfactory fit to the available data for the $NN\to NNK\bar K$ cross section
at high energies. We compare our predictions for the cross section near
threshold with an earlier empirical parameterization and that from phase space
models.


title: Charge dependence of $NN\to d\pi$

abstract:
  We calculate the isospin symmetry violating effects to the reactions
$pp\rightarrow d\pi ^+$ and $np\rightarrow d\pi ^0$ arising from the different
hadron masses and from the Coulomb interaction between the positive pion and
the deuteron. These effects are large enough in the cross section and analyzing
power $A_y$ that they should be taken into account in comparisons of accurate
experiments in different charge channels.


title:
Monopole giant resonances and nuclear compressibility in relativistic
  mean field theory

abstract:
  Isoscalar and isovector monopole oscillations that correspond to giant
resonances in spherical nuclei are described in the framework of time-dependent
relativistic mean-field (RMF) theory. Excitation energies and the structure of
eigenmodes are determined from a Fourier analysis of dynamical monopole moments
and densities. The generator coordinate method, with generating functions that
are solutions of constrained RMF calculations, is also used to calculate
excitation energies and transition densities of giant monopole states.
Calculations are performed with effective interactions which differ in their
prediction of the nuclear matter compression modulus K_nm. Both time-dependent
and constrained RMF results indicate that empirical GMR energies are best
reproduced by an effective force with K_nm \approx 270 MeV.


title:
An Effective Lagrangian with Broken Scale and Chiral Symmetry III:
  Mesons at Finite Temperature

abstract:
  We investigate the finite temperature behavior of the meson sector of an
effective Lagrangian which describes nuclear matter. A method is developed for
evaluating the logarithmic terms in the effective potential which involves
expansion and resummation; the result is written in terms of the exponential
integral. In the absence of explicit chiral symmetry breaking, a phase
transition restores the symmetry at a temperature of 190 MeV; when the pion has
a mass the transition is smooth. At a much higher temperature a first order
phase transition restores scale symmetry.


title:
Enhanced T-odd P-odd Electromagnetic Moments in Reflection Asymmetric
  Nuclei

abstract:
  Collective P- and T- odd moments produced by parity and time invariance
violating forces in reflection asymmetric nuclei are considered. The enhanced
collective Schiff, electric dipole and octupole moments appear due to the
mixing of rotational levels of opposite parity. These moments can exceed
single-particle moments by more than two orders of magnitude. The enhancement
is due to the collective nature of the intrinsic moments and the small energy
separation between members of parity doublets. In turn these nuclear moments
induce enhanced T- and P- odd effects in atoms and molecules. First a simple
estimate is given and then a detailed theoretical treatment of the collective
T-, P- odd electric moments in reflection asymmetric, odd-mass nuclei is
presented and various corrections evaluated. Calculations are performed for
octupole deformed long-lived odd-mass isotopes of Rn, Fr, Ra, Ac and Pa and the
corresponding atoms. Experiments with such atoms may improve substantially the
limits on time reversal violation.


title: A Giant Halo at the Neutron Drip Line

abstract:
  Relativistic Hartree-Bogoliubov (RHB) theory in coordinate space is used to
describe the chain of even-even Zirconium isotopes reaching from Zr116 to the
drip line nucleus Zr140. Pairing correlations are taken into account by a
density dependent force of zero range. For neutron numbers larger than the
magic number N=82 a giant neutron halo outside the core of Zr122 is observed.
It is formed by up to six neutrons.


title: Damping mechanisms of the Delta resonance in nuclei

abstract:
  The damping mechanisms of the Delta(1232) resonance in nuclei are studied by
analyzing the quasi-free decay reactions 12C(pi+,pi+ p)11B and 12C(3He,t pi+
p)11B and the 2p emission reactions 12C(pi+,pp)10B and 12C(3He,t pp)10B. The
coincidence cross sections are calculated within the framework of the
isobar-hole model. It is found that the 2p emission process induced by the
decay of the Delta resonance in the nucleus can be consistently described by a
pi+rho+g' model for the Delta+N -> N+N decay interaction.


title:
Deuteron electrodisintegration near threshold in the Bethe-Salpeter
  approach

abstract:
  In the framework of the covariant Bethe-Salpeter formalism we calculate the
amplitude of electrodisintegration of the deuteron near the threshold energy.
Due to the small relative momentum of the final np-pair, the deuteron break-up
process may be sufficiently described by a transition to the dominant 1S0
channel into the final state. Therefore only one unknown structure function
(form factor) exists. The explicit formula for this form factor is given in
terms of partial Bethe-Salpeter amplitudes. We compare our result to the usual
non-relativistic calculations. The essential role of P-states as well as their
possible link to mesonic exchange currents is discussed.


title: Microscopic Study of Superdeformed Rotational Bands in 151Tb

abstract:
  Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using
the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is
demonstrated that far going similarities between the two approaches exist and
predictions related to the structure of rotational bands calculated within the
two models are nearly parallel. An interpretation scenario for the structure of
the superdeformed bands is presented and predictions related to the exit spins
are made. Small but systematic discrepancies between experiment and theory,
analyzed in terms of the dynamical moments, J(2), are shown to exist. The
pairing correlations taken into account by using the particle-number-projection
technique are shown to increase the disagreement. Sources of these systematic
discrepancies are discussed -- they are most likely related to the yet not
optimal parametrization of the nuclear interactions used.


title: Exclusive diffractive processes and the quark substructure of mesons

abstract:
  Exclusive diffractive processes on the nucleon are investigated within a
model in which the quark-nucleon interaction is mediated by Pomeron exchange
and the quark substructure of mesons is described within a framework based on
the Dyson-Schwinger equations of QCD. The model quark-nucleon interaction has
four parameters which are completely determined by high-energy $\pi N$ and $K
N$ elastic scattering data. The model is then used to predict vector-meson
electroproduction observables. The obtained $\rho$- and $\phi$-meson
electroproduction cross sections are in excellent agreement with experimental
data. The predicted $q^2$ dependence of $J/\psi$-meson electroproduction also
agrees with experimental data. It is shown that confined-quark dynamics play a
central role in determining the behavior of the diffractive, vector-meson
electroproduction cross section. In particular, the onset of the asymptotic
$1/q^4$ behavior of the cross section is determined by a momentum scale that is
set by the current-quark masses of the quark and antiquark inside the vector
meson. This is the origin of the striking differences between the $q^2$
dependence of $\rho$-, $\phi$- and $J/\psi$-meson electroproduction cross
sections observed in recent experiments.


title: Variational approach to anharmonic collective motion

abstract:
  We derive large-amplitude collective equations of motion from the variational
principle for the time-dependent Schroedinger equation. These equations reduce
to the well-known diabatic formulas for vibrational frequencies in the small
amplitude limit. The finite amplitude expression allows departures from
harmonic behavior of giant resonances to be simply estimated. The relative
shift of the second phonon falls with nuclear mass A as A^(-4/3) in the three
modes we consider: monopole, dipole, and quadrupole. Numerically the effect is
very small in heavy nuclei, as was found with other approaches.


title:
Spectroscopic factors for bound s-wave states derived from neutron
  scattering lengths

abstract:
  A simple and model-independent method is described to derive neutron
single-particle spectroscopic factors of bound s-wave states in $^{A+1}Z =
^{A}Z \otimes n$ nuclei from neutron scattering lengths. Spectroscopic factors
for the nuclei ^{13}C, ^{14}C, ^{16}N, ^{17}O, ^{19}O, ^{23}Ne, ^{37}Ar, and
^{41}Ar are compared to results derived from transfer experiments using the
well-known DWBA analysis and to shell model calculations. The scattering length
of ^{14}C is calculated from the ^{15}C_{g.s.} spectroscopic factor.


title: Generalized seniority scheme in light Sn isotopes

abstract:
  The yrast generalized seniority states are compared with the corresponding
shell model states for the case of the Sn isotopes $^{104-112}$Sn. For most of
the cases the energies agree within 100 keV and the overlaps of the wave
functions are greater than 0.7.


title: Thermal Masses and Equilibrium Rates in the Quark Gluon Phase

abstract:
  We apply the momentum integrated Boltzmann transport equation to study the
time evolution of various quark flavours in the central region of
ultra-relativistic heavy ion collisions. The effects of thermal masses for
quarks and gluons are incorporated to take into account the in-medium
properties of these ingredients of the putative quark gluon plasma. We find
that even under very optimistic conditions, complete chemical equilibration in
the quark gluon plasma appears unlikely.


title: Pre-Cluster Dynamics In Multifragmentation

abstract:
  The initial production and dynamical expansion of hot spherical nuclei are
examined as the first stage both in the projectile-multifragmentation and in
central collision processes. The initial temperatures, which are necessary for
entering the adiabatic spinodal region, as well as the minimum temperatures and
densities, which are reached in the expansion, significantly differ for hard
and soft equations of state. Additional initial compression, occurring in
central collisions leads most likely to a qualitatively different
multifragmentation mechanism. Recent experimental data are discussed in
relation to the results of the proposed model.


title:
Pion Absorption Cross Section for ^2H and ^3He in the Delta-Isobar
  Region: A Phenomenological Connection

abstract:
  The absorption of \pi^+ on ^3He in the $\Delta$-region is evaluated with
exact inclusion of the final state interaction among the three emerging
protons. The absorption is described by a $\pi N \to \Delta$ vertex and a
$N\Delta - NN$ transition t-matrix which are calculated from a phenomenological
model for NN and \pi d reactions. In a calculation where the initial pion
scattering effects are neglected, the predicted peaks of the pion absorption
cross sections for ^2H and ^3He lie too high in energy in relation to the data.
The effect of the final state three-nucleon interaction turns out to be too
small for changing the magnitude and shifting the peak position of the total
absorption cross section for ^3He. We demonstrate that the adjustment of the
peak position for the deuteron cross section by small modifications of the
$\Delta$-parameters, automatically leads to the correct peak position in ^3He.


title: The Flavor Asymmetry of the Nucleon Sea

abstract:
  We re-examine the effects of anti-symmetry on the anti-quarks in the nucleon
sea arising from gluon exchange and pion exchange between confined quarks.
While the effect is primarily to suppress anti-down relative to anti-up quarks,
this is numerically insignificant for the pion terms.


title:
A dispersion theoretical approach to the threshold amplitudes of pion
  photoproduction

abstract:
  We give predictions for the partial wave amplitudes of pion photoproduction
near threshold by means of dispersion relations at fixed t. The free parameters
of this approach are determined by a fit to experimental data in the energy
range 160 MeV $\le E_{\gamma} \le$ 420 MeV. The observables near threshold are
found to be rather sensitive to the amplitudes in the resonance region, in
particular to the $\Delta$ (1232) and $N^*$ (1440). We obtain a good agreement
with the existing threshold data for both charged and neutral pion production.
Our predictions also agree well with the results of chiral perturbation theory,
except for neutral pion production off the neutron.


title: Deformation of Nuclei Close to the Two-Neutron Drip Line in Mg Region

abstract:
  We perform the Hartree-Fock-Bogoliubov (HFB) calculations for ground states
of even Mg isotopes using the Skyrme force and a density-dependent zero-range
pairing force. The HFB equation is solved in a three-dimensional cartesian
mesh, and a convergence of deformation is carefully examined with respect to a
cut-off radius for a check of the calculations. We discuss systematics of the
two-neutron separation energy, deformation and root-mean-square radius. We have
found that 36,38,40Mg have appreciable static deformation, where 40Mg is a
two-neutron drip-line nucleus in our calculation, and the deformations of the
neutron and proton are different in these three nuclei. The deformation
property is analyzed on the basis of the single-particle diagram. It is shown
that N=28 is not a closed shell in Mg as well as Si.


title:
Electroproduction of phi meson from proton and the strangeness in the
  nucleon

abstract:
  We analyze the process $e p \to e p \phi$ near the threshold within $uud -
s\bar s$ cluster model as a probe of the strangeness content of proton. Our
consideration is based on the relativistic harmonic oscillator quark model
which takes into account the Lorentz-contraction effect of the hadron
wavefunctions. We find that the knockout mechanisms are comparable to the
diffractive production of vector-meson-dominance model when only (3-5)% strange
quark admixture is assumed, which should be compared with (10-20)% of the
nonrelativistic quark model prediction. The cross sections of the $uud$- and
$s\bar s$-knockout processes have qualitatively different dependence on the
four-momentum transfer squared to the proton and may be distinguished
experimentally. We also briefly discuss a way to determine the strangeness
content of proton in 5-quark cluster model.


title: New approach to $^4$He charge distribution

abstract:
  We present a study of the $^4$He charge distribution based on realistic
nucleonic wave functions and incorporation of the nucleon's quark substructure.
The central depression of the proton point density seen in modern four-body
calculations is too small by itself to lead to a correct description of the
charge distribution. We utilize six-quark structures calculated in the
Chromodielectric Model for N-N interactions, and we find a swelling of the
proton charge distribution as the internucleon distance decreases. These charge
distributions are combined with the $^4$He wave function using the Independent
Pair Approximation and two-body distributions generated from Green's Function
Monte Carlo calculations. We obtain a reasonably good fit to the experimental
charge distribution without including meson exchange currents.


title: Theory of Eta Photo- and Electroproduction

abstract:
  We analyze the available data on eta photo- and electroproduction, around
W~1535 MeV, in the framework of the effective Lagrangian approach, and extract,
in a nearly model-independent fashion, the electrostrong amplitude for the
gamma+N--> N*(1535)--> N+eta processes. Quark model approaches are shown to be
quite inadequate to explain this property at all Q^2. In particular, at high
Q^2, the extracted amplitude falls much slower than the predictions of the
quark model, as a function of Q^2, a situation similar to the electroexcitation
and decay of Delta(1232). A QCD explanation of these observations is urgently
needed.


title: Molecular and Exotic Dibaryons and Other Hadrons

abstract:
  Experimental evidence has been growing for the existence of both molecular
and exotic dibaryons. The former are dominated by hadron and the latter by
quark-gluon degrees of freedom. Exotic dihadrons are of particular interest
because their properties are closely related to the parameters and
non-perturbative properties of QCD models. Molecular structures provide
information about confinement. Purely exotic models, such as bag and valence
quark models, ignore the multi-hadron phase of confinement. Multi-configuration
quark models and R-matrix boundary condition models better represent the medium
range repulsive effects leading to confinement, predicting higher excitation
energies of the exotic resonances. The ^1S_0 exotic predicted at 2.70 GeV mass
has been identified in pp spin observables, implying that there are several
more even and odd parity exotics in the NN system between 2.6 and 3.0 GeV. The
method also predicts exotic strange and doubly strange dibaryons (including a
di-lambda unbound by about 0.13 GeV) and exotics in baryon and meson channels.
The R-matrix formalism also describes the properties of molecular structures
and enables a classification of these into several types. Observed and
predicted examples of each type are discussed, including the recently observed
d'.


title: Light-front CQM calculations of baryon electromagnetic form factors

abstract:
  The parameter-free predictions for the $N - P_{11}(1440)$ and $N -
P_{33}(1232)$ electromagnetic transition form factors, obtained within our
light-front constituent quark model using eigenfunctions of a baryon mass
operator which includes a large amount of configuration mixing, are reported.
The effects due to small components in the baryon wave functions, such as S'-
and D-wave, are also investigated.


title:
Extended shell-model calculation for even N=82 isotones with realistic
  effective interactions

abstract:
  The shell model within the $2s1d0g_{7/2}0h_{11/2}$ shell is applied to
calculate nuclear structure properties of the even Z=52 - 62, N=82 isotones.
The results are compared with experimental data and with the results of a
quasiparticle random-phase approximation (QRPA) calculation. The interaction
used in these calculations is a realistic two-body G-matrix interaction derived
from modern meson-exchange potential models for the nucleon-nucleon
interaction. For the shell model all the two-body matrix elements are
renormalized by the $\hat{Q}$-box method whereas for the QRPA the effective
interaction is defined by the G-matrix.


title: The nonmesonic weak decay of the hypertriton

abstract:
  The nonmesonic decay of the hypertriton is calculated based on a hypertriton
wavefunction and 3N scattering states, which are rigorous solutions of 3-body
Faddeev equations using realistic NN and hyperon-nucleon interactions. The
pion-exchange together with heavier meson exchanges for the $\Lambda N \to N N
$ transition is considered. The total nonmesonic decay rate is found to be 0.5%
of the free $\Lambda$ decay rate. Integrated as well as differential decay
rates are given. The p- and n- induced decays are discussed thoroughly and it
is shown that the corresponding total rates cannot be measured individually.


title:
Effects of angular momentum projection on the nuclear partition function
  and the observation of the giant dipole resonance in hot nuclei

abstract:
  Procedures for projecting angular momentum in a model describing a hot
nucleus that takes into account large-amplitude quadrupole fluctuations are
discussed. Particular attention is paid to the effect angular-momentum
projection has on the observables associated with the $\gamma$-decay of the
giant-dipole resonance (GDR). We also elaborate on which of the different
projection methods provides the best overall description of the GDR, including
angular distributions. The main consequence of angular-momentum projection is
the appearance of an effective volume element in the integrals associated with
the thermal average of the physical observables. This effective volume element
is controlled by the value of the moments of inertia of the system. In the
limit of rigid-body moments of inertia, the effective volume element is found
to differ only slightly from the volume element associated with the
normalization of the five-dimensional quadrupole oscillator wavefunction in the
$\beta$, $\gamma$, and $\Omega$ space, namely $D[\alpha]=\beta^4d\beta
sin(3\gamma)d\gamma d\Omega$. In the limit of irrotational flow moments of
inertia, the leading behavior in the $\beta$ degree of freedom is
$D[\alpha]\propto \beta d\beta$.


title: Mapping the proton drip-line up to A=70

abstract:
  Coulomb energy differences between mirror nuclei with $A \le 70$ are
calculated within the framework of the nuclear shell model using an effective
Coulomb plus isovector and isotensor interaction. Absolute binding energies for
proton-rich nuclei are predicted by adding the calculated Coulomb shifts to
experimentally measured binding energies for the neutron-rich mirror. The
location of the proton drip-line is investigated, as well as candidates for the
exotic decay mode known as di-proton emission. Taking into account the
lifetimes of competing decay modes and limits imposed by experimental setups,
it is concluded that the best candidates for the observation of correlated
di-proton emission are $^{45}$Fe, $^{48}$Ni, and $^{63}$Se.


title:
Comment on `Measurement of the $\pi^+ \vec p$ analyzing power at 68.3
  MeV'

abstract:
  We comment on a recent paper by Weiser et al. [Phys. Rev. C {\bf 54}, 1930
(1996)]. The authors have performed a single-energy analysis of $\pi^+ p$
scattering data at 68.3 MeV, finding a value for the $S_{31}$ phase shift about
1^o smaller than found in the Karlsruhe-Helsinki (KH) partial-wave analysis.
The authors use this result to argue for a dispersion relation analysis using
recently measured data, so that their effect on the $\pi NN$ coupling constant
(f^2) and $\Sigma$ amplitude can be determined. We note that these tasks were
accomplished prior to the submission of the above paper. We clarify the effect
of this new analyzing power data on f^2 and the $\Sigma$ amplitude.


title:
Accurate Four-Body Response Function with Full Final State Interaction:
  Application to Electron Scattering off 4He

abstract:
  The longitudinal (e,e') response function of 4He is calculated precisely with
full final state interaction. The explicit calculation of the four-body
continuum states is avoided by the method of integral transforms. Precision
tests of the response show the high level of accuracy. Non-relativistic nuclear
dynamics are used. The agreement with experimental data is very good over a
large energy range for all considered momentum transfers (q=300, 400, 500
MeV/c). Only at higher q the theoretical response overestimates the
experimental one beyond the quasi-elastic peak.


title: Recent Calculations of Electromagnetic and Strong Decays of N*

abstract:
  We report on recent calculations of electromagnetic elastic form factors,
helicity amplitudes and strong decay widths of N* resonances. The calculations
are done in a collective constituent model for the nucleon, in which the
resonances are interpreted as rotations and vibrations of an oblate top with a
prescribed distribution of charges and magnetization.


title: Nature of the first excited state of He-4

abstract:
  We study the first excited state of He4 in a microscopic {H3+p,He3+n} cluster
model, including H3 and He3 distortions. The phenomenological 1S0 H3+p
scattering phase shift is well reproduced. We localize a complex pole of the
S-matrix between the H3+p and He3+n thresholds. The corresponding resonance
parameters are E_r=93 keV position relative to H3+p, and Gamma=390 keV width. A
pole search is also performed in an extended R-matrix method, and a resonance
is found with parameters E_r=114 keV and Gamma=392 keV. The R-matrix approach
gives several additional poles, some of which may be connected with an enhanced
threshold effect.


title: Baryon Current Matrix Elements in a Relativistic Quark Model

abstract:
  Current matrix elements and observables for electro- and photo-excitation of
baryons from the nucleon are studied in a light-front framework. Relativistic
effects are examined by comparison to a nonrelativistic model and can typically
be of order 20-25%, but can be larger for certain matrix elements, such as
radial transitions conventionally used to describe the Roper resonance. A
systematic study shows that the violation of rotational covariance of the
baryon transition matrix elements stemming from the use of one-body currents is
generally small.


title: Contributions of strange quarks to the magnetic moment of the proton

abstract:
  Using the Gerasimov-Drell-Hearn sum rule and experimental total cross
sections for photoproduction of $\eta$, $K$ and $\phi$ mesons on the proton, we
obtain upper bounds for the contribution of strange quarks to the anomalous
magnetic moment of the proton, $|\kappa_{s}| \le 0.20 \kappa_{p}$. The proposed
experiments to measure the spin-dependence of the absorption cross section are
expected to lower these bounds considerably. The existing data on $\eta$
production and phenomenological models for $K$ production agree with a negative
sign for $\kappa_{s}$.


title:
Cluster reduction of the four-body Yakubovsky equations in configuration
  space for bound-state problem and low-energy scattering

abstract:
  A method using an expansion of the four-body Yakubovsky wave function
components onto the basis of the Faddeev-equation solutions for the two-cluster
sub-Hamiltonian eigenfunctions is proposed. This expansion reduces the
Yakubovsky differential equations to a system of coupled-channel equations for
functions depending on the relative coordinates between the subsystems of the
two-cluster partitions. On the basis of the resulting equations the
four-nucleon bound-state problem and the zero-energy n-t scattering problem are
solved on the relatively small computer.


title: Imaging of Sources in Heavy-Ion Reactions

abstract:
  Imaging of sources from data within the intensity interferometry is
discussed. In the two-pion case, the relative pion source function may be
determined through the Fourier transformation of the correlation function. In
the proton-proton case, the discretized source function may be fitted to the
correlation data.