title:
One Loop Corrections To The Lightest Higgs Mass In The Minimal $\eta $
  Model

abstract:
  We have evaluated the one loop correction to the bound on the lightest Higgs
mass valid in the minimal, $ E_{6}$ based, supersymmetric $ \eta$ model. Under
the assumption that the theory remains perturbative up to the $10^{16}$ GeV
scale, we derive a conservative bound that decreases with the top mass for $M_t
\leq 2 M_W$ and varies from $ \sim 160$ GeV to $\sim 145$ GeV when $90 \leq M_t
\leq 200$ GeV.


title: Semileptonic $\pi$ and $K$ Decays and the Chiral Anomaly at One-loop

abstract:
  We calculate the $O(p^6)$ corrections to the anomalous form factors appearing
in $\pi^+$, $K^+ \to e^+ \nu \gamma,\ \mu^+\nu\gamma$ and $K_{l4}$ decays in
Chiral Perturbation Theory. The relevant dimension $6$ terms of the lagrangian
are evaluated assuming their saturation by the vector meson contribution.


title: Vortex Solutions in Two-Higgs Systems and $\tan\beta$

abstract:
  Classical vortex solutions in various two-Higgs systems are studied. The
systems we consider include the standard model with two Higgs doublets, in
which case the vortex appears as part of a string-like object. The Higgs
potentials contain several different couplings in general and the spontaneous
symmetry breaking involves with two different vacuum expectation values. In
particular it is shown that the existence of such a solution in general
requires a specific ratio of the two Higgs vacuum expectation values, i.e.
$\tan\beta$, and some inequalities between different Higgs couplings. This
ratio can be determined in terms of the couplings in the Higgs potential. The
Higgs masses are also computed in this case. (1+2)-d solutions are topological
so that they are topologically stable and the Bogomol'nyi bound is saturated
for some couplings. Some comments on the stabilization of (1+3)-d solutions are
also given. Thus, as long as such a defect can be formed in the early universe,
stable or not, $\tan\beta$ is no longer an independent free parameter in the
theory.


title:
On the Baryon, Lepton-Flavour and Right-Handed Electron Asymmetries of
  the Universe

abstract:
  Non-perturbative electroweak effects, in thermal equilibrium in the early
universe, have the potential to erase the baryon asymmetry of the universe,
unless it is encoded in a B-L asymmetry, or in some "accidentally" conserved
quantity. We first consider the possibility that the BAU may be regenerated
from lepton flavour asymmetries even when initially $B-L = 0$. We show that
provided some, but {\it not} all the lepton flavours are violated by
${\Delta}L{\neq}0$ interactions in equilibrium, the BAU may be regenerated
without lepton mass effects. We next examine the possibility of encoding the
baryon asymmetry in a primordial asymmetry for the right-handed electron, which
due to its weak Yukawa interaction only comes into chemical equilibrium as the
sphalerons are falling out of equilibrium. This would also raise the
possibility of preserving an initial baryon asymmetry when $B-L = 0$.


title: Supersymmetric (S)Neutrino-Mass Induced Baryogenesis

abstract:
  We propose a new mechanism for baryogenesis in supersymmetric extensions of
the standard model, that does not depend on (super)GUT interactions. It occurs
by the non-perturbative electroweak reprocessing of a lepton asymmetry. This
lepton asymmetry is generated by the effects of lepton number violating induced
operators, arising from "see-saw" (s)neutrino masses, which act on scalar
condensate oscillations along flat directions of the supersymmetric standard
model.


title: Inflation, Neutrino Baryogenesis, and (S)Neutrino-Induced Baryogenesis

abstract:
  We evaluate the constraints that the COBE observations put on baryogenesis in
inflationary cosmologies.We consider the supersymmetric version of the proposal
of Fukugita and Yanagida, that the baryon asymmetry of the universe is created
by nonperturbative electroweak reprocessing of a lepton asymmetry generated in
the decay of heavy right-handed see-saw (s)neutrinos. We review our recent
proposal of a mechanism for baryogenesis via sphaleron reprocessing of a lepton
asymmetry generated by (s)neutrino mass effects on flat direction scalar
condensate oscillations. Finally we analyze in detail the implementation of
these mechanisms in the recently proposed ansatze for fermion mass matrices in
supersymmetric, unified, theories.


title:
Radiative Corrections to the Neutral Higgs Spectrum in Supersymmetry
  with a Gauge Singlet

abstract:
  The radiative corrections to the $3\times3$scalar and the $2\times2$
pseudoscalar neutral Higgs boson massmatrices are calculated in the
supersymmetric extension of the standard model including a gauge singlet
superfield in the effective potential approach. The full $t$ and $b$
quark/squark contributions including the nonlogarithmic terms are taken into
account, which are seen to affect the result significantly. An analytic formula
for the upper bound on the mass of the lightest neutral Higgs scalar including
these corrections is given. (Figure available upon request)


title: Higher Order Corrections to Jet Cross Sections in Hadron Colliders

abstract:
  We describe a general method of calculating the fully differential cross
section for the production of jets at next-to-leading order in a hadron
collider. This method is based on a `crossing' of next-to-leading order
calculations with all partons in the final state. The method introduces
universal crossing functions that allow a modular approach to next-to-leading
order calculations for any process with initial state partons. These techniques
are applied to the production of jets in association with a vector boson
including all decay correlations of the final state observables.


title: Inelastic Channels in WW Scattering

abstract:
  If the electroweak symmetry-breaking sector becomes strongly interacting at
high energies, it can be probed through longitudinal $W$ scattering. We present
a model with many inelastic channels in the $W_L W_L$ scattering process,
corresponding to the production of heavy fermion pairs. These heavy fermions
affect the elastic scattering of $W_L$'s by propagating in loops, greatly
reducing the amplitudes in some charge channels. We conclude that the
symmetry-breaking sector cannot be fully explored by using, for example, the
$W_L^\pm W_L^\pm$ mode alone, even when no resonance is present; all $W_L W_L
\to W_L W_L$ scattering modes must be measured.


title: A Natural Solution to the MU Problem

abstract:
  We propose a simple mechanism for solving the $\mu$ problem in the context of
minimal low--energy supergravity models. This is based on the appearance of
non--renormalizable couplings in the superpotential. In particular, if $H_1H_2$
is an allowed operator by all the symmetries of the theory, it is natural to
promote the usual renormalizable superpotential $W_o$ to $W_o+\lambda W_o
H_1H_2$, yielding an effective $\mu$ parameter whose size is directly related
to the gravitino mass once supersymmetry is broken (this result is maintained
if $H_1H_2$ couples with different strengths to the various terms present in
$W_o$). On the other hand, the $\mu$ term must be absent from $W_o$, otherwise
the natural scale for $\mu$ would be $M_P$. Remarkably enough, this is entirely
justified in the supergravity theories coming from superstrings, where mass
terms for light fields are forbidden in the superpotential. We also analyse the
$SU(2)\times U(1)$ breaking, finding that it takes place satisfactorily.
Finally, we give a realistic example in which supersymmetry is broken by
gaugino condensation, where the mechanism proposed for solving the $\mu$
problem can be gracefully implemented.


title:
Z\rightarrow A^0 A^0\nu\bar\nu$ and $e^+e^-\rightarrow A^0 A^0 Z$ in Two
  Higgs Doublet Models

abstract:
  In LEP searches for the neutral CP-odd scalar $A^0$ of a multi-Higgs doublet
model, experimenters have searched for $Z\rightarrow h^0 A^0$ (where $h^0$ is
the lightest CP-even scalar). No model-independent limit on the $A^0$ mass can
be deduced from present data if $m_{h^0}>m_Z$. In this paper, we compute the
rates for $Z\rightarrow A^0 A^0\nu\bar\nu$ and $e^+e^-\rightarrow A^0 A^0 Z$.
Assuming that no light CP-even neutral scalars exist, the branching ratio for
$Z\rightarrow A^0 A^0\nu\bar\nu$ is found to be less than $1.4\times10^{-8}$.
At higher $e^+e^-$ center-of-mass energies, $\sigma(e^+e^-\rightarrow A^0 A^0
Z)$ peaks at $0.5$~fb. A comparison with other direct searches for the $A^0$ is
briefly considered.


title: Neutrino masses from discrete gauge symmetries

abstract:
  We investigate a model with an extra $Z_{2}$ gauge symmetry in the Standard
Model. We assume that only the scalars and the leptons carry non-zero charge.
The symmetry gives a structure to the mass matrix for the neutrinos. With two
extra Higgs singlets and two extra singlet right-handed neutrinos we can build
a model that fits the requirements of the MSW-solution of the Solar neutrino
problem. With a third singlet right-handed neutrino it is also possible to have
a 10 eV neutrino, a dark matter candidate.


title: CP violation in Higgs decays

abstract:
  We study CP violation in fermion pair decays of Higgs boson. We idenfy some
CP odd observables related to the tree level decay amplitude. We find that a
few thousand Higgs boson decay events can already provide important information
about CP violation. If the Higgs boson is produced, such an analysis could be
carried out at the SSC, LHC and NLC.


title: QCD Sum Rule and Perturbative QCD Approaches to Pion Compton Scattering

abstract:
  We compare two approaches to the description of pion Compton scattering at
moderate momentum transfer, one being based on local duality QCD sum rules for
the invariant amplitudes of the process, which have been derived recently, and
the other on the modified factorization formula with Sudakov effects included.
We find that perturbative QCD predictions are dominant over those from QCD sum
rules only for the scattering angle greater than 90$^o$.


title:
Polarized $q\to\Lambda$ Fragmentation Functions from
  $e^+e^-\to\Lambda+X^*$

abstract:
  Measurement of the helicity asymmetric cross section for semi-inclusive
production of $\Lambda$-hyperons in $e^+e^-$ annihilation near the $Z^0$
resonance allows a complete determination of the spin-dependent fragmentation
functions for the different quark flavors into the $\Lambda$. The parity
violating, self analyzing, decay of the final state $\Lambda$ makes the
experimental analysis of the helicity asymmetry possible. This experiment
should be practical with present day technology at the LEP collider at CERN or
at SLC at SLAC.


title: Partition function for the eigenvalues of the Wilson line

abstract:
  In a gauge theory at nonzero temperature the eigenvalues of the Wilson line
form a set of gauge invariant observables. By constructing the corresponding
partition function for the phases of these eigenvalues, we prove that the
trivial vacuum, where the phases vanish, is a minimum of the free energy.


title:
Improved LEP lower bound on the lightest SUSY Higgs mass from Radiative
  Electroweak Breaking and its Experimental Consequences

abstract:
  We show that the present LEPI lower bound on the Standard Model Higgs boson
mass ($M_H\gsim60\GeV$) applies as well to the lightest Higgs boson ($h$) of
the minimal $SU(5)$ and no-scale flipped $SU(5)$ supergravity models. This
result would persist even for the ultimate LEPI lower bound ($M_H\gsim70\GeV$).
We show that this situation is a consequence of a decoupling phenomenon in the
Higgs sector driven by radiative electroweak breaking for increasingly larger
sparticle masses, and thus it should be common to a large class of supergravity
models.
  A consequence of $m_h\gsim60\GeV$ in the minimal $SU(5)$ supergravity model
is the exclusion from the allowed parameter space of `spoiler modes'
($\chi^0_2\to\chi^0_1 h$) which would make the otherwise very promising
trilepton signal in $p\bar p\to\chi^\pm_1\chi^0_2X$ unobservable at Fermilab.
Within this model we also obtain stronger upper bounds on the lighter
neutralino and chargino masses, \ie, $m_{\chi^0_1}\lsim50\GeV$,
$m_{\chi^0_2,\chi^\pm_1}\lsim100\GeV$. This should encourage experimental
searches with existing facilities.


title: Complementarity and Chiral Fermions in SU(2) gauge Theories

abstract:
  Complementarity - the absence of a phase boundary separating the Higgs and
confinement phases of a gauge theory - can be violated by the addition of
chiral fermions. We utilize chiral symmetry violating fermion correlators such
as $ \langle \bps \psi \rangle $ as order parameters to investigate this issue.
Using inequalities similar to those of Vafa-Witten and Weingarten, we show that
SU(2) gauge theories with Higgs and fermion fields in the fundamental
representation exhibit chiral symmetry breaking in the confined phase and
therefore do {\it not} lead to massless composite fermions. We discuss the
implications for the Abbott-Farhi strongly interacting standard model.


title: Baryon Asymmetry, Supersymmetry and Gravitational Anomalies

abstract:
  We discuss two independent issues about the baryon asymmetry of the universe.
First, assuming that it is generated by an unspecified source at high
temperatures, we study the effects of non-perturbative $SU(2)_W$ dynamics above
the electroweak scale, in the context of supersymmetric models. We find that
there is a substantial difference with the nonsupersymmetric case with the net
effect of relaxing previous bounds on B and L violating interactions. In
particular supersymmetry allows neutrino masses as large as 10 eV (preferred by
solar neutrino and COBE data and measurable at future neutrino oscillation
experiments). Second, we argue that the existence of a mixed lepton
number-gravitational anomaly in the standard model will induce B-L violating
interactions. These transitions would be catalized by Einstein-Yang-Mills
instantons or sphalerons and could create a primordial B-L asymmetry at Planck
temperatures or lower. Gravity (and the anomaly structure of the standard
model) could then be the ultimate source of the baryon asymmetry. We analyze
the viability of the presently known gravitational instantons and sphalerons to
realize this scenario. (Talk presented by FQ at the Texas/Pascos Conference,
Berkeley Dec.1992.)


title:
Experimental Constraints on the Neutrino Oscillations and a Simple Model
  of Three Flavour Mixing

abstract:
  A simple model of the neutrino mixing is considered, which contains only one
right-handed neutrino field, coupled via the mass term to the three usual
left-handed fields. This is a simplest model that allows for three-flavour
neutrino oscillations. The existing experimental limits on the neutrino
oscillations are used to obtain constraints on the two free mixing parameters
of the model. A specific sum rule relating the oscillation probabilities of
different flavours is derived.


title: Quark Propagation in the Random Instanton Vacuum

abstract:
  This is the first of a series of papers devoted to a systematic study of QCD
correlation functions in a framework of 'instanton vacuum' models. The topic of
this paper is to work out approximate formulae for quark propagators in a
multi-instanton environment. As an application, and also as a necessary step
toward understanding the correlation functions, we study the propagators of
scalar and spinor quarks, using the simplest possible model, the so called
'random instanton vacuum' (RIV). Results related to heavy-light mesons, are
found to be very consistent with phenomenology.


title: Mesonic Correlation Functions in the Random Instanton Vacuum

abstract:
  A general model-independent discussion of mesonic correlation functions is
given. We derive new inequalities, including one stronger than Weingarten's
inequality. Mesonic correlation functions are calculated in the random
instanton vacuum and are compared with phenomenological expectations and
lattice results. Both diagonal and non-diagonal correlators of all strange and
light flavored currents, as well as the most important unflavored ones are
considered. Our results are used to extract the masses and the coupling
constants of the corresponding mesons. Not only the qualitative behaviour is
reproduced in all channels, but in several channels the model works with
amazing accuracy


title: The renormalization of the axial anomaly in dimensional regularization

abstract:
  The prescription for the $\gamma_5$-matrix within dimensional regularization
in multiloop calculations is elaborated. The three-loop anomalous dimension of
the singlet axial current is calculated.


title: Medley in finite temperature field theory

abstract:
  I discuss three subjects in thermal field theory: why in \sun gauge theories
the \zn symmetry is broken at high (instead of low) temperature, the possible
singularity structure of gauge variant propagators, and the problem of how to
compute the viscosity from the Kubo formula.


title: Damping rates for moving particles in hot QCD

abstract:
  Using a program of perturbative resummation I compute the damping rates for
fields at nonzero spatial momentum to leading order in weak coupling in hot
$QCD$. Sum rules for spectral densities are used to simplify the calculations.
For massless fields the damping rate has an apparent logarithmic divergence in
the infrared limit, which is cut off by the screening of static magnetic fields
(``magnetic mass''). This demonstrates how at high temperature even
perturbative quantities are sensitive to nonperturbative phenomenon.


title:
On Fermion Zero-Modes in Instanton $V-A$ Models With Spontaneous
  Symmetry Breaking

abstract:
  The left and right handed fermion zero-modes are examined. Their behaviour
under the variation of the size of the instanton, $\ri$, and the size of the
Higgs core, $\rh$, for a range of Yukawa couplings corresponding to the fermion
masses in the electroweak theory are studied. It is shown that the
characteristic radii of the zero-modes, in particlar those the left handed
fermions, are locked to the instanton size, and are not affected by the
variation of $\rh$, except for fermion masses much larger than those in the
standard electroweak theory.


title:
Effective Lagrangian for $b \rightarrow s$ Processes with
  QCD-Corrections

abstract:
  We present a complete calculation of the effective lagrangian for $b
\rightarrow s$ processes with $QCD$ corrections, in the leading logarithm
approximation, for the cases $m_t=m_w$ and $m_t \gg m_w$. The effective
lagrangian is then applied to estimate the $b \rightarrow s \gamma$ decay rate.
We find that it is enhanced by a factor of 6 for the case $m_t=m_w$, and a
factor of about 2 for $m_t \gg m_w$. Our results differ from those found in the
literature, but are not very different numerically for $m_t=m_w$.


title:
Strong and Radiative Meson Decays in a Generalized Nambu--Jona-Lasinio
  Model

abstract:
  We investigate strong and radiative meson decays in a generalized
Nambu--Jona-Lasinio model. The one loop order calculation provides a
satisfactory agreement with the data for the mesonic spectrum and for radiative
decays. Higher order effects for strong decays of $\rho$ and $K^*$ are
estimated to be large. We also discuss the role of the flavour mixing
determinantal interaction.


title:
Massive Spin-1 Field Chiral Lagrangian from an Extended
  Nambu-Jona-Lasinio Model of QCD

abstract:
  We present a calculation of the coupling constants in the massive spin-1
field chiral Lagrangian to chiral ${\cal O}(p^3)$ in the context of an extended
Nambu--Jona-Lasinio cut-off model. Phenomenological applications of this
Lagrangian to anomalous and non-anomalous low-energy hadronic transitions
involving spin-1 particles are also discussed.


title: Recent Developments in Chiral Perturbation Theory

abstract:
  I review recent developments in chiral perturbation theory (CHPT) which is
the effective field theory of the standard model below the chiral symmetry
breaking scale. The effective chiral Lagrangian formulated in terms of the
pseudoscalar Goldstone bosons ($\pi, \, K, \, \eta$) is briefly discussed. It
is shown how one can gain insight into the ratios of the light quark masses and
to what extent these statements are model--independent. A few selected topics
concerning the dynamics and interactions of the Goldstone bosons are
considered. These are $\pi \pi$ and $\pi K$ scattering, some non--leptonic kaon
decays and the problem of strong pionic final state interactions. CHPT also
allows to make precise statements about the temperature dependence of QCD Green
functions and the finite size effects related to the propagation of the
(almost) massless pseudoscalar mesons. A central topic is the inclusion of
matter fields, baryon CHPT. The relativistic and the heavy fermion formulation
of coupling the baryons to the Goldstone fields are discussed. As applications,
photo--nucleon processes, the $\pi N$ $\Sigma$--term and non--leptonic hyperon
decays are presented. Implications of the spontaneously broken chiral symmetry
on the nuclear forces and meson exchange currents are also described. Finally,
the use of effective field theory methods in the strongly coupled Higgs sector
and in the calculation of oblique electroweak corrections is touched upon.


title: Large Rapidity Gaps in PP Collisions

abstract:
  The survival probability of large rapidity gaps in pp collisions is
calculated for several different eikonal models of the Gaussian form. Results
obtained for models based on partonic interactions are quite similar. The
Regge-pole model predicts a higher value of $ < \vert S \vert^{2} > $ .


title: Angular Intermittency in QCD Jets

abstract:
  Using two methods, via fluctuations and correlations, an analytical formula
is derived for the factorial multiplicity moments in a QCD jet at the Double
Leading Logarithm accuracy. The resulting self-similar dependence on the
solid-angle cell size is characteristic of an intermittency behaviour in
angular variables. The intermittency indices depend on the diffusion angle
through the running of $ \alpha_ s. $ Physical features of jet fluctuations
such as collimation at large angles and saturation at small angles are well
described in the perturbative framework. A parameter-free prediction of angular
intermittency is proposed for $ {\cal Z}^0 $ decays into hadrons, assuming
hadron-parton duality.


title: Properties of Soft Radiation Near $\tt$ and $W^+W^-$ Threshold

abstract:
  We discuss the characteristic interference features of soft radiation in the
threshold production of heavy unstable particles: soft gluon radiation in $\ee
\to \tt$ and soft photon radiation in $\ee \to \ww$. We show that the heavy
particle decay width controls the interference between the emission off the
final state particles. As a result, the radiation pattern may provide a way of
measuring the decay width of the heavy particles.


title: Search for Anomalous $\gamma\gamma$ Production at TRISTAN

abstract:
  We report on measurements of the total cross section for e+e- --> 2-Gamma for
center-of-mass energies between 57.4 and 59.5 GeV, using the AMY detector at
the TRISTAN collider. We set new limits on the production of a possible new
s-channel resonance decaying into photon pairs.


title: Boson Pair Productions In $e^+$ $e^-$ Annihilation

abstract:
  We examine the processes $e^+ e^-\longrightarrow W^+ W^-$ and $Z^0 Z^0$ in
the context of the $SP(6)_L\otimes U(1)_Y$ model. We find that there are
significant deviations in the total cross sections $\sigma (s)$ from the
standard model results due to the presence of additional gauge bosons
$Z^\prime$ and $W^\prime$ in the model. These deviations could be detected at
LEP.


title: Constraints on New Physics From Tevatron Dijet Data

abstract:
  New results from the CDF Collaboration on the invariant mass distribution of
dijet events observed at the Tevatron are used to constrain the masses and
couplings of new gauge bosons ($W'$ and $Z'$) as well as fundamental diquarks
which can occur in some extended electroweak models. In the case of new gauge
bosons, these new bounds are then compared to existing limits which arise from
searches for the leptonic decay modes of these particles at the Tevatron.


title: Gamma Ray Bursts from Ordinary Cosmic Strings

abstract:
  We give an upper estimate for the number of gamma ray bursts from ordinary
(non-superconducting) cosmic strings expected to be observed at terrestrial
detectors. Assuming that cusp annihilation is the mechanism responsible for the
bursts we consider strings arising at a GUT phase transition and compare our
estimate with the recent BATSE results. Further we give a lower limit for the
effective area of future detectors designed to detect the cosmic string induced
flux of gamma ray bursts.


title: Could Large CP Violation Be Detected at Colliders?

abstract:
  We argue that CP--violation effects below a few tenths of a percent are
probably undetectable at hadron and electron colliders. Thus only operators
whose contributions interfere with tree--level Standard Model amplitudes are
detectable. We list these operators for Standard Model external particles and
some two and three body final state reactions that could show detectable
effects. These could test electroweak baryogenesis scenarios.


title: Resolved Photon Processes

abstract:
  We review high--energy scattering processes that are sensitive to the
hadronic structure of the photon, describing theoretical predictions as well as
recent experimental results. These processes include deep--inelastic
electron--photon scattering at \eplem\ colliders; and the production of jets,
heavy quarks and isolated photons in the collision of real photons at \eplem\
colliders, as well as in photon--proton collisions at $ep$ colliders. We also
comment on ``minijet'' based calculations of total $\gamma p$ and
  \gamgam\ cross--sections, and discuss the possibility that future linear
  \eplem\ colliders might produce very large photon fluxes due to the
  ``beamstrahlung'' phenomenon; in the most extreme cases, we predict more than
one hadronic \gamgam\ event to occur at every bunch crossing.


title: Longitudinal Structure Function at Intermediate x and the Gluon Density

abstract:
  Calculations are presented of the longitudinal structure function $F_L(x,
Q^2)$. We use next-to-leading order expressions in QCD
$({\cal{O}}(\alpha_s^2))$ plus parton densities determined previously from
global fits to data on deep inelastic lepton scattering, prompt photon
production, and bottom quark production. Anticipated data from the DESY ep
collider HERA should provide discriminating information on the gluon density,
particularly for values of $x < 0.05$.


title: One-loop fluctuation-dissipation formula for bubble-wall velocity

abstract:
  The limiting bubble wall velocity during a first-order electroweak phase
transition is of interest in scenarios for electroweak baryogenesis. Khlebnikov
has recently proposed an interesting method for computing this velocity based
on the fluctuation-dissipation theorem. I demonstrate that at one-loop order
this method is identical to simple, earlier techniques for computing the wall
velocity based on computing the friction from particles reflecting off or
transmitting through the wall in the ideal gas limit.


title: Supersymmetric Dark Matter - a Review

abstract:
  I address the question of whether supersymmetry provides a viable candidate
for the dark matter in the Universe. I review the properties of the lightest
neutralino as a candidate for solving the dark matter problem. I discuss the
neutralino's phenomenological and cosmological properties, and constraints from
present and future experiments. In the minimal supersymmetric model, the
neutralino mass has been experimentally excluded below some $20$ GeV, and is
not expected to be significantly larger than about $150$ GeV. I identify a
gaugino-like neutralino as the most natural dark matter candidate for a
plausible range of parameters. The requirement that the lightest neutralino be
the dominant matter component in the flat Universe provides non-trivial
restrictions on other parameters of the model, in particular on the masses of
the sfermions. Next, I study the consequences of adopting further grand
unification assumptions. In both scenarios I find sfermion masses most likely
beyond the reach of LEP 200 and the Tevatron but well within the discovery
potential of the SSC and the LHC. I also comment on the effects of relaxing
grand unification assumptions. Finally, I briefly outline prospects for the
neutralino dark matter searches.


title: Coupling Constant Unification and LEP Data

abstract:
  The recent LEP data for gauge coupling constants constrain many grand unified
models. In this paper, we study several possibilities for unification of gauge
coupling constants. Without an intermediate mass scale, the minimal
supersymmetric standard model is the only possibility. For one intermediate
mass scale, it is possible to have many routes toward grand unification:
$SO(10)\rightarrow SU(3)_c\times SU(2)_L\times SU(2)_R\times U(1) , SU(7),
SU(8)$, etc. We present also simple relations for the possibility of
unification.


title: Neutrino-Lasing in The Early Universe

abstract:
  Recently, Madsen has argued that relativistic decays of massive neutrinos
into lighter fermions and bosons may lead, via thermalization, to the formation
of a Bose condensate. If correct, this could generate mixed hot and cold dark
matter, with important consequences for structure formation.
  From a detailed study of such decays, we arrive at substantially different
conclusions; for a wide range of masses and decay times, we find that
stimulated emission of bosons dominates the decay. This phenomenon can best be
described as a neutrino laser, pumped by the QCD phase transition. We discuss
the implications for structure formation and the dark-matter problem.


title: Multi-Higgs Doublet Model: Can It Account for l^+l^-\gamma\gamma Events?

abstract:
  Motivated by recent experiments at LEP ($Z \to l^+l^-\gamma\gamma$, with
$M_{\gamma\gamma} \simeq 59 GeV$), we examine the possibility that such events
are explained by a Bjorken process with a resonant Higgs ($M_{h^o} \simeq 59
GeV$) decaying to $\gamma\gamma$. Our model is an N-doublet-Higgs model without
CP-violation. Under the simplifying assumption that $(N-k)$ doublets ($k \geq
1$) decouple from the fermion sector, we could explain the observed events if:
i) $(N-1) \geq 2$ and ii) the masses of the corresponding $(N-1)$ neutral
scalars are either completely or almost degenerate, i.e. the decay $Z \to
l^+l^- \gamma\gamma$ proceeds now via several overlapping resonances.


title: $J/\psi$ at small-$x$

abstract:
  It has been suggested that the suppression of $J/\psi$ production in heavy
nuclei is a signature of the formation of quark-gluon plasma. We here show that
this phenomenon can be understood in terms of conventional physics, {\it i.e.}
{\it i)} perturbative QCD, {\it ii)} the parton recombination implementation of
shadowing in the initial state, and {\it iii)} final state interactions with
the hadronic debris of the nuclear target. Unlike previous calculations we
include both the direct $J/\psi$ production and its production via radiative
$\chi$ decays ($\chi_J \to J/\psi + \gamma$). We are able to reproduce the
experimental data including their small-$x$ behavior. We emphasize the
importance of studying the $x_2$-dependence of the ratio $\sigma(b A)/\sigma(b
N)$, where $b$ designates the beam and $x_2$ is the momentum fraction of the
parton from the nuclear target.


title:
Strong renormalization scheme dependence in $\tau$-lepton decays: fact
  or fiction?

abstract:
  The question of the renormalization scheme dependence of the $\tau$
semileptonic decay rate is revisited in response to a recent criticism.
Particular attention is payed to a distinction between a consistent
quantitative description of this dependence and the actual selection of a
subset of ``acceptable'' renormalization schemes. It is argued that a
reasonable universal measure of the renormalization scheme dependence can be
formulated, which gives encouraging results when applied to various physical
quantities, including the semileptonic $\tau$ decay rate.


title: Excited Heavy Mesons and Kaon Loops in Chiral Perturbation Theory

abstract:
  We consider the effects of excited states on the $SU(3)$ breaking chiral loop
corrections to heavy meson properties. In particular, we compare the size of
kaon loops in which an excited heavy meson appears to the size of previously
calculated loops with heavy mesons in the ground state. We find that the new
effects may indeed be of the same magnitude as the old ones, but that there is
a strong dependence on the unknown masses and coupling constants of the new
states. As a result, we argue that the ground state loops alone may not be a
trustworthy guide to $SU(3)$ corrections, and that the appropriate cutoff for a
heavy-light chiral lagrangian which omits excited heavy mesons may be
considerably smaller than the na\"\i ve expectation of $\Lambda_\chi\approx
1\gev$.


title: Do Quarks Really Form Diquark Clusters in the Nucleon?

abstract:
  A gauge invariant method for the investigation of scalar diquark clustering
in the nucleon ground state is presented. The method focuses on a comparison of
quark distributions in the nucleon with those in the $\Delta$ baryon resonance.
Recent lattice QCD calculations of these quark distribution radii are analyzed
in a search for evidence of scalar diquark clustering. The analysis indicates
the lattice results describe the negative squared charge radius of the neutron
with little resort to hyperfine clustering between $u$-$d$-quark pairs. This
result contrasts both quark-diquark and nonrelativistic quark models where
hyperfine attraction between $u$ and $d$ quarks in the nucleon is argued to
play a significant role. Comparison of light quark distributions in $\Lambda^0$
and $\Sigma^{*0}$ indicate only a small reduction of the scalar diquark
distribution radius relative to the vector diquark distribution. Current
lattice QCD determinations of baryon charge distributions do not support the
concept of substantial $u$-$d$ scalar diquark clustering as an appropriate
description of the internal structure of the nucleon.


title:
Two--loop Contributions of Flavor Changing Neutral Higgs Boson to $\mu
  \to e\gamma$

abstract:
  The two--loop mechanism of Bjorken and Weinberg is used to constrain flavor
changing neutral Higgs bosons. We calculate the complete set of two--loop
diagrams for the rare decay $\mu \rightarrow e + \gamma$ induced by such
neutral Higgs bosons, for arbitrary Higgs and top masses. The analytic result
is used to set limits on Higgs masses for some recent models with specific
ansatz about the flavor changing couplings. For example, in the Cheng--Sher
scenario of multi-Higgs doublet models, all neutral Higgs bosons possess flavor
changing ($f_i \leftrightarrow f_j)$ couplings proportional to $\sqrt{m_i
m_j}$. We find that the present limit on $\mu\to e\gamma$ implies that, in such
scheme, these neutral Higgs bosons should be heavier than $200$ GeV.


title: The Electric and Magnetic Form Factors of the Neutron

abstract:
  We derive the electric and magnetic form factors of the neutron in the
framework of a relativistic constituent quark model. Our parameter free
prediction agrees well with a recent, accurate measurement. The relativistic
features of the model and the specific form of the wave function are essential
for the result. Comparisons are made to other models based on VMD, PQCD and QCD
sum rules.


title:
Reparametrization invariance and the expansion of currents in the heavy
  quark effective theory

abstract:
  The coefficients appearing at leading and subleading order in the $1/m$
expansion of bilinear heavy quark currents are related to each other by
imposing reparametrization invariance on both the effective current operators
and the short-distance coefficient functions in the heavy quark effective
theory. When combined with present knowledge about the leading order
coefficients, the results allow to calculate all coefficients appearing at
order $1/m$ to next-to-leading order in renormalization-group improved
perturbation theory. They also provide a meaningful definition of the velocity
transfer variable $v\cdot v'$ to order $1/m$.


title: Very Small Strangelets

abstract:
  We study the stability of small strangelets by employing a simple model of
strange matter as a gas of non-interacting fermions confined in a bag. We solve
the Dirac equation and populate the energy levels of the bag one quark at a
time. Our results show that for system parameters such that strange matter is
unbound in bulk, there may still exist strangelets with $A<100$ that are stable
and/or metastable. The lifetime of these strangelets may be too small to detect
in current accelerator experiments, however.


title:
$Z$--$Z'$ mixing and oblique corrections in an ${\rm SU(3) \times U(1)}$
  model

abstract: A global fit for experiments is included in this revised version.


title: Errata for "The Higgs Hunter's Guide"

abstract:
  Errata are given for "The Higgs Hunter's Guide". These errata should be
applied to the second printing of the book, dated 1991. The second printing has
already corrected numerous errors and misprints contained in the originally
published 1990 edition.


title:
Right-handed Neutral Currents, Families and the LEP $l^+l^-\gamma\gamma$
  Events

abstract:
  We explore the possibility of having new physics which could account for the
$l^+l^-\gamma\gamma$ events with $M_{\gamma\gamma}\simeq 60\ $GeV recently
reported by LEP. We consider models which contain an extra neutral gauge boson
($Z'$) that couples only to right-handed fermions. The models naturally require
at least three quark and lepton families from anomaly cancellation. We find
simple realizations of such models that have $\ell^+\ell^-\gamma\gamma$ events
at a rate similar to that observed at LEP.


title: Vanishing of Nonabelian Berry Phases in Heavy Solitonic Baryons

abstract:
  In this article, we show -- using a reasoning applicable to both the
excitation spectrum in the chiral bag model and the hyperfine structure of
diatomic molecules -- that the generic form of a non- abelian Berry potential
appears in heavy-quark effective theory (HQET) and that the Berry potential
vanishes for the soliton- heavy meson bound state in the heavy-quark limit. The
vanishing of the Berry potential in HQET is shown to be related to the
restoration of heavy-quark symmetry in infinite heavy-quark-mass limit in close
analogy to diatomic molecules at infinite internuclear separation.


title: Hard Photon Pair Production at LEP

abstract:
  The production of photon pairs in $e^+e^-\rightarrow f \bar f \gamma\gamma$
processes is studied using exact helicity amplitudes at tree level. Total cross
sections, including initial state radiation effects, are given. They are
presented in the case of quarks as a function of $y_{\rm cut}$ in the JADE
algorithm. In the case of leptons we use cuts similar to the ones employed in a
recent L3 analysis. Masses of the final state fermions are taken into account
when appropriate. The cross section $e^+e^-\rightarrow \tau^+ \tau^-
\gamma\gamma$ is about 10\% larger when the $\tau$ mass is neglected. We
obtain, with a different method, results which are in good agreement with L3
Montecarlo simulation.


title: Charged Scalar Particles and $\tau$ Leptonic Decay

abstract:
  Charged scalar particles introduced in some extensions of the standard model
can induce $\tau$ leptonic decay at tree level. We find that with some charged
SU(2)-singlet scalar particles, like ones introduced in Zee-type models, $\tau$
leptonic decay width is always smaller than what is predicted by the standard
model, therefore they may offer a natural solution to $\tau$ decay puzzle. To
be more specific, we examine some Zee-type models in detail to see if at the
same time they are acceptable in particle physics, cosmology and astrophysics.
It is shown that $\tau$ decay data do put some constrains on these models.


title:
Derivation of $m_A \simeq M_Z$ and $\tan \beta > \sqrt 3$ in the Minimal
  Supersymmetric Standard Model

abstract:
  In the minimal supersymmetric standard model, the Higgs sector has two
unknown parameters, usually taken to be $\tan \beta \equiv v_2/v_1$ and $m_A$,
the mass of its one physical pseudoscalar particle. By minimizing the minimum
of the Higgs potential along a certain direction in parameter space, it is
shown that $m_A = M_Z$ + radiative correction, and if one further plausible
assumption is made, $\tan \beta > \sqrt 3$.


title: Toponium Tests Of Top-Quark Higgs Bags

abstract:
  Recently it has been suggested that top quarks, or very massive fourth
generation quarks, might surround themselves with a Higgs "bag" of deformation
of the Higgs expectation value from its vacuum magnitude. In this paper we
address the question of whether such nonlinear Higgs-top interaction effects
are subject to experimental test. We first note that if top quarks were
necessarily accompanied by Higgs "bags", then top quark weak decay would
involve the sudden disruption of the Higgs "bag", with copious production of
physical Higgs particles accompanying the decay. We then examine the effects
that such Higgs "bags" would produce on the spectrum of toponium, where the two
bound top (anti)quarks, and their "bags", overlap. We numerically evaluate the
effects that the nonlinear feedback in the Higgs-toponium system would have on
the energy level splittings of the toponium bound states, and find that for
allowed values of the top and Higgs mass the effect is negligible, thus
indicating that even in this favourable circumstance Higgs "bag" formation
around top quarks does not observably occur. Finally, we consider the case of a
second Higgs doublet, allowing the possibility of enhanced couplings for one of
the physical Higgs to top. Even in this nonstandard scenario the effects are
minimal, and we infer the general absence of observable effects at any level
that might suggest the utility of considering top quarks to be accompanied by
Higgs "bags".


title: On the B and J/Psi Cross Section Measurements at Ua1 and CDF

abstract:
  We analise the implications of the measurement of $B$ and $J/\psi$ inclusive
\pt\ distributions performed in $p\bar p$ collisions by the UA1 and CDF
experiments.


title: One-Loop Corrections to Five-Gluon Amplitudes

abstract:
  We present the one-loop helicity amplitudes with five external gluons. The
computation employs string-based methods, new techniques for performing tensor
integrals, and improvements in the spinor helicity method.


title: Higgs - Two Photon Decay: QCD radiative correction

abstract:
  QCD radiative correction to Higgs $\rightarrow$ two photons decay rate is
calculated. Below the threshold we found negligible correction, thus supporting
results obtained earlier by Djouadi et all [7]. Above the threshold radiative
correction appears to be large for both real and imaginary part of H $\gamma
\gamma$ vertex. This leads to radiative correction for $\Gamma $(H $\rightarrow
\gamma \gamma $) to be of order 20--100 percents at $m_{t}=150 GeV$.
  Possible applications of our results for Higgs search at Next Linear
Colliders (NLC) are briefly discussed.


title: What is the Natural Size of Supersymmetric $CP$ Violation?

abstract:
  It is well known that if phases and masses in the Minimal Supersymmetric
Standard Model (MSSM) are allowed to have general values, the resulting neutron
EDM ($d_n$) exceeds the experimental upper limit by about $10^3$. We assume
that the needed suppression is not due to a fine-tuning of phases or masses,
and ask what natural size of $CP$ violation (CPV) results. We show that (1) the
phase of one of the superpotential parameters, $\mu$, does not contribute to
any CPV in the MSSM and so is not constrained by \dn; (2) the MSSM contribution
to $d_n$ is tiny, just coming from the CKM phase; (3) the phases in the MSSM
cannot be used to generate a baryon asymmetry at the weak scale, given our
assumptions; and (4) in non-minimal SUSY models, an effective phase can enter
at one loop giving $d_n \sim 10^{-26}$\ecm, $d_e \sim 10^{-27}$\ecm, and
allowing a baryon asymmetry to be generated at the weak scale, without
fine-tunings. Our results could be evaded by a SUSY breaking mechanism which
produced phases for the SUSY breaking parameters that somehow were naturally of
order $10^{-3}$.


title:
Empirical Determination of the Very High Energy Heavy Quark Cross
  Section from Non-Accelerator Data

abstract:
  To cosmic rays incident near the horizon the Earth's atmosphere represents a
beam dump with a slant depth reaching 36000~g~cm$^{-2}$ at $90^\circ$. The
prompt decay of a heavy quark produced by very high energy cosmic ray showers
will leave an unmistakable signature in this dump. We translate the failure of
experiments to detect such a signal into an upper limit on the heavy quark
hadroproduction cross section in the energy region beyond existing
accelerators. Our results disfavor any rapid growth of the cross section or the
gluon structure function beyond very conservative estimates based on
perturbative QCD.


title: Measuring the Gamma-Gamma Coupling of the Higgs at Linear Colliders

abstract:
  Observing the production of the Higgs particle in the $\gamma$-$\gamma$ mode
of a linear $e^+e^-$ collider allows for the measurement of the $H\gamma\gamma$
coupling. We point out that for the intermediate Higgs mass range this
measurement is considerably more challenging than previously believed. The $b
\bar b$ signature receives a large background from the production of heavy
quark pairs by resolved photons. We quantify the experimental requirements
needed to make a meaningful measurement in the presence of this background.


title: Consequences of a Possible Di-Gamma Resonace at TRISTAN

abstract:
  If high mass di-gamma events observed at LEP are due to the production of a
di-gamma resonance via its leptonic coupling, its consequences can be observed
at TRISTAN. We find that a predicted $Z$ decay branching rate is too small to
account for the observed events if the resonance spin is zero, due to a strong
cancellation in the decay amplitudes. Such a cancellation is absent if the
resonance has a spin two. We study the consequences of a tensor production in
the processes $e^+e^- \to e^+e^-$, $\mu^+\mu^-$ and $\gamma\,\gamma$ at TRISTAN
energies. Complete helicity amplitudes with tensor boson exchange contributions
are given, and the signal can clearly be identified from various distributions.
TRISTAN experiments are also sensitive to the virtual tensor boson exchange
effects, which reduce to the contact interaction terms in the high mass limit.


title: Radiative Tau Decays with One Pseudoscalar Meson

abstract:
  We have calculated the decay $\tau \rightarrow \nu \pi(K) \gamma$. We present
the photon energy spectrum, the meson-photon invariant mass spectrum and the
integrated rate as a function of a photon energy cut or an invariant mass cut.
Both the internal bremsstrahlung and the structure dependent radiation have
been taken into account. To this aim we have parametrized the form factors
$F_V$ and $F_A$, which determine the structure dependent radiation. Observables
especially suited for the measurement of the structure dependent form factors
are found and implications on the width of the $a_1$ discussed.


title:
$SU(n)_c\otimes SU(m)_L\otimes U(1)_N$ generalizations of the Standard
  Model

abstract:
  We consider generalizations of the standard model (SM) which are based on the
gauge symmetry $SU(n)_c\otimes SU(m)_L\otimes U(1)_N$. Although the most
interesting possibilities occur when $n=3$, we will consider also the cases
$n=4,5$ both with $m=3,4$. Models with left-right symmetry, horizontal
symmetries and the possible embedding in a larger group (grand unification
scenarios) are briefly discussed.


title:
Current Algebra Approach to Heavy Top Effects in $Z \rightarrow b+
  \bar{b}$

abstract:
  The $O(\alpha m_t^2/m_w^2)$ and $O(\alpha \alpha_s m_t^2/m_w^2)$ corrections
to the partial decay width $\Gamma(Z \rightarrow b + \bar{b})$ are computed
using the current algebra formulation of radiative corrections. This framework
allows one to easily enforce the relevant Ward identity that greatly simplifies
the calculations. As a result, the one-loop $O(\alpha m_t^2/m_w^2)$
contribution is computed through the investigation of only two convergent
diagrams. The computation of the QCD corrections to the one-loop $O(\alpha
m_t^2/m_w^2)$ term involves fewer diagrams than in the standard approach. In
particular, the number of infrared divergent contribution is reduced. The
calculation is performed in the dimensional regularization scheme and no term
more divergent than $\frac{1}{n-4}$ is found. Our result confirms the screening
of the one-loop top mass effect recently found by Fleischer {\em et al.}.


title: Light Composite Vector Bosons

abstract:
  In gauge theories with slowly-running coupling constants, it may be possible
for four-fermion operators to be nearly marginal. Such operators can possess
asymptotically weak couplings, and can plausibly give rise to light composite
vector mesons.


title: Double Beta Decay with Vector Majorons

abstract:
  We consider the possibility that neutrinoless double beta decay may occur in
models with unbroken lepton number via the emission of a massive gauge boson
with electron lepton number $-2$. We determine the shape of the $\beta\,\beta$
sum energy spectrum as a function of the gauge coupling, independent of
model-specific details. We discuss our results in light of the persistent
experimental claims that excess events are observed near but below the spectrum
endpoint of several elements.


title: Yukawa correction to top-quark production at the Tevatron

abstract:
  We calculate the correction to $\qbq\to\tbt$ of order $\gmm$. This
correction, proportional to the square of the Higgs-boson Yukawa coupling to
the top quark, arises from loops of Higgs bosons and the scalar component of
virtual vector bosons. The Yukawa correction to the total \tbt\ production
cross section at the Fermilab Tevatron in the standard Higgs model is found to
be much less than the theoretical uncertainty in the cross section. However, in
a two-Higgs-doublet model, Yukawa couplings are generally enhanced. The Yukawa
correction can increase the total $t\bar t$ production cross section in this
model by as much as $20$-$35\%$, which is potentially observable at the
Tevatron.


title:
New Upper Limits on the Tau Neutrino Mass from Primordial Helium
  Considerations

abstract:
  In this paper we reconsider recently derived bounds on $MeV$ tau neutrinos,
taking into account previously unaccounted for effects. We find that, assuming
that the neutrino life-time is longer than $O(100~sec)$, the constraint
$N_{eff}<3.6$ rules out $\nu_{\tau}$ masses in the range
$0.5~(MeV)<m_{\nu_\tau}<35~(MeV)$ for Majorana neutrinos and
$0.74~(MeV)<m_{\nu_\tau}<35~(MeV)$ for Dirac neutrinos. Given that the present
laboratory bound is 35 MeV, our results lower the present bound to $0.5$ and
$0.74$ for Majorana and Dirac neutrinos respectively.


title: The Production of the Exotic Atoms $\pi^+\pi^-$, $K^+\pi^-$ and $K^+K^-$

abstract:
  Estimates are made of the signals to be expected in the production of the
exotic atoms Pionium ($\pi^+\pi^-$), Kaonium ($K^+K^-$) and also $K^+\pi^-$ in
pp, pd and $e^+e^-$ reactions. Such experiments are now being undertaken or
contemplated at CELSIUS, COSY, Indiana and SATURNE.


title:
Calculation of the contributions to the signals and backgrounds for
  intermediate mass Higgs detection at the LHC and SSC from the q qbar initial
  state

abstract:
  We calculate the subprocess q qbar --> t tbar H which contributes to the
signal for detection of a light `intermediate mass' Higgs boson at the LHC and
SSC in the isolated lepton and two isolated photons mode. This enhances the gg
--> t tbar H signal by about 10% at the SSC and 25% at the LHC. We also
calculate the q qbar --> t tbar gamma gamma irreducible background subprocess
to this detection mode which enhances the gg --> t tbar gamma gamma irreducible
background. This background is found to be quite substantial due to the effect
of radiation from the initial state quarks as well as the final state t tbar
pair; at the SSC the q qbar initial state background enhances the gg initial
state background by between 20% for m_t=100 GeV and 35% for m_t=180 GeV, and at
the LHC by between 50% for m_t=100 GeV and 120% for m_t=180 GeV. However with a
3% mass resolution on the gamma gamma mass the extra q qbar background events
are typically smaller than the extra q qbar signal events, and the signal
remains observable.


title: The Top Width - Theoretical update

abstract:
  A critical assessment of the available calculations of the top quark width is
presented. QCD corrections, the finite mass of the $b$ quark and the effect of
the $W$ width are included as well as the electroweak corrections. The relative
importance of these corrections is demonstrated for the realistic range of top
masses. For the QCD corrected decay rate we use the formulae from \cite{JK1}
and include the electroweak correction taken from \cite{DS}. Our results differ
from those available in the literature because all the later calculations
ignored the effect of W width discussed earlier in \cite{JK1}~. This leads to
an effect comparable in size to the electroweak correction.


title: Unified Description of Hadrons and Heavy Hadron Decays

abstract:
  We construct an effective Lagrangian which describes interactions of heavy
and light hadrons utilizing the chiral flavor symmetry for light quarks and
heavy quark symmetry. For both light and heavy sector we include pseudo
scalars, vectors and baryons in the Lagrangian. Heavy hadron decays are
discussed as application of our formalism. The $D_s$ decay constant and the
coupling constant among heavy meson, heavy vector meson and light meson are
fitted from the experimental data of $D^0 \rightarrow K^- e^+\nu_e$ decay. We
also point out the possibility of model independent determination of $|V_{ub}|$
from $\Lambda_b \rightarrow p l \bar \nu$ decay.


title: Constraints on Anomalous $WW\gamma$ Couplings From $e\gamma$\ Collisions

abstract:
  We study the potential for using $e\gamma$\ collisions produced by
backscattered laser photons to investigate WW$\gamma$\ couplings. We present
results for Next Linear Collider energies of 500 GeV and 1 TeV. We find that
where statistics allow, off W mass shell results can be quite important,
complementing on W mass shell results from this and other studies. It is shown
that $e\gamma$\ colliders would prove quite valuable in the investigations of
W-boson physics.


title: On the current correlators in QCD at finite temperature

abstract:
  Current correlators in QCD at a finite temperature $T$ are considered from
the viewpoint of operator product expansion. It is stressed that at low $T$ the
heat bath must be represented by hadronic, and not quark-gluon states. A
possibility to express the results in terms of $T$-dependent resonance masses
is discussed. It is demonstrated that in order $T^2$ the masses do not move and
the only phenomenon which occurs is a parity and isospin mixing.


title:
Estimates of $m_d - m_u$ and $\langle\bar{d}d\rangle -
  \langle\bar{u}u\rangle$ from QCD sum rules for $D$ and $D^{\ast}$ isospin
  mass differences

abstract:
  The recent experimental data on $D^{+}-D^{0}$ and $D^{\ast\, +}-D^{\ast\,0}$
mass differences are used as inputs in the QCD sum rules to obtain new
estimates on the mass difference of light quarks and on the difference of their
condensates: $m_d -m_u =3\pm 1\, MeV$, $\langle\bar{d}d\rangle
-\langle\bar{u}u\rangle = -(2.5\pm 1)\cdot 10^{-3}\langle\bar{u}u\rangle$ (at a
standard normalization point, $\mu = 0.5\, GeV$).


title: Temperature Dependence of Electric and Magnetic Gluon Condensates

abstract:
  The contribution of Lorentz non-scalar operators to finite temperature
correlation functions is discussed. Using the local duality approach for the
one-pion matrix element of a product of two vector currents, the temperature
dependence of the average gluonic stress tensor is estimated in the chiral
limit to be $\langle{\bf E}^2 +{\bf B}^2\rangle_{T}=\frac{\pi^2}{10}bT^4$. At a
normalization point $\mu=0.5$ GeV we obtain $b\approx 1.1$. Together with the
known temperature dependence of the Lorentz scalar gluon condensate we are able
to infer $\langle{\bf E}^2\rangle_T$ and $\langle{\bf B}^2\rangle_T$ separately
in the low-temperature hadronic phase.


title: Masses, Mixings, Yukawa Couplings and their Symmetries

abstract:
  We present a method to find the number of real and imaginary observable
parameters coming from the Yukawa sector in an arbitrary gauge theory. The
method leads naturally to a classification of Yukawa couplings according to
their symmetries and suggests a new parametrization of masses and mixings that
is useful to study the behaviour of Yukawa couplings under the renormalization
group. We apply it to some examples based on the Standard Model with Yukawa
couplings obeying various chiral symmetries. We also show how our method of
parameter counting can be used in some models with an enlarged leptonic sector.


title: Supersymmetric Signals in $\gamma\gamma$ Collisions

abstract:
  We study the occurrence of final states with only an electron-positron pair
and missing transverse momentum as a signal of \susy\ in photon-photon
collisions. Suitable high energy photon beams may be provided at linear
colliders by back-scattering laser beams on electron beams. The final states
considered represent a typical signature for the production and decay of
selctron and chargino pairs within the \mssm. We show that, away from the
kinematical threshold, selctrons produce this signal far more abundantly than
charginos. The standard model background is dominated by W-pair production. We
propose a series of kinematical cuts which reduce this background to an
acceptable level. With a 1 TeV collider operated in the $\gamma\gamma$-mode, we
find that interesting and complementary tests of \susic\ models can be
performed for selctron masses up to 350 GeV.


title: Testing Supersymmetry by Means of Time Reversal Invariance

abstract:
  The minimal supersymmetric extension of the standard model allows for some of
the coupling strengths to be complex parameters. The presence of such imaginary
phases can lead to violations of time reversal invariance, which can be tested
if correlations in products of an odd number of polarizations and momenta are
measured and found to be different from zero. As an example, we consider the
triple product $\mbox{\bf J} \cdot \left(\mbox{\bf p}_1 \times \mbox{\bf p}_
{2} \right)$ in the $\beta$-decay of the neutron, of the $\Sigma^-$, and in the
decay $K^{+}_{3\mu}$. For these low-energy decays, we find that the present
experimental precision is not enough to provide useful bounds on combinations
of such phases and the masses of the supersymmetric particles. At higher
energies, the same time reversal violating correlation in the semileptonic
decay of the $t$ quark is of the order of $\alpha_s/\pi$, made bigger by the
large mass of the decaying quark.


title: The $\pi^0\to e^+e^-$ and $\eta\to \mu^+ \mu^-$ Decays Revisited

abstract:
  The rare $\pi^0 \to e^+e^-$ and $\eta \to \mu^+\mu^-$ decays are calculated
in different schemes, which are seen to be essentially equivalent to and
produce the same results as conventional Vector-Meson Dominance. We obtain the
theoretical predictions $B(\pi^0 \to e^+e^-) = (6.41 \pm 0.19)\times 10^{-8}$
and $B(\eta \to \mu^+\mu^-) = (1.14 +0.06 -0.03) \times 10^{-5}$ in agreement
with recent experimental data.


title: Next-to-Leading Order QCD Formulation of Deep Inelastic Scattering

abstract:
  We have performed a QCD next-to-leading order (NLO) calculation for Deep
Inelastic Scattering (DIS) retaining the full parton and hadron mass
dependencies. We find that the gluon initiated contributions to DIS processes,
such as charm production, are {\it comparable} in magnitude ({\it i.e.}, $30\%$
to $100\%$) to the ``leading-order'' (LO) sea-quark processes. The
``slow-rescaling" prescription and the full NLO formalism are compared in a
quantitative manner. The use of DIS distributions and the inclusion of the
charm mass via slow-rescaling are not sufficient to mimic the correct NLO
physics. These results imply that previous analyses of charm production data to
extract the strange and charm content of the nucleon, as well as the precise
determination of Standard Model parameters based on these analyses (such as the
Weinberg angle), need to be reassessed.


title: QCD Tests in Proton-Antiproton Collisions

abstract:
  We review the status of QCD tests in high energy p-pbar collisions. Contents:
i) Introduction ii) QCD in Hadronic Collisions iii) Jet Production iv) Heavy
Flavour Production v) W and Z Production vi) Direct Photons.


title: Z^0 Decay into Charmonium via Charm Quark Fragmentation

abstract:
  In decays of the $Z^0$, the dominant mechanism for the direct production of
charmonium states is the decay of the $Z^0$ into a charm quark or antiquark
followed by its fragmentation into the charmonium state. We calculate the
fragmentation functions describing the splitting of charm quarks into S-wave
charmonium states to leading order in the QCD coupling constant. Leading
logarithms of $M_Z/m_c$ are summed up using Altarelli-Parisi evolution
equations. Our analytic result agrees with the complete leading order
calculation of the rate for $Z^0 \rightarrow \psi c {\bar c}$. We also use our
fragmentation functions to calculate the production rate of heavy quarkonium
states in $W^\pm$, top quark, and Higgs decays.


title:
Heterotic Pomeron: A Unified Treatment of High Energy Hadronic
  Collisions in QCD

abstract:
  A unified treatment of high energy collisions in QCD is presented. Using a
probabilistic approach, we incorporate both perturbative (hard) and
non-perturbative (soft) components in a consistent fashion, leading to a
``Heterotic Pomeron". As a Regge trajectory, it is nonlinear, approaching 1 in
the limit $t\rightarrow -\infty$.


title:
$K_L \ra \mu^\pm e^\mp \nu \overline{\nu}$ as background to $K_L \ra
  \mu^\pm e^\mp$

abstract:
  We consider the process $K_L \ra \mu^\pm e^\mp \nu \overline{\nu}$ at next to
leading order in chiral perturbation theory. This process occurs in the
standard model at second order in the weak interaction and constitutes a
potential background in searches for new physics through the modes $K_L \ra
\mu^\pm e^\mp$. We find that the same cut, $M_{\mu e}>489$~MeV, used to remove
the sequential decays $K_{l3}\ra \pi_{l2}$ pushes the $B(K_L \ra \mu^\pm e^\mp
\nu \overline{\nu})$ to the $10^{-23}$ level, effectively removing it as a
background.


title:
Dimensionality of spacetime as a gauge-invariance parameter in
  Yang-Mills calculations

abstract: This is the revised version of an earlier paper with the same title.


title: Top Near Threshold: All QCD Radiative Corrections are Trivial

abstract:
  We have calculated part of O(${\alpha}_{S}$) QCD radiative correction to the
total cross-section of top's threshold production in $ e^{+}e^{-} \to t\bar t
\to W^{-} b W^{+} \bar b$ reaction. We found out a curious fact: there is no
O(${\alpha}_{S}$) correction to the total cross-section, originated from $b
\bar b , t \bar b ,\bar t b $ gluon exchange and corresponding gluon emission.
Thus, all O(${\alpha}_{S}$) corrections which are non-zero, can be classified
as: 1) corrections to $t \bar t$ nonrelativistic potential 2) corrections to
the top's width 3) hard gluon correction to $\gamma t \bar t$-vertex. These
corrections are well-known and were described in the previous papers. We can
conclude that similar situation takes place for all unstable particles
threshold production. This result can be expressed in the form of a general
statment: There is no O(${\alpha}_{QED}$ or ${\alpha}_{QCD}$) corrections for
the total cross-section , originated from the "jet-jet" interection.


title: Non-oblique Correction in Extenden Technicolor Theory

abstract:
  We study radiative corrections on $Zb{\bar b}$ vertex generated by the ETC
gauge bosons, ``diagonal'' as well as sideways. Although the oblique
corrections due to the ETC bosons are small in comparison with the oblique
correction due to the technicolor dynamics, the non-oblique corrections result
in substantial shift of contour plot in the $S$-$T$ plane. We show that such a
shift due to the non-oblique corrections is actually important for discussing
$S$ and $T$ values in the technicolor models.


title: Fermions in the background of the sphaleron barrier

abstract:
  We demonstrate the level crossing phenomenon for fermions in the background
field of the sphaleron barrier, by numerically determining the fermion
eigenvalues along the minimal energy path from one vacuum to another. We assume
that the fermions of a doublet are degenerate in mass, allowing for spherically
symmetric ans\"atze for all of the fields, when the mixing angle dependence is
neglected.


title: Sphalerons at finite temperature

abstract:
  We construct the sphaleron for several temperature dependent effective
potentials. We determine the sphaleron energy as a function of temperature and
demonstrate that the sphaleron energy at a given temperature $T$ is well
approximated by the sphaleron energy at temperature zero scaled by the ratio of
the vacuum expectation values of the Higgs field at temperatures $T$ and zero.
We address the cosmological upper bound on the Higgs mass.


title: T Violation Induced by Supersymmetry in t\bar{t} and W^+W^- Physics

abstract:
  T-odd correlations of polarizations and momenta provide a promising testing
ground for new physics beyond the standard model. We estimate the contribution
of the minimal supersymmetric extension of the standard model to two such
observables: in the production of $t\bar{t}$, we look for a term proportional
to \mbox{${\bf J}_t \cdot ({\bf p}_q \times {\bf p}_{t})$}-where {\bf J}$_t$ is
the polarization of the $t$ quark and {\bf p} $_{q,t}$ are the momenta of the
initial and final particles-and find that it is of the order of $10^{-1} \times
(\alpha_s/\pi)$. In the production of $W^+W^-$, we look for a term proportional
to \mbox{${\bf E}_W \cdot ({\bf p}_q \times {\bf p}_{W})({\bf p}_q \cdot {\bf
E}_W)$}-where {\bf E}$_W$ is the transverse polarization of W- to find that it
can be as large as $10^{-1} \times (\alpha_w/\pi)$.


title: Reconciling Dark Matter, Solar and Atmospheric Neutrinos

abstract:
  We present models that can reconcile the solar and atmospheric neutrino data
with the existence of a hot dark matter component in the universe. This dark
matter is a quasi-Dirac neutrino whose mass $m_{DM}$ arises at the one-loop
level. The solar neutrino deficit is explained via nonadiabatic conversions of
electron neutrino to a sterile neutrino and the atmospheric neutrino data via
maximal muon neutrino to tau neutrino oscillations generated by higher order
loop diagrams. For $m_{DM} \sim 30$ eV the radiative neutrino decay can lead to
photons that can ionize interstellar hydrogen. In one of the models one can
have observable $\nu_e$ to $\nu_\tau$ oscillation rates, with no appreciable
muon neutrino oscillations at accelerator experiments. In addition, there can
be observable rates for tau number violating processes such as $\tau \to 3e$
and $\tau \to e + \gamma$. In the other model one can have sizeable $\nu_e$ to
$\nu_\mu$ oscillation rates, as well as sizeable rates for muon number
violating processes such as $\mu \to e + \gamma$, $\mu \to e + majoron$ and
$\mu \to 3e$.


title: Cosmological Constraints and SU(5) Supergravity Grand Unification

abstract:
  The predictions of SU(5) supergravity models with radiative breaking
constrained by experimental proton decay bounds are discussed. It is shown that
cosmological constraints further restrict the parameter space but can be
satisfied for a wide range of parameters. It is also shown that no serious fine
tuning problems (either at $M_{SUSY}$ or $M_{GUT}$) exist.


title:
Predictions in SU(5) Supergravity Grand Unification with Proton
  Stability and Relic Density Constraints

abstract:
  It is shown that in the physically interesting domain of the parameter space
of SU(5) supergravity GUT, the Higgs and the Z poles dominate the LSP
annihilation. Here the naive analyses on thermal averaging breaks down and
formulae are derived which give a rigorous treatment over the poles. These
results are then used to show that there exist significant domains in the
parameter space where the constraints of proton stability and cosmology are
simultaneously satisfied. New upper limits on light particle masses are
obtained.


title: Single $W$ Boson Production in High Energy $e\gamma$ Collisions

abstract:
  We studied single $W$ boson production in high energy $e\gamma$ collisions
and the sensitivity of various observables to the $WW\gamma$ gauge boson
coupling. We evaluated the helicity amplitudes including the $W$ decay to final
state fermions and all Feynman diagrams which give the same final state. At
high energy, the non-resonant diagrams give significant contributions to the
cross sections and should not be neglected. We first considered a
$\sqrt{s}=120$~GeV $e^+e^-$ collider converted to an $e\gamma$ collider by
backscattering a low energy laser off of one of the original electron beams.
Such a collider could measure $\kappa_\gamma$ to $\simeq\pm 0.09$ at 95\% C.L.
which is the same level of precision as could be achieved at LEP200 using $W$
pair production. We next considered single $W$ production at a 200 GeV $e^+e^-$
collider in the Weizacker-Williams approximation which can measure the
$WW\gamma$ vertex independently of the $WWZ$ vertex. This process can measure
$\kappa_\gamma$ to $\pm 0.15$ at 95\% C.L. which is comparable to the $W$ pair
production process. Finally, we examined $W$ production at 500 GeV and 1 TeV
$e^+e^-$ colliders, comparing results for photon spectra obtained from a
backscattered laser and from beamstrahlung radiation. Here we found that the
couplings could best be measured using the backscattered laser photons with
$|\delta\kappa_\gamma|\leq 0.07$ and


title: Tensor Structure Function b$_1$(x) For Spin-One Hadrons

abstract:
  High-energy spin physics became a popular topic recently after the EMC
finding for the proton's spin content. There exist unmeasured spin-dependent
structure functions ($b_1$, $b_2$, $b_3$, and $b_4$) for spin-one hadrons such
as the deuteron. The tensor structure function $b_1(x)$ could be measured by
the proposed 15 GeV European Electron Facility. The measurement provides
important clues to physics of non-nucleonic components in spin-one nuclei and
to tensor structures on the quark-parton level.


title: General Solutions for Tunneling of Scalar Fields with Quartic Potentials

abstract:
  For the theory of a single scalar field $\varphi$ with a quartic potential
$V(\varphi)$, we find semi-analytic expressions for the Euclidean action in
both four and three dimensions. The action in four dimensions determines the
quantum tunneling rate at zero temperature from a false vacuum state to the
true vacuum state; similarly, the action in three dimensions determines the
thermal tunneling rate for a finite temperature theory. We show that for all
quartic potentials, the action can be obtained from a one parameter family of
instanton solutions corresponding to a one parameter family of differential
equations. We find the solutions numerically and use polynomial fitting
formulae to obtain expressions for the Euclidean action. These results allow
one to calculate tunneling rates for the entire possible range of quartic
potentials, from the thin-wall (nearly degenerate) limit to the opposite limit
of vanishing barrier height. We also present a similar calculation for
potentials containing $\varphi^4 \ln \varphi^2$ terms, which arise in the
one-loop approximation to the effective potential in electroweak theory.


title: Vector Resonances from a Strong Electroweak Sector at Linear Colliders

abstract:
  We explore the usefulness of very energetic linear $e^+e^-$ colliders in the
$TeV$ range in studying an alternative scheme of electroweak symmetry breaking
based on a strong interacting sector. The calculations are performed within the
BESS model which contains new vector resonances. If the mass $M_V$ of the new
boson multiplet lies not far from the maximum machine energy, or if it is
lower, such a resonant contribution would be quite manifest. A result of our
analysis is that also virtual effects are important. It appears that
annihilation into a fermion pair in such machines, at the considered
luminosities, would improve only marginally on existing limits if polarized
beams are available and left-right asymmetries are measured. On the other hand,
the process of $W$-pair production by $e^+e^-$ annihilation would allow for
sensitive tests of the hypothesized strong sector, especially if the $W$
polarizations are reconstructed from their decay distributions, and the more so
the higher the energy of the machine. An $e^+e^-$ collider with c.m. energy
$\sqrt{s}=500~GeV$ could improve the limits on the model for the range
$500<M_V(GeV)<1000$ when $W$ polarization is not reconstructed. If $W$
polarizations are reconstructed, then the bounds improve for the entire
expected range of $M_V$. These bounds become more stringent for larger energy
of the collider. We have also studied the detectability of the new resonances
through the fusion subprocesses, but this channel does not seem to be
interesting even for a collider with a c.m. energy $\sqrt{s}=2~TeV$.


title:
On the Unification of Couplings in the Minimal Supersymmetric Standard
  Model

abstract:
  The unification of gauge and Yukawa couplings within the minimal
supersymmetric standard model is studied at the two loop level. We derive an
expression for the effective scale, $T_{SUSY}$, which characterizes the
supersymmetric particle threshold corrections to the gauge couplings, and
demonstrate that $T_{SUSY}$ is only slightly dependent on the squark and
slepton masses, and strongly dependent on the Higgsino masses as well as on the
mass ratio of the gauginos of the strong and weak interactions. Moreover, the
value of the top quark Yukawa coupling necessary to achieve the unification of
bottom and tau Yukawa couplings is also governed by $T_{SUSY}$, and it yields
predictions for the top quark mass which are close to the quasi infrared fixed
point results associated with the triviality bounds on this quantity. From the
requirement of perturbative consistency of the top quark Yukawa sector of the
theory, we obtain constraints on the allowed splitting of the supersymmetric
spectrum, which, for certain values of the running bottom quark mass, are
stronger than those ones coming from the experimental constraints on the strong
gauge coupling.


title: CP Test in the W Pair Production via Photon Fusion at NLC

abstract:
  We study the possibility to test CP invariance in the $W^+W^-$ production via
photon fusion at NLC. The predictions of the CP violation effects are made
within two Higgs doublet extensions of the minimal standard model, where CP
violation is introduced by a neutral Higgs exchange in s channel in our case.
The width effect in the Higgs propagator on the CP violation effects is studied
in detail. The CP violation effects can be measured in some parameter region of
the extensions.


title: CP Violation in $t \bar{t}$ Production at $e^+ e^-$ Colliders

abstract:
  The general production {\it and} decay mechanism of $\ttbar$ in future
high-energy $\epem$ colliders has been investigated in a model-independent way,
focusing on an observation of possible CP violation. Angular asymmetries
sensitive to CP violation either in the production {\it or} in the subsequent
decays have been found. General considerations are illustrated through 1-loop
effects induced by gluino exchange in the supersymmetric version of the
Standard Model.


title: Gluon Fragmentation into Heavy Quarkonium

abstract:
  The dominant production mechanism for heavy quark-antiquark bound states in
very high energy processes is fragmentation, the splitting of a high energy
parton into a quarkonium state and other partons. We show that the
fragmentation functions $D(z,\mu)$ describing these processes can be calculated
using perturbative QCD. We calculate the fragmentation functions for a gluon to
split into S-wave quarkonium states to leading order in the QCD coupling
constant. The leading logarithms of $\mu/m_Q$, where $\mu$ is the factorization
scale and $m_Q$ is the heavy quark mass, are summed up using Altarelli-Parisi
evolution equations.


title: Could a nearby supernova explosion have caused a mass extinction?

abstract:
  We examine the possibility that a nearby supernova explosion could have
caused one or more of the mass extinctions identified by palaeontologists. We
discuss the likely rate of such events in the light of the recent
identification of Geminga as a supernova remnant less than 100 pc away and the
discovery of a millisecond pulsar about 150 pc away, and observations of SN
1987A. The fluxes of $\gamma$ radiation and charged cosmic rays on the Earth
are estimated, and their effects on the Earth's ozone layer discussed. A
supernova explosion of the order of 10 pc away could be expected every few
hundred million years, and could destroy the ozone layer for hundreds of years,
letting in potentially lethal solar ultraviolet radiation. In addition to
effects on land ecology, this could entail mass destruction of plankton and
reef communities, with disastrous consequences for marine life as well. A
supernova extinction should be distinguishable from a meteorite impact such as
the one that presumably killed the dinosaurs.


title: Heavy Quark Solitons

abstract:
  We investigate the heavy baryons which arise as solitonic excitations in a
``heavy meson" chiral Lagrangian which includes the light vector particles. It
is found that the effect of the light vectors may be substantial. We also
present a simple derivation which clearly shows the connection to the
Callan-Klebanov approach.


title:
Complete angular analysis of the decay cascade $B \rightarrow D^{**}(
  \rightarrow D^*(\rightarrow D \pi) + \pi) + W(\rightarrow l \nu)$

abstract:
  We develop a general algorithm for describing angular decay distributions in
cascade decay chains of arbitrary length. The general algorithm is used to
study joint angular decay distributions for the cascade decay $B\rightarrow
D^{**}( \rightarrow D^*(\rightarrow D \pi)+\pi) + W(\rightarrow l\nu)$ where
the $D^{**}$ is a generic $P$-wave charm meson state. Lepton mass effects are
fully incorporated


title: A Mass Spectrum for Leptons and Quarks

abstract:
  A suggestive phenomenological relation is found among the lepton and quark
masses which suggests a new insight into the problem of generations and also
gives a prediction for the top quark mass in agreement with the range of values
which is actually expected.


title:
Nonleptonic Cabibbo Favoured $B$-Decays and $CP$-Asymmetries for Charmed
  Final Hadron States in Isgur and Wise Theory

abstract:
  The Cabibbo allowed non-leptonic $B$-decays in two hadrons are studied,
within the factorization hypothesis, in the framework of Isgur and Wise theory
for the matrix elements of the $\Delta B=-\Delta C=\pm 1$ weak currents. The
$SU(2)_{HF}$ symmetry relates $|\Delta B|=1$ to $|\Delta C|=1$ currents, which
have been measured in the semileptonic strange decays of charmed particles. By
assuming colour screening and allowing for $SU(3)$ invariant contributions from
the annihilation terms with charmed final states one is able to comply with the
present experimental knowledge.\\ The $CP$ violating asymmetries in neutral $B$
decays are given for charmed final states in terms of the $K-M$ angles. With
the central values found for the annihilation parameters there is a destructive
(constructive) interference between the direct and annihilation terms in the
Cabibbo allowed (doubly forbidden) amplitudes for the decays into
$D^{0}(D^{*0})\pi^0$ and $D^0\rho^0$ so that they may be of the same order.
This would imply large asymmetries, for which however our present knowledge on
the amplitudes does not allow to predict even their sign.\\ We have better
confidence in our predictions for the charged final states than the neutral
ones and can draw the conclusion that the detection of the corresponding
asymmetries requires, at least, $10^6$ tagged neutral $B$-particles.


title: Baryons as solitons in Effective Chiral Quark - Meson Theory

abstract:
  The Nambu - Jona-Lasinio model in its SU(2) and SU(3) versions with scalar
and pseudoscalar coupling are applied to baryons. The parameters of the model
are fixed in the meson sector. The baryons arise as a soliton of three valence
quarks coupled to the Dirac sea (quark-antiquarks pairs). Within the SU(2)
version the nucleon static properties as well as some form factors, namely, the
electric and axial ones are described quite successfully. The nucleon-delta
splitting comes out reasonable. In medium the nucleonic soliton gets less
stable -- the mass is reduced whereas the radius increases. At some critical
medium density there is a clear delocalization of the soliton: The nucleon does
not exsist anymore as a soliton. In SU(3) version the strangness carrying
baryons are described as SU(3)-rotational excitations of the SU(2)-soliton
embedded in the SU(3)-sector. The mass splittings between the octet and
decuplet as well as within the multiplets are peproduced not only in a correct
oder but also in a good agreement with the experimantal values.


title: B=1 Soliton of the Nambu - Jona-Lasinio model in medium}

abstract:
  The solitonic sector of the Nambu - Jona-Lasinio model with baryon number one
is solved in the presence of an external medium. The calculations fully include
the polarization of both the Dirac sea and the medium as well as the Pauli
blocking effect. We found that with an increasing density the medium
destabilizes the soliton. At finite medium density the soliton mass gets
reduced whereas the mean square baryon radius shows an increase - a swelling of
the soliton. At some critical density of about two times nuclear matter density
there is no localized solution - the soliton disappears.


title:
Nucleon Properties and Restoration of Chiral Symmetry at Finite\nl
  Density and Temperature in an Effective Theory

abstract:
  Modifications of baryon properties due to the restoration of the chiral
symmetry in an external hot and dense baryon medium are investigated in an
effective chiral quark-meson theory. The nucleon arises as a soliton of the
Gell-Mann - L\'evi $\zs$-model, the parameters of which are chosen to be the
medium-modified meson values evaluated within the Nambu - Jona-Lasinio model.
The nucleon properties are obtained by means of variational projection
techniques. The nucleon form factors as well as the nucleon delta transition
form factors are evaluated for various densities and temperatures of the
medium. Similar to the chiral phase transition line the critical curve in the
$T-\zr$ plane for delocalization of the nucleon is non-monotonic and this
feature is reflected in all nucleon properties. At medium densities of about
$(2-3) \rnm$ the baryonic phase exists only at intermediate temperatures. For
finite temperature and densities the nucleon form factors get strongly reduced
at finite transfer momenta.


title:
$O(\alpha_S)$ Corrections to the Photon Structure Functions
  $F^\gamma_2(x,Q^2)$ and $F_L^\gamma(x,Q^2)$

abstract:
  We examine the QCD corrections to the structure functions $F_2^\gamma(x,Q^2)$
and $F_L^\gamma(x,Q^2)$ for a real photon target. The pointlike photon
contributions from light and heavy quarks are computed through
$O(\alpha\alpha_S)$. A parameterization of the hadronic (resolved) photon
contribution is also included and a comparison is made with the present
experimental data. We find that while the pointlike contributions are large for
$F_2^\gamma(x,Q^2)$, they are the dominant part of $F_L^\gamma(x,Q^2)$. For
$Q^2 > 50$ $({\rm GeV}/c)^2$ the charm component is as least as large as the
light quark component.


title: Numerical analysis of the Higgs mass triviality bound

abstract:
  Previous large $N$ calculations are combined with numerical work at $N=4$ to
show that the Minimal Standard Model will describe physics to an accuracy of a
few percent up to energies of the order 2 to 4 times the Higgs mass, $M_H$,
only if $M_H \le 710\pm60 ~ GeV$. This bound is the result of a systematic
search in the space of dimension six operators and is expected to hold in the
{\it continuum}. Given that studying the scalar sector in isolation is already
an approximation, we believe that our result is sufficiently accurate and that
further refinements would be of progressively diminishing interest to particle
physics. Note: The full ps file of this preprint is also available via
anonymous ftp to ftp.scri.fsu.edu. To get the ps file, ftp to this address and
use for username "anonymous" and for password your name. The file is in the
directory pub/vranas (to go to that directory type: cd pub/vranas) and is
called num_hig.ps (to get it type: get num_hig.ps)


title: Gluon Fusion: A Probe of Higgs Sector CP Violation

abstract:
  We demonstrate that CP violation in the Higgs sector, \eg\ of a multi-doublet
model, can be directly probed using gluon-gluon collisions at the SSC. %
requires phyzzx.tex macro package


title: Towards a theory of quark and lepton masses

abstract:
  Has any progress been made on understanding and predicting the 13 parameters
which describe the observed masses and mixing angles of the quarks and leptons?
Arguments are given in favor of pursuing schemes in which grand unified and
family symmetries provide many relations among these 13 parameters. A sequence
of simple assumptions leads to a supersymmetric SO(10) theory with 8
predictions: $\tan \beta, m_t, V_{cb}, m_s, m_s/m_d$, $m_u/m_d, V_{ub}$ and the
amount of CP violation $J$. These predictions are presented, together with
experiments which will test them.


title:
Valley Bifurcation in an $O(3)$ $\sigma$ Model: Implications for
  High-Energy Baryon Number Violation

abstract:
  The valley method for computing the total high-energy anomalous cross section
$S_{anom}$ is the extension of the optical theorem to the case of
instanton-antiinstanton backgrounds. As a toy model for baryon number violation
in Electroweak theory, we consider a version of the $O(3)$ $\sigma$ model in
which the conformal invariance is broken perturbatively. We show that at a
critical energy the saddle-point values of the instanton size and
instanton-antiinstanton separation bifurcate into complex conjugate pairs. This
nonanalytic behavior signals the breakdown of the valley method at an energy
where $S_{anom}$ is still exponentially suppressed.
  (Figures replaced 5/3/93).


title: Mirror fermions and LEP precision data

abstract:
  The three generation mirror fermion model is compared with LEP precision and
low energy data. While for zero mixing of ordinary and mirror fermions the
model is not favoured, for non zero mixing very low $\chi ^2 $ fits have been
obtained, in particular when right handed leptonic mixings are small and left
handed leptonic mixings are large (of the order of 0.1 radians.)


title: QCD Sum Rules and B Decays

abstract:
  We review some recent applications of QCD sum rules to $B$-decays. These
include the determination of the leptonic constant $f_B$ and of the
semileptonic transition amplitudes of the $B$-meson into negative and positive
parity charmed states.


title: The Breathing Mode in Extended Skyrme Model

abstract:
  We study an extended Skyrme model which includes fourth and sixth-order
terms. We explore some static properties like the $\Delta$-nucleon mass
splitting and investigate the Skyrmion breathing mode in the framework of the
linear response theory. We find that the monopole response function has a
pronounced peak located at $\sim$ 400 MeV, which we identify to the Roper
resonance $N(1440)$. As compared to the standard one, the extended Skyrme model
provides a more accurate description of baryon properties.


title: Theory Review of CP Violations in B Decays at Hadron Colliders

abstract:
  CP violations in B meson decays at hadron colliders are reviewed. In
particular I examine: $B^0-\bar{B^0}$ mixing and oscillations within Standard
Model and the Cabibbo-Kobayashi-Maskawa picture for CP violations; $B^0$ decays
into CP eigenstates and the measurements of the angles in the unitarity
triangle; finally I consider a class of charged $B$ decays that allow to avoid
uncertainties arising from the computation of hadronic matrix elements.


title: $B_c$ Physics at Hadron Colliders

abstract:
  In this paper we summarize the results of the theory working group dedicated
to the analysis of $B_c$ production at hadron colliders.


title: Unimagined Imaginary Parts in Heavy Quark Effective Field Theory

abstract:
  We argue that the imaginary parts of the anomalous dimensions in the
multiparticle sectors of heavy quark effective field theory may be removed by a
suitable redefinition of the multiparticle states. The connection between the
imaginary parts of the anomalous dimensions and the interquark potential is
pointed out


title: Rare and Radiative Kaon Decays

abstract:
  We review the status of theory and experiment of very rare and forbidden kaon
decays. We then review the radiative non-leptonic decays, and the associated
Dalitz pair modes. We pay particular attention to the study of long distance
physics in radiative decays within the framework of chiral perturbation theory
($\chi$PT). We discuss the experiments that will run in the near future and the
modes that they will be able to study.


title:
CP--odd Correlation in the Decay of Neutral Higgs Boson into $ZZ$,
  $W^+W^-$, or $t{\bar t}$

abstract:
  We investigate the possibility of detecting CP--odd angular correlations in
the various decay modes of the neutral Higgs boson including the modes of a
$ZZ$ pair, a $W^+W^-$ pair, or a heavy quark pair. It is a natural way to probe
the CP character of the Higgs boson once it is identified. Final state
interactions (i.e. the absorptive decay amplitude) is not required in such
correlations. As an illustrative example we take the fundamental source of the
CP nonconservation to be in the Yukawa couplings of the Higgs boson to the
heavy fermions. A similar correlation in the process $e^+e^- \to l^+ l^- H$ is
also proposed. Our analysis of these correlations will be useful for
experiments in future colliders such as LEP II, SSC, LHC or NLC.


title: Gluon Condensates at Finite Baryon Densities and Temperature

abstract:
  We derive here the equation of state for quark matter with a nontrivial
vacuum structure in QCD at finite temperature and baryon density. Using
thermofield dynamics, the parameters of thermal vacuum and the gluon condensate
function are determined through minimisation of the thermodynamic potential,
along with a self-consistent determination of the effective gluon and quark
masses. The scale parameter for the gluon condensates is related to the SVZ
parameter in the context of QCD sum rules at zero temperature. With inclusion
of quarks in the thermal vacuum the critical temperature at which the gluon
condensate vanishes decreases as compared to that containing only gluons. At
zero temperature, we similarly obtain the critical baryon density for the same
to be about 0.36 fm$^{-3}$.


title: The Emc Spin Crisis: Comparing Proton and Photon

abstract:
  The "kinematical" resolution of the $U_A(1)$ problem is proposed. The
cancellation of photonic and gluonic anomalies suggested by the t'Hooft
consistency principle naturally explains the zero singlet contributions to the
first moments of proton and photon spin structure functions. The new sum rule
for the photon spin structure function is derived. The strong strong
$Q^2$-dependence of the Gerasimov-Drell-Hearn sum rule is related to the $G_2$
structure function and to the gluonic anomaly.


title: g-modes and the Solar Neutrino Problem

abstract:
  We show that low-order g-modes with large enough amplitudes to affect
significantly the solar neutrino fluxes would produce surface velocities that
are $10^4$ times larger than the observed upper limits and hence are ruled out
by existing data. We also demonstrate that any large-amplitude, short-period
oscillations that grow on a Kelvin-Helmholtz time scale will require, to affect
solar neutrino fluxes, a large amount of energy (for g-modes, $10^9$ times the
energy in the observed $p-$ mode oscillations) and a tiny amount of dissipation
(for g-modes, $10^{-8}$ the dissipation rate of the $p$-modes).


title: Dynamical Supersymmetry Breaking at Low Energies

abstract:
  Conventional approaches to supersymmetric model building suffer from several
naturalness problems: they do not explain the large hierarchy between the weak
scale and the Planck mass, and they require fine tuning to avoid large flavor
changing neutral currents and particle electric dipole moments. The existence
of models with dynamical supersymmetry breaking, which can explain the
hierarchy, has been known for some time, but efforts to build such models have
suffered from unwanted axions and difficulties with asymptotic freedom. In this
paper, we describe an approach to model building with supersymmetry broken at
comparatively low energies which solves these problems, and give a realistic
example.


title:
Sparticle and Higgs Production and Detection at LEPII in two
  Supergravity Models

abstract:
  We study the most promising signals for supersymmetry at LEPII in the context
of two well motivated supergravity models: (i) the minimal $SU(5)$ supergravity
model including the stringent constraints from proton stability and a not too
young Universe, and (ii) a recently proposed string-inspired no-scale flipped
$SU(5)$ supergravity model. Our computations span the neutralino, chargino,
slepton, and Higgs sectors together with their interconnections in this class
of models. We find that the number of `mixed' (1-lepton + 2-jets + $\slash{p}$)
events occuring in the decay of pair-produced charginos ($\chi^\pm_1$) is quite
significant (per ${\cal L}=100\ipb$) for both models and that these predictions
do not overlap. That is, if $m_{\chi^\pm_1}<100\GeV$ then LEPII should be able
to exclude at least one of the two models. In the no-scale flipped $SU(5)$
model we find that the number of acoplanar di-electron events from selectron
pair production should allow for exploration of selectron masses up to the
kinematical limit and chargino masses indirectly as high as 150 GeV. We find
that the cross section $e^+e^-\to Z^*h$ deviates negligibly from the SM result
in the minimal model, whereas it can be as much as $1/3$ lower in the flipped
model. The usually neglected invisible mode $h\to\chi^0_1\chi^0_1$ can erode
the preferred $h\to 2\,{\rm jets}$ signal by as much as $40\%$ in these models.
We conclude that the charged slepton sector is a deeper probe than the
chargino/neutralino or Higgs sectors of the flipped $SU(5)$ model at LEPII,
while the opposite is true for the minimal $SU(5)$ model where the slepton
sector is no probe at all.


title: Fermions in Instanton Anti-Instanton Background

abstract:
  We consider the behaviour of fermions in the background of
instanton-anti\-instanton type configurations. Several different physics
problems, from the high energy electroweak interactions to the study of vacuum
structure of QCD and of large orders of perturbation theory are related to this
problem. The spectrum of the Dirac operator in such a background is studied in
detail. We present an approximation for the fermion correlation function when
the instanton-anti\-instanton separation ($R$) is large compared to their sizes
($\rho $). The situation when the instanton-anti\-instanton overlap and melt,
is studied through the behaviour of the Chern Simons number as a function of $
R/\rho$ and $x_4$.
  Applying our results to widely discussed cases of fermion-number violation in
the electroweak theory, we conclude that there are no theoretical basis for
expecting anomalous cross sections to become observable at energies in $10$ TeV
region.


title:
Two-loop renormalization constants and high energy $2\rightarrow 2$
  scattering amplitudes in the Higgs sector of the standard model

abstract:
  We calculate the complete matrix of two-body scattering amplitudes for the
scattering of longitudinally polarized gauge bosons $W_L^\pm$, $Z_L$ and Higgs
bosons to two loops in the high-energy, heavy-Higgs limit $\sqrt{s}\gg M_H\gg
M_W$. Use of the Goldstone boson equivalence theorem reduces the problem to one
involving only the scalar fields $w^\pm$, $z$ (the Goldstone bosons of the
original theory) and the Higgs boson. Renormalization of the scattering
amplitudes requires the calculation of the self-energy functions $\Pi
_i^0(M_i^2)$, the renormalization constants $Z_i$, and the bare quartic Higgs
coupling $\lambda _0$ to two loops. The results will be useful in other
calculations. To facilitate the calculations, we introduce a powerful new
technique for evaluating integrals over Feynman parameters in dimensional
regularization which is based on a Barnes' type representation of the binomial
expansion. We also collect some useful integrals which extend the tables given
by Devoto and Duke.


title: Two-loop unitarity constraints on the Higgs boson coupling

abstract:
  We use the results of Maher {\em et al.\/} (preceding paper) to construct the
matrix of $j=0$ partial-wave two-body and $2\rightarrow3$ scattering amplitudes
for the scattering of longitudinally polarized gauge bosons $W_L^\pm$, $Z_L$
and Higgs bosons $H$ correct to two loops in the high-energy, heavy-Higgs limit
$\sqrt{s}\gg M_H\gg M_W$. We show explicitly that the energy dependence of the
$2\rightarrow2$ amplitudes can be completely absorbed into a running quartic
Higgs coupling $\lambda_s= \lambda_s(s,M_H^2)$ and factors which involve small
anomalous dimensions and remain near unity. After diagonalizing the matrix of
partial-wave amplitudes, we use an Argand-diagram analysis to show that the
elastic scattering amplitudes are approximately unitary and weakly interacting
for $\lambda_s\alt2.3$, but that three-loop corrections are necessary to
restore unitarity for larger values of $\lambda_s$. That is, the interactions
in the Higgs sector of the standard model are effectively strong with respect
to the perturbative expansion for $\lambda_s\agt2.3$. The bound
$\lambda_s\alt2.3$ for a weakly interacting theory translates to a physical
Higgs mass $M_H\alt380$ GeV if the bound is to hold for energies up to a few
TeV, or $M_H\leq155$ GeV in perturbatively unified theories with mass scales of
order $10^{16}$ GeV.