title: A Lattice Construction of Chiral Gauge Theories

abstract:
  We formulate chiral gauge theories non-perturbatively, using two different
cuttoffs for the fermions and gauge bosons. We use a lattice with spacing $b$
to regulate the gauge fields in standard fashion, while computing the chiral
fermion determinant on a finer lattice with spacing $f << b$. This determinant
is computed in the background of $f$-lattice gauge fields, obtained by
gauge-covariantly interpolating $b$-lattice gauge fields. The notorious
doublers that plague lattice theories containing fermions are decoupled by the
addition of a Wilson term. In chiral theories such a term breaks gauge
invariance explicitly. However, the advantage of the two-cutoff regulator is
that gauge invariance can be restored to $O(f^2/b^2)$ by a {\it one-loop}
subtraction of calculable local gauge field counterterms. We show that the only
obstruction to this procedure is the presence of an uncancelled gauge anomaly
among the fermion representations. We conclude that for practical purposes, it
suffices to choose $f/b \sim b/L$, where $L^4$ is the physical volume of the
system. In our construction it is simple to prove the Adler-Bardeen theorem for
anomalies in global currents to all orders. The related subject of fermion
number violation is also studied. Finally, we discuss the prospects for
improving the efficiency of our algorithm.


title: Leptonic Constant from B Meson Radiative Decay

abstract:
  We propose a method to determine the leptonic decay constant $f_{B^*}$ in the
infinite heavy quark mass limit from the analysis of the radiative decay mode
$B^- \to \ell^- {\bar \nu}_\ell \gamma$. The method relies on HQET symmetries
and on experimental data from $D^{*0} \to D^0 \gamma$.


title: The Mellin Transform Technique for the Extraction of the Gluon Density

abstract:
  A new method is presented to determine the gluon density in the proton from
jet production in deeply inelastic scattering. By using the technique of Mellin
transforms not only for the solution of the scale evolution equation of the
parton densities but also for the evaluation of scattering cross sections, the
gluon density can be extracted in next-to-leading order QCD. The method
described in this paper is, however, more general, and can be used in
situations where a repeated fast numerical evaluation of scattering cross
sections for varying parton distribution functions is required.


title:
On probing the anomalous magnetic moments of vector leptoquarks in ep
  collisions

abstract:
  We study a possibility to measure the anomalous magnetic moment of vector
leptoquarks in reactions with single leptoquark production associated with hard
photon emission in ep collisions. For this purpose we propose to use the
radiative amplitude zero effect. We find that an exact radiative zero in the
angular distribution of the emitted photon is present only for pure Yang-Mills
coupling of photons to leptoquarks. As a result the cross section is sensitive
to the anomalous magnetic moment kappa of the leptoquark. This effect offers a
possibility to measure kappa with rather high accuracy. For LEP+LHC we
establish upper bounds in the plane leptoquark mass--anomalous magnetic moment.


title: A Dynamical Left--Right Symmetry Breaking Model

abstract:
  Left--right symmetry breaking in a model with composite Higgs scalars is
discussed. It is assumed that the low--energy degrees of freedom are just
fermions and gauge bosons and that the Higgs bosons are generated dynamically
through a set of gauge-- and parity--invariant 4-fermion operators. It is shown
that in a model with composite bi-doublet and two triplet scalars there is no
parity breaking at low energies, whereas in the model with two doublets instead
of two triplets parity is broken automatically regardless of the choice of the
parameters of the model. For phenomenologically allowed values of the
right--handed scale the tumbling symmetry breaking mechanism is realized in
which parity breaking at a high scale $\mu_R$ propagates down and eventually
causes the \EW symmetry breaking at the scale $\mu_{EW}\sim 100$ GeV. The model
exhibits a number of low and intermediate mass Higgs bosons with certain
relations between their masses. In particular, the $SU(2)_L$ Higgs doublet
$\chi_L$ is a pseudo--Goldstone boson of the accidental (approximate) $SU(4)$
symmetry of the Higgs potential and therefore is expected to be relatively
light.


title: Is Electroweak Baryogenesis Classical?

abstract:
  In this lecture first I present a brief genesis of the ideas on the
electroweak baryogenesis and then I focus on a mechanism in which the source of
$CP$ violation is a $CP$-violating field condensate which could occur, for
example, in multi-higgs extensions of the Standard Model. In the limit of a
thick bubble wall one finds a classical force acting on particles proportional
to the mass squared and the $CP$ violating phase. One can study this force in
the fluid approximation in which the effects of transport and particle decays
can be taken into account. A novelty in this talk is generalization of the
problem to the relativistic velocity. There is a regime in which the final
formula for the baryon asymmetry has a rather simple form.


abstract:
  We determine $|V_{cb}|$ from inclusive semileptonic B decays including
resummation of supposedly large perturbative corrections, which originate from
the running of the strong coupling. We argue that the low value of the BLM
scale found previously for inclusive decays is a manifestation of the
renormalon divergence of the perturbative series starting already in third
order. A reliable determination of $|V_{cb}|$ from inclusive decays is still
possible if one uses a short-distance b quark mass. We find that using the
$\overline{\rm MS}$ running mass significantly reduces the perturbative
coefficients already in low orders. For a semileptonic branching ratio of
$10.9\%$ we obtain $|V_{cb}|(\tau_B/1.50\,{\rm ps})^{1/2}=0.041\pm 0.002\pm
0.002$. This work was done in collaboration with M. Beneke and V.M.\ Braun.


title: Heavy Quark Production in Parton Model and in QCD

abstract:
  The cross sections of heavy quark production in $pp$ collision and for their
photo- and electroproduction are calculated in the framework of QCD. The
virtual nature of the interacting gluons as well as their transverse motion and
different polarizations are taken into account. The obtained cross sections
exhibit more rapid growth with the initial energy than the parton model
predictions and the $p_T$ distributions of produced heavy quarks are more
smooth.


title: Supersymmetry in the Very Early Universe

abstract:
  Supersymmetric flat directions can have a number of important consequences in
the very early universe. Depending on the form of the SUSY breaking potential
arising from the finite energy density at early times, coherent production of
scalar condensates can result along such directions. This leads a cosmological
disaster for Polonyi type flat directions with only Planck suppressed
couplings, but can give rise to the baryon asymmetry for standard model flat
directions. Flat directions are also natural candidates to act as inflatons.
Achieving density fluctuations of the correct magnitude generally requires an
additional hidden SUSY breaking sector.


title: Nonfactorizable Corrections to Hadronic Weak Decays of Heavy Mesons

abstract:
  Status of nonfactorizable effects in exclusive hadronic weak decays of $D$
and $B$ mesons is reviewed.


title: Chiral symmetry breaking in strongly coupled scalar QED

abstract:
  Scalar QED with fermions is investigated in an expansion in powers of the
inverse gauge coupling constant. The fermion mass generation is studied in next
to leading order of the strong coupling expansion for the Higgs-phase of the
model. Chiral symmetry breaking is discussed. Our approach supports from a
strong coupling point of view the results obtained earlier by Miransky, Bardeen
and Kondo.


title: The large-$N_c$ limit and the behavior of $g_A^{(0)}$ and $g_A$

abstract:
  We investigate the isoscalar and isovector components of the axial vector
coupling constants, $g_A^{(0)}$ and $g_A$, using algebraic models that lead to
the correct symmetries of large-$N_c$ QCD. Results obtained previously in
various chiral models are interpreted from this algebraic point of view. The
results of the Skyrme model and the valence quark model are explained by simple
realizations of the algebra.


title:
Symmetry analysis of the hadronic tensor for the semi-inclusive
  pseudoscalar meson leptoproduction from an unpolarized nucleon target

abstract:
  By examining the symmetry constraints on the semi-inclusive pseudoscalar
particle production in unpolarized inelastic lepton-hadron scattering, we
present a complete, exact Lorentz decomposition for the corresponding hadronic
tensor. As a result, we find that it contains five independent terms, instead
of the four as have been suggested before. The newly identified one is odd
under the naive time reversal transformation, and the corresponding structure
function is directly related to the single spin asymmetry in the semi-inclusive
pseudoscalar meson production by a polarized lepton beam off an unpolarized
target.


title:
Update of the stranger story: The strange vector form factors of the
  nucleon in the SU(3) chiral quark-soliton model

abstract:
  The strange vector form factors are evaluated for $Q^2=0$ and $Q^2=1\
\mbox{GeV}^2$ in the framework of the SU(3) chiral quark-soliton model (or
semi-bosonized SU(3) Nambu-Jona-Lasinio model). The rotational $1/N_c$ and
$m_s$ corrections are taken into account up to linear order. The mean-square
strange radius $\langle r^{2}\rangle^{Sachs}_{s}=-0.35\; \mbox{fm}^2$ and the
strange magnetic moment $\mu_s = -0.44\;\mu_N$ are obtained. The results are
compared with several different models.


title: Baryon Number Violating Transitions in String Backgrounds

abstract:
  We construct field configurations that interpolate between string background
states of differing baryon number. Using these configurations we estimate the
effect of the background fields on the energy barrier separating different
vacua. In the background of a superconducting GUT string the energy barrier is
increased, while in an electroweak string background or the electroweak layer
of a non-superconducting string the energy barrier is reduced. The energy
barrier depends sensitively on both the background gauge and scalar fields.


title: Bound state solutions of scalar QED_{2+1} for zero photon mass

abstract:
  The Feynman-Schwinger representation is used to study the behavior of
solutions of scalar QED in (2+1) dimensions. The limit of zero photon mass is
seen to be smooth. The Bethe-Salpeter equation in the ladder approximation also
exhibits this property. They clearly deviate from the behavior in the
nonrelativistic limit. In a variational analysis we show that this difference
can be attributed to retardation effects of relativistic origin.


title:
Double spin asymmetry in diffractive $Q \bar Q$ production at SMC
  energies and quark-pomeron vertex structure

abstract:
  It is shown that the longitudinal double spin asymmetry $A_{ll}$ in polarized
diffractive $l p \to l p+Q \bar Q$ reaction depends strongly on the spin
structure of quark-pomeron vertex. The SMC spin facilities may be one of the
best place to perform such experiment.


title: Quarks and Gluons at Small $x$ and Scaling Violation of $F_2$

abstract:
  I present some comments on the relationship between the small-$x$ behaviour
of the parton (quark and gluon) densities and the scaling violation of the
proton structure function $F_{2}(x,Q^{2})$.


title:
Gluon structure function for deeply inelastic scattering with nucleus in
  QCD

abstract:
  In this talk we present the first calculation of the gluon structure function
for nucleus in QCD. We discuss the Glauber formula for the gluon structure
function and the violation of this simple approach that we anticipate in QCD.
(Talk given by E. Levin at QCD and nuclear target session at the Workshop on
Deep Inelastic Scattering and QCD, Paris, April 1995).


title:
Accelerator and Reactor Neutrino Oscillation Experiments in a Simple
  Three-Generation Framework

abstract:
  We present a new approach to the analysis of neutrino oscillation
experiments, in the one mass-scale limit of the three-generation scheme. In
this framework we reanalyze and recombine the most constraining accelerator and
reactor data, in order to draw precise bounds in the new parameter space. We
consider our graphical representations as particularly suited to show the
interplay among the different oscillation channels. Within the same framework,
the discovery potential of future short and long baseline experiments is also
investigated, in the light of both the recent signal from the LSND experiment
and the atmospheric neutrino anomaly.


title:
Single Top Quark Production as a Probe for Anomalous Moments at Hadron
  Colliders

abstract:
  Single production of top quarks at hadron colliders via $gW$ fusion is
examined as a probe of possible anomalous chromomagnetic and/or chromoelectric
moment type couplings between the top and gluons. We find that this channel is
far less sensitive to the existence of anomalous couplings of this kind than is
the usual production of top pairs by $gg$ or $q\bar q$ fusion. This result is
found to hold at both the Tevatron as well as the LHC although somewhat greater
sensitivity for anomalous couplings in this channel is found at the higher
energy machine.


title: The LSND Experiment and the Zee Model

abstract:
  A recent experiment LSND at Los Alamos has provided\cite{1} an indication of
$\overline{\nu}_{\mu} - \overline{\nu}_e$ oscillations with $\Delta m^2$ of
order 1ev$^2$ or greater and $\sin^2 2 \theta_{e \mu}$ between $2 \times
10^{-3}$ and $10^{2}$. Such a value of $\Delta m^2$ for $\nu_{\mu} - \nu_e$
oscillations was not expected in the standard see-saw model\cite{2} suggested
by SO(10) with a large mass hierarchy because it leads to too large a value of
$m(\nu_{\tau})$ to fit cosmological constraints. Furthermore within that model
the LSND result is inconsistent with the indications of oscillations from both
atmospheric neutrinos\cite{3} and solar neutrinos.\cite{4}


title: Top Quark Candidates and Light Gluinos

abstract:
  We discuss the case for a light gluino and the mutual impact of this
possibility with the Fermilab top quark candidates


title:
New vector-scalar contributions to neutrinoless double beta decay and
  constraints on R-parity violation

abstract:
  We show that in minimal supersymmetric standard model (MSSM) with R-parity
breaking as well as in the left-right symmetric model, there are new observable
contributions to neutrinoless double beta decay arising from hitherto
overlooked diagrams involving the exchange of one W boson and one scalar boson.
In particular, in the case of MSSM, the present experimental bounds on
neutrinoless double beta decay lifetime improves the limits on certain R-parity
violating couplings by about two orders of magnitude. It is shown that similar
diagrams also lead to enhanced rates for $\mu^-\rightarrow e^+$ conversion in
nuclei, which are in the range accessible to ongoing experiments.


title: Theory of Hard Diffraction and Rapidity Gaps

abstract:
  In this talk we review the models describing the hard diffractive production
of jets or more generally high-mass states in presence of rapidity gaps in
hadron-hadron and lepton-hadron collisions. By rapidity gaps we mean regions on
the lego plot in (pseudo)-rapidity and azimuthal angle where no hadrons are
produced, between the jet(s) and an elastically scattered hadron (single hard
diffraction) or between two jets (double hard diffraction).


title: Chiral Perturbation Theory for Vector Mesons

abstract:
  The interactions of $\rho$, $K^*$, $\phi$ and $\omega$ vector-mesons with
low-momentum $\pi$, $K$ and $\eta$ pseudoscalar mesons are constrained by
chiral symmetry. We derive a heavy vector-meson chiral Lagrangian in which the
vector mesons are treated as heavy static matter fields. The unknown couplings
of the chiral Lagrangian are further related using the $1/N_c$ expansion.
Chiral perturbation theory is applied to the vector-meson mass matrix. At
one-loop there are large corrections to the individual vector meson masses, but
the singlet-octet mixing angle remains almost unchanged. The parity-violating
$s$-wave $\phiC \rightarrow \rho \pi$ weak decay amplitude is derived in the
combined chiral and large $N_c$ limits. Rare $\phi$ decays provide a sensitive
test of non-leptonic neutral current structure.


title:
Comment on Quarks and Gluons at Small $x$ and the Sdis Factorization
  Scheme

abstract:
  I present some comments on the partonic interpretation of the HERA data on
the proton structure function. The effects of the resummation of the leading
and next-to-leading $\ln x$-contributions are discussed. A new factorization
scheme, in which these resummation effects are absorbed into a steep
redefinition of the gluon density, is introduced and its (possible)
interpretation and phenomenological relevance are suggested.


title:
Analytic Properties of the QCD Running Coupling Constant and $\tau$
  Decay

abstract:
  A non-perturbative expansion method which gives a well-defined analytic
continuation of the running coupling constant from the spacelike to the
timelike region is applied to the inclusive semileptonic decay of the
$\tau$--lepton. The method allows us to evaluate $R_{\tau}$ by integration over
the non-perturbative physical region, rather than by using Cauchy's theorem,
and hence to incorporate threshold effects in a very direct way. Within our
framework the difference between the effective coupling constants in the
timelike and spacelike domains can be substantial and is not simply a matter of
the standard $\pi^2$ terms.


title:
On the Cosmological Domain Wall Problem for the Minimally Extended
  Supersymmetric Standard Model

abstract:
  We study the cosmology of the Supersymmetric Standard Model augmented by a
gauge singlet to solve the $\mu$-problem and describe the evolution of the
domain walls which are created during electroweak symmetry breaking due to the
discrete $Z_{3}$ symmetry in this model. The usual assumption, that
non-renormalizable terms induced by gravity (which explicitly break this
symmetry) may cause the walls to collapse on a cosmologically safe timescale,
is reconsidered. Such terms are constrained by considerations of primordial
nucleosynthesis, and also by the fact that by not respecting the $Z_{3}$
symmetry they induce divergences which destabilise the hierarchy and
reintroduce the $\mu$--problem. We find that, even when the K\"ahler potential
is `non-minimal' (i.e. when the hidden sector couples directly to the visible)
the model is either ruled out cosmologically or suffers from a naturalness
problem.


title: Results on Hard Diffractive Production

abstract:
  The results of experiments at hadron colliders probing the structure of the
pomeron through hard diffraction are reviewed. Some results on deep inelastic
diffractive scattering obtained at HERA are also discussed and placed in
perspective. By using a properly normalized pomeron flux factor in single
diffraction dissociation, as dictated by unitarity, the pomeron emerges as a
combination of valence quark and gluon color singlets in a ratio suggested by
asymptopia.


title: MACHOs and molecular clouds in galactic halos

abstract:
  Recent observations of microlensing events in the Large Magellanic Cloud by
the MACHO and EROS collaborations suggest that an important fraction of the
galactic halo is in form of Massive Astrophysical Compact Halo Objects (MACHOs)
with mass ~ 0.1 M_{\odot}. We outline a scenario in which dark clusters of
MACHOs and molecular clouds form in the halo at galactocentric distances larger
than ~ 10-20 kpc, provide baryons are a major constituent of the halo. Possible
signatures of the presence of molecular clouds in our galaxy are discussed. We
also discuss how molecular clouds as well as MACHOs can be observed directly in
the nearby M31 galaxy.


title:
Astrophysical and cosmological considerations on a string dilaton of a
  least coupling

abstract:
  String-loop effects may generate very weak matter couplings for a (massless)
dilaton. We examine limits on the shift of such a dilaton toward its present
equilibrium value from big-bang nucleosynthesis and the binary pulsar. On the
other hand, the approach of the dilaton toward its present value can be
realized in the early universe in a quick and efficient way if an inflationary
period is present. We comment briefly on some implications.


title: Relaxation mechanisms: From Damour-Polyakov to Peccei-Quinn

abstract:
  The ralaxation mechanism of Damour-Polyakov for fixing the vacuum expectation
value of certain scalar fields (moduli) in string theory could provide a
convenient framework for the Peccei-Quinn relaxation mechanism and remove the
narrow "axion window".


title: Present and Future Aspects of CP Violation

abstract:
  This series of five lectures describes aspects of CP violation, emphasizing
its description within the standard electroweak model. After discussing the
kaon system, the only place in which CP violation has been seen so far, we turn
to the leading contender for the effect, complex phases in the
Cabibbo-Kobayashi-Maskawa (CKM) matrix. A number of suggestions are made for
improved tests of the standard picture. Hadrons containing $b$ quarks play a
key role in this program, and are discussed separately. We also mention a
number of non-standard and speculative aspects of CP violation, including
alternatives to the CKM description, direct tests of time reversal invariance,
and baryogenesis.


title: Dual Ginzburg-Landau Theory and Chiral Symmetry Breaking

abstract:
  We study the properties of quarks, being confined in hadrons, with the
Schwinger-Dyson equation in the dual Ginzburg-Landau Theory. Magnetic monopole
condensation, which provides quark confinement, is demonstrated responsible
also for dynamical chiral-symmetry breaking. We discuss then the recovery of
the chiral symmetry at finite temperature.


title: Dual Ginzburg-Landau Theory for Nonperturbative QCD

abstract:
  Nonperturbative QCD is studied with the dual Ginzburg-Landau theory, where
color confinement is realized through the dual Higgs mechanism by QCD-monopole
condensation. We obtain a general analytic formula for the string tension. A
compact formula is derived for the screened inter-quark potential in the
presence of light dynamical quarks. The QCD phase transition at finite
temperature is studied using the effective potential formalism. The string
tension and the QCD-monopole mass are largely reduced near the critical
temperature, $T_c$. The surface tension is estimated from the effective
potential at $T_c$. We propose also a new scenario of the quark-gluon-plasma
creation through the color-electric flux-tube annihilation. Finally, we discuss
a close relation between instantons and QCD-monopoles.


title: Parton Gas Model for the Nucleon Structure Functions

abstract:
  A phenomenological model for the nucleon structure functions is presented.
Visualising the nucleon as a cavity filled with parton gas in thermal
equilibrium and parametrizing the effects due to the finiteness of the nucleon
volume, we obtain a good fit to the data on the unpolarized nucleon structure
functions.


title: Nuclear modification in the structure function $F_3$

abstract:
  Nuclear shadowing in the structure function $F_3$ is investigated as a
possible test of shadowing models. The $F_3$ shadowing is studied in two
different theoretical models: a parton-recombination model with $Q^2$ rescaling
and an aligned-jet model. We find that predictions in these models differ
completely in the small $x$ region. It suggests that the $F_3$ shadowing could
be used for discriminating among different models, which produce similar
shadowing behavior in the structure function $F_2$.


title: A Review of Minimal Supersymmetric Electro-Weak Theory

abstract:
  In this review article we study the Minimal Supersymmetric Electro-Weak
theory (of leptons). The Lagrangian is constructed step by step in great
detail, both in the superfield and component field formalism --- both on and
off shell. Furthermore the Lagrangian is written in the more familiar four
component formalism. Electro weak symmetry breaking is discussed, and the
physical chargino- and neutralino states are introduced and discussed.


title:
Optimized perturbation theory for bound states: toy model and realistic
  problem

abstract:
  Within quantum mechanics model we study the problem of resummation of an
asymptotic perturbation series for bound state parameters via optimization of
the perturbative expansion. A possible application of the method to the
positronium lifetime calculation is also briefly considered.


title: Ferromagnetic Detectors of Axions in RF (S - X) Band

abstract:
  The (pseudo) Goldstone bosons arise naturally in many modern theories such as
supergravity, superstring theory and variants of general relativity with
torsion. By the other hand, there are well known indications that a large part
of the Universe mass exists in a form of dark matter. The most attractive model
of the dark matter is non-relativistic gas of the light elementary particles
weakly interacting with the "usual" matter \cite{b2} - \cite{b4}. We describe
ferromagnetic detectors, for search of arion(axion), where a high-sensitive
two-channel SHF receiver is used. Its sensitivity reaches to $10^{-20}\,Wt$,
with time of accumulation $1-10\,s$. Fourier analysis of signal provides a
survey in zone up to $\pm50\,KHz$ with spectral resolution $0.1 - 25\, Hz$.
There was applied a high sensitive SHF receiver based on a special computer
method of coherent accumulation of signals. It is possible to use the receiver
in other precise experiments: measuring of electron/positron beams polarization
in storage rings, investigation of parity violation, investigation of
atmosphere with radars etc.


title: Elusive exotic states

abstract:
  The existence of flavor exotic $QQ\bar{q}\bar{q}$ molecular-type states is
investigated. An attractive force between two {\it pseudoscalar} $H =
(Q\bar{q})$ heavy meson is generated by (correlated) two-pion exchange. The
emergence of a (loosely) bound state depends crucially on the value of the
coupling constant $g$ of the $H^*H\pi$ vertex. For a $g$ value calculated from
the experimental upper limit on the width of the $D^*$ meson the considered
mechanism alone is strong enough to generate a bound state in the $BB$ system
while the $DD$ system is very close to become bound. Such states, if exist, are
stable with respect to strong interactions. They may be observed as stable
scalar particles with the mass $M\approx 2\,m_H$ and flavor quantum number $\pm
2$.


title: Theory of Vector Meson Production

abstract:
  I discuss the theoretical status of the `soft' pomeron and its place in
describing generic diffractive processes. The role of perturbative QCD (pQCD)
corrections is considered, in particular in the context of quasi-elastic vector
meson production at high $Q^2$. In those processes where short distances are
dominant, the `hard' (pQCD) pomeron is expected to reveal itself, such a
process may well be that of diffractive vector meson production at high-$t$ and
I discuss this.


title: Photon Energy Spectrum in $B \to X_s \gamma$ and Comparison with Data

abstract:
  A comparison of the inclusive photon energy spectrum in the radiative decay
$\BGAMAXS$, measured recently by the CLEO collaboration, with the standard
model is presented, using a $B$-meson wave function model and improving earlier
perturbative QCD-based computations of the same. The dependence of the photon
energy spectrum on the non-perturbative model parameters, $p_F$, the $b$-quark
Fermi momentum in the $B$ hadron, and $m_q$, the spectator quark mass, is
explicitly shown, allowing a comparison of these parameters with the ones
obtained from the analysis of the lepton energy spectrum in semileptonic $B$
decays. Taking into account present uncertainties, we estimate $\BBGAMAXS =
(2.55 \pm 1.28) \times 10^{-4}$ in the standard model, assuming
$\absvts/\absvcb= 1.0$. Comparing this with the CLEO measurement $\BBGAMAXS =
(2.32 \pm 0.67) \times 10^{-4}$ implies $\absvts/\absvcb= 1.1 \pm 0.43$, in
agreement with the CKM unitarity.


title:
Dispersion-Theoretical Analysis of the Nucleon Electromagnetic
  Formfactors

abstract:
  Dispersion relations allow for a coherent description of the nucleon
electromagnetic form factors measured over a large range of momentum transfer,
$Q^2 \simeq 0 \ldots 35$ GeV$^2$. Including constraints from unitarity and
perturbative QCD, we present a novel parametrisation of the absorptive parts of
the various isoscalar and isovector nucleon form factors. Using the current
world data, we obtain results for the electromagnetic form factors, nucleon
radii and meson couplings. We stress the importance of measurements at large
momentum transfer to test the predictions of perturbative QCD.


title:
Searching a systematics for nonfactorizable contributions to hadronic
  decays of $ D^{0}$ and $ D^{+}$ mesons

abstract:
  We investigate nonfactorizable contributions to charm meson decays in $ D
\rightarrow \bar K \pi $/ $ \bar K \rho$ /$ \bar K ^{*} \pi$ / $ \bar K a_{1}$
/ $ \bar K ^{*} \rho $ modes. Obtaining the contributions from spectator-quark
diagrams for $ N_{c}$ = 3, we determine nonfactorizable isospin 1/2 and 3/2
amplitudes required to explain the data for these modes. We observe that ratio
of these amplitudes seem to follow a universal value.


title: The Hyperfine Spin Splittings In Heavy Quarkonia

abstract:
  The hyperfine spin splittings in heavy quarkonia are studied using the
recently developed renormalization group improved spin-spin potential which is
independent of the scale parameter $\mu$. The calculated energy difference
between the $J/\psi$ and the $\eta_c$ fits the experimental data well, while
the predicted energy difference $\Delta M_p$ between the center of the gravity
of $1^3P_{0,1,2}$ states and the $1^1P_1$ state of charmonium has the correct
sign but is somewhat larger than the experimental data. This is not surprising
since there are several other contributions to $\Delta M_p$, which we discuss,
that are of comparable size ($\sim 1$ MeV) that should be included, before
precise agreement with the data can be expected. The mass differences of the
$\psi'-\eta_c'$, $\Upsilon(1S)-\eta_b$, $\Upsilon(2S)-\eta_b'$, and $B_c^*-B_c$
are also predicted.


title: Color-Octet $\psi'$ Production at Low $p_\perp$

abstract:
  We study contributions from color-octet quarkonium formation mechanisms to
$p_\perp$-integrated $\psi'$ production cross sections in pion-nucleon
reactions. The observed polarization of the $\psi'$ is not reproduced by the
lowest-order leading-twist color-singlet and color-octet mechanisms. This
suggests that there are important quarkonium production mechanisms beyond
leading twist.


title: Composite Neutrinos and Double Beta Decay

abstract:
  Neutrinoless double beta decay $(\b\b)_{0\nu}$ occurs through the magnetic
coupling of dimension five, $\lambda_W^{(\nu*)}/m_{\nu*}$, among the excited
electron neutrino $\nu^*$, electron and $W$ boson if $\nu^*$ is a massive
Majorana neutrino. If the coupling is not small, i.e., $\lambda_W^{(\nu*)}>1$
the mass of the excited neutrino must not be gless than the $Z$ boson mass,
$m_Z$. Since $\nu^*$ contributes in the $(\b\b)_{0\nu}$ decay as a vertual
state, this decay will give an oppotunity to explore the much heavier mass
region of $\nu^*$.
  In this paper, we present the decay formula of $(\b\b)_{0\nu}$ decay through
the $\nu^*$ exchange and discuss the constraint on the coupling constant and
the mass of the excited neutrino. By comparing the recent data for ${}^{76}$Ge,
we find $\lambda_W^{(\nu*)}({1\rm TeV}/m_{\nu*})) (m_N/{1\rm TeV})^{\frac 12}<
4.1\cdot 10^{-3}$ where $m_N$ is the Majorana mass of the excited electron
neutrino. If $m_N=m_{\nu*}$ and $\lambda_W^{(\nu*)}>1$, we find the mass bound
for the excited Majorana neutrino as $m_{\nu^*} > 5.9\cdot 10^4$TeV.
  In order to obtain the constraint on the composite scale $\Lambda$, we have
to specify the model. For the mirror type and the homodoublet type models,
$\lambda_W^{(\nu*)}/m_{\nu*}=f/(\sqrt 2 \Lambda)$ where $f$ is the relative
strength of gauge couplings. Then, we obtain $\Lambda > 170 f (m_N/{1\rm
TeV})^{\frac 12}$TeV. For the sequential type model,
$\lambda/m_{\nu*}=fv/(\sqrt 2 \Lambda^2)$ where $v$ is the vacuum expectation
value of the dopublet Higgs boson, i.e., $v=$250GeV. In this model, we find
$\Lambda > 6.6 f^{\frac 12} (m_N/{1\rm TeV})^{\frac 14}$TeV.


title: Supersymmetric Dark Matter

abstract:
  There is almost universal agreement among astronomers that most of the mass
in the Universe and most of the mass in the Galactic halo is dark. Many lines
of reasoning suggest that the dark matter consists of some new, as yet
undiscovered, weakly-interacting massive particle (WIMP). There is now a vast
experimental effort being surmounted to detect WIMPS in the halo. The most
promising techniques involve direct detection in low-background laboratory
detectors and indirect detection through observation of energetic neutrinos
from annihilation of WIMPs that have accumulated in the Sun and/or the Earth.
Of the many WIMP candidates, perhaps the best motivated and certainly the most
theoretically developed is the neutralino, the lightest superpartner in many
supersymmetric theories. We review the minimal supersymmetric extension of the
Standard Model and discuss prospects for detection of neutralino dark matter.
We review in detail how to calculate the cosmological abundance of the
neutralino and the event rates for both direct- and indirect-detection schemes,
and we discuss astrophysical and laboratory constraints on supersymmetric
models. We isolate and clarify the uncertainties from particle physics, nuclear
physics, and astrophysics that enter at each step in the calculation. We
briefly review other related dark-matter candidates and detection techniques.


title:
BFKL QCD Pomeron in High Energy Hadron Collisions: Inclusive Dijet
  Production

abstract:
  We calculate inclusive dijet production cross section in high energy hadron
collisions within the BFKL resummation formalism for the QCD Pomeron. Unlike
the previous calculations with the Pomeron developing only between tagging
jets, we include also the Pomerons which are adjacent to the hadrons. With
these adjacent Pomerons we define a new object --- the BFKL structure function
of hadron --- which enables one to calculate the inclusive dijet production for
any rapidity intervals. We present predictions for the K-factor and the
azimuthal angle decorrelation in the inclusive dijet production for
Fermilab-Tevatron and CERN-LHC energies.


title: Cross-Section Asymmetries Around the $Z$ Peak

abstract:
  A simple model-independent formula for cross-section asymmetries $A$ in
fermion-pair production is derived, which may be used for the analysis of LEP~1
data, $A = \sum_n A_n (s - M_Z^2)^n$. The coefficient $A_0$ depends on the $Z$
boson exchange, $A_1$ additionally on the $\gamma Z$ interference, while the
higher-order contributions are practically redundant. QED corrections are taken
into account, and relations to other approaches are indicated.


title: Proton Spin, Sum Rules, QCD and Higher Twist

abstract:
  We examine the present status of the Bjorken sum rule in the light of recent
data on the spin structure functions of the proton, neutron and deuteron
obtained by the CERN and SLAC experimental groups. We also discuss the role of
possible higher-twist contributions and higher-order PQCD corrections and
comment on the extraction of the necessary parameters, D and F, obtained from
hyperon semi-leptonic decays.


title:
Study of the Strongly Interacting Higgs Physics Model with Heavy
  Fermions

abstract:
  We study the effect of a possible fourth heavy generation of fermions on the
Higgs sector of the standard model. We show, from the violation of elastic
unitarity, that the scale of strong interactions is well below 1 TeV even with
a Higgs mass as low as 500 GeV provided the fourth generation fermion mass is
equal or larger than the Higgs mass. The diagonal Pade approximant method is
then used to unitarize the partial wave amplitudes. It is found that, for the
fourth generation fermion masses which are comparable to or larger than the
Higgs mass, the Landau ghosts in the I=0 and I=2 channels of the reconstructed
amplitudes move too close to the physical region to be accepted.


title: Cerenkov radiation by neutrinos in a supernova core

abstract:
  Neutrinos with a magnetic dipole moment propagating in a medium with a
velocity larger than the phase velocity of light emit photons by the Cerenkov
process. The Cerenkov radiation is a helicity flip process via which a
left-handed neutrino in a supernova core may change into a sterile right-handed
one and free-stream out of the core. Assuming that the luminosity of such
sterile right-handed neutrinos is less than $10^{53}$ ergs/sec gives an upper
bound on the neutrino magnetic dipole moment $\mu_\nu < 0.2 \times 10^{-13}
\mu_B$. This is two orders of magnitude more stringent than the previously
established bounds on $\mu_\nu$ from considerations of supernova cooling rate
by right-handed neutrinos.


title: Tunneling in quantum field theory with spontaneous symmetry breaking

abstract:
  Tunneling in quantum field theory is well understood in the case of a single
scalar field. However, in theories with spontaneous symmetry breaking, one has
to take into account the additional zero modes which appear due to the
Goldstone phenomenon. We calculate the false vacuum decay rate in this case.
The result may differ significantly from the tunneling rates in the absence of
symmetry breaking.


title: Thermal effects on dilepton production from $\pi-\pi$ annihilation

abstract:
  We study finite temperature effects on dilepton production from pion-pion
annihilation in hot hadronic matter. The softening of the pion dispersion
relation in a medium is found to enhance the production rate of dileptons with
invariant masses in the region of $2m^*_\pi(T)<M<m_\rho$. On the other hand,
the reduction of the pion electromagnetic form factor at finite temperature
leads to a suppression of the dilepton production rate. Including both effects,
we have found that the dilepton yield is slightly enhanced in the invariant
mass region $M= 270\sim 600$ MeV but is suppressed around the vector meson
resonance. We further discuss the relevance of our results to recent
experimental data from the S+Au collisions at CERN/SPS energies by the CERES
collaboration.


title: Top Quark Mass Prediction in Superstring Derived Standard--like Models

abstract:
  A remarkable achievement of the realistic superstring standard--like models
is the successful prediction of the top quark mass, assuming the Minimal
Supersymmetric Standard Model spectrum below the string scale. Recently it was
shown that string scale unification requires the existence of additional
matter, in vector--like representations, at intermediate energy scales and that
certain string models contain the needed representations in their massless
spectrum. I obtain the top, bottom and tau lepton Yukawa couplings in these
models, by calculating tree level string amplitudes, in terms of the unified
gauge coupling and certain vacuum expectation values that are required for the
consistency of the string models. Using two--loop renormalization group
equations for the gauge and Yukawa couplings, I study the effect of the
intermediate matter thresholds on the top quark mass prediction. Agreement with
the experimental values of $\alpha_{\rm strong}(M_Z)$, $\sin^2\theta_W(M_Z)$
and $\alpha^{-1}_{\rm em}(M_Z)$ is imposed. It is found that the physical top
quark mass prediction is increased to the range $192-200$ GeV and that the
ratio $\lambda_b(M_Z)/\lambda_\tau(M_Z)$ is in agreement with experiment.


title:
Nucleon to Delta Weak Excitation Amplitudes in the Non-relativistic
  Quark Model

abstract:
  We investigate the nucleon to Delta(1232) vector and axial vector amplitudes
in the non-relativistic quark model of the Isgur-Karl variety. A particular
interest is to investigate the SU(6) symmetry breaking, due to color hyperfine
interaction. We compare the theoretical estimates to recent experimental
investigation of the Adler amplitudes by neutrino scattering.


title:
Two-component colour dipole emission in the central region of
  onium-onium scattering

abstract:
  The initial-state radiation of soft colour dipoles produced in the central
region of onium-onium scattering via single QCD Pomeron exchange (BFKL) is
calculated in the framework of Mueller's dipole approach. The resulting dipole
production has a two-component structure. One is constant with energy while the
other grows and possesses a power-law tail at appreciably large transverse
distances from the collision axis. It may be related to the growth of the gluon
distribution at small Bjorken-$x.$


title: Anomalous four-fermion processes in electron-positron collisions

abstract:
  This paper studies the electroweak production of all possible four-fermion
states in $e^+e^-$ collisions with non-standard triple gauge boson couplings.
All $CP$ conserving couplings are considered. It is an extension of the methods
and strategy, which were recently used for the Standard Model electroweak
production of four-fermion final states. Since the fermions are taken to be
massless the matrix elements can be evaluated efficiently, but certain phase
space cuts have to be imposed to avoid singularities. Experimental cuts are of
a similar nature. With the help of the constructed event generator a number of
illustrative results is obtained for $W$-pair production. These show on one
hand the distortions of the Standard Model angular distributions caused by
either off-shell effects or initial state radiation. On the other hand, also
the modifications of distributions due to anomalous couplings are presented,
considering either signal diagrams or all diagrams.


title: QCD--Instanton Induced Final States in Deep Inelastic Scattering

abstract:
  We report briefly on a broad and systematic study of possible manifestations
of QCD-instantons at HERA. We concentrate on the high multiplicity final state
structure, reminiscent of an isotropically decaying ``fireball''. First results
of a Monte Carlo simulation are presented, with emphasis on the typical
event-structure and the transverse energy, muon and $K^0$ flows.


title: Gauge Coupling Unification in GUT and String Models

abstract:
  The results for the running of the gauge couplings in the MSSM are up-dated
by proper inclusion of all low scale effects. They are presented as predictions
for the strong coupling constant in the scenario with only two parameters at
the GUT scale ~ ($\alpha_{U}$ ~and ~$M_{U}$) ~and as a mismatch of the
couplings at the scales ~$\sim 3 \times 10^{16}$ GeV ~and ~$4\times10^{17}$
GeV, when all three couplings are taken as the experimental input.


title: Cabibbo favored hadronic decays of charmed baryons in flavor SU(3)

abstract:
  The two body Cabibbo favored hadronic decays of charmed baryons
$\Lambda^{+}_{c}$, $\Xi^{+}_{c}$ and $\Xi_{c}^{0}$ into an octet or decuplet
baryon and a pseudoscalar meson are examined in the SU(3) symmetry scheme. The
numerical estimates for decay widths and branching ratios of some of the modes
are obtained and are in good agreement with experiment.


title: Experimental tests of CPT symmetry and quantum mechanics at CPLEAR

abstract:
  We review a phenomenological parametrization of an open quantum-mechanical
formalism for CPT violation in the neutral kaon system, and constrain the
parameters using fits to recent CPLEAR data.


title: New Physics with three-photon events at LEP

abstract:
  The effect of the most general \z3gt vertex in the reaction $e^+e^- \ra
3\gamma$ is studied with a particular attention to LEP searches. We give exact
analytical expressions including realistic cuts for the signal and present a
detailed analysis based on a Monte Carlo that includes the effect of the
irreducible $3\gamma$ QED cross section. As special applications we discuss the
effect of heavy scalars, fermions and gauge bosons and comment on the
``monopole" connection.


title: Spin and Flavor Contents of the Proton

abstract:
  After a brief review of the experimental results obtained in deep inelastic
lepton-nucleon scatterings and the Drell-Yan processes and their implications
for the spin and flavor contents of the nucleon, we suggest that those
features, that are contrary to the expectations of the naive quark model, can
all be accounted for in the chiral quark model of Georgi and Manohar. In our
formulation of the chiral quark model, the $\eta ^{\prime }$ meson is seen to
play an important role.


title:
Lattice Study of the Decay B^0-bar -> rho^+ l^- nu_l-bar:
  Model-Independent Determination of |V_{ub}|

abstract:
  We present results of a lattice computation of the vector and axial-vector
current matrix elements relevant for the semileptonic decay B^0-bar -> rho^+
l^- nu_l-bar. The computations are performed in the quenched approximation of
lattice QCD on a 24^3 x 48 lattice at beta = 6.2, using an O(a) improved
fermionic action. Our principal result is for the differential decay rate,
dGamma/dq^2, for the decay B^0-bar -> rho^+ l^- nu_l-bar in a region beyond the
charm threshold, allowing a model-independent extraction of |V_{ub}| from
experimental measurements. Heavy quark symmetry relations between radiative and
semileptonic decays of B-bar mesons into light vector mesons are also
discussed.


title: Reinterpretation of Thermal Dilepton Emission Rate by Spectral Functions

abstract:
  We reinterpret the dilepton emission rate from a hadronic gas expected to be
produced in heavy ion collisions in terms of the spectral functions available
from the $e^+e^-$ annihilation and the $\tau$ lepton decays experiments. We
take into account all possible hadronic state especially the multi-pion
contributions to the dilepton emission and the parity mixing phenomenon due to
the soft final-state corrections. A new compilation of the experimental data
for the spectral functions is presented.


title: The Top Story

abstract:
  This is an overview of top quark search, with particular emphasis on the more
recent results. After a brief introduction to the basic constituents of matter
and their interactions, I shall discuss the indirect evidences for the
existence of top quark and its mass from LEP and finally the direct observation
of a top quark signal recently reported from the Tevatron collider. I shall try
to put these results in perspective and provide some insight into the physics
issues involved in the top quark search.


title:
Is it Possible to Unify the QCD Evolution of Structure Functions in $X$
  and $Q^2$ ?

abstract:
  We start from the two existing QCD evolution equations for structure
functions, the BFKL and DGLAP equations, and discuss the theoretical hints for
a unifying picture of the evolution in $x$ and $Q^2.$ The main difficulty is
due to the property of angular ordering of the gluon radiation driving the
evolution and the cancellation of the related collinear singularities. At the
leading $\log\ 1/x$ and leading $\log \ Q^2$ accuracy, we find a unified set of
equations satisfying the constraints.


title:
The Soft Pomeron and Nonperturbative Corrections in Quark-Quark
  Scattering

abstract:
  We consider elastic quark-quark scattering at high energy with fixed momentum
transfer $t$ and perform factorization of soft-gluon exchanges into a vacuum
expectation value of Wilson lines. Taking into account nonperturbative
corrections whose structure is predicted from infrared renormalon analysis, we
represent the scattering amplitude as an asymptotic series. In the region of
small momentum transfer, where the nonperturbative corrections are dominant,
the scattering amplitude is Gaussian distribution in $t$ with a slope depending
on a nonperturbative scale. A nonperturbative origin of the soft pomeron is
thus identified.


title: On the $k_{\perp}$ dependent gluon density of the proton

abstract:
  The $k_{\perp}$ dependent gluon distribution is calculated accounting for the
resummation of small~$x$ effects due to the Lipatov equation. It is represented
by a convolution of a gluon density in the collinear limit and a universal
function ${\cal G}(x,k^2,\mu)$ for which an analytic expression is derived.


title:
Large $p_T$ Hadroproduction of $Z$ as a Probe of Gluon Distribution
  inside Proton

abstract:
  The transverse momentum distribution of single vector boson production at
hadron colliders provides useful ways of testing the Standard Model and
searching new physics beyond the Standard Model. We study large $p_{_T}$
hadroproduction of $Z$-boson as a probe of gluon distributions inside proton.
We investigate how to get initial gluon-involving contributions, or how to
subtract quark-quark (or -antiquark) contributions from total cross section. We
also investigated the simultaneous measurement of the rapidity and the
transverse momentum of the produced $Z$ boson, to obtain momentum fractions of
initial partons. And we extracted relevant uncertainties involving in
experimental and theoretical analyses. This large $p_{_T}$ hadroproduction of
$Z$ can be used as constraints on analyses of global parton (gluon and quarks)
distribution functions inside proton.


title: How to Search for Doubly Charmed Baryons and Tetraquarks

abstract:
  Possible experimental searches of doubly charmed baryons and tetraquarks at
fixed target experiments with high energy hadron beams and a high intensity
spectrometer are considered here. The baryons considered are: $\Xi_{cc}^{+}$
(ccd), $\Xi_{cc}^{++}$ (ccu), and $\Omega_{cc}^{+}$ (ccs); and the tetraquark
is T ($cc\bar{u}\bar{d}$). Estimates are given of masses, lifetimes, internal
structure, production cross sections, decay modes, branching ratios, and
yields. Experimental requirements are given for optimizing the signal and
minimizing the backgrounds. This paper is designed as an experimental and
theoretical review. It may therefore be of assistance in the planning for a
future state-of-the-art very charming experiment, in the spirit of the aims of
the recent CHARM2000 workshop.


title:
$\gamma\gamma\to\pi^0\pi^0$ and $\eta\to\pi^0\gamma\gamma$ at $O(p^6)$
  in the NJL model

abstract:
  We discuss the processes $\gamma\gamma\to\pi^0\pi^0$ and $\eta\to\pi^0
\gamma\gamma$ at $O(p^6)$ in the momentum expansion. The calculation involves
tree--level, one--loop and two--loop diagrams of a chiral effective lagrangian
which is obtained by a bosonization of the NJL model. The importance of
integrating out meson resonances (reduction) is pointed out. Our final results
for the total cross section of $\gamma\gamma\to\pi^0\pi^0$ are in good
agreement with the experimental data of the Crystal Ball Collaboration. For the
width of the $\eta\to\pi^0\gamma\gamma$ decay we obtain the value $0.11$ eV
which has to be compared with the experimental value of $(0.84 \pm 0.18)$ eV.
Alternatively, taking empirical parameters from a vector--meson--dominance
model the prediction for the decay width is $0.35$ eV. We present a prediction
for the differential decay probability as a function of
$m_{\gamma\gamma}^2/m_\eta^2$.


title: Bounds on Heavy Chiral Fermions

abstract:
  We derive the low-energy electroweak effective lagrangian for the case of
additional heavy, unmixed, sequential fermions. Present data still allow for
the presence of a new quark and/or lepton doublet with masses greater than
$M_Z/2$, provided that these multiplets are sufficiently degenerate. Deviations
of the effective lagrangian predictions from a full one-loop computation are
sizeable only for fermion masses close to the threshold $M_Z/2$. Some of the
constraints on new sequential fermions coming from accelerator results and
cosmological considerations are presented. We point out that the new fermions
can significantly affect the production and decay rate into $\gamma \gamma$ of
the intermediate Higgs at LHC.


title: Supersymmetry at Present and Future Colliders

abstract:
  The theoretical expectations for the supersymmetric particle spectrum is
reviewed and a brief overview on present constraints on supersymmetric models
from collider experiments is presented. Finally, we discuss the discovery
potential of future collider experiments.


title:
Parameter Bounds in the Supersymmetric Standard Model from Charge/Color
  Breaking Vacua

abstract:
  We calculate limits on the trilinear soft-breaking parameter, $A_{t}$, in the
Minimal Supersymmetric Standard model by requiring the absence of nonzero top
squark vacuum expectation values. Assuming a low $\tan\beta$, which implies a
large top Yukawa coupling, we also calculate one-loop corrections to the
effective potential. The resulting numerical calculations of the charge/color
breaking limits are presented as best-fit surfaces. We compare these results
with the analytical limit, $A_{t}^{2} < 3(m_{2}^{2}+m_{q}^{2}+m_{t}^{2})$, and
find that although this bound is a good estimate of the charge/color breaking
bounds for a simplified model of the top sector, stricter bounds are found by a
numerical minimization of the Minimal Supersymmetric Standard Model potential.


title: Reexamination of KKbar Threshold Phenomena with K+K- Atom Included

abstract:
  We develop a general framework to study KKbar threshold phenomena with
resonances f0, a0 and K+K- atom included. Based on this formalism we predict
that the production of the K+K- atom in p+d=3He+X and similar reactions exhi-
bits a drastic energy dependence due to the interplay with resonances f0 (980)
and a0 (980). We point out that a set of few parameters describes KKbar
threshold effects, f0 and a0 mesons, and K+K- atom. Our hope is that precision
experimental study aimed at determining these parameters may shed more light on
the nature of f0 and a0 resonances.


title: The Oblique Corrections from the Diagonal ETC Interaction

abstract:
  We study the effect of the diagonal extended technicolor(ETC) gauge boson on
the oblique correction parameters. It is shown that in the $T$ parameter is
unacceptably large when the $Zbb$ vertex correction and $S$ parameter are
consistent with the experiments in the ETC model.


title: CP-Violating Effect of QCD Vacuum in Quark Fragmentation

abstract:
  We demonstrate that the non-trivial CP-violating structure of QCD vacuum can
lead to an observable effect in $e^+e^-\to q\bar q\to 2$-jet annihilation. We
find that the sign of the jet handedness correlation can be opposite to that
predicted by factorization of $q~\bar q$ fragmentation and CP-conjugation of
the two jets. A simple model estimation of the handedness correlation magnitude
is given.


title: Gluon Condensate from Lattice QCD

abstract:
  After making some critical comments about the traditional method of
extracting the gluon condensate from lattice QCD data, I present an alternative
analysis. The result is more than a factor of five larger than the
phenomenological value. Two closely related subjects, the effects of the
infrared renormalons on the extraction and the Lepage and Mackenzie improvement
on a lattice perturbation series, are also discussed.


title:
Finite width effects in Higgs decays as a means of measuring massive
  particle widths

abstract:
  We calculate decays of a Standard Model Higgs boson to a virtual massive
particle and discuss how this depends on the massive particle total width. If
the partial width of Higgs to a virtual massive particle can be measured this
gives a measurement of that massive particle's width. We discuss how one would
go about measuring these partial widths of a Higgs experimentally, and how this
could lead to a measurement of the $W$ boson and $t$ quark width. For the
latter extreme dependence on the Higgs mass and the small $H\to tt^*$ branching
ratios mean that little can be learnt about the $t$ quark width. For the former
there is also large dependence on the Higgs mass; however this can be removed
by taking the ratio of $H\to WW^*$ decays to $H\to ZZ^*$ decays. This ratio
also has the advantage of being fairly insensitive to physics beyond the
Standard Model. Unfortunately, for Higgs masses of interest the $H\to ZZ^*$
branching ratio is small enough that we require many 1000's of tagged Higgs
decays before an accurate measurement of the $W$ width can be made. This is
likely to be hard experimentally.


title: Inflation and Inverse Symmetry Breaking

abstract:
  An inflation model with inverse symmetry breaking of two scalar fields is
proposed. Constraints on the parameters for a successful inflation are
obtained. In general the inequality $\lambda_1\ll g <\lambda_2$ should be
satisfied, where $\lambda_{1,2}$ and $g$ are the coupling constants for self
interaction and mutual interaction of two scalar fields respectively. An
example with $SU(5)$ GUTs phase transition and numerical study are presented.
This model introduce a new mechanism for the onset of inflation.


title: Large $R$-parity Violating Couplings and Grand Unification

abstract:
  We consider a possibility that $R$-parity violating interactions of particles
which do not involve the first generation have large (up to 1) coupling
constants, $\Lambda$. Such couplings, if exist, could have a number of
phenomenological consequences: renormalization of $b-\tau$ mass ratio,
generation of $\nu_\tau$ mass in MeV region, {\em etc.}. In Grand Unified
models, where $B$- and $L$-violating couplings appear simultaneously, the
proton decay can be forbidden in virtue of hierarchical flavor structure of
$\Lambda.$ However, due to Cabibbo-Kobayashi-Maskawa mixing this decay is
induced already in one-loop. Present experimental data give the upper bound
$\Lambda \ltap 10^{-8}$ (or $|\lambda' \lambda''| \ltap 7\cdot 10^{-16},$ on
products of certain $L$- and $B$-violating coupling constants, in more general
context). The bound can be avoided, if there is an asymmetry between the $L$-
and $B$-violating couplings of usual matter fields. In the $SU(5)$ model the
asymmetry can be related to the doublet-triplet splitting.


title: Gauge Invariance and Unstable Particles

abstract:
  A gauge-independent approach to resonant transition amplitudes with
nonconserved external currents is presented, which is implemented by the pinch
technique. The analytic expressions derived with this method are $U(1)_{em}$
invariant, independent of the choice of the gauge-fixing parameter, and satisfy
a number of required theoretical properties, including unitarity. Although
special attention is paid to resonant scatterings involving the $\gamma WW$ and
$ZWW$ vertices in the minimal Standard Model, our approach can be extended to
the top quark or other unstable particles appearing in renormalizable models of
new physics.


title: The Electroweak Phase Transition

abstract:
  The electroweak phase transition is investigated by means of the
perturbatively calculated high temperature effective potential. An analytic
result to order $g^4,\lambda^2$ is presented for the Abelian Higgs model, the
SU(2)-Higgs model and the standard model and a complete on-shell
renormalization at zero temperature is performed. Higher order corrections are
found to increase the strength of the first order phase transition in the
non-Abelian model, opposite to the Abelian case. This effect is traced back to
the infrared contributions from the typical non-Abelian diagrams. The
dependence of several phase transition parameters on the Higgs mass is analysed
in detail. A new, gauge invariant, approach based on the composite field
$\Phi^\dagger\Phi$ is introduced. This method, which supports the above Landau
gauge results numerically, permits a conceptually simpler treatment of the
thermodynamics of the phase transition. In particular, it enables a
straightforward comparison with lattice data and the application of the
Clausius-Clapeyron equation to the electroweak phase transition.


title:
A Stochastic Approach to Thermal Fluctuations during a First Order
  Electroweak Phase Transition

abstract:
  We investigate the role played by subcritical bubbles at the onset of the
electroweak phase transition. Treating the configuration modelling the thermal
fluctuations around the homogeneous zero configuration of the Higgs field as a
stochastic variable, we describe its dynamics by a phenomenological Langevin
equation. This approach allows to properly take into account both the effects
of the thermal bath on the system: a systematic dyssipative force, which tends
to erase out any initial subcritical configuration, and a random stochastic
force responsible for the fluctuations. We show that the contribution to the
variance $\lgh\phi^2(t)\rg_V$ in a given volume $V$ from any initial
subcritical configuration is quickly damped away and that, in the limit of long
times, $\lgh\phi^2(t)\rg_V$ approaches its equilibrium value provided by the
stochastic force and independent from the viscosity coefficient, as predicted
by the fluctuation-dissipation theorem. In agreement with some recent claims,
we conclude that thermal fluctuations do not affect the nucleation of critical
bubbles at the onset of the electroweak phase transition making electroweak
baryogenesis scenarios still a viable possibility to explain the primordial
baryon asymmetry in the Universe.


title: Extracting the Strange Density from $xF_3$

abstract:
  We present a QCD analysis of the strange and charm contributions to the
neutrino deep inelastic structure function $xF_3$. We show that next-to-leading
order effects, which are relatively important for $F_2$, play a lesser role in
the case of $xF_3$. The neutrino--antineutrino difference $xF_3^{\nu} -
xF_3^{\bar \nu}$ provides a new determination of the strange density, which
exhibits some advantages with respect to other traditional methods.


title: Jets in QCD

abstract:
  Many analyses at the collider utilize the hadronic jets that are the
footprints of QCD partons. These are used both to study the QCD processes
themselves and increasingly as tools to study other physics, for example top
mass reconstruction. However, jets are not fundamental degrees of freedom in
the theory, so we need an {\em operational jet definition} and {\em reliable
methods to calculate their properties}. This talk covers both of these
important areas of jet physics.


title:
Magnetic Moments of the SU(3) Octet Baryons in the semibosonized SU(3)
  Nambu-Jona-Lasinio Model

abstract:
  We investigate the magnetic moments of the SU(3) octet baryons in the
framework of the $SU(3)$ semibosonized Nambu--Jona--Lasinio model. The
rotational $1/N_c$ corrections and strange quark mass in linear order are taken
into account. We derive general relations between magnetic moments of the SU(3)
octet baryons, based on the symmetry of our model. These relations indicate
that higher order corrections such as $O(m_s/N_c)$ and $O(m^{2}_{s})$ are
relatively small. The magnetic moments of the octet baryons predicted by our
model are quantitatively in a good agreement with experimental results within
about 15$\%$.


title: The $\alpha_S$ Dependence of Parton Distributions

abstract:
  We perform next-to-leading order global analyses of deep inelastic and
related data for different fixed values of $\alpha_S (M_Z^2)$. We present sets
of parton distributions for six values of $\alpha_S$ in the range 0.105 to
0.130. We display the $(x, Q^2)$ domains with the largest parton uncertainty
and we discuss how forthcoming data may be able to improve the determination of
the parton densities.


title: S-matrix interpretation of finite-temperature real-time field theories

abstract:
  The aim of the article is to construct the S-matrix interpretation of the
perturbation theory for the Wigner functions generating functional at a finite
temperature. The temperature is introduced in the theory by the way typical for
the microcanonical description. The perturbation theory contains the
two-temperature Green functions. The two possible boundary conditions are
considered. One of them is usual in a field theory vacuum boundary condition.
The corresponding generating functional can be used in the particle physics.
Another type of the boundary condition assumes that the system under
consideration is in environment of the free particles background field. This
leads to the theory with Kubo-Martin-Schwinger boundary conditions ones at the
one-temperature limit.


title:
Specific Features of Heavy Quark Production. LPHD approach to heavy
  particle spectra

abstract:
  Perturbative QCD formula for inclusive energy spectra of heavy quarks from
heavy quark initiated jets which takes into account collinear and/or soft
logarithms in all orders, the exact first order result and two-loop effects is
applied to distributions of heavy flavoured hadrons in the framework of the
LPHD concept. Fits to experimentally measured charm and bottom mean energy
losses result in $\alpha_{\MSbar}(M_Z)=0.125\pm 0.003\pm 0.004$ and
$(2\GeV)^{-1}\int_0^{2\GeV} dk \alpha_s^{eff}(k)= 0.18\pm 0.01\pm 0.02$ with
$\alpha_s^{eff}$ an infrared finite effective QCD coupling.


title: Is $M_t\simeq M_w$ Ruled Out?

abstract:
  A four generation supersymmetric model is proposed, in which the Tevatron
``top-quark'' events are reinterpreted as the production of $t^\prime$ which
decays dominantly to $bW^+$. In this model, $m_t\simeq m_W$, and
$t\rta\widetilde t\widetilde\chi^0_1$, with $\widetilde t\rta
c\widetilde\chi^0_1$. This decay chain, which rarely produces a hard isolated
lepton, would have been missed in all previous top quark searches. A narrow
region of the model parameter space exists which cannot yet be ruled out by
present data. This model predicts a rich spectrum of new physics which can be
probed at LEP-II and the Tevatron.


title: Limits on Non-Commuting Extended Technicolor

abstract:
  Using precision electroweak data, we put limits on non-commuting extended
technicolor models. We conclude that these models are viable only if the ETC
interactions are strong. Interestingly, these models predict a pattern of
deviations from the standard model which can fit the data significantly better
than the standard model does, even after taking into account the extra
parameters involved.


title: New third-family flavor physics and the top mass

abstract:
  A new massive gauge boson (X) coupling to the third family produces a
tantalizing pattern of deviations away from the standard model. These include
increasing Gamma_b/Gamma_h and decreasing the alpha_s(M_Z) extracted from
Gamma_h/Gamma_ell. We indicate how the X boson may be related to a dynamical
origin of the top mass.


title:
Electromagnetic Catalysis of a Neutrino Radiative decay or One More
  Source of Information on the Lepton Mixing Angles?

abstract:
  The radiative decay of ultrarelativistic massive neutrino $\nu_i \rightarrow
\nu_j \gamma$ is investigated in electromagnetic fields in the framework of the
Standard Model with lepton mixing. Estimates of the decay probability and
``decay cross-section'' for accelerator neutrinos of high energies in the
electric field of nucleus permit one to discuss the general possibility of
carrying out the neutrino experiment. Such an experiment could give unique
information on mixing angles in the lepton sector of the Standard Model which
would be almost independent of the specific neutrino masses.


title: Probing the Top-Quark Electric Dipole Moment at a Photon Linear Collider

abstract:
  We probe the top-quark electric dipole moment (EDM) in top-quark pair
production via photon-photon fusion at a photon linear collider. We show how
linearly-polarized photon beams can be used to extract information on the
top-quark EDM without the use of complicated angular correlations of top-quark
decay products. If the luminosity of the laser back-scattered photon-photon
collisions is comparable to that of the $e^+e^-$ collisions, then the
measurement of the top-quark EDM obtained by counting top-quark-production
events in photon fusion can be as accurate as the measurement obtained by
studying the $t\bar{t}$ decay correlations in $e^+e^-$ collisions using a
perfect detector.


title: The phenomenology of scalar octets

abstract:
  We discuss the phenomenology of colour scalar octets. Namely, we consider the
discovery potential of scalar octets at LEP, FNAL and LHC. Scalar octets decay
mainly into two gluons and new hadrons composed from scalar colour octets are
rather long lived $(\Gamma \leq O(10)Kev)$. For the scalar octet masses $M \geq
O(50)Gev$ scalar octets producing at FNAL or LHC decay into two gluons that
leads to additional four-jet events. We propose to look for scalar octets by
the measurement of the distributions of differential cross sections on the
invariant di-jet masses. Scalar octets naturally arise in models with
compactification of additional space dimensions. In such models the branching
ratio for the scalar octet bound state into two photons is $O(10^{-2})$ that
leads to the events with two photons and two jets. We also point out that the
current experimental data don't contradict to the existence of light ($M \sim
O(1)Gev$) scalar octets. Light scalar octets give additional contribution into
QCD $\beta$-function and allow to improve the agreement between deep inelastic
and LEP data.


title: Reggeization of quark-quark scattering amplitude in QCD

abstract:
  $s$-channel discontinuity of quark-quark scattering amplitude with gluon
quantum numbers in the $t$ channel and negative signature is calculated in the
Regge kinematical region in the two-loop approximation. Using this
discontinuity and assuming that the Regge asymptotic behaviour is given by the
Reggeized gluon contribution, we calculate the gluon trajectory in the two-loop
approximation. Remarkable cancellations lead to the independence of the
trajectory on properties of the scattered quarks, confirming the gluon
Reggeization.


title: Cosmic Strings are Current-Carrying

abstract:
  A synthesis of previous work done on the microscopic structure of cosmic
strings in realistic models is made and reveals that strings are expected to be
not only superconducting in the sense of Witten, but also generically
current-carrying, either at the GUT scale or at the electroweak scale. This
applies to any GUT string forming model leading to the standard electroweak
theory as a low energy limit. The current consists of charged vector bosons.
Cosmological consequences are briefly discussed.


title:
Constraints on "Fixed Point" QCD from the CCFR Data on Deep Inelastic
  Neutrino-Nucleon Scattering

abstract:
  The results of LO {\it Fixed point} QCD (FP-QCD) analysis of the CCFR data
for the nucleon structure function $~xF_3(x,Q^2)~$ are presented. The
predictions of FP-QCD, in which $~\alpha_{s}(Q^2)~$ tends to a nonzero coupling
constant $\alpha_{0}$ as $~Q^2\to \infty~,$ are in good agreement with the
data. If $~\alpha_{0}~$ is a first order zero of the $~\beta~$ function,
constraints for the possible values of the $~\beta~$ function parameter $~b~$
regulating how fast $~\alpha_ s(Q^2)~$ tends to its asymptotic value
$~\alpha_{0}~$ are found from the data. The corresponding values of
$~\alpha_{0}~$ are also determined. Having in mind the recent QCD fits to the
same data we conclude that in spite of the high precision and the large
$~(x,Q^2)~$ kinematic range of the CCFR data they cannot discriminate between
QCD and FP-QCD predictions for $~xF_3(x,Q^2)~$.
  PACS: 12.38.Qk; 19.90+b; 13.60 Hb


title:
Quantitative corrections to mass sum rules involving baryons containing
  heavy quarks

abstract:
  Quantitative corrections are estimated to three of Franklin's sum rules
involving the masses of baryons containing at least one charmed quark and to
three analogous sum rules for baryons containing at least one bottom quark. The
corrections arise from three-body contributions to baryon interaction energies
and are calculated from a semiempirical formula for the colormagnetic
contributions to baryon masses.


title: Hadronization in the SU(3) Nambu-Jona-Lasinio Model

abstract:
  The hadronization process for quarks combining into two mesons, q\bar q\to
MM' at temperature T is described within the SU(3) Nambu- Jona-Lasinio model
with finite current quark masses. Invariant matrix elements, cross-sections and
transition rates are calculated to leading order in a 1/N_c expansion. Four
independent classes, u\bar d, u\bar s, u\bar u and s\bar s\to hadrons are
analysed, and the yield is found to be dominated by pion production. Threshold
behaviour is determined by the exothermic or endothermic nature of the
processes constituting the hadronization class. A strong suppression of
transition rates is found at the pionic Mott temperature T_{M\pi}=212 MeV, at
which the pion becomes a resonant state. The mean time for hadronization is
calculated to be 2-4 fm/c near the Mott temperature. The calculation of
strangeness changing processes indicates that hadronization accounts for a 1%
increase in the absolute value of the kaon to pion ratio at T=150 MeV.


title:
Neutral-Kaon Production in e^+e^-, ep, and p\bar p Collisions at
  Next-to-Leading Order

abstract:
  We present new sets of fragmentation functions for neutral kaons, both at
leading and next-to-leading order. They are fitted to data on inclusive K^0
production in e^+e^- annihilation taken by MARK II at PEP (\sqrt s = 29 GeV)
and by ALEPH at LEP. Our fragmentation functions lead to a good description of
other e^+e^- data on inclusive K^0 production at various energies. They also
nicely agree with the K_S^0 transverse-momentum spectra measured by H1 at the
DESY ep collider HERA, by UA5 at the CERN Sp\bar pS Collider, and by CDF at the
Fermilab Tevatron.


title:
Non-perturbative aspects of screening phenomena in abelian and non
  abelian gauge theories

abstract:
  When computed to one-loop order in resummed perturbation theory, the
non-abelian Debye mass appears to be logarithmically sensitive to the magnetic
scale $g^2T$. More generally, we show that in higher orders power-like infrared
divergences forbid the use of perturbation theory to calculate the corrections
to Debye screening. A similar infrared problem occurs in the determination of
the mass-shell for the scalar propagator in 2+1-dimensional scalar
electrodynamics. In this context, we provide a non-perturbative approach which
solves the infrared problems and allows for an accurate calculation of the
scalar propagator in the vicinity of the mass-shell.


title: Is U(1)$_H$ a Good Family Symmetry?

abstract:
  We analyze U(1)$_H$ as a horizontal symmetry and its possibilities to explain
the known elementary-fermion masses. We find that only two candidates, in the
context of SU(3)$_c\otimes$SU(2)$_L\otimes$U(1)$_Y\otimes$U(1)$_H$
nonsupersymmetric, are able to fit the experimental result m$_b<<$m$_t$.


title: Axial form factor in the chiral quark soliton model

abstract:
  We calculate the axial form factor in the chiral quark soliton (semibosonized
Nambu - Jona-Lasinio) model using the semiclassical quantization scheme in the
next to leading order in angular velocity. The obtained axial form factor is in
a good absolute (without additional scaling) agreement with the experimental
data. Both the value at the origin and the $q$-dependence of the form factor as
well as the axial m.s.radius are fairly well reproduced.


title: Physics with jets in $p\bar p$ collisions

abstract:
  We discuss the possibilities for extracting information on the parton density
functions and the strong coupling constant from one- and two-jet events at the
Fermilab TEVATRON. First we study the inclusive two-jet triply differential
cross section $d^3\sigma/dE_Td\eta_1d\eta_2$. Different $\eta_1$ and $\eta_2$
pseudorapidity regions are directly related to the parton momentum fractions at
leading order and the shape of the triply differential distribution at fixed
transverse energy $E_T$ is a particularly powerful tool for constraining the
parton distributions at small to moderate $x$ values. Second, we consider the
one-jet inclusive transverse energy distribution where there is impressive
agreement between theory and experiment over a wide range of transverse energy.
By equating the next-to-leading order theoretical prediction for a given set of
input parton densities with the published CDF data, the evolution of the strong
coupling constant at scale $\mu$ can be studied between $\mu \sim 50~$GeV and
$\mu \sim 400~$GeV. This evolution is in agreement with QCD and corresponds to
$\alpha_s(M_Z)$ = 0.121 for the MRSA parameterisation.


title: The Determination of $\alpha_S$ at Hadron Colliders

abstract:
  Hadron colliders offer a unique opportunity to test perturbative QCD because,
rather than producing events at a specific beam energy, the dynamics of the
hard scattering is probed simultaneously at a wide range of momentum transfers.
This makes the determination of $\al$ and the parton density functions (PDF) at
hadron colliders particularly interesting. In this paper we restrict ourselves
to extracting $\al$ for a given PDF at a scale which is directly related to the
transverse energy produced in the collision. As an example, we focus on the
single jet inclusive transverse energy distribution and use the published
'88-'89 CDF data with an integrated luminosity of 4.2 pb$^{-1}$. The evolution
of the coupling constant over a wide range of scales (from 30~GeV to 500~GeV)
is clearly shown and is in agreement with the QCD expectation. The data to be
obtained in the current Tevatron run (expected to be well in excess 100
pb$^{-1}$ for both the CDF and D\O\ experiments) will significantly decrease
the experimental errors.


title: What Do We Know About the Tau Neutrino?

abstract:
  In this talk I review the present bounds on the tau neutrino, concentrating
on the possibility of bringing the mass bound below an MeV.


title: The status of the electroweak sector of the standard model

abstract:
  I will discuss the current status of the determination of $\alpha(m_Z)$ and
$\alpha_s(m_Z)$.


title: Quark and Gluon Propagators from Meson Data

abstract:
  We report robust calculations of various low energy QCD hadronic properties.
We use a multi-rank separable expansion for the gluon propagator which greatly
facilitates the numerical computations within the Global Colour Model for QCD.
The parameters for the propagators are determined by fitting experimental
values for $f_{\pi}$ and the $\pi$ and $a_1$ meson masses.


title: On the $k_{\perp}$ dependent gluon density in hadrons and the photon

abstract:
  The $k_{\perp}$ dependent gluon distribution for protons, pions,and photons
is calculated accounting for the resummation of small~$x$ effects due to the
Lipatov equation. It is represented by a convolution of a gluon density in the
collinear limit and a universal function ${\cal G}(x,k^2,\mu)$ for which an
analytic expression is derived.


title: Calculating the diffractive from the inclusive structure function

abstract:
  It is demonstrated that the global properties of the rapidity gap events at
HERA can be understood based on electron-gluon scattering and a
non-perturbative mechanism of colour neutralization. Using the measured
inclusive structure function $F_2$ to determine the parameters of the parton
model, the diffractive structure function $F_2^D$ is predicted. The ratio of
diffractive and inclusive cross sections, $R_D = \sigma_D/\sigma_{incl}\simeq
1/9$, is determined by the probability of the produced quark-antiquark pair to
evolve into a colour singlet state.


title: The Electromagnetic Interaction in Chiral Perturbation Theory

abstract:
  We investigate electromagnetic effects in the framework of chiral
perturbation theory. Using a completely independent method, we confirm Urech's
results for the divergences of the one--loop functional in the electromagnetic
sector. We perform a one--loop analysis of all $P_{\ell 2}$ ($P = \pi, K,
\eta$) and the $K_{\ell 3}$ form factors $f_+^{K^+\pi^0}(0)$,
$f_+^{K^0\pi^-}(0)$, including a systematic treatment of the $\cO(e^2p^2)$
contributions in the mesonic part. We illustrate our results by several
numerical estimates.


title:
Should the Pomeron and imaginary parts be modelled by two gluons and
  real quarks?

abstract:
  We illustrate that solution of the Schwinger-Dyson equation for the gluon
propagator in QCD does not support an infrared softened behaviour, but only an
infrared enhancement. This has consequences for the modelling of the Pomeron in
terms of dressed gluon exchange. It highlights that an understanding of the
Pomeron within QCD must take account of the bound state nature of hadrons.


title:
Isospin Breaking and the Top-Quark Mass in Models of Dynamical
  Electroweak Symmetry Breaking

abstract:
  In this talk we review the physics of top-quark mass generation in models of
dynamical electroweak symmetry breaking and the constraints on this physics
arising from limits on the deviation of the weak interaction $\rho$-parameter
from one. We then discuss top-color assisted technicolor in this context.


title:
The Calculation of the Two-Loop Spin Splitting Functions
  $P_{ij}^{(1)}(x)$

abstract:
  We present the calculation of the two-loop spin splitting functions
$P_{ij}^{(1)}(x)\; (i,j = q,g)$ contributing to the next-to-leading order
corrected spin structure function $g_1(x,Q^2)$. These splitting functions,
which are presented in the \MSbs, are derived from the order $\alpha_s^2$
contribution to the anomalous dimensions $\gamma_{ij}^{m} \; (i,j = q,g)$. The
latter correspond to the local operators which appear in the operator product
expansion of two electromagnetic currents. Some of the properties of the
anomalous dimensions will be discussed. In particular our findings are in
agreement with the supersymmetric relation
$\gamma_{qq}^{m}+\gamma_{gq}^{m}-\gamma_{qg}^{m}-\gamma_{gg}^{m}=0$ up to order
$\alpha_s^2$.


title: Power corrections and renormalons in Drell-Yan production

abstract:
  The resummed Drell-Yan cross section in the double-logarithmic approximation
suffers from infrared renormalons. Their presence was interpreted as an
indication for non-perturbative corrections of order $\lqcd/(Q(1-z))$. We find
that, once soft gluon emission is accurately taken into account, the leading
renormalon divergence in the resummed cross section is cancelled by
higher-order perturbative contributions in the exponent of the resummed cross
section. From this evidence, `higher twist' corrections to the hard cross
section in Drell-Yan production should therefore intervene only at order
$\lqcd^2/((Q^2 (1-z)^2)$ in the entire perturbative domain $Q (1-z) > \lqcd$.
We compare this result with hadronic event shape variables, comment on the
potential universality of non-perturbative corrections to resummed cross
sections, and on possible implications for phenomenology.


title: Multiple Interactions in gamma gamma Collisions

abstract:
  The cross--section for two--photon events with (at least) two independent
partonic scatters is estimated, for LEP energies as well as a 500 GeV ``photon
collider". This results in events with (at least) four central (mini--)jets.
Such events might be found in existing data, and should be clearly seen at the
second stage of LEP.


title: Hard Diffraction at HERA and the Gluonic Content of the Pomeron

abstract:
  We show that the previously introduced CKMT model, based on conventional
Regge theory, gives a good description of the HERA data on the structure
function F_2^D for large rapidity gap (diffractive) events. These data allow,
not only to determine the valence and sea quark content of the Pomeron, but
also, through their Q^2 dependence, give information on its gluonic content.
Using DGLAP evolution, we find that the gluon distribution in the Pomeron is
very hard and the gluons carry more momentum than the quarks. This indicates
that the Pomeron, unlike ordinary hadrons, is a mostly gluonic object. With our
definition of the Pomeron flux factor the total momentum carried by quarks and
gluons turns out to be 0.3-0.4 - strongly violating the momentum sum rule.


title:
Production and Two-photon Decay of the MSSM Scalar Higgs Bosons at the
  LHC

abstract:
  We consider the production and two-photon decay of the $CP$-even Higgs bosons
($h^0$ and $H^0$) of the Minimal Supersymmetric Standard Model (MSSM) at the
Large Hadron Collider. We study in detail the dependence of the cross section
on various parameters of the MSSM, especially the dependence on the mixing
effects in the squark sector due to the Higgs bilinear parameter $\mu$ and the
soft supersymmetry breaking parameter $A$. We find that the cross section for
the production of these Higgs bosons has a significant dependence on the
parameters which determine the chiral mixing in the squark sector. 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. For the $H^0$ the two-photon branching ratio
is only significant if the $H^0$ is light, but then the cross section times the
branching ratio may exceed 200~fb. The QCD corrections due to quark loop
contributions are known to increase the cross section by 50\%. We find the
dependence of the cross section on the gluon distribution function used to be
rather insignificant.


title:
Glueballs from 1+1 Dimensional Gauge Theories with Transverse Degrees of
  Freedom

abstract:
  We study $1+1$-dimensional $SU(N)$ gauge theories with adjoint scalar matter
representations, based on a dimensional truncation of $2+1$ and
$3+1$-dimensional pure QCD, which approximate the dynamics of transversely
polarized gluons. The glueballs are investigated non-perturbatively using
light-front quantisation, detailed spectra and wavefunctions being obtained for
the large-$N$ limit. In general there is some qualitative agreement of the
spectra with lattice Monte Carlo data from the higher dimensional QCD. From the
light-front wavefunctions we calculate (polarized) structure functions and
interpret the gluon and spin content of glueballs. We discuss the phase
structure of the reduced theories in relation to matrix models for relativistic
non-critical strings.


title:
Two Photon Processes and Effective Lagrangians with An Extended Scalar
  Sector

abstract:
  We consider the Standard Model with an extended scalar sector, and study the
possible effects of the physics underlying such a model using an effective
lagrangian parametrization. It is found that certain two photon processes offer
windows where such heavy interactions might be glimpsed, but the realization of
this expectation requires enormous experimental precision.


title:
The Role of Gravity in Determining Physics at High as Well as Low
  Energies

abstract:
  It is noted that in the context of a supersymmetric preonic approach to
unification, gravity, though weak, can play an essential role in determining
some crucial aspects of low-energy physics. These include: (i) SUSY-breaking,
(ii) electroweak symmetry-breaking, and (iii) generation of masses of quarks
and leptons, all of which would vanish if we turn off gravity. Such a role of
gravity has its roots in the Witten index theorem which would forbid
SUSY-breaking, within the class of theories under consideration, in the absence
of gravity.


title: Prospects for Supersymmetry at LEP2

abstract:
  Working within the framework of the minimal supergravity model with gauge
coupling unification and radiative electroweak symmetry breaking (SUGRA), we
map out regions of parameter space explorable by experiments at LEP2, for
center of mass energy options of $\sqrt{s}=150,\ 175$, $190$ and 205 GeV. We
compute signals from all accessible $2 \rightarrow 2$ SUSY pair production
processes using the ISAJET simulation program, and devise cuts that enhance the
signal relative to Standard Model backgrounds, and which also serve to
differentiate various supersymmetric processes from one another. We delineate
regions of SUGRA parameter space where production of neutralino pairs, chargino
pairs, slepton pairs and the production of the light Higgs scalar of SUSY is
detectable above Standard Model backgrounds and distinguishable from other SUSY
processes. In addition, we find small regions of SUGRA parameter space where
$\te\te$, $\tz_2\tz_2$ and $\tnu_L\tnu_L$ production yields spectacular events
with up to four isolated leptons. The combined regions of parameter space
explorable by LEP2 are compared with the reach of Tevatron Main Injector era
experiments. Finally, we comment on how the reach via the neutralino pair
channel is altered when the radiative electroweak symmetry breaking constraint
is relaxed.


title: Light U(1) Gauge Boson Coupled to Baryon Number

abstract:
  We discuss the phenomenology of a light U(1) gauge boson, $\gamma_B$, that
couples only to baryon number. Gauging baryon number at high energies can
prevent dangerous baryon-number violating operators that may be generated by
Planck scale physics. However, we assume at low energies that the new U(1)
gauge symmetry is spontaneously broken and that the $\gamma_B$ mass $m_B$ is
smaller than $m_Z$. We show for $m_\Upsilon<m_B<m_Z$ that the $\gamma_B$
coupling $\alpha_B$ can be as large as $\sim 0.1$ without conflicting with the
current experimental constraints. We argue that $\alpha_B\sim 0.1$ is large
enough to produce visible collider signatures and that evidence for the
$\gamma_B$ could be hidden in existing LEP data. We show that there are
realistic models in which mixing between the $\gamma_B$ and the electroweak
gauge bosons occurs only as a radiative effect and does not lead to conflict
with precision electroweak measurements. Such mixing may nevertheless provide a
leptonic signal for models of this type at an upgraded Tevatron.


title: Top-Quark Decay Via Flavor-Changing Neutral Currents at Hadron Colliders

abstract:
  We study low energy experimental constraints on an anomalous top-quark
coupling associated with the flavor-changing neutral current vertex $Z \bar t
c$. In view of these constraints, we discuss the experimental observability of
the induced rare decay mode $t \rightarrow Zc$, both at the Fermilab Tevatron
(with the Main Injector or a luminosity-upgrade) and at the LHC.


title:
Improved Evaluation of the NNLO QCD Effects in the Tau Decay,
  $e^{+}e^{-}$ Annihilation into Hadrons and Deep-Inelastic Sum Rules

abstract:
  A systematic method is proposed for analyzing the renormalization scheme
uncertainties in the next-next-to-leading order QCD predicitions, based on a
condition which eliminates schemes that give rise to large cancellations in the
expression for the characteristic scheme invariant combination of the expansion
coefficients. Using this method it is shown that the QCD corrections to the tau
lepton decay are rather stable with respect to change of the scheme, provided
that an improved formula is used, which involves numerical evaluation of the
contour integral in the complex energy plane with the Adler function under the
integral. Optimized predictions for the tau decay corrections are given. It is
shown that also in the case of the of QCD corrections to $e^{+}e^{-}$
annihilation into hadrons the conventional expansion has sizable scheme
dependence, even at large energies. However, a considerable improvement is
obtained when the QCD corrections are expressed as a contour integral, with the
Adler function under the integral, resumming in this way the large $\pi^{2}$
contributions. In the case of the corrections to the Bjorken sum rule for
polarized structure functions it is found that for $n_{f}=4$ they are
insensitive to change of the scheme. However, the $n_{f}=3$ expression is found
to be strongly scheme dependent at lower energies.


title: Structure and Decays of Particles Containing Heavy Quarks (Theory)

abstract:
  Some recent results and problems in the theory of particles containing heavy
quarks ar reviewed.


title:
Monopole Excitations of Baryons in the Nambu--Jona--Lasinio Soliton
  Model

abstract:
  We investigate the monopole excitations of the soliton in the
Nambu--Jona--Lasinio model. By studying the solutions to the corresponding
Bethe--Salpeter equation in the background of the soliton we exclude the
existence of real large amplitude fluctuations. This allows us to treat the
collective coordinate for the monopole excitations, which parametrizes the
extension of the soliton, in the harmonic approximation. The canonical
quantization of this coordinate yields a spectrum which agrees reasonably well
with the empirical data for the Roper resonance, N(1440), and the corresponding
one for the Delta, $\Delta$(1600). We also comment on going beyond the harmonic
approximation.


title:
The large top quark mass expansion for Higgs boson decays into bottom
  quarks and into gluons

abstract:
  We calculate the large top quark mass expansions for the H -> bb_bar decay
rate in the order (alpha_s)^2 and for the H -> gluons decay rate in the order
(alpha_s)^3. The obtained expansions rapidly converge in the region of their
validity, M_H < 2 m_top, i.e. below the threshold of tt_bar production.


title:
Finite width and irreducible background effects to $t\bar t$ production
  at $\gamma\gamma$ Next Linear Colliders

abstract:
  We study the complete process \phphbbww\ using exact matrix element
computations at tree-level, at a $\sqrt s=500$ GeV \eeb\ linear collider of the
next generation. Incoming photons produced via back-scattering of laser light
are considered. Sizable effects due to the finite width of the top quark as
well as to the irreducible background to $t\bar t$ production and decay are
predicted.


title: Infra--red soft universality

abstract:
  We show that in a special class of theories the commonly assumed universal
form of the soft supersymmetry--breaking terms is approached in the infra--red
limit. The resulting universal scalar mass and trilinear coupling are predicted
in terms of the gaugino mass.


title: Energy Dependence of Strange Particle Yields from a QGP-Fireball

abstract:
  We explore, as function of the collision energy and stopping in relativistic
nuclear collisions, the production yields of strange particles, in particular
strange antibaryons,assuming formation of a deconfined thermal QGP-fireball
which undergoes a sudden hadronisation. The non-equilibrium freeze-out
conditions are established and strange antibaryon excitation functions are
shown to have characteristic features that should allow to discriminate between
the QGP hypothesis and other reaction scenarios.


title: QGP Formation and Strange Antibaryons

abstract:
  We analyze current experimental results and explore, as function of the
collision energy and stopping in relativistic nuclear collisions, the
production yields of strange antibaryons, assuming formation of a deconfined
thermal QGP-fireball which undergoes a sudden hadronisation.


title:
The ``Out-Longitudinal'' Cross Term and Other Model Independent Features
  of the Two-Particle HBT Correlation Function

abstract:
  Using two specific models and a model independent formalism, we show that an
``out-longitudinal'' cross term should be included in any gaussian fits to
correlation data. In addition, we show that correlation radii (including the
cross term) measure lengths of homogeneity within the source, not necessarily
geometric sizes.


title:
Spontaneous CP violation in supersymmetric models with four higgs
  doublets

abstract:
  We consider supersymmetric extensions of the standard model with two pairs of
Higgs doublets. We study the possibility that CP violation is generated
spontaneously in the scalar sector via vacuum expectation values (VEVs) of the
Higgs fields. Using a simple geometrical interpretation of the minimum
conditions we prove that the minimum of the tree-level scalar potential for
these models is allways real. We show that complex VEVs can appear once
radiative corrections and/or explicit {\it soft} CP violating terms are added
to the effective potential.


title: On Non-Standard Couplings among the Electroweak Vector Bosons

abstract:
  Application of a Stueckelberg transformation allows one to connect various
Lagrangians which have been independently proposed for non-standard couplings.
We discuss the reduction of the number of independent parameters in the
Lagrangian and compare symmetry arguments with dimensional arguments.


title:
Effects of Symmetry Breaking on the Strong and Electroweak Interactions
  of the Vector Nonet

abstract:
  Starting from a chiral invariant and quark line rule conserving Lagrangian of
pseudoscalar and vector nonets we introduce first and second order symmetry
breaking as well as quark line rule violating terms and fit the parameters, at
tree level, to many strong and electroweak processes. A number of predictions
are made. The electroweak interactions are included in a manifestly gauge
invariant manner. The resulting symmetry breaking pattern is discussed in
detail. Specifically, for the ``strong'' interactions, we study all the vector
meson masses and V -> \phi \phi decays, including isotopic spin violations. In
the electroweak sector we study the { rho^0 , omega , phi } -> e^+e^- decays, {
pi^+ , K^+ , K^0 } ``charge radii'', K_{l3} ``slope factor'' and the overall
e^+e^- -> pi^+ pi^- process. It is hoped that the resulting model may be useful
as a reasonable description of low energy physics in the range up to about 1
GeV.


title: Systematics of Heavy Quark Production at HERA

abstract:
  We discuss heavy quark and quarkonium production in various kinematic regions
at the HERA ep collider. In contrast to fixed target experiments, collider
kinematics allows the possibility of detailed measurements of particle
production in the proton fragmentation region. One thus can study parton
correlations in the proton Fock states materialized by the virtual photon
probe. We discuss various configurations of inelastic electron-proton
scattering, including peripheral, diffractive, and deep inelastic processes. In
particular, we show that intrinsic heavy quark Fock states can be identified by
the observation of quarkonium production at large $x_F$ and a low mean
transverse momentum which is insensitive to the virtuality $Q^2$ of the photon.