title: Compton Scattering on the Deuteron in Baryon Chiral Perturbation Theory

abstract:
  Compton scattering on the deuteron is studied in the framework of baryon
chiral perturbation theory to third order in small momenta, for photon energies
of order the pion mass. The scattering amplitude is a sum of one- and
two-nucleon mechanisms with no undetermined parameters. Our results are in good
agreement with existing experimental data, and a prediction is made for
higher-energy data being analyzed at SAL.


title:
Effects of spinor distortion and density-dependent form factors upon
  $^{16}O(\vec{e},e'\vec{p})$

abstract:
  We propose an effective current operator for nucleon electromagnetic knockout
that incorporates spinor distortion and density-dependent nucleon form factors
using an effective momentum approximation. This method can be used in a
coordinate-space approach with either relativistic or nonrelativistic optical
potentials and overlap functions. We studied these effects for the
$^{16}O(\vec{e},e' \vec{p})$ reaction at Q^2 = 0.8 (GeV/c)^2. Spinor distortion
substantially enhances the left-right asymmetry while reducing the ratio
between sideways and longitudinal recoil polarization for p-shell knockout by
about 5% for modest missing momenta. We also find that the density dependence
of nucleon form factors suggested by a quark-meson coupling model reduces the
polarization ratio further. Much larger effects are obtained for the s-shell
than for p-shell. However, both effects are subject to much larger Gordon
ambiguities than comparable nonrelativistic calculations.


title: Quark Dynamics on Phase Space

abstract:
  We discuss the dynamics of quarks within a Vlasov approach. We use an
interquark ($qq$) potential consistent with the indications of Lattice QCD
calculations and containing a Coulomb term, a confining part and a spin
dependent term. Hadrons masses are shown to arise from the interplay of these
three terms plus the Fermi motion and the finite masses of the quarks.
  The approach gives a lower and an upper bound for hadrons. The theoretical
predictions are shown to be in fairly good agreement with the experimental
data.


title: Compton Scattering by Nuclei

abstract:
  The concept of Compton scattering by even-even nuclei from giant-resonance to
nucleon-resonance energies and the status of experimental and theoretical
researches in this field are outlined. Nuclear Compton scattering in the
giant-resonance energy-region provides information on the dynamical properties
of the in-medium mass of the nucleon. The electromagnetic polarizabilities of
the nucleon in the nuclear medium can be extracted from nuclear Compton
scattering data obtained in the quasi-deuteron energy-region. Recent results
are presented for two-body effects due to the mesonic seagull amplitude and due
to the excitation of nucleon internal degrees of freedom accompanied by meson
exchanges. Due to these studies the in-medium electromagnetic polarizabilities
are by now well understood, whereas the understanding of nuclear Compton
scattering in the Delta-resonance range is only at the beginning.
Phenomenological methods how to include retardation effects in the scattering
amplitude are discussed and compared with model predictions.


title: The Long and Short of Nuclear Effective Field Theory Expansions

abstract:
  Nonperturbative effective field theory calculations for NN scattering seem to
break down at rather low momenta. By examining several toy models, we clarify
how effective field theory expansions can in general be used to properly
separate long- and short-range effects. We find that one-pion exchange has a
large effect on the scattering phase shift near poles in the amplitude, but
otherwise can be treated perturbatively. Analysis of a toy model that
reproduces 1S0 NN scattering data rather well suggests that failures of
effective field theories for momenta above the pion mass can be due to
short-range physics rather than the treatment of pion exchange. We discuss the
implications this has for extending the applicability of effective field
theories.


title: Resonance Transport and Kinetic Entropy

abstract:
  Within the real-time formulation of nonequilibrium field theory, generalized
transport equations are derived avoiding the standard quasiparticle
approximation. They permit to include unstable particles into the transport
scheme. In order to achieve a self-consistent, conserving and thermodynamically
consistent description, we generalize the Baym's $\Phi$-functional method to
genuine nonequilibrium processes. The developed transport description naturally
includes all those quantum features already inherent in the corresponding
equilibrium limit. Memory effects appearing in collision term diagrams of
higher order are discussed. The variational properties of $\Phi$-functional
permit to derive a generalized expression for the non-equilibrium kinetic
entropy flow, which includes fluctuations and mass width effects. In special
cases an $H$-theorem is demonstrated implying that the entropy can only
increase with time. Memory effects in the kinetic terms provide corrections to
the kinetic entropy flow that in equilibrium limit recover the famous bosonic
type $T^3 \ln T$ correction to the specific heat of Fermi liquids like
Helium-3.

categories: nucl-th astro-ph cond-mat.stat-mech hep-ph


title:
Complete Sets of Polarization Observables in Electromagnetic Deuteron
  Break-up

abstract:
  For deuteron photo- and electrodisintegration the selection of complete sets
of polarization observables is discussed in detail by applying a recently
developed new criterion for the check of completeness of a chosen set of
observables. The question of ambiguities and their resolution by considering
additional observables is discussed for a numerical example, for which the role
of experimental uncertainties is also investigated. Furthermore, by inversion
of the expressions of the observables as hermitean forms in the $t$-matrix
elements a bilinear term of the form $t_{j'}^*t_j$ can be given as a complex
linear form in the observables from which an explicit solution for $t_j$ in
terms of observables can be obtained. These can also be used to select sets of
observables for the explicit representation of the $t$-matrix.


title:
Quaiselastic scattering from relativistic bound nucleons:
  Transverse-Longitudinal response

abstract:
  Predictions for electron induced proton knockout from the $p_{1/2}$ and
$p_{3/2}$ shells in $^{16}$O are presented using various approximations for the
relativistic nucleonic current. Results for the differential cross section,
transverse-longitudinal response ($R_{TL}$) and left-right asymmetry $A_{TL}$
are compared at $|Q^2|=0.8$ (GeV/c)$^2$ corresponding to TJNAF experiment
89-003. We show that there are important dynamical and kinematical relativistic
effects which can be tested by experiment.


title:
Continuum effects for the mean-field and pairing properties of weakly
  bound nuclei

abstract:
  Continuum effects in the weakly bound nuclei close to the drip-line are
investigated using the analytically soluble Poschl-Teller-Ginocchio potential.
Pairing correlations are studied within the Hartree-Fock-Bogoliubov method. We
show that both resonant and non-resonant continuum phase space is active in
creating the pairing field. The influence of positive-energy phase space is
quantified in terms of localizations of states within the nuclear volume.


title: Relativistic Faddeev approach to the NJL model at finite density

abstract:
  We study the nucleon solution of the relativistic Faddeev equation as a
function of density in the framework of a generalized Nambu-Jona-Lasinio model.
We truncate the interacting two-body channels to the scalar diquark channel,
the coupling constant of which is treated as a parameter. A 3-momentum cut-off
is used to regularize the model. The Faddeev equation is solved numerically
using the methods developed by Tjon and others. At zero density the nucleon is
bound only for unrealistically large values of the scalar coupling and this
binding energy decreases quickly with increasing density.


title: Quark rotation asymmetry and baryon magnetic moments

abstract:
  Quark rotation asymmetry is proposed in calculating baryon magnetic moments.
After taking into account interactions enforced on constituent quarks, assumed
to be linear and Coulomb potentials, respectively, and the quark rotation
asymmetry, we fit the theoretical values, based on two more hypotheses and
several other reasonable assumptions, of baryon magnetic moments with those
from experiments. The good fitting results show the necessity of the
consideration of quark rotation asymmetry within baryon.


title: $\Delta\pi N$ coupling constant in light cone QCD sum rules

abstract:
  We employ the light cone QCD sum rules to calculate $\Delta\pi N$ coupling
constant by studying the two point correlation function between the vacuum and
the pion state. Our result is consistent with the traditional QCD sum rules
calculations and it is in agreement with the experimental value.


title:
Relativistic effects in electromagnetic nuclear responses in the
  quasi-elastic delta region

abstract:
  A new non-relativistic expansion in terms of the nucleon's momentum inside
nuclear matter of the current for isobar electro-excitation from the nucleon is
performed. Being exact with respect to the transferred energy and momentum,
this yields new current operators which retain important aspects of relativity
not taken into account in the traditional non-relativistic reductions. The
transition current thus obtained differs from the leading order of the
traditional expansion by simple multiplicative factors. These depend on the
momentum and energy transfer and can be easily included together with
relativistic kinematics in non-relativistic, many-body models of isobar
electro-excitation in nuclei. The merits of the new current are tested by
comparing with the unexpanded electromagnetic nuclear responses in the isobar
peak computed in a relativistic Fermi gas framework. The sensitivity of the
relativistic responses to the isobar's magnetic, electric and Coulomb form
factors and the finite width of the isobar is analyzed.


title: Effective Theory for Neutron-Deuteron Scattering and the Triton

abstract:
  We apply the effective field theory approach to the three-nucleon system. In
particular, we consider neutron-deuteron scattering and the triton. Precise
predictions for S=3/2 scattering are obtained in a straightforward way. In the
S=1/2 channel, however, a unique nonperturbative renormalization takes place
which requires the introduction of a three-body force at leading order. We also
show that invariance under the renormalization group explains some universal
features of the three-nucleon system.


title:
High energy solar neutrinos and p-wave contributions to
  ^3He(p,\nue^+)^4He

abstract:
  High energy solar neutrinos can come from the hep reaction ^3He(p,\nue^+)^4He
with a large end point energy of 18.8 MeV. Understanding the hep reaction may
be important for interpreting solar neutrino spectra. We calculate the
contribution of the axial charge transition $^3P_0\to ^1S_0$ to the hep
thermonuclear S factor using a one-body reaction model involving a nucleon
moving in optical potentials. Our result is comparable to or larger than
previous calculations of the s-wave Gamow Teller contribution. This indicates
that the hep reaction may have p-wave strength leading to an enhancement of the
S factor.


title: Differential flow in heavy-ion collisions at balance energies

abstract:
  A strong differential transverse collective flow is predicted for the first
time to occur in heavy-ion collisions at balance energies. We also give a novel
explanation for the disappearance of the total transverse collective flow at
the balance energies. It is further shown that the differential flow especially
at high transverse momenta is a useful microscope capable of resolving the
balance energy's dual sensitivity to both the nuclear equation of state and
in-medium nucleon-nucleon cross sections in the reaction dynamics.


title: Coherence Effects and Neutrino Pair Bremsstrahlung in Neutron Stars

abstract:
  We calculate the rate of energy radiation by bremsstrahlung of neutrino pairs
by baryons in neutron stars employing a transport model in which neutrinos
couple to baryons with spectral width. The coherence effects, which are
included by computing the self energies with fully dressed propagators, lead to
the Landau-Pomeranchuk-Migdal suppression of the neutrino emission rates in the
soft neutrino and high temperature limit. A microscopic evaluation of the
bremsstrahlung rate by neutrons is carried out using the Brueckner theory of
nuclear matter at finite temperatures.


title: Matter-induced omega -> pi pi decay

abstract:
  We calculate the width for the omega -> pi pi decay in nuclear matter in a
hadronic model including mesons, nucleons and Delta isobars. We find a
substantial width of the longitudinally polarized omega modes, reaching ~100MeV
for mesons moving suitably fast with respect to the nuclear medium.


title: On the q-deformation of the NJL model

abstract:
  Using a q-deformed fermionic algebra we perform explicitly a deformation of
the Nambu-Jona-Lasinio (NJL) Hamiltonian. In the Bogoliubov-Valatin approach we
obtain the deformed version of the functional for the total energy, which is
minimized to obtain the corresponding gap equation. The breaking of chiral
symmetry and its restoration in the limit $q \to 0$ are then discussed.


title: Can Nuclear Decay constant be Modified ?

abstract:
  The life-time of $^{133}Cs$ in the first excited state has been measured with
the M\"ossbauer method by placing the absorber, CsCl, between two parallel flat
plates and the gamma-ray source, Ba^*TiO_3, in the free space. The result is
9.37 \pm 0.19 ns, which is 49 percent larger than the standard value 6.27 \pm
0.02 ns.


title: The piNN vertex function in a meson-theoretical model

abstract:
  The piNN vertex function is calculated within a dispersion theoretical
approach, including both pi-rho and pi-sigma intermediate states, where the
sigma meson is an abbreviation for a correlated pion pair in a relative S-wave
with isospin I=0. A strong coupling between the pi-sigma and the pi-rho states
is found. This leads to a softening of the piNN form factor. In a monopole
parameterization, a cut-off Lambda=800 MeV is obtained as compared to
Lambda=1000 MeV using pi-rho intermediate states only.


title: Probing nucleon strangeness structure with phi electroproduction

abstract:
  We study the possibility to constrain the hidden strangeness content of the
nucleon by means of the polarization observables in phi meson
electroproduction. We consider the OZI evading direct knockout mechanism that
arises from the non-vanishing s\bar{s} sea quark admixture of the nucleon as
well as the background of the dominant diffractive and the one-boson-exchange
processes. Large sensitivity on the nucleon strangeness are found in several
beam-target and beam-recoil double polarization observables. The small \sqrt{s}
and W region, which is accesible at some of the current high-energy electron
facilities, is found to be the optimal energy region for extracting out the OZI
evasion process.


title: Phenomenological spin-orbit three-body force

abstract:
  In order to improve the description of the N-d vector analyzing powers Ay and
iT11 (the so-called Ay puzzle) a spin-orbit three-body force has been
introduced. The L.S term in the NN potential has been modified including a
two-parameter three-body function depending on the hyperradius \rho. The
modification has been performed in channels where the pair nucleons (i,j) are
coupled to spin Sij=1 and isospin Tij=1. Calculations have been done in the
energy region from Elab=648 keV up to Elab=10 MeV. A noticeable improvement in
the description of the polarization observables has been obtained


title: Photoproduction of scalar mesons on protons and nuclei

abstract:
  We study the photoproduction of scalar mesons close to the threshold of
f_0(980) and a_0(980) using a unitary chiral model. Peaks for both resonances
show up in the invariant mass distributions of pairs of pseudoscalar mesons. A
discussion is made on the photoproduction of these resonances in nuclei, which
can shed light on their nature, a subject of continuous debate.


title:
(j,0)+(0,j) Covariant spinors and causal propagators based on Weinberg
  formalism

abstract:
  A pragmatic approach to constructing a covariant phenomenology of the
interactions of composite, high-spin hadrons is proposed. Because there are no
known wave equations without significant problems, we propose to construct the
phenomenology without explicit reference to a wave equation. This is done by
constructing the individual pieces of a perturbation theory and then utilizing
the perturbation theory as the definition of the phenomenology. The covariant
spinors for a particle of spin $j$ are constructed directly from Lorentz
invariance and the basic precepts of quantum mechanics following the logic put
forth originally by Wigner and developed by Weinberg. Explicit expressions for
the spinors are derived for j=1, 3/2 and 2. Field operators are constructed
from the spinors and the free-particle propagator is derived from the vacuum
expectation value of the time-order product of the field operators. A few
simple examples of model interactions are given. This provides all the
necessary ingredients to treat at a phenomenological level and in a covariant
manner particles of arbitrary spin.


title:
Structure of Excited States of 10Be studied with Antisymmetrized
  Molecular Dynamics

abstract:
  We study structure of excited states of 10Be with the method of variation
after spin parity projection in the framework of antisymmetrized molecular
dynamics. Present calculations describe many excited states and reproduce the
experimental data of E2 and E1 transitions and the new data of the $\beta$
transition strength successfully. We make systematic discussions on the
molecule-like structures of light unstable nuclei and the important role of the
valence neutrons based on the results obtained with the framework which is free
from such model assumptions as the existence of inert cores and clusters.


title:
Eta and eta-prime meson production in the reaction pn -> dM near
  threshold

abstract:
  The two-step model with pi-, rho- and omega- exchanges taken into account is
applied to investigate the reactions pn -> d eta and pn -> d eta-prime. The
existing experimental data on the reaction pn -> d eta are analysed and
predictions for the cross section of the reaction pn -> d eta-prime are
presented. It is found that pi- as well as rho exchange yield significant
contributions in both reactions. The effect of the final state interaction is
also studied.


title: Gamma-Deuteron Scattering

abstract:
  We discuss a recent computation of Compton scattering on the deuteron at
photon energies of order the pion mass. An interaction kernel is computed in
baryon chiral perturbation theory and sewn to phenomenological deuteron wave
functions. As an appetizer, we consider a computation of the pion-deuteron
scattering length using this method.


title: Deuteron production and space-momentum correlations at RHIC

abstract:
  We present predictions for the formation of (anti)nuclear bound states in
Au+Au central collisions at $\sqrt{s}=200A$ GeV. The coalescence afterburner
was applied to the freeze-out phase space distributions of nucleons provided by
the transport model, RQMD version 2.4. We study the sensitivity of the deuteron
spectra to space-momentum correlations. It is found that the deuteron
transverse momentum distributions are strongly affected by the nucleon
space-momentum correlations.


title: Scalar-isoscalar mesons in pion production at threshold

abstract:
  We present the contributions of the non-linear chiral scalar field S to cross
sections of $pp\to d\pi ^{+}, pp\to pn\pi ^{+}$ and $pp\to pp\pi ^0$ reactions
at threshold. We compare our results with the meson $\sigma$ contribution from
the $\sigma$-linear model. We show that the chiral scalar field S is almost 5
times bigger than the other contributions, which indicates that the two-pion
exchange dynamics embebbed in the S field is the most important term for the
pion production at threshold.


title:
Shape and blocking effects on odd-even mass differences and rotational
  motion of nuclei

abstract:
  Nuclear shapes and odd-nucleon blockings strongly influence the odd-even
differences of nuclear masses. When such effects are taken into account, the
determination of the pairing strength is modified resulting in larger pair
gaps. The modified pairing strength leads to an improved self-consistent
description of moments of inertia and backbending frequencies, with no
additional parameters.


title: Large $p_t$ enhancement from freeze out

abstract:
  Freeze out of particles across three dimensional space-time hypersurface is
discussed in a simple kinetic model. The final momentum distribution of emitted
particles, for freeze out surfaces with space-like normal, shows a
non-exponential transverse momentum spectrum. The slope parameter of the $p_t$
distribution increases with increasing $p_t$, in agreement with recently
measured SPS pion and $h^-$ spectra.


title: Canonical and Microcanonical Distributions for Fermi Systems

abstract:
  Recursion relations are presented that allow exact calculation of canonical
and microcanonical partition functions of degenerate Fermi systems, assuming no
explicit two-body interactions. Calculations of the level density, sorted by
angular momentum, are presented for Ni-56 are presented. The issue of treating
unbound states is also addressed.


title: Bethe-Salpeter Study of Vector Meson Masses and Decay Constants

abstract:
  The masses and decay constants of the light vector mesons $\rho/\omega$,
$\phi$ and $K^\star$ are studied within a ladder-rainbow truncation of the
coupled Dyson-Schwinger and Bethe-Salpeter equations of QCD with a model
2-point gluon function. The approach is consistent with quark and gluon
confinement, reproduces the correct one-loop renormalization group behavior of
QCD, generates dynamical chiral symmetry breaking, and preserves the relevant
Ward identities. The one phenomenological parameter and two current quark
masses are fixed by requiring that the calculated $f_\pi, m_\pi$ and $m_K$ are
correct. The resulting $f_K$ is within 3% of the experimental value. For the
vector mesons, all eight transverse covariants are included and the dominant
ones are identified; the complete angle dependence of the amplitudes is also
retained. The calculated values for the masses $m_\rho, m_\phi$ and
$m_{K^\star}$ are within 5%, while the decay constants $f_\rho, f_\phi$ and
$f_{K^\star}$ for electromagnetic and leptonic decays are within 10% of the
experimental values.


title:
Pairing and shell effects in the transport coefficients of collective
  motion

abstract:
  The linear response approach to nuclear transport has been extended to pair
correlations. The latter are treated within a mean field approximation to a
pairing interaction with constant matrix elements $G$. The constraint of
particle number conservation has been accounted for on a time dependent
average, which leads to modified response functions, both in the pairing degree
of freedom as well as in the shape variable. The former is expressed by the gap
parameter $\Delta$ and the latter by a $Q$ which specifies the elongation of a
fissioning nucleus. The tensors for friction and inertia corresponding to these
two collective coordinates are computed along the fission path of $^{224}Th$
for temperatures around $T=1 \mev$ and less. It is seen that dissipation
decreases with decreasing temperature and increasing pairing gap and falls well
below the values of common "macroscopic models". Both friction and inertia show
a sensible dependence on the configurations of the mean field caused both by
shell effects as well as by avoided crossings of single-particle levels.


title:
Symmetry conserving non-perturbative s-wave renormalization of the pion
  in hot and baryon dense medium

abstract:
  A non-perturbative s-wave renormalization of the pion in a hot and baryon
rich medium is presented. This approach proceeds via a mapping of the canonical
pion into the axial Noether's charge. The mapping was made dynamical in the
Hartree-Fock-Bogoliubov random phase approximation (HFB-RPA). It is shown that
this approach, while order mixing, is still symmetry conserving both in the
baryon free and baryon rich sectors, at zero as well as finite temperature. The
systematic character of this approach is emphasized and it is particularly
argued that it may constitute an interesting alternative for the
non-perturbative assessment of the nuclear matter saturation properties.


title:
Elastic and Inelastic Neutrino-Deuteron Scattering in Effective Field
  Theory

abstract:
  The differential cross-sections for elastic and inelastic neutrino-deuteron
scattering are calculated analytically using nucleon-nucleon effective field
theory. For elastic scattering, the deuteron axial form factor and the deuteron
strange magnetic moment form factor are computed to next-to-leading order,
including two-body currents. For inelastic scattering, two neutral current
processes nu+d->nu+n+p, nubar+d->nubar+n+p and one charged current process
nubar+d->(e^+)+n+n are computed to next-to-leading order. These depend on an
isovector axial two-body matrix element whose value is yet to be fixed by
experiment. Potential model calculations by Kubodera et al. and Ying et al. are
reproduced for different values of the two-body matrix element. This implies
that the differences between the two potential model calculations lie in their
treatment of short distance physics. The charged current to neutral current
nubar-d cross-section ratio is confirmed to be insensitive to short distance
physics, and the same ratio is obtained by potential models and the calculation
presented here, within 5%, for incident incident neutrino energies up to 20
MeV. The two-body matrix element could be fixed using the parity violating
process epol+d->e+n+p.


title: Superscaling of Inclusive Electron Scattering from Nuclei

abstract:
  We investigate the degree to which the concept of superscaling, initially
developed within the framework of the relativistic Fermi gas model, applies to
inclusive electron scattering from nuclei. We find that data obtained from the
low energy loss side of the quasielastic peak exhibit the superscaling
property, i.e., the scaling functions f(\psi') are not only independent of
momentum transfer (the usual type of scaling: scaling of the first kind), but
coincide for A \geq 4 when plotted versus a dimensionless scaling variable
\psi' (scaling of the second kind). We use this behavior to study as yet poorly
understood properties of the inclusive response at large electron energy loss.


title: Shell model studies of the proton drip line nucleus $^{106}$Sb

abstract:
  We present results of shell model calculations for the proton drip line
nucleus $^{106}$Sb. The shell model calculations were performed based on an
effective interaction for the $2s1d0g_{7/2}0h11_{11/2}$ shells employing modern
models for the nucleon-nucleon interaction. The results are compared with the
recently proposed experimental yrast states. A good agreement with experiment
is found lending support to the experimental spin assignements.


title: Lorentz covariance of three-dimensional equations

abstract:
  We show how the invariance under the charge conjugation and CPT symmetry,
present in the Bethe-Salpeter equation, is lost in the reduction to certain
relativistic three-dimensional equations. This in particular leads to the
breakdown of the standard Lorentz structure and renormalization procedures for
the resulting single-particle propagators. We formulate the equal-time
approximation of the Bethe-Salpeter equation in the form which manifestly
satisfies the above symmetries, and apply it to the description of the
pion-nucleon interaction in a dynamical model based on hadron exchanges. We
also consider the one-body limit of various three-dimensional equations for the
case of $t$- and $u$-channel one-particle-exchange potential.


title: Effects of Nonlocal One-Pion-Exchange Potential in Deuteron

abstract:
  The off-shell aspects of the one-pion-exchange potential (OPEP) are
discussed. Relativistic Hamiltonians containing relativistic kinetic energy,
relativistic OPEP with various off-shell behaviors and Argonne $v_{18}$
short-range parameterization are used to study the deuteron properties. The
OPEP off-shell behaviors depend on whether a pseudovector or pseudoscalar
pion-nucleon coupling is used and are characterized by a parameter $\mu$. We
study potentials having $\mu$=-1, 0 and +1 and we find that they are nearly
unitarily equivalent. We also find that a nonrelativistic Hamiltonian
containing local potentials and nonrelativistic kinetic energy provides a good
approximation to a Hamiltonian containing a relativistic OPEP based on
pseudovector pion-nucleon coupling and relativistic kinetic energy.


title:
Constituent quark model for baryons with strong quark-pair correlations
  and non-leptonic weak transitions of hyperon

abstract:
  We study the roles of quark-pair correlations for baryon properties, in
particular on non-leptonic weak decay of hyperons. We construct the quark wave
function of baryons by solving the three body problem explicitly with
confinement force and the short range attraction for a pair of quarks with
their total spin being 0. We show that the existence of the strong quark-quark
correlations enhances the non-leptonic transition amplitudes which is
consistent with the data, while the baryon masses and radii are kept to the
experiment.


title: Field theory of nucleon to higher-spin baryon transitions

abstract:
  We discuss the nucleon to higher-spin $N$- and $\Delta$-resonance transitions
by pions and photons. The higher-spin baryons are described by Rarita-Schwinger
fields and, as we argue, this imposes a stringent consistency requirement on
the form of the couplings. Popular $\pi N\Delta$ and $\gamma N\Delta$ couplings
are inconsistent from this point of view. We construct examples of consistent
interactions with the same nonrelativistic limit as the conventional ones.


title:
Structure effects on the Coulomb dissociation of 8B at relativistic
  energies

abstract:
  We investigate the Coulomb dissociation of 8B on 208Pb target at the beam
energy of 250 MeV/nucleon, employing the cross sections for the radiative
capture reaction 7Be(p,gamma)8B calculated within the Shell Model Embedded in
the Continuum (SMEC) approach. In contrast to the situation at lower beam
energies, the Coulomb breakup cross sections are found to be sensitive to the
M1 transitions. Comparisons of SMEC and single-particle potential model
predictions show that the Coulomb breakup cross sections at these high energies
are sensitive to the structure model of 8B. Analysis of the preliminary data
taken recently at GSI reveal that E2 multipolarity contributes up to 25 % to
the cross sections even for the relative energies of p - 7Be below 0.25 MeV.


title: Mesonic correlations and quark deconfinement

abstract:
  A simple confining separable interaction Ansatz for the rainbow-ladder
truncated QCD Dyson-Schwinger equations is used to implement chiral restoration
and quark deconfinement in a study of $\bar q q$ meson states at finite
temperature. The model is fixed at T=0 by reproducing selected pi and rho
properties. Deconfinement and chiral restoration are found to both occur at
T_c=146 MeV. In the pion sector, we investigate M_pi(T) and f_pi(T) along with
the exact QCD mass relation and the GMOR relation. For the vector mode, we
investigate the 3-space transverse and longitudinal masses M_rho^T(T) and
M_\rho^L(T), along with the widthfor the decay rho^0 --> e^+e^-. The equation
of state (EOS) for the model is investigated in the T-mu plane, a tri-critical
point is identified and the relationship to a bag model is discussed. The
deconfinement transition in rapidly rotating neutron stars is considered and a
new signal from the pulsar timing in binary systems with mass accretion is
suggested. The model is used to discuss the possibility of a superconducting
quark matter phase.


title: Proton-neutron interactions in N \approx Z nuclei

abstract:
  Proton-neutron (p-n) interactions and its various aspects in $N\approx Z$
nuclei of $g_{9/2}$- and $f_{7/2}$ subshell are studied using a schematic model
interaction with four force parameters proposed recently. It is shown that the
model interaction well reproduces observed physical quantities: the double
differences of binding energies, symmetry energy, Wigner energy, odd-even mass
difference and separation energy, which testifies the reliability of the model
interaction and its p-n interactions.
  First of all, the double differences of binding energies are used for probing
the p-n interactions. The analysis reveals different contributions of the
isoscalar and isovector p-n pairing interactions to two types of double
difference of binding energies, and also indicates the importance of a unique
form of isoscalar p-n pairing force with all $J$ components. Next, it is shown
that this p-n force is closely related to the symmetry energy and the Wigner
energy. Other calculations demonstrate significant roles of p-n interactions in
the odd-even mass difference and in the separation energy at $N=Z$.


title: Relativistic heavy ion collisions --- Where are we now? Where do we go?

abstract:
  Various aspects of the current status of ultrarelativistic heavy ion
collisions are reviewed. Perspectives of heavy ion physics in the future are
given as well.


title: Anisotropic flow from AGS to LHC energies

abstract:
  Within hydrodynamics we study the effects of the initial spatial anisotropy
in non-central heavy-ion collisions on the momentum distributions of the
emitted hadrons. We show that the elliptic flow measured at midrapidity in 158
A GeV/c Pb+Pb collisions can be quantitatively reproduced by hydrodynamic
expansion, indicating early thermalization in the collision. We predict the
excitation functions of the 2nd and 4th harmonic flow coefficients from AGS to
LHC energies and discuss their sensitivity to the quark-hadron phase
transition.


title: Comment on "Tensor force in doubly odd deformed nuclei"

abstract:
  An article by Covello, Gargano and Itaco [Phys.Rev. C 56, 3092 (1997)] tries
to find evidence for the important role of the residual tensor force between
the valence proton and neutron in doubly odd deformed nuclei. It is shown that
observable effects discussed by these authors do not fully justify their rather
strong conclusions.


title:
Effective Field Theory Approach To \vec{n} + \vec{p} -> d + \gamma At
  Threshold

abstract:
  Previously, in an effective field theory formulated by us, we have carried
out parameter-free calculations of a large number of low-energy two-nucleon
properties. An experiment at the Institut Laue-Langevin is currently measuring
spin-dependent effects in the polarized np capture process \vec{n}+\vec{p} -> d
+\gamma at threshold. Noting that spin-dependent observables for this reaction
are sensitive to terms of chiral orders higher than hitherto studied, we extend
our effective theory approach to this process and make parameter-free
predictions on the spin-dependent observables.


title: Historical Survey of the Quasi-Nuclear Baryonium

abstract:
  We review ideas and speculations concerning possible bound states or
resonances of the nucleon--antinucleon system.


title:
Semi-Microscopical Description of the Scission Configuration in the Cold
  Fission of $^{252}$Cf

abstract:
  The cold(neutronless) fission of $^{252}$Cf is studied in the frame of a
molecular model in which the scission configuration is described by two aligned
fragments interacting by means of Coulomb (+ nuclear) forces. The study is
carried out for different distances between the fragments tips and excitation
energies. For a given deformation, the fragment's total energy is computed via
the constrained Hartree-Fock + BCS formalism. The total excitation energy
present in the fragments is supposed to contribute only to the fragments
deformation and the asymptotic value of the kinetic energy is equated to the
inter-fragment potential at scission. These two constraints yield not more than
one or two fission channels for a fixed tip distance and excitation energy.
Discarding those fission channels corresponding to a disequilibrated sharing of
the excitation energy between the two fragments, we were able to establish the
most likely scission configurations for a specified excitation energy.


title: On the origin of the short range NN repulsion

abstract:
  We calculate S-wave singlet and triplet NN phase shifts stemming from the
short-range flavor-spin hyperfine interaction between constituent quarks using
the resonating group method approach. A strong short-range repulsion is found
in both waves. A fair comparison is performed between the traditional picture,
relying on the colour-magnetic interaction, and the present one, relying on the
Goldstone boson exchange dynamics. It is shown that the latter one induces
essentially stronger repulsion, which is a very welcome feature. We also study
a sensitivity of phase shifts and wave function to extention from the
one-channel to three-channel resonating group method approximation.


title:
Has charge symmetry breaking been observed in the d d -> alpha pi0
  reaction?

abstract:
  Estimates are made of the d d -> alpha gamma gamma production cross sections
in a model where each neutron-proton pair in the beam and target initiates an n
p -> d gamma reaction. This approach, which successfully reproduces observables
in two-pion production at intermediate energies, suggests that direct
two-photon production could provide a very significant background to the
measurement of the charge-symmetry-breaking (CSB) reaction d d -> alpha pi0. A
non-vanishing CSB cross section has been reported which might be confused with
such two-photon production under the given experimental conditions.


title:
Nucleon-Nucleon Effective Field Theory at NNLO: Radiation Pions and 1S0
  Phase Shift

abstract:
  Low energy phenomena involving two nucleons can be successfully described
using effective field theory. Because of the relatively large expansion
parameter, it is only at next-to-next-to-leading order (NNLO) where one can
expect to see agreement with experiment at the few percent level. The first
part of this talk will focus on radiation pion effects, which first appear at
NNLO. The power counting for radiation pions is simple for center of mass
momentum p~\sqrt{M m_pi}=Q_r, the threshold for pion production. We explain how
graphs calculated with the Q_r power counting scale for p~m_\pi. The Q_r^3
radiation pion contributions to nucleon-nucleon scattering are suppressed by
inverse powers of the S-wave scattering lengths. However, we point out that
order Q_r^4 radiation contributions might give a NNLO contribution for p~m_pi.
In the second part of the talk, results for the potential pion and contact
interaction part of the NNLO 1S0 phase shift are presented. We emphasize the
importance of eliminating spurious poles in the expression for the amplitude at
each order in the perturbative expansion. Doing this leaves a total of three
free parameters at NNLO. We obtain a good fit to the 1S0 phase shift.


title: Chiral Symmetry and Low Energy Pion-Nucleon Scattering

abstract:
  In these lectures, I examine the effect of the meson factory $\pi$N data on
the current algebra/PCAC program which describes chiral symmetry breaking in
this system. After historical remarks on the current algebra/PCAC versus chiral
Lagrangians approaches to chiral symmetry, and description of the need for
$\pi$N amplitudes with virtual (off-mass-shell) pions in nuclear force models
and other nuclear physics problems, I begin with kinematics and isospin aspects
of the invariant amplitudes. A detailed introduction to the hadronic vector and
axial-vector currents and the hypothesis of partially conserved axial-vector
currents (PCAC) follows. I review and test against contemporary data the PCAC
predictions of the Goldberger-Treiman relation, and the Adler consistency
condition for a $\pi$N amplitude. Then comes a detailed description of the
current algebra Ward-Takahashi identities in the chiral limit and a brief
account of the on-shell current algebra Ward-Takahashi identities. The latter
identities form the basis of so-called current algebra models of $\pi$N
scattering. I then test these models against the contemporary empirical $\pi$N
amplitudes extrapolated into the subthreshold region via dispersion relations.
The scale and the t dependence of the "sigma term" is determined by the recent
data.


title: Light-Front Nuclear Physics: Mean Field Theory for Finite Nuclei

abstract:
  A light-front treatment for finite nuclei is developed from a relativistic
effective Lagrangian (QHD1) involving nucleons, scalar mesons and vector
mesons. We show that the necessary variational principle is a constrained one
which fixes the expectation value of the total momentum operator $P^+$ to be
the same as that for $P^-$. This is the same as minimizing the sum of the total
momentum operators: $P^-+P^+$. We obtain a new light-front version of the
equation that defines the single nucleon modes. The solutions of this equation
are approximately a non-trivial phase factor times certain solutions of the
usual equal-time Dirac equation. The ground state wave function is treated as a
meson-nucleon Fock state, and the meson fields are treated as expectation
values of field operators in that ground state. The resulting equations for
these expectation values are shown to be closely related to the usual meson
field equations. A new numerical technique to solve the self-consistent field
equations is introduced and applied to $^{16}$O and $^{40}$Ca. The computed
binding energies are essentially the same as for the usual equal-time theory.
The nucleon plus momentum distribution (probability for a nucleon to have a
given value of $p^+$) is obtained, and peaks for values of $p^+$ about seventy
percent of the nucleon mass. The mesonic component of the ground state wave
function is used to determine the scalar and vector meson momentum distribution
functions, with a result that the vector mesons carry about thirty percent of
the nuclear plus-momentum. The vector meson momentum distribution becomes more
concentrated at $p^+=0$ as $A$ increases.


title: Nucleonic resonance effects in the $\phi$ meson photoproduction

abstract:
  The process $\gamma p \to \phi p$ close to threshold is investigated focusing
on the role played by the {\it s}- and {\it u}-channel nucleonic resonances.
For this purpose, a recent quark model approach, based on the $SU(6)\otimes
O(3)$ symmetry with an effective Lagrangian, is extended to the $\phi$ meson
photoproduction. Another non-diffractive process, the {\it t}-channel $\pi^0$
exchange, is also included. The diffractive contribution is produced by the
{\it t}-channel Pomeron exchange. Contributions from non-diffractive {\it s}-
and {\it u}-channel process are found small in the case of cross sections and
polarization observables at forward angles. However, backward angle
polarization asymmetries show high sensitivity to this non-diffractive process.
Different prescriptions to keep gauge invariance for the Pomeron exchange
amplitudes are investigated. Possible deviations from the exact $SU(6)\otimes
O(3)$ symmetry, due to the configuration mixing, are also discussed.


title: Neutron charge radius and the Dirac equation

abstract:
  We consider the Dirac equation for a finite-size neutron in an external
electric field. We explicitly incorporate Dirac-Pauli form factors into the
Dirac equation. After a non-relativistic reduction, the Darwin-Foldy term is
cancelled by a contribution from the Dirac form factor, so that the only
coefficient of the external field charge density is $e/6 r^2_{En}$, i. e. the
root mean square radius associated with the electric Sachs form factor . Our
result is similar to a recent result of Isgur, and reconciles two apparently
conflicting viewpoints about the use of the Dirac equation for the description
of nucleons.


title: Studies of the electric dipole transitions of deformed rare-earth nuclei

abstract:
  Spectrum and electric dipole transition rates and relative intensities in
$^{152-154}$Sm, $^{156-160}$Gd, $^{160-162}$Dy are studied in the framework of
the interacting boson model with s,p,d,f bosons. It is found that E1 transition
data among the low-lying levels are in good agreement with the SU(3) dynamical
symmetry of the spdf interacting boson model proposed by Engel and Iachello to
describe collective rotation with octupole vibration. These results show that
these nuclei have SU(3) dynamic symmetry to a good approximation. Also in this
work many algebraic expressions for electric dipole transitions in the SU(3)
limit of the spdf-IBM have been obtained. These formulae together with the
formulae given previously exhaust nearly all the E1 transitions for low-lying
negative parity states. They are useful in analyzing experimental data.


title: The properties of \bar{K} in the nuclear medium

abstract:
  The self-energy of the K^- meson in nuclear matter is calculated in a
self-consistent microscopic approach, using a \bar{K}N interaction obtained
from the lowest-order meson-baryon chiral Lagrangian. The effective \bar{K}N
interaction in the medium is derived by solving the coupled-channel
Bethe-Salpeter equation including Pauli blocking on the nucleons, mean-field
binding potentials for the baryons and the self-energy of the \pi and \bar{K}
mesons. The incorporation of the self-consistent {\bar K} self-energy in the
description, in addition to the Pauli blocking effects, yields a weaker
attractive in-medium {\bar K}N interaction and a \Lambda(1405) which dissolves
faster with increasing matter density, as a result of the {\bar K} spectral
function being spread out over a wide range of energies. These effects are
further magnified when the intermediate pions are dressed.


title:
Complete set of electromagnetic corrections to the nucleon mass in the
  Nambu-Jona-Lasinio model

abstract:
  We show how to derive the complete set of electromagnetic corrections to the
Nambu-Jona-Lasinio (NJL) model of the nucleon. Our results enable an accurate
estimate of the electromagnetic contribution to the neutron-proton mass
difference within this model. At the same time, our procedure demonstrates the
way to calculate the complete set of meson corrections to the NJL model that
maintains chiral symmetry.


title:
Chiral Unitary Approach To The N*N*pi, N*N*eta Couplings For The
  N*(1535) Resonance

abstract:
  Using a chiral unitary model in which the negative parity nucleon resonance
$N^\ast \equiv N^\ast(1535)$ is generated dynamically by means of the Bethe
Salpeter equation with coupled meson baryon channels in the $S = 0$ sector, we
have obtained the $\pi^0 N^\ast N^\ast$ and $\eta N^\ast N^\ast$ couplings. The
$\pi^0 N^\ast N^\ast$ coupling has smaller strength and the same sign as the
$\pi^0 N N$ coupling. This rules out the mirror assignment of chiral symmetry
where the ground state nucleon $N$ and the negative parity resonance $N^\ast$
are envisaged as chiral partners in the baryon sector.


title:
Medium Effects in Coherent Pion Photo- and Electroproduction on 4He and
  12C

abstract:
  Coherent pi0 photo- and electroproduction on 4He and 12C nuclei is
investigated in the framework of a distorted wave impulse approximation in
momentum space. The elementary process is described by the recently developed
unitary isobar model. Medium effects are considered by introducing a
phenomenological Delta self-energy. The recent experimental data for 4He and
12C can be well described over a wide range of energies and emission angles by
the assumption that the Delta-nuclear interaction saturates.


title: Resonances and Off-Shell Characteristics of Effective Interactions

abstract:
  The importance of including experimental resonances in constructing effective
inter-cluster interactions has been investigated. For this, we first address
the question of how to obtain the analytical properties of the Jost function in
regions of physical interest on the complex k-plane when the potential is given
in a tabular form. We then employ the Marchenko inverse scattering method to
construct, numerically, phase equivalent local potentials supporting the same
bound state(s) but having different resonance spectra which affect the
off-shell characteristics of the corresponding scattering amplitudes. This
implies that the inclusion of the experimental resonances in constructing a
potential would change its shape, strength, and range which in turn would
modify the bound and scattering wave functions in the interior region. This is
expected to have important consequences in calculations of transition
amplitudes in nuclear reaction theories, which strongly depend on the behaviour
of the wave functions at short distances. The influence of Supersymmetric
Transformations on the position and movement of resonances has also been
investigated.


title: About Atomic Structure of Nucleon

abstract:
  The comparison of magnetic moments of neutron and proton reveals three
possible states of a nucleon. The arguments are presented why these states can
be the stationary states.


title: Imaging proton sources and space-momentum correlations

abstract:
  The reliable extraction of information from two-proton correlation functions
is a long-standing problem in two-particle interferometry. Recently introduced
imaging techniques give one the ability to reconstruct source functions from
the correlation data in a model independent way. We explore the applicability
of two-proton imaging to realistic sources with transverse space-momentum
correlations. We find that the proton images are very sensitive to these
correlations. We show that one can reliably reconstruct the source functions
from the two-proton correlation functions, regardless of the degree of the
space-momentum correlations.


title:
Symmetry Breaking and Bifurcations in the Periodic Orbit Theory: I:
  Elliptic Billiard

abstract:
  We derive an analytical trace formula for the level density of the
two-dimensional elliptic billiard using an improved stationary phase method.
The result is a continuous function of the deformation parameter (eccentricity)
through all bifurcation points of the short diameter orbit and its repetitions,
and possesses the correct limit of the circular billiard at zero eccentricity.
Away from the circular limit and the bifurcations, it reduces to the usual
(extended) Gutzwiller trace formula which for the leading-order families of
periodic orbits is identical to the result of Berry and Tabor. We show that the
circular disk limit of the diameter-orbit contribution is also reached through
contributions from closed (periodic and non-periodic) orbits of hyperbolic type
with an even number of reflections from the boundary. We obtain the Maslov
indices depending on deformation and energy in terms of the phases of the
complex error and Airy functions. We find enhancement of the amplitudes near
the common bifurcation points of both short-diameter and hyperbolic orbits. The
calculated semiclassical level densities and shell energies are in good
agreement with the quantum mechanical ones.


title:
Nonequilibrium Weak Processes in Kaon Condensation I --- Reaction rate
  for the thermal kaon process ---

abstract:
  We investigate the thermal kaon process,in which kaons are thermally produced
via nucleon-nucleon collisions.This process is relevant to nonequilibrium
dynamics of kaon condensation inside neutron stars.The reaction rates for these
processes are calculated, and their temperature and density dependences are
compared with those of other reaction rates.It is shown that the thermal kaon
process is dominant over other relevant weak reactions throughout the
nonequilibrium process, such as the kaon-induced Urca and the modified Urca
reactions, and may control the entire evolution of the kaon condensate. The
characteristic role of the soft and hard kaons during the evolution is
explained, and implications for astrophysical phenomena are briefly discussed.


title:
On convergence of the HFF expoansion for meson production in NN
  collisions

abstract:
  We consider the application of heavy fermion formalism based ChPT to meson
production in nucleon-nucleon collisions. It is shown that to each lower chiral
order irreducible diagram there corresponds an infinite sequence of loop
diagrams which are of the same momentum power order. This destroys the
one-to-one correspondence between the loop and small momentum expansion and
thus rules out the application of any finite order HFF ChPT yo the NN-> NNpion
reactions.


title:
Kaon photoproduction on the nucleon: Contributions of kaon-hyperon final
  states to the magnetic moment of the nucleon

abstract:
  By using the Gerasimov-Drell-Hearn (GDH) sum rule and an isobaric model of
kaon photoproduction, we calculate contributions of kaon-hyperon final states
to the magnetic moment of the proton and the neutron. We find that the
contributions are small. The approximation of sigma_{TT'} by sigma_{T} clearly
overestimates the value of the GDH integral. We find a smaller upper bound for
the contributions of kaon-hyperon final states to the proton's anomalous
magnetic moment in kaon photoproduction, and a positive contribution for the
square of the neutron's magnetic moment.


title: Ground state energy fluctuations in nuclear matter II

abstract:
  Improvements are performed on a recently proposed statistical theory of the
mean field of a many-fermion system. The dependence of the predictions of the
theory upon its two basic ingredients, namely the Hartree-Fock energy and the
average energy of the two particle-two hole excitations, is explored.


title: Effective chiral theory of nucleon-nucleon scattering

abstract:
  We present a new chiral expansion scheme for the nucleon-nucleon scattering
amplitude which preserves unitarity exactly. Our effective field theory builds
on the power counting rules for 2-nucleon reducible diagrams proposed in
\cite{lutz}. We evaluate the leading order terms of the isospin one scattering
amplitude and elaborate in detail on the $^1S_0$ phase shift. Our chiral
description of the $^1S_0$-phase shift does compete in quality with modern
phenomenological nucleon-nucleon potentials. We describe elastic and inelastic
scattering quantitatively up to laboratory energies of $E_{\rm lab} \simeq 600$
MeV.


title: Quark Matter '99 --- Theoretical Summary: What Next?

abstract:
  I review the three broad areas where major progress has been reported: The
phase structure of strongly interacting matter, the properties of matter at the
instant when it freezes out into individual hadrons in the final stage of the
expansion of the hot fireball, and the status of the main signatures of the
formation of a quark-gluon plasma. In the final section I present some thoughts
about what should be done next, both in the experiemntal and the theoretical
arena.


title:
Shell structure of superheavy nuclei in self-consistent mean-field
  models

abstract:
  We study the extrapolation of nuclear shell structure to the region of
superheavy nuclei in self-consistent mean-field models -- the
Skyrme-Hartree-Fock approach and the relativistic mean-field model -- using a
large number of parameterizations. Results obtained with the Folded-Yukawa
potential are shown for comparison. We focus on differences in the isospin
dependence of the spin-orbit interaction and the effective mass between the
models and their influence on single-particle spectra. While all relativistic
models give a reasonable description of spin-orbit splittings, all
non-relativistic models show a wrong trend with mass number. The spin-orbit
splitting of heavy nuclei might be overestimated by 40%-80%. Spherical
doubly-magic superheavy nuclei are found at (Z=114,N=184), (Z=120,N=172) or
(Z=126,N=184) depending on the parameterization. The Z=114 proton shell
closure, which is related to a large spin-orbit splitting of proton 2f states,
is predicted only by forces which by far overestimate the proton spin-orbit
splitting in Pb208. The Z=120 and N=172 shell closures predicted by the
relativistic models and some Skyrme interactions are found to be related to a
central depression of the nuclear density distribution. This effect cannot
appear in macroscopic-microscopic models which have a limited freedom for the
density distribution only. In summary, our findings give a strong argument for
(Z=120,N=172) to be the next spherical doubly-magic superheavy nucleus.


title:
Simple Applications of Effective Field Theory and Similarity
  Renormalization Group Methods

abstract:
  We use two renormalization techniques, Effective Field Theory and the
Similarity Renormalization Group, to solve simple Schr{\"o}dinger equations
with delta-function potentials in one and two dimensions. The familiar
one-dimensional delta-function does not require renormalization, but it
provides the simplest example of a local interaction that can be replaced by a
sequence of effective cutoff interactions that produce controllable power-law
errors. The two-dimensional delta-function leads to logarithmic divergences,
dimensional transmutation and asymptotic freedom, providing an example of some
of the most important renormalization problems in gauge field theories. We
concentrate on the power-law analysis of errors in low-energy observables. The
power-law suppression of the effects of irrelevant operators is critical to the
success of field theory, and understanding them turns renormalization group
techniques into powerful predictive tools for complicated problems where exact
solutions are not available.


title: Effective Theory of the Triton

abstract:
  We apply the effective field theory approach to the three-nucleon system. In
particular, we consider S=1/2 neutron-deuteron scattering and the triton. We
show that in this channel a unique nonperturbative renormalization takes place
which requires the introduction of a single three-body force at leading order.
With one fitted parameter we find a good description of low-energy data.
Invariance under the renormalization group explains some universal features of
the three-nucleon system ---such as the Thomas and Efimov effects and the
Phillips line--- and the origin of SU(4) symmetry in nuclei.


title:
The relationship between particle freeze-out distributions and HBT
  radius parameters

abstract:
  The relationship between pion and kaon space-time freeze-out distributions
and the HBT radius parameters in high-energy nucleus-nucleus collisions is
investigated. We show that the HBT radius parameters in general do not reflect
the R.M.S. deviations of the single particle production points. Instead, the
HBT radius parameters are most closely related to the curvature of the
two-particle space-time relative position distribution at the origin. We
support our arguments by studies with a dynamical model (RQMD 2.4).


title: Two-Particle Correlations from the q-Boson Viewpoint

abstract:
  We propose and develop to some extent a novel approach, which allows us to
effectively describe, for relativistic heavy-ion collisions, the empirically
observed deviation from unity of the intercept \lambda (i.e. the measured value
corresponding to zero relative momentum {\bf p} of two registered identical
pions or kaons) of the two-particle correlation function C(p,K). The approach
is based on the use of two versions of the so-called q-deformed oscillators and
the corresponding picture of ideal gases of q-bosons. By these techniques the
intercept \lambda is put into direct correspondence with the deformation
parameter q. For fixed deformation strength, the model predicts dependence of
the intercept \lambda on the pion pair mean momentum {\bf K}.


title:
Axial Vector Current and Induced Pseudoscalar Coupling Constant on
  $\mu^- p \to n \nu_{\mu} \gamma$ reaction

abstract:
  The recent TRIUMF experiment for $\mu^- p \to n \nu_{\mu} \gamma$ gave a
surprising result that the induced pseudoscalar coupling constant $g_P$ was
larger than the value obtained from $\mu^- p \to n \nu_{\mu}$ experiment as
much as 44 %. Reexamining axial vector current on the gauge theory, we found an
additional term to the matrix element of Beder and Fearing which was used to
extract the $g_P$ value from the measured photon energy spectrum. This
additional term, which is self gauge invariant, plays a key role in restoring
the reliability of $g_P (- 0.88 m_{\mu}^2) = 6.77 g_A (0)$. Comparison with
conventional approaches is also presented.


title: Weak Decay of $\Lambda$ in Nuclei : Quarks vs Mesons

abstract:
  Decays of $\Lambda$ in nuclei, nonmesonic mode, are studied by using the
$\Lambda N \to NN$ weak transition potential derived from the meson exchange
mechanism and the direct quark mechanism. The decay rates are calculated both
for the $\Lambda$ in symmetric nuclear matter and light hypernuclei. We
consider the exchange of six mesons ($\pi, K, \eta, \rho, \omega, K^\ast$). The
form factor in the meson exchange mechanism and short range correlation are
carefully studied.


title:
Numerical analysis of two-pion correlation based on a hydrodynamical
  model

abstract:
  We will numerically investgate two-particle correlation function of CERN--SPS
158 A GeV Pb+Pb central collisions in detail based on a (3+1)-dimensional
relativistic hydrodynamical model with first order phase transition. We use the
Yano-Koonin-Podgoretski\u{\i} parametrization as well as the usual Cartesian
parametrization and analyze the pair momentum dependence of HBT radii extracted
from the parametrizations. We find that the interpretation of the temporal
radius parameters as the time duration in YKP parametrization is not available
for the hydrodynamical model where the source became opaque naturally because
of expansion and surface dominant freeze-out. Finally, effect of the phase
transition on the source opacity is also discussed.


title: Describing a1 and b1 decays

abstract:
  Two-body pion-radiating and weak decays of light axial-vector mesons and the
rho are studied as a phenomenological application of the QCD Dyson-Schwinger
equations. Models based on the rainbow-ladder truncation are capable of
providing a good description and, in particular, yield the correct sign and
magnitude of the a1 -> rho pi and b1 -> omega pi D/S ratios, with no additional
mechanism necessary.


title:
SU(3) quasi-dynamical symmetry as an organizational mechanism for
  generating nuclear rotational motions

abstract:
  The phenomenological symplectic model with a Davidson potential is used to
construct rotational states for a rare-earth nucleus with microscopic wave
functions. The energy levels and E2 transitions obatined are in remarkably
close agreement (to within a few percent) with those of the rotor model with
vibrational shape fluctuations that are adiabatically decoupled from the
rotational degrees of freedom. An analysis of the states in terms of their
SU(3) content shows that SU(3) is a very poor dynamical symmetry but an
excellent quasi-dynamical symmetry for the model. It is argued that such
quasi-dynamical symmetry can be expected for any Hamiltonian that reproduces
the observed low-energy properties of a well-deformed nucleus, whenever the
latter are well-described by the nuclear rotor model.


title: Kaon differential flow in relativistic heavy-ion collisions

abstract:
  Using a relativistic transport model, we study the azimuthal momentum
asymmetry of kaons with fixed transverse momentum, i.e., the differential flow,
in heavy-ion collisions at beam momentum of 6 GeV/c per nucleon, available from
the Alternating Gradient Synchrotron (AGS) at the Brookhaven National
Laboratory (BNL). We find that in the absence of kaon potential the kaon
differential flow is positive and increases with transverse momentum as that of
nucleons. The repulsive kaon potential as predicted by theoretical models,
however, reduces the kaon differetnial flow, changing it to negative for kaons
with low momenta. Cancellation between the negative differential flow at low
mementa and the positive one at high momenta is then responsible for the
experimentally observed nearly vanishing in-plane transverse flow of kaons in
heavy ion experiments.


title: Chiral Symmetry and Weak Decay of Hypernuclei

abstract:
  The weak decays of hyperons and hypernuclei are studied from the chiral
symmetry viewpoint. The soft pion relations are useful in understanding the
isospin properties of the weak hyperon decays. Recent development on the
short-range part of the $\Lam N\to NN$ weak transitions shows fairly good
account of the weak decays of hypernuclei, though it fails to explain the $n/p$
ratio. The $\pip$ decays of light hypernuclei are studied in the soft pion
approach. They are related to the $\DI=3/2$ amplitudes of the nonmesonic decay.


title:
Weak Decay of $\Lambda$ in Nuclei: Direct Quark Mechanism vs Meson
  Exchange

abstract:
  Nonmesonic decays of $\Lambda$ in nuclear medium and light hypernuclei are
studied by using the $\Lambda N \to NN$ weak transition potential derived from
the meson exchange mechanism and the direct quark mechanism. The long range
part of the transition potential is described by exchanges of the pseudoscalar
mesons ($\pi$, $K$, $\eta$), while the vector mesons ($\rho$, $\omega$,
$K^\ast$) may be considered as the medium- and short-range part in the meson
exchange picture. We propose the direct quark transition potential as the short
range part, which is derived from the matrix elements of the $\Delta S=1$
effective weak Hamiltonian in the two baryon states. The results indicate that
the direct quark contribution is significantly large and its behavior is
qualitatively different from the vector meson exchanges. We also find that the
decay rate is sensitive to the choice of form factor and that a soft cutoff
must be used for the pion-baryon verteces so that the strong tensor transition
is suppressed. We find that the $\pi + K + DQ$ results are compatible with
experiment although the $n/p$ ratio is still too large. The $\pi^+$ decays of
light hypernuclei are related to the $\DI=3/2$ amplitudes of the nonmesonic
decay. The role of chiral symmetry for the pionic decays are discussed.


title: Magnetic Monopole Decay and Its Consequences

abstract:
  We return to further examination of the need for the existence of magnetic
monopoles based on the decades old derivation [Sherman Frankel, Amer. Jour. of
Physics, 44, 7, 683-6 1976], of both the monopole-charge force, vec(F) =
eg(vec(r) * vec(v)/c)/r^3, as well as the Dirac angular momentum, vec(l_f) = eg
hat(r), from P and T conservation alone, without any recourse whatsoever to
Maxwell's Equations. The eg product also appeared in the charge conserving
equation, deg/dt = 0 = edg/dt + gde/dt, and this paper examines the second
possible solution, dg/dt = - de/dt, namely monopole decay, accounting for the
non-observance of stable monopoles. It treats astrophysics and neutrino physics
consequences and suggestions for experimental searches.


title: Non-perturbative model for the half-off-shell \gamma N N vertex

abstract:
  Form factors in the nucleon-photon vertex with one off-shell nucleon are
calculated by dressing the vertex with pion loops up to infinite order. Cutting
rules and dispersion relations are implemented in the model. Using the
prescription of minimal substitution we construct a \gamma \pi N N vertex and
show that it has to be included in the model in order that the Ward-Takahashi
identity for the \gamma N N vertex be fulfilled. The vertex is to be applied in
a coupled-channel K-matrix formalism for Compton scattering, pion
photoproduction and pion scattering. The form factors show a pronounced cusp
structure at the pion threshold. As an illustration of a consistent application
of the model, we calculate the cross section of Compton scattering. To provide
gauge invariance in Compton scattering, a four-point \gamma \gamma N N contact
term is constructed using minimal substitution.


title: Effective field theory for nuclear matter

abstract:
  We apply the relativistic chiral Lagrangian to the nuclear equation of state.
An effective chiral power expansion scheme, which is constructed to work around
nuclear saturation density, is presented. The leading and subleading terms are
evaluated and are shown to provide an equation of state with excellent
saturation properties. Our saturation mechanism is found to probe details of
the nuclear pion dynamics.


title:
On the dominance of J(P)=0(+) ground states in even-even nuclei from
  random two-body interactions

abstract:
  Recent calculations using random two-body interactions showed a preponderance
of J(P)=0(+) ground states, despite the fact that there is no strong pairing
character in the force. We carry out an analysis of a system of identical
particles occupying orbits with j=1/2, 3/2 and 5/2 and discuss some general
features of the spectra derived from random two-body interactions. We show that
for random two-body interactions that are not time-reversal invariant the
dominance of 0(+) states in this case is more pronounced, indicating that
time-reversal invariance cannot be the origin of the 0(+) dominance.


title: Shock-like Freeze-out in Relativistic Hydrodynamics

abstract:
  We have formulated a self-consistent model of freeze-out on an arbitrary
hypersurface. It conserves energy and momentum across the discontinuity between
ideal fluid and the gas of free particles. Energy and momentum of those free
particles have non-equilibrium values that could be a signal for the formation
of hot and dense matter in heavy ion collisions.


title:
Charge-Independence Breaking in the Two-Pion-Exchange Nucleon-Nucleon
  Force

abstract:
  Charge-independence breaking due to the pion-mass difference in the (chiral)
two-pion-exchange nucleon-nucleon force is investigated. A general argument
based on symmetries is presented that relates the charge-symmetric part of that
force to the proton-proton case. The static potential linear in that mass
difference is worked out as an explicit example by means of Feynman diagrams,
and this confirms the general argument.


title:
Measuring longitudinal amplitudes for electroproduction of pseudoscalar
  mesons using recoil polarization in parallel kinematics

abstract:
  We propose a new method for measuring longitudinal amplitudes for
electroproduction of pseudoscalar mesons that exploits a symmetry relation for
polarization observables in parallel kinematics. This polarization technique
does not require variation of electron scattering kinematics and avoids the
major sources of systematic errors in Rosenbluth separation.


title: Parity violation through color superconductivity

abstract:
  We give a pedagogical discussion of how color superconductivity can produce
parity violation in cold quark matter at very high densities.


title: Collective flow and QCD phase transition

abstract:
  In the first part I discuss the sensitivity of collective matter expansion in
ultrarelativistic heavy-ion collisions to the transition between quark and
hadronic matter (physics of the softest point of the Equation of State). A kink
in the centrality dependence of elliptic flow has been suggested as a signature
for the phase transition in hot QCD matter. Indeed, preliminary data of NA49
presented at this conference show first indications for the predicted kink. In
the second part I have a look at the present theories of heavy-ion reactions.
These remarks may also be seen as a critical comment to B. Mueller's summary
talk (nucl-th/9906029) presented at this conference.


title: Simple model for decay of superdeformed nuclei

abstract:
  Recent theoretical investigations of the decay mechanism out of a
superdeformed nuclear band have yielded qualitatively different results,
depending on the relative values of the relevant decay widths. We present a
simple two-level model for the dynamics of the tunneling between the
superdeformed and normal-deformed bands, which treats decay and tunneling
processes on an equal footing. The previous theoretical results are shown to
correspond to coherent and incoherent limits of the full tunneling dynamics.
Our model accounts for experimental data in both the A~150 mass region, where
the tunneling dynamics is coherent, and in the A~190 mass region, where the
tunneling dynamics is incoherent.


title:
Study of the He3(He4,gamma)Be7 and H3(He4,gamma)Li7 reactions in an
  extended two-cluster model

abstract:
  The He3(He4,gamma)Be7 and H3(He4,gamma)Li7 reactions are studied in an
extended two-cluster model which contains alpha+h/t and Li6+p/n
clusterizations. We show that the inclusion of the Li6+p/n channels can
significantly change the zero-energy reaction cross sections, S(0), and other
properties of the Be7 and Li7 nuclei, like the quadrupole moments Q. However,
the results agree with the known correlation trend between S(0) and Q.
Moreover, we demonstrate that the value of the zero-energy derivatives of the
astrophysical S-factors are more uncertain than currently believed.


title: A classical two-body Hamiltonian model and its mean field approximation

abstract:
  We extend a recent billiard model of the nuclear N-body Hamiltonian to
consider a finite two-body interaction. This permits a treatment of the
Hamiltonian by a mean field theory, and also allows the possibility to model
reactions between nuclei. The density and the mean field potential can be
accurately described by a scaling function which shows the qualitative features
of the liquid drop picture of the nucleus.


title: Transverse Energy Production at RHIC

abstract:
  We study the mechanism of transverse energy (E_T) production in Au+Au
collisions at RHIC. The time evolution starting from the initial energy loss to
the final E_T production is closely examined in transport models. The
relationship between the experimentally measured E_T distribution and the
maximum energy density achieved is discussed.


title: The NN scattering 3S1-3D1 mixing angle at NNLO

abstract:
  The 3S1-3D1 mixing angle for nucleon-nucleon scattering, epsilon_1, is
calculated to next-to-next-to-leading order in an effective field theory with
perturbative pions. Without pions, the low energy theory fits the observed
epsilon_1 well for momenta less than $\sim 50$ MeV. Including pions
perturbatively significantly improves the agreement with data for momenta up to
$\sim 150$ MeV with one less parameter. Furthermore, for these momenta the
accuracy of our calculation is similar to an effective field theory calculation
in which the pion is treated non-perturbatively. This gives phenomenological
support for a perturbative treatment of pions in low energy two-nucleon
processes. We explain why it is necessary to perform spin and isospin traces in
d dimensions when regulating divergences with dimensional regularization in
higher partial wave amplitudes.


title:
A Second Look at Single Photon Production in S+Au Collisions at 200
  A$\cdot$GeV and Implications for Quark Hadron Phase Transition

abstract:
  We reanalyze the production of single photons in S+Au collisions at CERN SPS
to investigate: i) the consequences of using a much richer equation of state
for hadrons than the one used in an earlier study by us; and, ii) to see if the
recent estimates of photon production in quark-matter (at two loop level) by
Aurenche et al. are consistent with the upper limit of the photon production
measured by the WA80 experiment. We find that the measured upper limit is
consistent with a quark hadron phase transition. The measured upper limit is
also consistent with a scenario where no phase transition takes place, but
where the hadronic matter reaches a density of several hadrons per unit volume;
which is rather unphysical.


title:
The short-range baryon-baryon interaction in a chiral constituent quark
  model

abstract:
  The previous analysis of the short-range $NN$ repulsion originating from the
Goldstone boson exchange hyperfine interaction between constituent quarks is
revisited. We study in which respects the repulsion depends on the radial form
of the spin-spin quark-quark force. We show that while the radial form affects
the structure of the 6Q wave function, the short-range repulsion in the $NN$
system persists in any case. We extend our analysis to other $YN$ and $YY$
(flavor octet-octet) systems and demonstrate that the flavor-spin hyperfine
interaction implies a short-range repulsion in these B=2 systems as well.


title: Decay out of a Superdeformed Band

abstract:
  Using a statistical model for the normally deformed states and for their
coupling to a member of the superdeformed band, we calculate the ensemble
average and the fluctuations of the intensity for decay out of the
superdeformed band and of the intraband decay intensity. We show that both
intensities depend on two dimensionless variables: The ratio
$\Gamma^{\downarrow}/\Gamma_S$ and the ratio $\Gamma_N/d$. Here,
$\Gamma^{\downarrow}$ is the spreading width for the mixing of the
superdeformed and the normally deformed states, $d$ is the mean level spacing
of the latter, and $\Gamma_S$ ($\Gamma_N$) is the width for gamma decay of the
superdeformed state (of the normally deformed states, respectively). This
parametric dependence differs from the one predicted by the approach of Vigezzi
et al. where the relevant dimensionless variables are $\Gamma_N/\Gamma_S$ and
$\Gamma^{\downarrow}/d$. We give analytical and numerical results for the decay
intensities as functions of the dimensionless variables, including an estimate
of the error incurred by performing the ensemble average, and we present fit
formulas useful for the analysis of experimental data. We compare our results
with the approach of Vigezzi et al. and establish the conditions under which
this approach constitutes a valid approximation.


title: Covariance of Antiproton Yield and Source Size in Nuclear Collisions

abstract:
  We confront for the first time the widely-held belief that combined
event-by-event information from quark gluon plasma signals can reduce the
ambiguity of the individual signals. We illustrate specifically how the
measured antiproton yield combined with the information from pion-pion HBT
correlations can be used to identify novel event classes.


title: Relativistic description of J/\psi dissociation in hot matter

abstract:
  The mass spectra and binding radii of heavy quark bound states are studied on
the basis of the reduced Bethe-Salpeter equation. The critical values of
screening masses for $c\bar{c}$ and $b\bar{b}$ bound states at a finite
temperature are obtained and compared with the previous results given by
non-relativistic models.


title:
High energy collisions of strongly deformed nuclei: An old idea with a
  new twist

abstract:
  UU collisions can provide about 30% larger densities compared to central PbPb
ones. New aspect is generation of rather deformed initial states. We show that
those can be effectively used to resolve a number of outstanding issues, from
corrections to hard processes, elliptic flow (the QGP push issue), and the
mechanism of $J/\psi$ suppression. UU collisions are studied by a simple
Monte-Carlo model, and it is shown how selecting two control parameters - the
number of participant nuclei and deformation - one can select particular
geometry of the collision.


title: T-odd particle spin rotation in nuclear target

abstract:
  It is shown that particle spin rotation in nuclear target, caused by the
imaginary part of the spin-dependent forward scattering amplitude, is T-odd
rotation.


title:
Omega- and phi-meson production in p n -> d M reactions near threshold
  and OZI-rule violation

abstract:
  We investigate the reactions p n -> d omega and p n -> d phi close to the
corresponding thresholds. The S-wave amplitudes are calculated within the
framework of the two-step model which is described by a triangle graph with pi,
rho and omega mesons in the intermediate state. The cross sections of the
reactions p n -> d omega and p n -> d phi are predicted to be significantly
larger than the cross sections of the corresponding reactions p p -> p p omega
and p p -> p p phi at the same values of the c.m. excess energy Q. The ratio of
the yields of phi to omega is found to be (30 +/- 7) x 10^-3.


title:
Particle Ratios at CERN, BNL and GSI : Unified Description of Freeze-Out
  Parameters

abstract:
  It is shown that the chemical freeze-out parameters obtained at CERN/SPS,
BNL/AGS and GSI/SIS energies all correspond to a unique value of 1 GeV for the
average energy per hadron.


title: Quasifree kaon-photoproduction from nuclei in a relativistic approach

abstract:
  We compute the recoil polarization of the lambda-hyperon and the photon
asymmetry for the quasifree photoproduction of kaons in a relativistic
impulse-approximation approach. Our motivation for studying polarization
observables is threefold. First, polarization observables are more effective
discriminators of subtle dynamics than the unpolarized cross section. Second,
earlier nonrelativistic calculations suggest an almost complete insensitivity
of polarization observables to distortions effects. Finally, this insensitivity
entails an enormous simplification in the theoretical treatment. Indeed, by
introducing the notion of a ``bound-nucleon propagator'' we exploit Feynman's
trace techniques to develop closed-form, analytic expressions for all
photoproduction observables. Moreover, our results indicate that polarization
observables are also insensitive to relativistic effects and to the nuclear
target. Yet, they are sensitive to the model parameters, making them ideal
tools for the study of modifications to the elementary amplitude --- such as in
the production, propagation, and decay of nucleon resonances --- in the nuclear
medium.


title: Directed flow of neutral strange particles at AGS

abstract:
  Directed flow of neutral strange particles in heavy ion collisions at AGS is
studied in the ART transport model. Using a lambda mean-field potential which
is 2/3 of that for a nucleon as predicted by the constituent quark model,
lambdas are found to flow with protons but with a smaller flow parameter as
observed in experiments. For kaons, their repulsive potential, which is
calculated from the impulse approximation using the measured kaon-nucleon
scattering length, leads to a smaller anti-flow than that shown in the
preliminary E895 data. Implications of this discrepancy are discussed.


title: Van der Waals Excluded Volume Model of Multicomponent Hadron Gas

abstract:
  A generalization of the Van der Waals excluded volume procedure for the
multicomponent hadron gas is proposed. The derivation is based on the grand
canonical partition function for the system of particles of several species
interacting by hard core potentials. The obtained formulae for thermodynamical
quantities are consistent with underlying principles of statistical mechanics
as well as with thermodynamical identities. The model can be applied to the
analysis of experimental data for particle number ratios in relativistic
nucleus-nucleus collisions.


title:
Statistical Properties of Charmonium Spectrum and a New Mechanism of
  J/\psi Suppression

abstract:
  The statistical properties of Charmonium energy spectrum determined by the
Bethe-Salpeter equation are investigated. It is found that the regular motion
of the $c\bar{c}$ system can be expected at a small value of color screening
mass but the chaotic motion at a large one. It is shown that the level mixing
due to color screening serves as a new mechanism resulting in the J/$\psi$
suppression. Moreover, this kind of suppression can occur before the color
screening mass reaches its critical value for J/$\psi$ dissociation. It implies
that a strong J/$\psi$ suppression is possible in the absence of dissociation
of J/$\psi$.


title:
Truncation of Large Shell-Model Eigenproblems by Model Space
  Partitioning

abstract:
  A method for solving the shell-model eigenproblem in a severely truncated
space, spanned by properly selected correlated states obtained by partitioning
the full configuration space, is proposed. The method describes in a
practically exact way the low energy spectroscopic properties of nuclei, as
exemplified in schematic models. The applicability of the method to heavy
nuclei as well in contexts different from the nuclear shell model is stressed


title:
The Interference Term between the Spin and Orbital Contributions to M1
  Transitions

abstract:
  We study the cross-correlation between the spin and orbital parts of magnetic
dipole transitions M1 in both isoscalar and isovector channels. In particular,
we closely examine certain cases where $\sum B(M1)$ is very close to $\sum
B(M1)_{\sigma} + \sum B(M1)_l$, implying a cancellation of the summed
interference terms. We gain some insight into this problem by considering
special cases approaching the SU(3) limit, and by examining the behaviour of
single-particle transitions at the beginning and towards the end of the s-d
shell.


title:
Excitation function of strangeness in A+A reactions from SIS to RHIC
  energies

abstract:
  The properties of $K^+$ and $K^-$ mesons are studied in nuclear reactions
from SIS to RHIC energies within the covariant transport approach HSD in
comparison to the experimental data whenever available. Whereas kaon
abundancies and spectra indicate little repulsive or vanishing selfenergies in
the medium, antikaons are found to experience strong attractive potentials in
nucleus-nucleus collisions at SIS energies. However, even when including these
potentials the $K^+$ and $K^-$ spectra at AGS energies are noticeably
underestimated showing an experimental excess of strangeness that points
towards a nonhadronic phase in these reactions. On the other hand the $K^+,
K^-$ production at SPS energies is again well described by the HSD approach
based on quark, diquark, string and hadronic degress of freedom. At RHIC
energies hadronic rescatterings are found to enhance the strangeness yield from
the partonic phase quite substantially.


title: Exploring Nucleon-Nucleon correlations in ($e,e'NN$) reactions

abstract:
  Correlations in the nuclear wave-function beyond the mean-field or
Hartree-Fock approximation are very important to describe basic properties of
nuclear structure. Attempts are made to explore details of these correlations
in exclusive nucleon knock-out by electron scattering experiments. Basic
results of $(e,e'p)$ experiments are reviewed. The role of correlations in
$(e,e'NN)$ experiments is discussed. Special attention is paid to a consistent
description of the competing effects due to final state interaction, meson
exchange current and isobar currents. Results are discussed for systematic
studies of these features in nuclear matter as well as for specific examples
for the finite nucleus $^{16}$O.


title: Fluctuations of particle ratios and the abundance of hadronic resonances

abstract:
  In this letter we will argue that the event-by-event fluctuations of the
ratio of positively over negatively charged pions provides a measurements of
the number of rho and omega mesons right after hadronization. This finding can
be utilized to put the hypothesis of chemical equilibration in relativistic
heavy ion collisions to a test.


title: The physics of the centrality dependence of elliptic flow

abstract:
  The centrality dependence of elliptic flow and how it is related to the
physics of expansion of the system created in high energy nuclear collisions is
discussed. Since in the hydro limit the centrality dependence of elliptic flow
is mostly defined by the elliptic anisotropy of the overlapping region of the
colliding nuclei, and in the low density limit by the product of the elliptic
anisotropy and the multiplicity, we argue that the centrality dependence of
elliptic flow should be a good indicator of the degree of equilibration reached
in the reaction. Then we analyze experimental data obtained at AGS and SPS
energies. The observed difference in the centrality dependence of elliptic flow
could imply a transition from a hadronic to a partonic nature of the system
evolution. Finally we exploit the multiplicity dependence of elliptic flow to
make qualitative predictions for RHIC and LHC.


title: Elliptic flow in heavy ion collisions near the balance energy

abstract:
  The proton elliptic flow in collisions of Ca on Ca at energies from 30 to 100
MeV/nucleon is studied in an isospin-dependent transport model. With increasing
incident energy, the elliptic flow shows a transition from positive to negative
flow. Its magnitude depends on both the nuclear equation of state (EOS) and the
nucleon-nucleon scattering cross section. Different elliptic flows are obtained
for a stiff EOS with free nucleon-nucleon cross sections and a soft EOS with
reduced nucleon-nucleon cross sections, although both lead to vanishing
in-plane transverse flow at the same balance energy. The study of both in-plane
and elliptic flows at intermediate energies thus provides a means to extract
simultaneously the information on the nuclear equation of state and the
nucleon-nucleon scattering cross section in medium.


title: Nucleon-Nucleon Scattering in Effective Field Theory

abstract:
  I outline the effective field theory (EFT) calculation of nucleon-nucleon
scattering which was recently carried out to next-to-next-to-leading order
(NNLO) by Noam Shoresh and myself. In this calculation only potential pion
contributions are included. These are the leading contributions from pions. A
toy model was also considered in which potential pions are the only pion
effects. The effective range expansion (ERE), which is valid for low energies,
is used to derive matching conditions on some of the EFT couplings.
Renormalization group flow analysis is used to fix the rest of the couplings
leaving no free parameters at NNLO.


title: Vacuum Condensates in the Global Color Symmetry Model

abstract:
  Based on the quark propagator in the instanton dilute liquid approximation,
we calculate analytically the quark condensate $<\bar{q}q>$, the mixed quark
gluon condensate $g_{s}<\bar{q}G_{\mu\nu}\sigma^{\mu\nu}q>$ and the four quark
condensate $<\bar{q} \Gamma q\bar{q} \Gamma q>$ at the mean field level in the
framework of global color symmetry model. The numerical calculation shows that
the values of these condensates are compatible with the ranges determined by
other nonperturbative approaches. Moreover, we find that for nonlocal four
quark condensate the previous vacuum saturation assumption is not a good
approximation even at the mean field level.


title: Multifragmentation of charge asymmetric nuclear systems

abstract:
  The multifragmentation of excited spherical nuclear sources with various N/Z
ratios and fixed mass number is studied within dynamical and statistical
models. The dynamical model treats the multifragmentation process as a final
stage of the growth of density fluctuations in unstable expanding nuclear
matter. The statistical model makes a choice of the final multifragment
configuration according to its statistical weight at a global thermal
equilibrium. Similarities and differences in the predictions of the two models
on the isotopic composition of the produced fragments are presented and the
most sensitive observable characteristics are discussed.


title:
Scaling of particle production with number of participants in
  high-energy A+A collisions in the parton-cascade model

abstract:
  In view of the recent WA98 data of $\pi^0$ spectra from central Pb+Pb
collisions at the CERN SPS, we analyze the production of neutral pions for A+A
collisions across the periodic table at $\sqrt{s}=17$ AGeV and 200 AGeV within
the framework of the parton-cascade model for relativistic heavy ion
collisions. The multiplicity of the pions (having $p_T > 0.5$ GeV) in the
central rapidity region, is seen to scale as $\sim (N_{part})^{\alpha}$, where
$N_{part}$ is the number of participating nucleons, which we have approximated
as 2A for central collisions of identical nuclei. We argue that the deviation
of $\alpha$ ($\simeq 1.2$) from unity may have its origin in the multiple
scattering suffered by the partons. We also find that the constant of
proportionality in the above scaling relation increases substantially in going
from SPS to RHIC energies. This would imply that the (semi)hard partonic
activity becomes a much cleaner signal above the soft particle production at
the higher energy of RHIC, and thus much less dependent on the (lack of)
understanding of the underlying soft physics background.


title:
Use of the double dispersion relation in QCD sum rules with external
  fields

abstract:
  In QCD sum rules with external fields, the double dispersion relation is
often used to represent the correlation function. In this work, we point out
that the double spectral density, when it is determined by successive
applications of the Borel transformation, contains the spurious terms which
should be kept in the subtraction terms in the double dispersion relation. They
are zero under the Borel transformation but, if the dispersion integral is
restricted with QCD duality, they contribute to the continuum. For the simple
case with zero external momentum, it is shown that subtracting out the spurious
terms is equivalent to the QCD sum rules represented by the single dispersion
relation.


title: The Canonical Nuclear Many-Body Problem as a Rigorous Effective Theory

abstract:
  The shell model is the standard tool for addressing the canonical nuclear
many-body problem of nonrelativistic nucleons interacting through a static
potential. We discuss several of the uncontrolled approximations that are made
in this model to motivate a different approach, one based on an exact solution
of the Bloch-Horowitz equation. We argue that the necessary self-consistent
solutions of this equation can be obtained efficiently by a Green's function
expansion based on the Lanczos algorithm. The resulting effective theory is
carried out for the simplest nuclei, d and 3He, using realistic NN interactions
such as the Argonne v18 and Reid93 potentials, in order to contrast the results
with the shell model. We discuss the wave function normalization, the evolution
of the wave function as the "shell model" space is varied, and the magnetic
elastic effective operator. The numerical results show a simple renormalization
group behavior that differs from effective field theory treatments of the two-
and three-body problems. The likely origin of this scaling is discussed.


title: Multiple pion production from an oriented chiral condensate

abstract:
  We consider an ``oriented'' chiral condensate produced in the squeezed states
of the effective field theory with time- and space-dependent pion mass
parameter. We discuss the general properties of the solution, identifying
condensate modes and determining the resulting pion distributions. The
implementation of the dynamics in the form of sudden perturbation allows us to
look for exact solutions. In the region of condensation, the dramatic increase
in pion production and charge fluctuations are demonstrated.


title:
Polarization transfer observables for quasielastic proton-nucleus
  scattering in terms of a complete Lorentz invariant representation of the NN
  scattering matrix

abstract:
  For the calculation of polarization transfer observables for quasielastic
scattering of protons on nuclei, a formalism in the context of the Relativistic
Plane Wave Impulse Approximation is developed, in which the interaction matrix
is expanded in terms of a complete set of 44 independent invariant amplitudes.
A boson-exchange model is used to predict the 39 amplitudes which were omitted
in the formerly used five-term parameterization(the SPVAT form) of the
nucleon-nucleon scattering matrix. Use of the complete set of amplitudes
eliminates the arbitrariness of the five-term representation.


title: Off-shell effects on particle production

abstract:
  We investigate the observable effects of off-shell propagation of nucleons in
heavy-ion collisions at SIS energies. Within a semi-classical BUU transport
model we find a strong enhancement of subthreshold particle production when
off-shell nucleons are propagated.


title:
Electron-deuteron scattering in a current-conserving description of
  relativistic bound states: including meson-exchange-current contributions

abstract:
  Using a three-dimensional formalism that includes relativistic kinematics,
the effects of negative-energy states, approximate boosts of the two-body
system, and current conservation we calculate the electromagnetic form factors
of the deuteron up to $Q^2=6$ GeV$^2$. This is done both in impulse
approximation and with a $\rho \pi \gamma$ meson-exchange current included. The
experimentally-measured quantities $A$, $B$, and $T_{20}$ are calculated over
the kinematic range probed in recent Jefferson Laboratory experiments. The
meson-exchange current provides significant strength in $A$ at large $Q^2$, but
has little impact on $B$ or $T_{20}$.


title: $\rho$ meson broadening and dilepton production in heavy ion collisions

abstract:
  The modification of the width of the rho meson due to in-medium decays and
collisions is evaluated. In high temperature and/or high density hadronic
matter, the collision width is much larger than the one-loop decay width. The
large width of the $\rho$ meson in matter seems to be consistent with some
current interpretations of the $e^+ e^-$ mass spectra measured at the CERN/SPS.


title: Particle Freeze-out and Discontinuities in Relativistic Hydrodynamics

abstract:
  Freeze-out of particles in relativistic hydrodynamics is considered across a
3-dimensional space-time hypersurface. The conservation laws for time-like
parts of the freeze-out hypersurface require different values of temperature,
baryonic chemical potential and flow velocity in the fluid and in the final
particle spectra. We analyze this freeze-out discontinuity and its connection
to the shock-wave phenomena in relativistic hydrodynamics.


title: The H-Dibaryon and the Hard Core

abstract:
  The H dibaryon, a single, triply magic bag containing two up, two down and
two strange quarks, has long been sought after in a variety of experiments. Its
creation has been attempted in $K^-$, proton and most recently in relativistic
heavy ion induced reactions. We concentrate on the latter, but our conclusions
are more generally applicable. The two baryons coalescing to form the single
dibaryon, likely $\Lambda \Lambda$ in the case of heavy ions, must penetrate
the short range repulsive barrier which is expected to exist between them. We
find that this barrier can profoundly affect the probability of producing the H
state, should it actually exist.