title: Pion mass and decay constant

abstract:
  Independent of assumptions about the form of the quark-antiquark scattering
kernel we derive the explicit relation between the pion Bethe-Salpeter
amplitude, Gamma_pi, and the quark propagator in the chiral limit; Gamma_pi
necessarily involves a non-negligible gamma_5 gamma.P term (P is the pion
four-momentum). We also obtain exact expressions for the pion decay constant,
f_pi, and mass, both of which depend on Gamma_pi; and demonstrate the
equivalence between f_pi and the pion Bethe-Salpeter normalisation constant in
the chiral limit. We stress the importance of preserving the axial-vector
Ward-Takahashi identity in any study of the pion itself, and in any study whose
goal is a unified understanding of the properties of the pion and other
hadronic bound states.


title: Nuclear Quadrupole Effects in Deeply Bound Pionic Atoms

abstract:
  We have studied nuclear quadrupole deformation effects in deeply bound pionic
atoms theoretically. We have evaluated the level shifts and widths of the
hyperfine components using the first order perturbation theory and compared
them with the effects of neutron skin. We conclude that the nuclear quadrupole
deformation effects for deeply bound $1s$ and $2p$ states are very difficult to
observe and that the effects could be observed for $3d$ states. We also
conclude that the deformation effects are sensitive to the parameters of the
pion-nucleus optical potential.


title: Hadrons in Dense Matter

abstract:
  There is currently enormous interest in the investigation of how hadron
properties may be altered by immersion in matter. There is strong evidence of a
reduction in the mass of the rho meson from relativistic heavy ion collisions
as well as a hint from a recent experiment on photoproduction in light nuclei.
We briefly review the main theoretical ideas which lead one to expect the mass
of a hadron to change in matter, including the various QCD-based methods,
notably the QCD sum rules, as well as mean-field, quark based models like QMC
and conventional nuclear approaches such as QHD.


title:
Polarization Phenomena in Small-Angle Photoproduction of e+e- Pairs and
  the Gerasimov-Drell-Hearn Sum Rule

abstract:
  Photoproduction of $e^+e^-$ pairs at small angles is investigated as a tool
to determine the functions $f_1$ and $f_2$ entering the real-photon forward
Compton scattering amplitude. The method is based on an interference of the
Bethe-Heitler and the virtual Compton scattering mechanisms, generating an
azimuthal asymmetry in the $e^+$ versus $e^-$ yield. The general case of a
circularly polarized beam and a longitudinally polarized target allows one to
determine both the real and imaginary parts of $f_1$ as well as $f_2$. The
imaginary part of $f_2$ requires target polarization only. We calculate cross
sections and asymmetries of the reaction $p(\gamma,e^+e^-)p$, estimate
corrections and backgrounds, and propose suitable kinematical regions to
perform the experiment. Our investigation shows that photoproduction of
$e^+e^-$-pairs off the proton and light nuclei may serve as a rather sensitive
test of the validity of the Gerasimov-Drell-Hearn sum rule.


title:
Photodisintegration of the Three-Nucleon Systems and their
  Polarizabilities

abstract:
  The total photodisintegration cross sections of three-body nuclei are
calculated with semirealistic NN potentials below pion threshold. Full final
state interaction with Coulomb force is taken into account via the Lorentz
integral transform method. The experimental total cross sections are well
described and the sum rule $\sigma_{-1}(^3$H) agrees with elastic electron
scattering data. The calculated ^3He polarizability is 0.15 fm^3.


title: Coherent Photons and Pomerons in Heavy Ion Collisions

abstract:
  Ultrarelativistic heavy ion beams carry large electromagnetic and strong
absorptive fields, allowing exploration of a variety of physics. Two-photon,
photon-Pomeron, and double Pomeron interactions can probe a huge variety of
couplings and final states. RHIC will be the first heavy ion accelerator
energetic enough to produce hadronic final states via coherent couplings.
Virtual photons from the nuclear EM fields can interact in two-photon
interactions, which can be exploited to study many particle spectroscopy and
QCD topics. Because the photon flux scales as $Z^2$, Two-photon luminosities
are large up to an energy of about \gamma\hbar c/R~ 3 GeV/c. Photon-Pomeron
interactions are sensitive to how different vector mesons, including the
$J/\psi$, interact with nuclear matter. $PP$ collisions rates are sensitive to
the range of the Pomeron. Signals can be separated from backgrounds by using
cuts on final state isolation (rapidity gaps) and $p_\perp$. We present Monte
Carlo studies of different backgrounds, showing that representative signals can
be extracted with good rates and signal to noise ratios.


title:
Relativistic Calculations for the Exclusive Photoproduction of Eta
  Mesons from Complex Nuclei

abstract:
  A relativistic model for the quasifree photoproduction of eta meson from
complex nuclei is developed. The interactions between fields are introduced
through effective Lagrangians. Contributions from several nucleon resonances as
well as nucleon Born terms and vector meson exchange diagrams are included.
Nucleon and eta wavefunctions are solutions of Dirac and Klein-Gordon
equations, respectively. Final state interactions of the outgoing particles are
included via optical potentials. The effects of these interactions on the cross
sections and photon asymmetries are studied and are found to be large.
Calculations indicate that at energies near threshold the exclusive reaction
takes place mainly through formation of the S_{11}(1535) resonance. Comparisons
with the non-relativistic calculations show differences between the two
approaches both for the cross sections and photon asymmetries. We give some
detailed predictions for the reaction observables for exclusive photoproduction
on ^{12}C, ^{16}O and ^{40}Ca.


title: Photoabsorption in nuclei

abstract:
  We calculate the total photoabsorption cross section and cross sections for
inclusive pion and eta photoproduction in nuclei in the energy range from 300
MeV to 1 GeV within the framework of a semi-classical BUU transport model.
Besides medium modifications like Fermi motion and Pauli blocking we focus on
the collision broadening of the involved resonances. The resonance
contributions to the elementary cross section are fixed by fits to partial wave
amplitudes of pion photoproduction. The cross sections for $NR \to NN$, needed
for the calculation of collision broadening, are obtained by detailed balance
from a fit to $NN \to NN\pi$ cross sections. We show that a reasonable
collision broadening is not able to explain the experimentally observed
disappearance of the $D_{13}$(1520)-resonance in the photoabsorption cross
section on nuclei.


title:
Excitation Functions of Stopping Power and Flow in Relativistic
  Heavy-Ion Collisions

abstract:
  Using a relativistic transport (ART) model, we study the stopping power, the
formation of superdense hadronic matter as well as the strength of transverse
and radial flow in central Au+Au collisions at beam momentum from 2 to 12 GeV/c
per nucleon. We find that complete stopping is achieved in the whole beam
momentum range. In particular, the proton rapidity distribution scaled by the
beam rapidity is independent of the beam momentum, and this is in agreement
with the experimental findings. Also, a large volume of superdense hadronic
matter with a local energy density exceeding that expected for the transition
of a hadronic matter to the quark-gluon plasma is formed in collisions at beam
momenta greater than 8 GeV/c per nucleon. Furthermore, it is found that the
transverse flow in these collisions is sensitive to the nuclear equation of
state and decreases with increasing beam momentum. On the other hand, the
radial flow is insensitive to the equation of state, and its strength increases
with beam momentum.


title:
Dissipative Field Theory with Caldeira-Leggett Method and its
  Application to Disoriented Chiral Condensation

abstract:
  The effective field theory including the dissipative effect is developed
based on the Caldeira-Leggett theory at the classical level. After the
integration of the small field fluctuations considered as the field radiation,
the integro-differential field equation is given and shown to include the
dissipative effects. In that derivation, special cares should be taken for the
boundary condition of the integration. Application to the linear sigma model is
given, and the decay process of the chiral condensate is calculated with it,
both analytically in the linear approximation and numerically. With these
results, we discuss the stability of chiral condensates within the quenched
approximation.


title:
Fission and cluster decay of $^{76}$Sr nucleus in the ground-state and
  formed in heavy-ion reactions

abstract:
  Calculations for fission and cluster decay of $^{76}Sr$ are presented for
this nucleus to be in its ground-state or formed as an excited compound system
in heavy-ion reactions. The predicted mass distribution, for the dynamical
collective mass transfer process assumed for fission of $^{76}Sr$, is clearly
asymmetric, favouring $\alpha $-nuclei. Cluster decay is studied within a
preformed cluster model, both for ground-state to ground-state decays and from
excited compound system to the ground-state(s) or excited states(s) of the
fragments.


title: Isospin Physics in Heavy-Ion Collisions at Intermediate Energies

abstract:
  In nuclear collisions induced by stable or radioactive neutron-rich nuclei a
transient state of nuclear matter with an appreciable isospin asymmetry as well
as thermal and compressional excitation can be created. This offers the
possibility to study the properties of nuclear matter in the region between
symmetric nuclear matter and pure neutron matter. In this review, we discuss
recent theoretical studies of the equation of state of isospin-asymmetric
nuclear matter and its relations to the properties of neutron stars and
radioactive nuclei. Chemical and mechanical instabilities as well as the
liquid-gas phase transition in asymmetric nuclear matter are investigated. The
in-medium nucleon-nucleon cross sections at different isospin states are
reviewed as they affect significantly the dynamics of heavy ion collisions
induced by radioactive beams. We then discuss an isospin-dependent transport
model, which includes different mean-field potentials and cross sections for
the proton and neutron, and its application to these reactions. Furthermore, we
review the comparisons between theoretical predictions and available
experimental data. In particular, we discuss the study of nuclear stopping in
terms of isospin equilibration, the dependence of nuclear collective flow and
balance energy on the isospin-dependent nuclear equation of state and cross
sections, the isospin dependence of total nuclear reaction cross sections, and
the role of isospin in preequilibrium nucleon emissions and subthreshold pion
production.


title: Electromagnetic Gauge Invariance of the Cloudy Bag Model

abstract:
  We examine the question of the gauge invariance of electromagnetic form
factors calculated within the cloudy bag model. One of the assumptions of the
model is that electromagnetic form factors are most accurately evaluated in the
Breit frame. This feature is used to show that gauge invariance is respected in
this frame.


title: Nuclear Sizes and the Isotope Shift

abstract:
  Darwin-Foldy nuclear-size corrections in electronic atoms and nuclear radii
are discussed from the nuclear-physics perspective. Interpretation of precise
isotope-shift measurements is formalism dependent, and care must be exercised
in interpreting these results and those obtained from relativistic electron
scattering from nuclei. We strongly advocate that the entire nuclear-charge
operator be used in calculating nuclear-size corrections in atoms, rather than
relegating portions of it to the non-radiative recoil corrections. A
preliminary examination of the intrinsic deuteron radius obtained from
isotope-shift measurements suggests the presence of small meson-exchange
currents (exotic binding contributions of relativistic order) in the nuclear
charge operator, which contribute approximately 1/2%.


title:
Asymmetric Nuclear Matter in the Relativistic Brueckner Hartree Fock
  approach

abstract:
  We present a calculation of asymmetric nuclear matter properties in a
relativistic Brueckner Hartree Fock framework. Following other calculations the
components of the self-energies are extracted by projecting on Lorentz
invariant amplitudes. It is shown that for asymmetric nuclear matter one needs
a sixth invariant. We present a set of invariants which in the limit of
symmetric nuclear matter reduces to the conventional set. We argue that the
existence of such a properly behaving set is also crucial for the application
of the projection method in symmetric nuclear matter. Results for the equation
of state and other observables are presented. Special attention is payed to an
analysis in terms of mean-field effective coupling constants. Apart from the
usual ones we also find significant strength in the isovector scalar channel,
which can be interpreted as an effective $\delta$-meson.


title: Bremsstrahlung Pair Production In Relativistic Heavy Ion Collision

abstract:
  We calculate production of electron- and muon-pairs by the bremsstrahlung
process in hadron collisions and compare it with the dominant two-photon
process. Results for the total cross section are given for proton-proton and
heavy-ion collisions at energies of the Relativistic Heavy Ion Collider (RHIC)
and the Large Hadron Collider (LHC).


title: Radiative Muon Capture by a Proton in Chiral Perturbation Theory

abstract:
  The first measurement of the radiative muon capture (RMC) rate on a proton
was recently carried out at TRIUMF. The TRIUMF group analyzed the RMC rate in
terms of the theoretical formula of Beder and Fearing, and found the surprising
result that the pseudoscalar coupling g_P is 1.5 times the value expected from
PCAC. To assess the reliability of the theoretical framework used by the TRIUMF
group to relate the RMC rate to the pseudoscalar form factor, we calculate the
RMC rate in chiral perturbation theory, which provides a systematic framework
to describe all the vertices involved in RMC, fulfilling gauge-invariance and
chiral-symmetry requirements in a transparent manner. As a first step we
present a chiral perturbation calculation at tree level which includes
sub-leading order terms.


title: Chemical equilibration of strangeness

abstract:
  Thermal models are very useful in the understanding of particle production in
general and especially in the case of strangeness. We summarize the assumptions
which go into a thermal model calculation and which differ in the application
of various groups. We compare the different results to each other. Using our
own calculation we discuss the validity of the thermal model and the amount of
strangeness equilibration at CERN-SPS energies. Finally the implications of the
thermal analysis on the reaction dynamics are discussed.


title: Strangeness in ultrarelativistic nucleus-nucleus collisions

abstract:
  I discuss strangeness production in nucleus-nucleus reactions at
ultrarelativistic energies (up to 200 AGeV). In these reactions matter may be
created with densities and temperatures in the transition region between
quark-gluon plasma (QGP) and hadron gas. Strange anti-baryon enhancement at 200
AGeV and probably even more so at 10 AGeV signals importance of interactions
beyond hadron gas dynamics. The systematics of strangeness production indicates
that energy and baryon density are key variables while the size of the
production volume plays no visible role. Analysis of strangeness appears useful
to explore thermalization, flow and the post-equilibrium stage in
ultrarelativistic nucleus-nucleus collisions.


title: The quark-meson coupling model for Lambda, Sigma and Xi hypernuclei

abstract:
  The quark-meson coupling (QMC) model, which has been successfully used to
describe the properties of both infinite nuclear matter and finite nuclei, is
applied to a systematic study of $\Lambda, \Sigma$ and $\Xi$ hypernuclei.
Assumptions made in the present study are, (i) the (self-consistent) exchanged
scalar, and vector, mesons couple only to the u and d quarks, and (ii) an SU(6)
valence quark model for the bound nucleons and hyperon. The model automatically
leads to a very weak spin-orbit interaction for the $\Lambda$ in a
hypernucleus. Effects of the Pauli blocking at the quark level, particularly in
the open, coupled, $\Sigma N - \Lambda N$ channel (strong conversion), is also
taken into account in a phenomenological way.


title:
Nucleon-nucleon scattering observables from solitary boson exchange
  potential

abstract:
  The one solitary boson exchange potential (OSBEP) is used to evaluate
observables of NN elastic scattering below pion threshold. In this approach, we
use a nonlinear model of self-interacting mesons as a substitution for the
commonly used phenomenological form factors. NN data support an empirical
scaling law between the pion and other meson fields, which suggests a link to
QCD and significantly reduces the number of parameters in the boson exchange
potential. The analysis of np and pp observables distinguishes the model by its
fit and few adjustable parameters. An outlook to apply OSBEP in pi-N systems is
given.


title:
A Note on the Toda Criterion for Interacting Dipole-Quadrupole
  Vibrations

abstract:
  The Toda criterion of the Gaussian curvature is applied to calculate
analytically the transition energy from regular to chaotic motion in a
schematic model describing the interaction between collective dipole and
quadrupole modes in atomic nuclei.


title: Strangeness Photoproduction with the Saphir Detector

abstract:
  Statistically improved data of total cross sections and of angular
distributions for differential cross sections and hyperon recoil polarizations
of the reactions \gamma p --> K^+ \Lambda and \gamma p --> K^+ \Sigma^0 have
been collected with the SAPHIR detector at photon energies between threshold
and 2.0 GeV. Here total cross section data up to 1.5 GeV are presented. The
opposite sign of \Lambda and \Sigma polarization and the change of sign between
forward and backward direction could be confirmed by higher statistics. A steep
threshold behaviour of the K^+ \Lambda total cross section is observed.


title:
Effect of large neutron excess on the dipole response in the region of
  the Giant Dipole Resonance

abstract:
  The evolution of the Dipole Response in nuclei with strong neutron excess is
studied in the Hartree-Fock plus Random Phase Approximation with Skyrme forces.
We find that the neutron excess increases the fragmentation of the isovector
Giant Dipole Resonance, while pushing the centroid of the distribution to lower
energies beyond the mass dependence predicted by the collective models. The
radial separation of proton and neutron densities associated with a large
neutron excess leads to non vanishing isoscalar transition densities to the GDR
states, which are therefore predicted to be excited also by isoscalar nuclear
probes. The evolution of the isoscalar compression dipole mode as a function of
the neutron excess is finally studied. We find that the large neutron excess
leads to a strong concentration of the strength associated with the isoscalar
dipole operator $\sum_ir^3_iY_{10}$, that mainly originates from uncorrelated
excitations of the neutrons of the skin.


title:
Total and Parity-Projected Level Densities of Iron-Region Nuclei in the
  Auxiliary Fields Monte Carlo Shell Model

abstract:
  We use the auxiliary-fields Monte Carlo method for the shell model in the
complete $(pf+0g_{9/2})$-shell to calculate level densities. We introduce
parity projection techniques which enable us to calculate the parity dependence
of the level density. Results are presented for $^{56}$Fe, where the calculated
total level density is found to be in remarkable agreement with the
experimental level density. The parity-projected densities are well described
by a backshifted Bethe formula, but with significant dependence of the
single-particle level-density and backshift parameters on parity. We compare
our exact results with those of the thermal Hartree-Fock approximation.


title: Constraining the (gamma,pi) amplitude for E2 N->delta

abstract:
  A recent analysis of pion photo-production multipoles using p(g,pi0) data
from Mainz is repeated, successively adding constraints from other observables
and varying the number of fitted partial waves. The original analysis is shown
to have been underconstrained and suffered from ambiguities. The inclusion of
additional observables in our analysis results in a very different, but stable,
ratio of E2/M1 multipoles at the delta that is consistent with the Mainz data
set.


title:
The reactions $pp\to pp\pi^0$ and $pp\to d\pi^+$ at threshold: The role
  of the isoscalar $\pi N$ scattering amplitude

abstract:
  We examine the role of the elementary isoscalar pion--nucleon scattering
amplitude in the description of the processes $pp \to pp\pi^0$ and $pp\to
d\pi^+$ at threshold. We argue that the presently used tree level dimension two
approximation used in chiral perturbation theory is insufficient as input by
direct comparison with the $\pi$N scattering data. We also show that a
successful semi--phenomenological boson--exchange model does better in the
description of these data. The influence of the violation of crossing symmetry
in the meson--exchange model has to be studied in more detail. We stress that
further investigations of the process $pp\to d\pi^+$ can pave the way to a
deeper understanding of the pion dominated part of the transition operator.


title: New Results on Quantum Chaos in Atomic Nuclei

abstract:
  In atomic nuclei, ordered and chaotic states generally coexist. In this paper
the transition from ordered to chaotic states will be discussed in the
framework of roto-vibrational and shell models. In particular for $^{160}Gd$,
in the roto-vibrational model, the Poincar\`e sections clearly show the
transition from order to chaos for different values of rotational frequency.
Furthermore, the spectral statistics of low-lying states of several $fp$ shell
nuclei are studied with realistic shell-model calculations.


title: Multi-scattering effects in (e,e'p) knockout

abstract:
  Multistep direct scattering of the ejectile proton is considered in (e,e'p)
reactions in the quasi-free region as an improvement over the usual treatment
of final-state interactions by means of an optical potential. The theory is
applied to 40Ca(e,e'p) as a case example. Important contributions of two- and
three-step processes are found at high missing energy and momentum in agreement
with the experimental trend.


title:
Bremsstrahlung of 350--450 MeV protons as a tool to study $NN$
  interaction off-shell

abstract:
  The $pp\to pp\gamma$ bremsstrahlung cross section is calculated within the
method of coordinate space representation. It is shown that in the beam energy
range of 350--450~MeV a deep attractive NN-potential with forbidden states
(Moscow potential) and realistic meson exchange potentials (MEP) give rise to
the cross sections that differ essentially in shape: the cross sections nearly
coincide in the minima but differ by a factor of 5 approximately in the maxima.
Therefore, the $pp\to pp\gamma$ reaction at energies $\sim$350--450~Mev can be
used to study $NN$ interaction off-shell and to discriminate experimentally
between MEP and Moscow potential.


title:
Effects of gluon damping rate on the viscosity coefficient of the
  quark-gluon plasma at finite chemical potential

abstract:
  By considering the Debye screening and damping rate of gluons, the viscosity
coefficient of the quark-gluon plasma was evaluated via real-time finite
temperature QCD in the relaxation time approximation at finite temperature and
chemical potential . The results show that both the damping rate and the
chemical potential cause considerable enhancements to the viscosity coefficient
of hot dense quark-gluon plasma.


title: Quantum Transition from Order to Chaos in the Nuclear Shell Model

abstract:
  We discuss the role of quantum chaos in atomic nuclei. After reviewing the
basic assumptions of the nuclear shell model, we analyze the spectral
statistics of the energy levels obtained with realistic shell-model
calculations in the fp shell. In particular, for Ca isotopes we observe a
transition from order to chaos by increasing the excitation energy and a clear
quantum signature of the breaking of integrability by changing the
single-particle spacings.


title:
Quantum Signature of the Chaos-Order Transition in a Homogeneous SU(2)
  Yang-Mills-Higgs System

abstract:
  We analyze a spatially homogeneous SU(2) Yang-Mills-Higgs system both in
classical and quantum mechanics. By using the Toda criterion of the Gaussian
curvature we find a classical chaos-order transition as a function of the Higgs
vacuum, the Yang-Mills coupling constant and the energy of the system. Then, we
study the nearest-neighbour spacing distribution of the energy levels, which
shows a Wigner-Poisson transition by increasing the value of the Higgs field in
the vacuum. This transition is a clear quantum signature of the classical
chaos-order transition of the system.


title: The Phase in Three-Pion Correlations

abstract:
  We discuss the complex phase generated in three pion correlation functions.
The lowest order contribution to the phase is of order $q^2 R/K$, where $q$ is
a typical relative momentum, $K$ is a typical center of mass momentum and $R$
is a typical radius parameter. This contribution is of purely kinematic origin.
At next order we find a generic contribution of order $(qR)^3$ which is a
result of odd modifications to the source emission function. We argue, that the
scale for typical HBT correlations in ultrarelativistic heavy ion collisions is
$q/K \ll qR \sim 1$, so that the third order correction actually dominates the
phase in the experimentally relevant momentum range. We study in detail such
contributions which arise from source asymmetries generated by flow, the source
geometry and resonance decays.


title:
The Perturbed Static Path Approximation at Finite Temperature:
  Observables and Strength Functions

abstract:
  We present an approximation scheme for calculating observables and strength
functions of finite fermionic systems at finite temperature such as hot nuclei.
The approach is formulated within the framework of the Hubbard-Stratonovich
transformation and goes beyond the static path approximation and the RPA by
taking into account small amplitude time-dependent fluctuations around each
static value of the auxiliary fields. We show that this perturbed static path
approach can be used systematically to obtain good approximations for
observable expectation values and for low moments of the strength function. The
approximation for the strength function itself, extracted by an analytic
continuation from the imaginary-time response function, is not always reliable,
and we discuss the origin of the discrepancies and possible improvements. Our
results are tested in a solvable many-body model.


title: Charge-Exchange and multi-scattering effects in (e,e'n) knockout

abstract:
  Final-state interactions in (e,e'n) knockout reactions in the quasi-free
region are studied by considering the multistep direct scattering of the
ejectile nucleon. Primary and multiple particle emission are included within
the same model and are found to become important with increasing excitation
energy. Charge-exchange effects taken into account through the two-step
(e,e'p)(p,n) and three-step (e,e'p)(p,N)(N,n) processes are also found to
increase with energy. A comparison with the results obtained with an
isospin-dependent optical potential at small excitation energies is presented.


title:
Hybrid stars : Spin polarised nuclear matter and density dependent quark
  masses

abstract:
  The possibility of formation of a droplet phase (DP) inside a star and its
consequences on the structural properties of the star are investigated. For
nuclear matter (NM), an equation of state (EOS) based on finite range, momentum
and density dependent interaction, and which predicts that neutron matter
undergoes ferromagnetic transition at densities realisable inside the neutron
star is employed. An EOS for quark matter (QM) with density dependent quark
masses, the so-called effective mass model, is constructed by correctly
treating the quark chemical potentials. It is then found that a droplet phase
consisting of strange quark matter and unpolarised nuclear matter sandwiched
between a core of polarised nuclear matter and a crust containing unpolarised
nuclear matter exists. Moreover, we could explain the mass and surface magnetic
field satisfactorily, and as well allow, due to the presence of a droplet
phase, the direct URCA process to happen.


title: Color Transparency - Color Coherent Effects in Nuclear Physics

abstract:
  Efforts to observe color transparency in the reactions: (e,e'p), (p,pp) and
coherent nuclear diffractive dissociation of pions into two jets are reviewed.


title:
Sum rules for isospin centroids in pick-up reactions on general
  multishell target states

abstract:
  Sum Rules equations for pick-up reactions are presented for the first time
for the energy centroids of states both for the isospin T_< (\equiv T_0 - 1
\over 2) and T_> (\equiv T_0 + {1 \over 2}) of the final nucleus when a nucleon
is picked up from a general multishell target state with isospin T_0. These
equations contain two-body correlation terms, <H^{01}>, which, at the present
moment, are difficult to handle analytically. These terms are managed by
combining these equations with the known stripping reactions equations. Sample
applications of these equations to experimental data are presented.


title:
What Can We Learn from Transverse Momentum Spectra in Relativistic Heavy
  Ion Collisions?

abstract:
  We compare the predictions of different models for transverse momentum
spectra in relativistic heavy ion collisions. Particular emphasis is given to
hydrodynamic flow with different assumptions for the radial expansion, and to
models based on a superposition of fireballs along the transverse direction
(random walk). It is shown that present experimental data cannot distinguish
between the models under consideration.


title: Nuclear Breakup of Borromean Nuclei

abstract:
  We study the eikonal model for the nuclear-induced breakup of Borromean
nuclei, using Li11 and He6 as examples. The full eikonal model is difficult to
realize because of six-dimensional integrals, but a number of simplifying
approximations are found to be accurate. The integrated diffractive and
one-nucleon stripping cross sections are rather insensitive to the
neutron-neutron correlation, but the two-nucleon stripping does show some
dependence on the correlation. The distribution of excitation energy in the
neutron-core final state in one-neutron stripping reactions is quite sensitive
to the shell structure of the halo wave function. Experimental data favor
models with comparable amounts of s- and p-wave in the Li11 halo.


title: On the possibility of eta-mesic nucleus formation

abstract:
  A microscopic treatment of eta-nucleus system is presented. Using this, the
poles of the amplitude describing elastic scattering of eta-meson off the light
nuclei ^2H, ^3H, ^3He, and ^4He have been located in the second quadrant of the
complex plane of the eta-nucleus relative momentum. The results obtained
indicate that, within the existing uncertainties in the eta-Nucleon input data,
a bound state could exist. By a qualitative consideration it is shown that such
bound-states, cannot be narrow. It is further shown that scattering length
calculations cannot provide a definite answer on the question concerning the
existence of eta-nucleus bound states.


title:
Relativistic Effects and the Role of Heavy Meson Exchange in Deuteron
  Photodisintegration

abstract:
  Relativistic effects and the role of heavy meson exchange in deuteron
photodisintegration are studied systematically for photon energies below the
pion production threshold. In a (p/M)-expansion, all leading order relativistic
one-body and pi-exchange as well as all static heavy meson exchange currents
consistent with the Bonn OBEPQ model are included. In addition, one- and
two-body boost effects have been investigated. Sizeable effects from the
various two-body contributions beyond pi-exchange have been found in almost
every observable considered, i.e., differential cross section and single
polarization observables.


title: Two-particle interferometry for non-central heavy-ion collisions

abstract:
  In non-central heavy ion collisions, identical two particle
Hanbury-Brown/Twiss (HBT) correlations C(K,q) depend on the azimuthal direction
of the pair momentum K. We investigate the consequences for a harmonic analysis
of the corresponding HBT radius parameters. Our discussion includes both, a
model- independent analysis of these parameters in the Gaussian approximation,
and the study of a class of hydrodynamical models which mimic essential
geometrical and dynamical properties of peripheral heavy ion collisions. Also,
we discuss the additional geometrical and dynamical information contained in
the harmonic coefficients of these HBT radius parameters. The leading
contribution of their first and second harmonics are found to satisfy simple
constraints. This allows for a minimal, azimuthally sensitive parametrization
of all first and second harmonic coefficients in terms of only two additional
fit parameters. We determine to what extent these parameters can be extracted
from experimental data despite finite multiplicity fluctuations and the
resulting uncertainty in the reconstruction of the reaction plane.


title: Probing proton halos through pion photoproduction

abstract:
  Charged pion photoproduction is proposed as a new method to study halo
nuclei. In particular, it is demonstrated that the reaction
17O(gamma,pi^-)17F(1/2+, 0.495 MeV) is well-suited to investigate the
well-known proton halo in 17F which is not amenable to radioactive beam
experiments. The cross sections are shown to be very sensitive to the halo
structure of the loosely bound proton.


title: How dense does parton matter get in Pb + Pb Collisions at the CERN SPS?

abstract:
  We examine the qualitative features of parton production through
materialization in heavy-ion collisions within perturbative QCD, and estimate
the magnitude of the resulting parton density created during the early stage of
the collisions. The implications for ``anomalous'' $J/\psi$ suppression
observed in Pb+Pb collisions at the CERN SPS are discussed. We argue that the
A-dependence of absorption of $J/\psi$ by (partonic) comovers is steeper than
assumed in most phenomenological models, because the absorption process is
dominated by quasi-perturbative QCD interactions. Our argument is supported by
results recently obtained in the framework of the parton cascade model. We
predict significant ``anomalous'' suppression for Pb+Pb collisions at the
CERN-SPS, but not for S+U collisions.


title: Theoretical Aspects of Science with Radioactive Nuclear Beams

abstract:
  Physics of radioactive nuclear beams is one of the main frontiers of nuclear
science today. Experimentally, thanks to technological developments, we are on
the verge of invading the territory of extreme N/Z ratios in an unprecedented
way. Theoretically, nuclear exotica represent a formidable challenge for the
nuclear many-body theories and their power to predict nuclear properties in
nuclear terra incognita. It is important to remember that the lesson learned by
going to the limits of the nuclear binding is also important for normal nuclei
from the neighborhood of the beta stability valley. And, of course, radioactive
nuclei are crucial astrophysically; they pave the highway along which the
nuclear material is transported up in the proton and neutron numbers during the
complicated synthesis process in stars.


title: Constraining the $(\gamma, \pi)$ amplitudes for E2 $N \to \Delta$

abstract:
  We reply to the Comment of A.M. Sandorfi et al. [nucl-th/9707028] on the
E2/M1 ratio from the Mainz photoproduction data, nucl-th/9707028 v2. We support
our published result for the E2/M1 ratio of REM
  = -(2.5 +- 0.2 +- 0.2)%.


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

abstract:
  We study the finite temperature properties of an effective chiral Lagrangian
which describes nuclear matter. Thermal fluctuations in both the nucleon and
the meson fields are considered. The logarithmic and square root terms in the
effective potential are evaluated by expansion and resummation with the result
written in terms of the exponential integral and the error function,
respectively. In the absence of explicit chiral symmetry breaking a phase
transition restores the symmetry, but when the pion has a mass the transition
is smooth. The nucleon and meson masses as a functions of density and
temperature are discussed.


title: Gamow-Teller strength distributions in fp-shell nuclei

abstract:
  We use the shell model Monte Carlo method to calculate complete 0f1p-shell
response functions for Gamow-Teller (GT) operators and obtain the corresponding
strength distributions using a Maximum Entropy technique. The approach is
validated against direct diagonalization for 48Ti. Calculated GT strength
distributions agree well with data from (n,p) and (p,n) reactions for nuclei
with A=48-64. We also calculate the temperature evolution of the GT+
distributions for representative nuclei and find that the GT+ distributions
broaden and the centroids shift to lower energies with increasing temperature.


title:
SMMC studies of N=Z pf-shell nuclei with pairing-plus-quadrupole
  Hamiltonian

abstract:
  We perform Shell Model Monte Carlo calculations of selected N=Z pf-shell
nuclei with a schematic hamiltonian containing isovector pairing and
quadrupole-quadrupole interactions. Compared to realistic interactions, this
hamiltonian does not give rise to the SMMC ``sign problem'', while at the same
time resembles essential features of the realistic interactions. We study
pairing correlations in the ground states of N=Z nuclei and investigate the
thermal dependence of selected observables for the odd-odd nucleus Co54 and the
even-even nuclei Zn60 and Ni60. Comparison of the present results to those with
the realistic KB3 interaction indicates a transition with increasing
temperature from a phase of isovector pairing dominance to one where isoscalar
pairing correlations dominate. In addition, our results confirm the qualitative
reliability of the procedure used to cure the sign problem in the SMMC
calculations with realistic forces.


title: High-density nuclear matter with nonlocal confining solitons

abstract:
  An infinite system of nonlocal, individually confining solitons is considered
as a model of high-density nuclear matter. The soliton-lattice problem is
discussed in the Wigner-Seitz approximation. The cell size is varied to study
the density dependence of physical quantities of interest. A transition to a
system where quarks can migrate between solitons is found. We argue that this
signals quark deconfinement. The model is applied to the calculation of
selected in-medium properties.


title:
In-medium omega-meson broadening and S-wave pion annihilation into
  e^+e^- pairs

abstract:
  An $\omega$-meson in motion with respect to a nuclear medium can couple to a
$\sigma$-meson through a particle-hole excitation. This coupling is large. We
investigate its consequences for the width of $\omega$-mesons in matter and for
the s-wave annihilation of pions into lepton pairs which can take place in
relativistic heavy ion collisions. We find that the two pion decay of
$\omega$-mesons, resulting from the $\omega-\sigma$ transition and the
subsequent $2\pi$ decay of the $\sigma$-meson, leads to a substantial
broadening of $\omega$-mesons in matter and possibly to an observable effect in
experiments measuring the $e^+e^-$ decay of vector mesons produced in nuclei
and in relativistic heavy-ion collisions. The inverse process, the s-wave
annihilation of pions into $\omega$-mesons decaying into $e^+e^-$ pairs, has in
general a much smaller cross section than the corresponding p-wave annihilation
through $\rho$-mesons and is expected to contribute rather little to the total
$e^+e^-$ pair production in relativistic heavy ion collisions.


title:
Computations of scattering lengths in nnpp system within cluster
  reduction method for Yakubovsky equations

abstract:
  Scattering lengths for d-d, n-$^3$He and p-$^3$H systems are computed via
Cluster Reduction Method for Yakubovsky equations in configuration space taking
into account Coulomb interaction between protons. MT I-III potential model was
used to describe the nucleon-nucleon interaction. Results of calculations are
in a good agreement with existing experimental data and results of calculations
of other authors.


title: Effective interactions and shell model studies of heavy tin isotopes

abstract:
  We calculate the low-lying spectra of heavy tin isotopes from A=120 to A=130
using the 2s1d0g_{7/2}0h_{11/2} shell to define the model space. An effective
interaction has been derived using 132Sn as closed core employing perturbative
many-body techniques. We start from a nucleon-nucleon potential derived from
modern meson exchange models. This potential is in turn renormalized for the
given medium, 132Sn, yielding the nuclear reaction matrix, which is then used
in perturbation theory to obtain the shell model effective interaction.


title: HBT with Space- vs. Time-like Hydrodynamic Freezeout

abstract:
  Bose-Einstein correlations in relativistic heavy ion collisions and their
dependence on the freeze-out condition in hydrodynamic models is compared to
time-like freeze-out, where particles are emitted away only from the surface,
i.e. space- vs. time-like freeze-out. The corresponding HBT radii are
calculated for the two models emphasizing the difference in the outward HBT
radius.


title: Lagrangian with off-shell vertices and field redefinitions

abstract:
  Meson exchange diagrams following from a lagrangian with off-shell
meson-nucleon couplings are compared with those generated from conventional
dynamics. The off-shell interactions can be transformed away with the help of a
nucleon field redefinition. Contributions to to the $NN$- and $3N$-potentials
and nonminimal contact e.m. meson-exchange currents are discussed, mostly for
an important case of scalar meson exchange. (pacs 11.10.Lm, 13.75.Cs, 21.30.-x,
24.10.Jv)


title:
Deuteron -- $\alpha$ interaction by inversion of RGM S-matrix:
  determination of spin-orbit potential for spin-1 projectile

abstract:
  The iterative-perturbative (IP) procedure for S-matrix to potential inversion
is applied to spin-one projectiles for the restricted case of vector spin-orbit
interaction only. In order to evaluate this extension of IP inversion we have
inverted the multi-channel RGM $S_{lj}$ of Kanada et al for deuterons
scattering from $^4$He with deuteron distortion and then compared the central
components with those derived from RGM with spin set to zero. Attention is
given to the question of how well the resulting potentials are established.
Reliable spin-1 inversion is demonstrated. Results relating to inversion, to
deuteron-nucleus interactions and to RGM are presented and suggest the range of
nuclear interaction information which the procedure makes possible. Unusual
non-locality and parity dependence effects are found; these are of possible
relevance to generic properties of nuclear potentials.


title: The Spectral Function of the Rho Meson in Nuclear Matter

abstract:
  We calculate the modification of a rho meson in nuclear matter through its
coupling to resonance-hole states. Starting from a recently proposed model, we
include all four star resonances up to 1.9 GeV. In contrast to previous works,
we include not only resonances that couple to the rho in a relative p-wave, but
also those that couple to an s-wave state. In addition, we solve the equation
for the rho spectral function self-consistently. We find that s-wave resonances
affect the in medium spectral function of the rho strongly. In the transverse
channel the rho meson is, especially at non zero momentum, completely washed
out and can in the presence of nuclear matter no longer be viewed as a resonant
excitation of the vacuum. Instead, our model shows a continuum of possible
excitations with the quantum numbers of a transversely polarized rho. In the
longitudinal channel, however, the rho retains its resonant character in our
calculation. As a consequence of the self-consistent treatment we also find a
strong enhancement of the widths of the included nucleon resonances in medium.


title:
On the extraction of electromagnetic properties of the Delta(1232)
  excitation from pion photoproduction

abstract:
  Several methods for the treatment of pion photoproduction in the region of
the Delta(1232) resonance are discussed, in particular the effective Lagrangian
approach and the speed plot analysis are compared to a dynamical treatment. As
a main topic, we discuss the extraction of the genuine resonance parts of the
magnetic dipole and electric quadrupole multipoles of the electromagnetic
excitation of the resonance. To this end, we try to relate the various values
for the ratio R_{EM} of the E2 to M1 multipole excitation strengths for the
Delta(1232) resonance as extracted by the different methods to corresponding
ratios of a dynamical model. Moreover, it is confirmed that all methods for
extracting resonance properties suffer from an unitary ambiguity which is due
to some phenomenological contributions entering the models.


title: Analysis of Pion Photoproduction over the Delta Resonance Region

abstract:
  A number of recent multipole analyses from Mainz, RPI, BNL and Virginia Tech
(VPI) have focused on the first resonance region. One goal common to these
studies was an improved set of Delta(1232) photo-decay amplitudes. There has
been considerable debate over the differing results found for A(1/2), A(3/2)
and the E2/M1 ratio. We show that a much more consistent set of values is
possible if differences in the database are considered.


title: Estimating the nuclear level density with the Monte Carlo shell model

abstract:
  A method for making realistic estimates of the density of levels in even-even
nuclei is presented making use of the Monte Carlo shell model (MCSM). The
procedure follows three basic steps: (1) computation of the thermal energy with
the MCSM, (2) evaluation of the partition function by integrating the thermal
energy, and (3) evaluating the level density by performing the inverse Laplace
transform of the partition function using Maximum Entropy reconstruction
techniques. It is found that results obtained with schematic interactions,
which do not have a sign problem in the MCSM, compare well with realistic
shell-model interactions provided an important isospin dependence is accounted
for.


title:
Energy Dependence of Breakup Cross Sections of Halo Nucleus 8B and
  Effective Interactions

abstract:
  We study the energy dependence of the cross sections for nucleon removal of
8B projectiles. It is shown that the Glauber model calculations with
nucleon-nucleon t-matrix reproduce well the energy dependence of the breakup
cross sections of 8B. A DWBA model for the breakup cross section is also
proposed and results are compared with those of the Glauber model. We show that
to obtain an agreement between the DWBA calculations, the Glauber formalism,
and the experimental data, it is necessary to modify the energy behavior of the
effective interaction. In particular, the breakup potential has a quite
different energy dependence than the strong absorption potential.


title:
The role of the quantum dispersion in the Coulomb correction of
  Bose-Einstein correlations

abstract:
  The time dependent Schroedinger equation for two identical and charged pions
is solved using wavepacket states. It is shown that the expected Coulomb
distortion in the momentum correlation function is obliterated by the
dispersion of the localized states, and therefore becomes unobservable.


title:
Energy Dependence of the NN t-matrix in the Optical Potential for
  Elastic Nucleon-Nucleus Scattering

abstract:
  The influence of the energy dependence of the free NN t-matrix on the optical
potential of nucleon-nucleus elastic scattering is investigated within the
context of a full-folding model based on the impulse approximation. The
treatment of the pole structure of the NN t-matrix, which has to be taken into
account when integrating to negative energies is described in detail. We
calculate proton-nucleus elastic scattering observables for $^{16}$O,
$^{40}$Ca, and $^{208}$Pb between 65 and 200 MeV laboratory energy and study
the effect of the energy dependence of the NN t-matrix. We compare this result
with experiment and with calculations where the center-of-mass energy of the NN
t-matrix is fixed at half the projectile energy. It is found that around 200
MeV the fixed energy approximation is a very good representation of the full
calculation, however deviations occur when going to lower energies (65 MeV).


title: Dihyperon in Chiral Colour Dielectric Model

abstract:
  The mass of dihyperon with spin, parity $J^{\pi}=0^{+}$ and isospin $I = 0$
is calculated in the framework of Chiral colour dielectric model. The wave
function of the dihyperon is expressed as a product of two colour-singlet
baryon clusters. Thus the quark wave functions within the cluster are
antisymmetric. Appropriate operators are then used to antisymmetrize
inter-cluster quark wave functions. The radial part of the quark wavefunctions
are obtained by solving the the quark and dielectric field equations of motion
obtained in the Colour dielectric model. The mass of the dihyperon is computed
by including the colour magnetic energy as well as the energy due to meson
interaction. The recoil correction to the dihyperon mass is incorporated by
Peierls-Yoccoz technique. We find that the mass of the dihyperon is smaller
than the $\Lambda-\Lambda$ threshold by over 100 MeV. The implications of our
results on the present day relativistic heavy ion experiments is discussed.


title: Photoproduction of the Hypertriton

abstract:
  In the framework of the impulse approximation we study the photoproduction of
the hypertriton $^3_{\Lambda}$H by using realistic $^3$He wave functions
obtained as solutions of Faddeev equations with the Reid soft-core potential
for different $^3_{\Lambda}$H wave functions. We obtain relatively small cross
sections of the order of 1 nb. We also find that the influence of Fermi motion
is important, while the effect of different off-shell assumptions on the cross
section is not too significant.


title:
Antisymmetry and channel coupling contributions to the absorption for p
  + alpha/d + 3He

abstract:
  To understand recently established empirical p + alpha potentials, RGM
calculations followed by inversion are made to study contributions of the d +
3He reaction channels and deuteron distortion effects to the p + alpha
potential. An equivalent study of the d + 3He potential is also presented. The
contributions of exchange non-locality to the absorption are simulated by
including an phenomenological imaginary potential in the RGM. These effects
alone strongly influence the shape of the imaginary potentials for both p +
alpha and d + 3He. The potentials local-equivalent to the fully
antisymmetrised-coupled channels calculations have a significant
parity-dependence in both real and imaginary components, which for p + alpha is
qualitatively similar to that found empirically. The effects on the potentials
of the further inclusion of deuteron distortion are also presented. The
inclusion of a spin-orbit term in the RGM, adds additional terms to the
phase-equivalent potential, most notably the comparatively large imaginary
spin-orbit term found empirically.


title: Analysis of the pp-->pp, pid-->pid, and pid-->pp Scattering Data

abstract:
  A combined analysis of the main reactions of the two-baryon system (pp-->pp,
pid-->pid, and pid-->pp) over the sqrt{s} interval from pion threshold to 2.4
GeV has been completed. The overall phase in pid-->pp has now been determined.
The combined analysis has resulted in an improved fit to the pid elastic and
pid-->pp databases.


title: Nucleon-Nucleon Partial Wave Analysis to 2.5 GeV

abstract:
  A partial-wave analysis of NN elastic scattering data has been completed.
This analysis covers an expanded energy range, from threshold to a laboratory
kinetic energy of 2.5 GeV, in order to include recent elastic pp scattering
data produced by the EDDA collaboration at COSY. The results of both
single-energy and energy-dependent analyses are described.


title: What QCD sum rules tell about the rho meson

abstract:
  Using a simple parametrization of Breit-Wigner type for the hadronic side of
the QCD sum rule for $\rho$ mesons in vacuum as well as in a nuclear medium we
explore the range of values for the mass and the width of the $\rho$ meson
which are compatible with the operator product expansion.


title:
Two-Body T-Matrices without Angular Momentum Decomposition: Energy and
  Momentum Dependencies

abstract:
  The two-body t-matrix is calculated directly as function of two vector
momenta for different Malfliet-Tjon type potentials. At a few hundred MeV
projectile energy the total amplitude is quite a smooth function showing only a
strong peak in forward direction. In contrast the corresponding partial wave
contributions, whose number increases with increasing energy, become more and
more oscillatory with increasing energy. The angular and momentum dependence of
the full amplitude is studied and displayed on as well as off the energy shell
as function of positive and negative energies. The behavior of the t-matrix in
the vicinity of bound state poles and resonance poles in the second energy
sheet is studied. It is found that the angular dependence of T exhibits a very
characteristic behavior in the vicinity of those poles, which is given by the
Legendre function corresponding to the quantum number either of the bound state
or the resonance (or virtual) state. This behavior is illustrated with
numerical examples.


title: The Skyrme Energy Functional and Naturalness

abstract:
  Recent studies show that successful relativistic mean-field models of nuclei
are consistent with naive dimensional analysis and naturalness, as expected in
low-energy effective field theories of quantum chromodynamics. The
nonrelativistic Skyrme energy functional is found to have similar
characteristics.


title: On electromagnetic off-shell effects in proton-proton bremsstrahlung

abstract:
  We study the influence of the off-shell structure of the nucleon
electromagnetic vertex on proton-proton bremsstrahlung observables. Realistic
choices for these off-shell effects are found to have considerable influences
on observables such as cross sections and analyzing powers. The rescattering
contribution diminishes the effects of off-shell modifications in
negative-energy states.


title:
Probing the Rho Spectral Function in Hot and Dense Nuclear Matter by
  Dileptons

abstract:
  We present a dynamical study of $e^+e^-$ and $\mu^+ \mu^-$ production in
proton-nucleus and nucleus-nucleus collisions at CERN-SPS energies on the basis
of the covariant transport approach HSD employing a momentum-dependent
$\rho$-meson spectral function that includes the pion modifications in the
nuclear medium as well as the polarization of the $\rho$-meson due to resonant
$\rho$$-N$ scattering. We find that the experimental data from the CERES and
HELIOS-3 Collaborations can be described equally well as within the dropping
$\rho$-mass scenario. Whereas corresponding dilepton $q_T$-spectra are found to
be very similar, the inclusive dilepton yield in the invariant mass range $0.85
\leq M \leq 1.0$ GeV should allow to disentangle the two scenarios
experimentally.


title: Computations of Three-Body Continuum Spectra

abstract:
  We formulate a method to solve the coordinate space Faddeev equations for
positive energies. The method employs hyperspherical coordinates and analytical
expressions for the effective potentials at large distances. Realistic
computations of the parameters of the resonances and the strength functions are
carried out for the Borromean halo nucleus 6He (n+n+alpha) for J = 0+, 0-, 1+,
1-, 2+,2-. PACS numbers: 21.45.+v, 11.80.Jy, 31.15.Ja, 21.60.Gx


title: Randomly Broken Nuclei and Disordered Systems

abstract:
  Similarities between models of fragmenting nuclei and disordered systems in
condensed matter suggest corresponding methods. Several theoretical models of
fragmentation investigated in this fashion show marked differences, indicating
possible new methods for distinguishing models using yield data. Applying
nuclear methods to disordered systems also yields interesting results.


title: Universal aspects of Efimov states and light halo nuclei

abstract:
  The parametric region in the plane defined by the ratios of the energies of
the subsystems and the three body ground state, in which Efimov states can
exist, is determined. We use a renormalizable model that guarantees the general
validity of our results in the context of short range interactions. The
experimental data for one and two-neutron separation energies, implies that
among the halo-nuclei candidates, only C-20 has a possible Efimov state, with
energy less than 14 KeV below the scattering threshold.


title: S-matrix studies of resonances in A=3,4,5,6, and 12 nucleon systems

abstract:
  Resonances of certain light nuclei are explored by studying the complex pole
structures of the scattering matrices. Among other results we predict the
existence of three-neutron and three-proton resonances, a small spin-orbit
splitting in the low-lying He-5 and Li-5 states and the nonexistence of the
soft dipole resonance in He-6.


title:
Spectra of produced particles at CERN SPS heavy-ion collisions from a
  parton-cascade model

abstract:
  We evaluate the spectra of produced particles (pions, kaons, antiprotons)
from partonic cascades which may develop in the wake of heavy-ion collisions at
CERN SPS energies and which may hadronize by formation of clusters which decay
into hadrons. Using the experimental data obtained by NA35 and NA44
collaborations for S+S and Pb+Pb collisions, we conclude that the Monte Carlo
implementation of the recently developed parton-cascade/cluster-hadronization
model provides a reasonable description of the distributions of the particles
produced in such collisions. While the rapidity distribution of the
mid-rapidity protons is described reasonably well, their transverse momentum
distribution falls too rapidly compared to the experimental values, implying a
significant effect of final state scattering among the produced hadrons
neglected so far.


title:
Nucleon-Nucleon Phase Shifts and Pairing in Neutron Matter and Nuclear
  Matter

abstract:
  We consider 1S0 pairing in infinite neutron matter and nuclear matter and
show that in the lowest order approximation, where the pairing interaction is
taken to be the bare nucleon-nucleon (NN) interaction in the 1S0 channel, the
pairing interaction and the energy gap can be determined directly from the 1S0
phase shifts. This is due to the almost separable character of the NN
interaction in this partial wave. Since the most recent NN interactions are
charge-dependent, we have to solve coupled gap equations for proton-proton,
neutron-neutron, and neutron-proton pairing in nuclear matter. The results,
however, are found to be close to those obtained with charge-independent
potentials.


title:
A covariant gauge-invariant three-dimensional description of
  relativistic bound-states

abstract:
  A formalism is presented which allows covariant three-dimensional bound-state
equations to be derived systematically from four-dimensional ones without the
use of delta-functions. The amplitude for the interaction of a bound state
described by these equations with an electromagnetic probe is constructed. This
amplitude is shown to be gauge invariant if the formalism is truncated at the
same coupling-constant order in both the interaction kernel of the integral
equation and the electromagnetic current operator.


title: High-Energy Nuclear Physics with Lorentz Symmetry Violation

abstract:
  If textbook Lorentz invariance is actually a property of the equations
describing a sector of the excitations of vacuum above some critical distance
scale, several sectors of matter with different critical speeds in vacuum can
coexist and an absolute rest frame (the vacuum rest frame) may exist without
contradicting the apparent Lorentz invariance felt by "ordinary" particles
(particles with critical speed in vacuum equal to $c$, the speed of light).
Sectorial Lorentz invariance, reflected by the fact that all particles of a
given dynamical sector have the same critical speed in vacuum, will then be an
expression of a fundamental sectorial symmetry (e.g. preonic grand unification
or extended supersymmetry) protecting a parameter of the equations of motion.
Furthermore, the sectorial Lorentz symmetry may be only a low-energy limit, in
the same way as the relation $\omega $ (frequency) = $c_s$ (speed of sound) $k$
(wave vector) holds for low-energy phonons in a crystal. In this context,
phenomena such as the absence of Greisen-Zatsepin-Kuzmin cutoff for protons and
nuclei and the stability of unstable particles (e.g. neutron, several
nuclei...) at very high energy are basic properties of a wide class of
noncausal models where local Lorentz invariance is broken introducing a
fundamental length. Observable phenomena are expected at very short wavelength
scales, even if Lorentz symmetry violation remains invisible to standard
low-energy tests. We present a detailed discussion of the implications of
Lorentz symmetry violation for very high-energy nuclear physics.


title: pi- and K-meson Bethe-Salpeter Amplitudes

abstract:
  Independent of assumptions about the form of the quark-quark scattering
kernel, K, we derive the explicit relation between the flavour-nonsinglet
pseudoscalar meson Bethe-Salpeter amplitude, Gamma_H, and the dressed-quark
propagator in the chiral limit. In addition to a term proportional to gamma_5,
Gamma_H necessarily contains qualitatively and quantitatively important terms
proportional to gamma_5 gamma.P and gamma_5 gamma.k k.P, where P is the total
momentum of the bound state. The axial-vector vertex contains a bound state
pole described by Gamma_H, whose residue is the leptonic decay constant for the
bound state. The pseudoscalar vertex also contains such a bound state pole and,
in the chiral limit, the residue of this pole is related to the vacuum quark
condensate. The axial-vector Ward-Takahashi identity relates these pole
residues; with the Gell-Mann--Oakes-Renner relation a corollary of this
identity. The dominant ultraviolet asymptotic behaviour of the scalar functions
in the meson Bethe-Salpeter amplitude is fully determined by the behaviour of
the chiral limit quark mass function, and is characteristic of the QCD
renormalisation group. The rainbow-ladder Ansatz for K, with a simple model for
the dressed-quark-quark interaction, is used to illustrate and elucidate these
general results. The model preserves the one-loop renormalisation group
structure of QCD. The numerical studies also provide a means of exploring
procedures for solving the Bethe-Salpeter equation without a three-dimensional
reduction.


title:
A large Hilbert space QRPA and RQRPA calculation of neutrinoless double
  beta decay

abstract:
  A large Hilbert space is used for the calculation of the nuclear matrix
elements governing the light neutrino mass mediated mode of neutrinoless double
beta decay of Ge76, Mo100, Cd116, Te128 and Xe136 within the proton-neutron
quasiparticle random phase approximation (pn-QRPA) and the renormalized QRPA
with proton-neutron pairing (full-RQRPA) methods. We have found that the
nuclear matrix elements obtained with the standard pn-QRPA for several nuclear
transitions are extremely sensitive to the renormalization of the
particle-particle component of the residual interaction of the nuclear
hamiltonian. Therefore the standard pn-QRPA does not guarantee the necessary
accuracy to allow us to extract a reliable limit on the effective neutrino
mass. This behaviour, already known from the calculation of the two-neutrino
double beta decay matrix elements, manifests itself in the neutrinoless
double-beta decay but only if a large model space is used. The full-RQRPA,
which takes into account proton-neutron pairing and considers the Pauli
principle in an approximate way, offers a stable solution in the physically
acceptable region of the particle-particle strength. In this way more accurate
values on the effective neutrino mass have been deduced from the experimental
lower limits of the half-lifes of neutrinoless double beta decay.


title: Integrability of the pairing hamiltonian

abstract:
  We show that a many-body Hamiltonian that corresponds to a system of fermions
interacting through a pairing force is an integrable problem, i.e. it has as
many constants of the motion as degrees of freedom. At the classical level this
implies that the Time-dependent Hartree-Fock- Bogoliubov dynamics is integrable
and at the quantum level that there are conserved operators of two-body
character which reduce to the number operators when the pairing strength
vanishes. We display these operators explicitly and study in detail the
three-level example.

categories: nucl-th chao-dyn nlin.CD nlin.SI solv-int


title: Large-basis shell-model calculation of 10C->10B Fermi matrix element

abstract:
  We use a $4\hbar\Omega$ shell-model calculation with a two-body effective
interaction derived microscopically from the Reid93 potential to calculate the
isospin-mixing correction for the 10C->10B superallowed Fermi transition. The
effective interaction takes into account the Coulomb potential as well as the
charge dependence of T=1 partial waves. Our results suggest the isospin- mixing
correction $\delta_{C}\approx 0.1 %$, which is compatible with previous
calculations. The correction obtained in those calculations, performed in a
$0\hbar\Omega$ space, was dominated by deviation from unity of the radial
overlap between the converted proton and the corresponding neutron. In the
present calculation this effect is accommodated by the large model space. The
obtained $\delta_{C}$ correction is about a factor of four too small to obtain
unitarity of the Cabibbo-Kobayashi-Maskawa matrix with the present experimental
data.


title: Fluctuation and Dissipation in Classical Many-Particle Systems

abstract:
  Coarse-grained Langevin-type effective field equations are derived for
classical systems of particles. These equations include the effects of thermal
fluctuation and dissipation which may arise from coupling to an external bath,
as in the Brownian motion of a single particle, or which may arise from
statistical fluctuations in small parts of an isolated many-particle system, as
in sound waves. These equations may provide some guidance for the analysis of
mesoscopic or microscopic molecular systems, or for systems of hundreds to
thousands of subatomic particles produced in high energy nuclear collisions.


title: The Continuum Structure of the Borromean Halo Nucleus 11Li

abstract:
  We solve the Faddeev equations for 11Li (n+n+9Li) using hyperspherical
coordinates and analytical expressions for distances much larger than the
effective ranges of the interactions. The lowest resonances are found at 0.65
MeV (1/2+, 3/2+, 5/2+) and 0.89 MeV (3/2+, 3/2-) with widths of about 0.35 MeV.
A number of higher-lying broader resonances are also obtained and related to
the Efimov effect. The dipole strength function and the Coulomb dissociation
cross section are also calculated. PACS numbers: 21.45.+v, 11.80.Jy, 21.60.Gx


title:
The isoscalar S-wave pi-N scattering length a+ from pi-deuteron
  scattering

abstract:
  We consider constraints on the isoscalar S-wave pi-N scattering length a+
from pi-deuteron scattering, to third order in small momenta and pion masses in
chiral perturbation theory. To this order, the pi-deuteron scattering length is
determined by a+ together with three-body corrections that involve no
undetermined parameters. We extract a novel value for a combination of
dimension two low-energy constants which is in agreement with previous
determinations.


title: Quantum Tunneling in Nuclear Fusion

abstract:
  Recent theoretical advances in the study of heavy ion fusion reactions below
the Coulomb barrier are reviewed. Particular emphasis is given to new ways of
analyzing data, such as studying barrier distributions; new approaches to
channel coupling, such as the path integral and Green function formalisms; and
alternative methods to describe nuclear structure effects, such as those using
the Interacting Boson Model. The roles of nucleon transfer, asymmetry effects,
higher-order couplings, and shape-phase transitions are elucidated. The current
status of the fusion of unstable nuclei and very massive systems are briefly
discussed.


title: Role of retardation in 3-D relativistic equations

abstract:
  Equal-time Green's function is used to derive a three-dimensional integral
equation from the Bethe-Salpeter equation. The resultant equation, in the
absence of anti-particles, is identical to the use of time-ordered diagrams,
and has been used within the framework of $\phi^2\sigma$ coupling to study the
role of energy dependence and non-locality when the two-body potential is the
sum of $\sigma$-exchange and crossed $\sigma$ exchange. The results show that
non-locality and energy dependence make a substantial contribution to both the
on-shell and off-shell amplitudes.


title: pi-pi Scattering and the Meson Resonance Spectrum

abstract:
  A pi-pi, Kbar-K, and rho-rho(omega-omega) fully coupled channel model is used
to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities
for elastic pi-pi scattering from threshold to 2.0 GeV. As input the S-matrix
is required to exhibit poles corresponding to the meson resonance table of the
Particle Data Group. As expected, the pi-pi inelasticity is very strongly
related to the opening of the Kbar-K channel near 1 GeV, and the opening of
rho-rho(4pi) and omega-omega(6pi) channels in the 1.5 GeV region. The
predictions of this model are compared to the various elastic pi-pi to pi-pi
amplitudes, that were obtained from analyses of pi(-) p to pi(-) pi(+) n data.
The role of the various resonances, in particular the glueball candidate
f_0(1500) and the f_J(1710) is investigated.


title:
Shell Model Monte Carlo studies of neutron-rich nuclei in the
  1s-0d-1p-0f shells

abstract:
  We demonstrate the feasibility of realistic Shell-Model Monte Carlo (SMMC)
calculations spanning multiple major shells, using a realistic interaction
whose bad saturation and shell properties have been corrected by a newly
developed general prescription. Particular attention is paid to the approximate
restoration of translational invariance. The model space consists of the full
sd-pf shells. We include in the study some well-known T=0 nuclei and several
unstable neutron-rich ones around N=20,28. The results indicate that SMMC can
reproduce binding energies, B(E2) transitions, and other observables with an
interaction that is practically parameter free. Some interesting insight is
gained on the nature of deep correlations. The validity of previous studies is
confirmed.


title: Relativistic Point-Coupling Models as Effective Theories of Nuclei

abstract:
  Recent studies have shown that concepts of effective field theory such as
naturalness can be profitably applied to relativistic mean-field models of
nuclei. Here the analysis by Friar, Madland, and Lynn of naturalness in a
relativistic point-coupling model is extended. Fits to experimental nuclear
data support naive dimensional analysis as a useful principle and imply a
mean-field expansion analogous to that found for mean-field meson models.


title:
Non-mesonic Weak Decays of Light Hypernuclei in the Direct Quark and the
  One-Pion Exchange Mechanisms

abstract:
  Contributions of the direct quark mechanism are studied in the nonmesonic
weak decays of light hypernuclei. The $\Lambda N \to NN$ transition is
described by the one pion exchange mechanism and the direct quark mechanism,
induced by the four-quark vertices in the effective weak Hamiltonian. By
employing a realistic wave function of the $\Lambda$ inside the hypernuclei,
nonmesonic decay rates of $^4_{\Lambda}$H, $^4_{\Lambda}$He, and
$^5_{\Lambda}$He are calculated. The results show that the direct quark
mechanism is significantly large and gives a large $\Delta I =3/2$ contribution
in the J=0 channel. The relative phase between the one-pion exchange and the
direct-quark contributions is determined so that the effective weak Hamiltonian
for quarks give both of them consistently. We find that the sum of these two
contributions reproduce the current available experimental data fairly well.


title: f_K/f_pi ratio from QCD sum rules

abstract:
  Using the correlation function of the axial vector mesons, we present a QCD
sum rule calculation for the decay constants f_pi and f_K. Our calculations are
only weakly dependent on the SU(3) breaking-parameter for the QCD vacuum and
give the ratio f_K/f_pi = 1.11 $\pm$ 0.02.


title: The semi-classical approach to the exclusive electron scattering

abstract:
  The semiclassical approach, successfully applied in the past to the
inelastic, inclusive electron scattering off nuclei, is extended to the
treatment of exclusive processes. The final states interaction is accounted for
in the mean field approximation, respecting the Pauli principle. The impact on
the exclusive cross section of the shape of the potential binding the nucleons
into the nucleus and of the distortion of the outgoing nucleon wave are
explored. The exclusive scattering is found to be quite sensitive to the mean
field final states interaction, unlike the inclusive one. Indeed we verify that
the latter is not affected, as implied by unitarity, by the distortion of the
outgoing nucleon wave except for the effect of relativity, which is modest in
the range of momenta up to about 500 MeV/c. Furthermore, depending upon the
correlations between the directions of the outgoing and of the initial nucleon,
the exclusive cross-section turns out to be remarkably sensitive to the shape
of the potential binding the nucleons. These correlations also critically
affect the domain in the missing energy-- missing momentum plane where the
exclusive process occurs.


title:
Relative space-time asymmetries in pion and nucleon production in
  non-central nucleus-nucleus collisions at high energies

abstract:
  We propose to use the ratio of the pion-proton correlation functions
evaluated under different conditions to study the relative space-time
asymmetries in pion and proton emission (pion and nucleon source relative
shifts) in high energy heavy ion collision. We address the question of the
non-central collisions, where the sources can be shifted spatially both in the
longitudinal and in the transverse directions in the reaction plane. We use the
RQMD event generator to illustrate the effect and the technique.


title: Chiral Limit of Nuclear Physics

abstract:
  We study nuclear physics in the chiral limit ($m_u$, $m_d=0$) in which the
pion mass vanishes. We find that the deuteron mass is changed little, but that
P--wave nucleon--nucleon scattering volumes are infinite. This motivates an
investigation of the possibilities that there could be a two--nucleon $^3P_0$
bound state, and that the nuclear matter ground state is likely to be a
condensed state of nucleons paired to those quantum numbers. However, the short
distance repulsion in the nucleon--nucleon potential is not affected by the
chiral limit and prevents such new chiral possibilities. Thus the chiral limit
physics of nuclei is very similar to that of nature. Using the chiral limit to
simplify QCD sum rule calculations of nuclear matter properties seems to be a
reasonable approximation.


title: Pion-Nucleon Scattering in the Infinite Momentum Frame

abstract:
  A light front field theory treatment of a chiral lagrangian is applied to
pion-nucleon and nucleon-nucleon scattering.


title:
Role of isospin dependent mean field in pion production in heavy ion
  reactions

abstract:
  The importance of a isospin dependent nuclear mean field (IDMF) in regard to
the pion production mechanism is studied for the reaction $Au+Au$ at 1
GeV/nucleon using the Quantum Molecular Dynamics (QMD) model. In particular,
the effect of the IDMF on pion spectra and the charged pion ratio are analyzed.
It is found that the inclusion of a IDMF considerably suppresses the low$-p_t$
pions, thus, leading to a better agreement with the data on pion spectra.
Moreover, the rapidity distribution of the charged pion ratio appears to be
sensitive to the isospin dependence of the nuclear mean field.


title: New Baryons in the Delta eta and Delta omega Channels

abstract:
  The decays of excited nonstrange baryons into the final states Delta eta and
Delta omega are examined in a relativized quark pair creation model. The
wavefunctions and parameters of the model are fixed by previous calculations of
N pi and N pi pi, etc., decays through various quasi-two body channels
including N eta and N omega. Our results show that the combination of
thresholds just below the region of interest and the isospin selectivity of
these channels should allow the discovery of several new baryons in such
experiments.


title: The Weak $\Lambda \Lambda K^0$ Interaction

abstract:
  We calculate the leading contribution to the weak $\Lambda \Lambda K$
coupling in heavy baryon chiral perturbation theory, including the SU(3)
breaking terms arising at one-loop. This coupling gives the leading one-boson
exchange amplitude for the process $\Lambda\Lambda\to\Lambda n$ and is an
important component in understanding the decay of $\Lambda\Lambda$-hypernuclei.
We find the S-wave and P-wave amplitudes to be stable under one-loop
corrections, but the associated errors become large. We discuss the theoretical
errors and potential effects of higher order terms.


title: The Skyrmion in the nucleus

abstract:
  The energy levels of a skyrmion in nucleus are calculated in a field theory
of skyrmions coupled to the dilaton field and the $\omega$ meson . The central
potential fits well with expectations. The nucleon spin-orbit interaction
derived from the omega meson in a rotating frame gives the correct level
splittings. The same interaction originating from the Thomas precession effect
is negligible. Energy levels are calculated for closed shell nuclei. The meson
fields are obtained from a Thomas-Fermi mean field approximation to the
nucleus.


title: A unitary model for meson-nucleon scattering

abstract:
  In an effective Lagrangian model employing the K-matrix approximation we
extract nucleon resonance parameters. To this end we analyze simultaneously all
available data for reactions involving the final states $\pi N$, $\pi\pi N$,
$\eta N$ and $K \Lambda$ in the energy range $m_N + m_{\pi} \le \sqrt s \le
1.9$ GeV. The background contributions are generated consistently from the
relevant Feynman amplitudes, thus significantly reducing the number of free
parameters.


title: Spectrum generating algebra of the symmetric top

abstract:
  We consider an algebraic treatment of a three-body system. We develop the
formalism for a system of three identical objects and show that it provides a
simultaneous description of the vibrational and rotational excitations of an
oblate symmetric top.


title:
Classical Gluon Radiation in Ultrarelativistic Nuclear Collisions:
  Space-Time Structure, Instabilities, and Thermalization

abstract:
  We investigate the space-time structure of the classical gluon field produced
in an ultrarelativistic collision between color charges. The classical solution
which was computed previously in a perturbative approach is shown to become
unstable on account of the non-Abelian self-interaction neglected in the
perturbative solution scheme. The time scale for growth of the instabilities is
found to be of the order of the distance between the colliding color charges.
We argue that these instabilities will eventually lead to thermalization of
gluons produced in an ultrarelativistic collision between heavy nuclei. The
rate of thermalization is estimated to be of order $g^2 \mu$, where $g$ is the
strong coupling constant and $\mu^2$ the transverse color charge density of an
ultrarelativistic nucleus.


title: Pion Cloud Contributions to the Proton's Weak Magnetic Form Factor

abstract:
  We report on the contributions to the nucleon weak magnetic and electric form
factors arising from isospin-breaking form factors. The relativized quark model
used in the calculations includes isospin impurities in the large basis nucleon
wavefunctions and uses constituent quark currents with both Pauli and Dirac
components. Significant contributions are found to arise from the Pauli
component when it is interpreted as arising from pion-baryon loops. Including
these pion cloud contributions reduces the strange magnetic form factor
extracted from the recent SAMPLE measurement of the proton's weak neutral
magnetic form factor at low Q^2 by 35 to 52%.


title: Transverse Energy production in Ultrarelativistic Heavy Ion Collisions

abstract:
  Kinetic theory is used to check the applicability of parton cascade in 1
dimensional expansion. Using the information provided by 3 dimensional parton
cascade, we model the transverse expansion by an effective area. With this
model, kinetic theory is able to give prediction of the time development of
transverse energy which is in good agreement with the parton cascade results.


title:
Pionic decay of a possible d'-dibaryon and the short-range NN
  interaction

abstract:
  We study the pionic decay of a possible dibaryon d' --> N N \pi in the
microscopic quark shell model. The initial d' dibaryon wave function (J^P=0^-,
T=0) consists of one 1\hbar\omega six-quark shell-model s^5p[51]_X
configuration. The most important final six-quark configurations s^6[6]_X,
s^4p^2[42]_X and (s^4p^2-s^52s)[6]_X are properly projected onto the NN
channel. The final state NN interaction is investigated by means of two
phase-equivalent - but off-shell different - potential models. We demonstrate
that the decay width \Gamma_d' depends strongly on the short-range behavior of
the NN wave function. In addition, the width \Gamma_d' is very sensitive to the
mass and size of the d' dibaryon.
  For dibaryon masses slightly above the experimentally suggested value
M_d'=2.065 GeV, we obtain a pionic decay width of \Gamma_d' = 0.18 - 0.32 MeV
close to the experimental value \Gamma_d' = 0.5 MeV.


title: The d'-dibaryon in a colored cluster model

abstract:
  We calculate the mass and structure of a J^P=0^-, T=0 six-quark system using
a colored diquark-tetraquark cluster wave function and a nonrelativistic quark
model Hamiltonian. The calculated mass is some 350 MeV above the empirical
value if the same confinement strength as in the nucleon is used. If the
effective two-body confinement strength is weaker in a compound six-quark
system than in a single baryon, as expected from a simple harmonic oscillator
model, one obtains M_d' = 2092 MeV close to experiment.


title: Electromagnetic Spectrum from QGP Fluid

abstract:
  We calculate thermal photon and electron pair distribution from hot QCD
matter produced in high energy heavy-ion collisions, based on a hydrodynamical
model which is so tuned as to reproduce the recent experimental data at CERN
SPS, and compare these electromagnetic spectra with experimental data given by
CERN WA80 and CERES. We investigate mainly the effects of the off-shell
properties of the source particles on the electromagnetic spectra.


title:
Chaos modified wall formula damping of the surface motion of a cavity
  undergoing fissionlike shape evolutions

abstract:
  The chaos weighted wall formula developed earlier for systems with partially
chaotic single particle motion is applied to large amplitude collective motions
similar to those in nuclear fission. Considering an ideal gas in a cavity
undergoing fission-like shape evolutions, the irreversible energy transfer to
the gas is dynamically calculated and compared with the prediction of the chaos
weighted wall formula. We conclude that the chaos weighted wall formula
provides a fairly accurate description of one body dissipation in dynamical
systems similar to fissioning nuclei. We also find a qualitative similarity
between the phenomenological friction in nuclear fission and the chaos weighted
wall formula. This provides further evidence for one body nature of the
dissipative force acting in a fissioning nucleus.


title: Chiral Symmetry and Meson-Exchange Currents

abstract:
  The meson-exchange current in nuclei, a long-standing problem in nuclear
physics, is described in modern theory of strong interactions, namely, QCD
expressed in terms of effective chiral Lagrangian field theory. Some old
results are given a modern interpretation and some new results are predicted.
Among the topics treated are an accurate calculation of the radiative np
capture process at thermal energy, the enhanced axial charge transition in
heavy nuclei, Brown-Rho (BR) scaling in dense medium induced by vacuum changes,
dropping meson masses and "mended symmetry" in relativistic heavy-ion processes
and the link between the physics of dilute and dense hadronic systems through a
mapping of effective chiral Lagrangians to Landau Fermi-liquid theory.


title: Nambu-Jona-Lasinio Model at the Next-to-Leading Order in 1/N

abstract:
  We derived and solved the compositeness condition in the Nambu-Jona-Lasinio
model at the next-to-leading order in 1/N, and obtained the expressions for the
effective coupling constants in terms of the compositeness scale. In the NJL
model with a scalar composite, the next to leading contributions are too large
for N=3. In the induced gauge theory with abelian gauge symmetry, the
correction term is reasonably suppressed, while, in the SU(N_c) gauge theory
with N_f flavors of fermions, the correction is suppressed only for
N_f>11N_c/2, complementarily to asymptotic freedom.


title:
The $\lambda\Lambda$ interaction and the reaction $\Xi^- + d \to n +
  \Lambda + \Lambda$

abstract:
  The $\Lambda\Lambda$ interaction resulting from the SU(3) rotation of the
S-wave component of the Nijmegen OBE potential $D$ is used to calculate the
binding energy of $^{ 6}_{\Lambda\Lambda}$He as a $\Lambda\Lambda\alpha$
three-body system, and the neutron differential energy spectrum for the
reaction $\Xi^- + d \to n + \Lambda + \Lambda$.


title: $^{6}_{\Lambda\Lambda}$He as a $\Lambda\Lambda$ interaction constraint

abstract:
  The Nijmegen OBE potential D is SU(3) rotated to model the strangeness -2
sector of the baryon-baryon force. Soft core repulsion is introduced to
regularize the singular nature of the OBE functions. The strength of the
$^1$S$_0$ $t=0$ interaction is adjusted to model three scenarios: (1) a bound
state, (2) a narrow virtual, or antibound, state, and (3) an unbound state in
which the force is weakly attractive. Using a separable approximation to these
potentials, the binding energy of $^{6}_{\Lambda\Lambda}$He is calculated in an
$\Lambda\Lambda\alpha$ model. The resultant binding energies suggest that the
strength of the $^1$S$_0$ $t=0$ $\Lambda\Lambda$ and the $nn$ interactions
should be similar, if the coupling between the $\Lambda\Lambda$ and $\Xi N$
channels is taken into consideration.


title:
Space-time Evolution of Quark-Gluon Plasma Fluid with First Order Phase
  Transition

abstract:
  We numerically solve the (3+1)-dimensional relativistic hydrodynamical
equation with a bag-model equation of state, which is one of the simplest
models for the first order phase transition. Based on the numerical solution,
we discuss the space-time evolution of the hot fluid produced in ultra
relativistic nuclear collisions. Especially, the space-time structure of the
two-phase co-existing region during the quark-gluon plasma-hadron phase
transition is analyzed in detail. Finally, we investigate the change of the
mass spectra of $J/\psi$, ${\eta}_{c}$ and ${\phi}$ as possible experimental
signatures of the phase transition.


title:
N N bar,Delta bar N, Delta N bar excitation for the pion propagator in
  nuclear matter

abstract:
  The particle-hole and Delta -hole excitations are well-known elementary
excitation modes for the pion propagator in nuclear matter. But, the excitation
also involves antiparticles, namely, nucleon-antinucleon, anti-Delta-nucleon
and Delta-antinucleon excitations. These are important for high-energy momentum
as well, and have not been studied before, to our knowledge. In this paper, we
give both the formulas and the numerical calculations for the real and the
imaginary parts of these excitations.


title: Study of odd-mass N=82 isotones with realistic effective interactions

abstract:
  The microscopic quasiparticle-phonon model, MQPM, is used to study the energy
spectra of the odd $Z=53 - 63$, N=82 isotones. The results are compared with
experimental data, with the extreme quasiparticle-phonon limit and with the
results of an unrestricted $2s1d0g_{7/2}0h_{11/2}$ shell model (SM)
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 MQPM the
effective interaction is defined by the G-matrix.


title: Green's Function for Nonlocal Potentials

abstract:
  The single-particle nuclear potential is intrinsically nonlocal. In this
paper, we consider nonlocalities which arise from the many-body and fermionic
nature of the nucleus. We investigate the effects of nonlocality in the nuclear
potential by developing the Green's function for nonlocal potentials. The
formal Green's function integral is solved analytically in two different limits
of the wavelength as compared to the scale of nonlocality. Both results are
studied in a quasi-free limit. The results illuminate some of the basic effects
of nonlocality in the nuclear medium.


title:
A Microscopic Calculation of Photoabsorption Cross Sections on Protons
  and Nuclei

abstract:
  A recently developed model for $\rho$-meson propagation in dense hadronic
matter is applied to total photoabsorption cross sections in $\gamma$-proton
and $\gamma$-nucleus reactions. Within the vector dominance model the photon
coupling to the virtual pion cloud of the nucleon, two-body meson-exchange
currents, as well as $\gamma$-nucleon resonances are included. Whereas the
$\gamma p$ reaction is determined by the low-density limit of the model, higher
orders in the nuclear density are important to correctly account for the
experimental spectra observed on both light and heavy nuclei over a wide range
of photon energies, including the region below the pion threshold. In
connection with soft dilepton spectra in high-energy heavy-ion collisions we
emphasize the importance of photoabsorption to further constrain the parameters
of the model.


title: ZPC 1.0.1: a parton cascade for ultrarelativistic heavy ion collisions

abstract:
  A Monte Carlo program solving Boltzmann equation for partons via cascade
method is presented. At presented, only gluon-gluon elastic scattering is
included. The scattering cross section is regulated by a medium generated
screening mass. Three different geometric modes (3 dimension expansion, 1-d
expansion, and scattering inside a box) are provided for theoretical study of
the parton transport and the applicability of the cascade method. Space cell
division is available to save the number of computer operations. This improves
the speed of the calculation by a large factor and makes the code best
optimized for simulation of parton cascade in ultrarelativistic heavy ion
collisions.


title: HBT Effect Based on a Hydrodynamical Model

abstract:
  We investigate HBT radii based on the numerical solutions of the
hydrodynamical model which are so tuned as to reproduce the recent experimental
data at the CERN SPS. Comparing the sizes of freeze-out hypersurface with HBT
radii, we discuss dynamical effect of the systematic flow on the apparent HBT
radii. Finally we compare HBT radii of the QGP phase transition model with
those of the hadron gas model without phase transition.


title:
Regular and chaotic dynamics in time-dependent 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 theory. Time-dependent and self-consistent calculations
that reproduce experimental data on monopole resonances in 208Pb, show that the
motion of the collective coordinate is regular for isoscalar oscillations, and
that it becomes chaotic when initial conditions correspond to the isovector
mode. Regular collective dynamics coexists with chaotic oscillations on the
microscopic level. Time histories, Fourier spectra, state-space plots, Poincare
sections, autocorrelation functions, and Lyapunov exponents are used to
characterize the nonlinear system and to identify chaotic oscillations.
Analogous considerations apply to higher multipolarities.


title:
Relativistic Brueckner-Hartree-Fock calculations with explicit
  intermediate negative energy states

abstract:
  In a relativistic Brueckner-Hartree-Fock calculation we include explicit
negative-energy states in the two-body propagator. This is achieved by using
the Gross spectator-equation, modified by medium effects. Qualitatively our
results compare well with other RBHF calculations. In some details significant
differences occur, e.g, our equation of state is stiffer and the momentum
dependence of the self-energy components is stronger than found in a reference
calculation without intermediate negative energy states.


title: S-wave Pairing of $\Lambda$ Hyperons in Dense Matter

abstract:
  In this work we calculate the $^1S_0$ gap energies of $\Lambda$ hyperons in
neutron star matter. The calculation is based on a solution of the BCS gap
equation for an effective G-matrix parameterization of the $\Lambda-\Lambda$
interaction with a nuclear matter background, presented recently by Lanskoy and
Yamamoto. We find that a gap energy of a few tenths of MeV is expected for
$\Lambda$ Fermi momenta up to about 1.3 fm$^{-1}$. Implications for neutron
star matter are examined, and suggest the existence of a $\Lambda$ $^1S_0$
superfluid between the threshold baryon density for $\Lambda$ formation and the
baryon density where the $\Lambda$ fraction reaches $15-20%$.


title: Cascade-Exciton Model Analysis of Proton Spallation from 10 MeV to 5 GeV

abstract:
  We have used an extended version of the Cascade-Exciton Model (CEM) to
analyze more than 600 excitation functions for proton induced reactions on 19
targets ranging from C-12 to Au-197, for incident energies ranging from 10 MeV
to 5 GeV. We have compared the calculations to available data, to calculations
using approximately two dozen other models, and to predictions of several
phenomenological systematics. We present here our conclusions concerning the
relative roles of different reaction mechanisms in the production of specific
final nuclides. We comment on the strengths and weaknesses of the CEM and
suggest possible further improvements to the CEM and to other models.


title: Nucleon and nuclear spin structure functions

abstract:
  Nuclear effects in polarized inelastic electron scattering off polarized
$^3He$ and polarized $^2H$ are discussed; in the resonance region, Fermi motion
effects are found to be much larger than in deep inelastic scattering. It is
shown that improperly describing nuclear dynamics would lead to the extraction
of unreliable neutron spin structure functions; on the other hand side, simple
and workable equations, relating the Gerasimov -- Drell -- Hearn Integral for
the neutron to the corresponding quantity for $^3He$ and $^2H$, are proposed.
Nuclear effects in the recent E143 data are estimated by a proper procedure.


title: Stability and Production of Superheavy Nuclei

abstract:
  Beyond uranium heavy elements rapidly become increasingly unstable with
respect to spontaneous fission as the proton number Z increases, because of the
disruptive effect of the long-range Coulomb force. However, in the region just
beyond Z = 100 magic proton and neutron numbers and the associated shell
structure enhances nuclear stability sufficiently to allow observation of
additional nuclei. Some thirty years ago it was speculated that an island of
spherical, relatively stable superheavy nuclei would exist near the next doubly
magic proton-neutron combination beyond 208:Pb, that is, at proton number Z =
114 and neutron number N = 184. Theory and experiment now show that there also
exists a rock of stability in the vicinity of Z = 110 and N = 162 between the
actinide region, which previously was the end of the peninsula of known
elements, and the predicted island of spherical superheavy nuclei slightly
southwest of the magic numbers Z = 114 and N = 184. We review here the
stability properties of the heavy region of nuclei. Just as the decay
properties of nuclei in the heavy region depend strongly on shell structure,
this structure also dramatically affects the fusion entrance channel. The six
most recently discovered new elements were all formed in cold-fusion reactions.
We discuss here the effect of the doubly magic structure of the target in
cold-fusion reactions on the fusion barrier and on dissipation.


title: A relativistic dynamical model for pi-N scattering

abstract:
  We present a unitary relativistic quasi-potential model for describing the
low-energy pion-nucleon interaction, based on the equal time Bethe-Salpeter
equation. It preserves the covariant structure of a relativistic spin 1/2
particle for the nucleon propagator, to be contrasted to other quasi-potential
approximations.