title: The Delta I = 1/2 Rule and B_K at O(p^4) in the Chiral Expansion

abstract:
  We calculate the hadronic matrix elements to $O(p^4)$ in the chiral expansion
for the ($\Delta S =1$) $K^0 \to 2 \pi$ decays and the ($\Delta S=2$) $\bar
K^0$-$K^0$ oscillation. This is done within the framework of the chiral quark
model. The chiral coefficients thus determined depend on the values of the
quark and gluon condensates and the constituent quark mass. We show that it is
possible to fit the $\Delta I =1/2$ rule of kaon decays with values of the
condensates close to those obtained by QCD sum rules. The renormalization
invariant amplitudes are obtained by matching the hadronic matrix elements and
their chiral corrections to the short-distance NLO Wilson coefficients. For the
same input values, we study the parameter $\hat B_K$ of kaon oscillation and
find $\hat B_K = 1.1 \pm 0.2$. As an independent check, we determine $\hat B_K$
from the experimental value of the $K_L$-$K_S$ mass difference by using our
calculation of the long-distance contributions. The destructive interplay
between the short- and long-distance amplitudes yields $\hat B_K = 1.2 \pm
0.1$, in agreement with the direct calculation.


title: Electroweak dipole moment form factors of the top quark in supersymmetry

abstract:
  The CP violating electric and weak dipole moment form factors of the top
quark appear in the process $e^{+}e^{-} --> t\bar{t}$. We present a complete
analysis of these dipole moment form factors within the Minimal Supersymmetric
Standard Model with complex parameters. We include gluino, chargino, and
neutralino exchange in the loop of the $\gamma t\bar{t}$ and $Z t\bar{t}$
vertex. We give the analytic expressions and present numerical results.


title: Vortex-Antivortex Pair Production in a First Order Phase Transition

abstract:
  We carry out numerical simulation of a first order phase transition in 2+1
dimensions by randomly nucleating bubbles, and study the formation of global
U(1) vortices. Bubbles grow and coalesce and vortices are formed at junctions
of bubbles via standard Kibble mechanism as well as due to a new mechanism,
recently proposed by us, where defect-antidefect pairs are produced due to
field oscillations. We make a comparative study of the contribution of both of
these mechanisms for vortex production. We find that, for high nucleation rate
of bubbles, vortex-antivortex pairs produced via the new mechanism have
overlapping configurations, and annihilate quickly; so only those vortices
survive till late which are produced via the Kibble mechanism. However, for low
nucleation rates, bubble collisions are energetic enough to lead to many well
separated vortex-antivortex pairs being produced via the new mechanism. For
example, in a simulation involving nucleation of 20 bubbles, a total of 14
non-overlapping vortices and antivortices formed via this new mechanism of pair
creation (6 of them being very well separated), as compared to 6 vortices and
antivortices produced via the Kibble mechanism. Our results show the
possibility that in extremely energetic bubble collisions, such as those in the
inflationary models of the early Universe, this new mechanism may drastically
affect the defect production scenario.


title: Spin Dependent Drell Yan and Double Prompt Photon Production to NLO QCD

abstract:
  We present the complete $O(\alpha_s^2)$ radiative corrections to the (non
singlet) polarized Drell Yan cross section for the production of a lepton pair
with a nonzero $q_T$. The helicity of the incoming states is arbitrary. In the
case of double photon, results for the longitudinal asymmetries and on the
$p_T$ behavior of the cross section are also given (to $O(\alpha_{em}^2\alpha_s
)$) in the central rapidity region of the tagged photon.


title: Computing the Strong Sphaleron Rate

abstract:
  We measure the diffusion constant for Chern-Simons number for classical,
lattice SU(3) Yang-Mills theory, using a generalization of the topological
definition of Chern-Simons number developed recently by Moore and Turok. The
diffusion constant is much larger than that for SU(2), even before the ratio of
coupling constants has been accounted for, which implies that chiral quark
number is efficiently destroyed by strong processes during the electroweak
phase transition. For the physical value of \alpha_s we estimate the decay time
for chiral quark number to be about 80/T, although various systematics make
this number uncertain by about a factor of 2.


title:
Spin Dependent Drell Yan in QCD to $O(\alpha_s^2)$ (I). (The Non-Singlet
  Sector)

abstract:
  A study of the order $\alpha_s^2$ corrections to the Drell Yan (non-singlet)
cross section for incoming states of arbitrary longitudinal helicities is
presented. The study is performed in the case of the transverse momentum
distributions, $(q_T)$, of the lepton pair and extends the calculation of Ellis
Martinelli and Petronzio (EMP) to the polarized case. We use the $\bar{MS}$
scheme and the t'Hooft-Veltman regularization for the helicity projectors. From
our results one can obtain the bulk of the totally inclusive NNLO cross section
for the production of a Drell Yan pair in the non-singlet sector by a simple
integration over the heavy photon momentum. We show that in the $\bar{MS}$
helicity is not conserved, unless a finite renormalization is done to reenter
into a physical scheme ($\bar{MS}_p$). This aspect of the calculation follows
the same trend as in polarized production of single and double photon to
$O(\alpha_s^2)$. In the unpolarized limit we reproduce all the results of EMP.


title: Partonic Picture of Nuclear Shadowing at Small x

abstract:
  We investigate the nuclear shadowing mechanism in the context of perturbative
QCD and the Glauber multiple scattering model. Using recent HERA data on
nucleon structure function at small $x$, we put stringent constrains on the
nucleon gluon density in the double-logarithm approximation. We suggest that
the scaling violation of the nucleon structure function in the region of small
$x$ and semihard scale $Q^2$ can be reliably described by perturbative QCD
which is a central key to the understanding of the scale dependence of the
nuclear shadowing effect. Our results indicate that while the shadowing of the
quark density arises from an interplay between the ``soft'' and semihard QCD
processes, the gluon shadowing is largely driven by a perturbative shadowing
mechanism. We demonstrate that the gluon shadowing is a robust phenomenon at
large $Q^2$ and can be unambiguously predicted by perturbative QCD.


title: Why is the B -> eta' X decay width so large ?

abstract:
  New mechanism for the observed inclusive B -> \eta'X decay is suggested. We
argue that the dominant contribution to this amplitude is due to the Cabbibo
favored b -> \bar{c}cs process followed by the transition \bar{c}c -> \eta'. A
large magnitude of the "intrinsic charm" component of \eta' is of critical
importance in our approach. Our results are consistent with an unexpectedly
large Br(B -> \eta'+X) \sim 10^{-3} recently announced by CLEO. We stress the
uniqueness of this channel for 0^{-+} gluonia search.


title: Precision Corrections to Dispersive Bounds on Form Factors

abstract:
  We present precision corrections to dispersion relation bounds on form
factors in bottom hadron semileptonic decays and analyze their effects on
parameterizations derived from these bounds. We incorporate QCD two-loop and
nonperturbative corrections to the two-point correlator, consider form factors
whose contribution to decay rates is suppressed by lepton mass, and implement
more realistic estimates of truncation errors associated with the
parameterizations. We include higher resonances in the hadronic sum that,
together with heavy quark symmetry relations near zero recoil, further tighten
the sum rule bounds. Utilizing all these improvements, we show that each of the
six form factors in B --> D l nu and B --> D^* l nu can be described with 3% or
smaller precision using only the overall normalization and one unknown
parameter. A similar one-coefficient parameterization of one of the Lambda_b
--> Lambda_c l nu form factors, together with heavy quark symmetry relations
valid to order 1/m^2, describes the differential baryon decay rate in terms of
one unknown parameter and the phenomenologically interesting quantity (\bar
Lambda)_Lambda \approx M_{Lambda_b} - m_b. We discuss the validity of
slope-curvature relations derived by Caprini and Neubert, and present weaker,
corrected relations. Finally, we present sample fits of current experimental B
--> D^*l nu and B --> D l nu data to the improved one-parameter expansion.


title: Corrections of Order $\Lambda^2_{QCD}/m^2_c$ to Inclusive Rare B Decays

abstract:
  We calculate nonperturbative ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections to
the dilepton invariant mass spectrum and the forward-backward charge asymmetry
in $B\to X_se^+e^-$ decay using a heavy quark expansion approach. The method
has recently been used to estimate long-distance effects in $B\to X_s\gamma$.
We generalize this analysis to the case of nonvanishing photon invariant mass,
$q^2\not= 0$, relevant for the rare decay mode $B\to X_se^+e^-$. In the
phenomenologically interesting $q^2$ region away from the $c\bar c$ resonances,
the heavy quark expansion approach should provide a reasonable description of
possible nonperturbative corrections. In particular this picture is preferable
to the model-dependent approach relying on the tails of Breit-Wigner
resonances, which has been employed so far in the literature to account for
these effects. We find that the ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections
to the dilepton invariant mass spectrum and to the forward-backward asymmetry
in $B\to X_se^+e^-$ amount to several percent at most for $q^2/m^2_b < 0.3$ and
$q^2/m^2_b > 0.6$. The ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ correction to the
$B\to X_s\gamma$ decay rate is also computed and found to be +3%, which agrees
in magnitude with previous calculations. Finally, we comment on long-distance
effects in $B\to X_s\nu\bar\nu$, which in this case are extremely suppressed
due to the absence of virtual photon contributions.


title: Heavy Quark Current Correlators to O(\alpha_s^2)

abstract:
  In this paper the three-loop polarization functions \Pi(q^2) are calculated
for the cases of an external vector, axial-vector, scalar or pseudo-scalar
current. Results are presented for the imaginary part which directly leads to
the cross section $\sigma(e^+e^- \to Z \to hadrons)$ and to the Higgs decay
rates, respectively.


title: Fluctuations In ``BR-Scaled'' Chiral Lagrangians

abstract:
  We develop arguments for "mapping" the effective chiral Lagrangian whose
parameters are given by "BR scaling" to a Landau Fermi-liquid fixed-point
theory for nuclear matter in describing fluctuations in various flavor (e.g.,
strangeness) directions. We use for this purpose the effective Lagrangian used
by Furnstahl, Tang and Serot that incorporates the trace anomaly of QCD in
terms of a light-quark (quarkonium) degree of freedom with the heavy (gluonium)
degree of freedom integrated out. The large anomalous dimension $d_{an}\approx
5/3$ for the scalar field found by Furnstahl et al to be needed for a correct
description of nuclear matter is interpreted as an indication for a
strong-coupling regime and the ground state given by the BR-scaled parameters
is suggested as the background around which fluctuations can be rendered weak
so that mean-field approximation is reliable. We construct a simple model with
BR scaled parameters that provides a satisfactory description of the properties
of matter at normal nuclear matter density. Given this, fluctuations around the
BR scaled background are dominated by tree diagrams. Our reasoning relies
heavily on recent developments in the study of nucleon and kaon properties in
normal and dense nuclear matter, e.g., nucleon and kaon flows in heavy-ion
processes, kaonic atoms, and kaon condensation in dense compact-star matter.


title: The bottom baryon pair production in the e^+e^- annihilation

abstract:
  In the framework of the nonrelativistic diquark model of the heavy baryons
and the perturbative approach of QCD we predict the value and energy dependence
for the total cross section of the Lambda_b- and Sigma_b^* -baryons pair
production at the energy range of the KEKB and PEP-II e^+e^- colliders.


title:
Production and absorption of $c \bar{c}$ pairs in nuclear collisions at
  SPS energies

abstract:
  We study the production of $c \bar{c}$ pairs and dimuons from hard collisions
in nuclear reactions within the covariant transport approach HSD, which
describes successfully both hadronic and electromagnetic observables from p+A
and A+A collisions from SIS to SPS energies. The production of $c \bar{c}$ and
Drell-Yan pairs is treated perturbatively employing experimental cross sections
while the interactions of $c\bar{c}$ pairs with hadrons are included by
conventional cascade-type two-body collisions. Adopting 6mb for the $c
\bar{c}$-baryon cross sections the data on $J/\Psi$ suppression in p+A
reactions are reproduced in line with calculations based on the Glauber model.
We study different models for $c \bar{c}$ dissociation on mesons in comparison
with the experimental data of the HELIOS-3, NA38 and NA50 collaborations.
Adopting absorption cross sections with mesons above the $D\bar{D}$ threshold
in the order of 1.5 - 3mb we find that all data on $J/\Psi$ suppression from
both proton-nucleus and nucleus-nucleus collisions can be described without
assuming the formation of a quark-gluon plasma in these collisions.


title:
Dijet hadroproduction with rapidity gaps and QCD double logarithmic
  effects

abstract:
  We show that the hadroproduction of a pair of jets with large transverse
energy in the central region bounded by rapidity gaps is an ideal process to
see important double logarithmic QCD suppression effects. We compute the cross
sections for both exclusive and inclusive double-diffractive dijet production
at Tevatron and LHC energies for a range of rapidity configurations.


title: Strangeness enhancement in the String Fusion Model Code

abstract:
  String Fusion Model Code results for Pb--Pb central collisions at SPS
energies including the string fusion interaction mechanism are compared to the
last experimental data. Predictions for RHIC energies are also presented. On
the other hand, the evolution of the strangeness enhancement ratio
$E_s=\frac{<\Lambda>+4<K_s^0>}{3<\pi^->}$ with the energy and with the atomic
number of participant nuclei is discussed.


title: Analysis of DCC Domain Structure

abstract:
  Wavelet-type methods are employed for the analysis of pion field
configurations that have been obtained by dynamical simulations in idealized
scenarios relevant to the formation of disoriented chiral condensates. It is
illustrated how the measurement of the isospin domain structure depends on the
ability to zoom in on limited parts of the phase space, due to the interplay
between the pion correlation length and the effective source geometry. The need
for advanced analysis methods is underscored by the fact that the extracted
neutral-fraction distribution would differ significantly from the ideal form,
even under perfect experimental conditions, and, moreover, by the circumstance
that thermal sources with suitably adjusted temperatures can lead to
distributions that may be practically indistinguishable from those arising from
DCC-type non-equilibrium evolutions.


title: Probe New Physics in Leptonic $ B_c$ Decays at CERN LHC

abstract:
  With respect to large samples of $B_c$ mesons expected to be produced at CERN
Large Hadron Collider(LHC) and the large branching ratios $Br(B_{c}\to
\tau\bar\nu)$ and $Br(B_{c}\to \mu\bar\nu)$, we suggest that $B_c$ purely
leptonic decays could offer an unique probe of the standard model and its
extensions such as two Higgs doublet models and models involving supersymmetry,
and also the structure of charged weak currents.


title: CP Violation in the B Meson System

abstract:
  CP violation in $B$ decays is reviewed in the Standard Model (SM) and beyond
the SM. The present explanation of CP violation in terms of a phase in the
Cabibbo-Kobayashi-Maskawa (CKM) matrix can be tested through a variety of CP
asymmetries in neutral and charged $B$ decays. Usually, new mechanisms of CP
nonconservation enter via $B-\bar{B}$ mixing and violate SM constraints on the
CKM parameters in a few characteristic ways. Different models can be partially
distinguished by penguin-dominated $B$ decay rate measurements. In radiative
decays, large mixing-induced asymmetries may occur due to new contributions to
the decay amplitude.


title: The rephasing freedom and the NNI form of quark mass matrices

abstract:
  For three generations of quarks, we show that one of quark mass matrices can
be transformed into either a Fritzsch form or a Branco-Silva-Marcos form, while
the other is kept in the NNI basis. In these bases, quark mass matrices are
determined unambiguously once quark masses and the CKM mixing are given.


title:
On the Evolution Kernels of Twist 2 Light-Ray Operators for Unpolarized
  and Polarized Deep Inelastic Scattering

abstract:
  The non-singlet and singlet evolution kernels of the twist--2 light-ray
operators for unpolarized and polarized deep inelastic scattering are
calculated in $O(\alpha_s)$ for the general case of virtualities $q^2, q'^2
\neq 0$. Special cases as the kernels for the general single-variable evolution
equation and the Altarelli-Parisi and Brodsky-Lepage limits are derived from
these results.


title: Flavor Alignment Solutions to the Strong CP Problem in Supersymmetry

abstract:
  An approach to solving the Strong CP Problem in supersymmetric theories is
discussed which uses abelian family symmetries to align the mass matrices of
the quarks and squarks. In this way both the Strong CP Problem and the
characteristic flavor and CP problems of supersymmetry can be solved in a
single way.


title: The Sliding-singlet Mechanism Revived

abstract:
  It is shown, using a modification of an idea of Sen, that completely
realistic supersymmetric grand-unified theories based on SU(6) or larger
unitary groups can be constructed using the sliding-singlet mechanism. These
models have a simple structure, preserve the successful prediction of $\sin^2
\theta_W$, and can suppress Higgsino-mediated proton decay to an acceptable
level in a simple way.


title: Nucleon Form Factors in a Covariant Diquark-Quark Model

abstract:
  In a model where constituent quarks and diquarks interact through quark
exchange the Bethe-Salpeter equation in ladder approximation for the nucleon is
solved. Quark and diquark confinement is effectively parametrized by choosing
appropriately modified propagators. The coupling to external currents is
implemented via nontrivial vertex functions for quarks and diquarks to ensure
gauge invariance at the constituent level. Nucleon matrix elements are
evaluated in a generalised impulse approximation, and electromagnetic, pionic
and axial form factors are calculated.


title: Four loop anomalous dimensions of gradient operators in phi^4 theory

abstract:
  We compute the anomalous dimensions of a set of composite operators which
involve derivatives at four loops in MSbar in phi^4 theory as a function of the
operator moment n. These operators are similar to the twist-2 operators which
arise in QCD in the operator product expansion in deep inelastic scattering. By
regarding their inverse Mellin transform as being equivalent to the DGLAP
splitting functions we explore to what extent taking a restricted set of
operator moments can give a good approximation to the exact four loop result.


title: New QCD Sum Rules for Nucleon Tensor Charge

abstract:
  Two new QCD sum rules for nucleon tensor charge are derived from a mixed
correlator of spin-1/2 and spin-3/2 nucleon interpolating fields. These sum
rules are analyzed along with a sum rule obtained from the usual correlator of
a general spin-1/2 nucleon interpolating field. The validity and reliability of
the sum rules are examined by monitoring the contaminations arising from the
transitions and continuum and the convergence of the operator product
expansion. Valid sum rules are identified and their predictions are presented.
It is found that the vacuum tensor susceptibility induced by the external field
plays an important role in determining both the validity and predictions of the
sum rules. The uncertainties associated with the sum-rule predictions are also
discussed.


title: A Model of Yukawa Hierarchies

abstract:
  We present a model for the observed hierarchies among the Yukawa couplings of
the standard model in the context of an effective low energy theory with an
anomalous U(1) symmetry. This symmetry, a generic feature of superstring
compactification, is a remnant of the Green-Schwarz anomaly cancellation
mechanism. The gauge group is that of the standard model, augmented by X, the
anomalous U(1), and two family-dependent phase symmetries $Y^{(1)}$ and
$Y^{(2)}$. The correct hierarchies are reproduced only when $sin^2\theta_w=3/8$
at the cut-off. To cancel anomalies, right-handed neutrinos and other standard
model singlets must be introduced. Independently of the charges of the
right-handed neutrinos, this model produces the same neutrino mixing matrix and
an inverted hierarchy of neutrino masses. The heaviest is the electron neutrino
with a mass $\sim 1$ meV, and mixing of the order of $\lambda_c^3$ with each of
the other two neutrinos.


title: A Model of Direct Gauge Mediation

abstract:
  We present a simple model of gauge mediation (GM) which does not have a
messenger sector or gauge singlet fields. The standard model gauge groups
couple directly to the sector which breaks supersymmetry dynamically. This is
the first phenomenologically viable example of this type in the literature.
Despite the direct coupling, the model can preserve perturbative gauge
unification. This is achieved by the inverted hierarchy mechanism which
generates a large scalar expectation value compared to the size of
supersymmetry breaking. There is no dangerous negative contribution to the
squark, slepton masses due to two-loop renormalization group equation. The
potentially non-universal supergravity contribution to the scalar masses can be
suppressed enough to maintain the virtue of the gauge mediation. The model is
completely chiral, and one does not need to forbid mass terms for the messenger
fields by hand. Beyond the simplicity of the model, it possesses cosmologically
desirable features compared to the original models of GM: an improved gravitino
and string moduli cosmology. The Polonyi problem is back unlike in the original
GM models, but is still much less serious than in hidden sector models.


title: Probing mu-term Generation Mechanism in String Models

abstract:
  We give a generic method to select a realistic $\mu$-term generation
mechanism based on the radiative electroweak symmetry breaking scenario and
study which type is hopeful within the framework of string theory. We discuss
effects of the moduli F-term condensation and D-term contribution to soft
scalar masses.


title: The Intrinsic Gluon Component of the Nucleon

abstract:
  Using an intrinsic parton model we estimate the rough shape and size of the
intrinsic gluon component of the nucleon, corresponding to an energy scale $Q$
of the order $\lqcd$. It is nearly as hard in shape as the valence quark, while
its size accounts for a quarter of the nucleon momentum. Both are in
qualitative agreement with the input leading twist gluon distribution assumed
by Gl\"uck, Reya and Vogt at this scale in order to reproduce the observed
distributions at $Q^2 \gsim 1$ GeV$^2$ via perturbative QCD evolution.


title:
Constraints on anomalous gauge couplings from present LEP1 and future
  LEP2, BNL data

abstract:
  We analyze, in a rather general model where anomalous triple gauge couplings
are present, the visible effects in R$_b$ (measured at LEP1), in W pair
production (to be measured at LEP2) and in the muon anomalous magnetic moment
(to be measured at BNL). From the combination of the three experiments a
remarkable improvement on the pure LEP2 constraints is obtained.


title:
A quantitative reanalysis of charmonium suppression in nuclear
  collisions

abstract:
  We present a quantitative description of $J/\psi$ and $\psi^\prime$
suppression in proton-nucleus and nucleus-nucleus collisions at CERN energies.
We use a conventional hadronic framework based on nuclear absorption plus final
state interaction of the $J/\psi$ or $\psi^\prime$ with co-moving hadrons.


title: QCD and Hadronic Interactions: Summary talk for Moriond 97

abstract:
  This talk covers a selection of topics that were discussed at this meeting in
the non-heavy-ion sessions: (a) The high $Q^{2}$ events at HERA and their
theoretical interpretation. (b) The issues of how well we know the predictions
of QCD, with a particular emphasis on resummation. (c) Anomalies in jet
production in association with $W$ bosons at the Tevatron and in dijet
production in deep-inelastic scattering. (d) Diffractive hard scattering.


title: Introduction to Perturbative QCD

abstract:
  This is a written version of two lectures given at the First School on Field
Theory and Gravitation in Vitoria (Brasil) April 15-19, 1997. We discuss the
foundation of QCD as the theory of strong interactions and the perturbative
analysis of e^+e^- annihilation into hadrons. Typical concepts of perturbative
QCD studies, such as collinear singularities, jets, Sudakov form factors, are
explained working out this case.


title: Hadronic sizes and observables in high-energy scattering

abstract:
  The functional dependence of the high-energy observables of total cross
section and slope parameter on the sizes of the colliding hadrons predicted by
the model of the stochastic vacuum and the corresponding relations used in the
geometric model of Povh and H\"ufner are confronted with the experimental data.
The existence of a universal term in the expression for the slope, due purely
to vacuum effects, independent of the energy and of the particular hadronic
system, is investigated. Accounting for the two independent correlation
functions of the QCD vacuum, we improve the simple and consistent description
given by the model of the stochastic vacuum to the high-energy pp and pbar-p
data, with a new determination of parameters of non-perturbative QCD. The
increase of the hadronic radii with the energy accounts for the energy
dependence of the observables.


title: Non-Forward and Unequal Mass Virtual Compton Scattering

abstract:
  We discuss the general operator product expansion of a non-forward unequal
mass virtual compton scattering scattering amplitude. We find that the
expansion now should be done in double moments with new moment variables. There
are in the expansion new sets of leading twist operators which have overall
derivatives, and they mix under renormalization. We compute the evolution
kernels from which the anomalous dimensions for these operators can be
extracted. We also obtain the lowest order Wilson Coefficients. In the high
energy limit we find the explicit form of the dominant contributing anomalous
dimensions and solve the resulting renormalization group equation. We find the
same high energy behavior as indicated by the conventional double leading
logarithmic analysis.


title: Model of the Stochastic Vacuum and QCD Parameters

abstract:
  Accounting for the two independent correlation functions of the QCD vacuum,
we improve the simple and consistent description given by the model of the
stochastic vacuum to the high-energy pp and pbar-p data, with a new
determination of parameters of non-perturbative QCD. The increase of the
hadronic radii with the energy accounts for the energy dependence of the
observables.


title: Condensates and Vacuum Structure of Adjoint QCD_2

abstract:
  We discuss a two dimensional SU(N) Yang-Mills theory coupled to massive
adjoint fermions for different worlds classified by the integer k=0,1,...N-1.
We study the fermion condensate for these unconnected worlds as a function of
the parameter k. We show that the condensate as well as the spectrum of the
theory do depend on this vacuum parameter k. Technically, the value of the
fermion condensate is related to the value of the gluon condensate via the
Operator Product Expansion. We use this to find the leading dependence (in the
limit of a heavy quark) of the fermion condensate on the nontrivial vacuum
angle k. We also determine the gluon condensate of the theory using low-energy
theorems.


title: Detecting and Studying Higgs Bosons

abstract:
  I review the ability of the LHC (large hadron collider), NLC (next linear
lepton collider) and FMC (first muon collider) to detect and study Higgs
bosons, with emphasis on the Higgs bosons of extended Higgs sectors, especially
those of the minimal supersymmetric standard model (MSSM). Particular attention
is given to means for distinguishing the lightest neutral CP-even Higgs boson
of the MSSM from the single Higgs boson of the minimal Standard Model (SM).


title: Jet Production Cross Section with Double Pomeron Exchange

abstract:
  I will discuss hadron-hadron collisions where the final state is
kinematically of the kind associated with double-pomeron-exchange (DPE) and has
large transverse momentum jets. I will show that in addition to the
conventional factorized (FDPE) contribution, there is a non-factorized (NDPE)
contribution which has no pomeron beam jet. Results of calculations from a
simple model of DPE for two-jet total and differential cross sections at
Tevatron energy scales are presented. The NDPE contribution is dominant.


title:
Azimuthal Correlation in Lepton-Hadron Scattering via Charged
  Weak-Current Processes

abstract:
  We consider the azimuthal correlation of the final-state particles in charged
weak-current processes. This correlation provides a test of perturbative
quantum chromodynamics. The azimuthal asymmetry is large in the semi-inclusive
processes in which we identify a final-state hadron, say, a charged pion
compared to that in the inclusive processes in which we do not identify
final-state particles and use only the calorimetric information. In
semi-inclusive processes the azimuthal asymmetry is more conspicuous when the
incident lepton is an antineutrino or a positron than when the incident lepton
is a neutrino or an electron. We analyze all the possible charged weak-current
processes and study the quantitative aspects of each process. We also compare
this result to the ep scattering with a photon exchange.


title: Heavy Higgs: Is the Gauge Symmetry Restored in the Early Universe?

abstract:
  The possibility of symmetry non-restoration at high temperature is explored
in a strongly interacting Higgs system described by an effective Chiral
Lagrangian. Despite a na\"{\i}ve perturbative hint of symmetry non-restoration
when the temperature is increased, non-perturbative methods point towards
symmetry restoration. (Contribution to the XXXIInd Rencontres de Moriond,
"Electroweak Interactions and Unified Theories")


title:
Kinematic Enhancement of Non-Perturbative Corrections to Quarkonium
  Production

abstract:
  In this letter we address issues involved in quarkonium production near the
boundaries of phase space. It is shown that higher-order non-perturbative
contributions are enhanced in this kinematic region and lead to a breakdown of
the non-relativistic (NRQCD) expansion. This breakdown is a consequence of
sensitivity to the kinematics of soft gluon radiation and to the difference
between partonic and hadronic phase space. We show how these large corrections
can be resummed giving the dominant contribution to the cross section. The
resummation leads to the introduction of non-perturbative, universal
distribution functions. We discuss the importance of these shape functions for
several observables, in particular the energy distribution of photo-produced
$J/\psi$ close to the endpoint.


title: What if Charged Current Events at Large Q2 are Observed at HERA ?

abstract:
  An excess of events at large Q2 with a positron in the final state has been
observed at HERA which, if confirmed, would be a signal of new physics. It is
not clear at present if a signal of comparable rate is also seen in the charged
current channel (with an antineutrino in the final state). In this note we
analyse the implications of the presence of such a signal in models of new
physics based on contact terms, leptoquarks and squarks with R-violating
decays. We find that in all cases the most likely possibility is that the
charged current signal is absent. As a consequence if this signal is present
the resulting indications are very selective. In particular for squarks only
charged current events with multi-quark final states are possible with quite
definite predictions on the spectrum of supersymmetric particles.


title: Phenomenology of the BFKL pomeron and Unitarity Corrections at low x

abstract:
  The low $x$ limit of deep inelastic electron proton scattering is considered
using methods of perturbative QCD. In the first part we investigate the
phenomenological consequences of the resummation of leading logarithms in $1/x$
given by the BFKL pomeron. We apply the BFKL pomeron to the inclusive structure
function $F_2$, to the diffractive production of vector mesons at large
momentum transfer, to inclusive photon diffractive dissociation in DIS and to
quark-antiquark production with large transverse momenta in DIS diffractive
dissociation. For the last process we perform extensive numerical calculations
based on the double logarithmic approximation. The BFKL pomeron is known to
violate unitarity. In the second part the first next-to-leading corrections
which have to be taken into account to restore unitarity of the scattering
amplitude are investigated. A compact configuration space representation of the
two to four gluon transition vertex is derived. Conformal symmetry of the
vertex is proven and its relation to a conformal covariant three point function
is established. The important role of the spectral function $\chi_4$ of the
four gluon state is pointed out. We relate this function to the twist expansion
of the four gluon amplitude. Motivated by this relation we develop a method to
perform the twist expansion of the amplitude. Based upon first results of our
analysis we draw conclusions concerning the singularity structure of the
function $\chi_4$.


title:
Do really the seagull terms survive for the electric polarizability of
  the nucleon

abstract:
  The seagull terms for the electric polarizability of the nucleon are shown to
vanish, if one introduces fluctuations around the Skyrmion, and the origin of
the eletric polarizability cannot be attributed to the seagull terms in the
Skyrme model.


title: Power corrections and Landau singularity

abstract:
  In the dispersive approach of Dokshitzer, Marchesini and Webber, standard
power-behaved contributions of infrared origin are described with the notion of
an infrared regular QCD coupling. I argue that their framework suggests the
existence of non-standard contributions, arising from short distances (hence
unrelated to renormalons and the operator product expansion), which appear in
the process of removing the Landau singularity of the perturbative coupling. A
natural definition of an infrared finite perturbative coupling is suggested
within the dispersive method. Implications for the tau hadronic width and the
lattice determination of the gluon condensate, where $O(1/Q^2)$ contributions
can be generated, are pointed out.


title: Gluonic reggeons

abstract:
  Contributions from gluon interactions, which are non-leading in high-energy
semi-hard processes, are studied and represented in terms of reggeon exchanges.
Unlike the leading gluonic reggeon, related to the BFKL pomeron, the
non-leading reggeons are sensitive to the spin and transverse momentum
distributions of scattering partons. There are several gluonic reggeons with
poles in the vicinity of angular momentum $j=0$ contributing to the
perturbative Regge asymptotics of QCD. We extend the high-energy effective
action including sub-leading terms which describe these reggeons and their
interactions with scattering quarks and gluons in the multi-Regge
approximation.


title: Non-Leptonic Weak Decays of B Mesons

abstract:
  We present a detailed study of non-leptonic two-body decays of B mesons based
on a generalized factorization hypothesis. We discuss the structure of
non-factorizable corrections and present arguments in favour of a simple
phenomenological description of their effects. To evaluate the relevant
transition form factors in the factorized decay amplitudes, we use information
extracted from semileptonic decays and incorporate constraints imposed by
heavy-quark symmetry. We discuss tests of the factorization hypothesis and show
how unknown decay constants may be determined from non-leptonic decays. In
particular, we find f_{Ds}=(234+-25) MeV and f_{Ds*}=(271+-33) MeV.


title:
Polarization Measurements and T-Violation in Exclusive Semileptonic B
  Decays

abstract:
  We provide a general analysis of time reversal invariance violation in the
exclusive semileptonic B decays B to D l nu and B to D* l nu. Measurements of
the lepton and D* polarizations can be used to search for and identify
non-standard model sources of T violation. Upper limits are placed on the T-odd
polarization observables in both the supersymmetric R-parity conserving and
R-parity breaking theories, as well as in some non-supersymmetric extensions of
the standard model, including multi-Higgs-doublet models, leptoquark models,
and left-right symmetric models. It is noted that many of these models allow
for large T-violating polarization effects which could be within the reach of
the planned B factories.


title:
A Simple Approximation of the One-Loop Corrected Cross Section for
  $e^+e^-\to W^+W^-$ at LEP 2

abstract:
  Using the SU(2) gauge coupling, $g_{W^\pm} (M^2_{W^\pm})$, at the high-energy
scale of $M_{W^\pm}$, defined by the (theoretical value of the) leptonic
W-width, rather than using the low-energy value, defined via the Fermi
coupling, $G_\mu$, in the Born approximation, and supplementing with Coulomb
corrections and initial state radiation, errors with respect to the exact
one-loop results for the differential cross section of $e^+e^-\to W^+W^-$ are
below 1% at LEP 2 energies at all $W^+W^-$ production angles. A similar
procedure is suggested to incorporate leading bosonic loop effects into
four-fermion production in the fermion-loop scheme. The resulting accuracy
below 1% is sufficient for LEP 2 experiments.


title:
Next-to-Leading-Order Corrections to Momentum Correlations in $Z^0 \to
  b\bar{b}$

abstract:
  We recently completed a calculation of the process $e^+e^- \to Q\bar{Q}+X$,
where Q is a heavy quark, at order $O(\alpha_s^2)$. As a first application of
this calculation we compute the momentum correlations of $b\bar{b}$ pairs at
next-to-leading-order. This quantity is interesting since it may affect the
determination of $R_b$ as measured in $Z^0$ decays. We find that the
next-to-leading corrections are of moderate size, thus confirming the
conclusions that can be drawn from the leading-order calculation.


title:
Onium-Onium scattering at fixed impact parameter: exact equivalence
  between the color dipole model and the BFKL Pomeron

abstract:
  We compute the onium-onium scattering amplitude at fixed impact parameter in
the framework of the perturbative QCD dipole model. Relying on conformal
properties of the dipole cascade and of the elementary dipole-dipole scattering
amplitude, we obtain an exact result for this onium-onium scattering amplitude,
which is proven to be identical to the BFKL result, and which exhibits the
frame invariance of the calculation. The asymptotic expression for this
amplitude and for the dipole distribution in an onium at fixed impact parameter
agree with previous numerical simulations. We show how it is possible to
describe onium-$e^{\pm}$ deep inelastic scattering in the dipole model, relying
on k_T-factorization properties. The elementary scattering amplitudes involved
in the various processes are computed using eikonal techniques.


title: The Pomeron Beyond BFKL

abstract:
  Conformally invariant reggeon interactions derived from $t$-channel unitarity
are discussed and progress towards understanding the ``physical Pomeron'', via
massless quark reggeon interactions, is briefly outlined.


title:
Solving the Bethe-Salpeter equation for bound states of scalar theories
  in Minkowski space

abstract:
  We apply the perturbation theory integral representation (PTIR) to solve for
the bound state Bethe-Salpeter (BS) vertex for an arbitrary scattering kernel,
without the need for any Wick rotation. The results derived are applicable to
any scalar field theory (without derivative coupling). It is shown that solving
directly for the BS vertex, rather than the BS amplitude, has several major
advantages, notably its relative simplicity and superior numerical accuracy. In
order to illustrate the generality of the approach we obtain numerical
solutions using this formalism for a number of scattering kernels, including
cases where the Wick rotation is not possible.


title: Critical Scattering and Two Photon Spectra for a Quark/Meson Plasma

abstract:
  At the Mott transition of a quark/meson plasma, mesons become unbound. This
leads to the effect of critical scattering, which is studied by investigating
photon pair production due to the process $q\bar q\to\gamma\gamma$. This
process can proceed either via direct annihilation or via the formation of a
mesonic resonance. It is shown that the latter channel leads to an enhancement
of photon pairs with invariant mass equal to the thermal pion mass. The size of
this effect measures the time the temperature stays near the Mott temperature
during the evolution. It is particularly pronounced for a first order phase
transition. The $\pi^0\to\gamma\gamma$ decay gives a strong background
contribution and may make the observation of critical scattering in two-photon
spectra of present day heavy ion collision experiments difficult.


title:
Constraints on long-baseline neutrino oscillation probabilities and CP
  asymmetries from neutrino oscillation data

abstract:
  We consider long-baseline neutrino oscillations in the framework of two
schemes with mixing of four massive neutrinos which can accommodate all the
existing indications in favour of neutrino mixing. Within these schemes, we
derive bounds on the oscillation probabilities and the CP-odd
neutrino-antineutrino asymmetries in long-baseline experiments. Using the
results of short-baseline neutrino oscillation experiments, we obtain rather
strong upper bounds on the long-baseline probabilities 1-P(nu_e->nu_e) and
P(nu_mu->nu_e). Nevertheless, the projected sensitivities of the MINOS and
ICARUS experiments are better than our bounds. We also show that there are no
corresponding constraints for nu_mu->nu_mu and nu_mu->nu_tau long-baseline
oscillations and that the CP-odd asymmetry in the latter channel can reach the
maximal value allowed by the unitarity of the mixing matrix. Some schemes with
mixing of three neutrinos are also considered.


title: Strong WW scattering and resonances at LHC

abstract:
  The low energy dynamics of the general strongly interacting symmetry breaking
sector can be easily described using effective chiral Lagrangians. Indeed, the
enhancement in WW scattering at LHC, that would imply the existence of such an
strong interaction, can be described with just two chiral parameters. These
techniques have been shown to reproduce remarkably well the low-energy
pion-pion scattering data, which follows a similar formalism. In this work we
first review the LHC sensitivity to those two chiral parameters (in the hardest
case of non-resonant low-energy WW scattering). Later it is shown how we can
predict the general resonance spectrum of the strongly interacting symmetry
breaking sector. For that purpose, we use the inverse amplitude method which is
also very successful reproducing the lightest hadronic resonances from data in
the low-energy non resonant region. We thus present an study of the regions in
parameter space where one, two or no resonances may appear.


title: Friction Domination with Superconducting Strings

abstract:
  We investigate the evolution of a superconducting string network with
arbitrary, constant string current in the friction dominated regime. In the
absence of an external magnetic field the network always reaches a scaling
solution. However, for string current stronger than a critical value, it is
different than the usual, horizon-scaling of the non-superconducting string
case. In this case the friction domination era never ends. Whilst the
superconducting string network can be much denser than usually assumed, it can
never dominate the universe energy density. It can, however, influence the
cosmic microwave background radiation and the formation of large scale
structure. When embedded in a primordial magnetic field of sufficient strength,
the network never reaches scaling and, thus, eventually dominates the universe
evolution.


title:
Unusual behavior in pbar-p and l-p collisions involving high energy and
  momenum transfer: Z0(W+-) and scalar jets

abstract:
  We show that the axial-vector coupling of Z0(W+-) to quarks, when acting
together with the emission of a hypothetical spin-zero jet-generating quantum
coupled to quarks results in an unusual behavior in certain processes, at high
energy and momentum transfer. This involves an excess jet production at the
subpicobarn level.


title:
Enhanced $b\to sg$ Decay, Inclusive $\eta^\prime$ Production, and the
  Gluon Anomaly

abstract:
  The experimental hint of large $B\to \eta^\prime + X_s$ is linked to the
$b\to s$ penguins via the gluon anomaly. Using running $\alpha_s$ in the
$\eta^\prime$-$g$-$g$ coupling, the standard $b\to sg^*$ penguin alone seems
insufficient, calling for the need of dipole $b\to sg$ at 10% level from new
physics, which could also resolve the ${\cal B}_{s.l.}$ and charm counting
problems. The intereference of standard and new physics contributions may
result in direct CP asymmetries at 10% level, which could be observed soon at B
Factories.


title: Radiative Corrections to the Photon + 1 Jet Rate at LEP

abstract:
  We present the results of a calculation of the rate for the annihilation of
an $e^+e^-$ pair into a jet containing an energetic photon and a single further
jet at order $\alpha \alpha_{s}$. By comparing these results with the existing
data on the photon + 1 jet rate from the ALEPH Collaboration, we make a first
determination of the process independent quark-to-photon fragmentation function
$D_{q \to \gamma}(z,\mu_{F})$ at order $\alpha \alpha_{s}$. We also compare our
prediction for the inclusive photon energy spectrum with the recent OPAL
measurement.


title: Distinguishing gauge-mediated from unified-supergravity spectra

abstract:
  We show that gauge-mediation and unified-supergravity give sufficiently firm
and different predictions for the spectrum of supersymmetric particles to make
it possible to discriminate the two scenarios even if the messenger mass is
close to the unification scale.


title: Dynamical Soft Terms with Unbroken Supersymmetry

abstract:
  We construct a class of simple and calculable theories for the supersymmetry
breaking soft terms. They are based on quantum modified moduli spaces. These
theories do not break supersymmetry in their ground state; instead we postulate
that we live in a supersymmetry breaking plateau of false vacua. We demonstrate
that tunneling from the plateau to the supersymmetric ground state is highly
supressed. At one loop, the plateau develops a local minimum which can be
anywhere between $10^8$ GeV and the grand unification scale. The value of this
minimum is the mass of the messengers of supersymmetry breaking. Primordial
element abundances indicate that the messengers' mass is smaller than $10^{12}$
GeV.


title: Single Top from Technipion Production

abstract:
  We investigate the contribution of technicolor mechanisms to the production
of single top quarks at hadron colliders. Technipions with mass larger than the
top mass will decay predominantly to a top quark plus a bottom antiquark. We
investigate two promising sub-processes: technipion plus W-boson via
gluon-gluon fusion and technipion plus quark production via quark gluon
interaction. The decay chain of technipion to top plus bottom quarks and then
top to W plus bottom yields final states for the two subprocesses with,
respectively, two W's and two bottom quarks and one W, two bottom quarks and a
light quark. We calculate the total cross sections and the $p_{T}$
distributions for these technipion production mechanisms at Tevatron and LHC
energies for a range of technipion masses, starting at 200 GeV. We study the
backgrounds to our processes and the kinematic cuts that enhance the signal to
background ratio and we report event rate estimates for the upgraded Tevatron
and the LHC. Only the LHC has the potential to observe these processes.


title: In Search of SUSY

abstract:
  Electroweak precision tests of the SM and MSSM as well as searches for
Supersymmetric Particles and Higgs bosons at LEP II and their significance
within the MSSM are discussed. Invited talk presented at the EPIPHANY Conf. in
Cracow, Jan. 3-7, 1997.


title: Hard Processes with Spin-Dependent Parton Distributions

abstract:
  To test a possible color-octet contribution of heavy quarkonium productions,
we propose $\psi$'-productions for small-$p_T$ regions, where the color-singlet
$\psi$' state cannot be produced by the gluon-gluon fusion owing to charge
conjugation. We also point out that these processes are very useful to deduce
informations of spin-dependent gluon distributions $\Delta g$.


title: Quarkonium Production at the Tevatron through Soft Colour Interactions

abstract:
  The direct charmonium and bottomonium production rate observed at high-pt in
pp-bar collisions at the Tevatron is factors of ten larger than predictions
based on conventional perturbative QCD. We show that this excess can be
accounted for by our model for soft colour interactions, previously introduced
to describe in a novel way the large rapidity gap events observed at HERA.


title:
The finite temperature real time \hbar^2 corrections in quantum
  mechanics

abstract:
  We study non-perturbative real time correlation functions at finite
temperature. In order to see whether the classical term gives a good
approximation in the high temperature limit T >> \hbar\omega, we consider the
first \hbar^2 quantum corrections. We find that for the simplest non-trivial
case, the quantum mechanical anharmonic oscillator, the classical result is
reliable only for moderately large times: after some time t_* the classical
approximation breaks down even at high temperatures. Moreover, the result for
the first quantum corrections cannot, in general, be reproduced by modifying
the parameters of the classical theory.


title: Coherent neutrino magnetic conversion in crystals

abstract:
  We study coherent enhancement of neutrino electro-magnetic conversion in
crystals. Large coherency length which grows with the neutrino energy makes the
coherent enhancement particularly effective for very small masses. We derive
constraints on the conversion rate which follow from the Fresnel effects in
scattering of neutrinos on atomic chains. We comment on possible applications
of the crystal converter to searches for non-diagonal neutrino magnetic
transitions in the CERN neutrino beam.


title:
The uncertainty in $\alpha_{s}(M_Z^2)$ determined from hadronic tau
  decay measurements

abstract:
  We show that QCD Minkowski observables such as the $e^{+}e^{-}$ R-ratio and
the hadronic tau decay $R_{\tau}$ are completely determined by the effective
charge (EC) beta-function, $\rho(x)$, corresponding to the Euclidean QCD vacuum
polarization Adler D-function, together with the next-to-leading order (NLO)
perturbative coefficient of D. An efficient numerical algorithm is given for
evaluating R, $R_{\tau}$ from a weighted contour integration of
$D(se^{i\theta})$ around a circle in the complex squared energy s-plane, with
$\rho(x)$ used to evolve in s around the contour. The EC beta-function can be
truncated at next-to-NLO (NNLO) using the known exact perturbative calculation
or the uncalculated N^3 LO and higher terms can be approximated by the portion
containing the highest power of b, the first QCD beta-function coefficient. The
difference between the R, $R_{\tau}$ constructed using the NNLO and "leading-b"
resummed versions of $\rho(x)$ provides an estimate of the uncertainty due to
the uncalculated higher order corrections. Simple numerical parametrizations
are given to facilitate these fits. For $R_{\tau}$ we estimate an uncertainty
$\delta\alpha_{s}(m_{\tau}^{2})\simeq0.01$, corresponding to
$\delta\alpha_{s}(M_{Z}^{2})\simeq0.002$. This encouragingly small uncertainty
is much less than rather pessimistic estimates by other authors based on
analogous all-orders resummations, which we demonstrate to be extremely
dependent on the chosen renormalization scheme, and hence misleading.


title:
Cold Dark Matter Candidate in a Class of Supersymmetric Models with an
  Extra U(1)

abstract:
  In supersymmetric models whose gauge group includes an additional U(1) factor
at the TeV scale, broken by the VEV of an standard model singlet S, the
parameter space can accommodate a very light neutralino not ruled out
experimentally. This higgsino-like fermion, stable if R-parity is conserved,
can make a good cold dark matter candidate. We examine the thermal relic
density of this particle and discuss the prospects for its direct detection if
it forms part of our galactic halo.


title: pi_0 --> gamma gamma and the axial anomaly at non zero temperature

abstract:
  In vacuum, in the chiral limit the coupling of a pion to two on-shell photons
is directly related to the coefficient of the axial anomaly in QED. This
relationship is lost at any nonzero temperature. Explicit calculations show
that the coupling decreases with temperature and vanishes at Tc, the
temperature of chiral symmetry restoration.


title: Purely-Nonperturbative Composite Operators and Parton Distributions

abstract:
  A class of purely-nonperturbative (PNP) composite operators is defined in
Quantum Chromodynamics, which is perturbative scheme and scale independent and
are useful to describe the internal structure of a strong interacting system.
The operator product expansion in terms of the new operators cleanly separates
the perturbative and nonperturbative physics without introducing any
factorization scale. A number of PNP observables of the nucleon is briefly
discussed including the PNP parton distributions. In particular, the fraction
of the nucleon momentum carried by the purely-nonperturbative gluons is found
to be around 16%.


title: Renormalons and 1/Q^2 Corrections

abstract:
  We argue that the appearance of the Landau pole in the running coupling of
QCD introduces 1/Q^2 power corrections in current correlation functions. These
terms are not accounted for by the standard operator product expansion and is
the price to be paid for the lack of a unique definition of the running
coupling at the 1/Q^2 level. We review also possible phenomenological
implications of the 1/Q^2 terms in an alternative language of the ultraviolet
renormalon.


title: The Banks-Zaks Expansion and "Freezing" in Perturbative QCD

abstract:
  The recent calculation of the four-loop beta function in QCD provides further
evidence that the Banks-Zaks expansion in 16half-n_f is sufficiently well
behaved to be useful even for n_f=2 light flavours. This expansion inherently
predicts "freezing" of the QCD couplant at low energies as a perturbative
effect. We consider the e+e- and Bjorken-sum-rule cases as examples.


title: CP Violation in Quasi-inclusive $B\to K^{(*)} X$ Decays

abstract:
  We consider the possibility of observing CP violation in quasi-inclusive
decays of the type $B^-\to K^- X$, $B^-\to K^{*-} X$, $\bar B^0\to K^- X$ and
$\bar B^0\to K^{*-} X$, where $X$ does not contain strange quarks. We present
estimates of rates and asymmetries for these decays in the Standard Model and
comment on the experimental feasibility of observing CP violation in these
decays at future $B$ factories. We find the rate asymmetries can be quite
sizeable.


title: Developing Transport Theory to Study the Chiral Phase Transition

abstract:
  Chiral symmetry is an important aspect of QCD. Modelling this via the
Nambu-Jona-Lasinio model, we construct a complete relativistic transport theory
for quarks and mesons. The collision integral is analysed in a systematic 1/N_c
approximation, and via this, it is shown that one can naturally incorporate
mesonic degrees of freedom plus the hadronization of quarks and antiquarks into
mesons into the field theoretic description. Time permitting, some simulation
results, on the level of the Vlasov equation and also including collisions in a
relaxation time approach, will be discussed.


title:
Leading log radiative corrections to deep inelastic production of heavy
  quarks

abstract:
  O(\alpha) QED radiative corrections to neutral current deep inelastic
production of heavy quarks are calculated in the leading log approximation and
compared with the corresponding corrections assuming a massless charm parton.
Besides the inclusive case, corrections to the semi-inclusive d^3\sigma/dx dy
dz and the effect of z-cuts are studied. In the latter case, the massless
corrections differ from the correct massive radiative corrections to deep
inelastic heavy quark production by about 40%-10% for 0.2\lesssim z \lesssim
0.5.


title:
Chiral two-loop pion-pion scattering parameters from crossing-symmetric
  constraints

abstract:
  Constraints on the parameters in the one- and two-loop pion-pion scattering
amplitudes of standard chiral perturbation theory are obtained from explicitly
crossing-symmetric sum rules. These constraints are based on a matching of the
chiral amplitudes and the physical amplitudes at the symmetry point of the
Mandelstam plane. The integrals over absorptive parts appearing in the sum
rules are decomposed into crossing-symmetric low- and high-energy components
and the chiral parameters are finally related to high-energy absorptive parts.
A first application uses a simple model of these absorptive parts. The
sensitivity of the results to the choice of the energy separating high and low
energies is examined with care. Weak dependence on this energy is obtained as
long as it stays below ~560 MeV. Reliable predictions are obtained for three
two-loop parameters.


title:
Slope of the Isgur-Wise function in the heavy mass limit of quark models
  \`a la Bakamjian-Thomas

abstract:
  The slope of the Isgur-Wise function for ground state mesons is evaluated for
the heavy mass limit of quark models \`a la Bakamjian-Thomas, which has been
previously discussed by us in general terms. A full calculation in various
spectroscopic models with relativistic kinetic energy gives a rather stable
result $\rho^2 \approx 1$, much lower than previous estimates. Attention is
paid to a careful comparison of this result with the ones of QCD fundamental
methods (lattice QCD, QCD sum rules) and with experimental data.


title: Mass generation of the lepton sector

abstract:
  We discuss the necessity of a right-handed Weyl neutrino due to the
vector-like phenomenon of the regularized Standard Model. It is shown that this
right-handed neutrino is decoupled from low energies as a free particle, and
Dirac neutrino masses are very small. We suggest gauge-invariant couplings
between down quarks and charged leptons so that charged leptons acquire masses
without extra Goldstone modes. By examining Schwinger-Dyson equations for
lepton self-energy functions, we show that the neutrinos get their Dirac masses
via explicit symmetry breakings that attribute to the mixing between neutrinos
and charged leptons. An analysis of these Dyson equations gives the four
relationships between inter-generation mixing angles and lepton masses.


title:
Possible Asymmetry of Particle Distribution Around Axes of Hard Jets in
  Ultrarelativistic Heavy Ion Collisions

abstract:
  We discuss a possible new manifestation of the formation of an initial
nonequilibrium flux tube stage in high energy heavy ion collisions. It is shown
that a strong asymmetry in particle distributions around axes of
hard-transverse jets takes place due to a large difference between longitudinal
and transverse forces acting on the hardly scattered quarks or gluons crossing
the flux tubes.


title:
Long distance $c \to u \gamma$ effects in weak radiative decays of
  D-mesons

abstract:
  We present a detailed analysis of the $D \to V \gamma $ transitions, using a
model which combines heavy quark effective theory and the chiral Lagrangian
approach and includes symmetry breaking. We notice that in addition to the
previously considered s - channel annihilation and t - channel W - exchange,
there is a long distance penguin - like $ c \to u \gamma$ contribution in the t
- channel of Cabibbo - suppressed modes. Its magnitude is determined by the
size of symmetry breaking which we calculate with a vector dominance approach.
Although smaller in magnitude, the penguin - like contribution would lead to
sizeable effects in case of cancellations among the other contributions to the
amplitude. Thus, it may invalidate suggested tests for beyond the standard
model effects in these decays. We also indicate the range of expectations for
the branching ratios of various $D \to V \gamma$ modes.


title: $\beta$-functions in large-$N_f$ supersymmetric gauge theories

abstract:
  We present calculations of the leading and $O(1/N_f)$ terms in a large-$N_f$
expansion of the $\beta$-functions and anomalous dimensions for various
supersymmetric gauge theories, including supersymmetric QCD. In the case of
supersymmetric QCD, we show that our $O(1/N_f)$ approximation displays an
infra-red fixed point in the conformal window $3N_c/2 < N_f < 3N_c$.


title:
$\Psi'/\Psi $ ratio in Nucleus-Nucleus Collisions : a Measure for the
  Chiral Symmetry Restoration Temperature ?

abstract:
  We argue that a decrease of the chiral scalar meson mass is responsible for
re-creation of $\Psi'$ from $J/\Psi$ in ultrarelativistic nucleus-nucleus
collisions. This causes the charmonium yields to freeze out at temperatures
close to the chiral symmetry restoration temperature $T_c$. As a result
$\Psi'/\Psi$ may serve as a thermometer for $T_c$ itself. Results in a detailed
reaction model support the conjecture. They show good agreement with recent
data of NA38 and NA50 for $J/\Psi$ and $\Psi'$ production in S on U and Pb on
Pb collisions.


title: Analytic constraints from electroweak symmetry breaking in the MSSM

abstract:
  We report on how a straightforward (albeit technically involved) analytic
study of the 1-loop effective potential in the Minimal Supersymmetric Standard
Model, modifies the usual electroweak symmetry breaking conditions involving
$\tan \beta$ and the other free parameters of the model. The study implies new
constraints which (in contrast with the existing ones like $1 \leq \tan \beta
\leq m_t/m_b$) are fully model-independent and exclude more restrictively a
region around $\tan \beta \sim 1$. Further results of this study will be only
touched upon here.


title: Ruling out a critical density baryonic universe

abstract:
  It has been suggested by Bartlett and Hall that our universe may have the
critical density in baryons by virtue of specific interactions with a `shadow'
world. We show that this possibility is severely constrained by primordial
nucleosynthesis, stellar evolution and the thermalization of the cosmic
microwave background. In particular, recent observations of small angular-scale
anisotropy in the cosmic microwave background conclusively rule out all such
baryon-dominated cosmologies.


title: phi-Meson Mass Modification in Heavy-Ion Collisions

abstract:
  We recently presented a method of analyzing invariant-mass spectra of kaon
pairs resulting from decay of $\phi$ mesons produced in high-energy heavy-ion
collisions. It can be used to extract the shifts in the mass and the width
($\Delta M$ and $\Delta \Gamma$) of the $\phi$ mesons when they are inside the
dense matter formed in these collisions. We have now performed a Monte-Carlo
simulation of this process. We illustrate our method with the help of available
preliminary data. Extracted value of $\Delta M$ is significantly larger than
that obtained with an earlier method. Our results are consistent with the
experimentally observed $p_T$ dependence of the mass shift.


title:
Six-Fermion Calculation of Intermediate-mass Higgs Boson Production at
  Future $e^+ e^-$ Colliders

abstract:
  The production of an intermediate-mass Higgs boson in processes of the kind
$e^+ e^- \to 6$ fermions at the energies of future linear colliders is studied.
The recently developed and fully automatic algorithm/code ALPHA is used to
compute the tree-level scattering amplitudes for the reactions $e^+ e^- \to
\mu^+ \mu^- \tau^- \bar\nu_{\tau} u \bar d, \mu^+ \mu^- e^- \bar\nu_{e} u \bar
d$. The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV,
properly adapted to 6-fermion production, in order to provide realistic
results, both in the form of cross sections and event samples at the partonic
level. Phenomenological results, that incorporate the effects of initial-state
radiation and beamstrahlung, are shown and commented, emphasizing the
potentials of full six-fermion calculations for precise background evaluation
as well as for detailed studies of the fundamental properties of the Higgs
particle.


title:
Excited pions, rho- and omega-mesons and their decays in a chiral SU(2)
  x SU(2) Lagrangian

abstract:
  A chiral SU(2) x SU(2) Lagrangian containing, besides the usual meson fields,
their first radial excitations is considered. The Lagrangian is derived by
bosonization of the Nambu-Jona-Lasinio quark model with separable non-local
interactions, with form factors corresponding to 3-dimensional ground and
excited state wave functions. The spontaneous breaking of chiral symmetry is
governed by the NJL gap equation. The first radial excitations of the pions,
rho-and omega-mesons are described with the help of two form factors. The weak
decay constant F_pi' is calculated. The values for the decay widths of the
processes rho -> 2 pi, pi' -> rho pi, rho' -> 2 pi, rho' -> omega pi and omega'
-> rho pi are obtained in agreement with the experimental data.


title: A Dynamical Scheme for a Large CP-Violating Phase

abstract:
  A dynamical scheme where the third generation of quarks plays a distinctive
role is implemented. New interactions with a $\theta$ term induce the breaking
of the electroweak symmetry and the top-bottom mass splitting. A large
CP-violating phase naturally follows from the latter.


title: The polarized Drell-Yan process at O(\alpha_s)

abstract:
  The results of a recent calculation of the QCD corrections to the polarized
Drell-Yan process are summarized. Some implications for the production of
vector bosons at RHIC are discussed.


title: QCD Effects in Higgs Physics

abstract:
  Higgs boson production at the LHC within the Standard Model and its minimal
supersymmetric extension is reviewed. The predictions for decay rates and
production cross sections are updated by choosing the present value of the top
quark mass and recent parton density sets. Moreover, all relevant higher order
corrections, some of which have been obtained only recently, are included in a
consistent way.


title:
The search for new physics by the measurement of the 4-jet cross section
  at LHC and FNAL

abstract:
  We investigate the possibility to look for new physics by the measurement of
the 4-jet cross section at LHC and FNAL. In particular, we consider the model
with scalar colour octet and the supersymmetric model with R-parity violation.
In both models pair produced new particles decay into 2 jets thus leading to
4-jet events. Therefore, the measurement of the distributions of 4-jet
differential cross section on the invariant dijet masses allows to look for new
physics. The main background comes from standard QCD 4-jet events. We find that
at LHC it would be possible to discover scalar colour particles with masses up
to 900 Gev and for FNAL the corresponding bound is 175 Gev.


title: Solutions to Solar Neutrino Anomaly

abstract:
  We present an updated analysis of astrophysical solutions, two-flavor MSW
solutions, and vacuum oscillation solutions to the solar neutrino anomaly. The
recent results of each of the five solar neutrino experiments are incorporated,
including both the zenith angle (day-night) and spectral information from the
Kamiokande experiment, and the preliminary Super-Kamiokande results. New
theoretical developments include the use of the most recent
Bahcall-Pinsonneault flux predictions (and uncertainties) and density and
production profiles, the radiative corrections to the neutrino-electron
scattering cross section, and new constraints on the Ga absorption cross
section inferred from the gallium source experiments. From a model independent
analysis, arbitrary astrophysical solutions are excluded at more that 98% C.L.
even if one ignores any one of the three classes of experiment, relaxes the
luminosity constraint, or allows more suppression of the 7Be than 8B flux. The
data is well described by large and small mixing angle two-flavor MSW
conversions, MSW conversions into a sterile neutrino with small mixing, or
vacuum oscillations. We also present MSW fits for nonstandard solar models
parameterized by an arbitrary solar core temperature or arbitrary 8B flux.


title: Gauge Invariant Higgs mass bounds from the Physical Effective Potential

abstract:
  We study a simplified version of the Standard Electroweak Model and introduce
the concept of the physical gauge invariant effective potential in terms of
matrix elements of the Hamiltonian in physical states. This procedure allows an
unambiguous identification of the symmetry breaking order parameter and the
resulting effective potential as the energy in a constrained state. We
explicitly compute the physical effective potential at one loop order and
improve it using the RG. This construction allows us to extract a reliable,
gauge invariant bound on the Higgs mass by unambiguously obtaining the scale at
which new physics should emerge to preclude vacuum instability. Comparison is
made with popular gauge fixing procedures and an ``error'' estimate is provided
between the Landau gauge fixed and the gauge invariant results.


title: Flavor-changing Top Quark Decays In R-Parity Violating SUSY

abstract:
  The flavor changing top quark decays t -> cV (V=Z,photon,gluon) induced by
R-parity-violating couplings in the minimal supersymmetric standard model
(MSSM) are evaluated. We find that the decays t -> cV can be significantly
enhanced relative to those in the R-parity conserving SUSY model. Our results
show that the top quark FCNC decay can be as large as Br(t->cg)=10^-3,
Br(t->cZ)=10^-4 and Br(t-> c\gamma)= 10^-5, which may be observable at the
upgraded Tevatron and/or the LHC.


title:
The Isentropic Equilibrium Deconfining Phase Transition in the Extended
  Bag Model

abstract:
  By using an Ansatz for the pressure (measured in terms of the bag constant)
of the hadronic gas in equilibrium, we have formulated a new bag-type model for
the phase transition, i. e. the extended bag model. This allows one to take
into account the nonperturbative vacuum effects from both sides of the
equilibrium condition. We have explicitly shown that our model automatically
provides an isentropic equilibrium deconfining phase transition from the
quark-gluon plasma phase to the hadronic gas phase with a temperature and
chemical potential dependent bag pressure at the phase boundary. This makes it
possible to regulate the total entropy and baryon number in both phases, i. e.
the flow of the specific entropy per baryon across the phase boundary. We have
also determined the functional form of the temperature and chemical potential
dependence of the bag pressure outside the phase boundary.


title:
Order alphas**2 Contributions to the Fragmentation Functions in e+ e-
  Annihilation

abstract:
  We present the higher order QCD corrections to the fragmentation functions
and the corresponding cross sections.


title:
Next-to-Leading Order QCD Analysis of Polarized Deep Inelastic
  Scattering Data

abstract:
  We present a Next-to-Leading order perturbative QCD analysis of world data on
the spin dependent structure functions $g_1^p, g_1^n$, and $g_1^d$, including
the new experimental information on the $Q^2$ dependence of $g_1^n$. Careful
attention is paid to the experimental and theoretical uncertainties. The data
constrain the first moments of the polarized valence quark distributions, but
only qualitatively constrain the polarized sea quark and gluon distributions.
The NLO results are used to determine the $Q^2$ dependence of the ratio
$g_1/F_1$ and evolve the experimental data to a constant $Q^2 = 5 GeV^2$. We
determine the first moments of the polarized structure functions of the proton
and neutron and find agreement with the Bjorken sum rule.


title:
QCD Corrections to $b\to s\gamma\gamma$ and Exclusive $B_s\to
  \gamma\gamma$ Decay

abstract:
  The short distance QCD corrections to $b\to s\gamma \gamma$ are calculated in
the leading logarithmic approximation. The equivalence of operator basis
reduction for S-matrix elements by using the equations of motion or by proving
a low energy theorem is discussed. We apply the above results to the exclusive
$B_s\to \gamma\gamma$ decay. The branching ratio of this decay is found to be
$5\times 10^{-7}$ in the Standard Model. We also found that QCD corrections
modify considerably the ratio between CP-even and CP-odd two-photon amplitudes.


title:
Spectra of Exclusive Semi-Leptonic Decays of B-meson in the Covariant
  Oscillator Quark Model

abstract:
  The spectra and form factors of exclusive semi-leptonic decays of B-meson are
analyzed, taking account of confined effects of quarks by the Covariant
Oscillator Quark Model. The predicted B --> (D*,D)l nubar_l spectra with the
conventional value of V_cb are fit well to the high-precision experiment. It is
also shown the values of V_cb and V_ub obtained through decay widths for the B
--> (D,D*,rho)l nubar_l processes are consistent with the presently accepted
ones.


title: Structure of Resonance in Preheating after Inflation

abstract:
  We consider preheating in the theory $1/4 \lambda \phi^4 + 1/2
g^2\phi^2\chi^2 $, where the classical oscillating inflaton field $\phi$ decays
into $\chi$-particles and $\phi$-particles. The parametric resonance which
leads to particle production in this conformally invariant theory is described
by the Lame equation. It significantly differs from the resonance in the theory
with a quadratic potential. The structure of the resonance depends in a rather
nontrivial way on the parameter $g^2/\lambda$. We construct the
stability/instability chart in this theory for arbitrary $g^2/\lambda$. We give
simple analytic solutions describing the resonance in the limiting cases
$g^2/\lambda\ll 1$ and $g^2/\lambda \gg 1$, and in the theory with
$g^2=3\lambda$, and with $g^2 =\lambda$. From the point of view of parametric
resonance for $\chi$, the theories with $g^2=3\lambda$ and with $g^2 =\lambda$
have the same structure, respectively, as the theory $1/4 \lambda \phi^4$, and
the theory $\lambda /(4 N) (\phi^2_i)^2$ of an N-component scalar field
$\phi_i$ in the limit $N \to \infty$. We show that in some of the conformally
invariant theories such as the simplest model $1/4 \lambda\phi^4$, the
resonance can be terminated by the backreaction of produced particles long
before $<\chi^2>$ or $<\phi^2 >$ become of the order $\phi^2$. We analyze the
changes in the theory of reheating in this model which appear if the inflaton
field has a small mass.


title: Dynamical Inflation and Unification Scale on Quantum Moduli Spaces

abstract:
  We show that simple strongly coupled supersymmetric gauge theories with
quantum moduli spaces can naturally lead to hybrid inflation. These theories
contain no input dimensionful or small parameters. The effective superpotential
is linear in the inflaton field; this ensures that supergravity corrections do
not spoil the slow roll conditions for inflation. We construct a simple theory
in which the classical moduli space exhibits neither GUT-symmetry-breaking nor
inflation whereas its quantum modification exhibits both. As a result, the
dynamical origin and scales of inflation and grand unification coincide.


title:
Electron-positron annihilation into Dirac magnetic monopole and
  antimonopole: the string ambiguity and the discrete symmetries

abstract:
  We address the problem of string arbitrariness in the quantum field theory of
Dirac magnetic monopoles. Different prescriptions are shown to yield different
physical results. The constraints due to the discrete symmetries (C and P) are
derived for the process of electron- positron annihilation into the
monopole-antimonopole pair. In the case of the annihilation through the
one-photon channel, the production of spin 0 monopoles is absolutely forbidden;
spin 1/2 monopole and antimonopole should have the same helicities (or,
equivalently, the monopole-antimonopole state should be p-wave $^1P_1$).


title:
Factorization of the charge correlation function in $B^0\bar B^0$
  oscillations

abstract:
  Extraction of the mass difference $\Delta m$ from $B^0\bar B^0$ oscillations
involves tagging of bottom flavour at production and at decay. We show that the
asymmetry between the unmixed and mixed events factorizes into two parts, one
depending on the production-tag and the other on the decay-tag.


title:
Pontecorvo neutrino-antineutrino oscillations: theory and experimental
  limits

abstract:
  We study Pontecorvo neutrino-antineutrino oscillations both in vacuum and in
matter within a field theoretic approach, showing that this phenomenon can
occur only if neutrinos have a Dirac-Majorana mass term. We find that matter
effects suppress these oscillations and cannot explain the solar neutrino
problem. On the contrary, a vacuum neutrino-antineutrino oscillations solution
to this problem exists. We analyze this solution and available data from
laboratory experiments giving stringent limits on $\nu_e$ and $\nu_{\mu}$
Majorana masses.


title:
QCD Sum Rules for the Isospin-Breaking Axial Correlator with Correct
  Chiral Behavior

abstract:
  We revisit the QCD sum-rule treatment of the isospin-breaking axial
correlator in light of the recent claim that a previous treatment produced
results incompatible with known chiral constraints. The source of the error in
the previous analysis is identified, and a corrected version of the sum-rule
treatment obtained. It is then shown that, using input from chiral perturbation
theory, one may use the resulting sum rule to extract information on the
leading chiral behavior of isospin-breaking parameters associated with the
coupling of excited pseudoscalar resonances to the axial currents. A rather
accurate extraction is possible for the case of the eta'. Demanding stability
of the sum-rule analysis also allows us to improve the upper bound on the
fourth-order low-energy constant, L_7.


title: HERA Physics - an overview of experimental and theoretical results

abstract:
  In this talk I review the low x QCD experimental results from HERA and their
theoretical underpinnings. In particular, I discuss the structure function
$F_2$, large rapidity gap events, pomeron structure functions and $J/\psi$
production.


title:
Order 1/N corrections to the time-dependent Hartree approximation for a
  system of N+1 oscillators

abstract:
  We solve numerically to order 1/N the time evolution of a quantum dynamical
system of N oscillators of mass m coupled quadratically to a massless dynamic
variable. We use Schwinger's closed time path (CTP) formalism to derive the
equations. We compare two methods which differ by terms of order 1/N^2. The
first method is a direct perturbation theory in 1/N using the path integral.
The second solves exactly the theory defined by the effective action to order
1/N. We compare the results of both methods as a function of N. At N=1, where
we expect the expansion to be quite innacurate, we compare our results to an
exact numerical solution of the Schroedinger equation. In this case we find
that when the two methods disagree they also diverge from the exact answer. We
also find at N=1 that the 1/N corrected evolutions track the exact answer for
the expectation values much longer than the mean field (N= \infty) result.


title: Chiral symmetry and the spectrum of the QCD Dirac operator

abstract:
  According to the Banks-Casher formula the chiral order parameter is directly
related to the spectrum of the Dirac operator. In this lecture, we will argue
that some properties of the Dirac spectrum are universal and can be obtained
from a random matrix theory with the global symmetries of the QCD partition
function. In particular, this is true for the spectrum near zero on the scale
of a typical level spacing. Alternatively, the chiral order parameter can be
characterized by the zeros of the partition function. We will analyze such
zeros for a random matrix model at nonzero chemical potential.


title: Removing Discrete Ambiguities in CP Asymmetry Measurements

abstract:
  We discuss methods to resolve the ambiguities in CP violating phase angles
$\phi$ that are left when a measurement of $\sin 2 \phi$ is made. We show what
knowledge of hadronic quantities will be needed to fully resolve all such
ambiguities.


title: Inflaton Decay and Heavy Particle Production with Negative Coupling

abstract:
  We study the decay of the inflaton in a renormalizable two scalar theory.
Since the dynamics of the system is dominated by states with large occupation
numbers which admit a semiclassical description, the decay can be studied by
solving the classical equations of motion on the lattice. Of particular
interest is the case when the cross-coupling between the inflaton and the
second scalar field is negative, which is naturally allowed in many realistic
models. While the inflaton decays via parametric resonance in the positive
coupling case we find that for negative coupling there is a new mechanism of
particle production which we call negative coupling instability. Due to this
new mechanism the variances of the fields grow significantly larger before the
production is shut off by the backreaction of the created particles. We also
find that heavy particles are produced much more efficiently with negative
coupling, which is of prime importance for GUT baryogenesis. Using a simple toy
model for baryogenesis and the results of our lattice simulations we show that
for natural values of the cross-coupling enough 10^{14}GeV bosons are created
to produce a baryon to entropy ratio consistent with observation. For positive
coupling the value of the cross-coupling required to produce such massive
particles is unnaturally large. In addition to our numerical results we obtain
analytical estimates for the maximum variances of the fields in an expanding
universe for all cases of interest in our model.


title: Towards Isolation of New Physics in B^0_s-\bar{B}^0_s Mixing

abstract:
  In many extensions of the standard model, new physics is possible to
contribute significantly to B^0_s-\bar{B}^0_s mixing. We show that the effect
of new physics, both its phase information and its magnitude, can be isolated
from measurements of CP asymmetries in the semileptonic B_s transitions and in
some nonleptonic B_s decays into hadronic CP eigenstates. We also find that the
rates of CP-forbidden decays at the \Upsilon (5S) resonance are not suppressed
by the large B_s mass difference, thus they can be used to extract the
CP-violating phase of new physics in either B^0_s-\bar{B}^0_s or K^0-\bar{K}^0
mixing.


title: Chargino Production at an e-e- Collider

abstract:
  The chargino pair production in $e^-e^-$ collisions with their subsequent
decays are considered within SUSY models with R-parity violation and with
lepton number non-conservation. The production process ($\sqrt{s}=1$ TeV) is
predicted to be large in a wide range of both sneutrino and chargino masses.
The influence of all virtual sneutrino states and their mixings with electrons
are taken into account. Some specific situations are pointed out when
significant suppressions of the cross section can take place. The chargino
decays are discussed for either the chargino as LSP or the chargino as heavier
sparticle. In both cases unique signals are possible with up to six charged
fermions and without missing energy.


title: Photons, dileptons and hard thermal loops

abstract:
  The production rate of soft real photons or soft lepton pairs by a hot QCD
plasma is dominated by strong collinear divergences. As a consequence, it
appears that the effective theory based on the resummation of hard thermal
loops fails to handle properly these light-cone sensitive processes since some
formally higher order diagrams are in reality the dominant ones.


title: Phase transitions precipitated by solitosynthesis

abstract:
  Solitosynthesis of Q-balls in the false vacuum can result in a phase
transition of a new kind. Formation and subsequent growth of Q-balls via the
charge accretion proceeds until the solitons reach a critical charge, at which
point it becomes energetically favorable for the Q-ball interior to expand
filling space with the true vacuum phase. Solitosynthesis can destabilize a
false vacuum even when the tunneling rate is negligible. In models with
low-energy supersymmetry, where the Q-balls associated with baryon and lepton
number conservation are generically present, solitosynthesis can precipitate
transitions between the vacua with different VEV's of squarks and sleptons.


title: On the Possibilities of Distinguishing Majorana from Dirac Neutrinos

abstract:
  Cross sections involving massive Dirac or Majorana neutrinos usually differ
only by terms which are suppressed by the smallness of the neutrino mass. The
process $e^+e^-\to\nu\nu$, however, is an example in which the two differential
cross sections are quite distinct even in the limit $m_\nu\to 0$ as long as
$m_\nu\not=0$. I discuss the cause of this phenomenon and comment on strategies
to identify processes with quite different Majorana and Dirac neutrino signals.


title: Hyperfine Interactions in Charm and Bottom Systems

abstract:
  Hyperfine interactions in the light meson and baryon sectors are generalized
to the charm and bottom systems. It is pointed out that an attempt to increase
the value of the wave function at the origin to account for the unusual ratio
of $\Lambda_{b}$ to the $B^0$ lifetimes could spoil the good agreement among
the baryon and meson hyperfine mass-splitting. Including spin effects and
taking phase space differences into account we predict that the decay rate of
the $\Lambda_{b}$ can be increased relative to that of the $B^0$ meson by about
7%.


title: Determination of Scalar Meson Masses in QCD-inspired Quark Models

abstract:
  We compare two QCD-inspired quark models with four-fermion interaction,
without and with the remnant coupling to low-energy gluons, in the regime of
dynamical chiral symmetry breaking (DCSB). The first one, the
Nambu-Jona-Lasinio (NJL) model ensures the factorization of scalar and
pseudoscalar meson poles in correlators, the well-known Nambu relation between
the scalar meson mass and the dynamical quark mass, $m_{\sigma} = 2 m_{dyn}$,
and the residual chiral symmetry in coupling constants characteristic for the
linear $\sigma$-model. The second one, the Gauged NJL model, happens to be
qualitatively different from the NJL model, namely, the Nambu relation is not
valid and the factorization of light meson poles does not entail the residual
chiral symmetry, i.e. it does not result in a linear $\sigma$-model. The more
complicated DCSB pattern in the GNJL model is fully explained in terms of
excited meson states with the same quantum numbers. The asymptotic restrictions
on parameters of scalar and pseudoscalar meson states are derived from the
requirement of chiral symmetry restoration at high energies.


title:
Flavor Changing Transitions and the Top Quark in a Two Higgs Doublets
  Model; Application to e^+e^- --> t bar-c nu_e bar-nu_e, t bar -c e^+ e^-, t
  bar-c Z, t --> cW^+W^- and t --> cZZ

abstract:
  Extension of the SM with one extra Higgs doublet may give rise to
flavor-changing-scalar coupling of a neutral Higgs to a pair of top-charm
quarks. This coupling gives rise to a large tree-level effective W^+W^-;ZZ -
Higgs - t bar-c interaction. We find that the reactions e^+e^- --> t bar-c nu_e
bar-nu_e, t bar-c e^+e^-, t bar-c Z and the two rare top decays t --> cW^+W^-,
t --> cZZ are very sensitive probes of such an effective interaction. The most
promising ones, e^+e^- --> t bar-c nu_e bar-nu_e, t bar-c e^+e^-, may yield
several hundreds and up to thousands of such events at the Next Linear Collider
with a center of mass energy of sqrt{s}=0.5-2 TeV if the mass of the light
neutral Higgs is a few hundred GeV. We also find that the rare decays t -->
cW^+W^- and t --> cZZ may be accessible in the LHC if the mass of the light
neutral Higgs lies in the narrow window 150 GeV < m_h < 200 GeV.


title: Minimal SO(10) Unification

abstract:
  It is shown that the doublet-triplet splitting problem can be solved in
SO(10) using the Dimopoulos-Wilczek mechanism with a very economical Higgs
content and simple structure. Only one adjoint Higgs field is required,
together with spinor and vector fields. The successful SUSY GUT prediction of
gauge coupling unification is preserved. Higgsino-mediated proton decay can be
suppressed below (but not far below) present limits without fine-tuning.


title: Birefringence and Dichroism of the QED Vacuum

abstract:
  We use an analytic form for the Heisenberg-Euler Lagrangian to calculate the
birefringent and dichroic properties of the vacuum for arbitrarily strong
wrenchless fields.
  PACS : 12.20.Ds, 42.25.Lc 97.60.Jd, 98.70.Rz


title: QED One-loop Corrections to a Macroscopic Magnetic Dipole

abstract:
  We consider the field equations of a static magnetic field including one-loop
QED corrections, and calculate the corrections to the field of a magnetic
dipole.
  PACS: 12.20.Ds, 97.60.Jd, 97.60.Gb


title: CP Violation in Neutral Kaon Decays

abstract:
  A brief review of the theoretical status of CP violation in decays of neutral
kaons is presented. We focus on three important topics: $\varepsilon$,
$\varepsilon'/\varepsilon$ and $K_L\to\pi^0\nu\bar\nu$.


title: New Physics from HERA?

abstract:
  The H1 and ZEUS experiments at the HERA $e^\pm p$ collider at Hamburg have
recently reported some anomalous hard-scattering events, which could be
indicative of new physics beyond the standard model. I have tried to discuss in
a nonspecialist language the significance of this result for particle physics
along with its interpretation in terms of the currently popular extensions of
the standard model.


title:
Some Advantages of SUSY SU(4) x SU(2)_L x SU(2)_R Model in String
  Derived SO(10) GUTs

abstract:
  A D-parity violated SUSY SU(4) x SU(2) _ L x SU(2)_R gauge model with the
Higgs sector 2{(4,1,2)+(4-bar,1, 2)}+(1,2,2)+some(1,1,1)'s is shown to have the
following advantages: (i) It is the simplest and almost unique solution that
satisfies M_X = M_{string} ~0.6 x 10^{18} GeV and M_{INT} ~ 5 x10^{11} GeV in
superstring derived SUSY SO(10) GUTs. (ii) The proton is stable enough by the
automatic "doublet-triplet splitting" closely connected with the D-parity
violation. (iii) The minimization of SUSY one-loop effective potential in a toy
model suggests that the SO(10) gauge theory tends to break dynamically down to
the SU(4) x SU(2)_ L x SU(2)_R model.


title: Meson properties in an extended nonlocal NJL model

abstract:
  We consider a nonlocal version of the NJL model, based on a separable
quark-quark interaction. The interaction is extended to include terms that bind
vector and axial-vector mesons. The nonlocality means that no further regulator
is required. Moreover the model is able to confine the quarks by generating a
quark propagator without poles at real energies. Working in the ladder
approximation, we calculate amplitudes in Euclidean space and discuss features
of their continuation to Minkowski energies. Conserved currents are constructed
and we demonstrate their consistency with various Ward identities. Various
meson masses are calculated, along with their strong and electromagnetic decay
amplitudes. We also calculate the electromagnetic form factor of the pion, as
well as form factors associated with the processes gamma gamma^* to pi^0 and
omega to pi^0 gamma^*. The results are found to lead to a satisfactory
phenomenology and lend some dynamical support to the idea of vector-meson
dominance.


title: A fermiophobic SU(2)xSU(2)xU(1) extension of the Standard Model

abstract:
  A new type of gauge extension of the SM is proposed. It is based on a
SU(2)xSU(2)xU(1) group with the peculiarity that the gauge bosons of the extra
SU(2) do not couple to fermions. This feature relaxes some of the constraints
on the masses of the new gauge bosons, leaving the possibility of having
lighter masses than in traditional extensions. The model exhibits several
interesting properties, it is anomaly free and at tree level it does not have
FCNC while loop induced effects are strongly suppressed. Also, from the
analysis of $\Delta \rho$ at one loop, two configurations for the vevs giving
rise to a screening phenomenon are identified. One of these configurations can
also be related with the Bess model. A tree level fit to the most recent
electroweak data is performed confirming the possibility of having new light
gauge boson masses. The constraints coming from different FCNC processes like
$b \to s \gamma$, $B_{0}-{\bar B}_{0}$ and $K_{0}-{\bar K}_{0}$ mixing are also
taken into account. Finally, a generalization of this model for the case of
having several extra copies of SU(2) groups is commented, focusing on the
presence of screening configurations and the corresponding mass spectrum.


title: Towards a Complete Calculation of $\gamma\gamma \to 4f$

abstract:
  We propose a general classification of all four fermion final states in
$\gamma\gamma$ collisions at a future $e^+e^-$ Linear Collider and discuss the
relation of ``signal'' and ``background'' contributions in vector boson
production. We utilize the results in a critical examination of the Higgs
signal in sub-threshold $W^+W^-$ pair production.


title: A violation of the factorization theorem for "hard" inclusive production

abstract:
  This talk is a digest of Ref.[1](E.Gotsman,E. Levin and U. Maor: TAUP
2416/97, hep-ph/9705205,Phys. Lett. (in press)) where a new mechanism for hard
inclusive production, which leads to a violation of the factorization theorem
(FT), is suggested. Numericalestimates for the effect are given for high energy
hadron (nucleus) scattering.


title: Introduction to thermal field theory

abstract:
  Within the next few years experiments at RHIC and the LHC will seek to create
in the laboratory a quark-gluon plasma, the phase of matter in which the
Universe was initially created. It is believed that the plasma will survive
long enough to reach thermal equilibrium. I give an introduction to the
formalism of thermal field theory, the combination of statistical mechanics and
quantum field theory needed to describe the plasma in thermal equilibrium, in a
way that tries to keep close to the physics it describes.


title: Optimal observables for new-physics search at LEP2

abstract:
  New observables \sigma_\pm for the process e^+e^-\to\mu^+\mu^- allow one to
get more direct information on additional Z' boson effects than what is
obtained from the canonical ones, \sigma and A_{FB}. Their deviations from the
Standard Model predictions have very specific energy dependences, which are
precisely determined by SM parameters. At energies varying from TRISTAN to
LEP2, one can uniquely predict the signs of \Delta\sigma_{\pm} induced by a Z'
as well as the locations of their extrema and zeros. This unambiguous energy
correlation could be quite useful in distinguishing effects due to Z' exchange
from those caused by other new physics sources. Furthermore, there are two
energy points, \sqrt{s_{+}}\simeq 78 GeV and \sqrt{s_{-}}\simeq 113 GeV, where
the SM quantities \sigma_\pm^{SM} as well as the deviations \Delta\sigma_{\pm}
attain their minimum values or vanish. These points could be very favourable
for a search for new physics beyond the SM and beyond Z' effects.


title:
Different behaviour of the spin structure functions $g_1(x)$ and
  $h_1(x)$ at $x\to 0$

abstract:
  We consider low-$x$ behaviour of the spin structure functions $g_1(x)$ and
$h_1(x)$ in the unitarized chiral quark model which combines ideas on the
constituent quark structure of hadrons with a geometrical scattering picture
and unitarity. A nondiffractive singular low-$x$ dependence of $g^p_1(x)$ and
$g_1^n(x)$ indicated by the recent SMC experimental data is described. A
diffractive type smooth behaviour of $h_1(x)$ is predicted at small $x$. The
expectations for the double-spin asymmetries in the low-mass Drell-Yan
production at RHIC in the central region are discussed alongside.


title: Physics at LEP2

abstract:
  The main physics topics of interest at LEP2, the CERN electron-positron
collider with center-of-mass energy in the range (161-192) GeV, are reviewed.
Progresses in both the precision tests of the standard model and the field of
discovery physics attainable at this machine are discussed. A few results of
the analysis of data collected in the 1996 first runs of LEP2 are also
presented.


title: Improved determination of the classical sphaleron transition rate

abstract:
  We determine the sphaleron transition rate using real time lattice
simulations of the classical system. An improved definition of the lattice
topological charge allows us to obtain a more reliable estimate of the
transition rate. For an SU(2) Yang-Mills-Higgs system in the broken phase we
find the transition rate to be strongly suppressed, and we have observed no
sphaleron transitions in the range of coupling constants used. For a pure SU(2)
Yang-Mills system in large volumes the rate behaves as $\kappa (\alpha_w T)^4$,
with $\kappa$ slightly decreasing as the lattice spacing is reduced. If the
lattice size is reduced to about twice the magnetic screening length, the rate
is suppressed by finite-size effects, and $\kappa$ is approximately
proportional to the lattice spacing. Our rate measurements are supplemented by
analysis of gauge field correlation functions in the Coulomb gauge.