title:
Origin of spontaneous violation of the Lorentz symmetry: Vortices in the
  cosmos

abstract:
  By carefully studying the (1,0)+(0,1) representation space for massive
particles we point to the existence of certain inherent tachyonic dispersion
relations: E^2= p^2-m^2. We put forward an interpretation that exploits these
``negative mass squared'' solutions; rotational invariance is spontaneously
broken. Relevance of these results to the vortices in the cosmos is pointed
out.
  NOTE: Just as "negative energy solutions'' of Dirac equation are
re-interpreted as antiparticles, similarly the possibility exists for
re-interpreting the tachyonic dispersion relations of all (j,0)+(0,j)
representation spaces via spontaneous Lorentz symmetry breaking. In Mod. Phys.
Lett. A8:2623-2630,1993 we exhibited this explicitly for the j=1 representation
space. The interest in this old subject has grown markedly in recent years as
is evident from numerous theoretical and phenomenological works on the subject.
With this observation, we make this replacement of our paper fourteen years
after its initial publication. The Abstract and main text remain unaltered. The
title is changed to reflect the underlying physics more closely.


title: A Bargmann-Wightman-Wigner Type Quantum Field Theory

abstract:
  This version corrects an inportant typographical error in Eq. 17. COMMENTS,
FOR THE RECORD: A referees reoprt from Phys. Rev. Lett. read in part ``The
first named author has appreciated my exceptionally long report. He has read
and well assimilated the literature I suggested. Congratulations! This very new
version of the manuscript has now three authors and carries a very well chosen
title. Indeed Bargmann, Wightman and Wigner had studied, this subject forty
years ago, in an unpublished book (several chapters were distributed as
preprints). The authors explain well the scope of their paper. They have made a
thorough construction of a field theory of a non usual Wigner type; that is
completely new and all references are relevant. {\it This paper should be
published.}" Despite the fact that no other report was received, the editors of
Phys. Rev. Lett. rejected this paper.
  D.V.A.


title: Is the World Supersymmetric? Do We Already Know?

abstract:
  In addition to the very good theoretical motivations for supersymmetry, there
are now at least nine phenomenological indications that nature is
supersymmetric. All are indirect, so more is better. They are enumerated here.
Some discussion is also given of models, of when and where superpartners might
be directly detected, and of why the scale of supersymmetry cannot be pushed up
if superpartners and SUSY Higgs bosons are not directly detected.


title: Metastability in Two Dimensions and the Effective Potential

abstract:
  We study analytically and numerically the decay of a metastable phase in
(2+1)-dimensional classical scalar field theory coupled to a heat bath, which
is equivalent to two-dimensional Euclidean quantum field theory at zero
temperature. By a numerical simulation we obtain the nucleation barrier as a
function of the parameters of the potential, and compare it to the theoretical
prediction from the bounce (critical bubble) calculation. We find the
nucleation barrier to be accurately predicted by theory using the bounce
configuration obtained from the tree-level (``classical'') effective action.
Within the range of parameters probed, we found that using the bounce derived
from the one-loop effective action requires an unnaturally large prefactor to
match the lattice results. Deviations from the tree-level prediction are seen
in the regime where loop corrections would be expected to become important.


title: Nuclear Force in the Skyrme Model: Quasistatic Approach

abstract:
  Dynamics of two-Skyrmion systems is studied in the quasistatic approach. The
quasistatic approach enables us to formulate the collective coordinate
quantization of two-Skyrmion systems consistently with the 1/Nc expansion. By
constructing quasistatic field configurations for largely separated two
Skyrmions, their energies are computed for three independent relative
orientations of the Skyrmions in the isospin space. The obtained energies are
much lower than those for the product approximation. In particular, the
repulsion in the two-pion range is considerably reduced.


title: A Predictive Inflationary Scenario Without The Gauge Singlet

abstract:
  We propose a new realization of the chaotic inflationary scenario in which
the scalar field responsible for inflation also spontaneously breaks the
underlying gauge symmetry at a superheavy scale $\sim 10^{15} - 10^{17}\; GeV$.
A possible framework is provided by the superstring inspired gauge models, in
which case several predictions are essentially model independent. The spectral
index for the scalar perturbations $n \simeq 0.92 - 0.88$, while the ratio of
the tensor to the scalar quadrupole anisotropy is $(\Delta T/T)^2_T/(\Delta
T/T)^2_S \approx 0.4 - 0.7$. On smaller angular scales, $\delta T/T (1^\circ )
\approx (9 - 16) \times 10^{-6}$ and $\delta T/T (2.1^\circ ) \approx (6 - 10)
\times 10^{-6}$. Implications for magnetic monopoles and cosmic strings as well
as the gauge hierarchy problem are pointed out.


title: Identifying the Higgs Boson in Electron--Photon Collisions

abstract:
  We analyze the production and detection of the Higgs boson in the next
generation of linear $e^+e^-$ colliders operating in the $e\gamma$ mode. In
particular, we study the production mechanism $e + \gamma \rightarrow e \gamma
\gamma \rightarrow e + H$, where one photon is generated via the laser
backscattering mechanism, while the other is radiated via the usual
bremsstrahlung process. We show that this is the most important mechanism for
Higgs boson production in a $500$ GeV $e\gamma$ collider for
$M_H\raisebox{-.4ex}{\rlap{$\sim$}} \raisebox{.4ex}{$>$}140$ GeV. We also study
the signals and backgrounds for detection of the Higgs in the different decay
channels, $b \bar b$, $W^+W^-$, and $ZZ$, and suggest kinematical cuts to
improve the signature of an intermediate mass Higgs boson.


title: String-Based Perturbative Methods for Gauge Theories

abstract:
  Recent progress in the computation of one-loop gluon amplitudes is reviewed.
These methods were originally derived from superstring theory and are
significantly more efficient than conventional Feynman rules. With these
methods, explicit computations can be performed beyond those achieved by
traditional methods.


title: Bounding the Photon Mass with Solar Probes

abstract:
  Proposed close-encounter solar probes (Vulcan and Solar Probe) are planned to
have highly eccentric orbits, with a perihelion of about $4R_S$ and an
inclination close to $90^\circ$ out of the plane of the ecliptic. We show this
could allow at least an order-of-magnitude improvement in the present directly
measured limit on the photon mass.


title: Decay-Time Asymmetries at the B-Factories

abstract:
  Absract (Invited talk at the X DAE High Energy Physics symposium in December
1992, held at Tata Institute of Fundamental Research, Bombay)


title:
Selected Topics on Rare Kaon Processes - in the Standard Model and
  Supergravity -

abstract:
  Rare kaon processes appear to be particularly suitable to study the
extensions of the standard model, especially if the possibility for eventual
direct evidence becomes unlikely. In this review, we discuss processes that are
important as a test of either the standard model or supergravity. Moreover,
some of these are important even for both the standard model and for
supergravity. Particular attention is paid to the reduction of uncertainties in
the calculation, especially the ones coming from the confinement effects.
Recent approaches, such as chiral perturbation theory, the large
$N_c$-expansion, QCD sum rules and lattice QCD, are discussed. This is found to
be the best strategy in view of the fact that supersymmetric effects are rather
tiny.


title: QCD Sum Rules: The Second Decade

abstract:
  Invited Talk at the Conference "QCD -- 20 Years Later", June 9 - 13, 1992,
Aachen, Germany


title: Resummation Methods at Finite Temperature: The Tadpole Way

abstract:
  We examine several resummation methods for computing higher order corrections
to the finite temperature effective potential, in the context of a scalar
$\phi^4$ theory. We show by explicit calculation to four loops that dressing
the propagator, not the vertex, of the one-loop tadpole correctly counts
``daisy'' and ``super-daisy'' diagrams.


title: Model Independent Higgs Boson Mass Limits at LEP

abstract:
  We derive model-independent constraints on Higgs mass and couplings from
associated signals for higher masses, accessible at LEP2. This work is
motivated by the fact that, in many extensions of the standard model, the Higgs
boson can have substantial "invisible" decay modes, for example, into light or
massless weakly interacting Goldstone bosons associated to the spontaneous
violation of lepton number below the weak scale.


title: Electroweak bubbles and sphalerons

abstract:
  We consider non-perturbative solutions of the Weinberg-Salam model at finite
temperature. We employ an effective temperature-dependent potential yielding a
first order phase transition. In the region of the phase transition, there
exist two kinds of static, spherically symmetric solutions: sphalerons and
bubbles. We analyze these solutions as functions of temperature. We consider
the most general spherically symmetric fluctuations about the two solutions and
construct the discrete modes in the region of the phase transition. Sphalerons
and bubbles both possess a single unstable mode. We present simple
approximation formulae for these levels.


title:
The $\Delta S=1$ Effective Hamiltonian Including Next-to-Leading Order
  QCD and QED Corrections

abstract:
  In this paper we present a calculation of the $\Delta S=1$ effective weak
Hamiltonian including next-to-leading order QCD and QED corrections. At a scale
$\mu$ of the order of few GeV, the Wilson coefficients of the operators are
given in terms of the renormalization group evolution matrix and of the
coefficients computed at a large scale $\sim M_W$. The expression of the
evolution matrix is derived from the two-loop anomalous dimension matrix which
governs the mixing of the relevant current-current and penguin operators,
renormalized in some given regularization scheme. We have computed the
anomalous dimension matrix up to and including order $\alphas^2$ and $\alphae
\alphas$ in two different renormalization schemes, NDR and HV, with consistent
results. We give many details on the calculation of the anomalous dimension
matrix at two loops, on the determination of the Wilson coefficients at the
scale $M_W$ and of their evolution from $M_W$ to $\mu$. We also discuss the
dependence of the Wilson coefficients/operators on the regularization scheme.


title: Quarkonium Decays and Light Quark Masses

abstract:
  The $SU(3)$-violating decays $\Phi^{2S} \goto \Phi^{1S} X$, where $X = \pi^0$
or $\eta$ and $\Phi = J/\psi$ or $\Upsilon$ have been recently proposed as a
means of probing the light quark masses beyond leading order in chiral
perturbation theory. We argue that this analysis is incorrect, even in the
heavy quark limit. We show that these decays are governed by an infinite number
of matrix elements which are not suppressed by any small parameter, and which
cannot be computed with our present understanding of QCD. Furthermore, for
sufficiently heavy quarks, we show that the decay amplitudes can be organized
into a twist expansion, and that the contributions considered in the above
proposal are subleading in this expansion. We also explain how these decays
nonetheless give a constraint on the light quark masses valid at {\it leading
order} in the chiral expansion. The decays $\Phi^{1S} \goto \eta\gamma$ and
$\Phi^{2S} \goto \Phi^{1S} \pi\pi$ also have contributions from infinitely many
operators, contrary to claims in the literature.


title: Parke-Taylor amplitudes in the multi-Regge kinematics

abstract:
  The Parke-Taylor multigluon amplitudes are examined in the multi-Regge
kinematics, which assumes strong rapidity ordering of the produced gluons, and
are used to compute the $n$-gluon production cross section and the gluon-gluon
total cross section.


title:
Is Geodetic Precession of Massive Neutrinos the solution to the Solar
  Neutrino Problem?

abstract:
  We examine a recent suggestion by Milburn that slightly massive electron
neutrinos, produced left-handed at the core of the sun, suffer geodetic
precession adequate to render them right-handed (and therefore sterile) in
sufficient numbers to solve the solar neutrino problem. In that light, we
perform a complete, general-relativistic calculation of the geodetic spin
precession of an ultrarelativistic particle in the Schwartzschild metric. We
conclude that the effect is negligible, in disagreement with Milburn's
analysis.


title:
Valley Method Versus Instanton-Induced Effective Lagrangean Up to
  $(E/E_{\rm sphaleron})^{8/3}$

abstract:
  We compare the two most popular approaches to the problem of
instanton-antiinstanton interaction at high energies - the valley method and
the effective-Lagrangian approach - and use them to calculate the
next-to-next-to-leading term in the expansion of ``holy grail'' function
determining the cross section with baryon number violation in the Standard
Model.


title: Constituent Quark Couplings and QCD in the Large $N_c$ Limit

abstract:
  It is shown that in the constituent quark model of Georgi-Manohar, the
dispersion relation that leads to the Adler-Weisberger sum rule for the axial
vector coupling $g_A$ requires a subtraction constant. This fact explains the
discrepancy between the results of different recent estimates of the $1/N_c$
corrections to Weinberg's large $N_c$ result $g_A=1$, where $N_c$ is the number
of QCD colors. We also discuss a possible scenario which shows that $g_A=1$
might not be a necessary consequence of QCD in the large $N_c$ limit.


title: Constraints on Anomalous Gauge Boson Couplings From $b \to s\gamma$

abstract:
  The recent results of the CLEO Collaboration on both inclusive and exclusive
radiative $B$ decays are combined with those of the UA2 Collaboration on
$W\gamma$ production to highly constrain the anomalous trilinear gauge
couplings of the $W$. The theoretical analysis of the $b \to s\gamma$ process
employs, next-to-leading order operator coefficient evolution as well as QCD
bremsstrahlung and appropriate phase space corrections.


title:
Hadronic contribution to the photon vacuum polarization: a theoretical
  estimate

abstract:
  A simple model for the hadronic contribution to the photon vacuum
polarization function $\Pi_{had}(q^2)$, for spacelike momenta, is presented.
For small momenta, the two loop contribution from the pseudoscalar meson octet
is computed from the chiral Lagrangian. The light quark contribution (which at
low momentum gives the ${\cal O}(q^6)$ counterterm in the chiral Lagrangian) is
calculated within a relativistic constituent quark model incorporating the
momentum dependence of the quark mass. The perturbative gluons of QCD are
included in a standard fashion. The total result is close to an estimate of
$\Pi_{had}(q^2)$ that is obtained directly from $e^+e^-\to hadrons$ data. We
further use our results for $\Pi_{had}(q^2)$ to calculate the ${\cal O}(e^4)$
hadronic contribution to lepton magnetic moments and to calculate
$\alpha_{QED}(M_Z^2)$. A simpler model of constituent quarks with momentum
independent masses gives less favourable results.


title: Chiral Dynamics and Heavy Quark Symmetry in a Toy Field Theoretic Model

abstract:
  We study a solvable QCD--like toy theory, a generalization of the
Nambu--Jona-Lasinio model, which implements chiral symmetries of light quarks
and heavy quark symmetry. The chiral symmetric and chiral broken phases can be
dynamically tuned. This implies a parity doubled heavy--light meson system,
corresponding to a $(0^-,1^-)$ multiplet and a $(0^+,1^+)$ heavy spin
multiplet. Consequently the mass difference of the two multiplets is given by a
Goldberger--Treiman relation and $g_A$ is found to be small. The Isgur--Wise
function, $\xi(w)$, the decay constant, $f_B$, and other observables are
studied.


title:
Unconventional superstring derived E$_{\bf 6}$ models and neutrino
  phenomenology

abstract:
  Conventional superstring derived E$_6$ models can accommodate small neutrino
masses if a discrete symmetry is imposed which forbids tree level Dirac
neutrino masses but allows for radiative mass generation. Since the only
possible symmetries of this kind are known to be generation dependent, we
explore the possibility that the three sets of light states in each generation
do not have the same assignments with respect to the 27 of $E_6$, leading to
non universal gauge interactions under the additional $U(1)'$ factors for the
known fermions. We argue that models realising such a scenario are viable, with
their structure being constrained mainly by the requirement of the absence of
flavor changing neutral currents in the Higgs sector. Moreover, in contrast to
the standard case, rank 6 models are not disfavoured with respect to rank 5. By
requiring the number of light neutral states to be minimal, these models have
an almost unique pattern of neutrino masses and mixings. We construct a model
based on the unconventional assignment scenario in which (with a natural choice
of the parameters) $m_{\nut}\sim O(10)$eV is generated at one loop, $m_{\num}$
is generated at two loops and lies in a range interesting for the solar
neutrino problem, and $\nue$ remains massless. In addition, since baryon and
lepton number are conserved, there is no proton decay in the model. To
illustrate the non-standard phenomenology implied by our scheme we also discuss
a second scenario in which an attempt for solving the solar neutrino puzzle
with matter enhanced oscillations and practically massless neutrinos can be
formulated, and in which peculiar effects for the $\num$ --> $\nut$ conversion
of the upward-going atmospheric neutrinos could arise as well.


title:
Spontaneous CP Violation and Baryogenesis in the Minimal Supersymmetric
  Standard Model

abstract:
  We investigate the effects of the spontaneous CP violation at finite
temperature in the Minimal Supersymmetric Standard Model on the baryogenesis at
the weak scale. After a brief discussion of the case in which the electroweak
phase transition is of the second order, we study in details the baryogenesis
scenario when the transition proceeds via bubble nucleation. We show that the
space-time dependent phase for the Higgs vacuum expectation values coming from
the spontaneous CP violation can give rise to a efficient generation of baryon
number inside the bubble walls if the superpotential parameters and the soft
supersymmetry breaking ones are complex. However we find that in order to get
the observed value for the baryon asymmetry of the universe the phases of such
parameters can be as small as $10^{-5}$, giving rise to an electron dipole
moment of the neutron well below the current experimental limit. Moreover a
light Higgs pseudoscalar is needed, and an upper bound on its mass is obtained.


title:
A QCD Relation Between Hyperfine Splittings in Isospin doublets - A
  Light Quark Symmetry?

abstract:
  Recent data on the $D^*$ masses confirm the QCD prediction based on the
\REF{\ICHJL}{Isaac Cohen and Harry J. Lipkin, \plb{84}{323}{1979}} very general
assumption $\({\ICHJL}\)$ that the spin-dependence of the quark couplings to
photons and gluons have the same structure and differ only in the value of the
coupling constants, This prediction with no free parameters and using the $\Xi$
and $\Xi^*$ masses as input follows from noting that the charmed antiquark
$\bar c$ and the strange diquark (ss) have exactly the same couplings to both
the photon (Q=-2/3) and to the gluon (both are color antitriplets). New
predictions are obtained with this approach. Corrections to the naive model are
investigated and shown to be small.


title: Custodial SU(2) Violation and the Origin of Fermion Masses

abstract:
  Custodial $SU(2)$ breaking due to dynamical fermion masses is studied in a
rather general context and it is shown how some well known limiting cases are
correctly described. The type of ``gap equation'' which can systematically lead
to extra negative contributions to the so--called $\rho$--parameter is
emphasized. Furthermore general model independent features are discussed and it
is shown how electro--weak precision measurements can be sensitive to the
fermion content and/or dynamical features of a given theory.


title: Electromagnetic Production of Quarkonium in $Z^{0}$ decay

abstract:
  The decay $Z^{0}\rightarrow Q+ \ell^{+}\ell^{-}$, where $Q$ is a
$J^{PC}=1^{--}$ quarkonium state, has a very clean final state, which should
make it easy to detect. The branching ratio of this mode is greater than
$10^{-6}$ for $\rho$, $\phi$, and $\psi$, indicating that these processes may
be detectable at LEP.


title: Overview of Accelerator Long Baseline Neutrino Oscillation Experiments

abstract:
  There is renewed interest in performing a long baseline neutrino oscillation
experiment using accelerator neutrinos because of a discrepancy between the
measured and the predicted values of the ratio of electron to muon neutrinos
produced in the upper atmosphere by cosmic rays.The approximate range in
oscillation parameter space indicated by the Kamiokande atmospheric neutrino
results and confirmed by IMB is bounded by $ 10^{-3}~ eV^2 < \dmsq < 10^{-1}~
eV^2 $ and $\s2t > 0.4~$. To reach such small $\dmsq$, using an accelerator as
the source of neutrinos where the energy is typically 1 GeV or greater,
requires baselines in the range of 10~km to 1000~km. In this talk I will give
an overview of the most likely possibilities for such a long baseline
accelerator neutrino oscillation experiment.


title: Dynamics of Phase Transitions Induced by a Heat Bath

abstract:
  We study the non-equilibrium dynamics of a symmetry restoring phase
transition in a scalar field theory, the ``system'', linearly coupled to
another scalar field taken as a ``heat bath''. The ``system'' is initially in
an ordered low temperature phase, and the heat bath is at a temperature close
to the critical temperature for the system. We estimate the time at which the
phase transition to the disordered (symmetric) phase takes place. We derive,
and integrate the one-loop effective equations of motion for the order
parameter that include the effects of the heat bath. A semiclassical Langevin
equation is derived and it is found that it contains a non-dissipative,
non-Markovian kernel, the noise term is colored and correlated on time scales
determined by the temperature of the heat bath. The range of validity of the
Langevin equation and a consistent procedure to incorporate corrections are
discussed.


title: Chemical equilibrium in QCD gas in the early universe

abstract:
  We compute the thermally averaged $\qq$--annihilation rate into two and three
gluons in the early universe. We show that at very high temperatures $\qq\to
ggg$ represents only a 3\%\ correction to $\qq\to gg$. Comparing the
annihilation rate to the Hubble rate, corrected for particle interactions in
the Standard Model gas, we find that quarks and gluons are not in chemical
equilibrium when $T\gsim 3\times 10^{14}$ GeV.


title:
Consistency and lattice renormalization of the effective theory for
  heavy quarks

abstract:
  The effective theory describing infinite mass particles with a given
velocity, has a great interest in heavy flavor physics. It has the unpleasant
characteristic that the energy spectrum is unbounded from below; this fact is
the source of the problems in the formulation of the euclidean theory. In this
paper we present an analysis of the euclidean effective theory, that is rather
complete and has positive conclusions. A proof of the consistency of the
euclidean theory is presented and a technique for the evaluation of the
amplitudes in perturbation theory is described. We compute also the one-loop
renormalization constants of the lattice effective theory and of the
heavy-heavy current that is needed for the determination of the Isgur-Wise
function. A variety of effects related to the explicit breaking of the Lorentz
symmetry of lattice regularization is demonstrated. The most peculiar
phenomenon is that the heavy quark velocity receives a finite renormalization.
Finally, we compute the lattice-continuum renormalization constant of the
Isgur-Wise current. It is needed for the conversion of the values of the matrix
elements computed with the lattice effective theory, to the values in the full
theory.


title: Chiral Corrections to the S-Wave Pion-Nucleon Scattering Lengths

abstract:
  We calculate the chiral corrections to Weinberg's prediction for the S--wave
$\pi N$ scattering lengths up--to--and--including order ${\cal O}(M_\pi^3)$
making use of heavy baryon chiral perturbation theory. For the isospin--odd
scattering length $a^-$ these corrections are small and bring the prediction
closer to the empirical value. In the case of the isospin--even $a^+$ large
cancellations appear so that the ${\cal O}(M_\pi^3)$ result depends sensitively
on certain resonance parameters which enter the calculation of the contact
terms present at next--to--leading order.


title: Diffraction and the Gluon Mass

abstract:
  We recently proposed a QCD-Pomeron described by the exchange of two
non-perturbative gluons characterized by a dynamically generated gluon mass. It
is here shown that data on elastic scattering, exclusive $\rho$ production in
deep inelastic scattering and the $J/\Psi$-nucleon total cross-section can be
successfully described in terms of a single gluon mass $m_g\simeq0.37$~GeV. We
observe that the total cross sections of hadrons with small radii, such as
$J/\Psi$, have a marked dependence on the effective gluon mass.


title: Probing supergravity models with the $b\to s\gamma$ microscope

abstract:
  We present a calculation of the branching ratio $\brbsg$ in two well
motivated supersymmetric models: the minimal $SU(5)$ and the no-scale flipped
$SU(5)$ supergravity models. We find that the improved CLEO upper bound
($\brbsg<5.4\times10^{-4}$ at 95\% CL) does not yet constrain the minimal
$SU(5)$ supergravity model, where $\brbsg_{minimal}=(2.3-3.6)\times10^{-4}$. In
the flipped $SU(5)$ model the CLEO bound is constraining, although still not
very significantly, even for light charged Higgs masses. An improvement in
sensitivity by a factor of two will probe all (more than half) of the parameter
space of the minimal (flipped) $SU(5)$ supergravity model. This ``resolution"
of the $\bsg$ microscope far surpasses that of present collider experiments. In
the flipped model there exists a significant region of parameter space where
$\brbsg$ is highly suppressed due to a new phenomenon involving a complicated
cancellation against the QCD correction parameter.


title: The vacuum structure in a supersymmetric gauged Nambu-Jona-Lasinio model

abstract:
  The dynamical breakdown of the $SU(2) \times U(1)$ symmetry triggered by a
top-antitop condensate is studied in a supersymmetric version of the gauged
Nambu-Jona-Lasinio model. An effective potential approach is used to
investigate the vacuum structure and the equivalence with the minimal
supersymmetric standard model. The role of the soft supersymmetry breaking
terms is analyzed in detail in a version of the model where the electroweak
gauge interactions are turned off.


title: Supersymmetric Corrctions to Masses and Widths

abstract:
  Supersymmetric radiative corrections to the partial width $\Gamma (\tau
\rightarrow e \nu \bar{\nu})$ and the masses of the $W$ and $Z$ gauge bosons
are calculated in different renormalization schemes. The importance of the
non-universal contributions is analyzed.


title:
Hadronic Transitions among Quarkonium States in a
  Soft-Exchange-Approximation. Chiral Breaking and Spin Symmetry Breaking
  Processes

abstract:
  Although no asymptotic heavy quark spin symmetry, and even more no flavor
symmetry, are expected for systems such as quarkonium, a numerical discussion
shows that for some processes and in a preasymptotic region which may roughly
include charmonium and bottomonium, the use of the spin-symmetry may be useful
in conjunction with chiral symmetry for light hadrons (soft-exchange-
approximation regime, SEA). We continue our discussion of hadronic transitions
in the SEA-regime by studying in particular chiral breaking transitions such as
$~^3P' \to ~^3P\pi^0$, $~^3P\eta$, level splittings and transitions which break
both chiral and spin symmetry, such as $\psi ' \to J/\psi \pi^0$, $J/\psi
\eta$, and $~^1P_1 \to J/\psi \pi^0$.


title:
Non-Standard Gauge-Boson Self-Interactions within a Gauge Invariant
  Model

abstract:
  We examine dimension-six extensions of the standard electroweak Lagrangian
which are invariant under local \suu -transformations. The dimension-four
trilinear and quadrilinear effective interactions of the vector bosons with one
another are found to coincide with the vector boson interactions previously
derived from global SU(2) weak isospin symmetry broken by electromagnetism.
Supplementing the model by a well-known dimension-six single-parameter
quadrupole interaction leads to the most general vector boson self-couplings
that can be obtained by addition of dimension-six terms to the standard
Lagrangian. We examine in some detail another SU(2)xU(1)-symmetric interaction
which contains W_3-B mixing and modifies both vector boson self-couplings and
fermionic interactions. Independently of being strongly constrained by the LEP
1 data, the addition of this interaction to the above-mentioned non-standard
ones does not change the form of the trilinear and quadrilinear non-standard
self-couplings of the vector bosons. Therefore, while being interesting in
itself with respect to LEP~1 physics, this term is irrelevant with respect to
the phenomenology of the vector-boson self-interactions.


title:
The Effects of the Massless O(alpha_s^2), O(\alpha\alpha_s), O(\alpha^2)
  QCD and QED Corrections and of the Massive Contributions to
  Gamma(H^0\rightarrow b\overline{b})

abstract:
  We consider in detail various theoretical uncertainties of the perturbative
predictions for the decay width of $H^0\rightarrow b\overline{b}$ process in
the region $50\ GeV< M_H\leq 2M_W$. We calculate the order
$O(\alpha_s^2)$-contributions to the expression for $\Gamma_{Hb\overline{b}}$
through the pole quark mass and demonstrate that they are important for the
elimination of the numerical difference between the corresponding expression
and the one through the running $b$-quark mass. The order $O(\alpha\alpha_s)$
and $O(\alpha^2)$ massless and order $O(m_b^2/M_H^2)$ massive corrections to
$\Gamma_{Hb\overline{b}}$ are also calculated. The importance of the latter
contributions for modeling of the threshold effects is demonstrated. The
troubles with identifying of the 4 recent L3 events $e^+e^-\rightarrow
l^+l^-\gamma\gamma$ with the decay of a Standard Higgs boson are discussed.


title:
Asymptotic behaviour of the total cross section of p-p scattering and
  the Akeno cosmic ray data

abstract:
  I present a new determination of the total cross section for proton-proton
collisions from the recent Akeno results on absorption of the cosmic ray
protons in the p-Air collisions. Extrapolation to the SSC energy suggests
$\sigma_{tot}(p-p) \approx (160-170) mb$. I also comment on a possible
sensitivity of the p-Air cross section determinations to assumptions on the
inelasticity of nuclear collisions at high energy.


title:
On Daisy and Superdaisy Resummation of the Effective Potential at Finite
  Temperature

abstract:
  We describe in detail, in the context of the simple scalar $\phi^4$ theory,
the prescription for resummation of daisy and superdaisy diagrams in the
effective potential using the solution of the gap equations in the infrared
limit. We find that the latter procedure is consistent provided we neglect
logarithmic terms from the finite-temperature self energies and from the
integration of overlapping momenta. This amounts to dressing only the zero-mode
contribution to the finite-temperature effective potential. Improving also the
non-zero modes, would require exactly solving (not in the IR limit) the gap
equations. In general this can only be done in a theory where all self-energies
are momentum independent ({\em e.g.} in the scalar theory at the symmetric
phase $\phi=0$). However some partial dressing procedures are still possible in
general.


title: Oblique electroweak corrections and triple vector boson couplings

abstract:
  We relate all $C$-- and $P$--invariant anomalous triple vector--boson
couplings to the oblique electroweak parameters. LEP constraints on the latter
then yield the strongest and most general simultaneous bounds to date on the
former. Even if the oblique parameters assume their Standard Model values
precisely, these bounds would not shrink to zero---thus underscoring the need
for direct experimental probes at future colliders.


abstract:
  Cabibbo-allowed nonleptonic weak decays of charmed baryons
$\lamc,~\xin,~\xip$ and $\Omega_c^0$ into an octet baryon and a pseudoscalar
meson are analyzed. The nonfactorizable contributions are evaluated under pole
approximation, and it turns out that the $s$-wave amplitudes are dominated by
the low-lying $\halfm$ resonances, while $p$-wave ones governed by the
ground-state $\halfp$ poles. The MIT bag model is employed to calculate the
coupling constants, form factors and baryon matrix elements. Our conclusions
are: (i) $s$ waves are no longer dominated by commutator terms; the
current-algebra method is certainly not applicable to parity-violating
amplitudes, (ii) nonfactorizable $W$ exchange effects are generally important;
they can be comparable to and somtimes even dominate over factorizable
contributions, depending on the decay modes under consideration, (iii)
large-$N_c$ approximation for factorizable amplitudes also works in the heavy
baryon sector and it accounts for the color nonsuppression of $\lamc\ri
p\bar{K}^0$ relative to $\lamc\ri\Lambda\pi^+$, (iv) a measurement of the decay
rate and the sign of the $\alpha$ asymmetry parameter of certain proposed decay
modes will help discern various models; especially the sign of $\alpha$ in
$\lamc\ri\Sigma\pi$ decays can be used to unambiguously differentiate recent
theoretical schemes from current algebra, and (v) $p$ waves are the dominant
contributions to the decays $\lamc\ri\Xi^0 K^+$ and $\xin\ri\Sigma^+ K^-$, but
they are subject to a large cancellation; this renders present theoretical
predictions on these two channels unreliable.


title: Spectral Densities and Borel Transforms in Compton Scattering

abstract:
  We show that the leading double spectral density in sum rules for
Compton-like processes can be obtained by simple properties of the Borel
transform, extending an approach widely used in the literature on sum rules,
and known to be valid only for the spectral densities of form factors. The
extension is illustrated in the scalar case, where it is shown to be consistent
with Cutkosky rules. Using arguments based on the analiticity properties of the
vertex and the box diagrams, we show that Compton scattering is, however, a
favourable case and indeed possible disagreements between the two methods are
likely to be encountered in more general situations.


title: A Model of Universality Violation Revisited

abstract:
  The possibility that the interactions of the third generation of quarks and
leptons may violate universality by a small amount remains an open experimental
question. The model of Li and Ma, which naturally accommodates such violations,
is found to be highly constrained by newly obtained, high precision electroweak
and $\tau$-lepton data once full Standard Model radiative corrections are
incorporated into the analysis. A comparison of the predictions of this model
with existing data and the expectations for future colliders is presented.


title:
On the Determination of the Gluon Density of the Proton from
  Heavy-Flavour Production at HERA

abstract:
  Using a recent next-to-leading-order calculation of the photoproduction
double differential cross section for heavy quarks, we study the possibility of
extracting the gluon density of the proton from heavy-quark photoproduction
data. We discuss the theoretical uncertainties connected with this method, and
we conclude that they are well under control in a wide $x$ domain.


title:
Detecting an Intermediate Mass Charged Higgs at $\gamma \gamma$
  Colliders

abstract:
  The detection of an intermediate mass charged Higgs boson at $\gamgam$
colliders via the modes $\gamgam \to H^+ H^- \to \nu \tau^+ \bar{\nu} \tau^-,~
c \bar{s} \bar{c} s,~$ and $ \nu \tau^+ \bar{c}s + c \bar{s} \bar{\nu} \tau^-$
is considered. $W^+ W^-$ boson pair production is the dominant background for
these modes. The three modes may be used in a complementary fashion to detect a
charged Higgs boson. The mixed leptonic-hadronic mode may be used to determine
the charged Higgs mass by reconstructing the invariant hadronic mass. The
sensitivity of Br$(H^+ \rightarrow c\bar s,\,\nu \tau^+)$ on the discovery
limit of the charged Higgs boson is also discussed.


title: $SU(3)$ vs. $SU(3) \times SU(3)$ Breaking in Weak Hyperon Decays

abstract:
  We consider the predictions of chiral perturbation theory for $SU(3)$
breaking in weak semileptonic and $s$-wave nonleptonic hyperon decays. By
defining an expansion sensitive only to $SU(3)$ breaking, we show that the
leading corrections give rise to moderate corrections to $SU(3)$ relations
($\lsim 20\%$), even though the {\it chiral} symmetry $SU(3) \times SU(3)$
appears to be rather badly broken. This explains why $SU(3)$ fits to weak
hyperon decays work well even though chiral-symmetry breaking corrections are
large. Applying these $SU(3)$-breaking corrections to the analysis of the EMC
data, we find that the predicted value of $\bra p\mybar s\gamma_\mu\gamma_5
s\ket p$ is reduced by $\simeq 35\%$, suggesting that the ``EMC effect'' may be
less striking than commonly thought.


title:
$N_c$-counting rules and the axial vector coupling constant of the
  constituent quark

abstract:
  Instead of using a simple reggeon-exchange model, we provide a
model-independent estimate of high-energy contribution to the Adler-Weisberger
sum-rule. Results and conclusions of the paper remain unchanged.


title: Phenomenology of a Non-Standard Higgs

abstract:
  The one-Higgs-doublet standard model is necessarily incomplete because of the
triviality of the scalar symmetry-breaking sector. If the Higgs mass is
approximately 600 GeV or higher, there must be additional dynamics at a scale
$\Lambda$ which is less than a few TeV. In this case the properties of the
Higgs resonance can differ substantially from those predicted by the standard
model. In this letter we construct an effective Lagrangian description of a
theory with a non-standard Higgs boson and analyze the features of a theory
with such a resonance coupled to the Goldstone Bosons of the breaking of $\su$.
This Lagrangian describes the most general theory in which the Higgs and the
Goldstone Bosons are the only particles with a mass small compared to
$\Lambda$. We compute the leading corrections to the decay width of the Higgs
boson and the contribution to the Peskin-Takeuchi parameter $S$ and present
results for the corrections to Goldstone Boson scattering. We find that the
most prominent effects are due to one new parameter, which is directly related
to the Higgs boson width.


title: SSC Phenomenology of the 331 Model of Flavor

abstract:
  The 331 model offers an explanation of flavor by anomaly cancellation between
three families. It predicts three exotic quarks, $Q=D$, $S$, $T$, and five
extra gauge bosons comprising an additional neutral $Z_2$ and four charged
dileptonic gauge bosons $(Y^{--},Y^-)$, $(Y^{++},Y^+)$. Production of
$Q\overline{Q}$, $QY$, $YY$ and $Z_2$ at the SSC is calculated, and signatures
are discussed.


title:
Phenomenological Implications of the $m_t$ RGE Fixed Point for SUSY
  Higgs Boson Searches

abstract:
  In minimal SUSY-GUT models with $M_{SUSY}\ltap 1$ TeV, the renormalization
group equations have a solution dominated by the infrared fixed point of the
top Yukawa coupling. This fixed point predicts $m_t=(200\; {\rm GeV})\sin \beta
$; combined with the LEP results it excludes $m_t\ltap 130$ GeV. For $m_t$ in
the range 130-160 GeV, we discuss the sensitivity of the $m_t$ fixed point
result to GUT threshold corrections and point out the implications for Higgs
boson searches. The lightest scalar $h$ has mass 60-85 GeV and will be
detectable at LEPII. At SSC/LHC, each of the five scalars $h$, $H$, $A$,
$H^{\pm }$ may be detectable, but not all of them together; in one parameter
region none will be detectable.


title: Parton-Parton Elastic Scattering and Rapidity Gaps at Very High Energies

abstract:
  The theory of the perturbative pomeron, due to Lipatov and collaborators, is
used to compute the probability of observing parton-parton elastic scattering
and rapidity gaps between jets in hadron collisions at very high energies.


title: High Energy Quark-Antiquark Elastic scattering with Mesonic Exchange

abstract:
  We studies the high energy elastic scattering of quark anti-quark with an
exchange of a mesonic state in the $t$ channel with $-t/\Lambda^{2} \gg 1$.
Both the normalization factor and the Regge trajectory can be calculated in
PQCD in cases of fixed (non-running) and running coupling constant. The
dependence of the Regge trajectory on the coupling constant is highly
non-linear and the trajectory is of order of $0.2$ in the interesting physical
range.


title:
Precision Electroweak Tests of the Minimal and Flipped SU(5)
  Supergravity Models

abstract:
  We explore the one-loop electroweak radiative corrections in the minimal
$SU(5)$ and the no-scale flipped $SU(5)$ supergravity models via explicit
calculation of vacuum polarization contributions to the $\epsilon_{1,2,3}$
parameters. Experimentally, $\epsilon_{1,2,3}$ are obtained from a global fit
to the LEP observables, and $M_W/M_Z$ measurements. We include $q^2$-dependent
effects which have been neglected in most previous ``model-independent"
analyses of this type. These effects induce a large systematic negative shift
on $\epsilon_{1,2,3}$ for light chargino masses ($m_{\chi^\pm_1}\lsim70\GeV$).
In agreement with previous general arguments, we find that for increasingly
large sparticle masses, the heavy sector of both models rapidly decouples, \ie,
the values for $\epsilon_{1,2,3}$ quickly asymptote to the Standard Model
values with a {\it light} Higgs ($m_{H_{SM}}\sim100\GeV$). Specifically, at
present the $90\%$ CL upper limit on the top-quark mass is $m_t\lsim175\GeV$ in
the no-scale flipped $SU(5)$ supergravity model. These bounds can be
strengthened for increasing chargino masses in the $50-100\GeV$ interval. In
particular, for $m_t\gsim160\GeV$, the Tevatron may be able to probe through
gluino($\tilde g$) and squark($\tilde q$) production up to $m_{\tilde g}\approx
m_{\tilde q}\approx250\GeV$, exploring at least half of the parameter space in
this model.


title: Flavor Symmetries and The Problem of Squark Degeneracy

abstract:
  If supersymmetry exists at low energies, it is necessary to understand why
the squark spectrum exhibits sufficient degeneracy to suppress flavor changing
neutral currents. In this note, we point out that gauged horizontal symmetries
can yield realistic quark mass matrices, while at the same time giving just
barely enough squark degeneracy to account for neutral $K$-meson phenomenology.
This approach suggests likely patterns for squark masses, and indicates that
there could be significant supersymmetric contributions to $B-\bar{B}$ and
$D-\bar{D}$ mixing and CP violation in the $K$ and $B$ systems.


title:
The Motion of Massive Test Particles in the Dark Matter with an
  $a_0/r^2$ Energy Density

abstract:
  The motion of massive test particles in dark matter is studied. It is shown
that if the energy density of the dark matter making up a galactic halo has a
large $r$ behavior of $1/r^2$, then contrary to intuition the motion of these
test particles are not govern by Newtonian gravity, but rather by the equations
of geodesic motion from Einstein's theory of general relativity.
  Moreover, the rotational velocity curves of orbiting massive test particles
in this energy density do not approach a constant value at large $r$ but will
instead always increase with the radius of the orbit $r_c$.


title: Decorated-box-diagram-contributions to Bhabha scattering. (II)

abstract:
  We evaluate, in the high-energy limit, $s\gg|t|\gg m^2\gg\lambda^2$, the sum
of amplitudes corresponding to a class of Feynman diagrams describing two-loop
virtual photonic corrections to Bhabha scattering. The diagrams considered are
box and crossed box diagrams with a vacuum polarization insertion in one of the
photon lines.


title: Effective Lagrangian for Heavy and Light Mesons: Radiative B Decays

abstract:
  We make use of the information obtained from semileptonic decays of $B$ and
$D$ mesons, within an effective lagrangian description based on heavy quark
theory and on chiral expansion, to study the radiative decays $B \to K^\star
\gamma$ and $B_S \to \phi\gamma$, and the pair conversion processes $B \to K
e^+e^-$ and $B \to K^\star e^+e^-$. We discuss with care the required
extrapolations from zero recoils. We obtain a BR($B\to K^\star\gamma$) between
$1.3\times 10^{-5}$ and $4.1\times 10^{-5}$ and BR($B_s \to\phi\gamma$) between
$1.4\times 10^{-5}$ and $4.5\times 10^{-5}$, with errors mainly arising from
the present uncertainty in the Kobayashi-Maskawa element $|V_{ts}|$. For the
pair conversion processes we study in particular the lepton effective mass
distributions whose measurements would allow for an understanding both long
distance and short distance contributions to such processes.


title:
Two-loop two-point functions with masses: asymptotic expansions and
  Taylor series, in any dimension

abstract:
  In all mass cases needed for quark and gluon self-energies, the two-loop
master diagram is expanded at large and small $q^2$, in $d$ dimensions, using
identities derived from integration by parts. Expansions are given, in terms of
hypergeometric series, for all gluon diagrams and for all but one of the quark
diagrams; expansions of the latter are obtained from differential equations.
Pad\'{e} approximants to truncations of the expansions are shown to be of great
utility. As an application, we obtain the two-loop photon self-energy, for all
$d$, and achieve highly accelerated convergence of its expansions in powers of
$q^2/m^2$ or $m^2/q^2$, for $d=4$.


title: Momentum Distributions in $t\bar t$

abstract:
  We apply the Green function formalism for $t-\bar t$ production and decay
near threshold in a study of the effects due to the momentum dependent width
for such a system. We point out that these effects are likely to be much
smaller than expected from the reduction of the available phase space. The
Lippmann--Schwinger equation for the QCD chromostatic potential is solved
numerically for $S$ partial wave. We compare the results on the total cross
section, top quark intrinsic momentum distributions and on the energy spectra
of $W$ bosons from top quark decays with those obtained for the constant width.


title: Extra symmetries in the effective theory of heavy quarks

abstract:
  Extra symmetries are shown to exist in the effective theory of heavy quarks
when both quarks and anti-quarks with the same velocity are included. These
symmetries mix the quark with the anti-quark sector and they resemble
axial-type of symmetries. Together with the known flavor and spin symmetries
they form a $u(4)$ algebra when a single flavor is considered. It is shown that
the full $U(4)$ set of symmetries breaks spontaneously down to $ U(2) \otimes
U(2)$. The Goldstone modes corresponding to the spontaneously broken currents
are identified. Finally, the precise connection of this theory with the
fundamental QCD is derived and it is investigated under some approximations.
Some physical processes where these extra symmetries may be relevant are
pointed out.


title: Gamma Rays from Small Scale Structures on Long Cosmic Strings

abstract:
  The formation of cusps on long cosmic strings is discussed and the
probability of cusp formation is estimated. The energy distribution of the
gamma-ray background due to cusp annihilation on long strings is calculated and
compared to observations. Under optimistic assumptions about the cusp formation
rate, we find that strings with a mass per unit length $\mu$ less than ${G\mu}
= 10^{-14}$ will have an observable effect. However, it is shown that the
gamma-ray bursters can not be attributed to long ordinary strings (or loops).


title: Should Squarks Be Degenerate?

abstract:
  For generic squark masses, box diagrams with squarks and gluinos give
unacceptably large contributions to neutral meson ($K$, $B$ and $D$) mixing.
The standard solution to this problem is to assume that squarks are degenerate
to a very good approximation. We suggest an alternative mechanism to suppress
squark contributions to flavor changing neutral currents: the alignment of
quark with squark mass matrices. This mechanism arises naturally in the
framework of Abelian horizontal symmetries.


title: Higgs particle detection using jets

abstract:
  We study the possibility of detecting the Higgs boson in the intermediate
mass range via its two jet channel. We consider only Higgs bosons produced in
association with a $t \bar{t}$ pair. Both $t$ and $\bar{t}$ are required to
decay semileptonically to reduce the QCD background. The signal is compared
with the main background, $t \bar{t} + 2$ jets, after appropriate cuts. A
sizable signal above background is seen in our simulation at the parton level.
Use of the $t\bar{t}Z$ channel with $ Z$ decaying to $l^+ l^-$ is suggested for
eliminating theoretical uncertainties in determining the $t \bar{t}H$ signal.


title: Linear and higher order power corrections in semileptonic B decays

abstract:
  In previous work we have developed a relativistic quark model of mesons which
is consistent with all QCD constraints at zeroth and first order in the heavy
quark expansion. Here we obtain first order model predictions for the
differential decay spectrum, the forward-backward asymmetry $A_{FB}$ and the
$D^{\ast}$ polarization parameter $\alpha$ in the decay $B\to D^{\ast}\ell\nu$.
We compare these with the predictions of QCD sum rules at first order. The
model suggests why the corrections allowed at first order are small,
concurrently with substantial corrections at second order.


title:
Hamiltonian Quantization of Effective Lagrangians with Massive Vector
  Fields

abstract:
  Effective Lagrangians containing arbitrary interactions of massive vector
fields are quantized within the Hamiltonian path integral formalism. It is
proven that correct Hamiltonian quantization of these models yields the same
result as naive Lagrangian quantization (Matthews's theorem). This theorem
holds for models without gauge freedom as well as for (linearly or nonlinearly
realized) spontaneously broken gauge theories. The Stueckelberg formalism, a
procedure to rewrite effective Lagrangians in a gauge invariant way, is
reformulated within the Hamiltonian formalism as a transition from a second
class constrained theory to an equivalent first class constrained theory. The
relations between linearly and nonlinearly realized spontaneously broken gauge
theories are discussed. The quartically divergent Higgs self interaction is
derived from the Hamiltonian path integral.


title: Next to leading order eta production at hadron colliders

abstract:
  Inclusive eta production at hadron colliders is considered,based on
evaluation of eta fragmentation functions at next to leading order. Absolute
predictions at LHC and SSC are presented, including the ratio $\eta/\pi^0$,
together with the estimate of the theoretical uncertainty, as a possible
neutral background to the $H\to \gamma\gamma$ detection.


title: A Note on Charge Quantization Through Anomaly Cancellation

abstract:
  In a minimal extension of the Standard Model, in which new neutral fermions
have been introduced, we show that the requirement of vanishing anomalies fixes
the hypercharges of all fermions uniquely. This naturally leads to electric
charge quantization in this minimal scenario which has features similar to the
Standard Model: invariance under the gauge group $SU(2)_L\otimes U(1)_Y$,
conservation of the total lepton number and masslessness for the ordinary
neutrinos. Such minimal models might arise as low-energy realizations of some
heterotic superstring models or $SO(10)$ grand unified theories.


title: New Eaxactly Solvable Hamiltonians: Shape Invariance and Self-Similarity

abstract:
  We discuss in some detail the self-similar potentials of Shabat and
Spiridonov which are reflectionless and have an infinite number of bound
states. We demonstrate that these self-similar potentials are in fact shape
invariant potentials within the formalism of supersymmetric quantum mechanics.
In particular, using a scaling ansatz for the change of parameters, we obtain a
large class of new, reflectionless, shape invariant potentials of which the
Shabat-Spiridonov ones are a special case. These new potentials can be viewed
as q-deformations of the single soliton solution corresponding to the
Rosen-Morse potential. Explicit expressions for the energy eigenvalues,
eigenfunctions and transmission coefficients for these potentials are obtained.
We show that these potentials can also be obtained numerically. Included as an
intriguing case is a shape invariant double well potential whose supersymmetric
partner potential is only a single well. Our class of exactly solvable
Hamiltonians is further enlarged by examining two new directions: (i) changes
of parameters which are different from the previously studied cases of
translation and scaling; (ii) extending the usual concept of shape invariance
in one step to a multi-step situation. These extensions can be viewed as
q-deformations of the harmonic oscillator or multi-soliton solutions
corresponding to the Rosen-Morse potential.


title:
Strange and Non-Strange Meson Fluctuations off the Nambu--Jona-Lasinio
  Soliton

abstract:
  Mesonic fluctuations off the chiral soliton of the Nambu--Jona-Lasinio model
are investigated. The hedgehog configuration is proven to represent a local
extremum of the action. The method is applied to flavor SU(3) and the energy
eigenvalue of the kaon bound state in the soliton background is evaluated which
is the key ingredient for the Callan-Klebanov approach to hyperons. The energy
eigenvalue of the corresponding strange-valence-quark is found to be 183MeV
higher than the energy eigenvalue of the up-valence-quark when 400MeV is
assumed for the up-quark constituent mass.


title: pi-pi scattering in a QCD based model field theory

abstract:
  A model field theory, in which the interaction between quarks is mediated by
dressed vector boson exchange, is used to analyse the pionic sector of QCD. It
is shown that this model, which incorporates dynamical chiral symmetry
breaking, asymptotic freedom and quark confinement, allows one to calculate
$f_\pi$, $m_\pi$, $r_\pi$ and the partial wave amplitudes in $\pi$-$\pi$
scattering and obtain good agreement with the experimental data, with the
latter being well described up to energies \mbox{$E\simeq 700$ MeV}.


title:
Fermion and Anti-Fermion Effective Masses in High Temperature Gauge
  Theories in $CP$-Asymmetric Background

abstract:
  We calculate the splitting between fermion and anti-fermion effective masses
in high temperature gauge theories in the presence of a non-vanishing chemical
potential due to the $CP$-asymmetric fermionic background. In particular we
consider the case of left-handed leptons in the $SU(2)\otimes U(1)$ theory when
the temperature is above $250$ GeV and the gauge symmetry is restored.


title: How to Measure the Mass of the W

abstract:
  We perform a numerical calculation of the total cross section $\sigma(e^+e^-
\rightarrow W^+W^-)$ as a function of energy, taking into account the finite
width of the $W$ and the most important radiative corrections. We present these
results, in tabular form, for several values of $M_W$. Using these results, we
investigate running strategies for integrated luminosities that might be
available at LEP~200 and estimate the accuracy to which it will be possible to
determine the mass of the $W$ by measuring this cross section near threshold.
With an integrated luminosity of $100\ {\rm pb}^{-1}$ it should be possible to
achieve a precision of $100\ {\rm MeV}$, and with an integrated luminosity of
$500\ {\rm pb}^{-1}$, a precision of $60\ {\rm MeV}$.


title: Beyond the Standard Model

abstract:
  The standard model of particle physics is marvelously successful. However, it
is obviously not a complete or final theory. I shall argue here that the
structure of the standard model gives some quite concrete, compelling hints
regarding what lies beyond.


title: Isgur-Wise Functions from the Mit Bag Model

abstract:
  The Isgur-Wise functions for the ground state to ground state semileptonic
decays involving $b \rightarrow c$ transitions are calculated from the
(modified) MIT bag model. It is checked that the results for the decays
$\overline{B} \rightarrow D l \overline\nu$ and $\overline{B} \rightarrow D^* l
\overline\nu$ agree well with experiment. Predictions for the decays $\Lambda_b
\rightarrow \Lambda_c l \overline\nu$, $\overline{B}_s \rightarrow D_s l
\overline\nu$ and $\overline{B}_s \rightarrow D^*_s l \overline\nu$ are given
and discussed.


title: Renormalization Group Improved Exponentiation of Soft Gluons in QCD

abstract:
  We extend the methods of Yennie, Frautschi and Suura to QCD for the summation
of soft gluon effects in which infrared singularities are cancelled to all
orders in $\alpha_s$. An explicit formula for the respective \rngp improved
exponentiated cross section is obtained for $q+\bbar{{q'}}\to q+\bbar{{q'}}+
n(G)$ at SSC energies. Possible applications are discussed.


title:
On the Erasure and Regeneration of the Primordial Baryon Asymmetry by
  Sphalerons

abstract:
  We show that a cosmological baryon asymmetry generated at the GUT scale,
which would be destroyed at lower temperatures by sphalerons and possible new
B- or L-violating effects, can naturally be preserved by an asymmetry in the
number of right-handed electrons. This results in a significant softening of
previously derived baryogenesis-based constraints on the strength of exotic B-
or L-violating interactions.


title:
Quantum Memory Effects in the Measurement of Observables with a
  Continuous Spectrum

abstract:
  In the measurement of a continuous observable Q, the pure components of the
reduced state do, in general, depend on the initial state. For measurements
which attempt to localize the measured system in a certain region R, the
localized wave functions are proportional to the original wave function outside
of R. This `quantum memory' effect shows that it is not possible to perfectly
localize a quantum particle.


title:
Weak Coupling Phase Structureof the Abelian Higgs Model at Finite
  Temperature

abstract:
  Using the 1-loop reduced 3D action of the Abelian Higgs-model we discuss the
order of its finite temperature phase transition. A two-variable saddle point
approximation is proposed for the evaluation of the effective potential. The
strength of the first order case scales like \sim e^{3-6}. Analytic asymptotic
weak coupling and numerical small coupling solutions are compared with special
emphasis on the cancellation of divergences. (Figures are not included, can be
sent upon request from jako@hercules.elte.hu .)


title: The sigma term and the quark number operator in QCD

abstract:
  We discuss the relationship of the forward matrix element of the operator
$\bar\psi\psi$, related to the so-called sigma term, to the quark number. We
show that in the naive quark model in the canonical formalism these quantities
coincide in the limit of small average quark momenta. In the QCD parton model
defined through light-front quantization this result is preserved at leading
perturbative order but it receives radiative corrections. We analyze the
theoretical and phenomenological consequences of this result, which provides a
bridge between a current algebra quantity, the sigma term, and a deep-inelastic
quantity, the parton number.


title: Decuplet Contributions to Hyperon Axial Vector Form Factors

abstract:
  We consider the predictions of chiral perturbation theory for $SU(3)$
breaking in the axial vector form factor $g_1$ measured in semileptonic hyperon
decays. We confirm that if only octet baryon intermediate states are included,
the non-analytic corrections are $\sim 100\%$. These corrections are dominated
by an $SU(3)$-symmetric wavefunction renormalization, which explains the fact
that the ``corrected'' predictions still fit the data well. We argue that the
large corrections are nonetheless strong evidence that this chiral expansion is
breaking down. Following a recent suggestion of Jenkins and Manohar, we then
include contributions from decuplet baryon intermediate states. Unlike these
authors, we do not neglect the octet--decuplet mass difference $\Delta$. We
find that the effects of $\Delta \ne 0$ significantly change the pattern of
corrections: we still find that the decuplet corrections can cancel the large
octet contributions in a non-trivial way, but the corrections no longer favor
the $SU(6)$ values of the axial couplings. We also argue that $D$ and $F$ axial
couplings cannot be reliably extracted from calculations which keep only the
non-analytic corrections.


title: Is Large Lepton Mixing Excluded?

abstract:
  The original \bnum -(or $\bar{\nu}_{\tau}$-) energy spectrum from the
gravitational collapse of a star has a larger average energy than the spectrum
for \bnue since the opacity of \bnue exeeds that of \bnum (or $\nu_{\tau}$).
Flavor neutrino conversion, \bnue $\leftrightarrow$ \bnum, induced by lepton
mixing results in partial permutation of the original \bnue and \bnum spectra.
An upper bound on the permutation factor, $p \leq 0.35$ (99$\%$ CL) is derived
using the data from SN1987A and the different models of the neutrino burst. The
relation between the permutation factor and the vacuum mixing angle is
established, which leads to the upper bound on this angle. The excluded region,
$\sin^2 2\theta > 0.7 - 0.9$, covers the regions of large mixing angle
solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well
as part of region of $\nu_{e} - \nu_{\mu}$ oscillation space which could be
responsible for the atmospheric muon neutrino deficit. These limits are
sensitive to the predicted neutrino spectrum and can be strengthened as
supernova models improve.


title: The Earth Effect in the MSW Analysis of the Solar Neutrino Experiments

abstract:
  We consider the Earth effect in the MSW analysis of the Homestake,
Kamiokande, GALLEX, and SAGE solar neutrino experiments. Using the
time-averaged data and assuming two-flavor oscillations, the large-angle region
of the combined fit extends to much smaller angles (to $\sin^22\theta \simeq
0.1$) than when the Earth effect is ignored. However, the additional constraint
from the Kamiokande II day-night data excludes most of the parameter space
sensitive to the Earth effect independent of astrophysical uncertainties, and
leaves only a small large-angle region close to maximal mixing at 90\% C.L. The
nonadiabatic solution remains unaffected by the Earth effect and is still
preferred. Both theoretical and experimental uncertainties are included in the
analysis.


title:
Perturbative QCD Fragmentation Functions for $B_c$ and $B_c^*$
  Production

abstract:
  The dominant production mechanism for ${\bar b} c$ bound states in high
energy processes is the production of a high energy ${\bar b}$ or $c$ quark,
followed by its fragmentation into the ${\bar b} c$ state. We calculate the
fragmentation functions for the production of the S-wave states $B_c$ and
$B_c^*$ to leading order in the QCD coupling constant. The fragmentation
probabilities for ${\bar b} \rightarrow B_c$ and ${\bar b} \rightarrow B_c^*$
are approximately $2.2 \times 10^{-4}$ and $3.1 \times 10^{-4}$, while those
for $c \rightarrow B_c$ and $c \rightarrow B_c^*$ are smaller by almost two
orders of magnitude.


title: Disoriented chiral condensate in (1+1) Lorentz-invariant geometry

abstract:
  We consider isospin correlations of pions produced in a relativistic nuclear
collision, using an effective theory of the chiral order parameter. Our theory
has (1+1) Lorentz invariance as appropriate for the central rapidity region. We
argue that in certain regions of space correlations of the chiral order
parameter are described by the fixed point of the (1+1) WZNW model. The
corresponding anomalous dimension determines scaling of the probability to
observe a correlated cluster of pions with the size of this cluster in
rapidity. Though the maximal size of clusters for which this scaling is
applicable is cut off by pion mass, such clusters can still include
sufficiently many particles to make the scaling observable.


title: Dark Matters in Axino Gravitino Cosmology

abstract:
  It is suggested that the axino mass in the 1 MeV region and gravitino mass in
the eV region can provide an axino lifetime of order of the time of photon
decoupling. In this case, some undecayed axinos act like cold dark matters and
some axino decay products (gravitinos and hot axions) act like hot dark matters
at the time of galaxy formation.


title: Non-Trivial Phase Structure of $\phi ^{4}$-Theory at Finite Temperature

abstract:
  The effective potential for the local composite operator $\phi^{2}(x)$ in
$\lambda \phi^{4}$-theory is investigated at finite temperature in an approach
based on path-integral linearisation of the $\phi^4 $-interaction. At zero
temperature, the perturbative vacuum is unstable, because a non-trivial phase
with a scalar condensate $\langle \phi ^{2} \rangle _{0}$ has lower effective
action. Due to field renormalisation, $\langle \lambda \phi ^{2} \rangle _{0}$
is renormalisation group invariant and leads to the correct scale anomaly. At a
critical temperature $T_{c}$ the non-perturbative phase becomes meta-stable
implying a first order phase-transition to the perturbative phase. The ratio
$\langle\lambda \phi^{2} \rangle _{0} / T_{c}^{2} \approx 62$ turns out to be a
universal constant.


title: Comment on SU(16) grand unification

abstract:
  In a recent paper on SU(16) grand unification, because of the presence of
intermediate-energy gauge groups containing products of U(1) factors which are
not orthogonal among themselves, the renormalization-group treatment has a few
small errors. I correct it. I emphasize that one should not switch gauge
couplings at the various thresholds. It is easier, and it avoids errors, to use
throughout the gauge couplings of the standard model, and compute at each
threshold, in the usual way, the extra contributions to the beta functions from
the extra non-decoupled fields. I also point out that the SU(16) grand
unification theory, due to the large number of scalars present in it, is not
asymptotically free. It becomes a strong-coupling theory at energies only
slightly larger than the unification scale.


title: Chiral symmetry and many-body nonleptonic decays of heavy hadrons

abstract:
  We suggest that, similar to the many applications of chiral effective
Lagrangian made recently to semileptonic decays of heavy hadrons involving
Goldstone bosons, chiral symmetry can also be applied to many-body nonleptonic
decays of heavy hadrons. As examples we establish the chiral effective
Hamiltonian for some typical many-body nonleptonic decays of bottom hadrons. We
discuss the lowest-order contributions coming from such a Hamiltonian. We
emphasize that wide applications of this method are possible.


title: The Standard Model of Leptons as a Purely Vectorial Theory

abstract:
  We propose a way to reconcile the Standard Model of leptons with a purely
vectorial theory. The observed neutrino is predicted to be massless. The
unobservability of its partner and the $V-A$ structure of the weak currents are
given the same origin.


title:
Bounding the Higgs Boson Mass in the Next-to-Minimal Supersymmetric
  Standard Model

abstract:
  We discuss the upper bound on the lightest CP-even Higgs boson mass in the
next-to-minimal supersymmetric standard model within the framework of a low
energy renormalisation group analysis. We find $m_h$ < 146 GeV for $m_t$ = 90
GeV, decreasing to $m_h$ < 123 GeV for $m_t$ = 180 GeV.


title:
The Rosner-Worah Type Quark Mass Matrix and Ansatz of Maximal CP
  Violation

abstract:
  A democratic form version of the Rosner-Worah quark mass matrix is discussed
from a phenomenological point of view. It is pointed out that an ansatz of
"maximal CP violation" can provide reasonable values of the Kobayashi-Maskawa
mixings.


title: Diquark electromagnetic form factors in a Nambu-Jona-Lasinio model

abstract:
  Electromagnetic properties of diquarks are investigated in the framework of a
color-octet Nambu-Jona-Lasinio model, which describes baryons as bound states
of diquarks and quarks. We calculate the electromagnetic form factors of scalar
and axial vector diquark bound states using the gauge--invariant proper--time
regularization. The nucleon charge radii and magnetic moments are estimated in
a simple additive diquark--quark model. This picture reproduces the qualitative
features such as the negative charge radius of the neutron. Within this model
axial vector diquarks are seen to be important.


title:
Unification of Couplings and the Dynamical Breakdown of the Electroweak
  Symmetry

abstract:
  I discuss the properties of the minimal supersymmetric extension of the
standard model, in the case in which there is a dynamical breakdown of the
electroweak symmetry induced by the formation of condensates of the third
generation of quarks and their supersymmetric partners. The top quark and Higgs
mass predictions derived within this scheme are essentially equivalent to those
ones obtained from the requirement of bottom-tau Yukawa coupling unification in
a supersymmetric grand unified scenario, if the compositeness scale is
identified with the grand unification scale. I give an explanation of this
interesting result, for which the relevance of the infrared quasi fixed point
on the top quark Yukawa coupling is emphasized.


title:
NLO calculation of $\epsilon^{\prime}/\epsilon$ in QCD and QED within
  the lattice QCD framework

abstract:
  We present the results of our recent calculation of $\epsilon^{\prime}/
\epsilon$ at the Next-to-Leading (NLO) order in QCD and QED, in the framework
of $\DSone$ Effective Hamiltonians. The operator matrix elements are taken from
lattice QCD, at a scale $\mu=2\,\,\mbox{GeV}$. NLO corrections seem to lower
the value of $\epsilon^{\prime}/\epsilon$, favouring the experimental result of
E731. Contributions from different operators are analyzed and dependence on
$\mt$, $\mu$ and $\Lambda_{\sss QCD}$ discussed. (Talk given at the XXVIIIth
Rencontres de Moriond, ``Electro-Weak Interactions and Unified Theories'',
March 13-19 1993).


title: Radiative Corrections to Supersymmetric Higgs Boson Masses

abstract:
  We discuss the large radiative corrections to the masses of supersymmetric
Higgs bosons in the MSSM and in its simplest extension, the NMSSM, with
particular attention paid to the bounds on the lightest CP-even Higgs mass
found in both models. In the case of the MSSM, these corrections are found to
be primarily associated with the effects top quark and stop squark loops, while
for extended models they also include significant contributions from Higgs and
Higgsino loops. (Talk presented at SUSY-93, Boston, March 1993)


title: Non-Perturbative Production of Multi-Boson States and Quantum Bubbles

abstract:
  The amplitude of production of $n$ on-mass-shell scalar bosons by a highly
virtual field $\phi$ is considered in a $\lambda \phi^4$ theory with weak
coupling $\lambda$ and spontaneously broken symmetry. The amplitude of this
process is known to have an $n!$ growth when the produced bosons are exactly at
rest. Here it is shown that for $n \gg 1/\lambda$ the process goes through
`quantum bubbles', i.e. quantized droplets of a different vacuum phase, which
are non-perturbative resonant states of the field $\phi$. The bubbles provide a
form factor for the production amplitude, which rapidly decreases above the
threshold. As a result the probability of the process may be heavily suppressed
and may decrease with energy $E$ as $\exp (-const \cdot E^a)$, where the power
$a$ depends on the number of space dimensions. Also discussed are the quantized
states of bubbles and the amplitudes of their formation and decay.


title: Single Lepton Production at Large Transverse Momentum

abstract:
  We study the production of single isolated leptons at large transverse
momentum, $p_T^\ell > M_W/2$. The dominant source of such leptons is production
of an on-shell $W$ boson recoiling against a hard jet. Vetoing this jet forces
the $W$ boson to be produced off resonance and significantly reduces the
standard model cross section, thereby enhancing the discovery prospects for non
standard model physics. A significant number of events have the topologically
interesting signature of a large $p_T$ lepton balancing a jet with little
measured missing transverse energy.


title:
Salient Features of High-Energy Multiparticle Distributions Learned from
  Exact Solutions of 1-d Ising Model

abstract:
  We have derived explicit expressions in the 1-d Ising model for multiplicity
distributions $P_{\del\xi}(n)$ and factorial moments $F_q(\del\xi)$. We
identify the salient features of $P_{\del\xi}(n)$ that lead to scaling,
$F_q(\del\xi)=\F_q[F_2]$, and universality. These results compare well with the
presently available high-energy data of $\bar{p}p$ and $e^+e^-$ reactions. We
point out the important features that should be studied in future higher-energy
experiments of multiparticle productions in $pp$, $\bar{p}p$, $ep$, $e^+e^-$,
and $NN$. We also make comments on comparisons with KNO and negative-binomial
distributions.


title:
Self-consistently Improved Finite Temperature Effective Potential for
  Gauge Theories

abstract:
  The finite temperature effective potential of the Abelian Higgs Model is
studied using the self-consistent composite operator method, which sums up the
contributions of daisy and superdaisy diagrams. The effect of the momentum
dependence of the effective masses is estimated by using a Rayleigh-Ritz
variational approximation.


title: Using $b \to s\gamma$ to Probe Top Quark Couplings

abstract:
  Possible anomalous couplings of the top-quark to on-shell photons and gluons
are constrained by the recent results of the CLEO Collaboration on both
inclusive and exclusive radiative $B$ decays. We find that the process \bsg\
can lead to reasonable bounds on both the anomalous electric and magnetic
dipole moments of the top-quark, while essentially no limits are obtained on
the corresponding chromoelectric and chromomagnetic moments, which enter the
expression for the decay rate only through operator mixing.


title:
The Role of Zero-Modes in the Canonical Quantization of Heavy-Fermion
  QED in Light-Cone Coordinates

abstract:
  Four-dimensional heavy-fermion QED is studied in light-cone coordinates with
(anti-)periodic field boundary conditions. We carry out a consistent light-cone
canonical quantization of this model using the Dirac algorithm for a system
with first- and second-class constraints. To examine the role of the zero
modes, we consider the quantization procedure in {the }zero-mode {and the
non-zero-mode} sectors separately. In both sectors we obtain the physical
variables and their canonical commutation relations. The physical Hamiltonian
is constructed via a step-by-step exclusion of the unphysical degrees of
freedom. An example using this Hamiltonian in which the zero modes play a role
is the verification of the correct Coulomb potential between two heavy
fermions.


title:
Novel Color Transparency Effect: Scanning the Wave Function of Vector
  Mesons

abstract:
  We demonstrate how the virtual photoproduction of vector mesons on nuclei
scans the wave function of vector mesons from the large non-perturbative
transverse size $\rho \sim R_{V}$ down to the small perturbative size $\rho
\sim 1/\sqrt{Q^{2}}$. Thee mechanism of scanning is based on color transparency
and QCD predicted spatial wave function of quark-antiquark fluctuations of
virtual photons. A rich, energy- and $Q^{2}$-dependent, pattern of the nuclear
shadowing and antishadowing is predicted, which can be tested at the European
Electron Facility and SLAC.


title: Branching Processes and Multi-Particle Production

abstract:
  The general theory of the branching processes is used for establishing the
relation between the parameters $k$ and $\bar n$ of the negative binomial
distribution. This relation gives the possibility to describe the overall data
on multiplicity distributions in $pp (p\bar p)$-collisions for energies up to
900 GeV and to make several interesting predictions for higher energies. This
general approach is free from ambiguities associated with the extrapolation of
the parameter $k$ to unity.


title: Thermal quark production in pure glue and quark gluon plasmas

abstract:
  We calculate production rates for massless $(u,d)$ and massive $(s,c,b)$
quarks in pure glue and quark gluon plasmas to leading order in the strong
coupling constant $g$. The leading contribution comes from gluon decay into
$q\bar q$ pairs, using a thermal gluon propagator with finite thermal mass and
damping rate. The rate behaves as $\alpha_S^2(\ln 1/\alpha_S)^2 T^4$ when $m,
\alpha_S \rightarrow 0$ and depends linearly on the transverse gluon damping
rate for all values of the quark mass $m$. The light quark ($u$, $d$, $s$)
chemical equilibration time is approximately 10-100 $T^{-1}$ for $g=$2-3, so
that quarks are likely to remain far from chemical equilibrium in
ultrarelativistic nuclear collisions.


title:
Coherent Nuclear Diffractive Production of Minijets - Illuminating Color
  Transparency

abstract:
  The cross section for coherent nuclear processes in which an incident meson
or photon dissociates diffractively into two jets of high relative transverse
momentum (between about 1 and 3 GeV/c) is found to be proportional in QCD to
$A^2$ in a wide kinematical region. The leading correction to this is a
significant positive term $\propto A^{7/3}$ caused by nuclear
multiple-scattering. We find also that shadowing of hard diffractive processes
reappears as a leading twist effect in the TeV energy range.


title:
Corrections from Low Momentum Physics to Heavy Quark Symmetry Relations
  for $B\rightarrow De\bar \nu_e$ and $B\rightarrow D^*e \bar \nu_e$ Decay

abstract:
  Heavy quark symmetry relations for $B\rightarrow De\bar \nu_e$ and
$B\rightarrow D^*e \bar \nu_e$ form factors receive corrections suppressed by
powers of the charm quark mass. For small up and down quark massed the leading
corrections of order $(1/m_c)^{n+2}~n = 0,1,2,...$ have a nonanalytic
dependence on the light quark masses of the form $\ell n m_\pi^2$ for $n = 0$
and $(1/m_\pi)^n$ for $n = 1,2, ...$~. These corrections arise from very low
momentum physics (i.e., well below the chiral symmetry breaking scale) and are
computed using chiral perturbation theory. They are typically of order a few
percent.


title: New Supersymmetric Option for Two Higgs Doublets

abstract:
  If the standard electroweak gauge model is embedded in a larger theory which
is supersymmetric and the latter breaks down to the former at some mass scale,
then the reduced Higgs potential at the electroweak mass scale may differ from
that of the well-known minimal supersymmetric extension. Specifically, if the
larger theory is based on $\rm {SU(2)_L \times SU(2)_R \times U(1)}$, an
interesting alternative exists for two Higgs doublets.


title: Exotic Bound State Production at Hadron Colliders

abstract:
  Hadronic production of nonrelativistic boundstates of $b^{\prime}$ or
isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC
energies. QCD corrections to production and decay rates are incorporated. Large
rates for final states from $\eta_{b^{\prime}}\rightarrow HZ$ are predicted.


title: Walking Technicolor And The $Zb\bar b$ Vertex

abstract:
  A slowly running technicolor coupling will affect the size of non-oblique
corrections to the $Zb\bar b$ vertex from extended technicolor dynamics. We
show that while ``walking technicolor'' reduces the magnitude of the
corrections, they generally remain large enough to be seen at LEP.


title:
The off-Shell Electromagnetic Vertex of the Nucleon in Chiral
  Perturbation Theory

abstract:
  We study the electromagnetic vertex of a nucleon in next-to-leading order
chiral perturbation theory (CPT). We consider the case where one of the
nucleons at the $\gamma$NN vertex is off its mass shell. We define relevant
measures for the off-shell dependence in the limited kinematical range allowed,
and analyze their expansion in the pion mass. The leading nonanalytic
contributions are calculated to estimate their size.


title:
Complex Time Solutions with Nontrivial Topology and Multi Particle
  Scattering in Yang-Mills Theory

abstract:
  A classical solution to the Yang-Mills theory is given a new semiclassical
interpretation in terms of particle scattering. It solves the complex time
boundary value problem, which arises in the semiclassical approximation to a
multi particle transition probability in the one-instanton sector at fixed
energy. The imaginary part of the action of the solution on the complex time
contour and its topological charge obey the same relation as the self-dual
Euclidean configurations. Hence the solution is relevant for the problem of
tunneling with fermion number violation in the electroweak theory. It describes
transitions from an initial state with a smaller number of particles to a final
state with a larger number of particles. The implications of these results for
multi particle production in the electroweak theory are also discussed.


title:
Recent Results in Chiral Perturbation Theory for Mesons Containing a
  Single Heavy Quark

abstract:
  Chiral symmetry and heavy quark symmetry constrain the interactions of mesons
containing a single heavy quark with low-momentum pions. Chiral corrections to
the Isgur-Wise function for $\bar B_s \rightarrow D_s^{(*)}$ versus $\bar B
\rightarrow D^{(*)}$ semileptonic decay, the ratio of heavy meson decay
constants $f_{D_s}/ f_D$ or $f_{B_s}/ f_B$, the amplitudes for $B_s - \bar B_s$
versus $B^0 - \bar B{\,}^0$ mixing, and the heavy meson mass splittings are
calculated in chiral perturbation theory. (Invited talk Rencontres de Moriond
1993)


title: General Issues in the Evolution of Fermion Masses and Mixings

abstract:
  General issues in the renormalization group evolution of fermion masses and
mixings is discussed. An effective fixed point in the top quark Yukawa coupling
can strongly constrain its value at the electroweak scale. Predictions
following from Yukawa coupling unification are affected by threshold
corrections at the grand unified scale. The Landau pole translates into an
upper limit on the strong gauge coupling $\alpha _3(M_Z)$. Given the hierarchy
in the fermion sector, the evolution of the Cabbibo-Kobayashi-Maskawa matrix
can be expressed in terms of a single scaling parameter $S$. Using this scaling
factor and analogous scaling factors for the quark and lepton masses, we
outline a systematic strategy that readily yields electroweak predictions for
any GUT scale texture.}


title:
Colour Screening, Quark Propagation in Nuclear Matter and the Broadening
  of the Momentum Distribution of Drell-Yan Pairs

abstract:
  We calculate the broadening of the transverse momentum distribution of a
quark propagating through nuclear matter. Colour screening plays a fundamental
role in that it cuts off quark-nucleon interactions with soft gluons. The mean
transverse momentum of the quark acquired along its trajectory, observed via
Drell-Yan pairs, is related to it the ratio of the total inelastic
meson-nucleon cross section it to the meson mean squared radius. Parameter-free
calculations agree with the data.


title:
One-loop helicity amplitudes for all 2 -> 2 processes in QCD and N=1
  supersymmetric Yang-Mills theory

abstract:
  One loop corrections to the helicity amplitudes of all 2 -> 2 subprocesses
are calculated in QCD and in N=1 supersymmetric Yang-Mills theory using two
versions of dimensional regularization: the `t~Hooft-Veltman scheme and
dimensional reduction. Studying the structure of the soft and collinear
singularities, we found universal transition rules for the squared matrix
element which can be used to translate the results obtained in these schemes to
the results valid in the conventional dimensional regularization scheme. With
explicit calculation it is demonstrated that the one loop helicity amplitudes
of the 2 -> 2 subprocesses calculated using dimensional reduction in the N=1
supersymmetric $SU(N)$ gauge theory respect the supersymmetry Ward identities.
Our transition rules can also be used to calculate the next-to-leading order
Altarelli-Parisi kernels in the dimensional reduction scheme when they satisfy
supersymmetry Ward identities as well.


title: On parton distributions beyond the leading order

abstract:
  The importance of properly taking into account the factorization scheme
dependence of parton distribution functions is emphasized. A serious error in
the usual handling of this topic is pointed out and the correct procedure for
transforming parton distribution functions from one factorisation scheme to
another recalled. It is shown that the conventional $\overline{\rm {MS}}$ and
DIS definitions thereof are ill-defined due to the lack of distinction between
the factorisation scheme dependence of parton distribution functions and
renormalisation scheme dependence of the strong coupling constant $\alpha_s$. A
novel definition of parton distribution functions is suggested and its role in
the construction of consistent next-to-leading order event generators briefly
outlined.


title: High Temperature Response Functions and the Non-Abelian Kubo Formula

abstract:
  We describe the relationship between time-ordered and retarded response
functions in a plasma. We obtain an expression, including the proper
$i\epsilon$-prescription, for the induced current due to hard thermal loops in
a non-Abelian theory, thus giving the non-Abelian generalization of the Kubo
formula. The result is closely related to the eikonal for a Chern-Simons theory
and is relevant for a gauge-invariant description of Landau damping in the
quark-gluon plasma at high temperature.


title: Quantum Statistical Metastability Revisited

abstract:
  We calculate the decay rate for a state prepared in a thermal density matrix
centered on a metastable ground state. We find a rate that is intrinsically
time {\it dependent}, as opposed to the {\it constant} rates of previous works.
The rate vanishes at early times, rises to a maximum and eventually falls-off
to zero as a consequence of unitary time evolution. Finally, we discuss
extensions of this calculation to field theories and possible implications for
both sphaleron mediated transitions and first order inflationary theories.


title:
Model Independent Upper Bound on the Lightest Higgs Boson Mass in
  Supersymmetric Standard Models

abstract:
  One of the main features of the Minimal Supersymmetric Standard Model (MSSM)
is the existence of an absolute tree-level upper bound $m_h$ on the mass of the
$CP=+1$ lightest Higgs boson, equal to $m_Z$, that could affect detectability
at future colliders. The above bound is spoiled by {\bf radiative corrections}
and by an {\bf enlarged Higgs sector}, as {\em e.g.} a gauge singlet. Radiative
corrections in the MSSM can push the upper bound up to $115\ GeV$ for $m_t
\simlt 150\ GeV$. The presence of an enlarged Higgs sector changes the previous
upper bound to one depending on the electroweak scale, $\tan \beta$ and the
gauge and Yukawa couplings of the theory. When radiative corrections are
included, the allowed region in the $(m_h,m_t)$ plane depends on the scale
$\Lambda$ below which the theory remains perturbative. In particular, for
models with arbitrary Higgs sectors and couplings saturating the scale
$\Lambda=10^{16}\ GeV$ we find $m_h \simlt 155\ GeV$ and $m_t \simlt 190\ GeV$.


title:
Production, Collection and Utilization of Very Long-Lived Heavy Charged
  Leptons

abstract:
  If a fourth generation of leptons exists, both the neutrino and its charged
partner must be heavier than 45 GeV. We suppose that the neutrino is the
heavier of the two, and that a global or discrete symmetry prohibits
intergenerational mixing. In that case, non-renormalizable Planck scale
interactions will induce a very small mixing; dimension five interactions will
lead to a lifetime for the heavy charged lepton of $O(1-100)$ years. Production
of such particles is discussed, and it is shown that a few thousands can be
produced and collected at a linear collider. The possible uses of these heavy
leptons is also briefly discussed.


title: Color Transparency and Fermi Motion

abstract:
  It is argued that color transparency in quasi elastic scattering of electrons
and hadrons on nuclei is possible only due to Fermi-motion. We found a strong
dependence of nuclear transparency on Bjorken x in (e,e'p), it is close to the
Glauber model expectations at $x>1$, but increases and even exceeds one at
$x<1$. It is argued that color transparency is accompanied by large
longitudinal momentum transfer to nuclear matter during the passage of the
small size wave packet. \vspace{\fill}


title: Discrete Time Quantum Mechanics

abstract:
  This paper summarizes a research program that has been underway for a decade.
The objective is to find a fast and accurate scheme for solving quantum
problems which does not involve a Monte Carlo algorithm. We use an alternative
strategy based on the method of finite elements. We are able to formulate fully
consistent quantum-mechanical systems directly on a lattice in terms of
operator difference equations. One advantage of this discretized formulation of
quantum mechanics is that the ambiguities associated with operator ordering are
eliminated. Furthermore, the scheme provides an easy way in which to obtain the
energy levels of the theory numerically. A generalized version of this
discretization scheme can be applied to quantum field theory problems. The
difficulties normally associated with fermion doubling are eliminated. Also,
one can incorporate local gauge invariance in the finite-element formulation.
Results for some field theory models are summarized. In particular, we review
the calculation of the anomaly in two-dimensional quantum electrodynamics (the
Schwinger model). Finally, we discuss nonabelian gauge theories.


title:
Hadron production in gamma-gamma collisions as a background for e+e-
  linear colliders

abstract:
  Drees and Godbole have proposed that, at the interaction point of an e+e-
linear collider, one expects a high rate of hadron production by gamma-gamma
collisions, providing an additional background to studies in e+e- annihilation.
Using a simplified model of the gamma-gamma cross section with soft and
jet-like components, we estimate the expected rate of these hadronic events for
a variety of realistic machine designs. The final background rates are quite
small, and they become smaller still when viewed with a realistic detector
simulation.


title:
When Are Radiative Corrections Important in the Minimal Supersymmetric
  Model?

abstract:
  Precision electroweak measurements at LEP currently check the validity of the
Standard Model to about one part in a thousand. Any successful model of physics
beyond the Standard Model must be consistent with these observations. The
impact of radiative corrections on the Minimal Supersymmetric Model (MSSM) is
considered. The influence of supersymmetric particles on precision electroweak
measurements is generally negligible since radiative corrections mediated by
supersymmetric particles are suppressed by a factor of order $m_Z^2/M_{\rm
SUSY}^2$ (where $M_{\rm SUSY}$ is the scale characterizing the scale of
supersymmetric particle masses). However, there are a few pertinent exceptions.
For example, the radiative corrections to the rare decay $b\to s\gamma$ from
charged Higgs and supersymmetric particle exchange can be of the same order as
the Standard Model contribution. Large radiative corrections also lead to
modifications of MSSM tree-level (natural) relations. The largest corrections
of this type occur in the MSSM Higgs sector and are enhanced by powers of the
top quark mass. The consequences of the radiatively corrected MSSM Higgs sector
are briefly discussed.


title: The Process of Generation of Mass, The Higgs Boson, and Dark Matter

abstract:
  A dynamical mechanism of symmetry breaking in which gauge and matter fields
play an active role is proposed. It basically represents a covariant
generalization of the mechanism responsible for superconductivity, and provides
a {\em natural} mechanism of generation of mass which is not in conflict with
the present value of the cosmological constant. When applied to
SU(2)$\times$U(1) leads to exactly the same physics (Lagrangian density) as the
Standard Model but modifying {\em only} the Higgs sector. It also predicts the
appearance over all space of a classical scalar field as well as the existence
of density fluctuations. According to it, space would be filled with a
macroscopically large number of Higgs bosons which now appear as light, stable
scalar particles {\em decoupled} from ordinary matter and radiation. Therefore
they would play the same role as the Cooper pairs in superconductivity and
would be a natural candidate for dark matter.


title: Measuring Chirally Odd Wave Functions with Helicity Flip Form Factors

abstract:
  We consider the role of chirally odd wave functions in hard exclusive
reactions. Such wave functions have the quarks oriented in the opposite
helicity configuration from those assumed in the short-distance limit and are
generally associated with non-zero orbital angular momentum. Calculations in
the impulse approximation allow for non-zero helicity flip amplitudes while the
conventional factorization prescription for exclusive processes does not. By
introducing a new approach, we show how helicity flip form factors are
nevertheless calculable in QCD.


title: On Exclusive Reactions in the Time-Like Region

abstract:
  The electromagnetic form factors of the proton in the time-like region and
two-photon annihilations into proton-antiproton are investigated. To calculate
these processes at moderately large $s$ we use a variant of the Brodsky-Lepage
hard-scattering formalism where diquarks are considered as quasi-elementary
constituents of baryons. The proton wave function and the parameters
controlling the diquark contributions are determined from fits to space-like
data. We also comment on the decay $\eta_c \to p\bar{p}$.


title:
Vacuum fine tuning and empirical estimations of masses of the top-quark
  and Higgs boson

abstract:
  The fine-tuning principles are analyzed in search for predictions of
top-quark and Higgs-boson masses. The modification of Veltman condition based
on the compensation between fermion and boson vacuum energies within the
Standard Model multiplets is proposed. It is supplied with the stability under
rescaling and with the requirement of minimum for the physical v. e. v. for the
Higgs field (zero anomalous dimension). Their joint solution for top-quark and
Higgs-boson couplings exists for the cutoff $\Lambda \approx 2.3 \cdot
10^{13}\,GeV$ that yields the low-energy values $m_t = 151 \pm 4\,GeV; m_H =
195 \pm 7\,GeV$.


title: The Stability of the Weak Skyrmions

abstract:
  We consider a set of gauge invariant terms in higher order effective
Lagrangians of the strongly interacting scalar of the electroweak theory. The
terms are introduced in the framework of the hidden gauge symmetry formalism.
The usual gauge term is known to stabilize the skyrmion but only in the large
vector mass limit. We find that adding higher-order gauge terms is insufficient
to insure stability. We then proceed to analyze other gauge invariant
interaction terms. Some of the conclusions also apply to QCD skyrmions.


title: LEP and radiative electroweak breaking close the light gluino window

abstract:
  We show that the LEP lower bound on the chargino mass, in conjunction with
the well motivated theoretical requirement of radiative electroweak symmetry
breaking, imply an upper bound on the lightest Higgs boson mass
($m_h\lsim62\GeV$) in a supersymmetry breaking scenario where the gluino mass
is a few GeV. Moreover, Higgs searches at LEP in the context of this model
require $m_h\gsim61\GeV$. The remaining experimentally allowed region in the
five-dimensional parameter space of this light gluino model is severely
fine-tuned (with $\tan\beta=1.88-1.89$ and $m_t=114.0-114.3\GeV$) and
cosmologically troublesome (with a neutralino relic abundance over {\it
five-hundred times larger than allowed}). Modest improvements in sensitivity in
LEP Higgs searches and Tevatron top-quark searches should soon exclude this
theoretically disfavored model completely.


title:
Five Phases of Weak Neutral Current Experiments from the Perspective of
  a Theorist

abstract:
  I give my personal perspective on the past, present, and future of weak
neutral current experiments, emphasizing the experimental inputs; the
theoretical difficulties and inputs; the role of model independent and global
analyses; and the implications at each stage. hep-ph/yymmnnn


title: Hadronization in Nuclear Matter

abstract:
  Nuclei are unique analyzers of the space-time development of jets at early
stage. We argue that the gluon bremsstrahlung, rather than the color string, is
the main mechanism of hadronization of highly virtual quarks produced in a hard
interaction. It results in an energy- and time-independent density of energy
loss, like a color string, but steeply dependent on the quark virtuality.
Effects of formation zone (FZ) and color transparency (CT) substantially affect
the jet quenching in a nuclear matter. The latter also plays an important role
in the broadening of transverse momentum distribution of a quark passing a
nucleus. Parameter-free calculations provide a good description of available
data on nuclear effects in the leading hadron production in deep-inelastic
lepton scattering, back-to-back high-$p_T$ hadron pair production, broadening
of the transverse momentum distribution in the Drell-Yan process of lepton pair
production on nuclei.