title: BFKL versus O(\alpha_s^3) Corrections to Large-rapidity Dijet Production

abstract:
  We examine dijet production at large rapidity intervals at Tevatron energies
by comparing an exact ${\cal O}(\alpha_s^3)$ calculation with the BFKL
approximation, which resums the leading powers of the rapidity interval $y$ to
all orders in $\alpha_s$. We analyze the dependence of the exact ${\cal
O}(\alpha_s^3)$ calculation on the jet cone-size as a function of $y$, and use
this cross section to define an ``effective rapidity'' $\hat y$ which reduces
the error that the large-$y$ approximation induces on the kinematics. Using
$\hat y$ in the BFKL resummation, we reexamine jet production at large
transverse momenta and the transverse momentum decorrelation of the tagging
jets. We find less dramatic, but still significant, effects than found
previously using the large-$y$ approximation.


title: Inclusive photoproduction of hadrons at HERA

abstract:
  We study inclusive photoproduction of hadrons at HERA via both direct and
resolved photons to next-to-leading order (NLO) in the QCD-improved parton
model. We predict transverse-momentum ($\pt$) and rapidity ($\ylab$)
distributions and compare them with recent data by the H1 Collaboration. To
estimate the theoretical error of the predictions, we investigate their
dependence on the choice of renormalization and factorization scales,
subtraction scheme, and parton density functions (PDF). We also introduce a new
NLO set of fragmentation functions for charged pions and kaons, which is
extracted from $e^+e^-$ data at $\sqrt s=29$ GeV, and confront it with the H1
data. This enables us to test quantitatively the QCD-improved parton model and,
in particular, the factorization theorem at the quantum level.


title:
Exclusive Processes: Tests of Coherent QCD Phenomena and Nucleon
  Substructure at CEBAF -

abstract:
  Measurements of exclusive processes such as electroproduction,
photoproduction, and Compton scattering are among the most sensitive probes of
proton structure and coherent phenomena in quantum chromodynamics. The
continuous electron beam at CEBAF, upgraded in laboratory energy to 10--12 GeV,
will allow a systematic study of exclusive, semi-inclusive, and inclusive
reactions in a kinematic range well-tuned to the study of fundamental nucleon
and nuclear substructure. I also discuss the potential at CEBAF for studying
novel QCD phenomena at the charm production threshold, including the possible
production of nuclear-bound quarkonium.


title: High Energy Photon-Photon Collisions -

abstract:
  The collisions of high energy photons produced at an electron-positron
collider provide a comprehensive laboratory for testing QCD, electroweak
interactions, and extensions of the Standard Model. The luminosity and energy
of the colliding photons produced by back-scattering laser beams is expected to
be comparable to that of the primary $e^+e^-$ collisions. In this overview, we
shall focus on tests of electroweak theory in photon-photon annihilation,
particularly $\gamma\gamma \rightarrow W^+ W^-$, $\gamma\gamma \rightarrow $
Higgs bosons, and higher-order loop processes, such as $\gamma\gamma
\rightarrow \gamma\gamma, Z \gamma$ and $ZZ.$ Since each photon can be resolved
into a $W^+ W^-$ pair, high energy photon-photon collisions can also provide a
remarkably background-free laboratory for studying $WW$ collisions and
annihilation. We also review high energy $\gamma\gamma$ tests of quantum
chromodynamics, such as the scaling of the photon structure function, $t \bar
t$ production, mini-jet processes, and diffractive reactions.


title:
LEP $e^{+}\,e^{-}\,\rightarrow\,\mu^{+}\, \mu^{-}\,\gamma\,\gamma$
  events and their consequences at future $e^+e^-$ colliders

abstract:
  The $e^{+}\,e^{-}\,\rightarrow\,l^{+}\, \l^{-}\,\gamma\,\gamma$ anomalous
events, detected by $L3$ de\-tec\-tor at $e^+ e^-$ $CERN-LEP$ collider have
been analysed. It has been shown that the interpretation of such events as a
manifestation of scalar (pseudoscalar) resonance with the mass of 60 GeV
contradicts other experimental data. In case of a possible existence that kind
of resonance, the perspectives to discover one in some processes at future
$e^+e^-$ colliders have been discussed.


title:
Anomalous di-photon production at LEP: possible consequences at FNAL
  hadron collider

abstract:
  The hypothetic R--resonance production (anomalous "$l\bar l\gamma\gamma$"
events at LEP) with 60 GeV mass at FNAL hadron collider has been considered.
The cross-section of this R-resonance production with the consequent decay $R
\to \gamma\gamma$ is obtained. Various distributions of leptons and photons in
the process $p\bar p \to l\bar l R (\to \gamma\gamma) X$ are calculated.


title:
New Measurement of the Single Diffraction Dissociation and the Nature of
  the Nature of the Pomeron

abstract:
  Recent data on single diffraction dissociation, measured by the CDF at the
Tevatron show a moderate increase with energy of the cross section, thus
confirming the predictions based on the dipole pomeron model.


title: Signals for Top Quark Anomalous Chromomagnetic Moments at Colliders

abstract:
  The Tevatron and the Next Linear Collider(NLC) will be excellent tools for
probing the detailed nature of the top quark. We perform a preliminary
examination of the influence of an anomalous chromomagnetic moment for the top,
$\kappa$, on the characteristics of $t\bar t$ production at the Tevatron and on
the spectrum of gluon radiation associated with $t\bar t$ production at the
NLC. In particular, we analyze the sensitivity of future data to non-zero
values of $\kappa$ and estimate the limits that can be placed on this parameter
at the Tevatron and at the NLC with center of mass energies of $\sqrt {s}=$ 500
and 1000 GeV. Constraints on $\kappa$ from low energy processes, such as
$b\rightarrow s\gamma$, are briefly discussed.


title:
Extending the Kinematic Range for $W_R$ Searches in $e^-e^-$ Collisions
  at the NLC

abstract:
  While the much discussed lepton-number violating process $e^-e^-\rightarrow
W_R^-W_R^-$ provides an excellent probe of both the Majorana nature of the
right-handed neutrino and the symmetry breaking sector of the Left-Right
Symmetric Model, it is likely that $W_R$'s are too massive to be pair produced
at the NLC with $\sqrt {s}$ in the 1-1.5 TeV range. We are thus lead to
consider the single $W_R$ production process $e^-e^-\rightarrow W_R^-(W_R^-)^*
\rightarrow W_R^-+jj$ in order to expand the collider's kinematic reach. After
pointing out that $W_R$'s with masses of order 1 TeV may be missed by future
hadron collider searches, we demonstrate that this three-body process possesses
a significant cross section, of order several fb, at the NLC with $\sqrt {s}$
in the range above. The angular distribution of the produced $W_R$'s is shown
to be essentially flat and the potential backgrounds from standard model
processes are shown to be small.


title: Dynamics of Chiral Symmetry Breaking in Nuclear Collisions

abstract:
  Measurements of disoriented chiral condensates in heavy ion collisions at
RHIC and the LHC can yield fundamental information on the nature of the QCD
phase transition. I review theoretical efforts to understand the evolution of
the condensate and present new results on experimental signals in the single
pion spectrum and in pion interferometry. (Invited talk at the Third
International Workshop on Relativistic Aspects of Nuclear Physics, Rio de
Janeiro.)


title: Baryogenesis in Brief

abstract:
  In this talk I briefly review the main ideas and challenges involved in the
computation of the baryon asymmetry of the Universe. (Invited talk given at
``The Birth of the Universe and Fundamental Physics'', Rome, May 18--21, 1994.)


title: Hadronic $Z\gamma$ Production with QCD Corrections and Leptonic Decays

abstract:
  The process $p p \to Z \gamma + X \to \ell^- \ell^+ \gamma + X$, where $\ell$
denotes a lepton, is calculated to order $\alpha_s$. Total and differential
cross sections, with acceptance cuts imposed on the leptons and photon, are
given for the Tevatron and LHC center of mass energies. In general, invariant
mass and angular distributions are simply scaled up in magnitude by the QCD
radiative corrections, whereas in transverse momentum distributions, the QCD
radiative corrections increase with the transverse momentum.


title:
Scaling Properties of $S$-wave Level Density for Heavy Quarkonium from
  QCD Sum Rules

abstract:
  In the framework of a specific scheme of the QCD sum rules for $S$-wave
levels of the heavy quarkonium, one derives an expression, relating the
energetic density of quarkonium states and universal characteristics in the
heavy quarkonium physics, such as the difference between the masses of a heavy
quark $Q$ and meson $(Q\bar q)$ and the number of heavy quarkonium levels below
the threshold of $(Q\bar Q) \to (Q\bar q) + (\bar Q q)$ decay.


title: Diffractive Dissociation in Deep Inelastic Scattering at HERA

abstract:
  The diffraction dissociation of virtual photons is considered in the
framework of conventional Regge theory. It is shown that the recent HERA data
on large rapidity gap events can be successfully described in terms of the
Pomeron structure function. Using Regge factorization, the latter can be
related to the deuteron structure function. The parameters which relate these
two structure functions are determined from soft hadronic diffraction data. The
size of the shadowing corrections at low x and large Q**2 is also obtained.


title: Masses of $nS$-wave Heavy Quarkonium Levels from QCD Sum Rules

abstract:
  Using a specific scheme of the QCD sum rules, one derives an universal
formula for the mass differences for the $nS$-levels of heavy qiarkonium. This
relation does not depend on the flavours of the heavy quarks, composing the
quarkonium, and it is in a good agreement with the experimental mass values for
the $\psi$- and $\Upsilon$-families.


title:
Experimental Evidence for Simple Relations between Unpolarized and
  Polarized Parton Distributions

abstract:
  The Pauli exclusion principle is advocated for constructing the proton and
neutron deep inelastic structure functions in terms of Fermi-Dirac
distributions that we parametrize with very few parameters. It allows a fair
description of the recent NMC data on $F^p_2(x,Q^2)$ and $F^n_2(x,Q^2)$ at
$Q^2=4 GeV^2$, as well as the CCFR neutrino data at $Q^2=3$ and $5 GeV^2$. We
also make some reasonable and simple assumptions to relate unpolarized and
polarized quark parton distributions and we obtain, with no additional free
parameters, the spin dependent structure functions $xg^p_1(x,Q^2)$ and
$xg^n_1(x,Q^2)$. Using the correct $Q^2$ evolution, we have checked that they
are in excellent agreement with the very recent SMC proton data at $Q^2=10
GeV^2$ and the SLAC neutron data at $Q^2=2 GeV^2$.


title:
Scaling Relation for Leptonic Constants\\ of Higher Excitations in Heavy
  Quarkonium

abstract:
  Using a specific scheme of the QCD sum rules, one derives the relation for
leptonic constants of $nS$-wave heavy qiarkonia, so $f^2_{n_1}/f^2_{n_2}=
n_2/n_1$, that does not depend on the quarkonium content, and it is in a good
agreement with the experimental values of constants for the $\psi$- and
$\Upsilon$-families.


title:
Intrinsic Charm Contribution to $J/\psi$ Plus Open Charm Associated
  Production at High Energies

abstract:
  We present the results of a calculation of the intrinsic charm quark
contribution to $J/\psi$ plus open charm associated production at large
transverse momentum in hadron collisions at high energies.
  It is shown that the value of the cross section for such process and its
energy dependence are significantly determined by the choice of charm quark
distribution function. We find that intrinsic charm contribution to inclusive
$J/\psi$ hadroproduction is about 1\% of the total contribution of all
mechanisms.


title: Vacuum-Induced Quantum Decoherence and the Entropy Puzzle

abstract:
  Or: ``How to generate an ensemble in a single event?'' Following recent work
on entropy in strong interactions, I explain the concept of environment-induced
quantum decoherence in elementary quantum mechanics. The classically chaotic
inverted oscillator becomes partially decoherent already in the environment of
a single other oscillator performing only vacuum fluctuations. One finds
exponential entropy growth in the subsystem with a Lyapunov exponent, which
approaches the classical one for weak coupling.
  Presented at the Workshops on ``Quantum Infrared Physics'', Paris,
  6 - 10.6.94, and ``QCD 94'', Montpellier, 7 - 13.7.94.
  Invited talk at the NATO Adv. Res. Workshop on ``Hot Hadronic Matter'',
  Divonne, 27.6. - 1.7.94. To appear in the Proceedings.


title: Charm Mixing and CP Violation in the Standard Model

abstract:
  The Standard Model predictions for $D^0$-$\bar{D}^0$ mixing and CP violation
in $D$ decays are revised. The emphasis is put on obtaining the order of
magnitude of the effects. In the case of mixing, the different approaches to
the long distance contributions are carefully discussed. The size of CP
asymmetries is discussed in general and some specific calculations are
reviewed. The possibility of using kinematic signals is briefly described.}}


title: A Model Independent Analysis of Solar Neutrino Data

abstract:
  The results of a solar model independent analysis of the existing solar
neutrino data under the assumption of MSW transitions in matter or vacuum
oscillations (in the cases of $\nu_{e}$--$\nu_{\mu}(\nu_{\tau})$ and
$\nu_{e}$--$\nu_{\mathrm{S}}$ mixing) are presented. The analysis was done in
two cases. In the first case no assumptions on the value of the total fluxes of
neutrinos from all reactions has been made. In the second case some boundaries
for the values of the neutrino fluxes, that take into account the predictions
of different standard solar models, are imposed. It is shown that rather large
regions of the parameters $ \Delta m^2 $ and $ \sin^2 2\theta $ are excluded by
the existing data. It is also shown that the astrophysical solution of the
solar neutrino problem can be excluded only in the case in which limitations on
the values of the solar neutrino fluxes are imposed.


title:
Hadronization cross--sections at the chiral phase transition of a quark
  plasma

abstract:
  Hadronization at finite temperature $T$ is discussed in the framework of the
Nambu--Jona-Lasinio model. The differential cross-section for the conversion of
a quark--antiquark pair into two pions to first order in a $1/N_c$ expansion is
calculated as a function of the c.m.~energy $s$ and temperature $T$. In
particular, approaching the temperature $T_c$ of the chiral phase transition,
the hadronization cross-section diverges like $\ln |1-{T\over T_c}|$.


title: Exponentiation of Multiparticle Amplitudes in Scalar Theories

abstract:
  It is argued that the amplitudes of the production of $n$ soft scalar
particles by one or a few energetic ones in theories like $\lambda\phi^4$ has
the exponential form, $A_n\propto\sqrt{n!}\exp[{1\over\lambda}F(\lambda
n,\epsilon)]$, in the regime $\lambda\to 0$, $\lambda n={fixed}$,
$\epsilon={fixed}$, where $\epsilon$ is the typical kinetic energy of outgoing
particles. Existing results support this conjecture. Several new analytical and
numerical results in favor of the exponential behavior of multiparticle
amplitudes are presented.


title: On Destabilizing Divergences in Supergravity Models

abstract:
  We show that, for standard N=1 supergravity coupled to chiral matter, if the
Kahler potential has no terms linear in chiral superfields then none are
generated through quad. div. one--loop corrections. If however <V>=0 and susy
is spontaneously broken, linear terms are present and new linear terms may be
generated due to nonrenormalizable couplings in K. These can potentially
destabilize the weak-scale hierarchy.


title: Abelian Action for Quark Confinement: A Direct Evaluation

abstract:
  We evaluate S_{APQCD}, the Abelian projection QCD(APQCD) action
nonperturbatively on the lattice. For SU(2), we find S_{APQCD} at strong
coupling is essentially the compact QED(CQED) action. At weaker coupling, we
find S_{APQCD} mutates: it gains additional operators, including an exogenous
NEGATIVE magnetic monopole mass shift. As a corollary, since monopoles are
condensed in CQED our results prove (vicariously) that SU(2) monopoles are
condensed. S_{APQCD} for SU(3) has similar behavior.


title: The Applicability of the Equivalence Theorem in $\chi PT$

abstract:
  We have explicitely calculated the tree level elastic scattering cross
sections of two longitudinal gauge bosons, up to four derivatives in the chiral
expansion both with and without using the Equivalence Theorem (ET). The
numerical results show the existence of new and severe restrictions in the ET
energy applicability range, as it was stated in our recent derivation, which we
also review here, of the precise ET version in the Chiral Lagrangian
description of the Standard Model Symmetry Breaking Sector.


title: Stability of Gauge Hierarchy in Einstein Supergravity

abstract:
  In supersymmetric grand unified theories, the gauge hierarchy achieved by a
fine-tuning in the superpotential can be violated in the presence of soft
breaking terms. We examine this problem in Einstein supergravity with
hidden-sector supersymmetry breaking. We show that the hierarchy is preserved
if couplings of the hidden sector to visible-sector fields in the
superpotential satisfy a certain requirement.


title:
Nuclear Broadening of Out-of-Plane Transverse Momentum in Di-Jet
  Production

abstract:
  Recently claimed \cite{dj1,dj2,FC} anomalous nuclear effects in di-jet
production are analyzed in view of multiple interaction of projectile/ejectile
partons in nuclear matter. We derive model--independent relations between
A-dependence of the cross section and nuclear broadening of transverse
momentum. Comparison with the data show that initial/final state interaction of
partons participating in hard process is hard as well. This is a solid argument
in favor of smallness of a color neutralization radius of a hadronizing highly
virtual quark.


title:
QCD Interconnection Effects \\ in Hadronic $W^+W^-$ and $t\bar{t}$
  Events

abstract:
  In the events of the type $e^+e^- \rightarrow W^+W^- \rightarrow$ 4 jets,
$e^+e^- \rightarrow t\bar{t} \rightarrow bW^+\bar{b}W^-$, particle production
could depend in a non-trivial way on the kinematics of the process. It is shown
that QCD interference effects are negligible for energetic perturbative
emission, but soft perturbative gluons and non-perturbative fragmentation could
induce colour correlations. Possible consequences for LEP 2 and NLC events are
briefly addressed.


title: Vector and pseudoscalar charm meson radiative decays

abstract:
  Combining heavy quark effective theory and the chiral Lagrangian approach we
investigate radiative decays of pseudoscalar $D$ mesons. We first reanalyse
$D^{*} \rightarrow D \gamma$ decays within the effective Lagrangian approach
using heavy quark spin symmetry, chiral symmetry Lagrangian, but including also
the light vector mesons. We then investigate $D \rightarrow V \gamma$ decays
and calculate the $D^0 \rightarrow \bar{K}^{*0} \gamma$ and $D^{s+} \rightarrow
\rho^+ \gamma$ partial widths and branching ratios.


title:
The Lightest Higgs Boson Mass in the Minimal Supersymmetric Standard
  Model

abstract:
  We compute the upper bound on the mass of the lightest Higgs boson in the
Minimal Supersymmetric Standard Model in a model-independent way, including
leading (one-loop) and next-to-leading order (two-loop) radiative corrections.
We find that (contrary to some recent claims) the two-loop corrections are
negative with respect to the one-loop result and relatively small ($\simlt
3$\%). After defining physical (pole) top quark mass $M_t$, by including QCD
self-energies, and physical Higgs mass $M_H$, by including the electroweak
self-energies $\Pi\left(M_H^2\right)-\Pi(0)$, we obtain the upper limit on
$M_H$ as a function of supersymmetric parameters. We include as supersymmetric
parameters the scale of supersymmetry breaking $M_S$, the value of $\tan \beta$
and the mixing between stops $X_t= A_t + \mu \cot\beta$ (which is responsible
for the threshold correction on the Higgs quartic coupling). Our results do not
depend on further details of the supersymmetric model. In particular, for
$M_S\leq 1$ TeV, maximal threshold effect $X_t^2=6M_S^2$ and any value of
$\tan\beta$, we find $M_H\leq 140$ GeV for $M_t\leq 190$ GeV. In the particular
scenario where the top is in its infrared fixed point we find $M_H\leq 86$ GeV
for $M_t = 170$ GeV.


title: J/psi+gamma Production at the Tevatron Energy

abstract:
  We study the process $\bar p p \rightarrow J/\psi + \gamma +X$ at the
Tevatron energy ($\sqrt{s} = 1.8$~TeV). The perturbative QCD contributions to
this process from the gluon-fusion and the fragmentation mechanisms are
computed. For the entire range of $p_T$ that can be probed at the Tevatron, the
fusion contribution is found to be dominant. Consequently the QCD prediction
for this process has better precision than the purely hadronic production of
$J/\psi$. An experimental study of this process at the Tevatron will help to
clarify several aspects of quarkonium production at large $p_T$.


title: Constraints on Massive Tau Neutrinos and their Cosmological Implications

abstract:
  We point out the following astrophysical consequences of a tau neutrino with
mass in the MeV range:
  (i) if it has a small electric charge which will allow it to become a cold
dark matter of the universe, then present limits on the 511 KeV gamma ray line
rule out the possibility that it contributes an $\Omega_{\nu_{\tau}}$ between
.1 to 1 making it unsuitable as a cold dark matter candidate;
  (ii) if an electrically neutral MeV range $\nu_{\tau}$ decays to $\nu_e +
\chi$ ( where $\chi$ is a massless boson) , then its lifetime is bounded by
SN1987A observations to be within a window $.05~~sec.\leq \tau(\nu_{\tau})~\leq
300~sec./(m_{\nu_{\tau}}~in~ MeV)$ a range which may be of interest from the
point of view of structure formation.
  Encouraged by the overlap between the range allowed in (ii) above and that
required for a proposed structure formation mechanism by Dodelson et al., we
search for simple extensions of the standard model, where such masses and
lifetimes may arise for natural values of parameters and show that the already
existing singlet majoron and low scale left-right models have this property. We
also comment on possible familon models for this decay.


title: Soft Supersymmetry Breaking from Gaugino Condensation

abstract:
  We study the structure of soft breaking terms in the context of a gaugino
condensation scenario. Assuming that the Supergravity Lagrangian is the correct
quantum field theory limit, at some momentum scale $\mu_{UV}$, of a more
fundamental one, we demonstrate that the correct result is obtained simply by
substituting, in the tree level Supergravity Lagrangian, $\lambda \lambda$ (the
gaugino condensate) by its vacuum expectation value $\Lambda^3$. In string
inspired scenarios this implies, in particular, that the scalar masses are
vanishing at the string tree-level and receive a contribution, at the one loop
level, which is proportional to the Green Schwarz coefficient $\delta_{GS}$.
Our results do not agree with the ones obtained in the effective Lagrangian
approach. We study in detail the origin of this discrepancy, and we argue that
the use of the supertrace anomaly to determine the effective theory for the
condensate does not fix its gravitational interactions, leaving the soft
breaking terms and the vacua of the theory unspecified.


title:
Four Weak Gauge Boson Production at Photon Linear Collider and Heavy
  Higgs Signal

abstract:
  We study the signals and backgrounds for a heavy Higgs boson in the processes
$\gamma\gamma\to WWWW$, $\gamma\gamma\to WWZZ$ at the photon linear collider.
The results are based on the complete tree level SM calculation for these
reactions. We show that the invariant mass spectrum of central $WW$, $ZZ$ pairs
is sensitive to the signal from Higgs boson with a mass up to 1~TeV at a 2~TeV
linear collider for integrated luminosity of 300~fb$^{-1}$. At 1.5~TeV PLC
Higgs boson with a mass up to 700~GeV can be studied. The nonresonant
longitudinal gauge boson scattering ($m_H=\infty$) can be detected in
photon-photon collisions at $e^+e^-$ center-of-mass energy of 3~TeV.


title:
Cancellation of Renormalon Ambiguities in the Heavy Quark Effective
  Theory

abstract:
  Recently, it has been shown that the concept of the pole mass of a heavy
quark becomes ambiguous beyond perturbation theory, because of the presence of
infrared renormalons. We argue that the predictions of heavy quark effective
theory, whose construction is based on the pole mass, are free of such
ambiguities. In the $1/m_Q$ expansion of physical quantities, infrared and
ultraviolet renormalons compensate each other between coefficient functions and
matrix elements. We trace the appearance of these compensations for
current-induced exclusive heavy-to-heavy and heavy-to-light transitions, and
for inclusive decays of heavy hadrons. In particular, we show that the
structure of the heavy quark expansion is not obscured by renormalons, and none
of the predictions of heavy quark effective theory are invalidated.


title: Bounds on Dirac Neutrino Masses from Nucleosynthesis

abstract:
  We derive new bounds on the Dirac mass of the tau and muonic neutrinos. By
solving the kinetic equation for the rate of energy deposition due to helicity
flipping processes and imposing the constraint that the number of effective
species contributing to the energy density at the time of nucleosynthesis be
$\Delta k_\nu<~0.3$, we find the bounds $m_{\nu_\mu} < ~150$ KeV and
$m_{\nu_\tau} < ~190$ KeV for $T_{\rm QCD}= 200$ MeV. The constraint $\Delta
k_\nu~<0.1~$ leads to the much stronger bound $m_\nu <10$ KeV for both species
of neutrinos.


title: Inside the Quarks

abstract:
  We build a model which is based on the assumption that the {\bf c} and {\bf
s,b} quarks are excited states of {\bf u} and {\bf d} quarks. This model
predicts the non-existence of the {\bf top} quark and estimates the size of the
quarks to be of order $10^{-7}$ fm.


title:
Analysis of the anomalous events $e^{+}\,e^{-}\,\rightarrow\, l^{+}\,
  \l^{-}\,\gamma\,\gamma$

abstract:
  The $e^{+}\,e^{-}\,\rightarrow\,l^{+}\, \l^{-}\,\gamma\,\gamma$ anomalous
events, regis\-te\-red at $L3$ de\-tec\-tor at $e^+ e^-$ $CERN-LEP$ collider
have been analysed. It has been shown that the interpretation of such events as
a manifestation of scalar (pseudoscalar) resonance with the mass of 60 GeV
contradicts other experimental data.


title:
Nontriviality of Gauge-Higgs-Yukawa System and Renormalizability of
  Gauged NJL Model

abstract:
  In the leading order of a modified 1/Nc expansion, we show that a class of
gauge-Higgs-Yukawa systems in four dimensions give non-trivial and well-defined
theories in the continuum limit. The renormalized Yukawa coupling y and the
quartic scalar coupling \lambda have to lie on a certain line in the
(y,\lambda) plane and the line terminates at an upper bound. The gauged
Nambu--Jona-Lasinio (NJL) model in the limit of its ultraviolet cutoff going to
infinity, is shown to become equivalent to the gauge-Higgs-Yukawa system with
the coupling constants just on that terminating point. This proves the
renormalizability of the gauged NJL model in four dimensions. The effective
potential for the gauged NJL model is calculated by using renormalization group
technique and confirmed to be consistent with the previous result by Kondo,
Tanabashi and Yamawaki obtained by the ladder Schwinger-Dyson equation.


title: Diffractive production of dijets at HERA

abstract:
  We investigate the production of a quark-antiquark pair in diffractive
photon- proton scattering, approximating soft pomeron exchange by the exchange
of two nonperturbative gluons. In deep inelastic scattering at HERA, events
with two jets and the scattered proton in the final state are predicted to be
observa- ble, with an important contribution from charm production. For
photoproduction of light quark jets with high transverse momentum we find that
both exchanged gluons must have a large invariant mass, so that the cross
section is very small, whereas for charm quarks it is quite appreciable. From
our calculation we also extract the quark structure function of the pomeron for
the scaling variable $z$ no too close to 0 or 1, finding a strong flavour
dependence and a behaviour somewhat harder than $z (1-z)$ for light quarks.


title:
Implications of factorization for the determination of hadronic form
  factors in $D_s^+ \ra \phi $ transition

abstract:
  Using factorization we determine the allowed domains of the ratios of form
factors, $x = A_2(0)/A_1(0)$ and $y = V(0)/A_1(0)$, from the experimentally
measured ratio $R_h \equiv \Gamma(D_s^+ \ra \phi \rho^+)/\Gamma(D_s^+ \ra \phi
\pi^+)$ assuming three different scenarios for the $q^2$-dependence of the form
factors. We find that the allowed domains overlap with those obtained by using
the experimentally measured ratio $R_{s\ell} = \Gamma(D^+_s \ra \phi \ell^+
\nu_{\ell})/\Gamma(D^+_s \ra \phi \pi^+)$ provided that the phenomenological
parameter $a_1$ is $1.23$. Such a comparison presents a genuine test of
factorization. We calculate the longitudinal polarization fraction,
$\Gamma_L/\Gamma \equiv \Gamma(D_s^+ \ra \phi_L \rho^+_L)/\Gamma(D_s^+ \ra \phi
\rho^+)$, in the three scenarios for the $q^2$-dependence of the form factors
and emphasize the importance of measuring $\Gamma_L/\Gamma $. Finally we
discuss the $q^2$-distribution of the semileptonic decay and find that it is
rather insensitive to the scenarios for the $q^2$-dependence of the form
factors, and unless very accurate data can be obtained it is unlikely to
discriminate between the different scenarios. Useful information on the value
of $x$ might be obtained by the magnitude of the $q^2$-distribution near $q^2 =
0$. However the most precise information on $x$ and $y$ would come from the
knowledge of the longitudinal and left-right transverse polarizations of the
final vector mesons in hadronic and/or semileptonic decays.


title: Experiments to Find or Exclude a Long-Lived, Light Gluino

abstract:
  Gluinos in the mass range ~1 1/2 - 3 1/2 GeV are absolutely excluded. Lighter
gluinos are allowed, except for certain ranges of lifetime. Only small parts of
the mass-lifetime parameter space are excluded for larger masses unless the
lifetime is shorter than ~ 2 10^{-11} (m_{gluino}/ GeV) sec. Refined mass and
lifetime estimates for R-hadrons are given, present direct and indirect
experimental constraints are reviewed, and experiments to find or definitively
exclude these possibilities are suggested.


title:
Chiral Sum-Rules for ${\cal L}^{WZ}_{(6)}$ Parameters and Application to
  $\pi^0,\eta,\eta'$ Decays

abstract:
  The chiral expansion of the low energy processes $\pi^0\to\gamma\gamma$ and
$\eta\to\gamma\gamma$ is reconsidered with particular emphasis on the question
of the evaluation of the two low-energy parameters from ${\cal L}^{WZ}_{(6)}$
which are involved at chiral order six. It is shown how extensive use of
sum-rules and saturation with resonances as well as constraints from asymptotic
QCD effectively determine their values. Predictions for the widths are
presented for both standard and non-standard values of the quark mass ratio
$m_s/{\hat m}$. A precise relation is established between the usual
phenomenological $\eta-\eta'$ mixing parameters and those of the chiral
expansion. The large size of the chiral correction to the $\eta$ decay can be
understood on the basis of a simple counting rule: $O(1/N_c)\sim\ O(m_q)$. It
is shown how this counting rule eventually allows one to include the $\eta'$
into the effective lagrangian in a consistent and systematic way.


title: Standard Model Baryogenesis

abstract:
  Simply on CP arguments, we argue against a Standard Model explanation of
baryogenesis via the charge transport mechanism. A CP-asymmetry is found in the
reflection coefficients of quarks hitting the electroweak phase boundary
created during a first order phase transition. The problem is analyzed both in
an academic zero temperature case and in the realistic finite temperature one.
At finite temperature, a crucial role is played by the damping rate of
quasi-quarks in a hot plasma, which induces loss of spatial coherence and
suppresses reflection on the boundary even at tree-level. The resulting baryon
asymmetry is many orders of magnitude below what observation requires. We
comment as well on related works.


title:
Electroweak Symmetry Breaking with Non-Universal Scalar Soft Terms and
  Large $\tan\beta$ Solutions

abstract:
  We discuss radiative electroweak symmetry breaking with non-universal scalar
masses at the GUT scale. Large $\tan\beta$ solutions are investigated in detail
and it is shown that qualitatively new (as compared to the universal case)
solutions exist, with much less correlation between soft terms. We identify two
classes of non-universalities which give solutions with $A_o\simeq B_o\simeq
M_{1/2}\simeq O(M_Z)$, $\mu \simeq O(0.5 m_o)$, $m_o>>M_Z$ and $A_o\simeq
B_o\simeq M_{1/2} \simeq\mu\simeq O(M_Z)$, $m_o\ge M_Z$, respectively. In each
case, after imposing gauge and Yukawa coupling unification, we discuss the
predictions for $m_t$, $m_b$ and the spectrum of supersymmetric particles. One
striking consequence is the possibility of light charginos and neutralinos
which in the second option can be higgsino-like. Cosmological constraint on the
relic abundance of the lightest neutralino is also included.


title: HBT Correlators -- Current Formalism vs. Wigner Function Formulation

abstract:
  We clarify the relationship between the current formalism developed by
Gyulassy, Kaufmann and Wilson and the Wigner function formulation suggested by
Pratt for the 2-particle correlator in Hanbury-Brown Twiss interferometry. When
applied to a hydrodynamical description of the source with a sharp freeze-out
hypersurface, our results remove a slight error in the prescription given by
Makhlin and Sinyukov which has led to confusion in the literature.


title:
Determination of the CP Violating Phase $\gamma$ by a Sum Over Common
  Decay Modes to $B_s$ and $\bar{B}_s$

abstract:
  To help the difficult determination of the angle $\gamma$ of the unitarity
triangle, Aleksan, Dunietz and Kayser have proposed the modes of the type
$K^-D^+_s$, common to $B_s$ and $\bar{B}_s$. We point out that it is possible
to gain in statistics by a sum over all modes with ground state mesons in the
final state, i.e. $K^-D^+_s$, $K^{*-}D_+^s$, $K^-D^{*+}_s$, $K^{*-}D^{*+}_s$.
The delicate point is the relative phase of these different contributions to
the dilution factor $D$ of the time-dependent asymmetry. Each contribution to
$D$ is proportional to a product $F^{cb}$ $F^{ub}$ $f_{D_s}$ $f_K$ where $F$
denotes form factors and $f$ decay constants. Within a definite phase
convention, lattice calculations do not show any change in sign when
extrapolating to light quarks the form factors and decay constants. Then, we
can show that all modes contribute constructively to the dilution factor,
except the $P$-wave $K^{*-}D^{*+}_s$, which is small. Quark model arguments
based on wave function overlaps also confirm this stability in sign. By summing
over all these modes we find a gain of a factor 6 in statistics relatively to
$K^-D^+_s$. The dilution factor for the sum $D_{tot}$ is remarkably stable for
theoretical schemes that are not in very strong conflict with data on $B \to
\psi K(K^*)$ or extrapolated from semileptonic charm form factors, giving
$D_{tot} \geq 0.6$, always close to $D(K^- D^+_s)$.


title: Renormalons in Effective Field Theories

abstract:
  We investigate the high-order behavior of perturbative matching conditions in
effective field theories. These series are typically badly divergent, and are
not Borel summable due to infrared and ultraviolet renormalons which introduce
ambiguities in defining the sum of the series. We argue that, when treated
consistently, there is no physical significance to these ambiguities. Although
nonperturbative matrix elements and matching conditions are in general
ambiguous, the ambiguity in any physical observable is always higher order in
$1/M$ than the theory has been defined. We discuss the implications for the
recently noticed infrared renormalon in the pole mass of a heavy quark. We show
that a ratio of form factors in exclusive $\Lambda_b$ decays (which is related
to the pole mass) is free from renormalon ambiguities regardless of the mass
used as the expansion parameter of HQET. The renormalon ambiguities also cancel
in inclusive heavy hadron decays. Finally, we demonstrate the cancellation of
renormalons in a four-Fermi effective theory obtained by integrating out a
heavy colored scalar.


title: Constraining Anomalous Top Quark Couplings at the Tevatron

abstract:
  We explore the influence of an anomalous chromomagnetic moment, $\kappa$,
onthe production characteristics of top quark pairs at the Tevatron. We find
that for top quarks in the 170 GeV mass range, present searches are probing
values of $\kappa$ of order ${1 \over 3}$. For $\kappa$'s in this range we find
that significant enhancements in the both the $q \bar q,~gg \to t \bar t$
production cross sections are obtained. Once top has been verified and QCD
uncertainties are under control, future high statistics measurements at the
Tevatron will eventually be sensitive to values of $\kappa$ with magnitudes
smaller than 0.10-0.15. We discuss a class of scalar technicolor models which
may produce large values of $\kappa$ in conjunction with generation of $m_t$.


title: Calculation of Z Plus Four Jet Production at the Tevatron

abstract:
  We present the first calculation of $Z+4$ jet production with heavy quark
flavor identification at the Tevatron $p\bar p$ collider. The $Z + 4$ jet
channel is especially interesting as a normalizer for the $W +4$ jet background
to top quark signals, as a background to a possible $t\to cZ$ flavor-changing
neutral-current (FCNC) decay signal, and as a background to missing-$p_T$
signals from gluino pairs. We also calculate the contributions to $W+4$ jet
production from all the different heavy-flavor final states. The MADGRAPH
program is used to generate all leading order subprocess helicity amplitudes.
We present Monte Carlo results with separation and acceptance criteria suitable
for the Tevatron experimental analyses. The dependence of the cross sections on
experimental cuts and the theoretical ambiguities due to the scale dependence
are discussed. The predicted ($W+4$ jet)/($Z+4$ jet) ratio is insensitive to
most of these choices.


title: Quantum Mechanics and Linearized Gravitational Waves

abstract:
  The interaction of classical gravitational waves (GW) with matter is studied
within a quantum mechanical framework. The classical equations of motion in the
long wave-length limit is quantized and a Schroedinger equation for the
interaction of GW with matter is proposed. Due to its quadrapole nature, the GW
interacts with matter by producing squeezed quantum states. The resultant
hamiltonian is quite different from one would expect from general principles,
however. The interaction of GW with the free particle, the harmonic oscillator
and the hydrogen atom is then studied using this hamiltonian.


title: Electroweak Baryogenesis and the Phase Transition Dynamics

abstract:
  The baryogenesis is reanalyzed based on the model by A.G.Cohen et al., in
which the lepton number, generated by the neutrinos' scattering from the bubble
walls appearing in the development of the electroweak phase transition, is
converted to the baryon number excess through the sphaleron transition. A
formula obtained in this paper on the lepton number production rate is correct
for the both thin and thick walls within the linear approximation.
Investigation on the time-development of the first order phase transition is
simulated, including the temporal change of the wall velocity as well as the
fusion effect of the bubbles. The details of such phase transition dynamics are
found to affect considerably the final value of the baryon number excess.


title:
Combined constraints on the SUSY parameter space from $\Delta r$ ~and
  Higgs boson search

abstract:
  Combining the constraints coming from the ~$M_W$ ~measurements and the
unsuccesful search for the Higgs boson at LEP we determine in the framework of
MSSM the allowed mass regions for the lighter scalar partner of the top quark.
For a heavy top quark particularily strong bounds are obtained for low values
of ~$\tan\beta\equiv v_2/v_1$ ~and light bottom squark.


title:
Matching to all orders and power corrections in heavy quark effective
  theory

abstract:
  This talk reports on various aspects of the divergence of perturbative
expansions in the context of matching QCD onto heavy quark effective theory.
Implications for exclusive and inclusive decays of heavy mesons are discussed.


title: Electromagnetic pion form factor at finite temperature

abstract:
  The electromagnetic form factor of the pion in the space-like region, and at
finite temperature, $F_{\pi}(Q^{2},T)$, is obtained from a QCD Finite Energy
Sum Rule. The form factor decreases with increasing T, and vanishes at some
critical temperature, where the pion radius diverges. This divergence may be
interpreted as a signal for quark deconfinement.


title: Probing the Photon Structure Function in Photoproduction

abstract:
  We show how the parton distributions in the photon can be accurately measured
in the photoproduction of large-pt jets at HERA. A short review is given of the
beyond Leading Logarithm formalism for the photon structure function, with a
discussion of the factorization scheme and of the non-perturbative input.


title: Searching for $G^3$ in $t \tbar$ Production

abstract:
  The triple gluon field strength operator $G^3$ represents the only genuinely
gluonic CP conserving term which can appear at dimension-6 within an effective
strong interaction Lagrangian. Previous studies of this operator have revealed
that its effect on gluon scattering is surprisingly difficult to detect. In
this article, we analyze the impact of $G^3$ upon top quark pair production. We
find that it will generate observable cross section deviations from QCD at the
LHC for even relatively small values of its coefficient. Furthermore, $G^3$
affects the transverse momentum distribution of the produced top quarks more
strongly at high energies than dimension-6 four-quark and chromomagnetic moment
terms in the effective Lagrangian. Top-antitop production at the LHC will
therefore provide a sensitive and clean probe for the elusive triple gluon
field strength operator.


title:
A new cross term in the two-particle Hanbury-Brown-Twiss correlation
  function

abstract:
  Using two specific models and a model-independent formalism, we show that in
addition to the usual quadratic ``side'', ``out'' and ``longitudinal'' terms, a
previously neglected ``out-longitudinal'' cross term arises naturally in the
exponent of the two-particle correlator. Since its effects can be easily
observed, such a term should be included in any experimental fits to
correlation data. We also suggest a method of organizing correlation data using
rapidity rather than longitudinal momentum differences since in the former
every relevant quantity is longitudinally boost invariant.


title: Astrophysical Implications of Neutrino Mass and Mixings

abstract:
  Astrophysical implications of neutrino mass and mixings are discussed. The
status of solar and atmospheric neutrino problems, and recent developments
concerning nuclear physics input to solar models and solar opacities are
reviewed. Implications of neutrino mass and mixings in supernova dynamics are
explored. The effects of supernova density fluctuations in neutrino propagation
is described.


title:
Hadronic screening masses and the magnetic gluon condensate at high
  temperature

abstract:
  The hadronic screening mass at high temperature ($T$) in QCD$_4$ is examined
on the basis of the QCD sum rules in (2+1) dimensions. Due to the magnetic
gluon condensate at high $T$ which is expected to be nonvanishing, the
screening mass deviates from the asymptotic value $2\pi T$. Also, the screening
mass in the vector (pseudo-vector) channel turns out to be heavier than that in
the scalar (pseudo-scalar) channel.


title:
First-order Phase Transition in Three-dimensional QED with Chern--Simons
  Term

abstract:
  We have studied the chiral phase transition in three-dimensional QED in the
presence of a Chern--Simons term for the gauge field. There exists a phase
where the chiral symmetry is broken dynamically and we have determined the
critical line for this symmetry breaking as a function of the effective
coupling and the strength of the additional Chern--Simons term. In the presence
of a Chern--Simons term, the chiral phase transition turns out to be first
order, in sharp contrast to the phase transition in pure three-dimensional QED.


title: Supersymmetry Breaking by Hidden Matter Condensation in Superstrings

abstract:
  We show that supersymmetry can be broken mainly by hidden matter condensates
in the observable matter direction in generic superstring models. This happens
only when the fields whose VEVs give masses to hidden matter do not decouple at
the condensation scale. We find how the parameters of the string model and the
vacuum determine whether supersymmetry is broken mainly by hidden matter or
gaugino condensates and in the matter or moduli directions.


title: The QCD String with Quarks. II. Light Cone Hamiltonian

abstract:
  The light-cone Hamiltonian is derived from the general gauge -- and Lorentz
-- invariant expression for the $q\bar{q}$ Green's function, containing
confinement via the area law for the Wilson loop.The resulting Hamiltonian
contains in a nonadditive way contributions from quark and string degrees of
freedom. Different limiting dynamical regimes of the system of quarks connected
by the string are found. In the limit of no transverse motion one recovers the
t'Hooft's 1+1 QCD Hamiltonian. The correspondence with the rest frame
Hamiltonian spectrum is established. The important notion of the light-cone
string, contributing significantly to the energy--momentum is discussed.


title: Towards a Model-Independent Analysis of Rare $B$ Decays

abstract:
  Motivated by the experimental accessibility of rare $B$ decays in the ongoing
and planned experiments, we propose to undertake a model-independent analysis
of the inclusive decay rates and distributions in the processes \bgamaxs~ and
\Bsell ~($B=B^\pm$ or $B^0_d$). We show how measurements of the decay rates and
distributions in these processes would allow us to extract the magnitude and
sign of the dominant Wilson coefficients of the magnetic moment operator $\mb
\bar{s}_L \sigma_{\mu \nu} b_R F^{\mu \nu }$ and the four-fermion operators
$(\bar{s}_L \gamma_\mu b_L)(\bar{\ell} \gamma^{\mu} \ell)$ and $(\bar{s}_L
\gamma_\mu b_L)(\bar{\ell} \gamma^{\mu}\gamma^5 \ell)$. Non-standard-model
effects could thus manifest themselves at low energy in rare $B$ decays through
the Wilson coefficient having values distinctly different from their
standard-model counterparts. We illustrate this possibility using the examples
of the two-doublet Higgs models and the minimal supersymmetric models. The
dilepton invariant mass spectrum and the forward-backward asymmetry of $\ell^+$
in the centre-of-mass system of the dilepton pair in the decay \Bsell ~are also
worked out for the standard model and some representative solutions for the
other two models.


title: Dissipation via Particle Production in Scalar Field Theories

abstract:
  The non-equilibrium dynamics of the first stage of the reheating process,
that is dissipation via particle production is studied in scalar field theories
in the unbroken and in the broken symmetry phase. We begin with a perturbative
study to one loop and show explicitly that the mechanism of dissipation via
particle production cannot be explained with a simple derivative term in the
equation of motion. The dissipative contribution is non-local and there does
not exist a local (Markovian) limit at zero temperature. Furthermore, we show
that both an amplitude as well as a one-loop calculation present instabilities,
requiring a non-perturbative resummation. Within the same approximations, we
study an O(2) linear sigma model that allows to study dissipation by Goldstone
bosons.
  We find infrared divergences that require non-perturbative resummation in
order to understand the long-time dynamics. We obtain a perturbative
  Langevin equation that exhibits a generalized fluctuation-dissipation
relation, with non-Markovian kernels and colored noise. We then study a
  Hartree approximation and clearly exhibit dissipative effects related to the
thresholds to particle production. The asymptotic dynamics depends on the
coupling and initial conditions but does not seem to lead to exponential
relaxation. The effect of dissipation by Goldstone bosons is studied
non-perturbatively in the large N limit in an O(N) theory. Dissipation produced
by Goldstone bosons dramatically changes the picture of the phase transition.
We find the remarkable result that for ``slow-roll'' initial conditions (with
the expectation value of the field initially near the origin) the final value
of the expectation value of the scalar field is very close to its initial
value. We find that the minima of the effective action depend on the initial
conditions. We provide extensive numerical analysis of the dynamics.


title:
Critical Analysis of Theoretical Estimates for $B$ to Light Meson Form
  Factors and the $B \to \psi K(K^{\ast})$ Data

abstract:
  We point out that current estimates of form factors fail to explain the
non-leptonic decays $B \to \psi K(K^{\ast})$ and that the combination of data
on the semi-leptonic decays $D \to K(K^{\ast})\ell \nu$ and on the non-leptonic
decays $B \to \psi K(K^{\ast})$ (in particular recent po\-la\-ri\-za\-tion
data) severely constrain the form (normalization and $q^2$ dependence) of the
heavy-to-light meson form factors, if we assume the factorization hypothesis
for the latter. From a simultaneous fit to \bpsi and \dk data we find that
strict heavy quark limit scaling laws do not hold when going from $D$ to $B$
and must have large corrections that make softer the dependence on the masses.
We find that $A_1(q^2)$ should increase slower with \qq than $A_2, V, f_+$.
  We propose a simple parametrization of these corrections based on a quark
model or on an extension of the \hhs laws to the \hl case, complemented with an
approximately constant $A_1(q^2)$. We analyze in the light of these data and
theoretical input various theoretical approaches (lattice calculations, QCD sum
rules, quark models) and point out the origin of the difficulties encountered
by most of these schemes. In particular we check the compatibility of several
quark models with the heavy quark scaling relations.


title: Rigorous QCD-Potential for the $t\bar{t}$-System at Threshold

abstract:
  Recent evidence for the top mass in the region of 160 $GeV$ for the first
time provides an opportunity to use the full power of relativistic quantum
field theoretical methods, available also for weakly bound systems. Because of
the large decay width $\G$ of the top quark individual energy-levels in
"toponium" will be unobservable. However, the potential for the $t\bar{t}$
system, based on a systematic expansion in powers of the strong coupling
constant $\a_s$ can be rigorously derived from QCD and plays a central role in
the threshold region. It is essential that the neglect of nonperturbative
(confining) effects is fully justified here for the first time to a large
accuracy, also just {\it because} of the large $\G$. The different
contributions to that potential are computed from real level corrections near
the bound state poles of the $t\bar{t}$-system which for $\G \ne 0$ move into
the unphysical sheet of the complex energy plane. Thus, in order to obtain the
different contributions to that potential we may use the level corrections at
that (complex) pole. Within the relevant level shifts we especially emphasize
the corrections of order $O(\a_s^4 m_t)$ and numerically comparable ones to
that order also from electroweak interactions which may become important as
well.


title:
Neutralino Mass Bounds in the Next-To-Minimal Supersymmetric Standard
  Model

abstract:
  We analyze the experimental data from the search for new particles at LEP 100
and obtain mass bounds for the neutralinos of the Next--To--Minimal
Supersymmetric Standard Model (NMSSM). We find that for $\tan\beta \gsim 5.5$ a
massless neutralino is still possible, while the lower mass bound for the
second lightest neutralino corresponds approximately to that for the lightest
neutralino in the Minimal Supersymmetric Standard Model (MSSM).


title:
$\epsilon_b$ Constraints on the Minimal $SU(5)$ and $SU(5)\times U(1)$
  Supergravity Models

abstract:
  We have performed a systematic analysis to compute the one-loop electroweak
corrections to the Z->b b-bar vertex in terms of $\epsilon_b$ and $R_b$ in the
context of the minimal $SU(5)$ and no-scale $SU(5)\times U(1)$ supergravity
models. With the measured top mass, $m_t=174\pm 10^{+13}_{-12}$ $\GeV$ ,
recently announced by CDF, we use the latest LEP data on $\epsilon_b$ and $R_b$
($\equiv{\Gamma(Z->b b-bar)/{\Gamma(Z->hadrons)}}$) in order to constrain
further the two models. We find that the present LEP data on $\epsilon_b$ and
$R_b$ constrain the two models rather severely. Especially, the low-$\tan\beta$
region is constrained more severely. $\tan\beta\lsim 2.5$ $(4.0)$ is excluded
by $\epsilon_b$ at $90\%$ C.~L. for $m_t\gsim 170$ $(180)$ $\GeV$ in the
minimal $SU(5)$ (no-scale $SU(5)\times U(1)$) supergravity. Even more stringent
constraint comes from $R_b$. It excludes $\tan\beta\lsim 4.0$ at $90\%$ C.~L.
for $m_t\gsim 160$ $(170)$ $\GeV$ in the minimal $SU(5)$ (no-scale $SU(5)\times
U(1)$) supergravity. We also find that the sign on $\mu$ in the two models can
be determined from $\epsilon_b$ and $R_b$ at $90\%$ C.~L.


title: $K \to \pi\pi\gamma$ decays: a search for novel couplings in kaon decays

abstract:
  We analyze $K \to \pi\pi\gamma$ decays in the framework of Chiral
Perturbation Theory. We study the different Dalitz plot distributions, trying
to find regions where o($p^6$) contributions could be more easily detected. To
fulfill this program we compute all the the o($p^4$) loop and counterterm
contributions, finding a substantial agreement with the existing calculations
and adding some small missing terms in $K_S \to \pi\pi\gamma$.


title: Weak Coupling Limit and Genuine QCD Predictions for Heavy Quarkonia

abstract:
  Although individual levels of toponium will be unobservable, the
top--anti--top system near threshold fulfills all requirements of a rigorous
perturbation theory in QCD for weakly bound systems. Corresponding techniques
from positronium may thus be transferred successfully to this case. After
clarifying the effect of a non-zero width we calculate the $t\bar{t}$ potential
to be used for the calculation of e.g. the cross-sections near threshold.


title: Gauge-Independent Bound-State Corrections to the Toponium Decay Width

abstract:
  Off-shell and relativistic bound-state corrections for the decay $t \to b+W$
are calculated to $O(\a_s^2)$ making full use of the Bethe-Salpeter formalism
for weakly bound systems. Thus we are able to take into account all terms to
that order in a systematic and straightforward manner. One of the previously
not considered contributions cancels precisely gauge dependent terms which
appeared in an earlier off-shell calculation. Important cancellations also
determine the gauge-independent part.


title: Estimation of Power Corrections to Hadronic Event Shapes

abstract:
  Power corrections to hadronic event shapes are estimated using a recently
suggested relationship between perturbative and non-perturbative effects in
QCD. The infrared cutoff dependence of perturbative calculations is related to
non-perturbative contributions with the same dependence on the energy scale
$Q$. Corrections proportional to $1/Q$ are predicted, in agreement with
experiment. An empirical proportionality between the magnitudes of perturbative
and non-perturbative coefficients is noted.


title: Chiral Symmetry Restoration and the Georgi Vector Limit

abstract:
  The chiral phase transition at high temperature and/or density is interpreted
in terms of Georgi's vector limit. We discuss three cases as possible support
for this scenario: Quark-number susceptibility, cool kaons in heavy-ion process
and an instanton-molecule picture for chiral restoration. Both the notion of
``mended symmetry" and the Georgi vector limit are suggested to be relevant in
nuclear physics of dense matter.


title: Just so oscillations in supersymmetric standard model

abstract:
  We analyze the spectrum and mixing among neutrinos in the minimal
supersymmetric standard model with explicit breaking of R parity. It is shown
that ({\em i}) the mixing among neutrinos is naturally large and ({\em ii}) the
non zero neutrino mass is constrained to be $\leq 10^{-5}$ eV from arguments
based on baryogenesis. Thus vacuum oscillations of neutrinos in this model may
offer a solution of the solar neutrino problem. The allowed space of the
supersymmetric parameters consistent with this solution is determined.


title: Regularization in the Gauged Nambu--Jona-Lasinio Model

abstract:
  Various prescriptions employed for regulating gauged Nambu--Jona-Lasinio type
models such as the top-quark condensate model are discussed. The use of
dimensional regularization maintains gauge invariance but destroys the
quadratic divergence in the gap equation. If instead a simple ultraviolet
momentum cutoff is used to regulate loop integrals, then gauge invariance is
destroyed by a quadratically divergent term as well as by ambiguities
associated with arbitrary routing of loop momenta. Finally it is shown that one
can use dispersion relations to regulate the top-quark condensate model. This
prescription maintains gauge invariance and does not depend on arbitrary shifts
in loop momenta.


title: Neutralino Event Rates In Dark Matter Detectors

abstract:
  The expected event rates for ${\tilde Z_{1}}$ dark matter for a variety of
dark matter detectors are studied over the full parameter space with tan
$\beta\leq$ 20 for supergravity grand unified models. Radiative breaking
constraints are implemented and effects of the heavy netural Higgs included as
well as loop corrections to the neutral Higgs sector. The parameter space is
restricted so that the ${\tilde Z_{1}}$ relic density obeys 0.10
$\leq\Omega_{\tilde Z_{1}}h^2\leq 0.35$, consistent with the COBE data and
astronomical determinations of the Hubble constant. It is found that the best
detectors sensitive to coherrent ${\tilde Z_{1}}$ scattering (e.g. Pb) is about
5-10 more sensitive than those based on incoherrent spin dependent scattering
(e.g. CaF). In general, the dark matter detectors are most sensistive to the
large tan $\beta$ and small $m_o$ and $m_{\tilde g}$ sector of the parameter
space.


title: A Proposed Test of Charge Symmetry in $\Sigma$ Decay

abstract:
  The semi-leptonic decays of $\Sigma^\pm$ offer a vehicle for observing charge
symmetry-breaking. The effect is expected to be about 6\%, enhanced due to the
replacement of two u quarks by d quarks. We propose that present experimental
data be improved to search for this effect.


title:
Implications of the Partial Width Z->bb for Supersymmetry Searches and
  Model-Building

abstract:
  Assuming that the actual values of the top quark mass at FNAL and of the
ratio of partial widths Z->bb/Z->hadrons at LEP are within their current
one-sigma reported ranges, we present a No-Lose Theorem for superpartner
searches at LEP II and an upgraded Tevatron. We impose only two theoretical
assumptions: the Lagrangian is that of the Minimal Supersymmetric Standard
Model with arbitrary soft-breaking terms, and all couplings remain perturbative
up to scales of order 10^16 GeV; there are no assumptions about the soft SUSY
breaking parameters, proton decay, cosmology, etc. In particular, if the LEP
and FNAL values hold up and supersymmetry is responsible for the discrepancy
with the SM prediction of the partial width of Z->bb, then we must have
charginos and/or top squarks observable at the upgraded machines. Furthermore,
little deviation from the SM is predicted within "super-unified" SUSY. Finally,
it appears to be extremely difficult to find any unified MSSM model, regardless
of the form of soft SUSY breaking, that can explain the partial width for large
tan(beta); in particular, no model with top-bottom-tau Yukawa coupling
unification appears to be consistent with the experiments.


title: Supersymmetric Contributions to $\BB$ and $\KK$ Mixings

abstract:
  We show that in the supersymmetric standard model (SSM) box diagrams mediated
by charginos and up-type squarks may give large contributions to $\BB$ and
$\KK$ mixings. This is due to the fact that a heavy top quark mass allows large
mass differences among the up-type squarks, which leads to a less efficient
cancellation among the different squark diagrams. If the ratio of the vacuum
expectation values of the Higgs bosons is of order of unity, box diagrams
mediated by charged Higgs bosons also contribute appreciably. For sizable
regions of the SSM parameter space, the SSM contributions could be sufficiently
large to affect significantly the evaluation of the CKM matrix from the
experimental values of the mixing parameter $x_d$ and the $CP$ violation
parameter $\epsilon$.


title: Discrete symmetries and isosinglet quarks in low-energy supersymmetry

abstract:
  Many extensions of the minimal supersymmetric standard model contain
superfields for quarks which are singlets under weak isospin with electric
charge -1/3. We explore the possibility that such isosinglet quarks have low or
intermediate scale masses, but do not mediate rapid proton decay because of a
discrete symmetry. By imposing the discrete gauge anomaly cancellation
conditions, we show that the simplest way to achieve this is to extend the Z_3
"baryon parity" of Ibanez and Ross to the isosinglet quark superfields. This
can be done in three distinct ways. This strategy is not consistent with grand
unification with a simple gauge group, but may find a natural place in
superstring-inspired models, for example. An interesting feature of this
scenario is that proton decay is absolutely forbidden.


title:
The hadronic vacuum polarization contribution to the muon g-2 in the
  quark-resonance model

abstract:
  The hadronic vacuum polarization contribution to the anomalous magnetic
moment of the muon is parametrized by using the quark-resonance model
formulated in \cite{QR}. In this context a recent prediction obtained within
the ENJL model \cite{RAF} can be affected by two additional contributions: the
next to leading corrections in the inverse cutoff expansion and the gluonic
corrections. Motivated by the necessity of reaching a highly accurate
theoretical prediction of the hadronic contribution to the muon g-2, we study
in detail both the effects.


title:
The S parameter in a technicolour model with explicit chiral symmetry
  breaking

abstract:
  We derive the S parameter of the electroweak radiative corrections in a
scaled-QCD technicolour and using a Nambu-Jona Lasinio model for hadronic low
energy interactions. In this framework deviations from low energy QCD can be
quantitatively deduced. We induce explicit chiral symmetry breaking in the NJL
model through the current-quarks mass term. It is shown that the prediction for
the S parameter can be sensitively reduced respect to the chiral prediction.


title: Electromagnetic Pion Form Factor and Neutral Pion Decay Width

abstract:
  The electromagnetic pion form factor, $F_\pi(q^2)$, is calculated for
spacelike-$q^2$ in impulse approximation using a confining quark propagator,
$S$, and a dressed quark-photon vertex, $\Gamma_\mu$, obtained from realistic,
nonperturbative Dyson-Schwinger equation studies. Good agreement with the
available data is obtained for $F_\pi(q^2)$ and other pion observables,
including the decay $\pi^0 \rightarrow \gamma\,\gamma$. This calculation
suggests that soft, nonperturbative contributions dominate $F_\pi(q^2)$ at
presently accessible~$q^2$.


title:
Testing the Vacuum Oscillation and the MSW Solutions of the Solar
  Neutrino Problem

abstract:
  Solar model independent tests of the vacuum oscillation and MSW solutions of
the solar neutrino problem are considered. Detailed predictions for time
(seasonal) variations of the signals in the future solar neutrino detectors
(SNO, Super Kamiokande, BOREXINO, HELLAZ), if solar neutrinos take part in
vacuum oscillations, are given. Results on the distortions of the spectra of
boron neutrinos, and of electrons from the neutrino-electron scattering induced
by boron neutrinos, in the cases of vacuum oscillations or MSW transitions are
presented for a large number of values of the relevant parameters. The
possibilities to distinguish between the vacuum oscillation, the MSW adiabatic,
and the MSW nonadiabatic transitions (solutions) in the future solar neutrino
experiments are discussed.


title: Open Questions in Charm Decays Deserving an Answer

abstract:
  A list is given of those open questions concerning the dynamics of charm
decays where there exists a strong need for an answer. Such a need is based on
lessons to be learnt about QCD -- either in their own right or for a better
understanding of $B$ physics -- or on searches for New Physics with a small
background from the Standard Model. The major items on this list are: lifetimes
of the $\Xi _c^{0,+}$ baryons; semileptonic branching ratios of $D_s$, $\Lambda
_c$ and $\Xi _c$ hadrons and absolute branching ratios for those states;
radiative decays $D\rightarrow \gamma K^*,\, \gamma \rho /\omega , \, D_s
\rightarrow \gamma \phi /\omega ,\, D\rightarrow l^+l^-K/K^*$; $D^0-\bar D^0$
oscillations down to a sensitivity below $10^{-4}$ and CP asymmetries in
non-leptonic $D$ decays down to 0.1\%. Ongoing and already approved experiments
will produce important new insights, which are unlikely to provide sufficient
answers to all these questions yet. It is discussed how a third-generation
fixed-target experiment like CHARM2000 or a $\tau$-charm factory can fill the
bill.


title: Constraints on the Fiite-Density Spectral Densities of Vector Channel

abstract:
  Sum rules for the variation of finite-density spectral density of vector
channel with baryon density are derived based on dispersion relations and the
operator product expansion. These sum rules may serve as constraints on the
phenomenological models for the finite-density spectral densities used in the
approaches motivated from QCD. Applying these sum rules to the rho meson in
nuclear medium with a simple pole-plus-continuum ansatz for the spectral
densities, we found that the qualitative features of the QCD sum-rule
predictions for the spectral parameters are consistent with these sum rules;
however, the quantitative QCD sum-rule results violate the sum rules to certain
degree.


title: Unifiable Supersymmetric Left-Right Model with E_6 Particle Content

abstract:
  A new supersymmetric gauge model is proposed with particle content chosen
only from the 27 and 27* representations of E_6. The gauge symmetry SU(3) X
SU(2)_L X SU(2)_R X U(1) is realized at the TeV energy scale and the gauge
couplings converge to a single value at around 10^{16} GeV. A discrete Z_4 X
Z_2 symmetry leads to a generalized definition of lepton number and ensures the
absence of tree-level flavor-changing neutral-current interactions at the
electroweak energy scale.


title:
Slope of the Isgur-Wise Function from a QSSR Constraint on the $\Upsilon
  B\bar{B}$ Couplings

abstract:
  We derive optimal upper and lower bounds on the slope of the Isgur-Wise
function at the zero recoil point in terms of the sum of the $\Upsilon
B\bar{B}$ couplings, estimated recently from a $QCD$ Spectral Sum Rule
($QSSR$). The problem is solved by means of a duality theorem in functional
optimization. Optimal correlations between the slope and the convexity
parameters of the Isgur-Wise function with the same input are also obtained.


title:
Azimuthal Angle Decorrelation in Large-rapidity Dijet Production at the
  Tevatron

abstract:
  In this talk we examine the azimuthal angle decorrelation in dijet production
at large rapidity intervals at the Tevatron as a possible signature of the BFKL
evolution.


title: Production of Heavy Bound States at LEP and Beyond

abstract:
  We describe some characteristic properties of $B_c$ mesons and discuss the
production and the prospects of detection in $e^+ e^-$, $\gamma \gamma$, and
$\bar pp/pp$ collisions. The production mechanisms considered here also play an
important role in charmonium and bottomonium production.


title: Sphalerons and Strings

abstract:
  This work is based on a paper with Margaret James, to appear in Phys Rev D.
In it we showed that the dipole moment of the sphaleron has its origin in two
components: a ring of electric current circulating around the edge of the
sphaleron; and also two regions of opposite magnetic charge above and below the
ring. This magnetic charge has a partly topological explanation, arising from
the fact that the sphaleron is axisymmetric and parity invariant. Here, I
discuss the definition of the electromagnetic field and its sources in the
Standard Model, comparing the one we use with the better-known one of 't Hooft.
I also discuss the resemblance between the sphaleron and Nambu's ``dumb-bell''
-- a segment of $Z$-string which connects a monopole to an antimonopole.


title: On Hadronic Production of the $B_c$ Meson

abstract:
  Two of the approaches to the hadronic productions of the double heavy mesons
$B_c$ and $B_c^*$ are investigated. Comparison in various aspects on the
results obtained by the approaches is made and shown in figures and a table.
Some trial understanding of the approaches themselves and the achieved results
is presented. The results may be used as some references for discovering the
mesons at Tevatron and LHC.


title: Limit on $Br(b\to s g)$ in Two Higgs Doublet Models

abstract:
  Using the recent CLEO measurement of $Br(b\to s \gamma)$, we find that the
branching ratio of $b\to s g$ cannot be larger than $10\%$ in two Higgs doublet
models. The small experimental value of $Br(b\to e\bar{\nu}X)$ can no longer be
explained by charged Higgs boson effects.


title:
Scalar Mass Bounds in Two Supersymmetric Extended Electroweak Gauge
  Models

abstract:
  In two recently proposed supersymmetric extended electroweak gauge models,
the reduced Higgs sector at the 100-GeV energy scale consists of only two
doublets, but they have quartic scalar couplings different from those of the
minimal supersymmetric standard model. In the SU(2) X SU(2) X U(1) model, there
is an absolute upper bound of about 145 GeV on the mass of the lightest neutral
scalar boson. In the SU(3) X U(1) model, there is only a parameter-dependent
upper bound which formally goes to infinity in a particular limit


title: Unitarity and the BFKL Pomeron

abstract:
  {\narrower\smallskip High Energy onium-onium scattering is calculated as a
function of impact parameter in the one and two pomeron exchange approximation.
Difficulties with using the multiple scattering series to unitarize single
pomeron exchange at high energy are noted. An operator formalsim which sums all
numbers of pomeron exchange is given. A toy model which has a similar operator
structure at high energy as QCD is presented and the S-matrix is evaluated.
Estimates of the energies and impact parameters at which blackness occurs in
onium-onium scattering are given. It is emphased that the problem of unitarity
in high energy onium-onium scattering can be solved in a purely perturbative
context, with a non-running coupling if the onium is heavy enough.\smallskip}


title: Scatttering of Weakly Interacting Massive Particles from Ge73

abstract:
  We use a "hybrid" method, mixing variationally-determined triaxial nuclear
Slater determinants, to calculate the response of Ge73 to hypothetical
dark-matter particles such as neutralinos. The method is a hybrid in that
rotational invariance is approximately restored prior to variation and then
fully restored before the mixing of intrinsic states. We discuss such features
of Ge73 as shape coexistence and triaxiality, and their effects on
spin-dependent neutralino cross sections. Our calculations yield a satisfactory
quadrupole moment and an accurate magnetic moment in this very complicated
nucleus, suggesting that the spin structure and thus the axial--vector response
to dark matter particles is modeled well.


title: Alignment in Gamma-Hadron Families of Cosmic Rays

abstract:
  Alignment of main fluxes of energy in a target plane is found in families of
cosmic ray particles detected in deep lead X-ray chambers. The fraction of
events with alignment is unexpectedly large for families with high energy and
large number of hadrons. This can be considered as evidence for the existence
of coplanar scattering of secondary particles in interaction of particles with
superhigh energy, $E_0 > 10^{16}$ eV. Data analysis suggests that production of
most aligned groups occurs low above the chamber and is characterized by a
coplanar scattering and quasiscaling spectrum of secondaries in the
fragmentation region. The most elaborated hypothesis for explanation of
alignment is related to the quark-gluon string rupture. However, the problem of
theoretical interpretation of our results still remains open.


title:
The Ellis-Jaffe Sum Rule: The Estimates of the Next-to-Next-to-
  Leading-Order QCD Corrections

abstract:
  The procedure of the estimates of the higher-order perturbative QCD
corrections to the physical quantities is generalized to the case when the
quantities under consideration obey the renormalization group equationts with
the corresponding anomalous dimension function. This procedure is used to
estimate the $\alpha_s^3$-corrections to the singlet part of the Ellis-Jaffe
sum rule for $f=3$ numbers of flavours.


title:
Gluon Decay as a Mechanism for Strangeness Production in a Quark-Gluon
  Plasma

abstract:
  A calculation of thermal gluon decay shows that this process contributes
significantly to strangeness production in a quark-gluon plasma. Our analysis
does not support recent claims that this is the dominant process. In our
calculations we take into account the resummed form of the transverse and
longitudinal parts of the gluon propagator following the Braaten-Pisarski
method. Our results are subject to the uncertainty concerning the estimate of
the damping rate entering the effective gluon propagator.


title: Leptoquark Search at $e^+ e^-$ Colliders

abstract:
  We investigate the possibility of detecting a scalar leptoquark, coupling to
the electron and the top, at a linear collider. For coupling strength equalling
the weak coupling constant, the present mass bounds are of the order of 300
GeV. We demonstrate that at the NLC, one could detect such particles if their
mass were less than a few TeV's.


title: Next-to-Leading Corrections at Small X from Quark Evolution

abstract:
  Deep inelastic processes at small x are discussed in the framework of
perturbative QCD at high energy. New results are presented on the quark
anomalous dimensions beyond the leading logarithmic approximation, and their
relevance to the structure functions being measured at HERA is pointed out.
  *Talk given at the XXIX Rencontres de Moriond, 19-26 March 1994, Meribel,
  France, to appear in the Proceedings.


title:
The electroweak chiral parameters for a heavy Higgs in the Standard
  Model

abstract:
  We study the electroweak interactions within the standard electroweak theory
in the case where the Higgs particle is heavy, namely, $M_H \leq 1\;TeV$. By
integrating out the Higgs boson to one loop we find the complete effective
lagrangian, called electroweak chiral lagrangian, that is $SU(2)_L\times
U(1)_Y$ invariant and contains the whole set of operators up to dimension four.
The values of the chiral parameters representing the non-decoupling effects of
the heavy Higgs are presented. Some examples have been chosen to show the
applicability of this effective lagrangian approach to compute
phenomenologically relevant quantities that either are being meassured at
present or will be meassured in future experiments.


title:
Higgs and Supersymmetric Particle Signals at the Infrared Fixed Point of
  the Top Quark Mass

abstract:
  We study the properties of the Higgs and supersymmetric particle spectrum
associated with the infrared fixed point solution of the top quark mass in the
MSSM. We concentrate on the possible detection of these particles, analysing
the deviations from the Standard Model predictions for the leptonic and
hadronic variables measured at LEP and for the decay rate $b\rightarrow
s\gamma$. We consider the low and moderate $\tan \beta$ regime, and we study
both, the cases of universal and non--universal soft supersymmetry breaking
parameters at high energies. In the first case, for any given value of the top
quark mass, the Higgs and sparticle spectra are completely determined as a
function of two soft supersymmetry breaking parameters. In the case of
non--universality, instead, the strong correlations between the sparticle
masses are relaxed, allowing a richer structure for the precision data
variables. We show, however, that the requirement that the low energy theory
proceeds from a grand unified theory with a local symmetry group including
$SU(5)$, strongly constrains the set of possible indirect experimental
signatures. As a general feature, whenever a significant deviation from the
Standard Model value of the precision data variables is predicted, a light
sparticle, visible at LEP2, appears in the spectrum.


title: The Thermal Beta-Function in Yang-Mills Theory

abstract:
  Previous calculations of the thermal beta-function in a hot Yang--Mills gas
at the one--loop level have exposed problems with the gauge dependence and with
the sign, which is opposite to what one would expect for asymptotic freedom. We
show that inclusion of higher--loop effects through a static Braaten--Pisarski
resummation is necessary to consistently obtain the leading term, but alters
the results only quantitatively. The sign, in particular, remains the same. We
also explore, by a crude parameterization, the effects a (non--perturbative)
magnetic mass may have on these results.


title: Dirac Neutrinos and Primordial Magnetic Fields

abstract:
  We consider random primordial magnetic fields and discuss their dissipation,
coherence length $L_0$, scaling behaviour and constraints implied by the
primoridal nucleosynthesis. Such magnetic fields could excite the
right-helicity states of Dirac neutrinos, with adverse consequences for
nucleosynthesis. We present solutions to the spin kinetic equation of a Dirac
neutrino traversing a random magnetic field in the cases of large and small
$L_0$, taking also into account elastic collisions. Depending on the scaling
behaviour and on the magnetic coherence length, the lower limit on the neutrino
magnetic moment thus obtained could be as severe as $10^{-20}\mu_B$.


title: Aspects of Nucleon Chiral Perturbation Theory

abstract:
  I review recent progress made in the calculation of nucleon properties in the
framework of heavy baryon CHPT. Topics include: Compton scattering, $\pi N$
scattering, the anatomy of a low-energy constant and the induced pseudoscalar
form factor.


title:
Time Reversal Odd Fragmentation Functions in Semi-Inclusive Scattering
  of Polarized Leptons from Unpolarized Hadrons

abstract:
  Semi-inclusive deep inelastic scattering of polarized leptons off hadrons
enables one to measure the antisymmetric part of the hadron tensor. For
unpolarized hadrons this piece is odd under time reversal. In deep inelastic
scattering it shows up as a $\langle \sin \phi \rangle$ asymmetry for the
produced hadrons. This asymmetry can be expressed as the product of a
twist-three "hadron $\rightarrow$ quark" distribution function and a time
reversal odd twist-two "quark $\rightarrow$ hadron" fragmentation function.
This fragmentation function can only be measured for nonzero transverse momenta
of the produced hadron.


title: Low x Physics and Perturbative Regge Asymptotics

abstract:
  Deep-inelastic scattering at small x is a new field of QCD phenomenology
which HERA experiments started to explore. The data show the feature expected
by the perturbative Regge asymptotics. We describe the parton picture of
structure function evolution both for increasing $Q^2$ and for decreasing $x$
and discuss the leading logarithmic approximation of QCD on which this picture
is based. The steep rise of the parton density towards smaller $x$ gets
saturated by parton recombination. An essential improvement of the leading
logarithmic approximation has to be worked out in order to satisfy the
unitarity conditions and in this way to describe the parton recombination in
perturbative QCD. We review some ideas of the perturbative Regge asymptotics
and some recent theoretical results about multi-reggeon exchange in QCD. Talk
at the Tennessee Intern. Symposium on Rad. Corrections, prepared for the
proceedings.


title: New Strong Interactions Above the Electroweak Scale

abstract:
  Theoretical arguments for a new higher-color quark sector, based on Pomeron
physics in QCD, are briefly described. The electroweak symmetry-breaking,
Strong CP conservation, and electroweak scale CP violation, that is naturally
produced by this sector is also outlined. A further consequence is that above
the electroweak scale there will be a radical change in the strong interaction.
Electroweak states, in particular multiple $W$'s and $Z$'s, and new,
semi-stable, very massive , baryons, will be commonly produced. The possible
correlation of expected phenomena with a wide range of observed Cosmic Ray
effects at and above the primary spectrum knee is described. Related phenomena
that might be seen in the highest energy hard scattering events at the Fermilab
Tevatron, some of which could be confused with top production, are also briefly
discussed.


title:
A-dependence of nuclear transparency in quasielastic A(e,e'p) at high
  Q^2

abstract:
  The A-dependence of the quasielastic A(e,e'p) reaction has been studied at
SLAC with H-2, C, Fe, and Au nuclei at momentum transfers Q^2 = 1, 3, 5, and
6.8 (GeV/c)^2. We extract the nuclear transparency T(A,Q^2), a measure of the
average probability that the struck proton escapes from the nucleus A without
interaction. Several calculations predict a significant increase in T with
momentum transfer, a phenomenon known as Color Transparency. No significant
rise within errors is seen for any of the nuclei studied.


title: Reggeized Gluons with a Running Coupling Constant

abstract:
  The equation for two reggeized gluons in the vacuum channel is generalized to
take into account the running QCD coupling constant on the basis of the
bootstrap condition for gluon reggeization. Both the gluon trajectory as a
function of momentum and the interaction as a function of distance grow like
$\log\log$ in the ultraviolet. The resulting equation depends on the
confinement region. With a simple parametrization of its influence by an
effective gluon mass the pomeron intercept turns out much smaller than for a
fixed coupling constant (the BFKL pomeron).


title: Nonabelian Debye Screening in One-Loop Resummed Perturbation Theory

abstract:
  Debye screening of static chromoelectric fields at high temperature is
investigated at next-to-leading order through one-loop resummed perturbation
theory. At this order the gluon propagator appears to give rise to strong
deviations from a Yukawa form of screening. Generally, an oscillatory behavior
is found which asymptotically becomes repulsive, but in a gauge-dependent
manner. However, these features are strongly sensitive to the existence of
screening of static magnetic fields. It is shown that a small magnetic
screening mass can restore exponential screening with a gauge independent value
of the screening mass, which depends logarithmically on the magnitude of the
magnetic mass. Recent results obtained in temporal axial gauge, which instead
indicate an asymptotic (repulsive) power-law behavior of screening, are also
critically discussed. In order to arrive at a gauge-invariant treatment of
chromoelectric screening, Polyakov loop correlations are considered, both with
and without dynamical gauge symmetry breaking. Again a crucial sensitivity to
the scale of magnetic screening is found. A detailed comparison of the
perturbative results with recent high-precision lattice simulations of the
SU(2) Polyakov loop correlator is made, which are found to agree well with the
perturbative result in the symmetric phase when a magnetic mass $\sim g^2T/4$
is included.


title: The Infrared Sensitivity of Nonabelian Debye Screening

abstract:
  It is shown that a perturbative treatment of nonabelian Debye screening at
high temperature suffers from infrared problems already at the next-to-leading
order, which is given by ring-resummed one-loop diagrams. Superficial infrared
power counting would let one expect a sensitivity to the magnetic mass scale
only at higher orders, but the form of Debye screening depends on the analytic
structure of the correlation functions, which is strongly sensitive to the
existence of screening of static magnetic fields. [Invited talk at the Workshop
on Quantum Infrared Physics, 6-10 June 1994, American University of Paris,
France]


title: On the Deconfinement Phase Transition in the Resonance Gas

abstract:
  We obtain the constraints on the ruling parameters of the dense hadronic gas
model at the critical temperature and propose the quasiuniversal ratios of the
thermodynamic quantities. The possible appearence of thermodynamical
instability in such a model is discussed.


title:
Multi-Channel Search for Minimal Supergravity at $p\bar p$ and $e^+e^-$
  Colliders

abstract:
  We examine the phenomenology of minimal supergravity models, assuming only
that the low energy theory has the minimal particle content, that electroweak
symmetry is radiatively broken, and that R-parity is essentially conserved.
After delineating regions of supergravity parameter space currently excluded by
direct particle searches at LEP and the Tevatron, we quantify how this search
region will be expanded when LEP~II and the Tevatron Main Injector upgrades
become operational. We describe how various experimental analyses can be
consistently combined within a single framework, resulting in a multi-channel
search for supersymmetry, but note that this analysis is sensitive to specific
assumptions about physics at the unification scale.


title:
Photon Vector Meson Coupling and Vector Meson Properties at Low
  Temperature Pion Gas

abstract:
  The vector and axial vector current mixing phenomena at low temperature pion
gas by Dey, Eletsky and Ioffe, leads to the low temperature correction of the
photon-vector meson coupling ($g_\rho$) at order $\epsilon=T^2/6f_\pi^2$ and
the $\rho$ meson mass at order $\epsilon^2$. We show how this {\it low
temperature theorems} involving the photon and vector mesons are satisfied in
the chiral models based on hidden gauge symmetry and the massive Yang-Mills
approach with an explicit $a_1$ meson. We discuss possible phenomenological
consequences of the low temperature corrections in RHIC experiments.


title: Quantum Inflation?

abstract:
  We consider curved space quantum corrections to the equations of motion of
the inflaton field in the early Universe. Using the stochastic formalism in
phase space, we demonstrate that the quantum corrected evolution of the
inflaton can differ dramatically from its classical evolution when the mass
scales in the potential become large, which is naturally the case in
fundamental theories describing Planck scale physics. Using the example of the
cosine potential, we show that the prolonged, perhaps even eternal,
quantum--inflationary period is expected with a significant probability. This
feature of Planck scale potentials can be dangerous, but it offers also a
possibility of creating the inflationary phase in string or supergravity
models, where no natural realization of inflation has been found so far.


title: Searching for Supersymmetry: A Minireview

abstract:
  After a lightning review of current bounds on the masses of supersymmetric
particles, we describe strategies that may be helpful for extracting signals
from the production of squarks, gluinos or top squarks, and from associated
chargino-neutralino production at the Tevatron. We then briefly review SUSY
signals at hadron and $e^+e^-$ supercolliders. We discuss how various SUSY
signals may be correlated within the supergravity framework and indicate the
sense in which $e^+e^-$ and hadron colliders may be complementary. **Presented
at the Eighth DPF Meeting, Albuquerque, NM, August, 1994**


title:
Complementarity of $e^+e^-$ and $pp$ Colliders for the Exploration of
  Electroweak Symmetry Breaking

abstract:
  I review the physics capabilities of the machines proposed for the next
generation of high-energy experimentation: in hadron physics, the LHC, and in
electron physics, a $500$--$1500$ GeV $e^+e^-$ linear collider. Using for
illustration two specific models of electroweak symmetry breaking, I show how
the $pp$ and $e^+e^-$ techniques are expected to complement one another in the
exploration of the next scale of physics. [invited lecture at the 22nd INS
Symposium, Tokyo] (text only; complete paper with figures and tables available
by anonymous ftp from preprint.slac.stanford.edu, in the directory
pub/preprints/hep-ph/9408)


title: Charm as Probe of New Physics

abstract:
  In this talk I would like to discuss two aspects of charm physics. One is to
show that many standard model predictions for rare decay modes (along with $D^0
-\bar{D}^0$ mixing and CP violation) are extremely small thus opening a window
for new physics effects\cite{1}; and the other is to review the expectations
from several plausible and interesting new physics possibilities.


title: Low Energy Leptogenesis in Left-Right Symmetric Models

abstract:
  We propose a new mechanism for baryogenesis. We study the effective potential
of left-right extension of the standard model and show that there can be a
first order phase transition at the left-right symmetry breaking and hence
$(B-L)$ symmetry breaking scale, which is around TeV in our scenario. As a
result, although $(B-L)$ violating interactions are in equilibrium at this
scale, enough $(B-L)$ asymmetry may be generated. This $(B-L)$ asymmetry is
then converted to baryon asymmetry during the anomalous electroweak process. If
right handed gauge bosons are seen in the TeV scale, then we argue that this
will be the only consistent mechanism to generate baryon asymmetry of the
universe.


title: Unitarity and Fermion Mass Generatation

abstract:
  Some years ago Appelquist and Chanowitz considered the scattering of
fermion--anti-fermion into a pair of longitudinal gauge bosons. Their
calculation established that unitarity implies that the physics giving mass to
a quark of mass $m_f$ must be below a mass scale of $16 \pi v^2 / m_f$ ($v=246$
GeV). This bound is a bit difficult to interpret, because the unitarity of
gauge boson scattering requires in any case that there be new physics, such as
a Higgs boson, with a mass lighter than this. This paper re-examines the
Appelquist-Chanowitz bound in order to clarify its meaning. This work uses toy
models with a singlet Higgs boson to unitarize gauge boson scattering, and
considers other possibilities for the new physics affecting the fermion mass.
This new physics has the effect of changing the Higgs
boson--fermion--anti-fermion coupling. New physics cannot significantly alter
this coupling unless it is substantially lighter than the Appelquist-Chanowitz
bound.


title: Next-to-leading Order Debye Mass for the Quark-gluon Plasma

abstract:
  The Debye screening mass for a quark-gluon plasma at high temperature is
calculated to next-to-leading order in the QCD coupling constant from the
correlator of two Polyakov loops. The result agrees with the screening mass
defined by the location of the pole in the gluon propagator as calculated by
Rebhan. It is logarithmically sensitive to nonperturbative effects associated
with the screening of static chromomagnetic fields.


title: Unifying Logarithmic and Factorial Behavior in High Energy Scattering

abstract:
  The elegant instanton calculus of Lipatov and others used to find
factorially-divergent behavior (g^N * N!) for N*g >> 1 in g*phi^4 perturbation
theory is strictly only applicable when all external momenta vanish; a
description of high-energy 2 --> N scattering with N massive particles is
beyond the scope of such techniques. On the other hand, a standard
multiperipheral treatment of scattering with its emphasis on leading logarithms
gives a reasonable picture of high-energy behavior but does not result in
factorial divergences. Using a straightforward graphical analysis we present a
unified picture of both these phenomena as they occur in the two-particle total
cross section of g*phi^4 theory. We do not attempt to tame the unitarity
violations associated with either multiperipheralism or the Lipatov technique.


title:
Constraints on non-universal soft terms from flavor changing neutral
  currents

abstract:
  The smallness of flavor changing neutral currents constrains the soft
parameter space of supersymmetric extensions of the Standard Model. These low
energy constraints are translated to the soft parameter space generated at some
high energy scale $\Mgut$. For gaugino masses larger than the scalar masses and
non-universal $A$-terms the constraints are significantly diluted at $\Mgut$
and do allow for the possibility of non-universal scalar masses. The strongest
constraints arise in the slepton sector of the theory.


title: The Three-Loop Free Energy for Pure Gauge QCD

abstract:
  We compute the free energy density for pure non-Abelian gauge theory at high
temperature and zero chemical potential. The three-loop result to $O(g^4)$ is
  [a lovely formula. Get the paper and print it out.] We examine the
sensitivity of this result to the choice of renormalization scale. We also give
a result for the free energy of scalar $\phi^4$ theory, correcting a result
previously given in the literature.


title: Recent Results in Neutrino Physics

abstract:
  This is a survey of the current experimental information on some of the
interesting issues in neutrino physics: neutrino species, neutrino masses,
neutrino magnetic moments, solar neutrinos, and the atmospheric neutrino
anomaly.


title: Dynamics of the QCD String with Light and Heavy Quarks

abstract:
  The generalization of the effective action [1] of the quark--antiquark system
in the confining vacuum is performed for the case of arbitrary quark masses.
The interaction of quarks is described by the averaged Wilson loop for which we
use the minimal area law asymptotics.
  The system is quantized by the path integral method and the quantum
Hamiltonian is obtained. It contains not only quark degrees of freedom but also
the string energy density.
  As well as in the equal masses case [1] two dynamical regimes are found [2]:
for large orbital excitations ($l \gg 1$) the system is represented as rotating
string, which leads to asymptotically linear Regge trajectories, while at small
$l$ one obtains a potential-like relativistic or nonrelativistic regime.
  In the limiting cases of light-light and heavy-light mesons a unified
description is developed [2]. For the Regge trajectories one obtains nearly
straight-line patterns with the slope very close to $1/2 \pi \sigma$ and $1/
\pi\sigma$ correspondingly. The upper bound on the light quark(s) masses which
doesn't change considerably this property of the trajectories is also found.


title: Theoretical expectations for the top-quark mass

abstract:
  I review the theoretical expectactions for the top-quark mass in a variety of
models: the Standard Model, unified models (GUTs), low-energy supersymmetric
models (SUSY), unified supersymmetric models (SUSY GUTs), supergravity models,
and superstring models. In all instances I consider the constraints on the
top-quark mass which arise by demanding that these theories be weakly
interacting. This assumption is quantified by the use of partial-wave unitarity
or triviality. The resulting upper bounds on the top-quark mass are most
stringent in SUSY GUTs models ($m^{\rm pole}_t\lsim200\sin\beta\GeV$). I also
discuss a class of $SU(5)\times U(1)$ superstring models where $m^{\rm
pole}_t\sim(170-195)\GeV$ is predicted. I conclude that experimental
determinations of the top-quark mass can be {\em naturally} understood in SUSY
GUTs and superstring models. (Lecture presented at the International School of
Subnuclear Physics, 32nd Course: From Superstring to Present-Day Physics,
Erice--Sicily: July 3--11, 1994.)


title:
Light Stops in the MSSM: Implications for Photino Dark Matter and Top
  Quark Decay

abstract:
  We consider the viability of the minimal supersymmetric standard model with a
light ($m_{\tilde t_1} < $ 45 GeV) stop. In order for its relic abundance to be
cosmologically significant, the photino as dark matter must be quite close in
mass to the stop, $(m_{\tilde t_1} - m_{\tilde \gamma}) \simeq 3 - 7 $ GeV.
However, as we show, the photino despite its low mass is virtually undetectable
by either direct or indirect means. We also discuss the implications of these
masses on the top quark branching ratios.


title: Implications of a Purely Right-Handed Bottom Quark Decay Coupling

abstract:
  We examine the implications of the hypothesis that the decays of the b-quark
occur via pure right-handed couplings. We show that the existing lower limits
on neutrinoless double beta decay imply that any gauge model realizing this
idea must have either an $L_e-L_\mu$ or $L_e-L_\tau$ symmetry. We then show
that constraints of cosmology together with observations from SN1987A imply
that the right-handed neutrinos in this model must be heavier than about 100
MeV in general. In one special case with the $L_e-L_\mu$ symmetry, the
$\nu_{\tau_R}$ is heavier than 2 GeV so that this particular version of the
model is already ruled out.


title:
Heavy Tau Neutrino as the Late Decaying Particle in the Cold Dark Matter
  Scenario

abstract:
  The tau neutrino with a mass of about 10 MeV can be the ``late decaying
particle'' in the cold dark matter scenario for the formation of structure in
the Universe. We show how this may be realized specifically in the recently
proposed doublet Majoron model.