title: Probing the Couplings of the Top Quark to Gauge Bosons

abstract:
  We parameterize the non-universal couplings of t-t-Z and t-b-W in the
electroweak chiral lagrangian approach, and examine the constraints on these
parameters from the LEP data. We also study how the SLC, Tevatron, LHC and NLC
can improve the measurement of these couplings. Different symmetry breaking
scenarios imply different correlations among these couplings, whose measurement
will then provide a means to probe the electroweak symmetry breaking sector.


title: String and string-inspired phenomenology

abstract:
  In these lectures I review the progress made over the last few years in the
subject of string and string-inspired phenomenology. I take a practical
approach, thereby concentrating more on explicit examples rather than on formal
developments. Topics covered include: introduction to string theory, the
free-fermionic formulation and its general features, generic conformal field
theory properties, $SU(5)\times U(1)$ GUT and string model-building,
supersymmetry breaking, the bottom-up approach to string-inspired models,
radiative electroweak symmetry breaking, the determination of the allowed
parameter space of supergravity models and the experimental constraints on this
class of models, and prospects for direct and indirect tests of string-inspired
models. (Lectures delivered at the XXII ITEP International Winter School of
Physics, Moscow, Russia, February 22 -- March 2, 1994)


title:
Non-equilibrium evolution of the disoriented chiral condensate in
  heavy-ion collisions

abstract:
  We study the dynamics of the chiral phase transition expected during the
expansion of the quark-gluon plasma produced in a high energy hadron or heavy
ion collision in the $O(4)$ linear sigma model to leading order in a large $N$
expansion for strong coupling constants. Starting from an approximate
equilibrium configuration at an initial proper time $\tau$ in the disordered
phase, we study the transition to the ordered broken symmetry phase as the
system expands and cools. We give results for the proper time evolution of the
effective pion mass, the order parameter $<\sigma>$ as well as for the pion two
point correlation function expressed in terms of a time dependent phase space
number density and pair correlation density. We investigate the possibility of
disoriented chiral condensate being formed during the expansion. In order to
create large domains of disoriented chiral condensates low-momentum
instabilities have to last for long enough periods of time. Our simulations
show that instabilities that are formed during the initial stages of the
expansion survive for proper times that are at most $3\,fm/c$.


title: Testing CPT and Quantum Mechanics in the K_0-Kbar_0 System

abstract:
  I report a recent study done in collaboration with M.E. Peskin, on the time
dependence of a kaon beam propagating according to a generalization of quantum
mechanics due to Ellis, Hagelin, Nanopoulos and Srednicki, in which CP- and
CPT-violating signatures arise from the evolution of pure states to mixed
states. Constraints on the magnitude of its parameters are established on the
basis of existing experimental data. New facilities such as phi-factories are
shown to be particularly adequate to study this generalization from \qm\ and to
disentangle its parameters from other CPT violating perturbations of the kaon
system. ( To appear in Proceedings of the First International Conference on
Phenomenology of Unification from Present to Future, Roma, ITALY -- March
23-26, 1994.)


title:
$\tau - \mu - e$ Universality in $\tau$ Decays and Constraints on the
  Slepton Masses

abstract:
  The leptonic $\tau$ decays are calculated at the 1-loop level in the Minimal
Supersymmetric Standard Model. The deviation from the $\tau - \mu - e$
universality is studied as a function of the supersymmetric parameters and
discussed in the context of the expected improvement of the experimental
accuracy.


title: Structure Functions and Small X Physics

abstract:
  We review recent developments in the determination of parton densities from
deep inelastic and related data. We show how the asymmetries observed in the
W+- rapidity distributions and in pp/pn Drell-Yan production further constrain
the partons at moderate x. We compare the GLAP and BFKL descriptions of the
recent measurements of F2(x,Q**2) at HERA. We survey processes which may be
used to identify BFKL dynamics.


title:
Implications of the Top Quark Mass Measurements for the CKM Parameters,
  $\xs$ and CP Asymmetries

abstract:
  Motivated by the recent determination of the top quark mass by the CDF
collaboration, $\mt =174 \pm 10 ^{+13}_{-12}$ GeV, we review and update
constraints on the parameters of the quark flavour mixing matrix $V_{CKM}$ in
the standard model. In performing these fits, we use inputs from the
measurements of $\abseps$, the CP-violating parameter in $K$ decays, $\xd =
(\delm)/\Gamma$, the mixing parameter in \bdbdbar\ mixing, the present
measurements of the matrix elements $\absvcb$ and $\absvub$, and the $B$-hadron
lifetimes. The CDF value for $\mt$ considerably reduces the CKM-parameter space
previously allowed. An interesting result of our analysis is that the present
data can be used to restrict the coupling constant product ratio
$f_{B_d}\sqrt{B_{B_d}}$ to the range 110-270 MeV -- in comfortable agreement
with existing theoretical estimates of this quantity. We use the updated CKM
matrix to predict the \bsbsbar\ mixing ratio $\xs$, as well as the quantities
$\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$, which characterize
  CP-violating asymmetries in $B$-decays.


title: The Form Factors of the Nucleons

abstract:
  We demonstrate that a relativistic constituent quark model can give nucleon
form factors that agree well with recent, accurate measurements. The
relativistic features of the model and the specific form of the wave function
are essential for the result. (Talk given at 14th International Conference on
Few-Body Problems in Physics, Williamsburg, Virginia, USA, May 26-31, 1994)


title: Electroweak Dyons

abstract:
  We consider dyon configurations in the standard electroweak model. In the
presence of a $\theta$ term and no fermions, the usual result $q = (n+\theta
/2\pi ) e$ is obtained for the electric charge spectrum. The effect of
including standard model fermions is discussed qualitatively.


title: Electroweak Strings, Sphalerons and Magnetic Fields

abstract:
  We describe electroweak strings and their ability to carry Chern-Simons
number. Certain string configurations, for any $\theta_W$, carry Chern-Simons
number equal to that of the sphaleron and we conjecture that such strings are
``extended sphalerons''. The production of electroweak strings during the phase
transition is discussed and it is suggested that electroweak strings could
survive long enough for them to play a role in baryogenesis. Finally the issue
of magnetic field generation during the electroweak phase transition is
addressed and several points not discussed in the existing literature are
clarified. A connection is made between electroweak strings and magnetic fields
produced at the phase transition. (Based on the talk presented at the NATO
workshop on ``Electroweak Physics and the Early Universe'', in Sintra, March
1994)


title: QCD sum rules vs. chiral perturbation theory

abstract:
  QCD sum rules are useful tools for studying the spectral properties of
hadrons; however, assumptions underlying standard sum-rule analyses can lead to
inconsistencies with known results of chiral perturbation theory. This
possibility is demonstrated with QCD sum-rule extractions of the nucleon mass
and $\sigma$ term. In both cases, inconsistent chiral behavior leads to an
uncertainty in the sum-rule predictions of $\sim 100\,\text{MeV}$.


title: $\epsilon'/\epsilon$ And Anomalous Gauge Boson Couplings

abstract:
  We study $\epsilon'/\epsilon$ in the Standard Model and $\epsilon'/\epsilon$
due to anomalous $WW\gamma$ and $WWZ$ interactions %using recent result on the
top quark mass from CDF. as a function of the top quark mass. In the Standard
Model, $\epsilon'/\epsilon$ is in the range $10^{-3} \sim 10^{-4}$ for the
central value of top quark mass reported by CDF. The anomalous gauge couplings
can have large contributions to the $CP$ violating $I=2$ amplitude in $K
\rightarrow \pi\pi$. Within the allowed regions for the anomalous gauge
couplings, $\epsilon'/\epsilon$ can be dramatically different from the standard
model prediction.


title:
The Convergence Radius of the Chiral Expansion in the Dyson-Schwinger
  Approach

abstract:
  We determine the convergence radius $m_{conv}$ for the expansion in the
current quark mass using the Dyson-Schwinger (DS) equation of QCD in the
rainbow approximation. Within a Gaussian form for the gluon propagator
$D_{\mu\nu} ({\bf p}) \sim \delta_{\mu\nu} \chi^2 e^{- {{p^2} \over \Delta}}$
we find that $m_{conv}$ increases with decreasing width $\Delta$ and increasing
strength $\chi^2$. For those values of $\chi^2$ and $\Delta$, which provide the
best known description of low energy hadronic phenomena, $m_{conv}$ lies around
$2 \Lambda_{QCD}$, which is big enough, that the chiral expansion in the
strange sector converges. Our analysis also explains the rather low value of
$m_{conv} \approx 50 \dots 80 \ {\text MeV}$ in the Nambu--Jona-Lasinio model,
which as itself can be regarded as a special case of the rainbow DS models,
where the gluon propagator is a constant in momentum space.


title: Next-to-Next-to-Leading Order QCD Analysis of DIS Structure Functions

abstract:
  It is performed for the first time a next-to-next-to-leading order analysis
of deep inelastic structure functions $F_2$ and $F_L$ using the recently
determined first moments of the non-singlet anomalous dimensions and the
corresponding Wilson coefficients. {}From a comparison to BCDMS data we found a
slight decrease in the energy scale of perturbative QCD with respect to the
next-to-leading order analysis, which brings the scale closer to the value
predicted from a scheme invariant approach.


title: Pseudo Dirac Neutrinos in Seesaw Model

abstract:
  Specific class of textures for the Dirac and Majorana mass matrices in the
seesaw model leading to a pair of almost degenerate neutrinos is discussed.
These textures can be obtained by imposing a horizontal $U(1)$ symmetry. A
specific model is discussed in which: (1) All three neutrino masses are similar
in magnitude and could lie around eV providing hot component of the dark matter
in the universe. (2) Two of these are highly degenerate and their
${\hbox{(mass)}}^2$ difference could solve the solar neutrino problem through
large angle MSW solution. (3) The electron neutrino mass may be observable
through Kurie plot as well as through search of the neutrinoless double beta
decay.


title: Leptonic Flavor Violations in the Presence of an Extra Z

abstract:
  Gauged extensions [$SU(2)_L\otimes U(1)_Y\otimes U(1)_X$] of the standard
$SU(2)_L\otimes U(1)_Y$ model obtained without extending the fermion content of
the model are studied. Models that are possible when $U(1)_X$ is identified
with some combination of the family lepton numbers are systematically
classified. Most of these contain flavor violations in the leptonic sector.
These flavor violations are correlated to the mixing of the $U(1)_X$ gauge
boson $Z'$ with the ordinary $Z$ in the models considered here. Detailed
phenomenological implications of a typical model are discussed. Constraints on
the $Z'$ mass and the $Z$-$Z'$ mixing following from ({\em i}) the observations
at LEP, ({\em ii}) rare processes like $Z\rightarrow e\tau$ and ({\em iii})
flavor violating $\tau$ decays are presented. It is found that the constraints
coming from the LEP allows the rare processes like $\tau \rightarrow eee $ at
the level of the present limits on its branching ratio. Thus the future search
could either improve on the existing LEP limits or would find such flavor
violating decays.


title: Neutrino Magnetic Moments and the Solar Neutrino Problem

abstract:
  Present status of the neutrino magnetic moment solutions of the solar
neutrino problem is reviewed. In particular, we discuss a possibility of
reconciling different degrees of suppression and time variation of the signal
(or lack of such a variation) observed in different solar neutrino experiments.
It is shown that the resonant spin--flavor precession of neutrinos due to the
interaction of their transitions magnetic moments with solar magnetic field can
account for all the available solar neutrino data. For not too small neutrino
mixing angles ($\sin 2\theta_0 \aprge 0.2$) the combined effect of the resonant
spin--flavor precession and neutrino oscillations can result in an observable
flux of solar $\bar{\nu}_{e}$'s.


title:
Estimates of the O(alpha_s^4) corrections to sigma_{tot}(e^+e^-
  \rightarrow hadrons), Gamma(\tau\rightarrow \nu_{\tau} +hadrons) and deep
  inelastic scattering sum rules

abstract:
  We present the estimates of the order $O(\alpha^{4}_{s})$ QCD corrections to
$R(s)$, $R_{\tau}$ and to the deep-inelastic scattering sum rules, namely to
the non-polarized and polarized Bjorken sum rules and to the Gross-Llewellyn
Smith sum rule. The estimates are obtained in the $\overline{MS}$-scheme using
the principle of minimal sensitivity and the effective charges approach.


title: The Transition to Perturbative QCD in Compton Scattering

abstract:
  We investigate the transition to perturbative QCD in Compton processes, by
concentrating on the specific reactions $\pi \gamma \to \pi \gamma$ and pion
photoproduction at moderate energy scales. New sum rules for each of the
helicities involved in the scattering and the cross section are given, together
with a detailed stability analysis. Our results are then compared with those
derived from higher-power factorization, incorporating Sudakov suppression for
quark elastic scattering. An overlap of predictions obtained by the two
approaches is observed at a momentum transfer as low as 4 GeV$^2$ and at a
photon scattering angle around 40$^o$. Our work shows that factorization
theorems and sum rule methods complement each other in the description of
Compton scattering at moderate energy scales, and give information on the
transition to perturbative QCD in these processes. The sum rule formalism is
further applied to the crossed reaction $\gamma \gamma\to \pi^+ \pi^-$, and is
in very good agreement with the experimental data."


title: Detecting Nutau Oscillations as PeV Energies

abstract:
  It is suggested that a large deep underocean neutrino detector, given the
presence of significant numbers of neutrinos in the PeV range as predicted by
various models of Active Galactic Nuclei, can make unique measurements of the
properties of neutrinos. It will be possible to observe the existence of the
nu_tau, measure its mixing with other flavors, in fact test the mixing pattern
for all three flavors based upon the mixing parameters suggested by the
atmospheric and solar neutrino data, and measure the nu_tau cross section. The
key signature is the charged current nu_tau interaction, which produces a
double cascade, one at either end of a minimum ionizing track. At a few PeV
these cascades would be separated by roughly 100 m, and thus be easily
resolvable in DUMAND and similar detectors. Future applications are precise
neutrino astronomy and earth tomography.


title: Pentaquark Exotic Baryons in the Skyrme Model

abstract:
  We investigate the pentaquark($P$) exotic baryons as soliton-antiflavored
heavy mesons bound states in the limit of infinitely heavy meson mass. Our
approach respects the chiral symmetry as well as the heavy quark symmetry. The
results reveal a possibility for the loosely bound non-strange $P$-baryon(s).


title: Static Quantities of the W-Boson in the MSSM

abstract:
  We systematically analyze the anomalous dipole $\Delta k_{\gamma}$ and
quadrupole $\Delta Q_{\gamma}$ moments of the W gauge bosons in the context of
the minimal supersymmetric standard model as functions of the soft SUSY
breaking parameters $A_0,m_0,M_{1/2}$ and the top quark mass. The severe
constraints imposed by the radiative breaking mechanism of the electroweak
symmetry\,$ SU(2)\times U(1)$\, are duly taken into account. The supesymmetric
values of $\Delta k_{\gamma}$ and $\Delta Q_{\gamma}$ can be largely different,
in some cases, from the standard model predictions but of the same order of
magnitude for values of \quad $A_0,m_0,M_{1/2} \leq {\cal O}(1 TeV) $.
Therefore possible supersymmetric structure can be probed provided the accuracy
of measurements for $\Delta k_{\gamma}$, $\Delta Q_{\gamma}$ reaches
$10^{-2}-10^{-3}$ and hence hard to be detected at LEP2. If deviations from the
standard model predictions are observed at LEP2, most likely these are not due
to an underlying supersymmetric structure. In cases where $M_{1/2} \ll A_0,m_0
$, the charginos and neutralinos may give substantial contributions saturating
the LEP2 sensitivity limits. This occurs when their masses $m_{\tilde
C},m_{\tilde Z}$ turn out to be both light satisfying $m_{\tilde C}+m_{\tilde
Z} \simeq M_W $. However these extreme cases are perturbatively untrustworthy
and besides unnatural for they occupy a small region in the parameter space. }


title:
Two-Loop ${\cal O}(\alpha_sG_Fm_t^2)$ Corrections to the Fermionic Decay
  Rates of the Standard-Model Higgs Boson

abstract:
  Low- and intermediate mass Higgs bosons decay preferably into fermion pairs.
The one-loop electroweak corrections to the respective decay rates are
dominated by a flavour-independent term of ${\cal O}(G_Fm_t^2)$. We calculate
the two-loop gluon correction to this term. It turns out that this correction
screens the leading high-$m_t$ behaviour of the one-loop result by roughly
10\%. We also present the two-loop QCD correction to the contribution induced
by a pair of fourth-generation quarks with arbitrary masses. As expected, the
inclusion of the QCD correction considerably reduces the renormalization-scheme
dependence of the prediction.


title: Search for the QCD Ground State

abstract:
  Within the Euclidean effective action approach we propose criteria for the
ground state of QCD. Despite a nonvanishing field strength the ground state
should be invariant with respect to modified Poincar\'e transformations
consisting of a combination of translations and rotations with suitable gauge
transformations. We have found candidate states for QCD with four or more
colours. The formation of gluon condensates shows similarities with the Higgs
phenomenon.


title: Threshold Effects in Two--Photon Decays of Higgs Particles

abstract:
  The couplings of Higgs particles to two photons are analyzed in the threshold
region, where the Higgs mass is about twice the loop--particle mass leading to
possible bound state formation. The amplitude of the pseudoscalar decay $A\to
\gamma\gamma$ for pseudoscalar masses in the range of $(t\bar t)$--bound state
masses is calculated in leading and next--to--leading order in $\alpha_s$. It
is shown that the real and imaginary parts of the form factor are significantly
different from the lowest order perturbative one.


title: Model-independent determination of $Z'$ couplings at LEP 200

abstract:
  All couplings of a new heavy gauge boson to ordinary fermions can be
determined in a model-independent way at a large $e^+e^-$ collider for large
enough statistics. No such determination is possible at LEP 200, however,
because its design integrated luminosity is too low for existing and
forthcoming limits on $Z'$ interactions. At any rate, it should be possible to
distinguish between models for $Z'$ masses $< 1\ TeV$, or to set limits of this
order on $Z'$ masses for definite models. These are (preliminary) $1\sigma $
limits. We neglect systematic errors and assume an integrated luminosity of
$0.5\ fb^{-1}$.


title: Pion Content of the Nucleon as seen in the NA51 Drell-Yan experiment

abstract:
  In a recent CERN Drell-Yan experiment the NA51 group found a strong asymmetry
of $\bar u$ and $\bar d$ densities in the proton at $x\simeq0.18$. We interpret
this result as a decisive confirmation of the pion-induced sea in the nucleon.


title: Bloch-Nordsieck cancellations beyond logarithms in heavy particle decays

abstract:
  We investigate the one-loop radiative corrections to the semileptonic decay
of a charged particle at finite gauge boson mass. Extending the Bloch-Nordsieck
cancellation of infrared logarithms, the subsequent non-analytic terms are also
found to vanish after eliminating the pole mass in favor of a mass defined at
short distances. This observation justifies the operator product expansion for
inclusive decays of heavy mesons and implies that infrared effects associated
with the summation of the radiative corrections are suppressed by at least
three powers of the mass of the heavy decaying particle.


title: Phase Transition in Extended Electroweak Theory

abstract:
  The phase transition in the Weinberg-Salam-Glashow (GSW) electroweak theory
extended by the majoron and dilaton field is considered. The possibility of the
boson condensation in the extreme conditions in the standard electroweak theory
is shown. The first order phase transition induces by the radiative corrections
(the Coleman-Weinberg potential) in the presence of matter was considered. Due
to t-quark mass ($\sim 174\ GeV$) a relatively high Higgs mass ($\sim 313 \
GeV$) was obtained. Only a fraction of this mass is connected to the
Coleman-Weinberg potential ($m_{CW} \sim 15\ GeV$). The model produces the
first order phase transition for low temperature ($T_c \sim 10\ GeV$).
Formation of bubbles filled with matter was considered near the phase
transition point. The realistic ball with $ M \sim 10^5 - 10^9 M_{\odot}$ and
the radius $ R \sim 10^{12} - 10^{14} cm$ is obtained.


title:
Relativistic Quark-Antiquark Bound State Problem with Spin-dependent
  Interactions in Momentum Space

abstract:
  The work described in this paper is the first step toward a relativistic
three-quark bound-state calculation using a Hamiltonian consistent with the
Wigner-Bargmann theorem and macroscopic locality. We give an explicit
demonstration that we can solve the two-body problem in momentum space with
spin-dependent interactions. The form of the potential is a combination of
linear+Coulomb+spin-spin+% spin-orbit+tensor, which includes confinement and is
of the general form consistent with rotation, space-reflection and
time-reversal invariance. Comparison is made with previous calculations using
an alternate technique and with the experimental meson mass spectrum. The
results obtained suggest that the model is realistic enough to provide a
two-body basis for the three quark baryon problem in which the Poincar\'{e}
group representation is unitary and cluster separability is respected.


title: Signatures of discrete symmetries in the scalar sector

abstract:
  I discuss methods to identify the presence of dicrete symmetries in the
two-Higgs-doublet model by observing the masses and the cubic and quartic
interactions of the scalars. The symmetries considered are a $ Z_2 $ symmetry
under which $ \phi_2 \rightarrow - \phi_2 $, and a CP symmetry which enforces
real coupling constants in the Higgs potential. Those symmetries are
spontaneously broken, and the $ Z_2 $ symmetry may also be softly broken. I
identify the signatures in the interactions of the scalars that these
symmetries leave after their breaking.


title:
Corrections of Order ${\cal O}(G_F\alpha_s m_t^2)$ to the Higgs Decay
  Rate $\Gamma(H\to b\bar{b})$

abstract:
  QCD corrections to the electroweak one-loop result for the partial width
$\Gamma(H\rightarrow b\bar{b})$ are studied. For the decay channel into bottom
quarks the rate is affected by a virtual top quark through electroweak
interactions. The calculation of QCD corrections to this quantity is performed
for an intermediate range Higgs mass in the heavy top mass limit. The leading
correction of order ${\cal O}(G_F\alpha_s m_t^2)$ is estimated. Numerically the
contribution is of comparable size as the electroweak correction, but of
opposite sign.


title: Damping Rate of a Hard Photon in a Relativistic Plasma

abstract:
  The damping rate of a hard photon in a hot relativistic QED and QCD plasma is
calculated using the resummation technique by Braaten and Pisarski.


title:
QCD Calculation of $B$ Meson Form Factors and Exclusive Nonleptonic
  Decays

abstract:
  The method of QCD sum rules has proven to be particularly useful in heavy
quark physics, where a small distance scale is provided by the inverse heavy
quark mass. We present two new examples for the application of this method to
B-physics: a calculation of the heavy-to-light form factors $B \rightarrow
\pi,K$ and an estimate of the weak decay amplitude for $B \rightarrow J/\psi K
$ beyond the factorization approximation.


title: Extended Variational Approach to the SU(2) Mass Gap on the Lattice

abstract:
  The linear delta expansion is applied to a calculation of the SU(2) mass gap
on the lattice. Our results compare favourably with the strong-coupling
expansion and are in good agreement with recent Monte Carlo estimates.


title: Supercooling of the quark-gluon plasma

abstract:
  Transition from the quark-gluon (QG) plasma to a hadronic gas is studied in
the framework of the relativistic combustion theory. The calculations reveal
that the QG phase must be in a strongly supercooled state. The stability of
this solution with respect to minor modifications is investigated. In
particular the effect of an admixture of hadronic matter in the QG phase is
considered in detail.


title: Yukawa Unification: The Good, The Bad and The Ugly

abstract:
  We analyze some consequences of grand unification of the third-generation
Yukawa couplings, in the context of the minimal supersymmetric standard model.
We address two issues: the prediction of the top quark mass, and the generation
of the top-bottom mass hierarchy through a hierarchy of Higgs vacuum
expectation values. The top mass is strongly dependent on a certain ratio of
superpartner masses. And the VEV hierarchy always entails some tuning of the
GUT-scale parameters. We study the RG equations and their semi-analytic
solutions, which exhibit several interesting features, such as a focusing
effect in the limit of certain symmetries and a correlation between the $A$
terms (which contribute to $b\rightarrow s\gamma$) and the gaugino masses. This
study shows that non-universal soft-SUSY-breaking masses are favored (in
particular for splitting the Higgs doublets via D-terms and for allowing more
natural scenarios of symmetry breaking), and hints at features desired in
Yukawa-unified models. Several phenomenological implications are also revealed.


title: Flavour Dependence of Form Factors in Heavy Meson Decays

abstract:
  Recently we have shown that due account of Wigner spin rotations is needed to
match the ISGW model consistently onto HQET. We now discuss the flavour
dependence of this procedure. We find that for finite mass ``heavy'' quark the
universal function $\xi(y=1) \approx 1$ but the slope is proportional to the
energy of the spectator quarks, and ratios of form factors are corrected in a
way that QCD sum rules seem to require. Predictions for heavy quarks, such as
in $B_c \rightarrow \psi(\eta_c)$ and to mixed systems, such as $D\rightarrow
K$ and $B \rightarrow \pi$ show a systematic mass dependence that may be
confronted with data.


title: On Primordial Magnetic Fields

abstract:
  A primordial magnetic field could be responsible for the observed magnetic
fields of the galaxies. One possibility is that such a primordial field is
generated at the electroweak phase transition because of the fluctuations in
the Higgs field gradients. I describe a statistical averaging procedure which
gives rise to a field of a correct magnitude. Another possibility, where the
Yang-Mills vacuum itself is ferrromagnetic, is also discussed.


title: On the Evolution of Magnetic Fields in the Early Universe

abstract:
  We address the question of the existence of magnetic domains in a recent
scenario for the creation of primordial magnetic fields. We write down the
magnetohydrodynamic equation in an expanding universe in the infinite
conductivity limit and discuss its solution. No domains are found.


title: Higher-order corrections to Higgs-boson decays

abstract:
  We review the status of radiative corrections to the decay rates of the
Standard-Model Higgs boson in the mass range accessible at LEP~2. Specifically,
we consider corrections of ${\cal O}(\alpha)$, ${\cal O}(\alpha_sG_Fm_t^2)$,
and ${\cal O}(G_F^2M_H^4)$ to the fermionic decay rates and two-loop QCD
corrections to the hadronic decay rates.


title:
Failure of the commonly used B -> K(K^*) form factors in explaining
  recent data on B -> J/\Psi + K ( K^* ) decays

abstract:
  We establish restrictions on $B \ra K ( K^* )$ form factors imposed by recent
data on $B \ra J/\Psi + K ( K^* ) $ decay rates and polarization. We show that
these constraints are not satisfied by few commonly used models. Finally, we
relate $B \ra K ( K^* )$ form factors to those in $D \ra K ( K^* )$ transitions
using the heavy flavour symmetry as proposed by Isgur and Wise and discuss the
uncertainties in this procedure. We find that this method also leads to form
factors excluded by data.


title: The Electroweak Phase Transition in Extended Models

abstract:
  We study the possibility of relaxing the cosmological bound on the Higgs mass
coming from the requirement of non-erasure of the baryon asymmetry by
sphalerons. After reviewing the Standard Model case we obtain this bound in two
extensions of it: 1) The Standard Model with an additional gauge singlet, and
2) The Minimal Supersymmetric Standard Model. Taking fully into account all
experimental constraints and thermal screening effects we found that the
situation can be slightly improved with respect to the Standard Model but only
in case 1) a non negligible region in parameter space exists where the baryon
washout is avoided and the experimental bounds evaded. (Talk given at the NATO
Advanced Reseach Workshop: "Electroweak Physics and the early Universe", 23-25
March 1994, Sintra (Portugal).)


title: Double Asymptotic Scaling at HERA

abstract:
  Perturbative QCD predicts that at sufficiently large $Q^2$ and small $x$
nucleon structure functions should exhibit scaling in the two variables
$\sqrt{\ln\smallfrac{1}{x}\ln\ln Q^2}$ and
$\sqrt{\ln\smallfrac{1}{x}\big/\ln\ln Q^2}$, provided only that the small-$x$
behaviour of the input to the perturbative QCD evolution is sufficiently soft.
We derive these asymptotic results by writing the gluonic Altarelli--Parisi
equation at small $x$ as a two--dimensional wave equation, which propagates the
gluon distribution from its boundaries into the asymptotic region. We then show
that the existing experimental data on $F_2^p(x,Q^2)$ from HERA provide a
remarkable confirmation of both of these scaling predictions. The so--called
`hard' pomeron, which does not scale, may thus be excluded by more than three
standard deviations, at least in the presently accessible kinematical regime.
We propose that existing and future data from HERA should be binned in the two
scaling variables, in order to search for scaling violations.


title: Running of the Top Yukawa with and without Light Gluinos

abstract:
  We investigate correlations among various parameters in the solution space of
minimal supersymmetric grand unification. In particular the extent to which the
top quark Yukawa coupling exhibits fixed point behavior is discussed and we
compare various analytic approximations to its value at the top mass with its
exact value in numerical solutions.\\ $^*$ Talk presented at the Workshop on
Yukawa Couplings and the Origin of Mass, Gainesville, Florida, Feb. 11-13,
1994\\


title: A Global Analysis of the Top Quark Couplings to Gauge Bosons

abstract:
  We propose to probe the electroweak symmetry breaking sector by measuring the
effective couplings of the top quark to gauge bosons. Using precision LEP data,
we constrain the non--universal couplings of t-t-Z and t-b-W, parameterized by
$\kappa_{L}^{NC}$, $\kappa_{R}^{NC}$, $\kappa_{L}^{CC}$ and $\kappa_{R}^{CC}$,
in the electroweak chiral lagrangian framework. Different scenarios of
electroweak symmetry breaking will imply different correlations among these
parameters. We found that at the order of ${m_t}^{2}\log {\Lambda}^2$, in which
$\Lambda \sim 4 \pi v$ is the cut--off scale of the effective theory,
$\kappa_{L}^{NC}$ is already constrained by LEP data. In models with an
approximate custodial symmetry, a positive $\kappa_{L}^{CC}$ is preferred.
$\kappa_{L}^{CC}$ can be constrained by studying the direct detection of the
top quark at the Tevatron and the LHC. At the NLC, $\kappa_{L}^{NC}$ and
$\kappa_{R}^{NC}$ can be better measured.


title: Sea-quark Content of Nucleons from Proton-induced Drell-Yan Production

abstract:
  We analyse the proton-induced Drell-Yan production in both the flavor
asymmetry and isospin breaking explanations for the violation of the Gottfried
sum rule. Consequences from three different forms of corrections to the flavor
and isospin symmetric parton distributions are examined. It is found that the
calculated results are sensitive to the choices of parameters and parton
distributions, and to the ways the corrections are introduced. All three forms
of corrections could be consistent with the recent Fermilab Experiment E772
data for the ratio of cross section $R=\sigma_{W}/\sigma_{IS}$ and for the
shape of the differential cross section $m^{3}d^{2}\sigma/dx_{F}dm$ for
$^{2}$H.


title: QED With Unequal Charges: A study of spontaneous Zn symmetry breaking

abstract:
  We study two-dimensional QED with unequal charges at finite temperature, and
show that there is a phase with a spontaneously broken $Z_n$ symmetry. In spite
of this, we were not able to establish the presence of domain walls. The
relevance for QCD in higher dimensions is discussed.


title:
Quark Mass Effects in Fermionic Decays of the Higgs Boson in
  $O(\alpha_s^2)$ Perturbative QCD

abstract:
  The results of analytical evaluation of $O(\alpha_s^2)$ QCD contributions due
to the nonvanishing quark masses to $\Gamma_{H\rightarrow q_f\overline{q}_f}$
are presented. The ``triangle anomaly'' type contributions are included. As a
byproduct the $O(\alpha_s^3)$ logarithmic contributions are evaluated. The
results are presented both in terms of running and pole quark masses. The
partial decay modes $H \rightarrow b\overline{b}$ and $H \rightarrow
c\overline{c}$ are considered. The calculated corrections decrease the absolute
value of large and negative $O(\alpha_s^2)$ massless limit coefficient by $\leq
1\%$ in the intermediate mass region and by 1\%$ - $20\% in the low mass region
which, however, is experimentally ruled out.
  The results are relevant for $H \rightarrow t\overline{t}$ decay mode for the
higher Higgs mass region where the mass effects are large and important. The
high order corrections remove a very large discrepancy between the results for
$\Gamma_{H\rightarrow q_f\overline{q}_f}$ in terms of running and pole quark
masses almost completely and reduce the scale dependence from about 40\% to
nearly 5\%.


title:
How to Use Weak Decays in Analyses of Data on Nucleon Spin Structure
  Functions

abstract:
  The use of weak decays to determine proton spin structure is examined in view
of possible violations of the Bjorken and Gottfried Sum rules, flavor symmetry
breaking and flavor asymmetry in the sea. The use of the neutron decay is found
to be unaffected by all these. A method for including these effects in analyses
of hyperon decays shows that a flavor-asymmetric sea produced by SU(3) symmetry
breaking has only a small effect on results for the total spin carried by
quarks. However the strange quark contribution cannot be reliably obtained from
charged lepton scattering and weak decay data alone, and requires additional
model-dependent input relating nucleon and hyperon wave functions.


title: Light Scalar Top and Heavy Top Signature at CDF

abstract:
  We propose a mechanism which could explain a slight excess of top signal rate
recently reported by CDF in the framework of the supersymmetric standard model.
If the scalar partner of the top (stop) is sufficiently light, the gluino with
an appropriate mass could decay into the stop plus the top with almost 100\%
branching ratio and experimental signatures of the gluino pair production could
be indistinguishable from those of the top production in the present integrated
luminosity Tevatron running. In this case the standard top signal, $W$ $+$
multi-jets events, would be effectively enhanced by the additional gluino
contribution. It is shown, moreover, that such a mechanism can actually work in
the radiative SU(2)$\times$U(1) breaking model without the GUT relations
between the gaugino mass parameters.


title: QCD Physics at LEP 2

abstract:
  I will discuss, in a concise way, the main objectives of QCD studies at LEP
2.


title: Left-Right Symmetry and Supersymmetric Unification

abstract:
  The existence of an SU(3) X SU(2)_L X SU(2)_R X U(1) gauge symmetry with g_L
= g_R at the TeV energy scale is shown to be consistent with supersymmetric
SO(10) grand unification at around 1O^{16} GeV if certain new particles are
assumed. The additional imposition of a discrete Z_2 symmetry leads to a
generalized definition of R parity as well as highly suppressed Majorana
neutrino masses. Another model based on SO(10) X SO(10) is also discussed.


title: Masses of the Light Quarks

abstract:
  The magnitude of $m_u,\,m_d$ and $m_s$ is discussed on the basis of Chiral
Perturbation Theory. In particular, the claim that $m_u=0$ leads to a coherent
picture for the low energy structure of QCD is examined in detail. It is
pointed out that this picture leads to violent flavour asymmetries in the
matrix elements of the scalar and pseudoscalar operators, which are in conflict
with the hypothesis that the light quark masses may be treated as
perturbations. [Talk delivered at the 2nd IFT Workshop, "Yukawa Couplings and
the Origins of Mass", Gainesville, Florida, Feb. 1994, to be published by
International Press.]


title: QCD Sum Rules for $\Sigma$ Hyperons in Nuclear Matter

abstract:
  Within finite-density QCD sum-rule approach we investigate the self-energies
of $\Sigma$ hyperons propagating in nuclear matter from a correlator of
$\Sigma$ interpolating fields evaluated in the nuclear matter ground state. We
find that the Lorentz vector self-energy of the $\Sigma$ is similar to the
nucleon vector self-energy. The magnitude of Lorentz scalar self-energy of the
$\Sigma$ is also close to the corresponding value for nucleon; however, this
prediction is sensitive to the strangeness content of the nucleon and to the
assumed density dependence of certain four-quark condensate. The scalar and
vector self-energies tend to cancel, but not completely. The implications for
the couplings of $\Sigma$ to the scalar and vector mesons in nuclear matter and
for the $\Sigma$ spin-orbit force in a finite nucleus are discussed.


title: Proton Decay and Neutrino Masses in SO(10)

abstract:
  In the last few years physicists have been looking at $SO(10)$ GUT models
with renewed attention because it has been realized that the SU(5) minimal
model cannot unify the strong, electromagnetic and weak interactions in a way
consistent with the experimental values of $\alpha(M_Z)$, $\si$ and
$\alpha_S(M_Z)$. In this paper we derive lower limits on neutrino masses,
relevant for cosmology and for the solar-neutrino problem, from necessary
consistency conditions on a class of $SO(10)$ models with $\sq$ or $\stt$
intermediate gauge symmetry.


title:
Equation of State for Particles Arising at the Universe at Grand
  Unification Energies

abstract:
  First postinflationary stage of the Universe evolution is considered in more
detail. It is shown that heavy particles with mass $M_{H}\sim M_{GUT}$ arising
at the Universe at phase transitions at Grand Unification Energies behave like
ideal quantum degenerate Bose gas. The equation of state for both scalar and
gauge bosons is presented including the coupling constant and vacuum
expectation value at $E_{GUT}$. One possible way is proposed to connect
cosmological observational data with parameters of Grand Unified Theories.


title: Majorana Masses for Neutrinos in SO(10)

abstract:
  We study the predictions for Majorana masses for neutrinos in SO(10)
grandunification models. (This paper precedes and is cited in the article
"PROTON DECAY AND NEUTRINO MASSES IN SO(10)", hep-ph/9405332)


title: Instanton interactions and non-perturbative particle production in QCD

abstract:
  I discuss the possible instanton-induced multiparticle production in hard
processes in QCD Figures are available upon request


title: Large Scale Inhomogeneities from the QCD Phase Transition

abstract:
  We examine the first-order cosmological QCD phase transition for a large
class of parameter values, previously considered unlikely. We find that the
hadron bubbles can nucleate at very large distance scales, they can grow as
detonations as well as deflagrations, and that the phase transition may be
completed without reheating to the critical temperature. For a subset of the
parameter values studied, the inhomogeneities generated at the QCD phase
transition might have a noticeable effect on nucleosynthesis.


title:
Flat Potential for Inflaton with a Discrete $R$-invariance in
  Supergravity

abstract:
  We show that a very flat potential of inflaton required for a sufficient
inflation is naturally obtained in $N=1$ supergravity by imposing a discrete
$R$-invariance $Z_{n}$. Several cosmological constraints on parameters in the
inflaton superpotential are derived. The reheating temperature turns out to be
$(1-10^8)$GeV for the cases of $n$=3--10. Baryogenesis in this model is also
discussed briefly.


title: Structure functions and low x physics

abstract:
  In the framework of conventional Regge theory we present a common description
of total photon-proton cross-section and proton structure functions in the
region $0 \leq Q^2 \leq 5 \ {\rm GeV}^2$. Using it as an initial condition in
the perturbative QCD evolution equation, we describe structure functions at any
$Q^2$ and $x$ - including the small $x$ region explored at HERA.


title: The Anharmonic Correction in the Soliton Model for the Hyperons

abstract:
  We derive the anharmonic correction to the hyperon energy in the bound state
version of the topological soliton model for the hyperons, and show that it
represents a negative correction of at most 10% to the energy of the bound
heavy flavour two-meson system in the case of cascade hyperons. The main
anharmonic correction arises from the mass term in the Lagrangian density. For
large meson masses the consistency of the model requires that the anharmonic
correction decreases as the inverse square root of the mass of the heavy
flavour meson.


title:
A Critical Analysis of the Proton Form Factor with Sudakov Suppression
  and Intrinsic Transverse Momentum

abstract:
  The behavior of the proton magnetic form factor is studied within the
modified hard scattering picture, which takes into account gluonic radiative
corrections in terms of transverse separations. We parallel the analysis given
previously by Li and make apparent a number of serious objections. The
appropriate cut-off needed to render the form-factor calculation finite is both
detailed and analyzed by considering different cut-off prescriptions. The use
of the maximum interquark separation as a common infrared cut-off in the
Sudakov suppression factor is proposed, since it avoids difficulties with the
$\alpha _{s}$-singularities and yields a proton form factor insensitive to the
inclusion of the soft region which therefore can be confidently attributed to
perturbative QCD. Results are presented for a variety of proton wave functions
including also their intrinsic transverse momentum. It turns out that the
perturbative contribution, although theoretically self-consistent for $Q^{2}$
larger than about $6$~GeV${}^{2}$ to $10$~GeV${}^{2}$, is too small compared to
the data.


title: Virtual Photons in Chiral Perturbation Theory

abstract:
  In the framework of chiral perturbation theory virtual photons are included.
We calculate the divergences of the generating functional to one loop and
determine the structure of the local action that incorporates the counterterms
which cancel the divergences. As an application we discuss the corrections to
Dashen's theorem at order [e^2*m(quark)].


title: Predictions of SUSY Masses in the Minimal SUSY GUT

abstract:
  The MSSM distinguishes itself from other GUT's by a successful prediction of
many unrelated phenomena with a minimum number of parameters. Among them: a)
Unification of the couplings constants; b)Unification of the masses; c) Proton
decay; d) Electroweak symmetry breaking. A combined fit of the free parameters
in the MSSM to these low energy constraints shows that the MSSM model can
satisfy these constraints simultaneously. From the fitted parameters the masses
of the as yet unobserved superpartners of the SM particles are predicted. The
2nd order QCD coupling constant is required to be between 0.108 and 0.132. It
is shown that a top mass of $174\pm16$ GeV, as suggested recently by the CDF
Collaboration, constrains the mixing angle between the Higgs doublets in the
MSSM to: $1.2<\tb<5.5$ at the 90% C.L.. The most probable value corresponds to
$\tb = 1.56$, which leads to a stop mass below the top mass. In this case the
stop production in $p\bar{p}$ collisions would contribute to the top signature.
This could be an explanation for the large effective $t\bar{t}$ cross section
observed by CDF.


title: The Three Loop Equation of State of QED at High Temperature

abstract:
  We present the three loop contribution (order $e^4$) to the pressure of
massless quantum electrodynamics at nonzero temperature. The calculation is
performed within the imaginary time formalism. Dimensional regularization is
used to handle the usual, intermediate stage, ultraviolet and infrared
singularities, and also to prevent overcounting of diagrams during resummation.


title:
Penguins leaving the pole: bound-state effects in B decaying to K* +
  photon

abstract:
  Applying perturbative QCD methods recently seen to give a good description of
the two body hadronic decays of the B meson, we address the question of
bound-state effects on the decay B into K* + gamma. Consistent with most
analyses, we demonstrate that gluonic penguins, with photonic bremsstrahlung
off a quark, change the decay rate by only a few percent. However, explicit
off-shell b-quark effects normally discarded are found to be large in
amplitude, although in the standard model accidents of phase minimize the
effect on the rate. Using an asymptotic distribution amplitude for the K* and
just the standard model, we can obtain a branching ratio of a few times
10^{-5}, consistent with the observed rate.


title: The R Axion From Dynamical Supersymmetry Breaking

abstract:
  All generic, calculable models of dynamical supersymmetry breaking have a
spontaneously broken $R$ symmetry and therefore contain an $R$ axion. We show
that the axion is massive in any model in which the cosmological constant is
fine-tuned to zero through an explicit $R$-symmetry-breaking constant. In
visible-sector models, the axion mass is in the 100 MeV range and thus evades
astrophysical bounds. In nonrenormalizable hidden-sector models, the mass is of
order of the weak scale and can have dangerous cosmological consequences
similar to those already present from other fields. In renormalizable hidden-
sector models, the axion mass is generally quite large, of order $10^7$ GeV.
Typically, these axions are cosmologically safe. However, if the dominant decay
mode is to gravitinos, the potentially large gravitino abundance that arises
from axion decay after inflation might affect the successful predictions of
big-bang nucleosynthesis. We show that the upper bound on the reheat
temperature after standard inflation can be competitive with or stronger than
bounds from thermal gravitino production, depending on the model and the
gravitino mass.


title: Inconclusive Inclusive Nonleptonic $B$ Decays

abstract:
  We reconsider the conflict between recent calculations of the semileptonic
branching ratio of the $B$ meson and the experimentally measured rate. Such
calculations depend crucially on the application of ``local duality'' in
nonleptonic decays, and we discuss the relation of this assumption to the
weaker assumptions required to compute the semileptonic decay rate. We suggest
that the discrepancy between theory and experiment might be due to the channel
with two charm quarks in the final state, either because of a small value for
$m_c$ or because of a failure of local duality. We examine the experimental
consequences of such solutions for the charm multiplicity in $B$ decays.


title: Another Source of Baryons in $B$ Meson Decays

abstract:
  It is usually assumed that the production of baryons in $B$ meson decays is
induced primarily by the quark level process $b\to c\bar ud$, where the charm
quark hadronizes into a charmed baryon. With this assumption, the $\Lambda_c$
momentum spectrum would indicate that the transition $B\to\Lambda_c X$ is
dominated by multi-body $B$ decays. However, a closer examination of the
momentum spectrum reveals that the mass $m_X$ against which the $\Lambda_c$ is
recoiling almost always satisfies $m_X\agt m_{\Xi_c}$. This fact leads us to
examine the hypothesis that the production of charmed baryons in $B$ decays is
in fact dominated by the underlying transition $b\to c\bar cs$, and is seen
primarily in modes with two charmed baryons in the final state. We propose a
number of tests of this hypothesis. If this mechanism is indeed important in
baryon production, then there are interesting consequences and applications,
including potentially important implications for the ``charm deficit'' in $B$
decays.


title:
Perturbative QCD Fragmentation Functions for Production of P-wave Mesons
  with Charm and Beauty

abstract:
  We calculate the leading order QCD fragmentation functions for the production
of $P$-wave charmed beauty mesons. Long-distance effects are factored into two
nonperturbative parameters: the derivative of the radial wavefunction at the
origin and a second parameter related to the probability for a $(\bar b c)$
heavy quark pair that is produced in a color-octet $S$-wave state to form a
color-singlet $P$-wave bound state. The four $2P$ states and those $3P$ states
which lie below the $BD$ flavor threshold eventually all decay into the $1S$
ground state $B_c$ through hadronic cascades or by emitting photons. The total
fragmentation probabilities for production of the $1S$ ground state $B_c$ from
the cascades of the $2P$ and $3P$ states are about $1.7 \times 10^{-4}$ and
$2.3 \times 10^{-4}$ respectively. Thus the direct production of the $P$-wave
states via fragmentation may account for a significant fraction of the
inclusive production rate of the $B_c$ at large transverse momentum in high
energy colliders. Our analytic results for the $P$-wave fragmentation functions
disagree with those obtained earlier in the literature.


title: Anomalous Vector-Boson Couplings in Majorana Neutrino Models

abstract:
  We examine the contributions of Majorana neutrinos to CP-violating WWZ and
ZZZ self-couplings, using a model in which sterile neutrinos couple to the W
and Z by mixing with a fourth-generation heavy lepton. We find that the induced
form factors can be as large as 0.5%. The model satisfies all phenomenological
bounds in a natural way, including those due to the strong limits on the
neutron and electron electric dipole moments. Anomalous CP-odd couplings of
this size are unlikely to be observed at LEP200, but might be detectable at
NLC.


title: Non-Equilibrium Quantum Field Evolution in FRW Cosmologies

abstract:
  We derive the effective equations for the out of equilibrium time evolution
of the order parameter and the fluctuations of a scalar field theory in
spatially flat FRW cosmologies. After setting the problem in general we propose
a non-perturbative, self-consistent Hartree approximation. The method consists
of evolving an initial functional thermal density matrix in time and is
suitable for studying phase transitions out of equilibrium. The renormalization
aspects are studied in detail and we find that the counterterms depend on the
initial state. We investigate the high temperature expansion and show that it
breaks down at long times. The infinite time limit is computed for de Sitter
spacetime. We obtain the time evolution of the initial Boltzmann distribution
functions, and argue that in the Hartree approximation, the time evolved state
is a ``squeezed'' state. We illustrate the departure from thermal equilibrium
by studying the case of a free field in de Sitter and radiation dominated
cosmologies. It is found that a suitably defined non-equilibrium entropy per
mode increases linearly with comoving time in a de Sitter cosmology, whereas it
is {\it not} a monotonically increasing function in the radiation dominated
case. This work has been done in collaboration with D. Boyanovsky and R.
Holman.


title:
Classical and Quantum Coherent State Description of Nucleon-Antinucleon
  Annihilation at Rest in the Skyrme Model with Omega Mesons

abstract:
  We model the $N\bar{N}$ system at rest as a baryon number zero lump in the
Skyrme model including the $\omega$ field. We integrate the classical equations
of motion from the highly non-perturbative annihilation region into the
non-interacting radiation zone. Subsequent coherent state quantization of the
radiation field gives a good description of the pion spectrum from annihilation
at rest.


title: Non-Equilibrium Quantum Fields in the Large N Expansion

abstract:
  An effective action technique for the time evolution of a closed system
consisting of one or more mean fields interacting with their quantum
fluctuations is presented. By marrying large $N$ expansion methods to the
Schwinger-Keldysh closed time path (CTP) formulation of the quantum effective
action, causality of the resulting equations of motion is ensured and a
systematic, energy conserving and gauge invariant expansion about the
quasi-classical mean field(s) in powers of $1/N$ developed. The general method
is exposed in two specific examples, $O(N)$ symmetric scalar $\l\F^4$ theory
and Quantum Electrodynamics (QED) with $N$ fermion fields. The $\l\F^4$ case is
well suited to the numerical study of the real time dynamics of phase
transitions characterized by a scalar order parameter. In QED the technique may
be used to study the quantum non-equilibrium effects of pair creation in strong
electric fields and the scattering and transport processes in a relativistic
$e^+e^-$ plasma. A simple renormalization scheme that makes practical the
numerical solution of the equations of motion of these and other field theories
is described.


title: Weak Decays of Heavy-Quark Systems

abstract:
  The recent theoretical progress in the description of semileptonic decays in
the framework of the heavy mass expansion is summarized. Both inclusive and
exclusive decays are considered.


title:
Inclusion of Z->b b-bar vertex corrections in Precision Electroweak
  Tests on the Sp(6)_L X U(1)_Y Model

abstract:
  We extend our previous work on the precision electroweak tests in the Sp(6)_L
X U(1)_Y family model to include for the first time the important Z->b b-bar
vertex corrections encoded in a new variable epsilon_b, utilizing all the
latest LEP data. We include in our analysis the one loop EW radiative
corrections due to the new bosons in terms of epsilon_1, epsilon_b and
$\Delta\Gamma_Z$. We find that the correlation between epsilon_1 and epsilon_b
makes the combined constraint much stronger than the individual ones. The model
is consistent with the recent CDF result of $m_t=174\pm 10^{+13}_{-12}\GeV$,
but it can not accomodate $m_t\gsim 195\GeV$.


title: Scanning the BFKL pomeron in elastic production of vector mesons at HERA

abstract:
  Elastic production of vector mesons $\gamma^{*} N\to V N$ is the
pomeron-exchange dominated diffractive reaction with much potential of probing
the BFKL pomeron. The BFKL pomeron can conveniently be described in terms of
the dipole cross section which is a solution of the generalized BFKL equation.
In this paper we discuss, how the energy and $Q^{2}$ dependence of elastic
production of vector mesons at HERA will allow scanning the dipole cross
section as a function of dipole size $r$. We show that determinaton of the
intercept of the BFKL pomeron requires measuring the $\rho^{0}$ and $J/\Psi$
production at $Q^{2} \sim (100-200)GeV^2$ and/or the quasireal photoproduction
of the $\Upsilon$. We present predictions for the effective intercept in the
kinematic range of the forthcoming HERA experiments, which can shed much light
on the nonperturbative component of the pomeron.


title:
Fermion Mass Postdictions in a Generalized Extended Technicolour
  Scenario

abstract:
  We review the recent discussion in the literature of one family extended
technicolour models with techni-fermion mass spectra compatible with the
experimental data for the precision parameters S,T,U,V, W and X and ETC
interactions compatible with the LEP measurements of the $Z\to b{\bar b}$
vertex. To investigate whether these scenarios are consistent with the third
family fermion masses we develop a generalized ETC model in which ETC
interactions are represented by four Fermi interactions. We discuss in detail
the reliability of the gap equation approximation to the non-perturbative
dynamics. Two generic scenarios of couplings fit the precision data and third
family masses; one is an unpredicitive existence proof, the other, which
generates the large top mass by direct top condensation, has a minimal number
of interactions that break the global symmetry of the light fermions in the
observed manner. This latter scenario makes surprisingly good predictions of
the charm, strange and up quark masses.


title: Realistic Superstring Models

abstract:
  I discuss the construction of realistic superstring standard--like models in
the four dimensional free fermionic formulation. I discuss the massless
spectrum of the superstring standard--like models and the texture of fermion
mass matrices. These models suggest an explanation for the top quark mass
hierarchy. At the cubic level of the superpotential only the top quark get a
mass term. The lighter quarks and leptons obtain their mass terms from
nonrenormalizable terms that are suppressed relative to the cubic order term. A
numerical estimate yielded $m_t\sim175-180~GeV$. The suppression of the
lightest generation masses results from the horizontal symmetries in the
superstring models. The problems of neutrino masses, gauge coupling unification
and hierarchical SUSY breaking are discussed. I argue that the realistic
features of these models are due to the underlying $Z_2\times Z_2$ orbifold,
with standard embedding, at the free fermionic point in toroidal
compactification space.


title: Hints of Grand Unification in Neutrino Data

abstract:
  There are strong indications for neutrino masses and mixings in the data on
solar neutrinos, the observed deficit of the muon neutrinos from the atmosphere
as well as the discussions of the dark matter of the universe after COBE data.
It is argued that the SO(10) grand unified has the right symmetry breaking
properties as dictated by LEP data to accomodate the neutrino masses and
mixings suggested by these experiments. Predictions for neutrino masses in two
different versions of the model are discussed.


title: Electroweak Physics Issues at a High Energy Photon Collider

abstract:
  The main attractions of studying the bosonic sector of the electroweak
standard model and its extensions at a future high energy photon collider are
reviewed. A presentation of the laser scheme for obtaining such a collider is
given where we emphasize the importance of polarised \gag spectra. The need for
{\em measuring} the differential luminosities is stressed. We show that, in a
large variety of processes, the yield of weak vector bosons is much higher than
at the \epm mode but unfortunately, the cross sections are dominated by the
transverse modes. Investigation of the physics related to the symmetry breaking
sector both in $W$ and $Z$ pair production is given and contrasted with what we
expect to obtain in the \epm mode and at the LHC. We reassess the issue of
whether an intermediate-mass Higgs can be observed as a resonance when we have
a broad spectrum that allows the simultaneous study of a host of electroweak
phenomena. This investigation includes the important background of the
so-called ``resolved" photon. We analyse the important issues of the mass
resolution, the $b$ tagging efficiencies, and the polarisation of the beams at
two typical \epm energies: 300GeV and 500GeV. New efficient cuts are found to
suppress the background. The importance of $WWH$ production at $\sim$1TeV is
emphasized and contrasted with other Higgs production mechanisms at both \epm
and $e\gamma$. Finally, we examine the interesting problem of the longitudinal
$W$ ($W_L$) content of the photon. A new set of polarised structure functions
for the $W_L$ inside the photon is proposed. We test the validity of the
ensuing effective $W$ approximation in the \ggwwht process.


title:
On the 1/m^2 corrections to the form-factors in /\_b -> /\_c
  semileptonic decays

abstract:
  Model-independent bounds are presented for the form-factors describing the
semileptonic decay $\Lambda_b\to\Lambda_ce\bar\nu_e$ at the end-point of the
lepton energy spectrum. For the axial-vector form-factor $f_1^A(1)$ we obtain
$f_1^A(1)\leq 0.960\div 0.935$, where the uncertainty arises from the value of
$\mu_\pi^2$, the average kinetic energy of the $b$ quark inside of the
$\Lambda_b$ baryon. A bound is given on the forward matrix element of the axial
current in a $\Lambda_b$ baryon which is relevant for the inclusive
semileptonic decays of the polarized $\Lambda_b$ decays.


title: Relations among Zero Momentum Correlators for Heavy-Light Systems in QCD

abstract:
  Relations connecting various zero momentum correlators of interpolating
fields for pseudoscalar and scalar channel, containing one heavy and one light
quark field, are derived from the Euclidean space formulation of the QCD
functional integral. These relations may serve as constraints on the
phenomenological models or approaches motivated from QCD, and suggest a method
to extract the chiral quark condensates. It is also found that the correlator
for pseudoscalar channel differs from that for scalar channel even in the large
heavy quark mass limit.


title: What is the Equivalence Theorem Really?

abstract:
  The precise statement of the equivalence theorem, between the longitudinally
polarized states of a massive gauge boson and the corresponding goldstone mode,
is discussed when the amplitude in question depends on masses of other
particles (e.g., the Higgs boson) in the theory.


title: Dark Matter from Supersymmetric Grand Unification

abstract:
  In constrained minimal supersymmetry the lightest neutralino of bino-type is
the only neutral candidate for dark matter. As a result, one is typically able
to restrict all the supersymmetric mass spectra below roughly 1-2\tev\ {\em
without} imposing an ill-defined fine-tuning constraint.


title: Upper Bounds in Low-Energy SUSY

abstract:
  In the constrained MSSM one is typically able to restrict the supersymmetric
mass spectra below roughly 1-2\tev\ {\em without} resorting to the ambiguous
fine-tuning constraint.


title: Quark Diffusion and Baryogenesis at the Electroweak Phase Transition

abstract:
  Baryogenesis at the electroweak phase transition may take place through
CP-violating reflections of quarks from expanding bubbles of the broken
symmetry phase. We formulate and approximately solve the transport equations
for the reflected quark asymmetries. The results are comparable to a previous
Monte Carlo calculation and allow for analytic estimates of the baryon
asymmetry $\Delta B$ when the bubble walls have a small velocity. Our method
predicts no velocity-dependence for $\Delta B$ in the small $v$ limit, unlike
results obtained from a simplified treatment based on the diffusion equation.


title: Pion-Nucleon Scattering in a Large-N Sigma Model

abstract:
  We review the large-N_c approach to meson-baryon scattering, including recent
interesting developments. We then study pion-nucleon scattering in a particular
variant of the linear sigma-model, in which the couplings of the sigma and pi
mesons to the nucleon are echoed by couplings to the entire tower of I=J
baryons (including the Delta) as dictated by large-N_c group theory. We sum the
complete set of multi-loop meson-exchange
  \pi N --> \pi N and \pi N --> \sigma N Feynman diagrams, to leading order in
1/N_c. The key idea, reviewed in detail, is that large-N_c allows the
approximation of LOOP graphs by TREE graphs, so long as the loops contain at
least one baryon leg; trees, in turn, can be summed by solving classical
equations of motion. We exhibit the resulting partial-wave S-matrix and the
rich nucleon and Delta resonance spectrum of this simple model, comparing not
only to experiment but also to pion-nucleon scattering in the Skyrme model. The
moral is that much of the detailed structure of the meson-baryon S-matrix which
hitherto has been uncovered only with skyrmion methods, can also be described
by models with explicit baryon fields, thanks to the 1/N_c expansion.


title: Renormalization scale uncertainty in tne DIS 2+1 jet cross-section

abstract:
  The deep inelastic scattering 2+1 jet cross- section is a useful observable
for precision tests of QCD, e.g. measuring the strong coupling constant
alpha(s). A consistent analysis requires a good understanding of the
theoretical uncertainties and one of the most fundamental ones in QCD is due to
the renormalization scheme and scale ambiguity. Different methods, which have
been proposed to resolve the scale ambiguity, are applied to the 2+1 jet
cross-section and the uncertainty is estimated. It is shown that the
uncertainty can be made smaller by choosing the jet definition in a suitable
way.


title:
Precise Determinations of the CKM Matrix from CP-Asymmetries in B-Decays
  and K_L --> \pi^0 \nu \bar\nu

abstract:
  We point out that the measurements of the CP asymmetries in neutral B-decays
together with a measurement of $Br(K_L\to \pi^\circ\nu\bar\nu)$ and the known
value of $\mid V_{us}\mid $ can determine {\it all} elements of the
Cabibbo-Kobayashi-Maskawa matrix without essentially any hadronic
uncertainties. In particular the strong dependence of $Br(K_L\to
\pi^\circ\nu\bar\nu)$ on $\mid V_{cb}\mid$ ($\mid V_{cb}\mid^4$) can be used to
determine this element precisely. Consequently $\mid V_{ub}\mid$, $\mid
V_{td}\mid$ and $\mid V_{ts} \mid $ can also be determined. We derive a set of
formulae which facilitate this study and we present a numerical analysis of
several future scenarios. Accurate determinations of all parameters are
expected from the B-factories and the Main Injector era at Fermilab including
KAMI. An impressive accuracy should be reached in the LHC era. An analysis
using $Br(\kpnn)$ instead of $Br(\klpnn)$ shows that although the determination
of $\mid V_{cb}\mid$ and $\mid V_{td}\mid$ this way is less accurate, still
useful results for these elements can be obtained.


title: Enhancing the top signal at Tevatron using Neural Nets

abstract:
  We show that Neural Nets can be useful for top analysis at Tevatron. The main
features of $t\bar t$ and background events on a mixed sample are projected in
a single output, which controls the efficiency and purity of the $t\bar t$
signal.


title:
Relativistic mass distribution in event-anti-event system and
  ``realistic'' equation of state for hot hadronic matter

abstract:
  We find the equation of state $p,\rho \propto T^6,$ which gives the value of
the sound velocity $c^2=0.20,$ in agreement with the ``realistic'' equation of
state for hot hadronic matter suggested by Shuryak, in the framework of a
covariant relativistic statistical mechanics of an event--anti-event system
with small chemical and mass potentials. The relativistic mass distribution for
such a system is obtained and shown to be a good candidate for fitting hadronic
resonances, in agreement with the phenomenological models of Hagedorn, Shuryak,
{\it et al.} This distribution provides a correction to the value of specific
heat 3/2, of the order of 5.5\%, at low temperatures.


title: Next-to-leading-order temperature corrections to correlators in QCD

abstract:
  Corrections of order $T^4$ to vector and axial current correlators in QCD at
a finite temperature $T<T_c$ are obtained using dispersion relations for the
amplitudes of deep inelastic scattering on pions. Their relation with the
operator product expansion is presented. An interpretation of the results in
terms of $T$-dependent meson masses is given: masses of $\rho$ and $a_1$ start
to move with temperature in order $T^4$.


title: An Automatic Invisible Axion In The SUSY Preon Model

abstract:
  It is shown that the recently proposed preon model which provides a unified
origin of the diverse mass scale and an explanation of family replication as
well as of inter-family mass-hierarchy, possesses a Peccei-Quinn symmetry whose
spontaneous breaking leads to an automatic invisible axion. Existence of the
PQ-symmetry is simply a consequence of supersymmetry and requirement of
minimality in the field-content and interactions, which propose that the
lagrangian should possess only those terms which are dictated by the gauge
principle and no others. In addition to the axion, the model also generates two
superlight Goldstone bosons and their superpartners which are cosmologically
safe.


title: Source Dimensions in Ultrarelativistic Heavy Ion Collisions

abstract:
  Recent experiments on pion correlations, interpreted as interferometric
measurements of the collision zone, are compared with models that distinguish a
prehadronic phase and a hadronic phase. The models include prehadronic
longitudinal expansion, conversion to hadrons in local kinetic equilibrium, and
rescattering of the produced hadrons. We find that the longitudinal and outward
radii are surprisingly sensitive to the algorithm used for two-body collisions.
The longitudinal radius measured in collisions of 200 GeV/u sulfur nuclei on a
heavy target requires the existence of a prehadronic phase which converts to
the hadronic phase at densities around 0.8-1.0 GeV/fm$^3$. The transverse radii
cannot be reproduced without introducing more complex dynamics into the
transverse expansion.


title: Fermion Masses from Superstring Models with Adjoint Scalars

abstract:
  We explore the possibility of embedding supersymmetric GUT texture ideas into
superstring models. We discuss the construction of GUT models using free
fermionic strings. We find SO(10) models with adjoint scalars, three
generations of chiral fermions, and a fundamental Higgs with a Yukawa coupling
to only the third generation.


title: Defining the Nambu--Jona-Lasinio Model by Higher Derivative Kinetic Term

abstract:
  Usual treatment of the Nambu--Jona-Lasinio (NJL) model using loop momentum
cutoff suffers from ambiguities in choosing the loop momenta to be cut off and
violation of (external) gauge invariance. We define the NJL model from the
starting Lagrangian level by using a higher derivative fermion kinetic term
with a cutoff parameter $\Lambda$. This definition is free from such
ambiguities and manifestly keeps the chiral symmetry as well as the gauge
invariance. Quantization of this higher derivative system, current operators
and calculational method are discussed in some detail. Calculating the pion
decay constant and $\pi^0\rightarrow 2\gamma$ decay amplitude, we explicitly
demonstrate that the low energy theorem holds. It is observed that the NJL mass
relation $m_\sigma = 2 m_0$ between the $\sigma$ meson and fermion masses no
longer holds in this model. We also present a simplified calculational method
which is valid when the cutoff parameter $\Lambda $ is much larger than the
energy scale of physics.


title: Spin Formalism and Applications to New Physics Searches

abstract:
  An introduction to spin techniques in particle physics is given. Among the
topics covered are: helicity formalism and its applications to the decay and
scattering of spin-1/2 and spin-1 particles, techniques for evaluating helicity
amplitudes (including projection operator methods and the spinor helicity
method), and density matrix techniques. The utility of polarization and spin
correlations for untangling new physics beyond the Standard Model at future
colliders such as the LHC and a high energy $e^+e^-$ linear collider is then
considered. A number of detailed examples are explored including the search for
low-energy supersymmetry, a non-minimal Higgs boson sector, and new gauge
bosons beyond the $W^\pm$ and $Z$.


title:
QCD CORRECTIONS TO THE H+ -->t anti-b decay within the minimal
  supersymmetric standard model

abstract:
  I present the results of the QCD corrections to the H+ --> t anti-b decay
within the minimal supersymmetric standard model, if gluinos and scalar quarks
are taken within the relevant loop diagram. I include the mixing of the scalar
partners of the left- and right-handed top quark, which is proportional to the
top quark mass. The standard corrections via gluons and quarks are about +8%
for a charged Higgs mass of 300 GeV and about -11% for a Higgs mass of 800 GeV.
I show that the standard corrections are diminished or enhanced by a
non-negligible amount for certain values of the supersymmetric parameter space.
I also obtain sign changes.


title: Baryon and lepton number transport in electroweak phase transition

abstract:
  We consider the baryon number generation by charge transport mechanism in the
electroweak phase transition taking properly into account thermal fluxes
through the wall separating true and false vacuum in the spatial space. We show
that the diffusion from the true vacuum to the false one has a large
diminishing effect on the baryon number unless the wall velocity is near to,
but less than, the speed of sound in the medium and the ratio between the
collision rate and wall thickness is about 0.3. The maximum net baryon density
generated is $\rho_B/s\simeq 0.2\times 10^{-10}$, where $s$ is the entropy
density of the Universe. If the wall proceeds as a detonation, no baryon number
is produced.


title:
Energy Losses (Gains) of Massive Coloured Particles in Stochastic Colour
  Medium

abstract:
  The propagation of massive coloured particles in stochastic background
chromoelectric field is studied using the semiclassical equations of motion.
Depending on the nature of the stochastic background we obtain the formulae for
the energy losses of heavy coloured projectile in nonperturbative hadronic
medium and for the energy gains in the stochastic field present, e.g., in the
turbulent plasma. The result appears to be significantly dependent on the form
of the correlation function of stochastic external field


title:
EEWW: a generator for $e^+e^- \to W^+W^-$ including one-loop and leading
  photonic two-loop corrections

abstract:
  We describe a generator for the process $e^+e^- \to W^+W^-$ including all
one-loop and leading log photonic two-loop contributions. It includes
polarization of the beam and $W$ bosons, and the possibility to study the
effect of anomalous couplings.


title:
Addendum To Our Paper: "Radiative Tau Decays With One Pseudoscalar
  Meson"

abstract:
  In a previous paper we have calculated the decay $\tau\to\pi\nu_\tau\gamma$.
We used a given relative sign between the internal bremsstrahlung and the
structure dependent radiation, which has been used by several other authors
before. However, we believe that there are good arguments why the opposite sign
is the physical one. We briefly discuss these arguments and then investigate
how the predictions for the decay $\tau\to\pi\nu_\tau\gamma$ are affected by
this sign.


title: Updated Limits on Visibly and Invisibly Decaying Higgs Bosons from LEP

abstract:
  Talk presented at the XXIX Rencontres de Moriond, Electroweak Interactions
and Unified Theories, March 12-19, 1994, Meribel


title: Parton Equilibration in Ultrarelativistic Heavy Ion Collisions

abstract:
  Medium effects which include color screening and Landau-Pomeranchuk-Migdal
suppression of induced radiation are discussed in connection with the
equilibration of dense partonic system in ultrarelativistic heavy ion
collisions. Taking into account of these medium effects, the equilibration rate
for a gluonic gas are derived and the consequences are discussed.


title:
Heavy Quark Production at $e^+ e^-$ Colliders in Multijet Events and a
  New Method of Computing Helicity Amplitudes

abstract:
  Heavy quark production in multijet events at $e^+e^-$ colliders is studied at
tree level. Total production rates are given and compared with the
corresponding results for massless quarks. A new method of computing helicity
amplitudes is briefly sketched. Talk presented at the XXIXth Rencontres de
Moriond, QCD and High Energy Hadronic Interactions, Meribel, France, March
19-26 1994.


title: Dark Matter and Structure Formation with Late Decaying Particles

abstract:
  Since it became evident that the CDM model for cosmic structure formation
predicts smaller power on large scales than observed, many alternatives have
been suggested. Among them, the existence of late decaying particle can cure it
by delaying the beginning of the matter domination and increasing the horizon
length at that time. We discuss the realization of this scenario and present
the light neutrino and the light axino as possible examples of working particle
physics model. We point out that the increased power at sub-galaxy scale
predicted by this scenario could lead to rich sub-galaxy structures.


title:
One-loop radiative corrections to the helicity amplitudes of QCD
  processes involving four quarks and one gluon

abstract:
  We present analytic results for the one-loop corrections of the helicity
amplitudes of the QCD five-parton subprocesses involving four quarks and one
gluon obtained with a standard Feynman diagram calculation using dimensional
reduction.


title: Multisphalerons in the Weinberg-Salam Theory

abstract:
  We construct multisphaleron solutions in the Weinberg-Salam theory. The
multisphaleron solutions carry Chern-Simons charge $n/2$, where $n$ is an
integer, counting the winding of the fields in the azimuthal angle. The
well-known sphaleron has $n=1$. The multisphalerons possess axial symmetry and
parity reflection symmetry. We vary the Higgs mass and the mixing angle. For
small $n$ the energies of the multisphalerons are on the order of $n$ times the
energy of the sphaleron and their magnetic dipole moments are on the order of
$n$ times the magnetic dipole moment of the sphaleron.


title:
High-Energy Factorization and Small-X Deep Inelastic Scattering Beyond
  Leading Order

abstract:
  High-energy factorization in QCD is investigated beyond leading order and its
relationship to the factorization theorem of mass singularities is established
to any collinear accuracy. Flavour non-singlet observables are shown to be
regular at small x order by order in perturbation theory. In the singlet
sector, we derive the relevant master equations for the space-like evolution of
gluons and quarks. Their solution enables us to sum next-to-leading corrections
to the small-x behaviour of quark anomalous dimensions and deep inelastic
scattering coefficient functions. We present results in both MSbar and DIS
factorization schemes.


title: Inflation, Supergravity and Superstrings

abstract:
  The positive potential energy required for inflation spontaneously breaks
supersymmetry and in general gives any would-be inflaton an effective mass of
order the inflationary Hubble parameter thus ruling it out as an inflaton. In
this paper I give simple conditions on the superpotential that eliminate some
potential sources for this mass, and derive a form for the Kahler potential
that eliminates the rest. This reduces the problem of constructing a model of
inflation in supergravity to that of constructing one in global supersymmetry
with the extra conditions $W=W_\varphi=\psi=0$ during inflation (where $W$ is
the superpotential, the inflaton $\in\varphi$, and $W_\psi\neq0$). I then point
out that Kahler potentials of the required form often occur in superstrings and
that the target space duality symmetries of superstrings often contain
R-parities which would make $W=W_\varphi=0$ automatic for $\psi=0$.


title: A Simple Way to Estimate the Value of $\bar{\alpha}\equiv\alpha(m^2_Z)$

abstract:
  To obtain the value of electromagnetic coupling constant at $q^2=m^2_Z$,
$\bar{\alpha}$, which plays a key role in electroweak physics one has to
integrate the cross-section of $e^+e^-$-annihilation into hadrons divided by
$(s-m^2_Z)$ over $s$ from threshold to infinity. By combining, for each flavor
channel, the contribution of lowest resonance with the perturbative QCD
continuum, we obtain $1/\bar{\alpha} = 128.90\pm 0.06 $ a result which is close
to known result obtained with purely experimental inputs, i.e. $1/\bar{\alpha}
= 128.87\pm 0.12$.


title: Probing Anomalous Chromomagnetic Top Quark Couplings at the NLC

abstract:
  The Next Linear Collider(NLC) will provide a excellent tool for probing the
detailed nature of the top quark. By extending the recent analysis of
Dokshitzer, Khoze and Sterling, we perform a preliminary examination of the
influence of an anomalous chromomagnetic moment for the top, $\kappa$, on the
spectrum of gluon radiation associated with $t\bar t$ production. In
particular, we analyze the sensitivity of future data to non-zero values of
$\kappa$ and estimate the limits that can be placed on this parameter at the
NLC with center of mass energies $\sqrt {s}=$ 500 and 1000 GeV.


title: Predicting the Masses of Heavy Hadrons without an Explicit Hamiltonian

abstract:
  There are striking regularities in the masses and mass differences of known
hadrons. Some of these regularities can be understood from known general
properties of the interactions of quarks without a need to specify the explicit
form of the Hamiltonian. The Feynman--Hellmann theorem is one of the tools
providing this understanding. If the mass regularities are exploited,
predictions can be made of the masses of as yet undiscovered hadrons. In
particular, it is found that the mass of the $B_c^*$ is $6320\pm 20$ MeV.
Predictions concerning i) excited vector mesons, ii) pseudoscalar mesons, iii)
$P$-wave mesons, and iv) ground-state spin 1/2 and 3/2 baryons are also made.


title: Constructing QCD Loop Amplitudes Using Collinear Limits

abstract:
  We discuss how higher-point QCD amplitudes may be constructed from lower
point ones by imposing the factorization constraints in the limits as external
momenta become collinear. As a particular example, the all-$n$ gluon one-loop
amplitude with maximal helicity violation is presented. We also discuss the
necessary collinear behavior of the $n$-gluon amplitudes.


title: Two--loop heavy Higgs corrections to the Higgs fermionic width

abstract:
  We calculate the two--loop electroweak corrections to the fermionic decay
width of the Higgs boson at leading order in $m_{H}$. The sum of one--loop and
two--loop radiative corrections turns out to be at 6% level over the whole
range of $m_{H}$ where the perturbation theory is supposed to be a sensible
approximation. We show that the perturbative approach breaks down at $m_{H}
\sim$ 1.4 TeV, and address the question of its relevance beyond this limit.


title: Radiative Majorana Neutrino Masses

abstract:
  We present new radiative mechanisms for generating Majorana neutrino masses,
within an extension of the standard model that successfully generates radiative
charged lepton masses, order by order, from heavy sequential leptons. Only the
new sequential neutral lepton has a right-handed partner, and its Majorana mass
provides the seed for Majorana neutrino mass generation. Saturating the
cosmological bound of $50$ eV with $m_{\nu_\tau}$, we find that $m_{\nu_\mu}$
and $m_{\nu_e}$ could be at most $10^{-2}$, and $10^{-3}$ eV, respectively. The
electron neutrino mass may vanish in the limit of degenerate charged Higgs
bosons. Unfortunately, $\nu_e - \nu_\tau$ mixing is also radiatively induced,
and is too small for sake of solving the solar neutrino problem via the
Mikheyev--Smirnov--Wolfenstein effect.


title:
Problems of Perturbation Series in Non-Equilibrium Quantum Field
  Theories

abstract:
  In the standard framework of non-equilibrium quantum field theories, the
pinch singularities associated to multiple products of $\delta$-functions do
not cancel in a perturbative expansion unless the particle distributions are
those for a system in thermal and chemical equilibrium.


title:
Unitarity Constraints for the Mass of the Higgs in the $SU(2)_L\otimes
  U(1)\otimes U(1)'$ Gauge Model

abstract:
  The critical values for the mass of the Higgs bosons, at which the theory
becomes strongly interacting, are calculated using the equivalence theorem, at
high energies this allows us to replace the longitudinally polarized gauge
bosons in the $S$ matrix for the corresponding Goldstone bosons. An appropriate
ansatz for defining the would-be Goldstone bosons in the case of an additional
neutral current, beyond the minimal standard model, is also presented.


title:
Initial-state QED corrections to four-fermion production in e+e-
  collisions at LEP200 and beyond

abstract:
  The implementation of QED initial-state radiative corrections in the process
of four-fermion production at LEP200 and higher-energy e+e- colliders is
discussed. Because of the presence of charged-current processes, this is a
nontrivial problem, and we compare our approach with other existing treatments.
We describe the Monte Carlo algorithm used for the generation of 4-fermion
events with photon bremsstrahlung. Comparison between our event generator and
semi-numerical calculations are presented, as well as predictions for W and Z
pair related cross sections.


title:
Neutrino Masses and $b-\tau$ unification in the Supersymmetric Standard
  Model

abstract:
  There are several indications that the Majorana masses of the right-handed
neutrino components, $M_R,$ are at the intermediate scale: $M_R\sim
(10^{10}-10^{12})$ GeV or even lighter. The renormalization effects due to
large Yukawa couplings of neutrinos from region of momenta $M_R \ltap q \ltap
M_G$ are studied in the supersymmetric standard model. It is shown that
neutrino renormalization effect can increase the $m_b/m_\tau$ ratio up to
$(10\div 15)\%.$ This strongly disfavours $m_b-m_\tau$ unification for low
values of $\tan\beta < 10$ especially at large values of $\alpha_s.$ Lower
bounds on $M_R$ and $\tan\beta$ from the $b-\tau$ unification condition were
found. The implications of the results to the see-saw mechanism of the neutrino
mass generation are discussed.


title: Transverse Energy Flow at HERA

abstract:
  We calculate the transverse energy flow accompanying small $x$ deep-inelastic
events and compare with recent data obtained at HERA. In the central region
between the current jet and the remnants of the proton we find that BFKL
leading $\ln(1/x)$ dynamics gives a distinctively large transverse energy
distribution, in approximate agreement with recent data.


title:
Three-jet final states and measuring the $\gamma\gamma$ width of the
  Higgs at a photon linear collider

abstract:
  The identification of the intermediate-mass Higgs process $\gamma\gamma\to H
\to b \bar b$ will be one of the most important goals of a future photon linear
collider. Potentially important backgrounds from the continuum $\gamma\gamma
\to c \bar c, b \bar b$ leading-order processes can be suppressed by a factor
$m_q^2/s$ by using polarized photon beams in the $J_z=0$ initial-state
configuration. We show that the same $m_q^2/s$ suppressions do not necessarily
apply to the radiative processes $\gamma\gamma \to c \bar c g, b \bar b g$.
These processes can mimic the two-jet topology of the Higgs signal when two of
the three partons are collinear, or when one of the partons is soft or directed
down the beam pipe. We calculate the contribution of these processes to the
two-jet background in the $J_z=0$ channel. We investigate the effect of
imposing additional event shape, jet width and secondary vertex cuts on both
signal and background, and show that with reasonable detector capabilities it
should be possible to reduce the background to a manageable level.


title: Vacuum Structure and Chiral Symmetry Breaking

abstract:
  We relate here the vacuum structure of chiral symmetry breaking to a wide
class of low energy hadronic properties to examine consistency with
experimental results. Phase transition of chiral symmetry breaking is described
through explicit vacuum realignment. We find that for the present ansatz,
vacuum structure of the light quark sector can be determined from $f_\pi=92$
MeV, which then yields that $\Gamma(\pi^0\rightarrow 2 \gamma)=8.3$ eV and,
$R_{ch}=0.67$ fms, in agreement with experiments. This amounts to three
independent `observations' of the vacuum structure of the light quark sector.
For the calculation of $\Gamma(\pi^0\rightarrow 2\gamma)$, we do not use the
anomaly equation - local gauge invariance for vacuum realignment becomes
adequate. The above width is sensitive to the vacuum structure, and can give
evidence regarding progress towards chiral symmetry restoration in QGP. The
corresponding results for $s$ quark sector are moderately good. We also exploit
similar ideas for heavy quarks, but here the experimental data are rare, and
the theoretical techniques are likely to need refinements.


title: Dispersive Methods and QCD Sum Rules for \gamma \gamma Collisions

abstract:
  It has been shown, in the case of meson photoproduction, that the power-law
falloff of these reactions can be described by lowest order (real) sum rules,
at moderate momentum transfer. The phases of these processes, in this regime,
are usually thought to be non-perturbative. In a sum rule framework, however,
they can possibly be described by radiative corrections to the hadronic
spectral densities of the corresponding helicities, which become complex
functions to order $\alpha_s$, and the effects of interference can be strongly
enhanced by the presence of the vacuum condensates in the dispersion relation.
It is shown that the imaginary parts of these complex corrections have a
factorized form and can be evaluated in a systematic fashion, while their real
parts, at the same perturbative order, are down by at least 2 powers of
momentum transfer. The analysis is done at two loop level, combining
dimensional regularization and light-cone methods. The calculations are
performed for all the independent set of scalar diagrams generated by the OPE.
The analytical bounds are identified and discussed.


title: CKM Matrix Elements: Magnitudes, Phases, Uncertainties

abstract:
  Schemes for fermion masses should predict elements of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix. We review the freedom allowed by
present experiments and how the parameter space will shrink in the next few
years. In addition to experiments which directly affect CKM parameters, we
discuss constraints arising from precise electroweak tests.


title: Neutrino Decay in the Doublet Majoron Model

abstract:
  A new Majoron model is presented within the framework of the seesaw
mechanism. Its Higgs sector consists of only doublet representations and the
lepton-number violation takes place at the same scale of the electroweak
symmetry breaking. This model is different from the singlet- or triplet-Majoron
model in several respects: it is free from the \(\rho\)-parameter constraint
and it provides moderately fast neutrino decay, but the constraint from the
stellar cooling of red giants is satisfied only with an imposed approximate
symmetry. A \(\tau\) neutrino as heavy as 10 MeV is possible in this model
despite various cosmological and astrophysical constraints.


title: On Testing Local QFT at LHC

abstract:
  We discuss the importance of measuring $\rho= ReF/ImF$ at LHC to test the
forward dispersion relations and local QFT. It is pointed out that at LHC we
can reach a short distance domain that has not been pre-explored by QED. This
is in contrast with all previous tests of the dispersion relations. We argue
that the most likely property of QFT to fail is polynomial boundedness. In a
theory with `fundamental length', R, we study the consequences of having
exponential behavior in the amplitude of the form (exp$\pm i\sqrt{s}\;R)$, as
suggested by different models. We show that such a behavior makes a significant
and measurable contribution to $\rho$ even at energies where $(\sqrt{s}\;R)$ is
still small, O(0.1). Talk delivered at Les Rencontres de Physique de la Vallee
d'Aoste: Results and Perspectives in Particle Physics, La Thuile, Aosta, March
1994.


title: Fragmentation production of J/psi and psi' at the Tevatron

abstract:
  We present a calculation of the charm and gluon fragmentation contributions
to inclusive $J/\psi$ and $\psi'$ production at large transverse momentum at
the Tevatron. For $\psi$ production, we include both fragmentation directly
into $\psi$ and fragmentation into $\chi_c$ followed by the radiative decay
$\chi_c \to \psi + \gamma$. We find that fragmentation overwhelms the
leading-order mechanisms for prompt $\psi$ production at large $p_T$, and that
the dominant contributions come from fragmentation into $\chi_c$. Our results
are consistent with recent data on $\psi$ production from the CDF and D0
experiments. In the case of prompt $\psi'$ production, the dominant mechanism
at large $p_T$ is charm fragmentation into $\psi'$. We find serious
disagreement between our theoretical predictions and recent $\psi'$ data from
the Tevatron.


title: On the vacuum theta angle in Yang-Mills field theories

abstract:
  Recently, MIT group found a numerical solution to non-abelian gauge fields
which is shown to contain non-integer topological number. Using this fact,
V.V.Khoze has argued that the vacuum theta angle is zero. Here, we study this
in a complimentary way--its physical respect. The key point is MIT solution has
an infinite action. Using this, we prove the vacuum theta angle is zero at
semiclassical level.


title: Dual solutions of Yang-Mills field theories in Minkowski space

abstract:
  Using spherical ansatz, we construct dual equations for non-abelian gauge
fields in Minkowski space. The analytically continued instanton is shown to
satisfy the dual equations but assumes a more ansatz. It is not the solution of
MIT second order differential equation. The symmetries of the solution function
space are examined. The relevant physics is reviewed.


title: Sum Rules for Heavy Flavor Transitions in the SV Limit

abstract:
  We show how sum rules for the weak decays of heavy flavor hadrons can be
derived as the moments of spectral distributions in the small velocity (SV)
limit. This systematic approach allows us to determine corrections to these sum
rules, to obtain new sum rules and it provides us with a transparent physical
interpretation; it also opens a new perspective on the notion of the heavy
quark mass. Applying these sum rules we derive a lower bound on the deviation
of the exclusive form factor $F_{B->D^*}$ from unity at zero recoil; likewise
we give a field-theoretical derivation of a previously formulated inequality
between the expectation value for the kinetic energy operator of the heavy
quark and for the chromomagnetic operator. We analyze how the known results on
nonperturbative corrections must be understood when one takes into account the
normalization point dependence of the low scale parameters. Relation between
the field-theoretic derivation of the sum rules and the quantum-mechanical
approach is elucidated.


title:
Flavour Mixing and Fermion Mass Generation as a Result of Symmetry
  Breaking

abstract:
  It is shown that a simple breaking of the subnuclear democracy leads to a
successful description of the mixing between the second and third family. In
the lepton channel the $\nu _{\mu } - \nu_{\tau }$ oscillations are expected to
be described by a mixing angle of $2.65^ {\circ }$ which might be observed soon
in neutrino experiments.


title:
The Equivalence Theorem for the Heavy-Higgs Standard Model and the
  Gauged Nonlinear Sigma-Model

abstract:
  The equivalence theorem states that the leading part of the amplitude for a
process with external longitudinally polarized vector bosons is given by the
amplitude in which the longitudinal vector bosons are replaced by the
corresponding pseudo-Goldstone bosons. The validity of this theorem within the
standard model with a heavy Higgs boson and within the gauged nonlinear
sigma-model (in which the Higgs boson is absent) is shown. Furthermore it is
examined to what extent also internal lines other than scalar lines can be
neglected. A simple power-counting method is developed which determines the
leading diagrams for a given process at an arbitrary loop order. This method is
also applied to effective Lagrangians with additional nonstandard interaction
terms of higher dimension (chiral Lagragians).


title: An algebraic approach to Z-Factors

abstract:
  We sketch a systematic approach to multiloop calculations. We focus on the
Z-factors of a renormalizable theory and show that they can be obtained by
purely algebraic methods based on power-counting and the forest structure of
the divergent graphs. (submitted contributions to the conference proceedings
"Confronting the Infinite", Adelaide February 1994)


title: Quarkonium Interactions in Hadronic Matter

abstract:
  The cross section for the \J~and \U~interaction with light hadrons is
calculated in short-distance QCD, based on the large heavy quark mass and the
resulting large energy gap to open charm or beauty. The low energy form of the
cross section is determined by the gluon structure functions at large $ x$;
hence it remains very small until quite high energies. This behaviour is
experimentally confirmed by charm photoproduction data. It is shown to exclude
\J~absorption in confined hadronic matter of the size or density attainable in
nuclear collisions; in contrast, the harder gluon spectrum in deconfined matter
allows break-up interactions.