title:
Microscopic analysis of quadrupole collective motion in Cr--Fe nuclei:
  II. Doorway nature of mixed-symmetry states

abstract:
  The mixed-symmetry collective modes are investigated in Cr-Fe nuclei, by
analyzing the realistic shell-model wavefunctions via the H^n-cooling method.
It is clarified that the relatively low-lying mixed-symmetry states behave like
doorway states. For these nearly spherical nuclei, the lowest mixed-symmetry
state is shown to have $J^P=2^+$. An indication of the mixed-symmetry 3^+ state
is obtained. The sequence of the mixed-symmetry 2^+, 1^+ and 3^+ levels and its
nucleus-dependence are discussed. Calculated M1 and M3 transitions in the
low-energy region suggest that the mixed-symmetry 1^+ and 3^+ components are
detectable. We investigate the B(M1) distribution in a wider energy range,
without breaking the isospin quantum number. It is confirmed that the
mixed-symmetry 1^+ component is well separated from the peak of the spin
excitation. The isospin-raising component has a peak, separated well from the
isospin-conserving one. The orbital angular-momentum contributes destructively
to the spin excitations.


title: Comment on ``Meson Masses in Nuclear Matter''

abstract:
  In a recent paper, Eletsky and Ioffe estimated the energy shift of
$\rho$-meson with high momentum (q) in nuclei using the Glauber approximation.
They also made remarks on the low q vector mesons in medium. In this Comment,
we will discuss the second point and show that (i) mean-field physics for the
mass shift of low-q mesons is overlooked in the paper, and (ii) the short
distant operator product expansion is relevant to analyze the low-q mesons in
QCD sum rules contrary to the claim in the paper.


title: Update of the pi N --> eta N and eta N --> eta N partial-wave amplitudes

abstract:
  A three-channel, multi-resonance, unitary model developed in 1995 is used to
determine the $\pi N \rightarrow \eta N$ and $\eta N \rightarrow \eta N$
amplitudes using as input the latest data for the dominant $S_{11}$ $\pi N$
elastic scattering partial wave following suggestions of Prof. G. H\"{o}hler.
The sign error in the numerical evaluation of the dispersion integral in the
original publication is eliminated. The remaining weighted data set for the
$\pi N \rightarrow \eta N$ total and differential cross sections is used as in
the original publication. The correction of the numerical error influences the
$\eta N$ cusp effect and improves the quality of the fit to the input data.
However, our new result for the $\eta N$ scattering length, $a_{\eta N }=
(0.717 \pm 0.030) + i (0.263 \pm 0.025)$ fm, is a sole consequence of the
correction of the $S_{11}$ input and suggests that the $\eta d$ system is
unbound or loosely bound.


title:
Self-Consistent Pushing and Cranking Corrections to the Meson Fields of
  the Chiral Quark-Loop Soliton

abstract:
  We study translational and spin-isospin symmetry restoration for the
two-flavor chiral quark-loop soliton. Instead of a static soliton at rest we
consider a boosted and rotating hedgehog soliton. Corrected classical meson
fields are obtained by minimizing a corrected energy functional which has been
derived by semi-classical methods ('variation after projection'). We evaluate
corrected meson fields in the region 300 MeV \le M \le 600 MeV of constituent
quark masses M and compare them with the uncorrected fields. We study the
effect of the corrections on various expectation values of nuclear observables
such as the root-mean square radius, the axial-vector coupling constant,
magnetic moments and the delta-nucleon mass splitting.


title: Pions in the nuclear medium and Drell-Yan scattering

abstract:
  We investigate the modification of the pion-cloud in the nuclear medium and
its effect on the nuclear Drell-Yan process. The pion's in-medium self-energy
is calculated in a self-consistent delta-hole model, with particle-hole
contribution also included. Both the imaginary and real part of the pion's and
delta's self-energy are taken into account and related through a dispersion
relation assuring causality. The resulting in-medium pion light-cone momentum
distribution shows only a slight enhancement compared to the one of the free
nucleon. As a consequence the ratio of the cross-section for Drell-Yan
scattering on nuclear matter and nucleonic target is close to unity in
agreement with experiment.


title: Caloric Curve for Finite Nuclei in Thomas-Fermi Theory

abstract:
  In a finite temperature Thomas-Fermi theory with realistic nuclear
interactions, we construct caloric curves for finite nuclei enclosed in a
sphere of about $4 - 8$ times the normal nuclear volume. The specific heat
capacity $C_v$ shows a peaked structure that is possibly indicative of a
liquid-gas phase transition in finite nuclear systems.


title: f [N pi N]: from quarks to the pion derivative coupling

abstract:
  We study the N pi N coupling, in the framework of a QCD-inspired confining
Nambu-Jona-Lasinio model. A simple relativistic confining and instantaneous
quark model is reviewed. The Salpeter equation for the nucleon and the boosted
pion is solved. The f [n pi n] and f[n pi Delta] couplings are calculated and
they turn out to be reasonably good. The sensibility of f[n pi n] and f[n pi
Delta] to confinement, chiral symmetry breaking and Lorentz invariance is
briefly discussed.


title:
Bethe-Salpeter equation: 3D reductions, heavy mass limits and abnormal
  solutions

abstract:
  We show that the 3D reductions of the Bethe-Salpeter equation have the same
bound state spectrum as the original equation, with the possible exception of
some solutions for which the corresponding 3D wave function vanishes. The
abnormal solutions of the Bethe-Salpeter equation (corresponding to excitations
in the relative time-energy degree of freedom), when they exist, are recovered
in the 3D reductions via a complicated dependence of the final potential on the
total energy. We know however that the one-body (or one high mass) limit of
some 3D reductions of the exact Bethe-Salpeter equation leads to a compact 3D
equation (by a mutual cancellation of the ladder and crossed graph
contributions), which does not exhibit this kind of dependence on the total
energy anymore. We conclude that the exact Bethe-Salpeter equation has no
abnormal solution at this limit, or has only solutions for which our 3D wave
function vanishes. This is in contrast with the results of the ladder
approximation, where no such cancellation occurs. We draw the same conclusions
for the static model, which we obtain by letting the mass of the lighter
particle go also to infinity. These results support Wick's conjecture that the
abnormal solutions are a spurious consequence of the ladder approximation.


title:
Role of anharmonicities of nuclear vibrations in fusion reactions at
  subbarrier energies

abstract:
  We discuss the effects of double octupole and quadrupole phonon excitations
in $^{144}$Sm on fusion reactions between $^{16}$O and $^{144}$Sm at subbarrier
energies. The effects of anharmonicities of the vibrational states are taken
into account by using the $sdf$-interacting boson model. We compare the results
with those in the harmonic limit to show that anharmonicities play an essential
role in reproducing the experimental fusion barrier distribution. From the
analysis of the high quality fusion data available for this system, we deduce
negative static quadrupole moments for both the first 2$^{+}$ and 3$^{-}$
states in $^{144}$Sm. This is the first time that the sign of static quadrupole
moments of phonon states in a spherical nucleus is determined from the data of
subbarrier fusion reactions.


title: Fluctuations and HBT Scales in Relativistic Nuclear Collisions

abstract:
  Bose-Einstein correlations in relativistic heavy ion collisions are examined
in a general model containing the essential features of hydrodynamical, cascade
as well as other models commonly employed for describing the particle
freeze-out. In particular the effects of longitudinal and transverse expansion,
emission from surfaces moving in time, the thickness of the emitting layer
varying from surface to volume emission and other effects are studied. Model
dependences of freeze-out sizes and times are discussed and compared to recent
$Pb+Pb$ data at 160A$\cdot$GeV.


title:
\pi\pi, K\pi and \pi N potential scattering and a prediction of a narrow
  \sigma meson resonance

abstract:
  Low energy scattering and bound state properties of the \pi N, \pi\pi and
K\pi systems are studied as coupled channel problems using inversion potentials
of phase shift data. In a first step we apply the potential model to explain
recent measurements of pionic hydrogen shift and width. Secondly, predictions
of the model for pionium lifetime and shift confirm a well known and widely
used effective range expression. Thirdly, as extension of this confirmation, we
predict an unexpected medium effect of the pionium lifetime which shortens by
several orders of magnitude. The \sigma meson shows a narrow resonance
structure as a function of the medium modified mass with the implication of
being essentially energy independent. Similarly, we see this medium resonance
effect realized for the K\pi system. To support our findings we present also
results for the \rho meson and the \Delta(1232) resonance.


title:
Nonequilibrium fluid-dynamics in the early stage of ultrarelativistic
  heavy-ion collisions

abstract:
  To describe ultrarelativistic heavy-ion collisions we construct a three-fluid
hydrodynamical model. In contrast to one-fluid hydrodynamics, it accounts for
the finite stopping power of nuclear matter, i.e. for nonequilibrium effects in
the early stage of the reaction. Within this model, we study baryon dynamics in
the BNL-AGS energy range. For the system Au+Au we find that kinetic equilibrium
between projectile and target nucleons is established only after a time
$t_{CM}^{eq}\approx 5~fm/c\simeq 2R_{Au}/\gamma_{CM}$. Observables which are
sensitive to the early stage of the collision (like e.g. nucleon flow)
therefore differ considerably from those calculated in the one-fluid model.


title:
Linear Extrapolation of Ultrarelativistic Nucleon-Nucleon Scattering to
  Nucleus-Nucleus Collisions

abstract:
  We use a Glauber-like approach to describe very energetic nucleus-nucleus
collisions as a sequence of binary nucleon-nucleon collisions. No free
parameters are needed: all the information comes from simple parametrizations
of nucleon-nucleon collision data. Produced mesons are assumed not to interact
with each other or with the original baryons. Comparisons are made to published
experimental measurements of baryon rapidity and transverse momentum
distributions, negative hadron rapidity and transverse momentum distributions,
average multiplicities of pions, kaons, hyperons, and antihyperons, and zero
degree energy distributions for sulfur-sulfur collisions at 200 GeV/c per
nucleon and for lead-lead collisions at 158 GeV/c per nucleon. Good agreement
is found except that the number of strange particles produced, especially
antihyperons, is too small compared with experiment. We call this model LEXUS:
it is a baseline linear extrapolation of ultrarelativistic nucleon-nucleon
scattering to heavy ion collisions.


title:
Symmetry energy of nuclear matter and properties of neutron statrs in a
  relativistic approach

abstract:
  Asymmetric nuclear matter is treated in the formalism of Dirac-Brueckner
approach with Bonn one-boson-exchange nucleon-nucleon interaction. We extract
the symmetry energy coefficient at the saturation to be about 31 MeV, which is
in good agreement with empirical value of $30\pm 4$ MeV. The symmetry energy is
found to increase almost linearly with the density, which differs considerably
from the results of non-relativistic approaches. This finding also supports the
linear parameterization of Prakash, Ainsworth and Lattimer. We find,
furthermore, that the higher-order dependence of the nuclear equation of state
on the asymmetry parameter is unimportant up to densities relevant for neutron
stars. The resulting equation of state of neutron-rich matter is used to
calculate the maximum mass of neutron star, and we find it to be about
2.1$M_\odot$. Possible mechanisms for the softening of the equation of state
are also discussed.


title:
Fermionic Molecular Dynamics: Multifragmentation in heavy-ion collisions
  and in excited nuclei

abstract:
  Within Fermionic Molecular Dynamics we investigate fragmentation of a
compound system which was created in a heavy-ion collision at a beam energy in
the Fermi energy domain and the decay of excited iron nuclei. We show that in
FMD many-body correlations play an important role in the formation of
fragments.


title: Parity violation in quasifree electron scattering off the deuteron

abstract:
  For deuteron electroweak disintegration, parity violating effects are
investigated which arise from the interference of $\gamma$ and $Z$ exchange as
well as from the hadronic sector via a small parity violating component in the
deuteron. The general formalism for the differential cross section and
polarization observables of electromagnetic deuteron disintegration is extended
to incorporate parity violating contributions. Formal expressions for the
additional structure functions are derived. Results are presented for these
parity violating structure functions for quasifree kinematics neglecting final
state interaction and two-body effects. Both types of parity violating
contributions to the asymmetry of the inclusive reaction with respect to
longitudinally polarized electrons are evaluated. The one from parity violating
deuteron components is negligible over the whole range of momentum transfers
considered.


title:
Unitarity constraint for threshold coherent pion photoproduction on the
  deuteron and chiral perturbation theory

abstract:
  The contribution of the two-step process gamma + d -> p + n -> pi0 + d to the
imaginary part of the amplitude for coherent pion production on the deuteron is
calculated exploiting unitarity constraints. The result shows that this
absorptive process is not negligible and has to be considered in an extraction
of the elementary neutron production amplitude from the gamma + d -> pi0 + d
cross section at threshold. In addition, it is argued that a consistent
calculation of gamma + d -> pi0 + d in baryon chiral perturbation theory beyond
next-to-leading order requires the inclusion of this absorptive process.


title:
Exploration of resonances by analytic continuation in the coupling
  constant

abstract:
  The energy and the width of resonance states are determined by analytic
continuation of bound-state energies as a function of the coupling constant
(potential strength). The advantage of the method is that the existing
techniques for calculation of bound states can be applied, without any
modifications, to determine the position of resonances. Various numerical
examples show the applicability of the method for three-body systems, including
the excited states of the $^6$He and $^6$Li.


title:
Collectivity Embedded in Complex Spectra: Example of Nuclear
  Double-Charge Exchange Modes

abstract:
  The mechanism of collectivity coexisting with chaos is investigated on the
quantum level. The complex spectra are represented in the basis of two-particle
two-hole states describing the nuclear double-charge exchange modes in
$^{48}$Ca. An example of $J^{\pi}=0^-$ excitations shows that the residual
interaction, which generically implies chaotic behavior, under certain specific
and well identified conditions may create transitions stronger than those
corresponding to the pure mean-field picture. Therefore, for this type of
excitations such an effect is not generic and in most cases the strength of
transitions is likely to take much lower values, even close to the
Porter-Thomas distributed.


title: Strangeness production and flow in heavy-ion collisions

abstract:
  We study strangeness (K^+, K^-, and Lambda) production and flow in Ni+Ni
collisions at 1-2 AGeV, based on the relativistic transport model including the
strangeness degrees of freedom. We find that strangeness spectra and flow are
sensitive to the properties of strange hadrons in nuclear medium. The
predictions of the chiral perturbation theory that the K^+ feels a weak
repulsive potential and K^- feels a strong attractive potential are in good
agreement with recent experimental data from FOPI and KaoS collaborations.


title:
Comment on "A Search for Narrow Sum Energy Lines in Electron-Positron
  Pair Emission from Heavy Ion collisions near the Coulomb Barrier"

abstract:
  The report of Ahmad et al., states that ``No evidence is found for sharp
peaks in the present data.'' But this statement is factually inaccurate. Figure
1 exhibits the APEX' published U + Th ``wedge cut'' data, and background, which
show a distinct (3.2 sigma) maximum of 83 excess pair counts in the 20 keV bin
near 790 keV. A one-gaussian best fit to this excess reduces chi-squared (for
the 21 bins from 500 to 920 keV) by 12.6 from 28.3 to 16.7, and the reduced
chi-squared value from 1.41 to 0.98. Furthermore, at the 99% Confidence Level,
the data impose lower and upper bounds of (24, 146) respectively upon the mean
excess pair count in this bin. This data therefore provides positive,
statistically significant evidence for sharp pairs near 790 keV. Whether this
evidence is compelling is a separate question not addressed here.


title:
The nuclear liquid-gas phase transition within Fermionic Molecular
  Dynamics

abstract:
  The time evolution of excited nuclei, which are in equilibrium with the
surrounding vapour, is investigated. It is shown that the finite nuclear
systems undergo a first oder phase transition. The caloric curve is presented
for excited Oxygen, Magnesium, Aluminum and Calcium and the critical
temperature is estimated for Oxygen.


title: Covariant equations for the three-body bound state

abstract:
  The covariant spectator (or Gross) equations for the bound state of three
identical spin 1/2 particles, in which two of the three interacting particles
are always on shell, are developed and reduced to a form suitable for numerical
solution. The equations are first written in operator form and compared to the
Bethe-Salpeter equation, then expanded into plane wave momentum states, and
finally expanded into partial waves using the three-body helicity formalism
first introduced by Wick. In order to solve the equations, the two-body
scattering amplitudes must be boosted from the overall three-body rest frame to
their individual two-body rest frames, and all effects which arise from these
boosts, including the Wigner rotations and rho-spin decomposition of the
off-shell particle, are treated exactly. In their final form, the equations
reduce to a coupled set of Faddeev-like double integral equations with
additional channels arising from the negative rho-spin states of the off-shell
particle.


title:
``Soft'' transverse expansion and flow in a multi-fluid model without
  phase transition

abstract:
  We study transverse expansion and directed flow in Au(11AGeV)Au reactions
within a multi-fluid dynamical model. Although we do not employ an equation of
state (EoS) with a first order phase transition, we find a slow increase of the
transverse velocities of the nucleons with time. A similar behaviour can be
observed for the directed nucleon flow. This is due to non-equilibrium effects
which also lead to less and slower conversion of longitudinal into transverse
momentum. We also show that the proton rapidity distribution at CERN energies,
as calculated within this model, agrees well with the preliminary NA44-data.


title: Analytically Solvable Mean-Field Potential for Stable and Exotic Nuclei

abstract:
  Slater determinants built from the single-particle wave functions of the
analytically solvable Ginocchio potential are used to approximate the
self-consistent Hartree-Fock solutions for the ground states of nuclei. The
results indicate that the Ginocchio potential provides a good parametrization
of the nuclear mean field for a wide range of nuclei, including those at the
limit of particle stability.


title: Quantum Mechanical Localization Effects for Bose-Einstein Correlations

abstract:
  For a set of N identical massive boson wavepackets with optimal initial
quantum mechanical localization, we calculate the Hanbury-Brown/Twiss (HBT)
two-particle correlation function. Our result provides an algorithm for
calculating one-particle spectra and two-particle correlations from an
arbitrary phase space occupation (q_i,p_i,t_i)_{i=1,N} as e.g. returned by
event generators. It is a microscopic derivation of the result of the coherent
state formalism, providing explicit finite multiplicity corrections. Both the
one- and two-particle spectra depend explicitly on the initial spatial
wavepacket width which parametrizes the quantum mechanical wavepacket
localization. They provide upper and lower bounds which suggest that a
realistic value for this width has the order of the Compton wavelength.


title: Analysis of Kaon Production at SIS Energies

abstract:
  We analyse the production and propagation of pions and kaons in heavy-ion
reactions from 0.8 -- 1.8~A$\cdot$GeV within a coupled channel transport
approach including the kaon production channels $BB \to K^+YN, \pi B\to K^+Y,
BB \to NN K \bar{K}, \pi B\to N K\bar{K}, K^+B\to K^+B $ and $\pi \pi\to K
\bar{K}$. Assuming the hyperon selfenergy to be 2/3 of the nucleon selfenergy
we find that all inclusive experimental $K^+$ spectra at SIS energies can be
reproduced reasonably well without any selfenergies for the kaons although a
slightly repulsive kaon potential cannot be excluded by the present data on
kaon spectra and flow.


title: Level Statistics of Near-Yrast States in Rapidly Rotating Nuclei

abstract:
  The nearest neighbour level spacing distribution and the $\Delta_3$
statistics of level fluctuations associated with very high spin states ($I
\gesim 30$) in rare-earth deformed nuclei are analysed by means of a cranked
shell model. The many particle-many hole configurations created in the rotating
Nilsson potential are mixed by the surface-delta two-body residual interaction.
The levels in the near-yrast region show a Poisson-like level spacing
distribution. As the intrinsic excitation energy $U$ increases, the level
statistics shows a gradual transition from order to chaos, reaching at $U
\gesim 2$ MeV the Wigner distribution typical of the Gaussian orthogonal
ensemble of random matrices. This transition is caused by the residual two-body
interaction. On the other hand, the level spacings between the yrast and the
first excited state show a peculiar behaviour, displaying a Wigner-like
distribution instead of the Poisson-like distribution seen for the other
near-yrast rotational states. The lowest spacings reflect the properties of the
single-particle orbits in the mean-field, and are only weakly affected by the
residual two-body interaction.


title:
The effects of varying the strengths of tensor and spin-orbit
  interactions on M1 and E2 rates in ^{12}C: Comparison of results in $\Delta N
  = 0$ and $\Delta N = 0 + 2\hbar\omega$ spaces}

abstract:
  The energies and transition rates to $J=1^{+} T=1$ and $J=2^{+} T=0,1$ states
in ^{12}C with matrix elements fitted to realistic $G$ matrix elements obtained
in non-relativistic approaches are studied. Then the effects of varying the
strengths of the two-body tensor and spin-orbit interactions are also
considered. The calculations are done in both a small space (0p) and a large
space (0p + $2\hbar\omega$). In the small space the B(M1) from ground to the
$J=1^{+} T=1$ is enhanced and gets closer to experiment if the strength of the
spin-orbit interaction is increased and/or if that of the tensor interaction is
made weaker. In a large space the spin B(M1) gets reduced by almost a factor of
two. A `self-weakening' mechanism for the tensor interaction which succeeded in
explaining anomalies in other nuclei does not seem to work for this case.


title: The anapole moment and nucleon weak interactions

abstract:
  From the recent measurement of parity nonconservation (PNC) in the Cs atom we
have extracted the constant of the nuclear spin dependent electron-nucleon PNC
interaction, $\kappa = 0.442 (63)$; the anapole moment constant, $\kappa_a =
0.364 (62)$; the strength of the PNC proton-nucleus potential, $g_p = 7.3 \pm
1.2 (exp.) \pm 1.5 (theor.)$; the $\pi$-meson-nucleon interaction constant,
$f_\pi \equiv h_\pi^{1} = [9.5 \pm 2.1 (exp.) \pm 3.5 (theor.)] \times
10^{-7}$; and the strength of the neutron-nucleus potential, $g_n = -1.7 \pm
0.8 (exp.) \pm 1.3 (theor.)$.


title: Particle-unstable nuclei in the Hartree-Fock theory

abstract:
  Ground state energies and decay widths of particle unstable nuclei are
calculated within the Hartree-Fock approximation by performing a complex
scaling of the many-body Hamiltonian. Through this transformation, the wave
functions of the resonant states become square integrable. The method is
implemented with Skyrme effective interactions. Several Skyrme parametrizations
are tested on four unstable nuclei: 10He, 12O, 26O and 28O.


title:
Analytic expressions for the single particle energies with a
  quadrupole-quadrupole interaction and the relation to Elliott's SU(3) model

abstract:
  We present an analytical proof and a generalization of the
Fayache-Sharon-Zamick relation between single particle energy splittings and
the SU(3) limit in Elliott's model.


title: Recoil effects on nucleon electromagnetic form factors

abstract:
  The electromagnetic form factors are computed using eigenstates of linear
momentum for the nucleon. The latter is described in the framework of the
chiral color-dielectric model, projecting the hedgehog ansatz on eigenstates of
angular momentum and isospin. Form factors are well reproduced, with the
exception of the magnetic one for the proton, up to $q^2 \simeq 0.5$ GeV$^2$.
The effect of the removal of the spurious center-of-mass contributions shows up
mainly in the electric form factor of the proton. A noticeable improvement is
obtained with respect to the calculation without linear momentum projection.


title:
Parity-violating quasifree electron-deuteron scattering in a covariant
  approach

abstract:
  The role of relativistic corrections associated with lower Dirac components
of the deuteron wavefunction, is examined for parity-violating (PV) electron
scattering. The relation between these corrections and negative energy
components of the struck nucleon in relativistic PWIA is elucidated. The model
dependence induced by describing such effects, using different deuteron vertex
functions and prescriptions for the half-off-shell nucleon vertices, is
compared against the precision required for studies of nucleon strangeness in
quasielastic PV $e-d$ scattering.


title:
Vacuum Effects and Compressional Properties of Nuclear Matter in Cutoff
  Field Theory

abstract:
  Including the vacuum effects, the compressional properties of nuclear matter
are studied in the cutoff field theory. Under the Hartree approximation, the
low-energy effective Lagrangian is derived in the framework of the
renormalization group methods. The coefficients are determined in a way where
the physical results hardly depend on the value of the cutoff which is
conveniently introduced into the theory. It is shown that, to reproduce the
empirical data of the nucleus incompressibility, the compressibility of the
nuclear matter is favorable to be 250$\sim$350MeV.


title:
A self-consistent treatment of damped motion for stable and unstable
  collective modes

abstract:
  We address the dynamics of damped collective modes in terms of first and
second moments. The modes are introduced in a self-consistent fashion with the
help of a suitable application of linear response theory. Quantum effects in
the fluctuations are governed by diffusion coefficients D_{\mu\nu}. The latter
are obtained through a fluctuation dissipation theorem generalized to allow for
a treatment of unstable modes. Numerical evaluations of the D_{\mu\nu} are
presented. We discuss briefly how this picture may be used to describe global
motion within a locally harmonic approximation. Relations to other methods are
discussed, like "dissipative tunneling", RPA at finite temperature and
generalizations of the "Static Path Approximation".


title:
Statistical fluctuations for the fission process on its decent from
  saddle to scission

abstract:
  We reconsider the importance of statistical fluctuations for fission dynamics
beyond the saddle in the light of recent evaluations of transport coefficients
for average motion. The size of these fluctuations are estimated by means of
the Kramers-Ingold solution for the inverted oscillator, which allows for an
inclusion of quantum effects.


title: Photoabsorption on a Nucleon in the D_{13} Resonance Energy Region

abstract:
  We present a simple model for the $\gamma N \to \pi \pi N$ reaction which
reproduces the cross sections of the $\pi^+ \pi^- p, \pi^+ \pi^- n, \pi^+ \pi^0
n$ and $\pi^- \pi^0 p$ channels over the range of the energies 0.41-0.85 GeV.
We use the dynamical model for the resonances, \Delta(1232), N^*(1520) and
\rho-meson. The total photoabsorption off a nucleon is also discussed.


title: Double Giant Dipole Resonance in ^{208}Pb

abstract:
  Double-dipole excitations in ^{208}Pb are analyzed within a microscopic model
explicitly treating 2p2h-excitations. Collective states built from such
2p2h-excitations are shown to appear at about twice the energy of the isovector
giant dipole resonance, in agreement with the experimental findings. The
calculated cross section for Coulomb excitation at relativistic energies cannot
explain simultaneously the measured single-dipole and double-dipole cross
sections, however.


title: Comment on ``Validity of certain soft-photon amplitudes''

abstract:
  The criteria suggested by Welsh and Fearing (nucl-th/9606040) to judge the
validity of certain soft-photon amplitudes are examined. We comment on aspects
of their analysis which lead to incorrect conclusions about published
amplitudes and point out important criteria which were omitted from their
analysis.


title:
Benchmark Calculations for the Triton Binding Energy for Modern NN
  Forces and the pi-pi Exchange Three-Nucleon Force

abstract:
  We present high precision benchmark calculations for the triton binding
energy using the most recent, phase equivalent realistic nucleon-nucleon (NN)
potentials and the Tuscon-Melbourne pi-pi three-nucleon force (3NF). That 3NF
is included with partial waves up to a total two-body angular momentum of
j_max=6. It is shown that the inclusion of the 3NF slows down the convergence
in the partial waves and j_max=5 is needed in order to achieve converged
results within a few keV. We adjust the cut-off parameter Lambda in the form
factors of the Tuscon-Melbourne 3NF separately for the different NN potentials
to the triton binding energy. This provides a set of phenomenological
three-nucleon Hamiltonians which can be tested in three-nucleon scattering and
systems with A>3. A connection between the probability to find two nucleons at
short distances in the triton and the effect of that 3NF on the triton binding
energy is pointed out.


title: Phi Meson Production in Heavy-Ion Collisions at SIS Energies

abstract:
  Phi meson production in heavy-ion collisions at SIS/GSI energies ($\sim 2$
GeV/nucleon) is studied in the relativistic transport model. We include
contributions from baryon-baryon, pion-baryon, and kaon-antikaon collisions.
The cross sections for the first two processes are obtained in an
one-boson-exchange model, while that for the last process is taken to be of
Breit-Wigner form through the phi meson resonance. The dominant contribution to
phi meson production in heavy ion collisions at these energies is found to come
from secondary pion-nucleon collisions. Effects due to medium modifications of
kaon masses are also studied and are found to reduce the phi meson yield by
about a factor of two, mainly because of increased phi decay width as a result
of dropping kaon-antikaon masses. In this case, the $\phi/K^-$ ratio is about
4%, which is a factor of 2-3 below preliminary experimental data from the FOPI
collaboration at GSI. Including also the reduction of phi meson mass in medium
increases this ratio to about 8%, which is then in reasonable agreement with
the data.


title: Chiral Perturbation Theory and the pp -> pp pi0 Reaction Near Threshold

abstract:
  A chiral-perturbative consideration of the near-threshold pp -> pp pi0
reaction indicates that the pion-rescattering term has a substantial energy and
momentum dependence. The existing calculations that incorporate this dependence
give pion rescattering contributions significantly larger than those of the
conventional treatment, and this enhanced rescattering term interferes
destructively with the one-body impulse term, leading to theoretical cross
sections that are much smaller than the observed values. However, since the
existing calculations are based on coordinate-space representation, they
involve a number of simplifying assumptions about the energy-momentum flow in
the rescattering diagram, even though the delicate interplay between the
one-body and two-body terms makes it desirable to avoid these kinematical
assumptions. We carry out here a momentum-space calculation that retains the
energy-momentum dependence of the vertices as predicted by chiral perturbation
theory. Our improved treatment increases the rescattering amplitude by a factor
of 3 over the value obtained in the r-space calculations. The pp -> pp pi0
transition amplitude, which is now dominated by the rescattering term, leads to
the cross section much larger than what was reported in the approximate r-space
calculations. Thus, the extremely small cross sections obtained in the previous
chiral perturbative treatments of this reaction should be considered as an
accidental consequence of the approximations employed rather than a general
feature.


title:
A General Signal of a Phase Transition from Single-Particle Momentum
  Distributions

abstract:
  A two-particle space correlation function is derived from the single-particle
momentum distribution of the emission source. A signal of a first order phase
transition is obtained from this correlation function if density fluctuations
are large.


title:
Helicity Asymmetry for Proton Emission from Polarized Electrons in the
  Eikonal Regime

abstract:
  The nuclear response to longitudinally polarized electrons, detected in
coincidence with out-of-plane high-energy protons, is discussed in a simple
model where the ejectile wave function is approximated as a plane wave with a
complex wave vector. This choice is equivalent to solve the problem of
Final-State Interactions (FSI) in homogeneous nuclear matter, as the residual
nucleus can be described to a first approximation when dealing with very fast
emitted protons. The main advantage of the present method is that in the
framework of the Distorted-Wave Impulse Approximation (DWIA) it allows for an
analytical derivation of all the components of the nuclear response. It emerges
that cancellations among the leading contributions determine the very small
absolute size of the socalled fifth structure function and produce a nontrivial
asymptotic scaling of the related helicity asymmetry for large values of the
momentum transfer.


title: Large Mass Diphotons From Relativistic Heavy Ion Collisions

abstract:
  We evaluate the production of large mass diphotons from quark annihilation at
BNL RHIC and CERN LHC energies from central collisions of gold nuclei. The
collision is assumed to lead to either a thermally and chemically equilibrated
quark gluon plasma, or a free-streaming quark gluon gas having an identical
initial entropy, or a chemically equilibrating quark gluon system, with the
same entropy at $T=T_c$. We also obtain an estimate of hard photon pairs from
initial state quark annihilation and find that the thermal production dominates
the yield up to $M \approx$ 4 GeV at RHIC, and up to 6 GeV at LHC. A simulation
study of decay versus thermal diphotons is presented.


title: Particle production in quantum transport theories

abstract:
  The particle production in the intermediate energy heavy ion collisions is
discussed in the framework of the nonequilibrium Green's functions formalism.
The evolution equations of the Green's functions for fermions allows for the
discussion of the off-shell fermion propagator and of the large momentum
component in the initial state. For the case of a homogeneous system numerical
calculations of the meson production rate are performed and compared with the
semiclassical production rate.


title:
Hadron production in relativistic nuclear collisions: thermal hadron
  source or hadronizing quark-gluon plasma?

abstract:
  Measured hadron yields from relativistic nuclear collisions can be equally
well understood in two physically distinct models, namely a static thermal
hadronic source vs.~a time-dependent, nonequilibrium hadronization off a
quark-gluon plasma droplet. Due to the time-dependent particle evaporation off
the hadronic surface in the latter approach the hadron ratios change (by
factors of $<\approx 5$) in time. Final particle yields reflect time averages
over the actual thermodynamic properties of the system at a certain stage of
the evolution. Calculated hadron, strangelet and (anti-)cluster yields as well
as freeze-out times are presented for different systems. Due to strangeness
distillation the system moves rapidly out of the T, $\mu_q$ plane into the
$\mu_s$-sector. Strangeness to baryon ratios f_s=1-2 prevail during a
considerable fraction (50%) of the time evolution (i.e. $\Lambda$-droplets or
even $\Xi^-$-droplets form the system at the late stage: The possibility of
observing this time evolution via HBT correlations is discussed). The observed
hadron ratios require $T_c\approx 160 MeV$ and $B^{1/4}>\approx 200 MeV$. If
the present model is fit to the extrapolated hadron yields, metastable
hypermatter can only be produced with a probability $p< 10^{-8}$ for $A \ge 4$.


title: Compression and Expansion in Central Collisions

abstract:
  Dynamics of central collisions of heavy nuclei in the energy range from few
tens of MeV/nucleon to a couple of GeV/nucleon is discussed. As the beam energy
increases and/or the impact parameter decreases, the maximum compression
increases. It is argued that the hydrodynamic behavior of matter sets in the
vicinity of balance energy. At higher energies shock fronts are observed to
form within head-on reaction simulations, perpendicular to beam axis and
separating hot compressed matter from cold. In the semicentral reactions a weak
tangential discontinuity develops in-between these fronts. The hot compressed
matter exposed to the vacuum in directions parallel to the shock fronts begins
to expand collectively into these directions. The expansion affects particle
angular distributions and mean energy components and further shapes of spectra
and mean energies of particles emitted into any one direction. The variation of
slopes and the relative yields measured within the FOPI collaboration are in a
general agreement with the results of simulations. As to the FOPI data on
stopping, they are consistent with the preference for transverse over the
longitudinal motion in the head-on Au + Au collisions. Unfortunately, though,
the data cannot be used to decide directly on that preference due to acceptance
cuts. Tied to the spatial and temporal changes in the reactions are changes in
the entropy per nucleon.


title: Transverse Photon Spectrum from QGP Fluid

abstract:
  We calculate the thermal photon distribution from the hot QCD matter produced
by high energy nuclear collisions based on a hydrodynamical model, and compare
it with the recent experimental data obtained by CERN WA80. Through the
asymptotic value of the slope parameter of the transverse momentum
distribution, we investigate the characteristic temperature of the QCD fluid.


title:
Correlations and the Cross Section of Exclusive ($e,e'p$) Reactions for
  $^{16}$O

abstract:
  The reduced cross section for exclusive ($e,e'p$) reactions has been studied
in DWIA for the example of the nucleus $^{16}$O using a spectral function
containing effects of correlations. The spectral function is evaluated directly
for the finite nucleus starting from a realistic nucleon-nucleon interaction
within the framework of the Green's function approach. The emphasis is focused
on the correlations induced by excitation modes at low energies described
within a model-space of shell-model configurations including states up to the
$sdg$ shell. Cross sections for the $p$-wave quasi-hole transitions at low
missing energies are presented and compared with the most recent experimental
data. In the case of the so-called perpendicular kinematics the reduced cross
section derived in DWIA shows an enhancement at high missing momenta as
compared to the PWIA result. Furthermore the cross sections for the $s$- and
$d$-wave quasi-hole transitions are presented and compared to available data at
low missing momenta. Also in these cases, which cannot be described in a model
without correlations, a good agreement with the experiment is obtained.


title:
Constraints on the relativistic mean field of $\Delta$-isobar in nuclear
  matter

abstract:
  The effects of the presence of $\Delta$-isobars in nuclear matter are studied
in the framework of relativistic mean-field theory. The existence of stable
nuclei at saturation density imposes constraints on the $\Delta$-isobar
self-energy and thereby on the mean-field coupling constants of the scalar and
vector mesons with $\Delta$-isobars. The range of possible values for the
scalar and vector coupling constants of $\Delta$-isobars with respect to the
nucleon coupling is investigated and compared to recent predictions of QCD
sum-rule calculations.


title: An Effective Equation of State for Dense Matter with Strangeness

abstract:
  An effective equation of state (EoS) which generalizes the Lattimer-Swesty
equation for nuclear matter is presented for matter at supernuclear densities
including strange baryons. It contains an adjustable baryon potential energy
density, based on models of local potentials for the baryon-baryon
interactions. The features of the equation rely on the properties of nuclei for
the nucleon-nucleon interactions, and mainly on experimental data from
hypernuclei for the hyperon-nucleon and hyperon-hyperon interactions. The EoS
is used to calculate equilibrium compositions and thermodynamic properties of
high density matter with strangeness in two astrophysical contexts: neutron
star matter (transparent to neutrinos) and proto-neutron star matter (opaque to
neutrinos). The effective EoS reproduces typical properties of high density
matter found in theoretical microscopic models. Of these, the main result is
that hyperons appear in both types of matter at about twice the nuclear
saturation density, and that their appearance significantly softens the EoS.
The range of maximal masses of neutron stars found in a comprehensive parameter
survey is 1.4-1.7 $M_\odot$. Another typical result is that the maximal mass of
a proto-neutron star with strange baryons is higher than that of an evolved
neutron star (opposite to the case of nuclear matter), setting the stage for a
"delayed collapse" scenario.


title: Results from Shell Model Monte Carlo Studies

abstract:
  We review results obtained using Shell Model Monte Carlo (SMMC) techniques.
These methods reduce the imaginary-time many-body evolution operator to a
coherent superposition of one-body evolutions in fluctuating one-body fields;
the resultant path integral is evaluated stochastically. After a brief review
of the methods, we discuss a variety of nuclear physics applications. These
include studies of the ground-state properties of pf-shell nuclei, Gamow-Teller
strength distributions, thermal and rotational pairing properties of nuclei
near N=Z, $\gamma$-soft nuclei, and $\beta\beta$-decay in ^{76}Ge. Several
other illustrative calculations are also reviewed. Finally, we discuss
prospects for further progress in SMMC and related calculations.


title: Microscopic Enhancement of Heavy-Element Production

abstract:
  Realistic fusion barriers are calculated in a macroscopic-microscopic model
for several soft-fusion heavy-ion reactions leading to heavy and superheavy
elements. The results obtained in such a realistic picture are very different
from those obtained in a purely macroscopic model. For reactions on 208:Pb
targets, shell effects in the entrance channel result in fusion-barrier
energies at the touching point that are only a few MeV higher than the ground
state for compound systems near Z = 110. The entrance-channel fragment-shell
effects remain far inside the touching point, almost to configurations only
slightly more elongated than the ground-state configuration, where the fusion
barrier has risen to about 10 MeV above the ground-state energy. Calculated
single-particle level diagrams show that few level crossings occur until the
peak in the fusion barrier very close to the ground-state shape is reached,
which indicates that dissipation is negligible until very late in the fusion
process. Whereas the fission valley in a macroscopic picture is several tens of
MeV lower in energy than is the fusion valley, we find in the
macroscopic-microscopic picture that the fission valley is only about 5 MeV
lower than the fusion valley for soft-fusion reactions leading to compound
systems near Z = 110. These results show that no significant
``extra-extra-push'' energy is needed to bring the system inside the fission
saddle point and that the typical reaction energies for maximum cross section
in heavy-element synthesis correspond to only a few MeV above the maximum in
the fusion barrier.


title: EMC effect from the QMC and the QHD descriptions

abstract:
  The density dependence of the bag parameters is studied in a framework which
links the Quark-Meson Coupling model and the field theory of hadrons for
nuclear matter description. The EMC effect is treated in the dynamical
rescaling hypothesis by using the density dependent bag radius and the Local
Density Approximation. Our results are in good agreement with the expected
values of the rescaling parameter.


title: The extraction of hadronic parameters from experiments on pionium

abstract:
  Experimental values of the lifetime of the 1s level of pionium and of the
difference between the energies of the 2s and 2p levels yield values of the
a(0c) and a(cc) elements of the s-wave scattering matrix for the 2-channel (pi+
pi-, pi0 pi0) system at the pi+ pi- threshold. We develop a method for
obtaining the isospin invariant quanties a20 - a00 and 2a00 + a20 from a(0c)
and a(cc). We emphasize that the isospin invariant scattering lengths a00 and
a20 universally used in the literature cannot be considered to be purely
hadronic quantities.


title: Dileptons from Disoriented Chiral Condensates

abstract:
  Disoriented chiral condensates or long wavelength pionic oscillations and
their interaction with the thermal environment can be a significant source of
dileptons. We calculate the yield of such dilepton production within the linear
sigma model, both in a quantal mean-field treatment and in a semi-classical
approximation. We then illustrate the basic features of the dilepton spectrum
in a schematic model. We find that dilepton yield with invariant mass near and
below $2m_{\pi}$ due to the soft pion modes can be up to two orders of
magnitude larger than the corresponding equilibrium yield.


title: Time invariance violating nuclear electric octupole moments

abstract:
  The existence of a nuclear electric octupole moment (EOM) requires both
parity and time invariance violation. The EOMs of odd $Z$ nuclei that are
induced by a particular T- and P-odd interaction are calculated. We compare
such octupole moments with the collective EOMs that can occur in nuclei having
a static octupole deformation. A nuclear EOM can induce a parity and time
invariance violating atomic electric dipole moment, and the magnitude of this
effect is calculated. The contribution of a nuclear EOM to such a dipole moment
is found, in most cases, to be smaller than that of other mechanisms of atomic
electric dipole moment production.


title:
The new limits of the neutrinoless $(\mu^-,e^-)$ conversion branching
  ratio

abstract:
  The nuclear physics dependence of the exotic $(\mu^-,e^-)$ conversion
branching ratio $R_{\mu e^-}$ for the experimentally most interesting nuclei
$^{208}Pb$ and $^{48}Ti$, is investigated in various nuclear models. The
results thus obtained are combined with the new experimental limits extracted
at PSI for these nuclei to put bounds on the elementary particle parameters
entering $R_{\mu e^-}$ such as intermediate neutrino masses and mixing angles
as well as relevant parameters of intermediate supersymmetric particles (masses
and mixing of s-fermions and neutralinos).


title:
State-by-state calculations for all channels of the exotic $(\mu^-,e^-)$
  conversion process

abstract:
  The coherent and incoherent channels of the neutrinoless muon to electron
conversion in nuclei, $\mu^- (A,Z) \to e^- (A,Z)^*$, are studied throughout the
periodic table. The relevant nuclear matrix elements are computed by explicitly
constructing all possible final nuclear states in the context of the
quasi-particle RPA. The obtained results are discussed in view of the existing
at PSI and TRIUMF experimental data for $^{48}Ti$ and $^{208}Pb$ and compared
with results obtained by: (i) shell model sum-rule techniques (ii) nuclear
matter mapped into nuclei via a local density approximation and (iii) earlier
similar calculations.


title: Radiative pion capture in nuclei: a continuum shell-model approach

abstract:
  The radiative pion capture process in nuclei is approached by using a
continuum shell-model description of the nucleus, together with a
phenomenological treatment of the two particle-two hole effects. It is found
that these effects play an important role to reproduce the observed
experimental photon energy distribution. This distribution as well as the
integrated one depends significantly on the details of the mean field
potential. This makes this process interesting to investigate the nuclear
structure dynamics.


title:
The excitation of a quantum gas of independent particles under periodic
  perturbation in integrable or non-integrable potential

abstract:
  The excitation of a quantum gas of 112 independent fermions in the
time-dependent potential well, periodically oscillating around the spherical
shape, was followed over 10 oscillation cycles. Five different oscillation
frequencies are considered for each of the five types of deformations:
spheroidal and Legendre polynomial ripples: P_3, P_4, P_5 and P_6. The
excitation rate of the gas in the deforming hard-walled cavities substantially
decreases after initial one or two cycles and the final excitation energy is a
few times smaller than the wall formula predictions. Qualitatively similar
results are obtained for the diffused Woods-Saxon well. The details and
possible origins of this behaviour are discussed as well as the consequences
for the one-body dissipation model of nuclear dynamics.


title: Coherent two pion photoproduction on 12C

abstract:
  We develop the formalism for coherent two pion photoproduction in nuclei and
perform actual calculations of cross sections for $\pi^-\pi^+$ and $\pi^0\pi^0$
photoproduction on $^{12}C$. We find that due to the isospin symmetry the cross
section for $\pi^0\pi^0$ production is very small and has a maximum when the
pions propagate together. However, the kinematical region where the energies
and polar angles of the two $\pi^0$ mesons are equal and their relative
azimuthal angle $\phi=180^0$ is forbidden. Conversely in the $\pi^-\pi^+$
production the pions prefer to have a relative azimuthal angle 180$^0$ and the
production of the pions propagating together is suppressed. The dominant
one-body mechanism in both channels is related to the excitation of the
$\Delta$ isobar. Hence the reaction can serve as a source of information about
$\Delta$'s properties in nucleus. We have found that the reaction is sensitive
to effects of the pion and $\Delta$ renormalization in the nuclear medium,
similar to those found in the coherent $(\gamma,\pi^0)$ reaction, but magnified
because of the presence of the two pions.


title:
Hyperfine Structure Constants for Eu Isotopes: Is The Empirical Formula
  of HFS Anomaly Universal ?

abstract:
  We calculate the hyperfine structure constant for the Eu isotopes with shell
model wave functions. The calculated results are compared with those predicted
by the Moskowitz-Lombardi (M-L) empirical formula. It turns out that the two
approaches give the very different behaviors of the hfs constants in the
isotope dependence. This should be easily measured by experiment, which may
lead to the universality check of the M-L formula.


title: Eta-meson light nucleus scattering and Charge Symmetry Breaking

abstract:
  The \eta-meson collision with light nuclei, ^2H, ^3H, ^3He, and ^4He, is
considered on the basis of a microscopic approach which utilises Faddeev type
and Lippmann-Schwinger equations. The nuclear hamiltonian is approximated by
the finite rank approximation which amounts to the coherent approximation. The
\eta-nucleus scattering length and the resonance and bound--state poles of the
amplitude describing elastic scattering of \eta-meson by these nuclei are
obtained. For each of the nuclei considered, the minimal factor enhancing the
\eta N--attraction that moves the poles to the quasi--bound state area of the
complex k--plane, is determined. It is shown that within the existing
uncertainties in the elementary \eta N iteraction all these nuclei can support
a quasi--bound state which can result in a formation of an eta-mesic nucleus.
Various aspects of the eta-nucleus physics are discussed with specific emphasis
given to the \eta--nucleus effective interaction in configuration space
(constructed via the Marchenko inverse scattering method), to the
Okubo--Zweig--Iizuka (OZI) rule, and to the charge symmetry breaking problem.


title:
Muon capture by oriented nuclei: new possibilities for studying induced
  pseudoscalar interaction

abstract:
  Angular distribution of neutrinos (recoil nucleus) in muon capture for an
allowed Gamov-Teller transition is considered by taking account of hyperfine
effects. This angular distribution is shown to include a correlation of the
form P_2(cos A), where A is the angle between the neutrino momentum and the
axis specifying the orientation of the initial mesic atom. This correlation,
which arises only if the initial mesic atom is aligned, proves highly sensitive
to the form factor g_P of induced pseudoscalar interaction. The proposed method
for determinating g_P may be realized for the transition 1+ to 2+ from the
ground state of the 6-Li nucleus to the narrow resonance of the 6-He nucleus in
continuum, as well as in the processes like 10-B(3+) to 10-Be(2+), 11-B(3/2-)
to 11-Be(1/2-), 23-Na(3/2+) to 23-Ne(1/2+) with transitions to bound states.


title:
T-noninvariant effect in muon capture by 6-Li nucleus with decay to a
  continuum

abstract:
  The T-noninvariant transverse polarization of neutrons is considered for muon
capture by a 6-Li nucleus with decay into a quasistationary 2+ state of the
three particle alpha+n+n continuum. This polarization is orthogonal to the
plane spanned by the polarization axis of the initial mesic atom and the
neutron momentum. The situation in which neutrons that are emitted in the plane
orthogonal to the axis of the mesic-atom polarization and which have oppositely
directed momenta equal in magnitude are selected is analyzed. The wave function
of the final state is constructed by using the method of hyperspherical
harmonics. In the approximation of the allowed Gamow-Teller transition 1+ to
2+, this neutron polarization is expressed in terms of the T-noninvariant
relative phase of reduced matrix elements for transitions from the 6-Li ground
state to various final-state configurations.


title:
The Delta(1232)-nucleon interaction in the 2H(p,n) charge exchange
  reaction

abstract:
  The 2H(p,n) charge exchange reaction at T_p=790 MeV is used to study the
Delta(1232)-nucleon interaction in the Delta resonance excitation energy
region. For the Delta-N potential, a meson exchange model is adopted where pi,
rho, omega, and sigma meson exchanges are taken into account. The deuteron
disintegration below and above pion threshold is calculated using a coupled
channel approach. Various observables, such as the inclusive cross section, the
quasifree Delta decay, the coherent pion production, and the two-nucleon
breakup are considered. It is shown that these observables are influenced by
the dynamical treatment of the Delta degrees of freedom. Of special interest is
the coherent pion decay of the Delta resonance which is studied by means of the
exclusive reaction 2H(p,n pi+)2H. Both the peak energy and the magnitude of the
coherent pion production cross section depend very sensitively on the strength
of the Delta-N potential. The coherent pions have a peak energy of 300 MeV and
a strongly forward peaked angular distribution.


title: Algebraic treatment of three-body problems

abstract:
  We discuss an algebraic treatment of three-body systems in terms of a U(7)
spectrum generating algebra. In particular, we develop the formalism for
nonlinear configurations and present an algebraic description of vibrational
and rotational excitations of symmetric (X_3) and asymmetric tops (XY_2 and
XYZ). The relevant point group symmetry is incorporated exactly.


title: On the relativistic field theory model of the deuteron II

abstract:
  The relativistic field theory model of the deuteron is applied to the
calculation of the cross sections of the low-energy radiative neutron-proton
capture n + p -> D + gamma and the low-energy two-proton fusion p + p -> D +
e^+ + nu_e. For the low-energy radiative neutron-proton capture n + p -> D +
gamma our result agrees well with both the experimental data and the potential
model prediction. In the case of the two-proton fusion the cross section
obtained is 2.9 times as much as that given by the potential approach. The
obtained result is discussed in connection with the solar neutrino problem.
  ERRATUM: We correct the value of the cross section for pp-fusion p + p -> D +
e^+ + nu_e. We find a contribution to the astrophysical factor \delta S_pp(0) =
2.01 x 10^{-25} (1 +/- 0.30) MeV b which is obtained only due to weak and
strong low-energy interactions of the protons and the deuteron when neglecting
the Coulomb repulsion between protons in the intermediate state. Minor
misprints are corrected.


title: Higher-Order Nuclear-Polarizability Corrections in Atomic Hydrogen

abstract:
  Nuclear-polarizability corrections that go beyond unretarded-dipole
approximation are calculated analytically for hydrogenic (atomic) S-states.
These retardation corrections are evaluated numerically for deuterium and
contribute -0.68 kHz, for a total polarization correction of 18.58(7) kHz. Our
results are in agreement with one previous numerical calculation, and the
retardation corrections completely account for the difference between two
previous calculations. The uncertainty in the deuterium polarizability
correction is substantially reduced. At the level of 0.01 kHz for deuterium,
only three primary nuclear observables contribute: the electric polarizability,
$\alpha_E$, the paramagnetic susceptibility, $\beta_M$, and the third Zemach
moment, $< r^3 >_{(2)}$. Cartesian multipole decomposition of the virtual
Compton amplitude and its concomitant gauge sum rules are used in the analysis.


title: In-Medium Effective Axial-Vector Coupling Constant

abstract:
  The axial-vector coupling constant in nuclear medium is systematically
studied using chiral perturbation theory. For normal nuclear matter, the first
non-trivial corrections are estimated based on the independent particle
approximation taking into account nuclear correlations in nuclear medium. The
one-pion-exchange (OPE) two-body interactions turn out to enhance the coupling
constant by $\delta g_A/g_A\simeq (0.09 \sim 0.15)$. The role of the
four-nucleon contact interaction, whose low-energy constants are yet to be
determined, is analyzed in connection with the empirical quenching factor of
$\delta g_A/g_A\simeq -0.2$ in the presence of the nuclear short-range
correlation. Conventional approaches are discussed in the light of our result.


title: Yang-Mills Radiation in Ultra-relativistic Nuclear Collisions

abstract:
  The classical Yang-Mills radiation computed in the McLerran-Venugopalan model
is shown to be equivalent to the gluon bremsstrahlung distribution to lowest
order in pQCD. The classical distribution is also shown to match smoothly onto
the conventional pQCD mini-jet distribution at a scale characteristic of the
initial parton transverse density of the system. The atomic number and energy
dependence of that scale is computed from available structure function
information. The limits of applicability of the classical Yang-Mills
description of nuclear collisions at RHIC and LHC energies are discussed.


title:
Calculation of $g_{\pi NS_{11}}$ and $g_{\eta NS_{11}}$ Couplings in QCD
  Sum Rules

abstract:
  We calculate the coupling constants, $g_{\pi NS_{11}}$ and $g_{\eta NS_{11}},
using QCD sum rules in the presence of an external meson field. A covariant
derivative is introduced within the S_{11} interpolating field so that in the
nonrelativistic limit the field dominantly reduces to two quarks in the s-wave
state and one quark in the p-wave state. Our result for the couplings obtained
by further making use of the soft-meson theorem qualitatively agrees with its
phenomenological value extracted from the S_{11}(1535) decay width. The
prediction for the couplings however depend on the value of quark-gluon
condensate, $< {\bar q} g_s \sigma \cdot {\cal G} q >$, which is also important
in the calculation of the S_{11}(1535) mass itself within the sum rule
approach.


title:
Interfering Doorway States and Giant Resonances. I: Resonance Spectrum
  and Multipole Strengths

abstract:
  A phenomenological schematic model of multipole giant resonances (GR) is
considered which treats the external interaction via common decay channels on
the same footing as the coherent part of the internal residual interaction. The
damping due to the coupling to the sea of complicated states is neglected. As a
result, the formation of GR is governed by the interplay and competition of two
kinds of collectivity, the internal and the external one. The mixing of the
doorway components of a GR due to the external interaction influences
significantly their multipole strengths, widths and positions in energy. In
particular, a narrow resonance state with an appreciable multipole strength is
formed when the doorway components strongly overlap.


title: Hadronic Effects in the Pionium Ion

abstract:
  The hadronic properties of the pionium ion (Coulomb bound system of three
charged pions) are estimated using the results for the positronium ion
$P{s}^{-}$. It turns out that the hadronic shift of the ground state energy and
the lifetime of the pionium ion are approximately the same as for pionium.


title:
Interfering Doorway States and Giant Resonances. II: Transition
  Strengths

abstract:
  The mixing of the doorway components of a giant resonance (GR) due to the
interaction via common decay channels influences significantly the distribution
of the multipole strength and the energy spectrum of the decay products of the
GR. The concept of the partial widths of a GR becomes ambiguous when the mixing
is strong. In this case, the partial widths determined in terms of the $K$- and
$S$-matrices must be distinguished. The photoemission turns out to be most
sensitive to the overlapping of the doorway states. At high excitation
energies, the interference between the doorway states leads to a restructuring
towards lower energies and apparent quenching of the dipole strength.


title: Semileptonic decays of heavy mesons

abstract:
  The semileptonic and leptonic decays of heavy mesons are studied as a
phenomenological application and exploration of a heavy-quark limit of
Dyson-Schwinger equations. The single form factor, $\xi(w)$, which
characterises the semileptonic decay in this limit, is calculated and compares
well with recent experimental extractions. We obtain a lower bound of 1/3 on
the slope-parameter $\rho^2 \equiv -\xi^\prime(1)$, which, in calculations with
realistic input, is exceeded by a great deal: agreement with experimental data
requiring $\rho^2 \sim 1.2 - 1.6$. The flavour and momentum dependence of the
light-quark propagators has observable consequences.


title: Scaling Properties of Nuclear Giant Resonance Transition Probabilities

abstract:
  Multifractal scaling analysis of nuclear giant resonance transition
probability distributions is performed within the approximation which takes
into account the one-particle-one-hole (1p-1h) and 2p-2h states. A new measure
to determine the fractal dimensions of the spectra is introduced. It is found
that chaotic dynamics governing the decay leads to non-trivial multifractal
scaling properties. Such a kind of scaling is absent in the case of regular
dynamics. The degree of collectivity is another element which worsens the
scaling.


title: Bose-Einstein Weights for Event Generators

abstract:
  A simple new algorithm for the calculation of two-particle Bose-Einstein
correlations from classical event generators is derived and discussed.


title: Pion Double Charge Exchange on Nuclei and Inelastic Rescatterings

abstract:
  The inclusive pion double charge exchange process on nuclei is considered in
the framework of the Gribov-Glauber approach. It is shown that inelastic
rescatterings related to production of two (and more) pions in the intermediate
state give an important contribution to the process of double charge exchange
at kinetic energies above ~ 0.5 GeV. This mechanism dominates at energies
greater or about 1 GeV and allows to explain the weak energy dependence of the
double charge exchange cross section observed experimentally.


title: Proton polarizability contribution to hydrogen Lamb shift

abstract:
  The correction to the hydrogen Lamb shift due to the proton electric and
magnetic polarizabilities is expressed analytically through their static
values, which are known from experiment. The numerical value of the correction
is $ - 71 \pm 11 \pm 7$ Hz.


title: Momentum Distributions in Halo Nuclei

abstract:
  The halo nuclei $^6$He and $^8$He are described in a consistent way in a
microscopic multiconfiguration model, the refined resonating group method. The
ground state properties have been calculated, and momentum distributions of
fragments and neutrons have been determined in a simple reaction scenario,
taking into account final-state interactions. The correlation of neutrons and
fragments are investigated.


title:
Freeze-Out Time in Ultrarelativistic Heavy Ion Collisions from Coulomb
  Effects in Transverse Pion Spectra

abstract:
  The influence of the nuclear Coulomb field on transverse spectra of $\pi^+$
and $\pi^-$ measured in $Pb+Pb$ reactions at 158 A GeV has been investigated.
Pion trajectories are calculated in the field of an expanding fireball. The
observed enhancement of the $\pi^-/\pi^+$ ratio at small momenta depends on the
temperature and transverse expansion velocity of the source, the rapidity
distribution of the net positive charge, and mainly the time of the freeze-out.


title: Strangeness: Theoretical Status

abstract:
  Strangeness plays an important role in the study of quark matter since it
indicates the rate at which new particles are being produced and therefore
provides information about the degree of chemical equilibration reached in
heavy ion collisions. It is shown that ratios provide an excellent method for
determining the temperature and the chemical potential since many theoretical
uncertainties cancel out. All indications are that particle abundances are very
close to chemical equilibrium. The amount of strangeness present in $S-S$
collisions is very close to the one corresponding to chemical equilibrium.
Deviations are at the 30% level.


title: Naturalness in the quark-meson coupling model

abstract:
  The quark-meson coupling (QMC) model is examined using Georgi's ``naive
dimensional analysis''. We argue that the QMC model is quite natural as an
effective field theory for nuclei.


title:
Stochastic Time-Dependent Hartree-Fock for heavy-ion collisions in the
  Fermi energy domain

abstract:
  We present the first realization of Stochastic TDHF, a theory which goes
beyond pure mean-field dynamics, embracing dissipation as well as fluctuations.
Applications to heavy-ion collisions in the Fermi energy domain are given and
analyzed in terms of dissipative features and Intermediate Mass Fragment
production.


title:
Nuclear medium modifications of the NN interaction via quasielastic
  ($\vec p,\vec p '$) and ($\vec{p},\vec{n}$) scattering

abstract:
  Within the relativistic PWIA, spin observables have been recalculated for
quasielastic ($\vec p,\vec p '$) and ($\vec p,\vec n$) reactions on a $^{40}$Ca
target. The incident proton energy ranges from 135 to 300 MeV while the
transferred momentum is kept fixed at 1.97 fm^{-1}. In the present
calculations, new Horowitz-Love--Franey relativistic NN amplitudes have been
generated in order to yield improved and more quantitative spin observable
values than before. The sensitivities of the various spin observables to the NN
interaction parameters, such as (1) the presence of the surrounding nuclear
medium, (2) a pseudoscalar versus a pseudovector interaction term, and (3)
exchange effects, point to spin observables which should preferably be measured
at certain laboratory proton energies, in order to test current nuclear models.
This study also shows that nuclear medium effects become more important at
lower proton energies ($\leq$ 200 MeV). A comparison to the limited available
data indicates that the relativistic parametrization of the NN scattering
amplitudes in terms of only the five Fermi invariants (the SVPAT form) is
questionable.


title:
Neutron electromagnetic form factors and inclusive scattering of
  polarized electrons by polarized $^{3}$He and $^{3}$H targets

abstract:
  The electromagnetic inclusive responses of polarized $^{3}$He and $^{3}$H are
thoroughly investigated at the quasielastic peak for squared momentum transfers
up to $2 (GeV/c)^2$, within the plane wave impulse approximation. Great
emphasys is put on the effects in the bound-state due to different two- and
three-body nuclear forces, and to the Coulomb interaction as well. A careful
analysis of the polarized responses allows to select possible experiments for
minimizing the model dependence in the extraction of the neutron
electromagnetic form factors. In particular, the relevant role played by the
proton in the transverse-longitudinal response of polarized $^{3}$He, at low
momentum transfer, can be utilized for obtaining valuable information on the
proton contribution to the total polarized response and eventually on the
neutron charge form factor.


title: Space-time Characteristics of the Fireball from HBT Interferometry

abstract:
  We present the Yano-Koonin-Podgoretskii parametrisation of the correlation
function. Compared to the conventionally used Cartesian parametrisation, this
one provides more straightforward measurement of the duration of the emission
process in the fireball and a clearer signal of the longitudinal expansion,
which is expected in ulrarelativistic heavy ion collisions.


title: 3He Transport and the Question of Nonstandard Solar Models

abstract:
  I consider phenomenological changes in the standard solar model with the goal
of testing recent claims that the solar neutrino puzzle requires new particle
physics. The assumption of a steady-state sun producing the correct luminosity
and governed by standard microphysics appears to leave only one nonstandard
solar model possibility open, slow mixing of the solar core on timescales
characteristic of 3He equilibration. The conjecture of such mixing raises
striking physics issues connected with the standard model 3He instability and
the possibility that the 3He abundance gradient might allow the sun's early
convective core to persist. While helioseismology might eventually rule out
such a "model," contrary to one recent claim I will argue that the
helioseismology of a mixed two-fluid sun is as yet far from clear. Finally, I
conclude by stressing that 3He-driven slow mixing is not being proposed as a
solution of the solar neutrino problem, but as an example of a possibility that
has not been quantitatively modeled and yet could produce neutrino fluxes far
closer to experiment than the standard solar model. Thus, despite the
attractiveness of neutrino oscillation solutions, astrophysical explanations of
the solar neutrino problem are not yet, in my view, ruled out definitively.


title: Be7(p,gamma)B8 and the high-energy solar neutrino flux

abstract:
  The importance of the Be7(p,gamma)B8 reaction in predicting the high-energy
solar neutrino flux is discussed. I present a microscopic eight-body model and
a potential model for the calculation of the Be7(p,gamma)B8 cross section.


title: Importance of core polarization in halo nuclei

abstract:
  A comment on the importance of core polarization in halo nuclei. I point out
that although core polarization is suppressed in neutron halos, it plays an
essential role in their binding mechanism.


title:
A Simple Mode on a Highly Excited Background: Collective Strength and
  Damping in the Continuum

abstract:
  Simple states, such as isobaric analog states or giant resonances, embedded
into continuum are typical for mesoscopic many-body quantum systems. Due to the
coupling to compound states in the same energy range, a simple mode acquires a
damping width ("internal" dynamics). When studied experimentally with the aid
of various reactions, such states reveal enhanced cross sections in specific
channels at corresponding resonance energies ("external" dynamics which include
direct decay of a simple mode and decays of intrinsic compound states through
their own channels). We consider the interplay between internal and external
dynamics using a general formalism of the effective nonhermitian hamiltonian
and looking at the situation both from "inside" (strength functions and
spreading widths) and from "outside" (S-matrix, cross sections and delay
times). The restoration of isospin purity and disappearance of the collective
strength of giant resonances at high excitation energy are discussed as
important particular manifestations of this complex interplay.


title: Cross section and analyzing power of pol{p}p -> pn pi+ near threshold

abstract:
  The cross section and analyzing power of the pol{p}p -> pn pi+ reaction near
threshold are estimated in terms of data obtained from the pol{p}p -> d pi+ and
pp -> pp pi0 reactions. A simple final state interaction theory is developed
which depends weakly upon the form of the pion-production operator and includes
some Coulomb corrections. Within the uncertainties of the model and the input
data, the approach reproduces well the measured energy dependence of the total
cross section and the proton analyzing power at a fixed pion c.m. angle of
90deg, from threshold to T_p = 330 MeV. The variation of the differential cross
section with pion angle is also very encouraging.


title: Gauge-invariant theory of pion photoproduction with dressed hadrons

abstract:
  Based on an effective field theory of hadrons in which quantum chromodynamics
is assumed to provide the necessary bare cutoff functions, a gauge-invariant
theory of pion photoproduction with fully dressed nucleons is developed. The
formalism provides consistent dynamical descriptions of pi-N --> pi-N
scattering and Gamma-N --> pi-N production mechanisms in terms of nonlinear
integral equations for fully dressed hadrons. Defining electromagnetic currents
via the gauging of hadronic n-point Green's functions, dynamically detailed
currents for dressed nucleons are introduced. The dressed hadron currents and
the pion photoproduction current are explicitly shown to satisfy gauge
invariance in a self-consistent manner. Approximations are discussed that make
the nonlinear formalism manageable in practice and yet preserve gauge
invariance. This is achieved by recasting the gauge conditions for all
contributing interaction currents as continuity equations with ``surface''
terms for the individual particle legs coming into or going out of the hadronic
interaction region. General procedures are given that approximate any type of
(global) interaction current in a gauge-invariance preserving manner as a sum
of single-particle ``surface'' currents. It is argued that these prescriptions
carry over to other reactions, irrespective of the number or type of
contributing hadrons or hadronic systems.


title: Low-energy Pion-nucleon Scattering

abstract:
  This paper contains the results of an analysis of recent low-energy
pion-nucleon scattering experiments. Obtained are phase shifts, the
pion-nucleon coupling constant and an estimate of the Sigma term.


title: Perspective: Atomic Parity Violation and the Nuclear Anapole Moment

abstract:
  I discuss in qualitative terms the implications of the recent measurement by
C. S. Wood et al. of the hyperfine dependence of atomic parity violation in
133Cs. The derived anapole moment constrains the strength of hadronic parity
violation.


title: Symposium Summary and Outlook: Twenty Years of Meson Factory Physics

abstract:
  The opening of the meson factories twenty years ago provided nuclear physics
with new beams, higher momentum transfers, and new opportunities for precision
measurements. The resulting changes in nuclear physics were substantial,
altering not only the range of physics issues identified with the field but
also the manner and size of the collaborations that do nuclear physics.
Inspired by the talks of this symposium, I discuss some of the accomplishments
as well as some of the goals not yet reached.


title: Stability of bubble nuclei through Shell-Effects

abstract:
  We investigate the shell structure of bubble nuclei in simple
phenomenological shell models and study their binding energy as a function of
the radii and of the number of neutron and protons using Strutinsky's method.
Shell effects come about, on the one hand, by the high degeneracy of levels
with large angular momentum and, on the other, by the big energy gaps between
states with a different number of radial nodes. Shell energies down to -40 MeV
are shown to occur for certain magic nuclei. Estimates demonstrate that the
calculated shell effects for certain magic numbers of constituents are probably
large enough to produce stability against fission, alpha-, and beta-decay. No
bubble solutions are found for mass number A < 450.


title:
Breakup probabilities and the optical potential in elastic deuteron
  scattering

abstract:
  We investigate the effect of the deuteron breakup on the optical potential
for the elastic scattering of 56 MeV deuterons from $^{51}$V. The breakup
probabilities calculated within the post-form distorted wave Born-approximation
theory of breakup reactions are fitted to derive the contribution to the
optical potential from the breakup channels. The breakup potentials are found
to have large real as well as imaginary parts. Thus the dynamical polarization
potential due to the breakup process is expected to modify strongly the real
part of the optical potential calculated by the double folding model.


title: Parity conserving gamma asymmetry in n-p radiative capture

abstract:
  The importance of n-p radiative capture, utilizing polarized cold neutrons,
as a means of measuring the weak pion coupling constant is reviewed. Parity
conserving processes of the form k_gamma*[s_n,k_n] can contribute to the
s_n*k_gamma photon asymmetry in any such experiment, if the apparatus is not
perfectly symmetric. For an incident laboratory neutron energy of 0.003 eV a
value of A^{PC}_{gamma}=0.67*10^{-8} is obtained for two different potential
models (Argonne AV14 and Nijmegen Reid93). Serving as an extreme test case, the
Reid soft core potential yields 0.61*10^{-8}, close to the result of the
contemporary forces. Implications for extracting the weak pion coupling
constant and for monitoring the beam polarization are discussed.


title:
Structure analysis of the virtual Compton scattering amplitude at low
  energies

abstract:
  We analyze virtual Compton scattering off the nucleon at low energies in a
covariant, model-independent formalism.
  We define a set of invariant functions which, once the irregular nucleon pole
terms have been subtracted in a gauge-invariant fashion, is free of poles and
kinematical zeros.
  The covariant treatment naturally allows one to implement the constraints due
to Lorentz and gauge invariance, crossing symmetry, and the discrete
symmetries.
  In particular, when applied to the $ep\to e'p'\gamma$ reaction,
charge-conjugation symmetry in combination with nucleon crossing generates four
relations among the ten originally proposed generalized polarizabilities of the
nucleon.


title:
Microscopic Analysis of Thermodynamic Parameters from 160 MeV/n - 160
  GeV/n

abstract:
  Microscopic calculations of central collisions between heavy nuclei are used
to study fragment production and the creation of collective flow. It is shown
that the final phase space distributions are compatible with the expectations
from a thermally equilibrated source, which in addition exhibits a collective
transverse expansion. However, the microscopic analyses of the transient states
in the reaction stages of highest density and during the expansion show that
the system does not reach global equilibrium. Even if a considerable amount of
equilibration is assumed, the connection of the measurable final state to the
macroscopic parameters, e.g. the temperature, of the transient ''equilibrium''
state remains ambiguous.


title:
Relativistic Quantum Field Theory of High-Spin Matter Fields: A
  Pragmatic approach for Hadronic Physics

abstract:
  A consistent phenomenology of the interaction of particles of arbitrary spin
requires covariant spinors, field operators, propagators and model
interactions. Guided by an approach originally proposed by Weinberg, we
construct from group theoretical arguments the (j,0)+(0,j) covariant spinors
and the field operators for a massive particles. Specific examples are worked
out in the familiar language of the Bjorken and Drell text for the case of the
(1,0)+(0,1), (3/2,0)+(0,3/2) and (2,0)+(0,2) matter fields. The m\to 0 limit of
the covariant spinors is shown to have the expected structure. The algebra of
the \gamma^{\mu\nu} matrices associated with the (1,0)+(0,1) matter fields is
presented, and the conserved current derived. The procedure readily extends to
higher spins. The causality problem associated with the j\ge 1 wave equations
is discussed in detail and a systematic procedure to construct causal
propagators is provided. As an example a spin two wave equation satisfied by
the (2,0)+(0,2), covariant spinors is found to support not only ten correct and
causal solutions, but also thirty physically unacceptable acausal solutions.
However, we demonstrate how to construct the Feynman propagator for the higher
spin particles directly from the spinors and thus avoid the shortcomings of the
wave equation in building a phenomenology. The same exercise is repeated for
the (1,0)+(0,1) and (3/2,0)+(0,3/2) matter fields, and the same conclusions
obtained. Massless limit is discussed in detail. (Typos uncorrected, Part of
the work published and extended in several journal articles, for an important
correction see physics/9702005).


title: Probing the Structure of Halo Nuclei

abstract:
  Our understanding of halo nuclei has so far relied on high-energy scattering
and reactions, but a number of uncertainties remain. I discuss in general terms
the new range of observables which will be measured by experiments around the
Coulomb barrier, and how some details of the reaction mechanisms still need to
be clarified.


title: Halo Excitation of $^6$He in Inelastic and Charge-Exchange Reactions

abstract:
  Four-body distorted wave theory appropriate for nucleon-nucleus reactions
leading to 3-body continuum excitations of two-neutron Borromean halo nuclei is
developed. The peculiarities of the halo bound state and 3-body continuum are
fully taken into account by using the method of hyperspherical harmonics. The
procedure is applied for A=6 test-bench nuclei; thus we report detailed studies
of inclusive cross sections for inelastic $^6$He(p,p')$^6$He$^*$ and
charge-exchange $^6$Li(n,p)$^6$He$^*$ reactions at nucleon energy 50 MeV. The
theoretical low-energy spectra exhibit two resonance-like structures. The first
(narrow) is the excitation of the well-known $2^+$ three-body resonance. The
second (broad) bump is a composition of overlapping soft modes of
multipolarities $1^-, 2^+, 1^+, 0^+$ whose relative weights depend on
transferred momentum and reaction type. Inelastic scattering is the most
selective tool for studying the soft dipole excitation mode.


title: Neutrino-nucleus reactions on ^{12}C and ^{16}O

abstract:
  Exclusive and inclusive $(\nu_\mu, \mu^-), (\nu_e, e^-)$ cross-sections and
$\mu^-$-capture rates are calculated for ^{12}C and ^{16}O using the consistent
random phase approximation (RPA) and pairing model. After a pairing correction
is introduced to the RPA results the flux-averaged theoretical $(\nu_\mu,
\mu^-), (\nu_e, e^-)$ cross-sections and $\mu^-$-capture rates in $^{12}$C are
in good agreement with experiment. In particular when one takes into account
the experimental error bars, the recently measured range of values for the
$(\nu_\mu, \mu^-)$ cross-section is in agreement with the present theoretical
results. Predictions of $(\nu_\mu, \mu^-)$ and $(\nu_e, e^-)$ cross-sections in
^{16}O are also presented.


title:
Analysis of Photoreaction in the Delta Energy Region by the Quantum
  Molecular Dynamics Approach

abstract:
  We study the photoreaction in the delta energy region using the QMD approach.
The proton and pion cross-sections are calculated and compared with
experimental data. Through this work we examine the multistep contributions in
the cross-sections and the {$\pi - \Delta$} dynamics.


title: Relativistic Approach to Superfluidity in Nuclear Matter

abstract:
  Pairing correlations in symmetric nuclear matter are studied within a
relativistic mean-field approximation based on a field theory of nucleons
coupled to neutral ($\sigma$ and $\omega$) and to charged ($\varrho$) mesons.
The Hartree-Fock and the pairing fields are calculated in a self-consistent
way. The energy gap is the result of a strong cancellation between the scalar
and vector components of the pairing field. We find that the pair amplitude
vanishes beyond a certain value of momentum of the paired nucleons. This fact
determines an effective cutoff in the gap equation. The value of this cutoff
gives an energy gap in agreement with the estimates of non relativistic
calculations.


title:
Energy loss effects on charm and bottom production in high-energy
  heavy-ion collisions

abstract:
  We study the effect of energy loss on charm and bottom quarks in high-energy
heavy-ion collisions including longitudinal expansion and partial
thermalization. We find that high $p_\perp$ heavy quarks are greatly
suppressed, and consequently, high-mass dileptons from heavy quark decays are
also suppressed. We consider in detail the detector geometry and single lepton
energy cuts of the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). Because of the longitudinal expansion, the suppressions of $ee, e\mu$
and $\mu\mu$ pairs resulting from the heavy quark energy loss are very
different due to the different rapidity coverages and energy cuts. The assumed
energy loss rate, on the order of 1 GeV/fm, results in a large suppression on
dielectrons, and dielectrons from heavy quark decays become comparable or even
lower than the Drell-Yan yield. It is thus possible to probe the energy loss
rate of the medium using dileptons from heavy quark decays.


title: Low-energy Antiproton Interaction with Helium

abstract:
  An ab initio potential for the interaction of the neutral helium atom with
antiprotons and protons is calculated using the Born-Oppenheimer approximation.
Using this potential, the annihilation cross section for antiprotons in the
energy range 0.01 microvolt to 1 eV is calculated.


title: Model study of hot and dense baryonic matter

abstract:
  The properties of baryonic matter have been investigated at finite density
and temperature using different models. The variation of baryon masses and
fractional number densities with baryon density and temperature obtained from
different models have been compared. The quark hadron phase transition have
been studied using Chiral Colour Dieletric (CCD) model in the quark sector. No
phase transition has been seen for the different variants of the
Zimanyi-Moszkowski model. However, a phase transition is observed for the
linear and non-linear Walecka model.


title: Quantum Monte Carlo calculations of nuclei with A \leq 7

abstract:
  We report quantum Monte Carlo calculations of ground and low-lying excited
states for nuclei with A \leq 7 using a realistic Hamiltonian containing the
Argonne v18 two-nucleon and Urbana IX three-nucleon potentials. A detailed
description of the Green's function Monte Carlo algorithm for systems with
state-dependent potentials is given and a number of tests of its convergence
and accuracy are performed. We find that the Hamiltonian being used results in
ground states of both 6Li and 7Li that are stable against breakup into
subclusters, but somewhat underbound compared to experiment. We also have
results for 6He, 7He, and their isobaric analogs. The known excitation spectra
of all these nuclei are reproduced reasonably well and we predict a number of
excited states in 6He and 7He. We also present spin-polarized one-body and
several different two-body density distributions. These are the first
microscopic calculations that directly produce nuclear shell structure from
realistic interactions that fit NN scattering data.


title:
Generalized polarizabilities of the nucleon studied in the linear sigma
  model (II)

abstract:
  In a previous paper virtual Compton scattering off the nucleon has been
investigated in the one-loop approximation of the linear sigma model in order
to determine the 3 scalar generalized polarizabilities. We have now extended
this work and calculated the 7 vector polarizabilities showing up in the
spin-dependent amplitude of virtual Compton scattering. The results fulfill 3
model-independent constraints recently derived. Compared to the constituent
quark model there exist enormous differences for some of the vector
polarizabilities. At vanishing three-momentum of the virtual photon, the
analytical results of the sigma model and of chiral perturbation theory can be
related. The influence of the $\pi^{0}$ exchange in the $t$ channel has been
discussed in some detail. Besides, the vector polarizabilities determine 2
linear combinations of the third order spin-polarizabilities appearing in real
Compton scattering.


title: Effective Q-Q Interactions in Constituent Quark Models

abstract:
  We study the performance of some recent potential models suggested as
effective interactions between constituent quarks. In particular, we address
constituent quark models for baryons with hybrid Q-Q interactions stemming from
one-gluon plus meson exchanges. Upon recalculating two of such models we find
them to fail in describing the N and \Delta spectra. Our calculations are based
on accurate solutions of the three-quark systems in both a variational
Schr\"odinger and a rigorous Faddeev approach. It is argued that hybrid {Q-Q}
interactions encounter difficulties in describing baryon spectra due to the
specific contributions from one-gluon and pion exchanges together. In contrast,
a chiral constituent quark model with a Q-Q interaction solely derived from
Goldstone-boson exchange is capable of providing a unified description of both
the N and \Delta spectra in good agreement with phenomenology.


title:
Momentum Dependence of Single Particle Potential in Dirac Brueckner
  Approach

abstract:
  The momentum dependence of the empirical scalar and vector potentials needed
for describing relativistic heavy-ion collisions at 1 GeV/nucleon is compared
with that derived from self-consistent Dirac-Brueckner calculations using the
Bonn-A potential. Our calculated scalar and vector potentials exhibit a weak
momentum dependence and their magnitudes decrease with nucleon momentum, in
close similarity with the momentum dependence required by the empirical
potentials. The effects of explicit momentum dependence on the properties of
equilibrium nuclear matter are found to be small.


title: Spin-Isospin Structure and Pion Condensation in Nucleon Matter

abstract:
  We report variational calculations of symmetric nuclear matter and pure
neutron matter, using the new Argonne v18 two-nucleon and Urbana IX
three-nucleon interactions. At the equilibrium density of 0.16 fm^-3 the
two-nucleon densities in symmetric nuclear matter are found to exhibit a
short-range spin-isospin structure similar to that found in light nuclei. We
also find that both symmetric nuclear matter and pure neutron matter undergo
transitions to phases with pion condensation at densities of 0.32 fm^-3 and 0.2
fm^-3, respectively. Neither transtion occurs with the Urbana v14 two-nucleon
interaction, while only the transition in neutron matter occurs with the
Argonne v14 two-nucleon interaction. The three-nucleon interaction is required
for the transition to occur in symmetric nuclear matter, whereas the the
transition in pure neutron matter occurs even in its absence. The behavior of
the isovector spin-longitudinal response and the pion excess in the vicinity of
the transition, and the model dependence of the transition are discussed.


title: Exact Baryon, Strangeness and Charge Conservation in Hadronic Gas Models

abstract:
  Relativistic heavy ion collisions are studied assuming that particles can be
described by a hadron gas in thermal and chemical equilibrium. The exact
conservation of baryon number, strangeness and charge are explicitly taken into
account. For heavy ions the effect arising from the neutron surplus becomes
important and leads to a substantial increase in e.g. the $\pi^-/\pi^+$ ratio.
A method is developed which is very well suited for the study of small systems.


title:
Hydrodynamics of nuclear collisions with initial conditions from
  perturbative QCD

abstract:
  We compute the longitudinal hydrodynamic flow in ultrarelativistic heavy ion
collisions at $\sqrt{s}$ = 5500 GeV by using boost non-invariant initial
conditions following from perturbative QCD. The transfer of entropy and energy
from the central region to larger rapidities caused by boost non-invariance is
determined and the associated decrease in the lifetime of the system is
estimated.


title: Sub-threshold resonances in few-neutron systems

abstract:
  Three- and four-neutron systems are studied within the framework of the
hyperspherical approach with a local S-wave nn-potential. Possible bound and
resonant states of these systems are sought as zeros of three- and four-body
Jost functions in the complex momentum plane. It is found that zeros closest to
the origin correspond to sub-threshold (nnn) (1/2-) and (nnnn) (0+) resonant
states. The positions of these zeros turned out to be sensitive to the choice
of the $nn$--potential. For the Malfliet- Tjon potential they are
E(nnn)=-4.9-i6.9 (MeV) and E(nnnn)=-2.6-i9.0 (MeV). Movement of the zeros with
an artificial increase of the potential strength also shows an extreme
sensitivity to the choice of potential. Thus, to generate ^3n and ^4n bound
states, the Yukawa potential needs to be multiplied by 2.67 and 2.32
respectively, while for the Malfliet-Tjon potential the required multiplicative
factors are 4.04 and 3.59.


title: How to count nucleon pairs?

abstract:
  Within the context of the isovector-pairing SO(5) model, three methods
measuring numbers of different kinds of nucleon pairs are discussed. Though
methods do not give the same results, the odd-even staggering in pair numbers
in even-even and odd-odd N=Z nuclei and the reduction of the np pair number
with increasing T_z is observed in all three procedures.


title: Hadron Physics from the Global Color Model of QCD

abstract:
  We review recent progress in modeling the quark-gluon content of mesons and
their low-energy interactions through the Global Color Model field theory. An
emphasis is placed on techniques that are shared with the approach based on
truncations of the Dyson-Schwinger equations of QCD. In contrast to most other
field theory models for QCD degrees of freedom in hadron physics, this approach
directly deals with the derived intrinsic space-time extent of the meson modes
in their role as field variables and can accommodate confinement as well as
dynamical breaking of chiral symmetry. Various theoretical techniques and
approximations found useful in this approach are described. Selected
applications reviewed here include the properties and interactions of the
Goldstone bosons, interaction vertex functions, low energy chiral observables,
electromagnetic interactions and form factors, and transition form factors.
Some initial considerations of Vector Meson Dominance and pion loop processes
are discussed.


title: Hadron structure effect in finite nuclei

abstract:
  The quark-meson coupling model, based on a mean-field description of
non-overlapping nucleon bags bound by the self-consistent exchange of $\sigma$,
$\omega$ and $\rho$ mesons, is reviewed. In particular, I present the changes
in the hadron masses of the (non-strange) vector mesons and the nucleon in a
nucleus. I also give a new, simple scaling relation among the changes of the
hadron masses.


title: A Hartree-Bose Mean-Field Approximation for IBM-3

abstract:
  A Hartree-Bose mean-field approximation for the IBM-3 is presented. A
Hartree- Bose transformation from spherical to deformed bosons with
charge-dependent parameters is proposed which allows bosonic pair correlations
and includes higher angular momentum bosons. The formalism contains previously
proposed IBM-2 and IBM-3 intrinsic states as particular limits.