title:
Positivity restrictions to the transverse polarization of the
  inclusively detected spin-half baryons in unpolarized electron-positron
  annihilation

abstract:
  The positivity constraints to the structure functions for the inclusive
spin-half baryon production by a time-like photon fragmentation are
investigated. One conclusion is that $\hat F$, which arises from the hadronic
final-state interactions, is subjected to an inequality between its absolute
value and the two spin-independent structure functions. On the basis of this
finding, we derive a formula through which the upper limits can be given for
the transverse polarization of the inclusively detected spin-half baryons in
unpolarized electron-positron annihilation. The derived upper bound supplies a
consistency check for the judgement of reliability of experimental data and
model calculations.


title: Damping Rate of a Scalar Particle in Hot Scalar QED

abstract:
  In contrast to the damping of partons in a quark-gluon plasma, the damping of
a scalar particle in a hot scalar QED plasma can be calculated to leading order
for the whole momentum range using the Braaten-Pisarski method. In this way the
evolution of the logarithmic infrared singularity caused by the exchange of a
transverse photon from soft to hard momenta can be studied.


title:
Symmetry aspects of the pion leptoproduction and the upper limit of the
  Levelt-Mulders asymmetry

abstract:
  We examined the symmetry aspect of the semi-inclusive one-pion production in
the deep inelastic scattering of a lepton beam off an unpolarized nucleon
target, with an emphasis on the positivity restrictions on the corresponding
structure functions. In combination with the Callan-Gross-type relation between
two twist-two structure functions $W_1$ and $W_2$, we derived an upper bound on
the Levelt-Mulders asymmetry, which occurs when the lepton beam is
longitudinally polarized.


title:
Manifestation of $s\to \Lambda$ fragmentation matrix elements via
  transverse $\Lambda$ polarization in unpolarized $e^-e^+$ annihilation

abstract:
  Making use of the collinear expansion technique developed by Ellis, Furmanski
and Petrozio, and the special propagator concept invented by Qiu, we present a
factorization approach to the photon fragmentation tensor for the inclusive
Lambda hyperon production. As a result, the structure function $\tilde F$,
which is related to the transverse polarization of the inclusive Lambda hyperon
in unpolarized electron-positron annihilation, is expressed as a combination of
four parton fragmentation matrix elements. Since the inclusive $\Lambda$
production we considered is theoretically the simplest, our study can be taken
as a question to the operatability and practability of the first nonleading QCD
factorization theorem in the transverse $\Lambda$ polarization phenomena.


title: Faddeev equation for heavy baryons in the quark-diquark picture

abstract:
  We describe heavy baryons as bound states of a quark and a diquark. For this
purpose we derive the Faddeev equation for baryons containing a single heavy
quark from a Nambu-Jona-Lasinio type of model which is appropriately extended
to include also heavy quarks. The latter are treated in the heavy mass limit.
The heavy baryon Faddeev equation is then solved using a static approximation
for the exchanged quark.


title:
Non-perturbative effect in the nucleon structure function and the
  Gottfried sum

abstract:
  We investigate the non-perturbative effect in the nucleon structure function
and the Gottfried sum by using a non-perturbative quark propagator with lowest
dimensional condensate contributions from the QCD vacuum. It is shown that the
non-perturbative effect modifies the conventional quark-parton model formula of
the nucleon structure function at finite $Q^2$ and suggests a non-trivial $Q^2$
dependence in the Gottfried sum.


title: Asymptotic Freedom from Thermal and Vacuum Magnetization

abstract:
  We calculate the effective Lagrangian for a magnetic field in spinor, scalar
and vector QED. Connections are then made to $SU(N_C)$ Yang--Mills theory and
QCD. The magnetization and the corresponding effective charge are obtained from
the effective Lagrangian. The renormalized vacuum magnetization will depend on
the renormalization scale chosen. Regardless of this, the effective charge
decreasing with the magnetic field, as in QCD, corresponds to anti- screening
and asymptotic freedom. In spinor and scalar QED on the other hand, the
effective charge is increasing with the magnetic field, corresponding to
screening. Including effects due to finite temperature and density, we comment
on the effective charge in a degenerate fermion gas, increasing linearly with
the chemical potential. Neglecting the tachyonic mode, we find that in hot QCD
the effective charge is decreasing as the inverse temperature, in favor for the
formation of a quark-gluon plasma. However, including the real part of the
contribution from the tachyonic mode, we find instead an effective charge
increasing with the temperature. Including a thermal gluon mass, the effective
charge in hot QCD is group invariant (unlike in the two cases above), and
decreases logarithmically in accordance to the vacuum renormalization group
equation, with the temperature as the momentum scale.


title:
Computational Study of Baryon Number Violation in High Energy
  Electroweak Collisions

abstract:
  We use semiclassical methods to study processes which give rise to change of
topology and therefore to baryon number violation in the standard model. We
consider classically allowed processes, i.e.~energies above the sphaleron
barrier. We develop a computational procedure that allows us to solve the Yang
Mills equations of motion for spherically symmetric configurations and to
identify the particle numbers of the in- and out-states. A stochastic sampling
technique is then used to map the region spanned by the topology changing
solutions in the energy versus incoming particle number plane and, in
particular, to determine its lower boundary. A lower boundary which approaches
small particle number would be a strong indication that baryon number violation
would occur in high energy collisions, whereas a lower asymptote at large
particle number would be evidence of the contrary. With our method and the
computational resources we have had at our disposal, we have been able to
determine the lower boundary up to energies approximately equal to one and a
half time times the sphaleron energy and observed a 40\% decrease in particle
number with no sign of the particle number leveling off. However encouraging
this may be, the decrease in incoming particle number is only from particles 50
down to approximately 30. Nevertheless, the formalism we have established will
make it possible to extend the scope of this investigation and also to study
processes in the classically forbidden region, which we plan to do in the
future.


title: Experimental constraints on a stringy SU(5)$\times$U(1) model

abstract:
  We re-examine the phenomenological aspects of a recently proposed
string-derived SU(5)$\times$U(1) one-parameter supergravity model, and explore
the sensitivity of the model predictions to variations in the strong coupling
and the string unification scale. We also perform an analysis of the
constraints on the parameter space of the model in light of the recent Tevatron
trilepton data and the LEP~1.5 chargino and slepton data. We obtain
$m_{\chi^\pm_1}\gsim70\GeV$, which excludes one-third of the parameter space of
the model. The remainder of the parameter space should be probed by ongoing
analyses of the Tevatron trilepton data and forthcoming LEP~2 runs.


title: A Supersymmetric Theory of Flavor with Radiative Fermion Masses

abstract:
  Supersymmetric theories involving a spontaneously broken flavor symmetry can
lead to fermion masses which vanish at tree level but are generated by
radiative corrections. In the context of supersymmetric theories with minimal
low energy field content we discuss which fermion masses and mixings may be
obtained radiatively, and find that constraints from flavor changing
phenomenology imply that only the first generation fermion masses and some (but
not all) CKM mixings can naturally come from radiative corrections. We also
consider general conditions on theories of flavor which guarantee the existence
of tree level massless fermions while having non-trivial CKM matrix elements at
tree level. Two complete models of flavor are presented. In the first model,
all first generation fermion masses are radiatively generated. In the second
model, the electron and up quark mass are due to radiative corrections whereas
the down mass appears at tree level, as does a successful prediction for the
Cabibbo angle $\sin \theta_c = \sqrt{m_d/m_s}$.


title: Effective Potential Models for Hadrons

abstract:
  The aim of these lectures is to give a self-contained introduction to
nonrelativistic potential models, to their formulation as well as to their
possible applications. At the price of some lack of (in a mathematical sense)
rigorous derivations, we try to give a feeling and understanding for the
simplest conceivable method to extract the explicit form of the forces acting
between quarks from the interplay between experimental observations and
theoretical considerations. According to this spirit, we demonstrate, in
detail, how to obtain the underlying Hamiltonian and how to determine the
Lorentz structure of the quark--(anti-)quark interaction potential from
well-established experimental facts.


title:
Gauss Integration over Relativistic 3--Body Phase Space for
  1--Dimensional Distributions of $ 2 \to 3 $ Reaction

abstract:
  We present the analysis of the phase space geometry of 2 $\rightarrow$ 3
reaction for the general case of nonzero and unequal particle masses. Its
purpose is to elaborate an alternative approach to the problem of integration
over phase space which does not exploit the Monte Carlo principle. The fast and
effective algorithm of integration based on Gauss method is developed for
treating 1--dimensional distributions in two--particle invariant variables. The
algorithm is characterized by significantly improved accuracy and it can meet
requirements of interactive processing.


title:
Nonleptonic charmed meson decays: Quark diagrams and final-state
  interactions

abstract:
  Effects of final-state interactions in nonleptonic decays of charmed mesons
are studied in the framework of quark-diagram approach. For the case of u-d-s
flavour symmetry we discuss how the inelastic coupled-channel rescattering
effects (and, in particular, resonance formation in the final state) modify the
input quark-diagram weak amplitudes. It is shown that such inelastic effects
lead to the appearance of nonzero relative phases between various quark
diagrams, thus invalidating some of the conclusions drawn in the past within
the diagrammatical approach. The case of SU(3) symmetry-breaking in Cabibbo
once-forbidden $D^0$ decays is also studied in some detail.


title: Neutrino masses and mixing

abstract:
  The status of the problem of neutrino masses and mixing is shortly reviewed.
Different schemes of mixing of (Dirac or Majorana) massive neutrinos are
considered. The theory of neutrino oscillations in vacuum and in matter is
presented. Existing indications in favor of neutrino mixing are shortly
discussed.


title:
Improved description of threshold pion electroproduction in chiral
  perturbation theory

abstract:
  We investigate neutral pion electroproduction off protons in the framework of
heavy baryon chiral perturbation theory. The chiral expansion of the S--wave
multipoles $E_{0+}$ and $L_{0+}$ is carried out to three orders. There appear
several undetermined low--energy constants. Three are taken from a recent study
of the new TAPS threshold $\pi^0$ photoproduction data, one is fixed from the
proton Dirac form factor and the novel S--wave constants appearing at orders
$q^4$ and $q^5$ are determined from a best fit (constrained by resonance
exchange) to the recent NIKHEF and MAMI data at photon momentum transfer
squared $k^2 = -0.1 \, \, {\rm GeV}^2$. The inclusion of a particular set of
dimension five operators is forced upon the fit by a soft--pion theorem which
severely constrains the momentum dependence of the longitudinal S--wave
multipole $L_{0+}$ at order $q^4$. We give predictions for lower photon
virtualities for the various multipoles and differential cross sections.
Further improvements are briefly touched upon.


title: Wick's Theorem at Finite Temperature

abstract:
  We consider Wick's Theorem for finite temperature and finite volume systems.
Working at an operator level with a path ordered approach, we show that
contrary to claims in the literature, expectation values of normal ordered
products can be chosen to be zero and that results obtained are independent of
volume. Thus the path integral and operator approaches to finite temperature
and finite volume quantum field theories are indeed seen to be identical. The
conditions under which normal ordered products have simple symmetry properties
are also considered.


title: Searching for Invisibly Decaying Higgs Bosons at LEP II

abstract:
  We study the potential of LEP II to unravel the existence of invisibly
decaying Higgs bosons, predicted in a wide class of models. We perform a model
independent analysis, focusing our attention to the final state topologies
exhibiting $b \bar{b}$ or $\ell^+ \ell^-$ ($\ell=\mu$ or $e$) pairs and missing
energy. We carefully evaluate the signals and backgrounds, choosing appropriate
cuts to enhance the discovery limits. Our results demonstrate that LEP II is
capable of discovering such a Higgs boson for a wide range of masses and
couplings.


title:
Discrepancy-based error estimates for Quasi-Monte Carlo. I: General
  formalism

abstract:
  We show how information on the uniformity properties of a point set employed
in numerical multidimensional integration can be used to improve the error
estimate over the usual Monte Carlo one. We introduce a new measure of
(non-)uniformity for point sets, and derive explicit expressions for the
various entities that enter in such an improved error estimate. The use of
Feynman diagrams provides a transparent and straightforward way to compute this
improved error estimate.


title:
Decay constants and mixing parameters in a relativistic model for q\barQ
  system

abstract:
  We extend our recent work, in which the Dirac equation with a
``(asymptotically free) Coulomb + (Lorentz scalar $\gamma_0\sigma r$) linear ''
potential is used to obtain the light quark wavefunction for $q\bar Q$ mesons
in the limit $m_Q\to \infty$, to estimate the decay constant $f_P$ and the
mixing parameter $B$ of the pseudoscalar mesons. We compare our results for the
evolution of $f_P$ and $B$ with the meson mass $M_P$ to the non-relativistic
formulas for these quantities and show that there is a significant correction
in the subasymptotic region. For $\sigma =0.14{{\rm ~GeV}}^{-2}$ and $\lms
=0.240{\rm ~GeV}$ we obtain: $f_D =0.371\; ,\; f_{D_s}=0.442\; ,\; f_B=0.301\;
,\; f_{B_s}=0.368 {\rm ~GeV}$ and $B_D=0.88\; ,\; B_{D_s}=0.89\; ,\; B_B=0.95\;
,\; B_{B_s}=0.96\; ,\;$ and $B_K=0.60$.


title: Initial Particle Instability in Muon Collisions

abstract:
  I consider the process $\mu^+\mu^-\to e\bar{\nu}W^+$ in the case when the
effective mass of the $(e\bar\nu)$ system than the muon mass. In this case the
momentum transferred from the initial muon to the $e\bar\nu$ system (the
virtual neutrino momentum) can be both time--like and space--like. Since the
path of integration over $k^2$ goes through a pole at $k^2=0$, it gives a
divergent cross section. In the ideal case of large enough beams this
divergence disappears if the finite width $\Gamma$ of the initial muon is taken
into account. The obtained cross section corresponds to the flux of equivalent
neutrino, which coincides with that of muon (with some energy distribution). In
practice, the effect of final size of the muon beam reduces this cross section
very strong, and the effect is hardly observable.


title: The $e^+e^-$ pair production at $\mu^+\mu^-$ collider

abstract:
  The main source of \epe pair at $\mu^+\mu^-$ collider is incoherent process
$\mu^+\mu^-\to \mu^+\mu^-\epe$ with cross section about 10 mb (at muon energy 2
TeV). The corresponding distributions are discussed briefly. These pairs give
the dangerous background. The coherent production of \epe pairs here is
negligibly small.


title: Degenerate BESS at future $e^+e^-$ colliders

abstract:
  The sensitivity of future $e^+e^-$ colliders to the new physics deriving from
a model of strong electroweak symmetry breaking is discussed. The model
considered is an effective lagrangian description of Goldstone bosons and of
new vector resonances degenerate in mass.


title: The Scalar Contribution to $\tau \to K \pi \nu_\tau$

abstract:
  We consider the scalar form factor in $\tau \to K\pi \nu_\tau$ decays. It
receives contributions both from the scalar resonance $K_0^*(1430)$ and from
the scalar projection of off-shell vector resonances. We construct a model for
the hadronic current which includes the vector resonances $K^*(892)$ and
$K^*(1410)$ and the scalar resonance $K_0^*(1430)$. The parameters of the model
are fixed by matching to the $O(p^4)$ predictions of chiral perturbation
theory. Suitable angular correlations of the $K\pi$ system allow for a model
independent separation of the vector and scalar form factor. Numerical results
for the relevant structure functions are presented.


title: Color-Octet Contributions to $J/\psi$ Photoproduction

abstract:
  We have calculated the leading color-octet contributions to the production of
$J/\psi$ particles in photon-proton collisions. Using the values for the
color-octet matrix elements extracted from fits to prompt $J/\psi$ data at the
Tevatron, we demonstrate that distinctive color-octet signatures should be
visible in $J/\psi$ photoproduction. However, these predictions appear at
variance with recent experimental data obtained at HERA, indicating that the
phenomenological importance of the color-octet contributions is smaller than
expected from theoretical considerations and suggested by the Tevatron fits.


title:
Analytic O(alpha_s) Results for Bottom and Top Quark Production in e+ e-
  Collisions

abstract:
  We present a new derivation of the O(alpha_s) angular distribution of the
outgoing $q$-quark in the production process $e^+ e^- \to\gamma,Z\to
q\,\bar{q}(g)$. In our calculation, we express the three-particle phase-space
integration of the gluon-bremsstrahlung process in terms of a general set of
analytic integral solutions. A consistent treatment of the QCD one-loop
corrections to the axial-vector current deserves special attention. This is
relevant in the derivation of the forward-backward asymmetry predicted by the
standard model. Finally, we provide the full analytical solutions for the
differential rates in closed form and conclude with numerical estimates for
bottom and top quark production.


title:
Inclusive Hadron Production in Photon-Photon Collisions at
  Next-to-Leading Order

abstract:
  We study inclusive charged-hadron production in collisions of quasireal
photons at NLO in perturbative QCD, using fragmentation functions recently
extracted from PEP and LEP1 data. We superimpose the direct (DD),
single-resolved (DR), and double-resolved (RR) gamma-gamma channels. First, we
confront existing data taken by TASSO at PETRA and by MARK II at PEP with our
NLO calculations. We also make comparisons with the neutral-kaon to
charged-hadron ratio measured by MARK II. Then, we present NLO predictions for
LEP2, a next-generation e+e- linear collider (NLC) in the TESLA design, and a
Compton collider obtained by converting a NLC. We analyze transverse-momentum
and rapidity spectra with regard to the scale dependence, the interplay of the
DD, DR, and RR components, the sensitivity to the gluon density in the resolved
photon, and the influence of gluon fragmentation. It turns out that the
inclusive measurement of small-p_T hadrons at a Compton collider would greatly
constrain the gluon density of the photon and the gluon fragmentation function.


title: QCD Interference Effects of Heavy Particles Below Threshold

abstract:
  We consider how two classes of heavy particles: extra vector-like families,
and strongly interacting superpartners, manifest themselves below threshold, by
interference of virtual loops with normal QCD processes. Quantitative estimates
are presented.


title: The Strange Spin of the Nucleon

abstract:
  The recent series of experiments on polarized lepton-nucleon scattering have
provided a strange new twist in the story of the nucleon, some of whose aspects
are reviewed in these lectures. In the first lecture, we review some issues
arising in the analysis of the data on polarized structure functions, focusing
in particular on the importance and treatment of high-order QCD perturbation
theory. In the second lecture some possible interpretations of the ``EMC spin
effect" are reviewed, principally in the chiral soliton (Skyrmion) approach,
but also interpretations related to the axial $U(1)$ anomaly. This lecture also
discusses other indications from recent LEAR data for an $\bar{s} s$ component
in the nucleon wave function, and discusses test of a model for this component.
Finally, the third lecture reviews the implications of polarized structure
functions measurements for experiments to search for cold dark matter
particles, such as the lightest supersymmetric particle and the axion, after
reviewing briefly the astrophysical and cosmological evidence for cold dark
matter.


title: Screening Theorem for the Higgs Decays into the Gauge Boson Pairs

abstract:
  The radiative corrections to the decays of the neutral CP-even Higgs boson
$H$ into a longitudinal gauge boson pair, {\it i.e.}, $H \rightarrow Z_LZ_L$
and $W^+_LW^-_L$ are analyzed in the two Higgs doublet model by making use of
the equivalence theorem. The sensitivity of the decay rates to the masses of
the heavier Higgs bosons, charged $G^{\pm}$ and CP-odd neutral $A$ bosons as
well as CP-even neutral $h$ boson, is investigated. Though the width $\Gamma (H
\rightarrow Z_LZ_L)$ is insensitive to the masses of heavier Higgs bosons,
$\Gamma (H \rightarrow W^+_LW^-_L)$ is sensitive and the radiative corrections
are minimized for $m_G = m_A$. These results are explained completely on the
basis of a new screening theorem for the vertices, which is closely connected
with the custodial $SU(2)_V$ symmetry.


title: Parton Distributions of the Virtual Photon

abstract:
  We propose a generic ansatz for the extension of parton distributions of the
real photon to those of the virtual photon. Alternatives and approximations are
studied that allow closed-form parametrizations.


title:
QCD Radiative Correction to the Hadronic Annihilation Rate of $1^{+-}$
  Heavy Quarkonium

abstract:
  Hadronic annihilation rate of $1^{+-}$ heavy quarkonium is given to
next-to-leading order in $\alpha_s$ and leading order in $v^2$ using a recently
developed factorization formalism which is based on NRQCD. The result includes
both the annihilation of P-wave color-singlet $Q\bar{Q}$ component, and the
annihilation of S-wave color-octet $Q\bar{Q}$ component of the quarkonium. The
notorious infrared divergences due to soft gluons, i.e., the Logarithms
associated with the binding energy, encountered in previous perturbative
calculations of $1^{+-}$ quarkonium decays are found to be explicitly
cancelled, and a finite result for the decay width to order $\alpha_s^3$ is
then obtained.


title:
The Two-Photon Decay Mode of MSSM Higgs Bosons at the Large Hadron
  Collider

abstract:
  At the Large Hadron Collider (LHC), the CP-even Higgs bosons ($h^0$ and
$H^0$) of the Minimal Supersymmetric Standard Model (MSSM) will be searched for
mainly through their two-photon decay. We present a detailed analysis of the
production and two-photon decay of the CP-even Higgs bosons of MSSM at the LHC
by taking into account all the parameters of the model, especially the bilinear
parameter $\mu$ and the trilinear supersymmetry breaking parameter $A$.
Non-zero values of these parameters lead to significant mixing in the squark
sector, and, thus, affect the masses of Higgs bosons through radiative
corrections, as well as their couplings to squarks. The dependence of the cross
section for the production of Higgs, and its subsequent decay to two photons,
on various parameters of the MSSM is described in detail. The cross section
times the two-photon branching ratio of $h^0$ is of the order of 15--25~fb in
much of the parameter space that remains after imposing the present
experimental constraints on the parameters. For the $H^0$, the two-photon
branching ratio is only significant if it is light. With a light $H^0$ the
cross section times the branching ratio may be 200~fb or more.


title:
The Chiral Coupling Constants $\lb{1}$ and $\lb{2}$ from \pipi Phase
  Shifts

abstract:
  A Roy equation analysis of the available $\pi\pi$ phase shift data is
performed with the $I=0$ S- wave scattering length $a^0_0$ in the range
predicted by the one-loop standard chiral perturbation theory. A suitable
dispersive framework is developed to extract the chiral coupling constants
\lb{1}, \lb{2} and yields \lb{1}$=-1.70\pm0.15$ and \lb{2}$\approx 5.0$. We
remark on the implications of this determination to (combinations of) threshold
parameter predictions of the three lowest partial waves.


title: Introduction To The Symmetry Breaking Sector

abstract:
  The basic ingredients of the Spontaneous Symmetry Breaking Phenomenon and of
the Higgs Mechanism are reviewed in these lectures of pedagogical character.
Some relevant topics related with the breaking $\gs \rightarrow U(1)_{\rm em}$
are selected and discussed here. A brief survey of the experimental Higgs
particle searches and the theoretical limits on $\mh$ are also presented. The
main features of the most popular models of symmetry breaking beyond the
Standard Model are briefly considered. It includes a short summary of the Higgs
Sector in the Minimal SUSY Model, the basic ideas of Technicolor models and a
brief introduction to Strongly Interacting Scalar sectors and to the Effective
Chiral Lagrangian Approach to the Electroweak Theory.


title: A Collection of Polarized Parton Densities

abstract:
  A significant number of parameterizations for the polarized parton densities
have appeared in the literature. Using the CTEQ evolution package, these
distributions have been evolved consistently preparatory to compilation into an
integrated package in the spirit of PDFLIB by Plothow-Besch. Here, a comparison
of a few of the more recent distributions are made. (Presented during the
Workshop on the ``Prospects of Spin Physics at HERA'' held at DESY-Zeuthen,
Germany, 28-31 August 1995.)


title: Single Spin Asymmetries at RHIC

abstract:
  One purpose of this meeting is to assess the physics potential of HERA-N
Stage I. To develop a reasonable perspective, it is useful to look at other
spin experiments. For completeness, this report discusses some of the single
spin physics that has appeared in studies relating to the Relativistic Heavy
Ion Collider (RHIC). (Talk presented during the meeting on ``The Measurement of
Singly Polarized Collisions at HERA'' held at DESY-Zeuthen, Germany, 31
August-1 September 1995.)


title: Parity Invariance and Effective Light-Front Hamiltonians

abstract:
  In the light-front form of field theory, boost invariance is a manifest
symmetry. On the downside, parity and rotational invariance are not manifest,
leaving the possibility that approximations or incorrect renormalization might
lead to violations of these symmetries for physical observables. In this paper,
it is discussed how one can turn this deficiency into an advantage and utilize
parity violations (or the absence thereof) in practice for constraining
effective light-front Hamiltonians. More precisely, we will identify
observables that are both sensitive to parity violations and easily calculable
numerically in a non-perturbative framework and we will use these observables
to constrain the finite part of non-covariant counter-terms in effective
light-front Hamiltonians.


title:
Processes with the $t$-channel singularity in the physical region:
  finite beam sizes make cross sections finite

abstract:
  It is known that some high-energy processes have a $t$-channel singularity in
the physical region. In this paper we show that this singularity is regularized
if one takes into account the finite sizes of the colliding beams, i.e. the
realistic situation which takes place at high--energy colliders. On this way we
obtain the finite cross section which is linear proportional to the transverse
sizes of the colliding beams. As an application of the above result we study
the production of the single $W$ boson at $\mu^+\mu^-$ colliders in the
reaction $\mu ^- \mu ^+ \to e \bar \nu _e W^+ $. For the total energy $\sqrt
{s}\approx 95$ GeV and reasonable parameters of the muon beams the ``beam--size
'' dependent part of the cross section for this reaction is of the order of the
standard cross section of the $\mu ^- \mu ^+ \to \mu^- \bar \nu _{\mu} W^+ $
process.


title:
Deep-Inelastic Electroproduction of Neutrons in the Proton Fragmentation
  Region

abstract:
  Experiments at HERA looking for deep-inelastic electroproduction of neutrons
in the proton fragmentation region are in progress. They are aimed to measure
the pion structure function at small Bjorken $x$. The important condition for
such a study is to establish under what kinematical conditions the dominance of
the pion-pole graph in the process is guaranteed. We analyse other sources of
theleading neutron, in order to figure out the kinematical region where the
one-pion exchange dominates.


title: Single-photon signal from neutralinos at LEP2

abstract:
  The production of invisible pairs of lightest neutralinos accompanied by a
large-angle hard photon in the reaction $e^+ e^- \to \chi^0_1 \chi^0_1 \gamma$
is studied at LEP2 energies. The most general gaugino/higgsino composition of
the $\chi^0_1$ within the Minimal Supersymmetric Standard Model is assumed. The
spectrum of the observed photon is derived within the framework of the
$p_t$-dependent structure-function approach, whose accuracy is assessed to be
within the foreseen experimental accuracy at LEP2. Higher-order QED corrections
due to undetected initial-state radiation are also included. A comparison with
the Standard Model main background from $e^+ e^- \to \nu \bar \nu \gamma$ is
performed for optimized photon kinematical cuts. Quantitative conclusions on
the signal/background ratio are given for a wide range of values of the SUSY
parameters.


title: Phenomenological implications of light stop and higgsinos

abstract:
  We examine the phenomenological implications of light $\tilde{t}_R$ and
higgsinos in the Minimal Supersymmetric Standard Model, assuming $\tan^2 \beta
< m_t / m_b$ and heavy $\tilde{t}_L$ and gauginos. In this simplified setting,
we study the contributions to $\Delta m_{B_d}$, $\epsilon_K$, $BR(b \rightarrow
s \gamma)$, $R_b \equiv \Gamma (Z \rightarrow b \overline{b}) / \Gamma ( Z \to
  {\rm hadrons})$, $BR(t \to b W)$, and their interplay.


title:
Next-To-Leading Order Analysis of Polarized and Unpolarized Structure
  Functions

abstract:
  We present numerical solutions of the $Q^2$ evolution equations at
next-to-leading order (NLO) for unpolarized and polarized parton distributions,
in both the flavor non-singlet and singlet channels. The numerical method is
based on a contour integration algorithm in complex-moment space, and, unlike
most standard fitting techniques, is not restricted to the use of analytic
moments of distributions. We also compute analytic continuations of the
recently calculated singlet anomalous dimensions, needed for evolving polarized
quark and gluon distributions at NLO. Using these we study the NLO effects on
the $x$ dependence of the spin-dependent structure functions $g_1^p$ and
$g_1^n$.


title: Extracting $R_b$ and $R_c$ Without Flavor Tagging

abstract:
  At present, two outstanding discrepancies between experiment and the standard
model are the measurements of the hadronic branching fractions $R_b$ and $R_c$.
We note that an independent measurement of these branching fractions may be
obtained from the width of hadronic $Z$ decays with a prompt photon,
$\Gamma_{qq\gamma}$, along with the total hadronic decay rate, $\Gamma_{had}$,
and an additional theoretical assumption. Such an analysis requires no flavor
tagging. We consider several plausible theoretical assumptions and find that
the current value of $\Gamma_{qq\gamma}$ favors larger $R_b$ and smaller $R_c$
relative to standard model predictions, in accord with the direct measurements.
If $\Gamma_{qq\gamma}$ and $\Gamma_{had}$ are combined with the direct
measurements, generation-blind corrections to all up-type and all down-type
quark widths are most favored. An updated measurement of $\Gamma_{qq\gamma}$
with the currently available LEP data is likely to provide an even stronger
constraint on both the branching fraction discrepancies and their possible
non-standard model sources.


title: Supernatural Inflation

abstract:
  Most models of inflation have small parameters, either to guarantee
sufficient inflation or the correct magnitude of the density perturbations. In
this paper we show that, in supersymmetric theories with weak scale
supersymmetry breaking, one can construct viable inflationary models in which
the requisite parameters appear naturally in the form of the ratio of mass
scales that are already present in the theory. Successful inflationary models
can be constructed from the flat-direction fields of a renormalizable
supersymmetric potential, and such models can be realized even in the context
of a simple GUT extension of the MSSM. We evade naive ``naturalness" arguments
by allowing for more than one field to be relevant to inflation, as in ``hybrid
inflation" models, and we argue that this is the most natural possibility if
inflaton fields are to be associated with flat direction fields of a
supersymmetric theory. Such models predict a very low Hubble constant during
inflation, of order $10^3$-$10^4$ GeV, a scalar density perturbation index $n$
which is very close to or greater than unity, and negligible tensor
perturbations. In addition, these models lead to a large spike in the density
perturbation spectrum at short wavelengths.


title: Production of pseudoscalar Higgs-bosons in $e\,\gamma$ collisions

abstract:
  We investigate the production of a pseudoscalar Higgs-boson $A^0$ using the
reaction $e\,\gamma\rightarrow e\,A^0$ at an $e\bar{e}$ collider with center of
mass energy of 500 GeV. Supersymmetric contributions are included and provide a
substantial enhancement to the cross section for most values of the symmetry
breaking parameters. We find that, despite the penalty incurred in converting
one of the beams into a source of backscattered photons, the $e\, \gamma$
process is a promising channel for the detection of the $A^0$.


title: Photoproduction of J/$\psi$ in the forward region

abstract:
  We study the phenomenology of fixed-target elastic $J/\psi$ photoproduction
in the NRQCD factorization formalism. Our the goal is to test an essential
feature of this formalism --- the color-octet mechanism. We obtain an
order-of-magnitude estimate for a certain linear combination of NRQCD
color-octet matrix elements. Our estimate is consistent with other empirical
determinations and with the $v$-scaling rules of NRQCD.


title: Hyperon weak radiative decays in chiral perturbation theory

abstract:
  We investigate the leading-order amplitudes for weak radiative decays of
hyperons in chiral perturbation theory. We consistently include contributions
from the next-to-leading order weak-interaction Lagrangian. It is shown that
due to these terms Hara's theorem is violated. The data for the decays of
charged hyperons can be easily accounted for. However, at this order in the
chiral expansion, the four amplitudes for the decays of neutral hyperons
satisfy relations which are in disagreement with the data. The asymmetry
parameters for all the decays can not be accounted for without higher-order
terms. We shortly comment on the effect of the 27-plet part of the weak
interaction.


title: Extensions of the Standard Model

abstract:
  Rapporteur talk at the International Europhysics Conference on High Energy
Physics, Brussels (Belgium), July 27-August 2, 1995. This talk begins with a
brief general introduction to the extensions of the Standard Model, reviewing
the ideology of effective field theories and its practical implications. The
central part deals with candidate extensions near the Fermi scale, focusing on
some phenomenological aspects of the Minimal Supersymmetric Standard Model. The
final part discusses some possible low-energy implications of further
extensions near the Planck scale, namely superstring theories.


title: Optimal Renormalization Scales and Commensurate Scale Relations

abstract:
  Commensurate scale relations relate observables to observables and thus are
independent of theoretical conventions, such as the choice of intermediate
renormalization scheme. The physical quantities are related at commensurate
scales which satisfy a transitivity rule which ensures that predictions are
independent of the choice of an intermediate renormalization scheme. QCD can
thus be tested in a new and precise way by checking that the observables track
both in their relative normalization and in their commensurate scale
dependence. For example, the radiative corrections to the Bjorken sum rule at a
given momentum transfer $Q$ can be predicted from measurements of the e+e-
annihilation cross section at a corresponding commensurate energy scale $\sqrt
s \propto Q,$ thus generalizing Crewther's relation to non-conformal QCD. The
coefficients that appear in this perturbative expansion take the form of a
simple geometric series and thus have no renormalon divergent behavior. We also
discuss scale-fixed relations between the threshold corrections to the heavy
quark production cross section in e+e- annihilation and the heavy quark
coupling $\alpha_V$ which is measurable in lattice gauge theory.


title: Heavy quark coefficient functions at asymptotic values $Q^2 \gg m^2$

abstract:
  In this paper we present the analytic form of the heavy-quark coefficient
functions for deep-inelastic lepton-hadron scattering in the kinematical regime
$Q^2 \gg m^2$ . Here $Q^2$ and $m^2$ stand for the masses squared of the
virtual photon and heavy quark respectively. The calculations have been
performed up to next-to-leading order in the strong coupling constant
$\alpha_s$ using operator product expansion techniques. Apart from a check on
earlier calculations, which however are only accessible via large computer
programs, the asymptotic forms of the coefficient functions are useful for
charm production at HERA when the condition $Q^2 \gg m_c^2$ is satisfied.
Furthermore the analytical expressions can also be used when one applies the
variable heavy flavour scheme up to next-to-leading order in $\alpha_s$.


title:
GUT Scale Threshold Corrections in a Complete Supersymmetric SO(10)
  Model: $\alpha_s(M_Z)$ vs. Proton Lifetime

abstract:
  We show that one loop GUT scale threshold corrections to gauge couplings are
a significant constraint on the GUT symmetry breaking sector of the theory. The
one loop threshold corrections relate the prediction for $\alpha_s(M_Z)$ to the
proton lifetime. We have calculated these corrections in a new complete SO(10)
SUSY GUT. The results are consistent with the low energy measurement of
$\alpha_s(M_Z)$. We have also calculated the proton lifetime and branching
ratios in this model. We show that proton decay rates provide a powerful test
for theories of fermion masses.


title:
Longitudinal Z-boson pair production via gluon fusion in technicolor
  models

abstract:
  We study the coupling of two longitudinal Z-bosons to two gluons via
technicolor interactions. Noticing a similarity of this process to $2 \gamma
\rightarrow 2 \pi^{0}$, we calculate the amplitude in chiral perturbation
theory in one-generation technicolor model. At the invariant mass of $
Z_{L}Z_{L}$ above the colored pseudo-Goldstone boson threshold, we find the
signal in proton collisions at $\sqrt{s} = 14\, TeV$ is stronger than the
standard model background by an order of magnitude, and is large enough to be
easily observable at LHC.
  The cross section for $W_{L}^{+}W_{L}^{-}$ pair production is also presented.


title: Phenomenology of the Top Mass in Realistic Extended Technicolor Models

abstract:
  Extended technicolor (ETC) theories typically require ETC gauge bosons
lighter than of order 1 TeV, to perturbatively generate the $t$ quark mass. We
point out that explicit models of $t-b$ mass splitting also typically contain
additional TeV scale ETC gauge bosons transforming in the {\it adjoint} of
technicolor, leading to large weak-isospin-breaking effects observable in the
$\rho$ parameter. Viable ETC models may thus require a lowest ETC scale of
order 10 TeV, with relatively strong and finely tuned couplings to generate
$m_t$. Such models do not generate observable corrections to the $Zb{\bar b}$
vertex.


title: Hadrophilic Z':a bridge from LEP1, SLC and CDF to LEP2 anomalies

abstract:
  In order to explain possible departures from the Standard Model predictions
for $b\bar b$ and $c\bar c$ production at $Z$ peak, we propose the existence of
a $Z'$ vector boson with enhanced couplings to quarks. We first show that this
proposal is perfectly consistent with the full set of LEP1/SLC results. In
particular, $Z-Z'$ mixing effects naturally explain the fact that $\Gamma_b$
and $\Gamma_c$ deviate from the SM in opposite directions. We then show that
there is a predicted range for enhanced $Z'q\bar q$ couplings which explains,
for a precise and interesting range of $Z'$ masses, the excess of dijet events
seen at CDF. A $Z'$ with such couplings and mass would produce clean
  observable effects in $b\bar b$ and in total hadronic production at LEP2.


title: Semi-leptonic B decays into higher charmed resonances

abstract:
  We apply HQET to semi-leptonic $B$ meson decays into a variety of excited
charm states. Using three realistic meson models with fermionic light degrees
of freedom, we examine the extent that the sum of exclusive single charmed
states account for the inclusive semi-leptonic $B$ decay rate. The consistency
of form factors with the Bjorken and Voloshin sum rules is also investigated.


title: Measuring Multijet Structure of Hadronic Energy Flow Or What IS A Jet?

abstract:
  Ambiguities of jet algorithms are reinterpreted as instability wrt small
variations of input. Optimal stability occurs for observables possessing
property of calorimetric continuity (C-continuity) predetermined by kinematical
structure of calorimetric detectors. The so-called C-correlators form a basic
class of such observables and fit naturally into QFT framework, allowing
systematic theoretical studies. A few rules generate other C-continuous
observables. The resulting C-algebra correctly quantifies any feature of
multijet structure such as the "number of jets" and mass spectra of "multijet
substates". The new observables are physically equivalent to traditional ones
but can be computed from final states bypassing jet algorithms which reemerge
as a tool of approximate computation of C-observables from data with all
ambiguities under analytical control and an optimal recombination criterion
minimizing approximation errors.


title: Analysis of rho-omega interference in the pion form-factor

abstract:
  The formalism underlying the analysis of e+e- -> pi+pi- in the rho-omega
interference region is carefully revisited. We show that the standard neglect
of the pure I=0 omega, omega_I, `direct'' coupling to pi-pi is not valid, and
extract those combinations of the direct coupling and \rho-omega mixing allowed
by experiment. The latter is shown to be only very weakly constrained by
experiment, and we conclude that data from the e+e- -> pi+pi- interference
region cannot be used to fix the value of rho-omega mixing in a
model-independent way unless the errors on the experimental phase can be
significantly reduced. Certain other modifications of the usual formalism
necessitated by the unavoidable momentum-dependence of rho-omega mixing are
also discussed.


title: Hadronic Light-by-light Scattering Contribution to Muon $ g - 2 $

abstract:
  The hadronic light-by-light scattering contribution to muon $g-2$ is examined
based on the low energy effective theories of QCD, the Nambu-Jona-Lasinio model
and hidden local symmetry approach, supplemented by a general information
concerning the asymptotic behavior of QCD.
  Our result is $- 52 \times 10^{-11}$ with an uncertainty of $\pm 18 \times
10^{-11}$, which includes our best estimate of model dependence. This is within
the expected measurement uncertainty of $40\times 10^{-11}$ in the forthcoming
experiment at Brookhaven National Laboratory. Our result removes one of the
main theoretical obstacles in verifying the existence of the weak contribution
to the muon $g-2$.


title: High Energy Cosmic Neutrinos and the Equivalence Principle

abstract:
  Observation of the ultra-high energy neutrinos, in particular, detection of
$\nu_{\tau}$ from cosmologically distant sources like active galactic nuclei
(AGN) opens new possibilities to search for neutrino flavor conversion. We
consider effects of violation of the equivalence principle (VEP) on propagation
of these cosmic neutrinos. Two effects are studied: (1) the oscillations of
neutrinos due to the VEP in the gravitational field of our Galaxy and in the
intergalactic space, (2) the resonance flavor conversion driven by the
gravitational potential of the AGN. We show that the ultra-high energies of the
neutrinos as well as cosmological distances to the AGN, or strong AGN
gravitational potential will allow one to improve the accuracy of test of the
equivalence principle by 21 orders of magnitude for massless or degenerate
neutrinos ($\Delta f \sim 10^{-41}$) and at least by 12 orders of magnitude for
massive neutrinos ($\Delta f \sim 10^{-28} \times (\Delta m^2/1 {\rm eV}^2)$).
Experimental signatures of the transitions induced by the VEP are discussed.


title: LEP1-Quick

abstract:
  The theoretical background of the electroweak precision measurements at LEP1
is reviewed. The presentation is compact but specific enough to understand all
details.


title:
Polar Angle Dependence of the Alignment Polarization of Quarks Produced
  in e^+e^- Annihilation

abstract:
  We calculate one-loop radiative QCD corrections to the three polarized and
unpolarized structure functions that determine the beam-quark polar angle
dependence of the alignment (or longitudinal) polarization of light and heavy
quarks produced in e^+e^- annihilations. We present analytical and numerical
results for the alignment polarization and its polar angle dependence. We
discuss in some detail the zero-mass limit of our results and the role of the
anomalous spin-flip contributions to the polarization observables in the
zero-mass limit. Our discussion includes transverse and longitudinal beam
polarization effects.


title: J/Psi and Psi' Suppression in Hadronic Matter

abstract:
  We present a microscopic calculation of the breakup cross sections of
$J/\psi$ and $\psi'$ on pions and nucleons as a function of the kinetic energy.
These cross sections are used for the investigation of the $J/\psi$ to
continuum and $\psi'/J/\psi$ ratios in ultrarelativistic heavy ion collisions.
The contribution of produced comoving pions to the $\psi'/J/\psi$ signal is
calculated. While this model can account for the data, the uncertainties in the
parameter values do not allow to exclude the possibility of additional sources
for charmonium absorption, like a resonance gas or the quark gluon plasma.


title:
Structure Functions and Particle Production in the Cumulative Region:
  two different exponentials

abstract:
  In the framework of the recently proposed QCD based parton model for the
cumulative phenomena in the interactions with nuclei two mechanisms for
particle production, direct and spectator ones, are analysed. It is shown that
due to final state interactions the leading terms of the direct mechanism
contribution are cancelled and the spectator mechanism is the dominant one. It
leads to a smaller slope of the cumulative particle production rates compared
to the slope of the nuclear structure function in the cumulative region $x>1$,
in agreement with the recent experimental data.


title: Anomalous mesonic interactions near a chiral phase transition

abstract:
  Using constituent quarks coupled to a linear sigma model at nonzero
temperature, I show that many anomalous mesonic amplitudes, such as $\pi^0
\rightarrow \gamma \gamma$, vanish in a chirally symmetric phase. Processes
which are allowed, such as $\pi^0 \sigma \rightarrow \gamma \gamma$, are
computed to leading order in a loop expansion.


title: Gamma-Gamma Physics at LEP2

abstract:
  This report is an overview of the gamma-gamma physics capabilities of LEP2,
and covers the following topics: structure functions, equivalent photon
approximation, tagging conditions etc, soft and semihard physics, large-$p_t$
processes, heavy-quark physics, and exclusive channels.


title: $WW$ resonance and chiral Lagrangian

abstract:
  We discuss the sensitivity of the $e^+ e^- \rightarrow W^+ W^-$ cross section
at a future $e^+ e^-$ collider with $\sqrt{s}=500$GeV to the non-decoupling
effects of a techni-$\rho$ like vector resonance. The non-decoupling effects
are parametrized by the chiral coefficients of the electroweak chiral
perturbation theory. We define renormalization scale independent chiral
coefficients by subtracting the Standard Model loop contributions. We also
estimate the size of the decoupling effects of the techni-$\rho$ resonance by
using a phenomenological Lagrangian including the vector resonance.


title:
The global colour model of QCD and its relationship to the NJL model,
  chiral perturbation theory and other models

abstract:
  The Global Colour Model (GCM) of QCD is a very successful model. Not only is
it formally derivable from QCD but under various conditions it reduces to the
NJL model and also to Chiral Perturbation Theory, and to other models. Results
presented include the effective gluon propagator, the difference between
constituent and exact quark propagators, various meson and nucleon observables,
a new mass formula for the Nambu-Goldstone mesons of QCD, and the change in the
MIT bag constant in nuclei.


title:
Nonabelian Duality and Higgs Multiplets in Supersymmetric Grand Unified
  Theories

abstract:
  We consider strongly interacting supersymmetric gauge theories which break
dynamically the GUT symmetry and produce the light Higgs doublets naturally.
Two models we proposed in the previous articles are reanalyzed as two phases of
one theory and are shown to have desired features. Furthermore, employing
nonabelian duality proposed recently by Seiberg, we study the dual theory of
the above one and show that the low-energy physics of the original and dual
models are the same as expected. We note that the Higgs multiplets in the
original model are regarded as composite states of the elementary hyperquarks
in its dual theory. Theories with other hypercolors and similar matter contents
are also analyzed in the same way.


title:
Calculation of the Isgur-Wise function from a light-front constituent
  quark model

abstract:
  The space-like elastic form factor of heavy-light pseudoscalar mesons is
investigated within a light-front constituent quark model in order to evaluate
the Isgur-Wise form factor. The relativistic composition of the constituent
quark spins is properly taken into account using the Melosh rotations, and
various heavy-meson wave function are considered, including the eigenfunctions
of an effective light-front mass operator reproducing meson mass spectra. It is
shown that in a wide range of values of the recoil the Isgur-Wise form factor
exhibits a moderate dependence upon the choice of the heavy-meson wave function
and is mainly governed by the effects of the confinement scale.


title: Multiple Hard Parton Interactions at HERA

abstract:
  At HERA, the large flux of almost real photons accompanying the electron beam
leads to the copious photoproduction of jets. Regions of small momentum
fractions $x$ of the incoming particles are explored, where the density of
partons is high. As a result, the probability for more than one hard partonic
scattering occurring in a single $\gamma p$ collision could become significant.
It is well known that this effect modifies the contribution of jets (minijets)
to the total cross section. We discuss the latest HERA data on the total
$\gamma p$ cross section in this context. The possible effects of multiple hard
interactions on event shapes and jet cross sections at HERA have been studied
using Monte Carlo programs. We review some of the available results, which in
general indicate that the effects of multiple interactions should be
significant and may already be manifest in the existing HERA data.


title:
On dynamically generated parton distribution functions and their
  properties

abstract:
  The idea of ``dynamically'' generated parton distribution functions, based on
regular initial conditions at low momentum scale, is reanalyzed with particular
emphasize paid to its compatibility with the factorization mechanism. Basic
consequences of this approach are discussed and compared to those of the
conventional approach, employing singular initial distribution functions.


title:
Rb, Rc and Jet Distributions at the Tevatron in a Model with an extra
  vector boson

abstract:
  We show that the reported anomalies in $R_b$ and $R_c$ can be interpreted as
the effect of a heavy vector boson \zprime\ universally coupled to $u$- and
$d$-type quarks separately and nearly decoupled from leptons. This extra vector
boson could then also naturally explain the apparent excess of the jet rate at
large transverse momentum observed at CDF.


title: Soft Terms from Strings

abstract:
  We study the structure of the soft SUSY-breaking terms obtained from 4-D
Strings under the assumption of dilaton/moduli dominance in the process of SUSY
breaking. We first analyze in detail the dilaton-dominated limit because of its
finiteness properties and phenomenological predictivity, and second, we
consider the new features appearing when several moduli fields contribute to
SUSY breaking. In particular, we discuss in detail the case of symmetric
Abelian orbifolds. Although some qualitative features indeed change in the
multimoduli case with respect to the dilaton dominance one, the most natural
mass relations at low-energy, $m_l < m_q \simeq M_g$, are still similar. Only
in some very specific limits these relations might be reversed. We also study
the presence of tachyons pointing out that their possible existence may be, in
some cases, an interesting advantage in order to break extra gauge symmetries.
Finally, we compute explicitly the $\mu$ and $B$ parameters in the context of
the mechanism for generating a ``$\mu $-term'' by the K\"ahler potential, as
naturally implemented in orbifolds. It leads to the prediction $|tg\beta |=1$
at the String scale, independently of the Goldstino direction. It is worth
noticing that in this squeme the dilaton-dominated case, where there is no free
parameters, is excluded since it is not consistent with the measured value of
the top-quark mass. In this connection, low-energy charge and color breaking
minima are also discussed.


title: Solutions to the R_b, R_c and alpha_s puzzles by Vector Fermions

abstract:
  We propose two minimal extensions of Standard Model, both of which can easily
accommodate the recent puzzling observations about the excess in $R_b$, the
deficit in $R_c$ and the discrepancy in the low energy and high energy
determinations of $\alpha_{s}$. Each model requires three additional heavy
vectorial fermions in order to resolve the puzzles. The current
phenomenological constraints and the new potential phenomena are also
discussed.


title:
The Impossibility of Baryogenesis at a Second Order Electroweak Phase
  Transition

abstract:
  We investigate whether baryogenesis is possible at a second order electroweak
phase transition. We find that under rather general conditions, the departure
from thermal equilibrium is suppressed by the expansion rate of the Universe,
and hence baryon production is also suppressed by the expansion rate. We
conclude that if no additional sources of departure from thermal equilibrium
such as topological defects are present, then electroweak baryogenesis is ruled
out if the phase transition is second order or crossover. However, a
non-vanishing net baryon to entropy ratio {\it is} generated, and we provide
both upper and lower bounds for the result. Our technique is also applicable to
other baryogenesis mechanisms taking place during and immediately after a
second order phase transition. We estimate the lowest value of the transition
energy scale for which the resulting baryon to entropy ratio might be large
enough to explain observations.


title: Dilaton Supersymmetry Breaking

abstract:
  We argue that dilaton supersymmetry breaking in string derived supergravity
requires an effective superpotential which is not separable as a function of
the dilaton times a function of the moduli. We show that in a simple model with
hidden sector matter condensation and a dilaton independent term one can easily
obtain $|F_S| \not=0$. For a wide range of realistic model parameters
$|F_S|>>|F_T|$ and supersymmetry is mainly broken in the dilaton direction.


title: Second Class Current in QCD Sum Rules

abstract:
  Induced tensor charge of the nucleon $g_T$, which originates from G-parity
violation, is evaluated from QCD sum rules. We find that $g_T/g_A$ with $g_A$
being the axial charge is $ -$0.0152 $\pm$ 0.0053 which is proportional to u-d
quark mass difference. This result is small compared to preliminary analysis of
the experiment, but is consistent with the estimate in the MIT bag model.


title: Recent Refinements in Higgs Physics

abstract:
  Recent refinements of the phenomenology of Higgs bosons in the Standard Model
and the Minimal Supersymmetric Standard Model are reviewed.


title: Supersymmetric Hints from Precision Electroweak Data?

abstract:
  The Standard Model does not provide a very good fit to the most recent
precision electroweak data from LEP, due primarily to the observed branching
ratios for $Z$ decay to $b\bar b$ and $c\bar c$. The possibility that an
extension of the Standard Model with low-energy supersymmetry can improve the
agreement between data and theory is considered.


title: Calculating Fermion masses in Superstring Derived Standard-like Models

abstract:
  I discuss the calculation of the heavy generation masses in the superstring
derived standard-like models. The top quark Yukawa coupling is obtained from a
cubic level mass term while the bottom quark and tau lepton mass terms are
obtained from nonrenormalizable terms. The calculation of the heavy fermion
Yukawa couplings is outlined in detail in a specific toy model. The dependence
of the effective bottom quark and tau lepton Yukawa couplings on the flat
directions at the string scale is examined. The gauge and Yukawa couplings are
extrapolated from the string unification scale to low energies. Agreement with
$\alpha_{strong}$, $sin^2\theta_W$ and $\alpha_{em}$ at M_Z is imposed, which
necessitates the existence of intermediate matter thresholds. The needed
intermediate matter thresholds exist in the specific toy model. The effect of
the intermediate matter thresholds on the extrapolated Yukawa couplings in
studied. It is observed that the intermediate matter thresholds also help to
maintain the correct $b/\tau$ mass relation. It is found that for a large
portion of the parameter space that the LEP precision data for
$\alpha_{strong}$, $sin^2\theta_W$ and $\alpha_{em}$, as well as the top quark
mass and the $b/\tau$ mass relation can all simultaneously be consistent with
the superstring derived standard-like models. Possible corrections due to the
supersymmetric mass spectrum are studied as well as the minimization of the
supersymmetric Higgs potential. It is demonstrated that the calculated values
of the Higgs VEV ratio, $tan\beta=v_1/v_2$, can be compatible with the
minimization of the one-loop effective Higgs potential.


title: Charmonium Production via Fragmentation at Higher Orders in alpha_s

abstract:
  Quarkonium production at a given large p_T is dominated by parton
fragmentation: a parton which is produced with transverse momentum p_T/z
fragments into a quarkonium state which carries a fraction z of the parton
momentum. Since parton production cross sections fall steeply with p_T, high z
fragmentation is favored. However, quantum number constraints may require the
emission of gluons in the fragmentation process, and this softens the z
dependence of the fragmentation function. We discuss the possibility that
higher- order processes may enhance the large z part of fragmentation functions
and thus contribute significantly to the quarkonium cross section. An explicit
calculation of light quark fragmentation into eta_c shows that the higher-order
process q -> q eta_c in fact dominates the lowest-order process q -> qg eta_c.


title:
Determination of Leading Twist Non-Singlet Operator Matrix Elements by
  QCD Sum Rules

abstract:
  We use QCD sum rules to determine the twist-two non-singlet operator matrix
elements and fixed x structure functions paying particular regard to the
estimate of the errors. Particularly for the matrix element determination, we
find large uncertainties due to radiative and higher dimension contributions.
We consider the origin of these large corrections and comment on their
consequences for other operator matrix element determinations.


title:
New Effective Feynman-like Rules for the Multi-Regge QCD Asymptotics of
  Inclusive Multijet Production

abstract:
  New effective Feynman-like rules are defined for inclusive multijet cross
sections in the multi-Regge regime. The solution of the BFKL equation is used
as a starting point. The resulting rules involve conformal weight and rapidity
as a momentum and a coordinate respectively and are translation invariant in
the coordinates. We use the effective rules to calculate ultra high energy
asymptotics of inclusive multijet production. The dependence on the parton
densities occurs only in the overall normalization of the asymptotic cross
sections.


title: Bounds on the Soft Pomeron Intercept

abstract:
  The Donnachie-Landshoff fit of total cross sections has now become a standard
reference for models of total, elastic and diffractive cross-sections. Adopting
their philosophy that simple-pole exchanges should account for all data to
present energies, we assess the uncertainties on their fits. Our best estimate
for the pomeron intercept is $1.096^{+0.012}_{-0.009}$, but several models have
a good chi square for intercepts in the range [1.07,1.11].


title:
A String Model with $SU(4)\times O(4)\times [Sp(4)]_{Hidden}$ Gauge
  Symmetry

abstract:
  In the four dimensional free fermionic formulation of the heterotic string, a
semi-realistic $SU(4)\times SU(2)_L \times SU(2)_R$ model is proposed with
three fermion generations in $(4,2,1)+(\bar 4,1,2)$ representations. The gauge
symmetry of the model breaks to the standard gauge group using a higgs pair in
the $(4,1,2)+(\bar 4,1,2)$ representations. The massless spectrum includes
exotic fractionally charged states with non -- trivial transformation
properties under part ($Sp(4)$) of the non -- abelian `hidden' symmetry.
Finally there is a mirror pair in $(4,2,1) , (\bar 4,2,1)$ allowing the
possibility for an identical running of $g_{4,L,R}$ couplings between the
string and $SU(4)$ breaking scales. This is of crucial importance for a
successful prediction of the weak mixing angle. Potential shortcomings and
problems of the construction are analysed and possible solutions are discussed.


title:
Is a high $P_T$ muon of the $e^+p \to \mu^+ X$ event observed at HERA a
  signature of the stop?

abstract:
  We investigate the $e^+p \to \mu^+ X$ event with high transverse momenta
observed at HERA (H1) and show that this event could be interpreted as a
signature of the single production of the scalar top quark in a supersymmetric
model with $R$-parity breaking interactions. The event topology of the H1 event
is rather characteristic and in fact it can be simulated by our specific
scenario if we reasonably choose our model parameters to be ({\romannumeral 1})
$m_{{\widetilde{d}},{\widetilde{b}}, {\widetilde{\nu}}}$
${{\stackrel{>}{\sim}}}$ $1$TeV [$0.8$TeV] for ${\lambda'_{131}}$ $=$ $0.1$
[$0.05$] and ({\romannumeral 2}) $m_{{\widetilde{W}}_{1}}$
${{\stackrel{<}{\sim}}}$ $150$GeV, $100$GeV ${{\stackrel{<}{\sim}}}$
$m_{{\widetilde{t}}_1}$ ${{\stackrel{<}{\sim}}}$ $200$GeV and
${\lambda'_{131}}$ ${{\stackrel{>}{\sim}}}$ $0.05$.


title: Effect of Quark Scatter on Baryogenesis by Electroweak Strings

abstract:
  The amount of baryon asymmetry generated by the electroweak strings at a
rough estimate is smaller than that generated by the bubble expansion since the
collapsing strings cannot cover the whole volume of the universe. However, the
interaction cross section of the strings with particles can be larger than the
geometrical area of the order of the string thickness. The scattering cross
section of quarks from the electroweak strings is calculated using Dirac
equation in the string background. It it proportional to the reverse of the
momentum perpendicular to the string axis. Thus the effective interaction area
can be enhanced at least ten times so that the suppression compared to the
first order phase transition scenario might be also improved.


title: Perturbative QCD analyses of the nonleptonic $B$ meson decays

abstract:
  Based on Brodsky-Lepage approach, the nonleptonic $B$ meson decay branching
ratio is derived in terms of three parameters and is geometrically analysed as
the 3-surface embedded in the 4-dimensional (abstract) Euclidean space
generated by the three parameters and $BR$. Investigating its 2-dimensional
sections, we find ranges for these parameters imposed by a comparison with
experimental data.


title: CKM Favored Semileptonic Decays of Heavy Hadrons at Zero Recoil

abstract:
  We study the properties of Cabibbo-Kobayashi-Maskawa (CKM) favored
semileptonic decays of mesons and baryons containing a heavy quark at the point
of no recoil. We first use a diagrammatic analysis to rederive the result
observed by earlier authors that at this kinematic point the $B$ meson decays
via $b\to c$ transitions can only produce a $D$ or $D^*$ meson. The result is
generalized to include photon emissions which violate heavy quark flavor
symmetry. We show that photons emitted by the heavy quarks and the charged
lepton are the only light particles that can decorate the decays $\bar{B}\to
D(D^*) + \ell\nu$ at zero recoil, and the similar processes of heavy baryons.
Implications for the determinations of the CKM parameter $V_{cb}$ are
discussed. Also studied in this paper is the connection between our
diagrammatic analysis of suppression of particle emission and the formal
observation based on weak currents at zero recoil being generators of heavy
quark symmetry. We show that the two approaches can be unified by considering
the Isgur-Wise function in the presence of an external source.


title: The NOMAD Experiment : Status Report

abstract:
  The NOMAD experiment has been designed to search for neutrino-tau appearance
in the CERN wide-band neutrino beam . The detector is now completed and has
been further improved. All subdetectors are working well. The experiment, where
the search for oscillation is based on kinematical criteria, will reach the
sensitivity dm2 > 0.7 eV2 for maximal mixing and dm2 > 50 eV2 for mixing angles
sin2 2\theta > 3.8E-4 after 2 years of running, making possible to explore a
region of cosmological interest. Preliminary measurements are presented from
the 1994 and 1995 data samples.


title: Charm nonleptonic decays and final state interactions

abstract:
  A global previous analysis of two-body nonleptonic decays of $D$ mesons has
been extended to the decays involving light scalar mesons. The allowance for
final state interaction also in nonresonant channels provides a fit of much
improved quality and with less symmetry breaking in the axial charges. We give
predictions for about 50 decay branching ratios yet to be measured. We also
discuss long distance contributions to the difference $\Delta \Gamma$ between
the $D_S$ and $D_L$ widths.


title: Meson masses within the model of induced nonlocal quark currents

abstract:
  The model of induced quark currents formulated in our recent paper (Phys.
Rev. D51, 176) is developed. The model being a kind of nonlocal extension of
the bosonization procedure is based on the hypothesis that the QCD vacuum is
realized by the (anti-)self-dual homogeneous gluon field. This vacuum field
provides the analytical quark confinement. It is shown that a particular form
of nonlocality of the quark and gluon propagators determined by the vacuum
field, an interaction of quark spin with the vacuum gluon field and a
localization of meson field at the center of masses of two quarks can explain
the distinctive features of meson spectrum: Regge trajectories of radial and
orbital excitations, mass splitting between pseudoscalar and vector mesons, the
asymptotic mass formulas in the heavy quark limit: $M_{Q\bar Q}\to 2m_Q$ for
quarkonia and $M_{Q\bar q}\to m_Q$ for heavy-light mesons. With a minimal set
of parameters (quark masses, vacuum field strength and the quark-gluon coupling
constant) the model describes to within ten percent inaccuracy the masses and
weak decay constants of mesons from all qualitatively different regions of the
spectrum.


title: On the Skyrme model prediction for the N-N spin-orbit force

abstract:
  In the framework of the product ansatz as an approximation for the two-baryon
system we review in details the derivation of the isoscalar nucleon-nucleon
spin orbit potential coming from the sixth order term of the extended Skyrme
model. We show that the sixth order term contributes with a positive sign, as
is the case for the Skyrme term, contrary to the claims of Riska and
Schwesinger. Those authors considered only one part of the force due to the
sixth order term and omitted the second part which turns out to be the dominant
one. Our result is independent of the parameters of the model.


title: No Mikheyev-Smirnov-Wolfenstein Effect in Maximal Mixing

abstract:
  We investigate the possible influence of the MSW effect on the expectations
for the solar neutrino experiments in the maximal mixing scenario suggested by
the atmospheric neutrino data. A direct numerical calculation of matter induced
effects in the Sun shows that the naive vacuum predictions are left completely
undisturbed in the particular case of maximal mixing, so that the MSW effect
turns out to be unobservable. We give a qualitative explanation of this result.


title: Definitions and upper bounds for unstable boson masses

abstract:
  We consider the problem of a proper definition of the mass of a heavy
unstable boson. It is shown how various definitions are related by the
renormalization-scheme independence of the full resummed amplitude. This is
made explicit for the $W$ boson in the large $N_f$ limit, where we find an
upper bound on the peak position of the lineshape and on the mass, provided a
sensible definition of the mass is used. In more realistic models, we
conjecture that under certain conditions the mass is similarly bounded. Using
this approach an upper limit of about 1 TeV on the mass of the
Minimal-Standard-Model Higgs boson is found, independent of any breakdown of
perturbation theory.


title: Effective Field Theories as Asymptotic Series: From QCD to Cosmology

abstract:
  We present some generic arguments demonstrating that an effective Lagrangian
$L_{eff}$ which, by definition, contains operators $O^n$ of arbitrary
dimensionality in general is not convergent, but rather an asymptotic series.
It means that the behavior of the far distant terms has a specific factorial
dependence $L_{eff}\sim \sum_n \frac{c_n O^n}{M^{n}},~c_n\sim n! ,~n\gg1$. We
discuss a few apparently different problems, which however have something in
common-- the aforementioned $n!-$ behavior:
  1.Effective long -distance theory describing the collective fields in QCD;
  2.Effective Berry phase potential which is obtained by integrating over the
fast degrees of freedom. As is known, the Berry potential is associated with
induced local gauge symmetry and might be relevant for the compactification
problem at the Planck scale.
  3.Nonlocal Lagrangians introduced by Georgi\cite{Georgi} for appropriate
treatment of the effective field theories without power expanding.
  4.The so-called improved action in lattice field theory where the new, higher
dimensional operators have been introduced into the theory in order to reduce
the lattice artifacts.
  5.Cosmological constant problem and vacuum expectation values in gravity. We
discuss some applications of this, seemingly pure academic phenomenon, to
various physical problems with typical energies from $1 GeV$ to the Plank
scale.


title:
Colour-octet Contributions to J/psi Hadroproduction at Fixed Target
  Energies

abstract:
  We investigate the integrated cross section for forward $\jpsi$ production in
proton-proton and pion-proton collisions at centre of mass energies upto 60
GeV. We find that colour-octet contributions to the cross section are crucially
important, and their inclusion produces a very good description of the data.
Since the values of non-perturbative matrix elements are fixed by other
experiments, these predictions are parameter-free.


title:
Polarized and Unpolarized Double Prompt Photon Production in Next to
  Leading Order QCD

abstract:
  We calculate $O(\alpha_s)$ corrections to inclusive and isolated double
prompt photon production, both for the unpolarized case, and for longitudinal
polarization of the incoming hadrons. The calculation is performed using purely
analytical techniques for the inclusive case, and a combination of analytical
and Monte Carlo techniques to perform the phase space integration in the
isolated case. A brief phenomenological study is made of the process
$pp\rightarrow \gamma \gamma X$ at CMS energies appropriate for the RHIC heavy
ion collider.


title: Parton distributions of real and virtual photons

abstract:
  Recent progress on the parton distribution functions of the photon, both real
and virtual, is briefly reviewed and experimental possibilities at HERA are
discussed.


title:
Constraining the Proton's Gluon Density by Inclusive Charm
  Electroproduction at HERA

abstract:
  We analyze the capability of charm production in deep-inelastic ep scattering
at HERA to constrain the gluon distribution g(y,\mu^2) of the proton. The
dependence of the theoretical predictions for the charm structure function
F_2^c on the mass factorization scale \mu and the charm mass is investigated.
F_2^c seems to be well suited for a rather clean and local gluon measurement at
small momentum fractions y.


title: Light Baryons in a Constituent Quark Model with Chiral Dynamics

abstract:
  It is shown from rigorous three-body Faddeev calculations that the masses of
all 14 lowest states in the $N$ and $\Delta$ spectra can be described within a
constituent quark model with a Goldstone-boson-exchange interaction plus linear
confinement between the constituent quarks.


title: Neutrino Mixing and Oscillations in Quantum Field Theory

abstract:
  We show that the generator of field mixing transformations in Quantum Field
Theory induces a non trivial structure in the vacuum which turns out to be a
coherent state, both for bosons and for fermions, although with a different
condensate structure. The Fock space for mixed fields is unitarily inequivalent
to the Fock space of the massive (free) fields in the infinite volume limit. As
a practical application we study neutrino mixing and oscillations. A new
oscillation formula is found where the oscillation amplitude is depressed, with
respect to the usual one, by a factor which is momentum and mass dependent. In
the relativistic limit, the usual formula is recovered. We finally discuss in
some detail phenomenological features of the modified oscillation formula.


title: Electroweak Radiative Corrections to AA -> W+W-

abstract:
  We discuss the complete virtual and soft-photonic O(alpha) corrections to AA
-> W+W- within the electroweak Standard Model for arbitrary polarized photons.
In the on-shell renormalization scheme for fixed M_W no leading corrections
associated with the running of alpha or heavy top-quark and Higgs-boson masses
occur. The corrections turn out to be of the order of 10%, but can become much
larger where the lowest-order cross-sections are suppressed.


title: IR-Renormalon Contribution to the Longitudinal Structure Function $F_L$

abstract:
  The available data on $F_L$ suggest the existence of unexpected large higher
twist contributions. We use the $1/N_f$ expansion to analyze the renormalon
contribution to the coefficient function of the longitudinal structure function
$F_L^{p-n}$. The renormalon ambiguity is calculated for all moments of the
structure function thus allowing to estimate the contribution of ``genuine''
twist-4 corrections as a function of Bjorken-$x$. The predictions turn out to
be in surprisingly good agreement with the experimental data.


title:
Problems for Supersymmetry Breaking by the Dilaton in Strings from
  Charge and Color Breaking

abstract:
  The general constraints on the parameter space of soft-breaking terms, in
order to avoid dangerous charge and color breaking minima, are applied to the
four-dimensional string scenario where the dilaton is the source of
supersymmetry breaking (dilaton-dominated limit). The results indicate that the
whole parameter space is excluded on these grounds after imposing the present
experimental data on the top mass. The inclusion of a non-vanishing
cosmological constant does not improve essentially the prospects. Possible
way-outs to this situation are briefly discussed.


title:
Naturally Light Higgs Doublet in the Spinor Representation of SUSY
  SO(10)

abstract:
  Within the supersymmetric SO(10) GUT we explore the possibility of the light
Higgs doublet being a member of the 16-dimensional spinorial representation.
This fact is ultimately related with the assumption that the light matter (at
least partially) resides in some of the tensor representations as well. Several
interesting features emerge. First, provided that the same 16-plet is
responsible for the breaking $SO(10) \rightarrow SU(5)$, the heaviness of the
top can automatically follow from the field content at $M_{GUT}$, without need
of any flavour symmetries. Secondly, the doublet--triplet splitting problem
receives a new natural solution. In addition, a dimension=5 (Higgsino mediated)
proton decay can be naturally suppressed. We construct explicit SO(10) models
with the above properties, with most general superpotentials under the
symmetries.


title: Calculating Scattering Amplitudes Efficiently

abstract:
  We review techniques for more efficient computation of perturbative
scattering amplitudes in gauge theory, in particular tree and one-loop
multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color
and helicity information to decompose amplitudes into smaller gauge-invariant
pieces, and (2) exploiting the analytic properties of these pieces, namely
their cuts and poles. Other useful tools include recursion relations, special
gauges and supersymmetric rearrangements.


title: $K_L \to \pi^0 e^+ e^-$ and $B \to X_s \ell^+ \ell^-$ Decay in the MSSM

abstract:
  The flavor changing neutral current processes $K_L \to \pi^0 e^+ e^-$, $B \to
X_s e^+ e^-$ and $B \to X_s \mu^+ \mu^-$ are studied within the minimal
supersymmetric extension of the Standard Model. We first examine the rates for
these decay modes in the MSSM with a universal soft supersymmetry breaking
sector at a Grand Unification scale. We later relax the universality condition
and investigate the FCNC transitions in a more general class of models with
negligible flavor violation in squark mixing matrices. We find that the MSSM
prediction for the kaon channel's branching fraction differs from its Standard
Model value by at most 30\% over the entire allowed parameter space. On the
other hand, supersymmetric contributions could potentially enhance certain $B
\to X_s \ell^+ \ell^-$ observables by more than 100\% relative to Standard
Model expectations. The impact of supersymmetry upon the $B$ meson modes is
strongly correlated with the MSSM value for the Wilson coefficient of the
magnetic moment operator that mediates $B \to X_s \gamma$.


title:
Topological Charge and $U(1)_A$ Symmetry in the High Temperature Phase
  of QCD

abstract:
  We discuss the global symmetries of the high temperature phase of QCD with
$N_f$ massless quarks. We show that the $U(N_f) \times U(N_f)$ symmetries are
only violated by operators of dimension $\geq 3 N_f$. For $N_f > 2$ this
implies that the thermal two-point correlation functions of the $\eta'$ and
$\pi^a$'s are identical. We discuss the implications of this for the chiral
phase transition at finite temperature.


title:
Detecting a Light Gravitino at Linear Collider to Probe the SUSY
  Breaking Scale

abstract:
  If supersymmetry is dynamically broken at a low scale ($M_{susy}$), within a
few orders of magnitude of the weak scale, then the lightest supersymmetric
partner is the gravitino and the next to lightest supersymmetric partner is a
neutralino $\chi^0_1$ with mass $m_{\chi^0_1}$, which can decay into a photon
($\gamma$) plus a gravitino ($\widetilde{G}$). We study the detection of
$e^{-}e^{+}\rightarrow \chi^0_1 \chi^0_1 \rightarrow
\gamma\widetilde{G}\gamma\widetilde{G}$ at the proposed Linear Collider, and
find the range of the parameters $M_{susy}$ and $m_{\chi^0_1}$ that can be
accessible with a right-hand polarized electron beam at $\sqrt{S}=500$\,GeV,
with 50\,${\rm fb}^{-1}$ integrated luminosity. We also discuss briefly the
accessible range for current electron and hadron colliders.


title: Rapidity Gaps in Deep Inelastic Scattering

abstract:
  A simple semiquantitative picture of diffractive electroproduction is
described. Although the diffractive component of $F_2$ is approximately
independent of $Q^2$ and $W^2$, this mechanism is "soft," i.e. it depends upon
large-distance physics and is not readily describable within perturbative QCD.


title:
Solving the Bethe-Salpeter Equation in Minkowski Space: Scalar Theories
  and Beyond

abstract:
  The Bethe-Salpeter equation (BSE) for bound states in scalar theories is
reformulated and solved in terms of a generalized spectral representation
directly in Minkowski space. This differs from the conventional approach, where
the BSE is solved in Euclidean space after a Wick rotation. For all but the
lowest-order (i.e., ladder) approximation to the scattering kernel, the {\it
naive} Wick rotation is invalid. Our approach generates the vertex function and
Bethe-Salpeter amplitude for the entire allowed range of momenta, whereas these
cannot be directly obtained from the Euclidean space solution. Our method is
quite general and can be applied even in cases where the Wick rotation is not
possible.


title: Soft Scalar Masses in String Models with Anomalous $U(1)$ symmetry

abstract:
  We obtain the low-energy effective theory from string models with anomalous
$U(1)$ symmetry. The feature of soft supersymmetry breaking scalar masses and
some phenomenological implications are discussed. We show that it is, in
general, difficult to keep the degeneracy and the positivity of squared soft
scalar masses at the Planck scale.


title: Electroweak baryogenesis with the vector-like quark model

abstract:
  We study on the electroweak baryogenesis problem in the vector-like quark
model. This model can add to the minimal standard model the extra CP-violation
source which breaks CP spontaneously. Using charge transport mechanism
suggested by Nelson et al, we can get the net hypercharge flux : $f_{Y} \sim
10^{-5}$. This result could nicely explain the present baryon to entropy ratio
: $\rho_{B}/s \sim 10^{-9}$.


title:
Experimental Signatures of Low Energy Gauge Mediated Supersymmetry
  Breaking

abstract:
  The experimental signatures for gauge mediated supersymmetry breaking are
presented. The phenomenology associated with this class of models is
distinctive since the gravitino is naturally the LSP. The next lightest
supersymmetric particle (NLSP) can be a gaugino, Higgsino, or right handed
slepton. Decay of the NLSP to its partner plus the LSP proceeds through the
Goldstino component of the gravitino. For a significant range of parameters
this decay can take place within the detector, and can be measured as a
displaced vertex or kink in a charged particle track. In the case that the NLSP
is mostly gaugino, we identify the discovery modes as $e^+e^- \rightarrow
\gamma \gamma + \Emiss$, and $p \bar{p} \rightarrow l^+ l^- \gamma \gamma +
\EmissT$. If the NLSP is a right handed slepton the discovery modes are $e^+
e^- \rightarrow l^+ l^- + \Emiss$ and $p \bar{p} \rightarrow l^+ l^- +
\EmissT$. An NLSP which is mostly Higgsino is also considered. Finally, these
theories can contain scalar particles which mediate sub-millimeter range
coherent forces of gravitational strength.


title:
Charged Higgs mass bound from the $b \to s \gamma$ process in the
  minimal supergravity

abstract:
  The constraint on the mass of the charged Higgs boson from the recent
measurement of the inclusive $b \rightarrow s \gamma$ decay is studied in a
framework of the minimal supergravity. It is shown that the lower bound for the
charged Higgs mass crucially depends on the sign of the higgsino mass parameter
($\mu$). For $\mu<0$, the bound exceeds 400 GeV when the ratio of two Higgs
vacuum expectation values ($\tan\beta$) is larger than 10. No strong bound is
obtained for $\mu>0$ due to cancellations between charged Higgs and
supersymmetric particle contributions.


title:
Heavy-to-heavy and heavy-to-light weak decay form factors in the
  light-front approach: the exclusive $ 0^- $ to $ 0^- $ case

abstract:
  Weak transition form factors among heavy pseudoscalar mesons are investigated
within a relativistic quark model formulated on the light-front. It is shown
that the light-front result derived in the time-like region for the matrix
elements of the plus component of the weak vector current coincides with the
spectator pole term of the quark triangle diagram. For the first time, the
dependence of the form factors on the squared four-momentum transfer $q^2$ is
calculated in the whole accessible kinematical region $0 \leq q^2 \leq
q^2_{max}$. For the numerical investigations of the semileptonic $B \to D \ell
\nu_{\ell}$, $B \to \pi \ell \nu_{\ell}$, $D \to K \ell \nu_{\ell}$ and $D \to
\pi \ell \nu_{\ell}$, the equal-time wave functions corresponding to the
updated version of the ISGW model are adopted. Our results for the form factors
and the decay rates are presented and compared with available experimental data
and predictions of different approaches. Moreover, the $K^0_L \to \pi^{\pm} ~
e^{\mp} ~ \nu_e$ decay is briefly discussed. Our approach is consistent with
experimental data.


title: The quark condensate in the GMOR relation

abstract:
  The quark condensate which enters the Gell-Mann-Oakes-Renner (GMOR) relation,
is investigated in the framework of one-gluon-exchange models. The usual
definition of the quark condensate via the trace of the quark propagator
produces a logarithmic divergent condensate. In the product of current mass and
condensate, this divergence is precisely compensated by the bare current mass.
The finite value of the product in fact does not contradict the relation
recently obtained by Cahill and Gunner. Therefore the GMOR relation is still
satisfied.


title: Multiparton Interactions in Photoproduction at HERA

abstract:
  The high energy photoproduction of jets is being observed at the ep collider,
HERA. It may be that the HERA centre-of-mass energy is sufficiently large that
the production of more than one pair of jets per ep collision becomes possible,
owing to the large number density of the probed gluons. We construct a Monte
Carlo model of such multiparton interactions and study their effects on a wide
range of physical observables. The conclusion is that multiple interactions
could have very significant effects upon the photoproduction final state and
that this would for example make extractions of the gluon density in the photon
rather difficult. Total rates for the production of many (i.e. > 2) jets could
provide direct evidence for the presence of multiple interactions, although
parton showering and hadronization significantly affect low transverse energy
jets.


title: The Non-Minimal Supersymmetric Standard Model at Large $\tan\beta$

abstract:
  We present a comprehensive analysis of the Non-Minimal Supersymmetric
Standard Model (NMSSM) for large values of $\tan\beta$, the ratio of the vacuum
expectation values of the two Higgs doublets, which arise when we impose the
constraint of the unification of Yukawa couplings in the model. In this limit
we show that the vacuum expectation value of the singlet is forced to be large,
of the order of $10$ TeV. The singlet decouples from the lightest CP-even
neutral Higgs boson and the neutralinos. We compare our results with the
corresponding particle spectrum of the Minimal Supersymmetric Standard Model in
the same limit. With the exception of the lightest Higgs boson, the particle
spectrum in the model turns out to be heavy. The Higgs boson mass, after the
inclusion of radiative corrections, is found to be in the neighbourhood of
$\sim 130$ GeV.


title: $U_A(1)$ symmetry restoration in QCD with $N_f$ flavors

abstract:
  Recently, there have been reports that the chirally restored phase of QCD is
effectively symmetric under $U(N_f) \times U(N_f)$ rather than $SU(N_f)\times
SU(N_f)$. We supplement their argument by including the contributions from
topologically nontrivial gauge field configurations and discuss how the
conclusions are modified. General statements are made concerning the particle
spectrum of QCD with light $N_f$ flavors in the high temperature chirally
restored phase.


title: Quasi Yukawa Fixed Point due to Decoupling of SUSY Particles

abstract:
  We study effects of SUSY particle decouplings on a quasi fixed point (QFP) of
Yukawa coupling. From renormalization group analysis it is shown that if the
SUSY breaking scale $M_S$ is large ($\simg 1$TeV), effects of decoupling of
Higgsinos and squarks raise the top Yukawa QFP. This tendency is enhanced in
most cases of non-universal SUSY breaking. For the case of $M_S\siml 1$TeV, the
decoupling of gluinos lowers $m_t^{\rm QFP}$. We checked some parameter
dependencies for the top Yukawa QFP. The bottom-top Yukawa unified case is also
studied. When top quark mass is measured more precisely, some patterns of soft
mass spectra could be excluded if rather large initial top Yukawa coupling is
realized by underlying theory.


title:
Wilson Renormalization Group formulation of Real Time thermal field
  theories

abstract:
  We apply Renormalization Group techniques to the Real Time formulation of
thermal field theory. Due to the separation between the $T=0$ and the $T\neq 0$
parts of the propagator in this formalism, one can derive exact evolution
equations for the Green functions describing the effect of integrating out
thermal fluctuations of increasing wavelengths, the initial conditions being
the renormalized Green functions of the $T=0$ theory. As a first application,
we study the phase transition for the real scalar theory, computing the order
of the transition, the critical temperature, and critical exponents, in
different approximations to the evolution equations for the scalar potential.


title: Nonrestoration of spontaneously broken P, CP and PQ at high temperature

abstract:
  The possibility of P and CP violation at high temperature in models where
these symmetries are spontaneously broken is investigated. It is found that in
minimal models that include singlet fields, high T nonrestoration is possible
for a wide range of parameters of the theory, in particular in models of CP
violation with a CP-odd Higgs field. The same holds true for the invisible
axion version of the Peccei-Quinn mechanism. This can provide both a way out
for the domain wall problem in these theories and the CP violation required for
baryogenesis. In the case of spontaneous P violation it turns out that high T
nonrestoration requires going beyond the minimal model.The results are shown to
hold true when next-to-leading order effects are considered.


title: Classical Preheating and Decoherence

abstract:
  We establish the equivalence between the quantum evolution of spatially
homogeneous oscillations of a scalar field and that of an analogous classical
system with certain random initial condition. We argue that this observation
can be used for numerical simulation of the Universe in the preheating epoch.
We also explicitly demonstrate that the phenomenon of parametric resonance that
leads to preheating is simultaneously an effective mechanism for generating
quantum decoherence of the Universe.


title: New Physics Effects on Higgs Production at $\gamma \gamma $ Colliders

abstract:
  We study heavy physics effects on the Higgs production in $\gamma \gamma $
fusion using the effective Lagrangian approach. We find that the effects coming
from new physics may enhance the standard model predictions for the number of
events expected in the final states $\bar bb$, $WW$, and $ZZ$ up to one order
of magnitude, whereas the corresponding number of events for the final state
$\bar tt$ may be enhanced up to two orders of magnitude.


title: The role of the pion cloud in electroproduction of the $\Delta$(1232)

abstract:
  We calculate the ratios $E2/M1$ and $C2/M1$ of the multipole amplitudes for
electroproduction of the $\Delta$(1232) in the range of photon virtuality
$0<-K^2<1$~GeV$^2$ in a chiral chromodielectric model and a linear
$\sigma$-model. We find that relatively large experimental values can be
explained in terms of the pion contribution alone; the contribution arising
from d-state quark admixture remains below 10\%. We describe the pion cloud as
a coherent state and use spin and isospin projection to obtain the physical
nucleon and the $\Delta$. The $A_{1/2}$ and $A_{3/2}$ amplitudes are reasonably
well reproduced in the $\sigma$-model; in the chromodielectric model, however,
they are a factor of two too small.


title:
Electromagnetic Annihilation Rates of $\chi_{c0}$ and $\chi_{c2}$ with
  Both Relativistic and QCD Radiative Corrections

abstract:
  We estimate the electromagnetic decay rates of $\chi_{c0}\rightarrow
\gamma\gamma$ and $\chi_{c2}\rightarrow\gamma\gamma$ by taking into account
both relativistic and QCD radiative corrections. The decay rates are derived in
the Bethe-Salpeter formalism and the QCD radiative corrections are included in
accordance with factorization assumption. Using a QCD-inspired interquark
potential, we obtain relativistic BS wavefunctions of $\chi_{c0}$ and
$\chi_{c2}$ by solving BS equations for the corresponding $^{2S+1}L_J$ states.
Our numerical result for the ratio
$R=\frac{\Gamma(\chi_{c0}\rightarrow\gamma\gamma)}{\Gamma(\chi_{c2}
\rightarrow\gamma\gamma)}$ is about $11-13$ which agrees with the update E760
experimental data. Explicit calculations show that the relativistic corrections
due to spin-dependent interquark forces induced by gluon exchange enhance the
ratio $R$ substantially and its value is insensitive to the choice of
parameters that characterize the interquark potential. Our expressions for the
decay widths are identical with that obtained in the NRQCD theory to the
next-to-leading order in $v^2$ and $\alpha_s$. Moreover, we have determined two
new coefficents in the nonperturbative matrix elements for these decay widths.


title:
Pseuduscalar Heavy Quarkonium Decays With Both Relativistic and QCD
  Radiative Corrections

abstract:
  We estimate the decay rates of $\eta_c\rightarrow 2\gamma$,
$\eta_c'\rightarrow 2\gamma$, and $J/\psi\rightarrow e^+ e^-$,
$\psi^\prime\rightarrow e^+e^-$, by taking into account both relativistic and
QCD radiative corrections. The decay amplitudes are derived in the
Bethe-Salpeter formalism. The Bethe-Salpeter equation with a QCD-inspired
interquark potential are used to calculate the wave functions and decay widths
for these $c\bar{c}$ states. We find that the relativistic correction to the
ratio $R\equiv \Gamma (\eta_c \rightarrow 2\gamma)/ \Gamma (J/ \psi \rightarrow
e^+ e^-)$ is negative and tends to compensate the positive contribution from
the QCD radiative correction. Our estimate gives $\Gamma(\eta_c \rightarrow
2\gamma)=(6-7) ~keV$ and $\Gamma(\eta_c^\prime \rightarrow 2\gamma)=2 ~keV$,
which are smaller than their nonrelativistic values. The hadronic widths
$\Gamma(\eta_c \rightarrow 2g)=(17-23) ~MeV$ and $\Gamma(\eta_c^\prime
\rightarrow 2g)=(5-7)~MeV$ are then indicated accordingly to the first order
QCD radiative correction, if $\alpha_s(m_c)=0.26-0.29$. The decay widths for
$b\bar b$ states are also estimated. We show that when making the assmption
that the quarks are on their mass shells our expressions for the decay widths
will become identical with that in the NRQCD theory to the next to leading
order of $v^2$ and $\alpha_s$.


title: Distinctive Signals of spontaneous R-parity breaking at LEP-II

abstract:
  We consider the signals of pair-produced charginos in an $e^{+}e^{-}$
collider, in a scenario where R-parity is spontaneously broken. The possibility
of lepton-chargino mixing, together with the presence of a Majoron, opens up
the two-body decay channel of a chargino into a tau and a Majoron. We have
studied the regions where this is the dominant decay of a chargino, and have
shown that over a large region of the parameter space the ensuing signals,
namely tau-pairs with missing-$p_T$, may rise well above standard model
backgrounds at LEP-II. Such signals can also enable one to distinguish between
spontaneous and explicit R-parity breaking.