title: Aspects of Standard Models with Two Higgs Doublets

abstract:
  We {works done in collaboration with C.S.Kim, Yonsei Univ., Seoul, Korea}
present some properties of the SM with two Higgs doublets. Unlike the minimal
SM, the Yukawa couplings (in the usual ``type II'' model) converge with the
increasing energy to flavor democracy (FD), i.e.~to common values, in a
specific flavor basis. This may represent a possible signal of some new,
(almost) flavor-blind physics beyond the SM. When imposing the assumption of
equality of the corresponding quark and leptonic Yukawa couplings at high
transition energies, we can estimate the physical mass of the tau-neutrino as a
function of $m_t$ and the VEV ratio. Furthermore, such an assumption would
effectively rule out the existence of the 4th generation of fermions.
  We {work done in collaboration with P.Overmann and E.A.Paschos, Dortmund
Univ., Germany} also investigated the most general framework of the SM with two
Higgs doublets such that no flavor-changing neutral currents (FCNC) occur at
the tree level. Finite 1-loop-induced FCNC (and CP-violating) effects, when
confronted with experimental con- straints from the physics of K and B mesons,
provide us with constraints on the values of the dominant Yukawa couplings of
the charged Higgs with the top quark. In the usual, more restrictive, ``type
II'' model, this would imply certain constraints on the value of the VEV ratio.


title:
Quark-Lepton Flavor Democracy and the Non-Existence of the Fourth
  Generation

abstract:
  In the Standard Model with two Higgs doublets (type II), which has a
consistent trend to a flavor gauge theory and its related flavor democracy in
the quark and the leptonic sectors (unlike the minimal Standard Model) when the
energy of the probes increases, we impose the mixed quark-lepton flavor
democracy at high ``transition'' energy and assume the usual see-saw mechanism,
and consequently find out that the existence of the fourth generation of
fermions in this framework is practically ruled out.


title: Neutralinos as Dark Matter Candidates

abstract:
  We review some properties of the neutralino as a candidate for dark matter in
the Universe. After presentation of evaluations for the neutralino relic
abundance, possibilities for its direct and indirect detections are discussed,
with emphasis for measurements at neutrino telescopes.


title: Massive two--loop diagrams: The Higgs propagator

abstract:
  Formulae are provided to express any two-loop scalar integral with arbitrary
masses and arbitrary external momenta in terms of an integral of one fairly
simple function or of its derivatives. Such integrals can be calculated
numerically with high precision. Good agreement is found with known analytical
expressions of specific two--loop diagrams. To prove the effectiveness of these
techniques, the two--loop selfenergy of the Higgs boson to order $(g^{2}
\frac{m_{H}^{2}}{m_{W}^{2}})^{2}$ is calculated, and the correctness of the
result is checked by using the unitarity of the S matrix. This result allows
one to disentangle the leading corrections to the shape of the Higgs resonance,
and to derive a perturbative bound of $\sim$1.2 TeV on the mass of the Higgs
boson.


title: Is the stop mass below the top mass?

abstract:
  It is shown that a top mass of 174+/-17 GeV, as quoted recently by the CDF
Collaboration, constrains the mixing angle between the Higgs doublets in the
Minimal Supersymmmetric extension of the Standard Model (MSSM) to: 1.2<tan
beta<5.5 at the 90% C.L.. The most probable value corresponds to tan beta =
1.56; such a small value causes a large mixing in the stop sector and the
lightest stop is likely to be below the top mass. In this case the stop
production in pp_bar collisions would contribute to the top signature, thus
providing a possible explanation for the large effective tt_bar cross section
observed by CDF.


title: Minimal String Unification and Constraint on Hidden Sector

abstract:
  We examine whether a minimal string model possessing the same massless
spectra as the MSSM can be obtained from $Z_4$, $Z_6$ and $Z_8$ orbifold
constructions. Using an anomaly cancellation condition of the target space
duality symmetry, we derive allowable values of a level $k_1$ of U(1)$_Y$ for
the minimal string model on the orbifolds through computer analyses. We
investigate threshold corrections of the gauge coupling constants of SU(3),
  SU(2) and U(1)$_Y$ and examine consistencies of the model with the LEP
experiments. Further we investigate what kinds of hidden sectors are consistent
with the minimal string models. Also their gauge coupling constants of the
hidden groups are estimated. We discuss Yukawa couplings of the models.


title:
Standard Model Predictions for Weak Boson Pair Production in E-E-
  Scattering

abstract:
  We study polarized $e^-e^-$ scattering into $\WW$, $\WZ$ and $\ZZ$ final
states within the framework of the standard model of electroweak interactions.
These mechanisms for producing pairs of weak gauge bosons are potential
backgrounds to new reactions beyond the realm of the standard model. At a
centre-of-mass energy of 500 GeV the total cross sections are calculated to be
2.5, 9.4 and 1.0 fb, respectively, for unpolarized beams. The energy behaviour
of the cross sections as well as particularly interesting differential
distributions are presented and the topology of the final states is discussed.


title: Fermion Scattering off Electroweak Bubble Wall and Baryogenesis

abstract:
  By treating CP-violating interaction as a perturbative term, we solve the
Dirac equation in the background of electroweak bubble wall (the distorted wave
Born approximation). We obtain the transmission and reflection coefficients for
a chiral fermion incident from the symmetric-phase region and for the one from
the broken-phase region respectively. There hold the respective sets of
unitarity relations and also reciprocity relations among them. These relations
enable us to rigorously derive quantum-number flux through the bubble wall,
which is the first order quantity of the CP violation. The flux is found to be
negligible for a thick wall such that $m_0/a\gsim 2$, where $1/a$ is the wall
thickness and $m_0$ is the fermion mass.


title: New representation of two-loop propagator and vertex functions

abstract:
  We present a new method of calculating scalar propagator and vertex functions
in the two-loop approximation, for arbitrary masses of particles. It is based
on a double integral representation, suitable for numerical evaluation. Real
and imaginary parts of the diagrams are calculated separately, so that there is
no need to use complex arithmetics in the numerical program.


title:
Finite Temperature Reduction of the SU(2) Higgs-Model with Complete
  Static Background

abstract:
  Direct evaluation of the 1-loop fluctuation determinant of non-static degrees
of freedom in a complete static background is advocated to be more efficient
for the determination of the effective three-dimensional model of the
electroweak phase transition than the one-by-one evaluation of Feynman
diagrams. The relation of the couplings and fields of the effective model to
those of the four-dimensional finite temperature system is determined in the
general 't Hooft gauge with full implementation of renormalisation effects.
Only field renormalisation constants display dependence on the gauge fixing
parameter. Characteristics of the electroweak transition are computed from the
effective theory in Lorentz-gauge. The dependence of various physical
observables on the three-dimensional gauge fixing parameter is investigated.


title: Radiative Leptonic Decays of Heavy Mesons

abstract:
  We compute the photon spectrum and the rate for the decays $B(D)\to
l\nu_l\gamma$ These photonic modes constitute a potentially large background
for the purely leptonic decays which are used to extract the heavy meson decay
constants. While the rate for $D\to l\n\g$ is small, the radiative decay in the
$B$ meson case could be of comparable magnitude or even larger than $B\to\m\n$.
This would affect the determination of $f_B$ if the $\tau$ channel cannot be
identified. We obtain theoretical estimates for the photonic rates and disscuss
their possible experimental implications.


title:
Single spin asymmetry in inclusive pion production, Collins effect and
  the string model

abstract:
  We calculate the single spin asymmetry in the inclusive pion production in
proton-proton collisions. We generate the asymmetry at the level of
fragmentation function (Collins effect) by the Lund coloured string mechanism.
We compare our results with the Fermilab E704 data from polarized proton-proton
collisions at 200 GeV. We show that the transversely polarized quark densities
at high Bjorken x strongly differ from these predicted by the SU(6) proton wave
function.


title:
Bounding Effective Operators at the One-Loop Level: The Case of
  Four-Fermion Neutrino Interactions

abstract:
  The contributions of non-standard four-neutrino contact interactions to
electroweak observables are considered at the one-loop level by using the
effective quantum field theory. The analysis is done in terms of three unknown
parameters: the strength of the non-standard neutrino interactions,
$\tilde{F}$, an additional derivative coupling needed to renormalize the
divergent contributions that appear when the four-neutrino interactions are
used at the loop level and a non-standard non-derivative $Z$-${\bar\nu} \nu$
coupling. Then, the precise measurements of the invisible width of the
$Z$-boson at LEP and the data on the neutrino deep-inelastic scattering yield
the result $\tilde{F} = (-100 \pm 140) G_F$. Assuming that there are no
unnatural cancellations between the contributions of the three effective
couplings a much stronger bound is obtained: $\abs{\tilde{F}}\ltap~ 2 G_F$,
which is a factor 200 better than the one obtained in previous analyses based
on tree level calculations.


title: Flavour in supersymmetric Grand Unification: a democratic approach

abstract:
  We consider the flavour problem in a supersymmetric Grand Unified theory with
gauged SU(6) group, where the Higgs doublets are understood as pseudo-Goldstone
bosons of a larger $\SU(6)\otimes\SU(6)$ global symmetry of the Higgs
superpotential. A key element of this work is that we never appeal to any
flavour symmetry. One main interesting feature emerges: only one of the light
fermions, an up-type quark, to be identified with the top, can get a Yukawa
coupling at renormalizable level. This fact, together with bottom-tau Yukawa
unification, also implied in our scheme, gives rise to a characteristic
correlation between the top and the Higgs mass. By including a flavour-blind
discrete symmetry and requiring that all higher dimensional operators be
mediated by the exchange of appropriate heavy multiplets, it is possible to
give an approximate description of all masses and mixing angles in term of a
hierarchy of grand unified scales. A special ``texture'' arises, implying a
relation between the top mass and the third generation mixing angles. Several
other possible consequences of this approach are pointed out, concerning the
$\mu/s$ mass ratio, the Cabibbo angle and the proton decay.


title: Nambu mass hierarchies in strings

abstract:
  We show that a recent proposal by Nambu to generate a hierarchy among Yukawa
couplings in the standard model may be easily implemented in superstring
models. In such models, two of the main ingredients of the Nambu proposal find
a natural explanation: minimising with respect to the Yukawas amounts to a
minimisation with respect to the underlying moduli fields and a constraint on
the Yukawas of the type of the Veltman condition may be attributed to the
relaxation process to a phenomenologically viable string vacuum.


title: Exponentiation of soft photons in a process involving hard photons

abstract:
  We present a simple method of removing the singularities associated with soft
photon emission to all orders in perturbation theory through exponentiation,
while keeping a consistent description of hard photon emission. We apply this
method to the process e+ e- --> mu+ mu- + n photons where we include both Z^0
and photon exchange and retain the muon mass dependence. The photonic radiation
is allowed to be radiated off any charged leg, and so we include all initial
and final state radiation, as well as all interference effects. The effect of
exponentiation is to suppress soft photon emission over the cross-section you
would obtain from working at strictly leading order. We also show how one would
extend the method to treat the collinear singularity; and remove the associated
leading mass logarithms.


title: Baryon Magnetic Moments in the 1/N Expansion

abstract:
  Relations among the baryon magnetic and transition magnetic moments are
derived in the $1/N_c$ expansion. Relations which hold to ALL ORDERS in $SU(3)$
breaking and to leading and first subleading orders in the $1/N_c$ expansion
are obtained. Additional relations are found which are valid up to $SU(3)$
breaking at first subleading order in the $1/N_c$ expansion. The experimental
accuracy of these relations fits the pattern predicted by the $1/N_c$
expansion. The predictions of the $1/N_c$ expansion are compared in detail with
those of the non-relativistic quark model. The $1/N_c$ expansion explains why
certain quark model relations work to greater accuracy than others.


title:
Natural explanation for discrete R-symmetry in successful inflation in
  N=1 supergravity

abstract:
  Recently it was shown that discrete R-invariance in superpotential can lead
to a successful flat potential in inflation. We suggest that this discrete
R-symmetry arises from an underlying supersymmetric gauge theory, which gives
rise to a scalar inflaton as a composite field.
  This discrete R-symmetry is common to the dynamical breaking scenarios in
global supersymmetry studied several years ago.
  Some extension of the R-invariance method is also shown.


title:
Calculation of the Four-Quark Condensates in the QCD Motivated
  Nambu-Jona- Lasinio Model

abstract:
  The four-quark condensates appearing in QCD sum rule are calculated
nonperturbatively in a realistic QCD motivated extended Nambu-Jona-Lasinio
model. The calculation is in the framework of the effective potential for local
composite operators up to next-to-the-leading order in the 1/N expansion in
which the non-factorized parts of the condensates are included. We show in this
paper the possibility of explaining the phenomenological enhancement factor
$~\kappa=2.4~$, needed for fitting the data in the factorization approximation,
as the contribution of the non-factorized parts of the four- quark condensates.


title:
On the Determination of $a_1$ and $a_2$ from Hadronic Two Body $B$
  Decays

abstract:
  {}From Class I decays : $B^o \ra \pi^+ ( \rho^+ ) + D^- ( {D^*}^- )$, we
determine $a_1$, and from Class III decays : $B^+ \ra \pi^+ ( \rho^+ ) +
\ol{D}^o ( {\ol{D}^*}^o )$, we determine an allowed domain in the $( a_1, a_2
)$ plane. We find that within one standard deviation errors, the allowed band
of $a_1$ from Class I decays is at least three standard deviations removed from
the allowed domain $( a_1, a_2 )$ from Class III decays.If we expand the
experimental errors to two standard deviations we do find a small intersection
between the $a_1$ band and the allowed $( a_1, a_2 )$ domain. The results
usually quoted in the literature lie in this intersection. We suggest : (1) an
independent measurement of the branching ratio for the Class III decay, $B^+
\ra \rho^+ \ol{D}^o $, (2) a high-statistics measurement of the branching ratio
of the Class I decay, $B \ra \ol{D} ( \ol{D}^* ) + D_s ( D_s^* )$ in both
charged states, and (3) a measurement of the longitudinal polarization fraction
in the Class III decay $B^+ \ra \rho^+ {\ol{D}^*}^o $ to shed more light on the
questions involved .


title:
QCD corrections to electroweak processes in an unconventional scheme:
  application to the b -> s gamma decay

abstract:
  In this work we give a detailed description of a method for the calculation
of QCD corrections to electroweak processes in dimensional regularization that
does not require any definition of the gamma_5 matrix in d dimensions. This
method appears particularly convenient in order to limit the algebraic
complexity of higher order calculations. As an example, we compute the leading
logarithmic corrections to the b -> s gamma decay.


title:
Gauge Invariance of Green Functions: Background-Field Method versus
  Pinch Technique

abstract:
  Application of the background-field method to QCD and the electroweak
Standard Model yields gauge-invariant effective actions giving rise to simple
Ward identities. Within this method, we calculate the quantities that have been
treated in the literature using the pinch technique. Putting the quantum gauge
parameter equal to one, we recover the pinch-technique results as a special
case of the background-field method. The one-particle-irreducible Green
functions of the background-field method fulfil for arbitrary gauge parameters
the desirable theoretical properties that have been noticed within the pinch
technique. Therefore the background-field formalism provides a general
framework for the direct calculation of well-behaved Green functions. Within
this formalism, the pinch technique appears as one of arbitrarily many
equivalent possibilities.


title: Electroweak effective lagrangians

abstract:
  In this paper I review several aspects of the use of effective lagrangians in
(mainly) electroweak physics. The conditions under which this approach is
reliable and useful, as well as the limitations of the formalism are detailed.
Various applications are also presented.


title: Heavy Quarks from QCD Spectral Sum Rules

abstract:
  This is a short review of the present status of the dynamics of the heavy
quarks extracted from QCD spectral sum rules. We discuss the determination of
the ``perturbative" quark mass, the decay constants of the $D$ and $B$ mesons,
the form factors of the semileptonic and radiative decays of the $B$ mesons,
the slope of the Isgur--Wise function and the emerged value of $V_{cb}$. We
mention shortly some properties of the hybrid and $B_c$ mesons.


title: Beauty Quark Fragmentation Into Strange B Mesons

abstract:
  Using the recent measurement of the total production rate for $B_s$ and
$B_s^*$ mesons in electron-positron annihilation to determine the strange quark
mass parameter in the $\bar b\to B_s,\, B_s^*$ fragmentation functions we
calculate the momentum distributions of the $B_s$ and $B_s^*$ mesons.


title: Probing quark gluon plasma with jets

abstract:
  We study multiple scatterings of jets on constituents of quark gluon plasma
and introduce energy--energy correlations to quantify their effects. The
effects from a longitudinally expanding plasma on medium as well as high energy
jets are found to be significant at both RHIC and LHC energies. Because jets
escape from the plasma long before the completion of mixed phase, these effects
are free from complications of final state hadronic interactions and decays.
These suggest that jets can be used to probe the plasma that might be created
in future high energy heavy ion collisions.


title: Baryons in the Large N Limit

abstract:
  The properties of baryons can be computed in a systematic expansion in
$1/N_c$, where $N_c$ is the number of colors. Recent results on the axial
couplings and masses of baryons (for the case of three flavors) are presented.
The results give insight into the structure of flavor $SU(3)$ breaking for
baryons.
----------------------------------------------------------------------------
Talks presented at the Symposium on Internal Spin Structure of the Nucleon
(Yale University, Jan 94) and at the Workshop on Continuous Advances in QCD
(Theoretical Physics Institute, University of Minnesota, Feb 94).


title: The Chiral Phase Transition and Instanton Anti-instanton Molecules

abstract:
  We explore the idea that the chiral phase transition in QCD can be described
as a transition from a disordered instanton liquid to a strongly correlated
phase of polarized instanton anti-instanton molecules. We find a number of non
perturbative effects caused by the presence of instantons above T_c, among them
the fact that instantons contribute to the euquation of state. We also study
how instantons affect the propagation of light quarks at high temperature and
determine the spacelike screening masses for mesons and baryons. We derive the
corresponding effective interaction and find that the interaction in the
scalar-pseudoscalar channel is attractive and four times stronger than the one
in the vector-axial-vector channel, in agreement with recent lattice QCD
simulations.


title:
On the Pais--Treiman method to measure $\pi\pi$ phase shifts in $K_{e4}$
  decays

abstract:
  We evaluate theoretical uncertainties to the method of Pais and Treiman to
measure the $\pi\pi$ phase shifts in $K_{e4}$ decays. We find that they are
very small, below $1\%$.


title:
Spin-dependent Parton Distributions from Polarized Structure Function
  Data

abstract:
  In the past year, polarized deep inelastic scattering experiments at CERN and
SLAC have obtained structure function measurements off proton, neutron and
deuteron targets at a level of precision never before achieved. The
measurements can be used to test the Bjorken and Ellis-Jaffe sum rules, and
also to obtain information on the parton distributions in polarized nucleons.
We perform a global leading-order QCD fit to the proton deep inelastic data in
order to extract the spin-dependent parton distributions. By using parametric
forms which are consistent with theoretical expectations at large and small
$x$, we find that the quark distributions are now rather well constrained. We
assume that there is no significant intrinsic polarization of the strange quark
sea. The data are then consistent with a modest amount of the proton's spin
carried by the gluon, although the shape of the gluon distribution is not well
constrained, and several qualitatively different shapes are suggested. The
spin-dependent distributions we obtain can be used as input to phenomenological
studies for future polarized hadron-hadron and lepton-hadron colliders.


title: Comment on current correlators in QCD at finite temperature

abstract:
  We address some criticisms by Eletsky and Ioffe on the extension of QCD sum
rules to finite temperature. We argue that this extension is possible, provided
the Operator Product Expansion and QCD-hadron duality remain valid at non-zero
temperature. We discuss evidence in support of this from QCD, and from the
exactly solvable two- dimensional sigma model O(N) in the large N limit, and
the Schwinger model.


title: Transformations of real-time finite-temperature Feynman rules

abstract:
  We consider transformations of the $2\times2$ propagator matrix in real-time
finite-temperature field theory, resulting in transformed $n$--point functions.
As special cases of such a transformation we examine the Keldysh basis, the
retarded/advanced $RA$ basis, and a Feynman-like $F\bar F$ basis, which differ
in this context as to how ``economically'' certain constraints on the original
propagator matrix elements are implemented. We also obtain the relation between
some of these real-time functions and certain analytic continuations of the
imaginary-time functions. Finally, we compare some aspects of these bases which
arise in practical calculations.


title: The Status of Molecules

abstract:
  This report summarizes the experimental and theoretical status of hadronic
molecules, which are weakly-bound states of two or more hadrons. We begin with
a brief history of the subject and discuss a few good candidates, and then
abstract some signatures for molecules which may be of interest in the
classification of possible molecule states. Next we argue that a more general
understanding of $2\to 2$ hadron-hadron scattering amplitudes will be crucial
for molecule searches, and discuss some of our recent work in this area. We
conclude with a discussion of a few more recent molecule candidates (notably
the $f_0(1710)$) which are not well established as molecules but satisfy some
of the expected signatures.


title:
The Photon Structure Function $F_2$ in QCD with Nonlocal Vacuum Quark
  Condensates

abstract:
  We calculate the contribution from nonlocal vacuum condensates of quark
fields to the hadronic part of the photon structure function $F_2(x)$ in the
operator product expansion approach to QCD. The result is a smooth function of
$x$ and its magnitude is comparable with one of gluon condensate. Extrapolation
to the case of real photon is realized with the help of the model, suggested by
Gorsky et al. As a result we obtain a substantial improvement of the agreement
with experimental data for the standard value of the parameter $\lambda_q^2
\equiv \langle\bar qD^2 q\rangle /\langle\bar qq\rangle \approx 0.5 \ \ GeV^2
$.}


title: Eikonal Wave Functions and Model Independent Exclusive B Decays

abstract:
  In this letter we investigate the proper normalization for the B meson
eikonal valence wave function used in exclusive B decays. The normalization
appropriate for a hard scattering process renormalized at the scale $\mu$ is
determined by calculating the short distance contribution to the purely
leptonic decay.


title: Is the Standard Electroweak Theory Happy with $m_t\sim$ 174 GeV?

abstract:
  Based on the recent CDF report on the top-quark, we have carried out an
analysis on the Higgs mass within the minimal standard electroweak theory using
the latest data on the $W$-mass. Although this theory is in quite a happy
situation now, we wish to point out that more precise measurements of $M_W$ and
$m_t$ in the future are crucial and they could come to require some new physics
beyond it.


title:
Model for anomalous $\Upsilon'' \to \Upsilon \pi \pi$ transition with
  account of chiral phase shift in hadron bag of quarkonium

abstract:
  We assume that a rather large bag of the $\Upsilon''(3S b\bar b)$ heavy
quarkonium is in the phase of spontaneously broken chiral symmetry, in contrast
to the $\Upsilon(1S b \bar b)$ hadron bag, having small size and being in the
phase of exact chiral symmetry, so that the shift of the phases in the
$\Upsilon'' \to \Upsilon \pi \pi$ transition is the additional source for the
$\pi\pi$ pairs. This source causes an anomalous $\pi\pi$ invariant mass
distribution, which is experimentally observed.


title:
Effective Meson Lagrangian with Chiral and Heavy Quark Symmetries from
  Quark Flavor Dynamics

abstract:
  By bosonization of an extended NJL model we derive an effective meson theory
which describes the interplay between chiral symmetry and heavy quark dynamics.
This effective theory is worked out in the low-energy regime using the gradient
expansion. The resulting effective lagrangian describes strong and weak
interactions of heavy $B$ and $D$ mesons with pseudoscalar Goldstone bosons and
light vector and axial--vector mesons. Heavy meson weak decay constants,
coupling constants and the Isgur--Wise function are predicted in terms of the
model parameters partially fixed from the light quark sector. Explicit
$SU(3)_F$ symmetry breaking effects are estimated and, if possible, confronted
with experiment.


title:
Wopper, Version 1.1: A Monte Carlo Event Generator for Four Fermion
  Production at LEP-II and Beyond

abstract:
  We report on the status of the Monte Carlo event generator WOPPER. Version
1.1 of WOPPER describes four fermion production at LEP-II and beyond with
leading logarithmic radiative corrections in the double W pole approximation.
These approximations are appropriate for almost all practical purposes, but the
inclusion of these finite width effects and radiative corrections is
nevertheless indispensable for LEP-II physics.


title: Polarization Rotation Effects due to Parity Violation in Atoms

abstract:
  We present a study of parity (P) violating polarization rotations of atoms in
external electric fields. Five different types of rotations are identified and
the consequences of time reversal invariance (T) are discussed. The role played
by Zeldovich's electric dipole moment of unstable states is elucidated. To
calculate the effects, we use the standard model of elementary particle physics
where P violation in atoms is due to the exchange of the Z boson between the
quarks in the nucleus and the atomic electrons. We consider in detail
hydrogen-like systems in $n=2$ states, especially $^1_1$H, $^4_2$He$^+$, and
$^{12}_6$C$^{5+}$. We discuss ways to obtain in some cases large enhancement
factors for the P-violating polarization rotations and show that e.g. for
$^1_1$H one could in principle observe rotations as large as a few percent,
where for a statistically significant result one would need a total of
$10^{15}$ polarized atoms. We point out that some of our P-violating
polarization rotations are very sensitive to the nuclear spin-dependent part of
the P-violating Hamiltonian which receives a contribution from the polarized
strange quark density in polarized nuclei.


title:
Bubble Nucleation in Theories with Symmetry Breaking by Radiative
  Corrections

abstract:
  A formalism is developed to calculate the bubble nucleation rate in theories
where the symmetry breaking is by radiative corrections. Although to leading
and next-to-leading order the result can be expressed in terms of the effective
action of the theory, this is not true of the higher order corrections. In
particular, the imaginary part of the effective potential does not explicitly
enter the calculation and the problems of interpretation which it would entail
are avoided. Based on a talk given at the NATO Advanced Research Workshop
Electroweak Physics and the Early Universe, Sintra, Portugal, March 25, 1994


title: GUT effects in the soft supersymmetry breaking terms

abstract:
  In minimal supergravity theories the soft supersymmetry breaking (SSB)
parameters are universal (flavor blind) near the Planck scale. Nevertheless,
one often assumes universality at the grand-unification scale $M_{G} \approx
10^{16}$ GeV instead, and corrections to the SSB parameters arising from their
evolution between the Planck and GUT scales are neglected. We study these
corrections and show that large splittings between the scalar mass parameters
can be induced at $M_{G}$. These effects are model dependent and lead to
significant uncertainties in the low-energy predictions of supersymmetric
models, in their correlations and in the allowed parameter space.


title:
An Upper Bound on the Higgs Boson Mass from Yukawa Unification and a
  Comment on Vacuum Stability Constraints

abstract:
  Only small regions in the $m_{t} - \tan\beta$ plane are allowed when
considering simultaneously (assuming the MSSM) coupling constant unification
and (minimal) GUT relations among Yukawa couplings (i.e., $h_{b} = h_{\tau}$ at
the unification point). In particular, if $m_{t} \simle 175$ GeV we find that
only $1 \simle \tan\beta \simle 1.5$ or $\tan\beta \simgr 40 \pm 10$ is
allowed. The former implies that the light Higgs boson is $\simle 110$ GeV and,
in principle, visible to LEPII. The prediction for the Higgs boson mass in the
$\tan\beta \approx 1$ scenario is discussed and uncertainties related to ($i$)
vacuum stability constraints, ($ii$) different methods for calculating the
Higgs boson mass, ($iii$) two-loop calculations and ($iv$) GUT corrections are
briefly reviewed. It is shown that large left-right mixing between the
$t$-scalars can significantly enhance the Higgs boson mass. That and an
ambiguity in the size of the two-loop correction lead to our conservative upper
bound of 110 GeV. Vacuum stability considerations constrain the $t$-scalar
mixing and slightly diminish the upper bound (depending on the value of
$m_{t}$). Improved two-loop calculations are also expected to strengthen the
bound.


title:
Heavy quark limit in the model with confined light quarks and infrared
  heavy quark propagators

abstract:
  We have studied the weak decay constants and the Isgur-Wise form factor of
the B and D mesons in the heavy quark limit, by employing a relativistic quark
confinement model. It is an attempt to improve our previous work within the
same line of thinking, but by incorporating a couple of novel aspects. First,
the infrared behavior of the heavy quark is considered by modifying its
conventional propagator in terms of a single parameter $\nu$. Second, the mass
difference of the heavy meson and heavy quark: $E=m_H-M_Q$ has been included.
It is found that the weak decay constants depend strongly on the mass
difference E with a relatively mild $\nu$ dependence. As for the Isgur-Wise
function it is controlled more sensitively by the infrared parameter $\nu$,
leading to its suppression at maximum meson recoil.


title: Decays of $\ell=1$ Baryons --- Quark Model versus Large-$N_c$

abstract:
  We study nonleptonic decays of the orbitally excited, \su6 \rep{70}-plet
baryons in order to test the hypothesis that the successes of the
nonrelativistic quark model have a natural explanation in the large-$N_c$ limit
of QCD. By working in a Hartree approximation, we isolate a specific set of
operators that contribute to the observed s- and d-wave decays in leading order
in $1/N_c$. We fit our results to the current experimental decay data, and make
predictions for a number of allowed but unobserved modes. Our tentative
conclusion is that there is more to the nonrelativistic quark model of baryons
than large-$N_c$.


title: Studies of Strong Electroweak Symmetry Breaking at Photon Colliders

abstract:
  It has recently been shown that the studies of strongly-interacting
electroweak symmetry breaking (EWSB) at photon colliders, via photon splitting
into $W$ pair followed by longitudinal $W$-boson scattering, could be possible.
Here we present a signal-background analysis for the scattering channels $W^+_L
W^-_L \to Z_L Z_L$ and $W^+_L W^-_L \to W^+_L W^-_L$ with background coming
from the standard model (SM) production of $\gamma\gamma \to WW ZZ$ and $WWWW$,
respectively. We illustrate the analysis using the SM with a heavy Higgs boson
$(m_H\approx 1$ TeV) to represent a typical strongly-interacting EWSB model and
the SM with a light Higgs boson ($m_H\approx 0.1$ TeV) to represent the
background. We come up with a set of kinematic acceptance to enhance the
signal-to-background ratio. Extension of the kinematic acceptance to other
strongly-interacting EWSB models is then trivial, and the signal cross sections
for various EWSB models are calculated. We found that it is very feasible to
probe the EWSB sector at a photon collider of center-of-mass energy of 2 TeV
with a luminosity of just 10~fb$^{-1}$.


title: Why more hadronlike photons produce less particles on nuclear targets

abstract:
  In hadron-nucleus interactions, the stronger is nuclear shadowing in the
total cross section the higher is the multiplicity of secondary hadrons. In
deep inelastic scattering, nuclear shadowing at small $x$ is associated with
the hadronlike behaviour of photons as contrasted to the pointlike behaviour in
the non-shadowing region of large $x$. In this paper we predict smaller mean
multiplicity of secondary hadrons, and weaker fragmentation of the target
nucleus, in deep inelastic leptoptoproduction on nuclei in the shadowing region
of small $x$ as compared to the non-shadowing region of large $x$. This
paradoxial conclusion has its origin in nuclear enhancement of the coherent
diffraction dissociation of photons. We present numerical predictions for
multiproduction in $\mu Xe$ interactions studied by the Fermilab E665
collaboration.


title: The Spectral Density Method Applied to the Hot Quantum Field Theories

abstract:
  The spectral density method being applied to the quantum field theory at
finite temperature is revived and its possibilities are briefly discussed.


title: Quantum Chromodynamics and Multiplicity Distributions

abstract:
  Quantum chromodymamics (QCD) approach to the problem of multiplicity
distributions in high energy particle collisions is described. The solutions of
QCD equations for generating functions of the multiplicity distributions in
gluon and quark jets are presented for both fixed and running coupling
constants. The newly found characteristics very sensitive to distribution
shapes is discussed. The predictions are confronted to experimental data.
Evolution of the multiplicity distributions with decreasing phase space windows
is considered and discussed in connection to the notions of intermittency and
fractality. Some other QCD effects are briefly described.


title: Four fermion production in e+ e- annihilation

abstract:
  Four fermion processes at e+ e- colliders in a range of energy from 100 GeV
to 1 TeV are discussed and examples of results obtained with an event generator
presented. We also investigate the effects of the inclusion of initial state
QED corrections and QCD contributions.


title: Four quark processes at LEP 200

abstract:
  In this paper I investigate the production of four quarks at LEP 200
energies. Effects due to initial state QED corrections and background diagrams,
including QCD contributions, are studied and examples of results obtained with
an event generator presented.


title: Quantum Scattering and Classical Solutions

abstract:
  I discuss a formalism for computing quantum scattering amplitudes using a
semiclassical expansion of a functional integral representation for the
S-matrix. The classical background for the expansion is determined by solving
the equations of motion subject to nontrivial boundary conditions determined by
the initial and final quantum states. The formalism is designed to accommodate
intrinsically nonperturbative processes such as baryon number violation,
quantum tunneling and multiparticle scattering. It appears to yield a
controlled small coupling expansion even at asymptotically high energies where
instanton methods fail. (Contribution to proceedings for Sintra '94 NATO
Workshop on
  Electroweak Physics and the Early Universe)


title: Single Leptoquark Production at Hadron Colliders

abstract:
  Leptoquarks can be produced in pairs by gluon--gluon fusion and
quark--antiquark annihilation at hadron colliders. While HERA is the proper
machine for single production of $(eu)$ and $(ed)$ type leptoquarks, the flavor
species of ($\mu u$), ($\mu d$) and ($\tau u$), ($\tau d$) type leptoquarks can
be produced at hadron colliders very efficiently. Besides exploiting
gluon-quark collisions, leptoquarks can also be produced singly by colliding
the quarks in one proton beam with leptons $e,\mu,\tau$ generated by splitting
photons which are radiated off the quarks in the other proton beam. For Yukawa
couplings of the size $\alpha$ leptoquark masses up to about 300~GeV can be
generated at the Tevatron while the LHC can produce leptoquarks with masses up
to about 3~TeV. [Leptoquarks involving heavy quarks can be produced singly at a
lower rate, determined by the heavy flavor flux in the proton beam.]


title: Soft Pion Emission in Semileptonic $B$-Meson Decays

abstract:
  An analysis of semileptonic decays of $B$ mesons with the emission of a
single soft pion is presented in the framework of the heavy-quark limit using
an effective Lagrangian which implements chiral and heavy-quark symmetries. The
analysis is performed at leading order of the chiral and inverse heavy mass
expansions. In addition to the ground state heavy mesons some of their
resonances are included. The estimates of the various effective coupling
constants and form factors needed in the analysis are obtained using a chiral
quark model. As the main result, a clear indication is found that the $0^{+}$
and $1^{+}$ resonances substantially affect the decay mode with a $D^{\ast}$ in
the final state, and a less dramatic effect is also noticed in the $D$ mode. An
analysis of the decay spectrum in the $D^{(\ast)}-\pi$ squared invariant mass
is carried out, showing the main effects of including the resonances. The
obtained rates show promising prospects for studies of soft pion emission in
semileptonic $B$-meson decays in a $B$-meson factory where, modulo experimental
cuts, about $10^5$ such decays in the $D$ meson mode and $10^4$ in the
$D^{\ast}$ mode could be observed per year.


title: Pion Wave Function from QCD Sum Rules with Nonlocal Condensates

abstract:
  We investigate a model QCD sum rule for the pion wave function
$\varphi_{\pi}(x)$ based on the non-diagonal correlator whose perturbative
spectral density vanishes and $\Phi(x,M^2)$, the theoretical side of the sum
rule, consists of condensate contributions only. We study the dependence of
$\Phi(x,M^2)$ on the Borel parameter $M^2$ and observe that $\Phi(x,M^2)$ has a
humpy form, with the humps becoming more and more pronounced when $M^2$
increases. We demonstrate that this phenomenon reflects just the oscillatory
nature of the higher states wave functions, while the lowest state wave
function $\varphi_{\pi}(x)$ extracted from our QCD sum rule analysis,has no
humps, is rather narrow and its shape is close to the asymptotic form
$\varphi_{\pi}^{as}(x) = 6x(1-x)$.


title: Minimal String Unification and Yukawa Couplings in Orbifold Models

abstract:
  We study the minimal supersymmetric standard model derived from $Z_N \times
Z_M$ orbifold models. Moduli dependent threshold corrections of the gauge
couplings are investigated to explain the measured values of the coupling
constants. Also we study Yukawa couplings of the models. We find that the $Z_2
\times Z_6'$, $Z_2\times Z_6$, $Z_3 \times Z_6$ and $Z_6 \times Z_6$ orbifold
models have the possibility to derive Yukawa couplings for the second and third
generations as well as the measured gauge coupling constants. Allowed models
are shown explicitly by combinations of modular weights for the matter fields.


title:
$b \rightarrow s \gamma$ AND $b \rightarrow s g$: A THEORETICAL
  REAPPRAISAL

abstract:
  We present upgraded theoretical predictions for inclusive and exclusive
radiative decays of {\it B} mesons. Our results include those next-to-leading
order corrections that have already been computed. Our best estimates in the
Standard Model are $BR(B \rightarrow K^* \gamma)=(4.3 \pm 0.9^{ +1.4}_{-1.0})
\times 10^{-5}$, $BR(B \rightarrow X_s \gamma) =(1.9 \pm 0.2\pm 0.5) \times
10^{-4}$, $\Gamma(B \rightarrow K^* \gamma)/ \Gamma(B \rightarrow X_s
\gamma)=0.23 \pm 0.09$ and $BR(B \rightarrow X_s g)= (1.57 \pm 0.15
^{+0.86}_{-0.59} \pm 0.23) \times 10^{-3}$. We also consider limits found with
two-Higgs-doublet models.


title: Another Look at the Electroweak Vortex Solution

abstract:
  We discuss the position in configuration space of the electroweak vortex
solution. (Talk given at the NATO Advanced Research Workshop "Electroweak
Physics and the Early Universe", Sintra, Portugal, March 1994)


title: The Breaking of Subnuclear Democracy as the Origin of Flavour Mixing

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


title: Damping Rate of a Yukawa Fermion at Finite Temperature

abstract:
  The damping of a massless fermion coupled to a massless scalar particle at
finite temperature is considered using the Braaten-Pisarski resummation
technique. First the hard thermal loop diagrams of this theory are extracted
and effective Green's functions are constructed. Using these effective Green's
functions the damping rate of a soft Yukawa fermion is calculated. This rate
provides the most simple example for the damping of a soft particle. To leading
order it is proportional to $g^2T$, whereas the one of a hard fermion is of
higher order.


title:
Scaling behaviour of leptonic decay constants for heavy quarkonia and
  heavy mesons

abstract:
  In the framework of QCD sum rules one uses a scheme, allowing one to apply
the conditions of both nonrelativistic heavy quark motion inside mesons and
independence of nonsplitting nS-state density on the heavy quark flavours. In
the leading order an analitic expression is derived for leptonic constants of
both heavy quarkonia and heavy mesons with a single heavy quark. The expression
allows one explicitly to determine scaling properties of the constants.


title: Constraints on Four-Point Couplings in Low-Energy Meson Interactions

abstract:
  We investigate from first principles the introduction of isospin-1 vector and
axial-vector fields into the nonlinear sigma model. Chiral symmetry is
nonlinearly realised and spin-1 fields are assumed to transform homogeneously
under chiral rotations. By requiring the Hamiltonian of the theory to be
bounded from below we find inequalities relating three- and four-point meson
couplings. This leads to a low-energy phenomenological Lagrangian for the
nonanomalous sector of $\pi\rho a_1$ strong interactions.


title:
Low-Energy Effective Lagrangian in Unified Theories with Non-Universal
  Supersymmetry Breaking Terms

abstract:
  Supersymmetric grand unified theories with non-universal soft supersymmetry
breaking terms are studied. By integrating out the superheavy fields at an
unification scale, we compute their low-energy effective Lagrangian. We find
new contributions to the scalar potential specific to the non-universal
supersymmetry breaking. $D$-term contribution to the scalar masses is one
example. The gauge hierarchy achieved by a fine-tuning in the superpotential
would be violated in general due to the non-universal SUSY breaking terms. We
show, however, it is preserved for a certain class of the soft terms derived
from a {\em hidden} ansatz. We also discuss some phenomenological implications
of the non-universal supersymmetry breaking, including predictions of the
radiative electroweak symmetry breaking scenario and of no-scale type models.


title:
Comparison of SO(10)-Symmetric Fermion Mass Matrices with and without
  Degenerate Neutrinos

abstract:
  It has been recently suggested by others that one can simultaneously explain
the depletions of solar electron-neutrinos and atmospheric muon-neutrinos along
with a 7 eV neutrino component of mixed dark matter by postulating the
existence of nearly-degenerate 2 eV neutrinos with the correct mixing
parameters. We study this claim in the framework of a simple SO(10)-symmetric
model constructed from the low scale data using a bottom-up procedure recently
advanced by the authors and compare the results with and without degenerate
neutrinos.


title: Existence and Stability of Spinning Embedded Vortices

abstract:
  I show the existence of a new type of vortex solution which is non-static but
stationary and carries angular momentum. This {\it spinning vortex} can be
embedded in models with trivial vacuum topology like a model with
$SU(2)_{global}\times U(1)_{local} \rightarrow U(1)_{global}$ symmetry
breaking. The stability properties of the embedded spinning vortex are also
studied in detail and it is shown that stability improves drastically as
angular momentum increases. The implications of this result for vortices
embedded in the standard electroweak model are under study.


title: Supersymmetry at the DiTevatron

abstract:
  We study the signals for supersymmetry at the Tevatron and DiTevatron
($\sqrt{s}=4\TeV$) in various well-motivated supersymmetric models. We consider
the trilepton signature in the decay of pair-produced charginos and
neutralinos, the missing energy signature in gluino and squark production, and
the $b\bar b$ signal in the decay of the lightest supersymmetric Higgs boson
produced in association with a $W$ or $Z$ boson. In each case we perform signal
and background studies, using Monte Carlo and/or real data to estimate the
sensitivity to these signals at the Tevatron and DiTevatron with the Main
Injector, for short- and long-term integrated luminosities of ${\cal L}=10$ and
$25\ifb$, and $5\sigma$ statistical significance. We conclude that one could
probe chargino masses as high as $m_{\chi^\pm_1}\sim180\,(200)\GeV$, gluino
masses as high as $m_{\tilde g}\sim450\,(750)\GeV$, and lightest Higgs boson
masses as high as $m_h\sim110\,(120)\GeV$ at the Tevatron (DiTevatron). A
high-luminosity option at the Tevatron ($10^{33}\cm^{-2}\s^{-1}$) may
compensate somewhat for the higher reach of the DiTevatron, but only in the
trilepton and Higgs signals. However, these gains may be severely compromised
once the multiple-interaction environment of the high-luminosity Tevatron is
accounted for.


title:
Gauge-Coupling Unification and the Minimal SUSY Model: A Fourth
  Generation Below the Top?

abstract:
  We explore the possibility of a fourth generation in the
gauge-coupling-unified, minimal supersymmetric (MSSM) framework. We find that a
sequential fourth generation (with a heavy neutrino $\nu'$) can still fit,
surviving all present experimental constraints, provided
$\lambda_b(M_U)=\lambda_\tau(M_U)$ Yukawa unification is relaxed. For the
theory to remain perturbative up to $M_U$, the new leptonic generation must lie
within reach of LEP-II and the new $b',t'$ must have masses within the reach of
the Tevatron. For example, for $\mt>150\gev$ we find $m_{\nu'},m_{\tau'}<
86\gev$, $m_{t'}<178$, and $m_{b'}<156\gev$. Experiments at Fermilab are
already sensitive to the latter mass regions; we comment on direct $b'$
searches and on the $m_{t'}\simeq \mt$ case in light of new CDF data. Discovery
may involve novel decay signatures; however, CDF and LEP-II will confirm or
exclude an MSSM fourth generation in the near future.


title:
Proton-Proton Elastic Scattering; Landshoff Contributions in the Diquark
  Model

abstract:
  Independent multiple scattering (`Landshoff') contributions to proton-proton
elastic scattering at wide angles are calculated in the quark-diquark model.
Results confirm previous observations about the magnitude of these
contributions. The use of the quark-diquark model extends the applicability of
perturbative QCD calculations down to lower values of momentum transfer
substantially.


title: New Approach for Measuring $|V_{ub}|$ at Future $B$-Factories

abstract:
  It is suggested that the measurements of hadronic invariant mass ($m_X$)
distributons in the inclusive $B \rightarrow X_{c(u)} l \nu$ decays can be
useful in extracting the CKM matrix element $|V_{ub}|$. We investigated
hadronic invariant mass distributions within the various theoretical models of
HQET, FAC and chiral lagrangian as well as ACCMM model. It is also emphasized
that the $m_X$ distribution even at the region $m_{X} > m_{D}$ in the inclusive
$b\rightarrow u$ are effetive in selecting the events, experimentally viable at
the future asymmetric $B$ factories, with better theoretical understandings.


title: Gluon and Charm Distributions in the Photon

abstract:
  We study systematically the sensitivity of the photon structure function data
on the gluon contents of the photon, by using the leading order
Altarelli--Parisi (AP) equations.
  Charm quark contribution is studied in the quark parton model and by using
the massive quark AP equations of Gl\"uck, Hoffmann and Reya.
  The present photon structure function data are found to allow wide range of
gluon distributions in the photon.
  We give a set of six scale-dependent parton distributions in the photon
(WHIT1 to WHIT6), which have systematically different gluon contents.
  Sensitivity of the structure function at small $x$ and that of the total
charm quark production cross section to the effective gluon distribution are
discussed.


title: SUSY GUTs without light Higgs bosons

abstract:
  There are two different types of perturbative unification in SUSY GUTs.
Perturbative gauge unification is necessary for the extremely successful
prediction of $\sin^2\theta_w$. ``Perturbative validity'' requires that {\it
all} couplings (not just the gauge couplings) remain small; this assumption is
essential to the proof that any SUSY GUT must have a light Higgs with a mass
below 140 GeV. It is pointed out here that if the latter bound is violated (so
that there need be no light Higgs bosons), then it is plausible that the
successful prediction of $\sin^2\theta_w$ will {\it not} be significantly
altered.


title: A light stop and its consequences at the Tevatron and LEPII

abstract:
  An interesting prediction of a string-inspired {\em one-parameter}
$SU(5)\times U(1)$ supergravity model, is the fact that the lightest member
($\tilde t_1$) of the top-squark doublet $(\tilde t_1,\tilde t_2)$, may be
substantially lighter than the top quark. This sparticle ($\tilde t_1$) may be
readily pair-produced at the Tevatron and, if $m_{\tilde t_1}\lsim130\GeV$,
even be observed at the end of Run IB. Top-squark production may also be an
important source of sought-for top-quark signatures in the dilepton and
$\ell$+jets channels. Therefore, a re-analysis of the top data sample in the
presence of a possibly light top-squark appears necessary before definitive
statements concerning the discovery of the top quark can be made. Such a light
top-squark is linked with a light supersymmetric spectrum, which can certainly
be searched for at the Tevatron through trilepton and squark-gluino searches,
and at LEPII through direct $\tilde t_1$ pair-production (for $m_{\tilde
t_1}\lsim100\GeV$) and via chargino and Higgs-boson searches.


title: Measuring Parton Densities in the Pomeron

abstract:
  We present a program to measure the parton densities in the pomeron using
diffractive deep inelastic scattering and diffractive photoproduction, and to
test the resulting parton densities by applying them to other processes such as
the diffractive production of jets in hadron-hadron collisions. Since QCD
factorization has been predicted NOT to apply to hard diffractive scattering,
this program of fitting and using parton densities might be expected to fail.
Its success or failure will provide useful information on the space-time
structure of the pomeron.


title:
Towards a dynamical determination of parameters in the Minimal
  Supersymmetric Standard Model

abstract:
  In the Minimal Supersymmetric Standard Model (MSSM), the scale $M_{SUSY}$ of
soft supersymmetry breaking is usually {\em assumed} to be of the order of the
electroweak scale. We reconsider here the possibility of treating $M_{SUSY}$ as
a dynamical variable. Its expectation value should be determined by minimizing
the vacuum energy, after including MSSM quantum corrections. We point out the
crucial role of the cosmological term for a dynamical generation of the desired
hierarchies $m_Z, M_{SUSY} << M_P$. Inspired by four-dimensional superstring
models, we also consider the Yukawa couplings as dynamical variables. We find
that the top Yukawa coupling is attracted close to its effective infrared fixed
point, corresponding to a top-quark mass in the experimentally allowed range.
As an illustrative example, we present the results of explicit calculations for
a special case of the MSSM.


title:
Measurement of the WW-Gamma Vertex Through Single Photon Production at
  e^+ e^- Colliders

abstract:
  We perform a detailed study of the process $e^+e^-\to\gamma\nu_l\bar\nu_l$
and its sensitivity to anomalous gauge boson couplings of the $\gamma WW$
vertex. We concentrate on LEP II energies, $\sqrt{s}=200$ GeV, and energies
appropria- te to the proposed Next Linear Collider (NLC) high energy $e^+e^-$
collider with c.m. energies of 500 GeV and 1 TeV. At 200 GeV, the process
offers, at best, a consistency check of other processes being considered at
LEP-200. At 500 GeV, the parameters $\kappa_\gamma$ and $\lambda_\gamma$ can be
measured to about $\pm 0.05$ and $\pm 0.1$ respectively at 95\% C.L. while at 1
TeV, they can be measured to about $\pm 0.02$. At the high luminosities
anticipa- ted at high energy linear colliders precision measurements are likely
to be limited by systematic rather than statistical errors.


title:
Gauge independent transverse and longitudinal self-energies and vertices
  via the pinch technique

abstract:
  In the context of the Standard Model we show how to apply the pinch technique
to four-fermion amplitudes with non-conserved external charged currents,in
order to construct to one-loop order gauge independent self-energies and
vertices. We discuss the technical difficulties arising due to the presence of
longitudinal contributions from the W and Goldstone boson ($\phi$) propagators,
and derive gauge independent $WW$, $\phi W$, and $\phi\phi$ effective
self-energies, and vertices. The quantities so constructed satisfy a set of
Ward identities, whose validity enforces the gauge invariance of the physical
amplitude considered; their derivation does not require knowledge of the
explicit closed form of the gauge independent self-energies and vertices. Use
of these Ward identities enables the decomposition of the amplitude in
manifestly gauge independent transverse and longitudinal structures with
distinct kinematic properties. Explicit one-loop calculations are carried out,
and several applications of the results are briefly discussed.}


title: Light-Ray Operators and their Application in QCD

abstract:
  The nonperturbative parton distribution and wave functions are directly
related to matrix elements of light-ray (nonlocal) operators. These operators
are generalizations of the standard local operators known from the operator
product expansion. The renormalization group equation for these operators leads
to evolution equations for more general distribution amplitudes which include
the Altarelli-Parisi and the Brodsky-Lepage equations as special cases. It is
possible to derive the Altarelli-Parisi kernel as a limiting case of the
extended Brodsky-Lepage kernel. As new application of the operator product
expansion the virtual Compton scattering near forward direction is considered.


title: The Parton Distribution Functions in the Limit $x_{Bj}\to 1$

abstract:
  We review both the counting rule and the influence of the evolution in $Q^2$
for the large $x_{Bj}$ behaviour of the valance quark distribution functions.
Based on a factorization procedure we present a more general perturbative
treatment to compute this behaviour. A complete analysis is performed in the
scalar $\phi^3_{[6]}$-theory for the parton distribution function of the
``meson'', which shows that logarithmical corrections arise from the
distribution amplitude and that the reference momentum square $Q_0^2$ is fixed
by $x_{Bj}$.


title: Quark Pair Production in the Chiral Phase Transition

abstract:
  The production of quarks and antiquarks during a sudden restoration of chiral
symmetry, as it might occur in very energetic heavy ion collisions, is
considered. If gluons are already present they can assist additively to the
overall production: real gluons are partially decaying during such a chiral
transition. The total number of produced quarks is calculated and found to be
quite sizeable. It is speculated that such a phenomenon could give rise to a
significant contribution to the overall quark pair creation in the
preequilibrium stage of the heavy ion collision.


title: Nonfactorizable Contributions to Nonleptonic Weak Decays of Heavy Mesons

abstract:
  Nonfactorizable contributions to exclusive two-body nonleptonic weak decays
of heavy mesons arising from color octet currents, characterized by the
parameter $r_2$, are extracted from the data. It is found that $r_2$ is equal
to $\sim -0.67\,$, $-(0.9\sim 1.1),~-(1.2\sim 1.3)$, $\sim 0.36$ respectively
for $D\to \bar{K}\pi,~\bar{K}^*\pi,~\bar{K}^*\rho,~\bar{B}\to D\pi$ decays. As
expected, soft-gluon effects become stronger when the decay particles are less
energetic, allowing more time for significant final-state strong interactions.
As a consequence, the parameter $a_2$ is not universal and is channel or class
dependent, contrary to the anticipation of the factorization approach. The
leading $1/N_c$ expansion works most successfully for $D\to\bar{K}\pi$ decays
as the subleading $1/N_c$ factorizable contribution is almost compensated by
the soft-gluon effect. We argue that, in contrast to what happens in $B^-\to
D^{(*)} \pi(\rho)$ decays, the nonfactorizable term and the subleading $1/N_c$
factorizable term in $\bar{B}\to \psi\bar{K}^{(*)}$ decays are opposite in
signs, in accordance with a recent QCD sum rule calculation. Implications are
discussed.


title: Quark Masses from Lattice QCD at the Next-to-Leading Order

abstract:
  Using the results of several quenched lattice simulations, we predict the
value of the strange and charm quark masses in the continuum at the
next-to-leading order, $m^{\overline{MS}}_s(\mu=2\,\, \rm{GeV})= (127 \pm
18)\,\, \rm{MeV}$ and $m^{\overline{MS}}_{ch}(\mu=2 \,\,\rm{GeV})=(1.47 \pm
0.28)\,\, \rm{GeV}$. The errors quoted above have been estimated by taking into
account the original statistical error of the lattice results and the
uncertainties coming from the matching of the lattice to the continuum theory.
A detailed presentation of the relevant formulae at the next-to-leading order
and a discussion of the main sources of errors is also presented.


title: Phase of the Wilson Line at High Temperature in the Standard Model

abstract:
  We compute the effective potential for the phase of the Wilson line at high
temperature in the standard model to one loop order. Besides the trivial vacua,
there are metastable states in the direction of $U(1)$ hypercharge. Assuming
that the universe starts out in such a metastable state at the Planck scale, it
easily persists to the time of the electroweak phase transition, which then
proceeds by an unusual mechanism. All remnants of the metastable state
evaporate about the time of the $QCD$ phase transition.


title: Beyond the black disk limit: antishadow scattering mode

abstract:
  The appearance of the antishadow scattering mode at Tevatron-Collider
energies is considered on the basis of unitarity and geometrical notions on
hadron interactions


title:
Monte Carlo simulation of baryon and lepton number violating processes
  at high energies

abstract:
  We report results obtained with the first complete event generator for
electroweak baryon and lepton number violating interactions at supercolliders.
We find that baryon number violation would be very difficult to establish, but
lepton number violation can be seen provided at least a few hundred L violating
events are available with good electron or muon identification in the energy
range 10 GeV to 1 TeV.


title: Charge form factors of pseudoscalar mesons

abstract:
  The elastic charge form factors of the pion, kaon, D- and B-mesons are
calculated within a relativistic constituent quark model formulated on the
light-cone. Our parameter free predictions agree well with the available data.
The results are approximately independent of the assumed form of the light-cone
wave function, in particular they do not depend on the high momentum tail of
the wave function for energies accessible to present experiments.


title:
The 2-Loop Effective Potential of the 3d SU(2)-Higgs Model in a General
  Covariant Gauge

abstract:
  To study the convergence of the loop expansion at the high-temperature
electroweak phase transition, we calculate the 2-loop effective potential of
the 3d SU(2)-Higgs model in a general covariant gauge. We find that the loop
expansion definitely breaks down for large $\xi$, but converges rather well for
smaller values, deep in the broken phase.


title: Deep Inelastic Electropion Production

abstract:
  This paper is devoted to a study of possible scaling laws, and their
logarithmic corrections, occurring in deep inelastic electropion production.
Both the exclusive and semi-exclusive processes are considered. Scaling laws,
originally motivated from PCAC and current algebra considerations are examined,
first in the framework of the parton model and QCD peturbation theory and then
from the more formal perspective of the operator product expansion and
asymptotic freedom, (as expressed through the renormalization group). We
emphasize that these processes allow scaling to be probed for the full
amplitude rather than just its absorbtive part (as is the case in the
conventional structure functions). Because of this it is not possible to give a
formal derivation of scaling for deep inelastic electropion production
processes even if one believes that they are unambiguously sensitive to the
light cone behavior of the operator product. The origin of this is shown to be
related to its behavior near $x\approx 0$. Investigations, both theoretical and
experimental, of these processes is therefore strongly encouraged.


title: Z Condensation and Standard Model Baryogenesis

abstract:
  The standard model satisfies Sakharov's conditions for baryogenesis but the
CP violation in the KM matrix appears too small to account for the observed
asymmetry. In this letter we explore a mechanism through which CP violation can
be greatly amplified.
  First CP is {\it spontaneously} broken through dynamical effects on bubble
walls, and the two CP conjugate phases grow through phase ordering. Direct
competition between macroscopic regions of both phases then amplifies the
microscopic CP violation to a point where one of the two phases predominates.
This Letter is devoted to a demonstration that spontaneous CP violation may
indeed occur on propagating bubble walls via the formation of a condensate of
the longitudinal $Z$ boson.


title:
The Background Field Method: Alternative Way of Deriving the Pinch
  Technique's Results

abstract:
  We show that the background field method (BFM) is a simple way of deriving
the same gauge-invariant results which are obtained by the pinch technique
(PT). For illustration we construct gauge-invariant self-energy and three-point
vertices for gluons at one-loop level by BFM and demonstrate that we get the
same results which were derived via PT. We also calculate the four-gluon vertex
in BFM and show that this vertex obeys the same Ward identity that was found
with PT.}


title: CP Violation: Present and Future

abstract:
  We review the present status of CP violation in the standard model.
Subsequently we make an excursion in the future in order to see what we could
expect in this field in this and the next decade. We present various strategies
for the determination of the CKM parameters and divide the decays into four
classes with respect to theoretical uncertainties. We emphasize that the
definitive tests of the Kobayashi-Maskawa picture of CP violation will come
through a {\it simultaneous} study of CP asymmetries in $B_{d,s}^o$ decays, the
rare decays $K^+ \to \pi^+\nu \bar\nu$ and $K_L \to \pi^o\nu\bar\nu$, and
$x_d/x_s$. We illustrate how the measurements of the CP asymmetries in
$B^0_{d,s}$-decays together with a measurement of $Br(K_L\to
\pi^\circ\nu\bar\nu)$ or $Br(\kpnn)$ and the known value of $\mid V_{us}\mid $
can determine {\it all} elements of the Cabibbo-Kobayashi-Maskawa matrix
essentially without any hadronic uncertainties.


title: Semi-Analytical Approach to Higgs Production at LEP 2

abstract:
  The cross-section for the reaction $e^+e^- \rightarrow b\bar{b}\mu^+\mu^-$ is
calculated with a semi-analytical integration of the phase space. Compact
formulae are obtained for the total cross section and for invariant mass
distributions of the $\mu^+\mu^-$ and $b\bar{b}$ pairs. The background diagrams
to $ZH$ production yield analytically cumbersome but numerically small
contributions. The numerical results are compared with those from a Monte Carlo
approach.


title:
One-Particle Inclusive Processes in Deeply Inelastic Lepton-Nucleon
  Scattering

abstract:
  The one-particle inclusive cross section in deeply inelastic lepton--nucleon
scattering, expressed in terms of parton densities and fragmentation functions
being differential in the invariant mass of the observed hadron and of the
incoming nucleon, diverges if this invariant mass vanishes. This divergence can
be traced back to the kinematical configuration where the parent parton of the
observed hadron is emitted collinearly from the incoming parton of the QCD
subprocess. By using the concept of ``fracture functions'', which has recently
been introduced by Trentadue and Veneziano, it is possible to absorb this
divergence in these new distribution functions as long as the observed hadron
is not soft. This procedure allows the determination of a finite one-particle
inclusive cross section in next-to-leading order QCD perturbation theory. We
give details of the calculation and the explicit form of the bare fracture
functions in terms of the renormalized ones.


title:
Effective light front quantization of scalar field theories and
  two-dimensional electrodynamics

abstract:
  We introduce a new method to include condensates in the light-cone
Hamiltonian. By using a Gaussian approximation to the ordinary vacuum in a
theory close to the light front, we derive an effective Hamiltonian on the
light cone, which has new terms reflecting the nontriviality of the vacuum. We
demonstrate our method for scalar $\phi^4$-theory and the massive Schwinger
model.


title: Non-Debye Screening in Finite Temperature QCD

abstract:
  We study the non-abelian, gauge invariant, screening potential between two
charges in a quark-gluon plasma. Using Braaten and Pisarski resummed
perturbation theory in temporal axial gauge, we find a repulsive power screened
potential which behaves as $\sim 1/r^6$ at large distance. This questions
either the physical meaning of the Debye mass or the known pragmatic treatment
of the temporal axial gauge propagator.


title: QCD Transport Theory

abstract:
  Because of the long range of the gauge interactions, the collective behaviour
of quarks and gluons plays a decisive role in the transport processes.
Collective effects, like Debye screening and Landau damping, remove the
unphysical infrared divergences of the transport cross-sections and provide
finite relaxation rates. I review here a theory of the plasma collective
excitations that has been recently developed. It is based on kinetic equations
derived from the general QCD Dyson-Schwinger equations, in the weak coupling
limit. I present new, truly non-abelian, collective excitations, which
correspond to nonlinear color oscillations of the QCD plasma.


title:
Issues in Light Meson Spectroscopy: The Case for Meson Spectroscopy at
  Cebaf

abstract:
  I review some outstanding issues in meson spectroscopy. The most important
qualitative issue is whether hadrons with explicit gluonic degrees of freedom
exist. To answer this question requires a much better understanding of
conventional $q\bar{q}$ mesons. I therefore begin by examining the status of
conventional meson spectroscopy and how the situation can be improved. The
expected properties of gluonic excitations are discussed with particular
emphasis on hybrids to give guidance to experimental searches. Multiquark
systems are commented upon as they are likely to be important in the mass
region under study and will have to be understood better. In the final section
I discuss the opportunities that CEBAF can offer for the study of meson
spectroscopy.


title: Instanton Contribution to $B \rightarrow X_{s} \gamma $ Decay

abstract:
  We study instanton effects on $B \rightarrow X_s\gamma$ decay using the heavy
quark effective field theory and the operator product expansion. In the dilute
gas approximation the effect is negligibly small. This is in contrast to the
result of the instanton effect in inclusive semileptonic $b\rightarrow u$ decay
but similar to the inclusive hadronic $\tau$ decay. We discuss the similarities
and differences of the $B \rightarrow X_s\gamma$ decay compared to inclusive
hadronic $\tau$ decay and semileptonic $B$ decay.


title: Constraints on Supergravity in the Light Gluino Scenario

abstract:
  Minimal $N=1$ supergravity with a radiatively broken electroweak symmetry
group is studied in the light gluino scenario. Constraints from the
$b\rightarrow s\gamma$ decay and from the masses of the light CP-even neutral
Higgs $m_h$, the lightest chargino $m_{\chi^{\pm}_1}$, and the second lightest
neutralino $m_{\chi^0_2}$ are analyzed. We consider models in which the
relation $A=B+m_0$ holds. We plot the allowed region in the $\tan\beta-\mu$
plane consistent with chargino/neutralino searches, and an upper bound on
$\tan\beta$ given by 1.82 (1.85) for $\mu>0$ ($\mu<0$) is found. We analize the
consistency of this upper bound with experimental constraints on the lightest
Higgs mass. We find that a gluino with a mass of a few GeV is incompatible with
this kind of models.


title: The Higgs Boson Width is Adjustable

abstract:
  We show that it is possible to construct models in which the width of the
Higgs boson is arbitrary - either smaller or larger than a standard model Higgs
boson of the same mass. There are no new fields into which the Higgs boson
decays. Instead, the coupling of the Higgs boson to the gauge bosons is
adjusted. We construct and analyze weakly--coupled models with arbitrary--width
Higgs bosons to investigate the phenomenology one might find in a strongly
interacting model. In any such model new physics must enter at a mass scale
which decreases as the Higgs boson width is adjusted away from its standard
model value. In particular, if the Higgs boson is wider than the standard model
Higgs boson, then interesting new physics must appear in the isospin--two
channel.


title: Time-Like Shock Hadronization of a Supercooled Quark-Gluon Plasma

abstract:
  We study the energy-momentum and baryonic number conservation laws for
quark-gluon plasma discontinuity transitions into hadron matter states. We find
that the time-like shock hadronization of a supercooled quark-gluon plasma
(when the normal vector to the discontinuity hypersurface is time-like) should
take place. We consider some properties of this process, which is different
from the standard space-like shock hadronization.


title: Principles of Chiral Perturbation Theory

abstract: Lectures given at the Workshop "Hadrons 1994", Gramado, RS, Brasil


title:
On the Determination of $|V_{ub}|$ from Inclusive Semileptonic Decay
  Spectra

abstract:
  We propose a model independent method to determine $|V_{ub}|$ from the energy
spectrum of the charged lepton in inclusive semileptonic $B$ decays. The method
includes perturbative QCD corrections as well as nonperturbative ones.


title:
Classical Transport Theory and Hard Thermal Loops in the Quark-Gluon
  Plasma

abstract:
  Classical transport theory for colored particles is investigated and employed
to derive the hard thermal loops of QCD. A formal construction of phase-space
for color degrees of freedom is presented. The gauge invariance of the
non-Abelian Vlasov equations is verified and used as a guiding principle in our
approximation scheme.We then derive the generating functional of hard thermal
loops from a constraint satisfied at leading-order by the color current. This
derivation is more direct than alternative ones based on perturbative quantum
field theory, and shows that hard thermal effects in hot QCD are essentially
{\it classical}. As an illustration, we analyze color polarization in the QCD
plasma.


title: On the QCD corrections to $b \to s \gamma$ in supersymmetric models

abstract:
  We reinvestigate the leading QCD corrections to the radiative decay $b \to s
\gamma for supersymmetric extensions of the Standard Model. Although the major
contributions to the corrections originate from the running of the effective
Lagrangian from the W scale down to the $b$ scale, additional corrections are
expected from large mass splittings between the particles running in the loops,
as well as from integrating out heavy particles at scales different from the W
mass. The calculation is performed in the framework of effective field
theories.


title: On The Spin-Dependent Potential Between Heavy Quark And Antiquark

abstract:
  A new formula for the heavy quark-antiquark spin dependent potential is given
by using the techniques developed in the heavy quark effective theory. The
leading logarithmic quark mass terms emerging from the loop contributions are
explicitly extracted and summed up. There is no renormalization scale ambiguity
in this new formula. The spin-dependent potential in the new formula is
expressed in terms of three independent color-electric and color-magnetic field
correlation functions, and it includes both the Eichten-Feinberg's formula and
the one-loop QCD result as special cases.


title:
Standard Model CP-violation and Baryon asymmetry Part I: Zero
  Temperature

abstract:
  We consider quantum effects in a world with two coexisting symmetry phases,
unbroken and spontaneously broken, as a result of a first order phase
transition. The discrete symmetries of the problem are discussed in general. We
compute the exact two-point Green function for a free fermion, when a thin wall
separates the two phases. The Dirac propagator displays both massive and
massless poles, and new CP-even phases resulting from the fermion reflection on
the wall. We discuss the possible quark-antiquark CP asymmetries produced in
the Standard Model(SM) for the academic $T=0$ case. General arguments indicate
that an effect first appears at order $\alpha_W$ in the reflection amplitude,
as the wall acts as a source of momentum and the on-shell one-loop self-energy
cannot be renormalized away. The asymmetries stem from the interference of the
SM CP-odd couplings and the CP-even phases in the propagator. We perform a toy
computation that indicates the type of GIM cancellations of the problem. The
behaviour can be expressed in terms of two unitarity triangles.


title:
Standard Model CP-violation and Baryon asymmetry Part II: Finite
  Temperature

abstract:
  We consider the scattering of quasi-particles off the boundary created during
a first order electroweak phase transition. Spatial coherence is lost due to
the quasi-quark damping rate, and we show that reflection on the boundary is
suppressed, even at tree-level. Simply on CP considerations, we argue against
electroweak baryogenesis in the Standard Model via the charge transport
mechanism. A CP asymmetry is produced in the reflection properties of quarks
and antiquarks hitting the phase boundary. An effect is present at order
$\alpha_W^2$ in rate and a regular GIM behaviour is found, which can be
expressed in terms of two unitarity triangles. A crucial role is played by the
damping rate of quasi-particles in a hot plasma, which is a relevant scale
together with $M_W$ and the temperature. The effect is many orders of magnitude
below what observation requires.


title: Triviality, perturbation theory and $Z\to b \overline b$

abstract:
  We compute the large-$m_t$ contributions to the $Zb\overline b$ vertex in the
Standard Model non-perturbatively using both the $1/\nc$ and the $1/\nf$
expansions. Triviality and its consequences for the perturbative result are
systematically analyzed. In particular, we point out that the effect of
triviality is already important at the two-loop level for a heavy Higgs
($600\gev<M_H<1\tev$) even when the top mass is below $200\gev$.


title:
On Measuring $CP$ Violation in Neutral $B$-meson Decays at the $\Upsilon
  (4S)$ Resonance

abstract:
  Within the standard model we carry out an analysis of $CP$-violating
observables in neutral $B$-meson decays at the $\Upsilon (4S)$ resonance. Both
time-dependent and time-integrated $CP$ asymmetries are calculated, without
special approximations, to meet various possible measurements at symmetric and
asymmetric $e^{+}e^{-}$ $B$ factories. We show two ways to distinguish between
direct and indirect $CP$-violating effects in the $CP$-eigenstate channels such
as $B^{0}_{d}/\bar{B}^{0}_{d}\rightarrow \pi^{+}\pi^{-}$ and $\pi^{0} K_{S}$.
Reliable knowledge of the Cabibbo-Kobayashi-Maskawa phase and angles can in
principle be extracted from measurements of some non-$CP$-eigenstate channels,
e.g. $B^{0}_{d}/\bar{B}^{0}_{d}\rightarrow D^{\pm}\pi^{\mp}$ and
$\stackrel{(-)}{D}$$^{(*)0}K_{S}$, even in the presence of significant
final-state interactions.


title: On the Unitarity Triangles of the CKM Matrix

abstract:
  The unitarity triangles of the $3\times 3$ Cabibbo-Kobayashi-Maskawa (CKM)
matrix are studied in a systematic way. We show that the phases of the nine CKM
rephasing invariants are indeed the outer angles of the six unitarity triangles
and measurable in the $CP$-violating decay modes of $B_{d}$ and $B_{s}$ mesons.
An economical notation system is introduced for describing properties of the
unitarity triangles. To test unitarity of the CKM matrix we present some
approximate but useful relations among the sides and angles of the unitarity
triangles, which can be confronted with the accessible experiments of quark
mixing and $CP$ violation.


title: On Test of CPT Symmetry in CP Violating B Decays

abstract:
  Considering that the existing experimental limit for $CPT$ violation is still
poor, we explore various possible ways to test $CPT$ symmetry in $CP$-violating
$B$ decays at $e^{+}e^{-}$ $B$ factories and hadron machines. We find that it
is difficult to distinguish between the effect of direct $CP$ violation and
that of $CPT$ violation in the time-integrated measurements of neutral $B$
decays to $CP$ eigenstates such as $\psi K_{S}$ and $\pi^{+}\pi^{-}$. Instead,
a cleaner signal of small $CPT$ violation may appear in the time-integrated
$CP$ asymmetries for a few non-$CP$-eigenstate channels, e.g.,
$B^{0}_{d}/\bar{B}^{0}_{d}\rightarrow D^{\pm}\pi^{\mp}$ and
$\stackrel{(-)}{D}$$^{(*)0}K_{S}$. The time-dependent measurements of $CP$
asymmetries are available, in principle, to limit the size of $CPT$-violating
effects in neutral $B$-meson decays.


title:
Minimal Supersymmetric Higgs Boson Decay Rate in O(\alpha_s^2)
  Perturbative QCD

abstract:
  A short presentation of the results of the analytical evaluation of the
O(\alpha_s^2) QCD contributions in the fermionic decay rates of the neutral
CP-odd minimal supersymmetric Higgs particle is made. The corrections due to
the nonvanishing quark masses are included. The results are presented both in
terms of running and pole quark masses.


title: On the coupling of heavy mesons to pions in QCD

abstract:
  We compute the strong coupling constant $g_{P^* P \pi}$, with $P$ and $P^*$
respectively pseudoscalar and vector heavy mesons by using the QCD sum rules
approach. Our computation is based on the evaluation of the time ordered
product of currents between the vacuum and the soft pion state. The so-called
parasitic terms are taken into account and give a contribution to the sum rule
of the same order of the lowest lying state, while higher dimension non
perturbative terms have small numerical effects. The infinite heavy quark mass
limit is also examined.


title: Symmetry Principles toward Solutions of $\mu$ Problem

abstract:
  We stress that a natural solution of the $\mu$ problem requires two
ingredients: a symmetry that would enforce $\mu = 0$ as well as the occurence
of a small breaking parameter that generates a nonzero $\mu$. It is suggested
that both the Peccei-Quinn symmetry and the spontaneously broken $R$ symmetry
may be the sources of the needed $\mu$ term in the minimal supersymmetric
standard model provided that they are spontaneously broken at a scale
$10^{10}-10^{12}$ GeV. To solve the strong CP problem with a hidden sector
confining group, both of these symmetries are needed in superstring models with
an anomalous $U(1)_A$.


title: Fluctuations at Phase Transitions

abstract:
  We use the closed time-path formalism to calculate fluctuations at phase
transitions, both in and out of equilibrium. Specifically, we consider the
creation of vortices by fluctuations, of relevance to the early universe and to
$^{4}He$ superfluidity. (Invited talk to Nato Advanced Research Workshop on
Electroweak Physics and the Early Universe, Sintra (Portugal), March 1994)


title:
Parameterization Invariance and the Resolution of the Unitary Gauge
  Puzzle

abstract:
  We examine the calculation of the critical temperature $T_c$ for the
restoration of a spontaneously broken symmetry. Motivated by a set of recently
developed gauge dependence identities, we give a gauge and parameterization
independent definition of this temperature in terms of the physical mass of the
scalar particle as determined by the propagator pole. As an explicit
illustration, we consider the Abelian Higgs model in the unitary gauge, where
the usual definition of the critical temperature based upon the effective
potential leads to an erroneous result. We show how the gauge invariant
definition reproduces the correct result as found in the ``renormalizable''
parameterizations.


title: Quartic Mass Corrections to $R_{had}$

abstract:
  The influence of nonvanishing quark masses on the total cross section in
electron positron collisions and on the $Z$ decay rate is calculated. The
corrections are expanded in $m^2/s$ and $\as$. Methods similar to those applied
for the quadratic mass terms allow to derive the corrections of order $\as
m^4/s^2$ and $\as^2m^4/s^2$. Coefficients which depend logarithmically on
$m^2/s$ and which cannot be absorbed in a running quark mass arise in order
$\as^2$. The implications of these results on electron positron annihilation
cross sections at LEP and at lower energies in particular between the charm and
the bottom threshold and for energies several GeV above the $b\bar b$ threshold
are discussed.


title: Strong and Radiative $D^\ast$ Decays

abstract:
  We use the relativistic light--front quark model to show that both strong and
radiative $D^\ast$ decays are in good agreement with the 1992 CLEO II results.
In particular the coupling for $D^{\ast}\ra D \pi$ is consistent with the
experimental upper limit. The key point is the relativistic treatment of the
quark spin.


title: Electroweak Baryogenesis and the Standard Model

abstract:
  Electroweak baryogenesis is addressed within the context of the standard
model of particle physics. Although the minimal standard model has the means of
fulfilling the three Sakharov's conditions, it falls short to explaining the
making of the baryon asymmetry of the universe. In particular, it is
demonstrated that the phase of the CKM mixing matrix is an insufficient source
of {\it CP} violation. The shortcomings of the standard model could be bypassed
by enlarging the symmetry breaking sector and adding a new source of {\it CP}
violation.


title: Top Ten Models Constrained by b to s gamma

abstract:
  The radiative decay b to s gamma is examined in the Standard Model and in
nine classes of models which contain physics beyond the Standard Model. The
constraints which may be placed on these models from the recent results of the
CLEO Collaboration on both inclusive and exclusive radiative $B$ decays is
summarized. Reasonable bounds are found for the parameters in some cases.


title:
Unification Constraints in the Next-to-Minimal Supersymmetric Standard
  Model

abstract:
  We perform a renormalisation group analysis of the next-to-minimal
supersymmetric standard model (NMSSM) based on the following constraints:
two-loop gauge coupling unification at a variable scale $M_X$, running the
gauge couplings through the low energy thresholds; universal soft supersymmetry
breaking parameters; correct electroweak symmetry breaking. The
phenomenological implications of our results include a standard model-like
Higgs boson of mass in the range 70-140 GeV.


title:
Tau Leptons and Top Quarks in a `Non-Local' Baryogenesis at the
  Electroweak Phase Transition

abstract:
  Baryon asymmetry can be generated at the first order electroweak phase
transition, provided there is a CP violation on the bubble wall. In this report
we discuss the role of leptons and quarks in the `non-local' baryogenesis
mechanism.


title: A Novel Kind of Neutrino Oscillation Experiment

abstract:
  A novel method to look for neutrino oscillations is proposed based on the
elastic scattering process $\bar{\nu}_{i} e^{-}\rightarrow \bar{\nu}_{i}
e^{-}$, taking advantage of the dynamical zero present in the differential
cross section for $\bar{\nu}_{e} e^{-}\rightarrow \bar{\nu}_{e} e^{-}$. An
effective tunable experiment between the "appearance" and "disappearance"
limits is made possible. Prospects to exclude the allowed region for
atmospheric neutrino oscillations are given.


title: A Model for the Origin and Mechanisms of CP Violation

abstract:
  In this talk I will show that the two-Higgs doublet model with vacuum CP
violation and approximate global $U(1)$ family symmetries may provide one of
the simplest and most attractive models for understanding the origin and
mechanisms of CP violation. It is shown that the mechanism of spontaneous
symmetry breaking provides not only a mechanism for generating masses of the
bosons and fermions, but also a mechanism for creating CP-phases of the bosons
and fermions, so that CP violation occurs, after spontaneous symmetry breaking,
in all possible ways from a single CP phase of the vacuum and is generally
classified into four types of CP-violating mechanism. A new type of
CP-violating mechanism in the charged Higgs boson interactions of the fermions
is emphasized and can provide a consistent description for both established and
reported CP-, P- and T-violating phenomena. Of particular importance is the new
source of CP violation for charged Higgs boson interactions that lead to the
value of $\epsilon'/\epsilon$ as large as $10^{-3}$ independend of the CKM
phase. (Invited Talk at the 5th Conference on the Intersections of Particle and
Nuclear Physics, May 31-June 6, 1994, at St. Petersburg, Florida, to appear in
the Proceedings)


title: On the problem of the magnetic mass

abstract:
  The dynamical generation of a transverse gauge field mass is studied by means
of gap equations for pure gauge theory and the gauged non-linear sigma model in
three dimensions. Non-trivial solutions to the gap equations are found
indicating that this type of mass generation is a feature of the static sector
of finite temperature field theory. In the case of the non-linear sigma model
the transverse mass can be defined in a manifestly gauge invariant manner. Its
value is determined to be m=0.28g^2.


title: Axion Dissipation Through the Mixing of Goldstone Bosons

abstract:
  By coupling axions strongly to a hidden sector, the energy density in
coherent axions may be converted to radiative degrees of freedom, alleviating
the ``axion energy crisis''. The strong coupling is achieved by mixing the
axion and some other Goldstone boson through their kinetic energy terms, in a
manner reminiscent of paraphoton models. Even with the strong coupling it
proves difficult to relax the axion energy density through particle absorption,
due to the derivative nature of Goldstone boson couplings and the effect of
back reactions on the evolution of the axion number density. However, the
distribution of other particle species in the hidden sector will be driven from
equilibrium by the axion field oscillations. Restoration of thermal equilibrium
results in energy being transferred from the axions to massless particles,
where it can redshift harmlessly without causing any cosmological problems.


title: The Detection of Cold Dark Matter with Neutrino Telescopes

abstract:
  High energy neutrinos are produced by the annihilation of dark matter
particles in our galaxy. These are presently searched for with large area, deep
underground neutrino telescopes. Cold dark matter particles, trapped inside the
sun, are an abundant source of such neutrinos. Back-of-the-envelope
calculations are sufficient to demonstrate how neutrino telescopes are
competitive with existing and future particle colliders such as the LHC in the
search for weakly interacting massive cold dark matter particles. We will
emphasize that a $1\,\rm km^2$ area is the natural scale for a future
instrument capable of probing the full GeV--TeV mass range of cold dark matter
particle candidates by searching for high energy neutrinos produced by their
annihilation in the sun. We speculate on what such a detector may look like.


title:
Generational Mass Splitting of Neutrinos in High Temperature
  $SU(2)_{\scriptscriptstyle{L}}\otimes U(1)$ Gauge Theory

abstract:
  We calculate the generational mass splitting of neutrinos in high temperature
$SU(2)_{\scriptscriptstyle{L}}\otimes U(1)$ gauge theory when the temperature
is above $250$ GeV and the gauge symmetry is restored. We consider the case of
neutrinos that are massless at tree level as well as the case of neutrinos with
tree-level mass and large mixing.


title:
An Effective Chiral Lagrangian Approach to Kaon-Nuclear Interactions:
  Kaonic atom and kaon condensation

abstract:
  On-shell kaon-nucleon scattering, kaonic atom and kaon condensation are
treated on the same footing by means of a chiral perturbation expansion to the
next-to-next-to-leading order (``N$^2$LO"). Constraining the low-energy
constants in the chiral Lagrangian by on-shell $KN$ scattering lengths and
kaonic atom data, the off-shell s-wave scattering amplitude up to one-loop
order corresponding to N$^2$LO and the critical density of kaon condensation up
to in-medium two-loop order are computed. The effects on kaon-proton scattering
of the quasi-bound $\Lambda (1405)$ and on kaonic atoms and kaon condensation
of $\Lambda (1405)$-proton-hole excitations through four-Fermi interactions are
studied to all orders in density within the in-medium two-loop approximation.
It is found that the four-Fermi interaction terms in the chiral Lagrangian play
an essential role in providing attraction for kaonic atoms, thereby inducing
condensation but the critical density is remarkably insensitive to the strength
of the four-Fermi interaction that figures in kaonic atoms. The prediction for
the critical density is extremely robust and gives -- for ``natural" values of
the four-Fermi interactions -- a rather low critical density, $\rho_c \lsim 4
\rho_0$. When the BR scaling is suitably implemented, the condensation sets in
at $\rho_c\simeq 2\, \rho_0$ with loop corrections and four-Fermi interactions
playing a minor role.


title: A Variational Approach to the Spinless Relativistic Coulomb Problem

abstract:
  By application of a straightforward variational procedure we derive a simple,
analytic upper bound on the ground-state energy eigenvalue of a
semirelativistic Hamiltonian for (one or two) spinless particles which
experience some Coulomb-type interaction.


title:
CP Conserving and Violating Contributions to
  $K_L\to\pi^+\pi^-\nu\bar{\nu}$

abstract:
  We study both CP conserving and violating contributions to the decay
$K_L\to\pi^+\pi^-\nu\bar{\nu}$. We find that the decay branching ratio is
dominated by the CP conserving part. In the standard CKM model, we estimate
that for $m_t\sim 174\ GeV$, the branching ratio due to the CP conserving
(violating) contributions can be as large as $4.4 \times 10^{-13}$ ($1.0\times
10^{-14}$).


title: Unification of Fundamental Interactions in Supersymmetry

abstract:
  A review is given of recent developments on the implications of supergravity
grand unification with SU(5)-type proton decay under the condition $M_{H_3}
/m_G < 10$ (where $M_{H_3}$ is the Higgs triplet mass) and the naturalness
condition that the universal scalar mass $m_0$ and the gluino mass are $<$
1~TeV. It is shown that the maximum achievable lifetime limits on proton
lifetime at Super Kamiokande and ICARUS will exhaust the full parameter space
of the model under the constraint $m_{\tilde W_1} >$~100~GeV. Thus the model
predicts the observation of either a light chargino with mass $\lappeq$~100~GeV
, or the observation of a $\bar \nu K^+$ mode at Super Kamiokande and ICARUS
within the above naturalness constraints.Analysis of the $b \rightarrow s\gamma
$ branching ratio within this model is also discussed. It is shown that there
is a significant region of the parameter space where the branching ratio
predicted by the model lies within the current experimental bounds. It is
pointed out that improved measurements of $B(b\rightarrow s\gamma)$ will
significantly delineate the parameter space of the model and allow for a more
stringent determination of their allowed ranges.


title: Parton Distributions of the Proton

abstract:
  To obtain improved parton densities of the proton, we present a new global
analysis of deep inelastic and related data including, in particular, the
recent measurements of $F_2$ at HERA, of the asymmetry of the rapidity
distributions of $W^\pm$ production at the FNAL $pp$ collider and of the
asymmetry in Drell-Yan production in $pp$ and $pn$ collisions. We also
incorporate data to determine the flavour dependence of the quark sea
distributions. We find that the behaviour of the partons at small $x$ is
consistent with the precocious onset of BFKL leading $\log(1/x)$ dynamics. We
discuss the ambiguities remaining in the gluon distribution. We present
improved predictions for $W$ boson (and $t$ quark) production at the FNAL $\pp$
collider.


title: $\epsilon_b$ Constraints on Self--Couplings of Vector Bosons

abstract:
  We analyze the constraints on possible anomalous contributions to the
$W^+W^-Z$ vertex coming from non-universal radiative corrections to the $Z
\rightarrow b \bar{b}$ width. We parametrize these corrections in terms of
$\epsilon_b$ and use the LEP data to establish the allowed values for the
anomalous triple couplings. We examine all CP conserving effective operators
that exhibit $SU(2)_L\times U(1)_Y$ gauge invariance and do not give any tree
level contribution to the present experimental observables. For some of these
operators our constraints are comparable with the bounds coming from a global
fit of the oblique parameters, which evidences the increasing relevance of the
precise measurement of the $b$--quark parameters at LEP for the search of new
physics.


title:
Anomalous quartic couplings in $ W^+W^- \gamma $ production at $e^+e^- $
  colliders

abstract:
  We study the process $e^+e^- \rightarrow W^+W^- \gamma$ at high-energy $e^+
e^-$ colliders to investigate the effect of genuine quartic
$W^+W^-\gamma\gamma$ and $W^+W^- Z\gamma$ anomalous couplings on the cross
section. Deviations from the Standard Model predictions are quantified. We show
how bounds on the anomalous couplings can be improved by choosing specific
initial state helicity combinations. The dependence of the anomalous
contributions on the collider energy is studied.


title: The Free Energy of Hot QED at Fifth Order

abstract:
  The order $e^5$ contribution to the pressure of massless quantum
electrodynamics at nonzero temperature is determined explicitly. An identity is
also obtained relating a gauge-invariant piece of the pressure at order
$e^{2n+3} \ (n \ge 1) $ (from diagrams with only one fermion loop) to the
pressure at order $e^{2n}$.