title:
The Doublet-Triplet Splitting Problem and Higgses as Pseudogoldstone
  Bosons

abstract:
  The doublet-triplet splitting problem is probably the most significant
challenge to supersymmetric GUT theories. In this talk, we review potential
solutions and their problematic aspects. We also present a complete consistent
realization of our preferred solution, higgses as pseudogoldstone bosons, and
discuss some distinctive aspects of its phenomenology.


title: The ttbar threshold at a muon collider

abstract:
  The beam energy spread is a major issue in future attempts to study the
$t\overline{t}$ threshold at $e^+e^-$ colliders. Muon colliders are expected to
naturally have narrow band beams making them an ideal place to study the
excitation curve. We present the parameter determinations that are possible
from measuring the total cross section near threshold at a $\mu ^+\mu ^-$
collider.


title:
Chiral Perturbation Theory for phi -> rho gamma gamma and phi -> omega
  gamma gamma

abstract:
  We predict differential decay distributions for phi->rho gamma gamma and phi
-> omega gamma gamma using chiral perturbation theory. We also consider the
isospin violating decay phi -> omega pi^0. Experimental information on these
decays can be used to determine couplings in the heavy vector meson chiral
Lagrangian.


title: Model-Independent Determinations of B -> D l nu , D* l nu Form Factors

abstract:
  We present nonperturbative, model-independent parametrizations of the
individual QCD form factors relevant to B -> D* l nu and B -> D l nu decays.
These results follow from dispersion relations and analyticity, without
recourse to heavy quark symmetry. To describe a form factor with two percent
accuracy, three parameters are necessary, one of which is its normalization at
zero recoil, F(1). We combine the individual form factors using heavy quark
symmetry to extract values for the product |V_{cb}| F(1) from B -> D* l nu data
with negligible extrapolation uncertainty.


title: Future of Top-Quark Physics at Fermilab

abstract:
  I discuss some of the physics of the top quark which will be explored in the
near and more-distant future at the Tevatron.


title: Examination of the Resonance Contributions to Dileptonic Rare B-Decays

abstract:
  We analyse the long-distance contribution to $B\to X_s\ell^+\ell^-$
differential decay rate when the momentum dependence of $\psi$ and
$\psi'$-$\gamma$ conversion strength is taken into account. The results
indicate that the resonance to nonresonance interference in the dilepton
invariant mass distribution is substantially reduced.


title:
Radiative Electroweak symmetry breaking in the MSSM and Low Energy
  Thresholds

abstract:
  We study Radiative Electroweak Symmetry Breaking in the Minimal
Supersymmetric Standard Model (MSSM). We employ the 2-loop Renormalization
Group equations for running masses and couplings taking into account sparticle
threshold effects. The decoupling of each particle below its threshold is
realized by a step function in all one-loop Renormalization Group equations
(RGE). This program requires the calculation of all wavefunction, vertex and
mass renormalizations for all particles involved. Adapting our numerical
routines to take care of the succesive decoupling of each particle below its
threshold, we compute the mass spectrum of sparticles and Higgses consistent
with the existing experimental constraints. The effect of the threshold
corrections is in general of the same order of magnitude as the two-loop
contributions with the exception of the heavy Higgses.


title: Dynamical Generation of Light Fermions

abstract:
  We show that composite fermions with masses much smaller than the scale of
confinement arise naturally in certain models which admit dynamical breakdown
of chiral symmetry.
  The models are such that to leading order some of the fermions remain
massless but pick up small dynamical masses at subleading order.


title: Heavy-to-Light Meson Transitions in QCD

abstract:
  I discuss QCD sum rules determinations of the form factors governing the
decay $B \to \pi (\rho) \ell \nu$. For some of these form factors the computed
dependence on the momentum transferred does not agree with the expectation from
the nearest pole dominance hypothesis. Relations are observed among the form
factors, that seem to be compatible with equations recently derived by B.Stech.
The measurement of a number of color suppressed nonleptonic B decay rates could
shed light on the accuracy of the calculation of these form factors and on the
factorization approximation.


title: A Global Test of QCD Theories for Direct Photon Production

abstract:
  Direct photon production data at fixed target and collider experiments from
$pp$ and $\bar{p}p$ collisions are analysed in NLO QCD. The results are grouped
into three sets having $\sqrt{s}=20-30$ GeV, 630 GeV and 1.8 TeV. It is seen
that at the lowest energies considered, the theory systematically underpredicts
the results for all the values of the transverse momentum. At the intermediate
energy of the UA2 experiment, the data are more accurately described at high
$p_T$, and at the highest collider energies no significant underprediction is
seen even at low $p_T$, when using recent structure functions as measured at
HERA.


title: Symmetry breaking and electroweak physics at Photon Linear Colliders

abstract:
  The physics potential of a high-energy photon collider is reviewed. The
emphasis is put on aspects related to the symmetry breaking sector, including
Higgs searches and production of longitudinal vector bosons.


title:
The Strong Coupling and the Bottom Mass in Supersymmetric Grand Unified
  Theories

abstract:
  We apply the full one-loop corrections to the masses, gauge couplings, and
Yukawa couplings in the minimal supersymmetric standard model. We focus on
predictions for the strong coupling and the bottom-quark pole mass in the
context of SU(5) supersymmetric grand unification. We discuss our results in
both the small and large $\tan\beta$ regimes. We demonstrate that the finite
(non-logarithmic) corrections to the weak mixing angle are essential in
determining $\alpha_s$ and $m_b$ when some superpartner masses are light.
Minimal SU(5) predicts acceptable $\alpha_s$ and $m_b$ only at small
$\tan\beta$ with SUSY masses of $\cal O$(TeV). The missing doublet model
accommodates gauge and Yukawa coupling unification for small or large
$\tan\beta$, and for any SUSY mass scale. In the large $\tan\beta$ case, the
bottom mass is acceptable only if the Higgsino mass parameter $\mu$ is
positive.


title:
O(4) symmetric singular solutions and multiparticle cross sections in
  $\phi^4$ theory at tree level

abstract:
  We solve the classical euclidean boundary value problem for tree-level
multiparticle production in $\phi^4$ theory at arbitrary energies in the case
of $O(4)$ symmetric field configurations. We reproduce known low-energy results
and obtain a lower bound on the tree cross sections at arbitrary energies.


title: Resolved Photon Processes

abstract:
  We review the present level of knowledge of the hadronic structure of the
photon, as revealed in interactions involving quarks and gluons ``in" the
photon. The concept of photon structure functions is introduced in the
description of deep--inelastic $e \gamma$ scattering, and existing
parametrizations of the parton densities in the photon are reviewed. We then
turn to hard \gamp\ and \gaga\ collisions, where we treat the production of
jets, heavy quarks, hard (direct) photons, \jpsi\ mesons, and lepton pairs. We
also comment on issues that go beyond perturbation theory, including recent
attempts at a comprehensive description of both hard and soft \gamp\ and \gaga\
interactions. We conclude with a list of open problems.


title:
Pure electroweak mechanism for the electric dipole moment of neutron in
  the Kobayashi-Maskawa model

abstract:
  The pure electroweak three-loop mechanism for the induced electric and
chromoelectric dipole moments of quarks is studied in the Kobayashi-Maskawa
model with three and four generations. In the standard three generation case,
this mechanism is found to produce a negligible contribution to the electric
dipole moment of neutron. In the presence of the fourth heavy generation,
however, pure electroweak corrections are important and might be several times
larger than the corresponding QCD contribution for the masses of heaviest
quarks $\sim$ 500-600 GeV. The resulting electric dipole moment of neutron
naturally arises at the level of $10^{-29} \,e\cdot cm$. The effects of the
fourth generation physics are parametrized at standard electroweak scale by the
presence of the effective charged right-handed currents.


title: Determining the CP of a Higgs Particle at a Future Linear Collider

abstract:
  In a more general electroweak theory, there could be Higgs particles that are
odd under $CP$. Correlations among momenta of the initial electron and
final-state fermions are in the Bjorken process sensitive to the $CP$ parity.
Monte Carlo data on the expected efficiency demonstrate that it should be
possible to verify the scalar character of an intermediate-mass Standard Model
Higgs boson after three years of data taking at a future linear collider. This
is most likely not possible at LEP2. Signals of possible presence of $CP$
violation in the Higgs sector are briefly discussed.


title: Rapidity Gaps in DIS through Soft Colour Interactions

abstract:
  We present a new mechanism for the creation of large rapidity gaps in DIS
events at HERA. Soft colour interactions between perturbatively produced
partons and colour-charges in the proton remnant, modifies the colour structure
for hadronization giving colour singlet systems that are well separated in
rapidity. An explicit model is presented that, although the detailed results
depend on the initial state parton emission, can describe both the observed
rapidity gaps and, in addition, the forward energy flow in an inclusive event
sample.


title: Model gluon propagator and pion and rho-meson observables

abstract:
  A one parameter, model confined-gluon propagator is employed in a
phenomenological application of the Dyson-Schwinger and Bethe-Salpeter
equations to the calculation of a range of $\pi$- and $\rho$-meson observables.
Good agreement is obtained with the data. The calculated quark propagator does
not have a singularity on the real-$p^2$ axis. A mass formula for the pion,
involving only the vacuum, dressed quark propagator, is presented and shown to
provide an accurate estimate of the mass obtained via a direct solution of the
Bethe-Salpeter equation.


title: Non-Equilibrium Phase Transitions and Domain Walls

abstract:
  Non-equilibrium phase transitions of a scalar field in an expanding spacetime
are discussed. These transitions are shown to lead, for appropriate potential
energy functions, to a biased choice of vacuum structure which can be
analytically described using percolation theory. The initial domain wall
networks, which form between different vacua, are evolved in time by computer
simulation and their behavior analyzed. It is shown that, unlike systems in
thermal equilibrium, domain walls formed in biased systems persist for only a
short time before decaying exponentially away. This result opens the door to a
re-analysis of domain walls in cosmology.


title: An Introduction to Heavy Mesons

abstract:
  Introductory lectures (delivered at the VI Mexican School of Particles and
Fields) on heavy quarks and heavy quark effective field theory. Applications to
inclusive semileptonic decays and to interactions with light mesons are covered
in detail.


title: The spin of the nucleon in its rest system

abstract:
  The spin dependent structure functions, g$_{1p}$ of the proton and g$_{1n}$
of the neutron, calculated in the nucleon rest frame using a relativistic quark
model wave function, are compared with recent experiments.


title: Multiinstanton ladders in Baryon Number Violating Processes

abstract:
  We estimate the contribution of a class of multiinstanton ladder graphs to
baryon and lepton number violating processes in the standard model. We find
that this contribution is negligible and does not alter the high energy
behavior of the leading semiclassical approximation.


title: Physics with Like-Sign Muon Beams

abstract:
  We point out that both the specific lepton number content and the high
energies potentially attainable with muon-muon colliders make it advisable to
consider the technical feasibility of including an option of like-sign incoming
beams in the studies towards a proposal to build a muon-muon collider with
center-of-mass energies in the TeV region. This capability will add some unique
physics capabilities to the project. Special attention will have to be paid to
polarization retention for the muons.


title: Polarized Gluons in the Nucleon

abstract:
  QCD suggests that gluons in the nucleon play an important role in {\it
so-called} ``the proton spin problem''. In this talk, the behavior of the
polarized gluon distribution in the nucleon is discussed by using the
positivity condition of distribution functions together with the unpolarized
and polarized experimental data.


title: A-Dependence of Heavy Flavour Production in QCD

abstract:
  We calculate the A-dependence of charm and beauty production cross sections
on nuclear targets taking into account the difference of quark and gluon
distributions in free nucleons and in nucleus. At comparatively low energies,
if $\sigma \sim A^{\alpha}$, the value of $\alpha$ is slightly higher than
unity. With the growth of the initial energy the value of $\alpha$ decreases
and becomes smaller than unity. We also calculate the values of $\alpha$ for
different Feynman-$x$ of the produced $Q\overline{Q}$ pair and obtain that they
decrease significantly in the beam fragmentation region.


title: Dilepton Production at SPS Energies

abstract:
  We present a nonperturbative dynamical study of $e^+e^-$ production in
proton- nucleus and nucleus-nucleus collisions at SPS energies on the basis of
a covariant transport approach. For p + A reactions the dilepton yield for
invariant masses m $\leq $ 1.2 GeV is found to be dominated by the decays of
the $\eta, \rho, \omega$ and $\Phi$ mesons in line with the findings of the
CERES collaboration. For S + Au collisions at 200 GeV/A the dilepton yield is,
however, dominated by $\pi^+\pi^-$ annihilation due to the high pion densities
achieved. Whereas for `free' meson masses and form factors the experimental
cross section is slightly underestimated for 0.3 GeV $\leq$ m $\leq$ 0.45 GeV,
different medium modifications of the $\rho$-meson appear compatible with
current CERES data.


title:
Constraints on a General Higgs Sector from $K^0-\bar K^0$, $B_d- \bar
  B_d$ Mixing and the $\epsilon$ Parameter

abstract:
  The scalar sector of the Standard Model is extended to include an arbitrary
assortment of scalars. In the case where this assignment does not preserve
$\rho=1$ at the tree-level, the departure from unity itself puts the most
stringent constraint on the scalar sector, and where $\rho_{tree}=1$ is
maintained, useful bounds on the parameter space of the charged Higgs mass and
the doublet-nondoublet mixing angle can arise from data on $\bbbar$, $\kkbar$
mixing and the $\e$ parameter. These constraints turn out to be comparable (and
in some cases, better) to those obtained from $\zbb$ data.


title: Towards a Complete Feynman Diagrams Automatic Computation System

abstract:
  Complete Feynman diagram automatic computation systems are now coming of age
after many years of development. They are made available to the high energy
physics community through user-friendly interfaces. Theorists and
experimentalists can benefit from these powerful packages for speeding up time
consuming calculations and for preparing event generators. The general
architecture of these packages is presented and the current development of the
one-loop diagrams extension is discussed. A rapid description of the prominent
packages and tools is then proposed. Finally, the necessity for defining a
standardization scheme is heavily stressed for the benefit of developers and
users.


title: Fermion Masses in SUSY GUTs

abstract:
  We discuss the fermion mass problem in SUSY GUTs, including such ideas as
texture zeroes, and Georgi-Jarlskog textures. We focus on a specific
supersymmetric model based on the gauge group $SU(4)\otimes SU(2)_L \otimes
SU(2)_R$. In this model the gauge group is broken to that of the standard model
at $10^{16}$ GeV, and supersymmetry is broken at low-energy. The model may be
regarded as a ``surrogate SUSY GUT'', and has several advantages over the
$SU(5)$ and $SO(10)$ SUSY GUTs, such as the absence of the doublet-triplet
splitting problem, and a simpler Higgs sector which does not involve any large
Higgs representations. The model predicts full quadruple Yukawa unification
(top-bottom-tau-tau neutrino), leading to the prediction of large top mass and
$\tan \beta$. An operator analysis leads to schemes where the strange and down
mass are predicted, and $|V_{ub}|>0.004$.


title: Neutralino Decays in the Minimal Supersymmetric Standard Model

abstract:
  A complete phenomenological study of the next-to-lightest neutralino decays
is performed in the MSSM. The widths and branching ratios for all the possible
decay channels (including the radiative decay X0(2) --> X0(1) gamma and the
decay into a light Higgs X0(2) --> X0(1) h0) are studied in detail as functions
of all the SuSy parameters of the model. Particular attention is paid to
situations that are interesting for LEP2 searches. Non-trivial decay patterns
are found that critically depend on the region of the parameter space
considered.


title: Beyond Leading Logarithm Parton Distributions in the photon

abstract:
  I discuss the parton distributions in the photon and the constraints coming
from the jet production in photoproduction and in photon-photon collisions.


title:
Single Spin Asymmetry in Inclusive Pion Production, Collins Effect and
  the String Model (revised version)

abstract:
  We calculated the single spin asymmetry in the inclusive pion production in
the fragmentation region of transversely polarized proton-proton collisions. We
generated the asymmetry at the level of fragmentation function (Collins effect)
by the Lund coloured string mechanism. We compared our results to the presently
available experimental data. We obtained a qualitative agreement with the data
after assuming that the transverse polarizations of the $u$ and the $d$ quarks
in the proton are +1 and -1, respectively, at x_B = 1.


title: The Spectrum and Confinement for the Bethe-Salpeter Equation

abstract:
  The problem of calculating of the mass spectrum of the two-body
Bethe-Salpeter equation is studied with no reduction to the three-dimensional
("quasipotential") equation. The method to find the ground state and excited
states for a channel with any quantum numbers is presented. The problem of the
confining interaction for the Bethe-Salpeter equation is discussed from the
point of view of formal properties of the bound state spectrum, but with only
an inspiration from the QCD. We study the kernel that is non-vanishing at large
Euclidian intervals, $R_E\to \infty$, which is constructed as a special
limiting case of a sum of the covariant one-boson-exchange kernels. When the
usual attractive interaction is added, it is found that this kernel is similar
in its effect to the non-relativistic potential in coordinate space, $V(r)$,
with $V(r\to \infty) \to V_{\infty}$. The positive real constant $V_{\infty}$
gives the scale that define the limit of bound state spectrum compared to the
sum of the constituent masses, $M < 2m + V_{\infty}$. At the same time the
self-energy corrections remove the singularities from the propagators of the
constituents, i.e. constituents do not propagate as free particles. Combination
of these features of the solutions allows an interpretation of this type of
interaction as a confining one. The illustrative calculations are presented for
a model of massive scalar particles with scalar interaction, i.e. the "massive
Wick model".


title:
Three-Loop O(alpha_s^2 G_F M_t^2) Corrections to Higgs Production and
  Decay at e^+e^- Colliders

abstract:
  We evaluate the next-to-leading-order QCD corrections of O(alpha_s^2 G_F
M_t^2) to the Standard-Model l^+l^-H, ZZH, and W^+W^-H couplings in the
heavy-top- quark limit. Exploiting these results together with knowledge of
Delta rho to the same order, we analyze a variety of production and decay
processes of low- mass Higgs bosons at e^+e^- colliders. Specifically, we
consider H->l^+l^-, H->l^+l^-l'^+l'^-, e^+e^-->ZH, Z->ff-barH, and
e^+e^-->ff-barH, with f=l,nu. We work in the electroweak on-shell scheme
formulated with G_F and employ both the on-shell and MS-bar definitions of the
top-quark mass in QCD. As expected, the scheme and scale dependences are
greatly reduced when the next-to-leading- order corrections are taken into
account. In the on-shell scheme of top-quark mass renormalization, the
O(alpha_s^2 G_F M_t^2) corrections act in the same direction as the O(alpha_s
G_F M_t^2) ones and further increase the screening of the O(G_F M_t^2) terms.
The coefficients of (alpha_s/pi)^2 range from -6.847 for the ZZH coupling to
-16.201 for the l^+l^-H coupling. This is in line with the value -14.594
recently found for Delta rho.


title: Model-Independent Semileptonic Form Factors Using Dispersion Relations

abstract:
  We present a method for parametrizing heavy meson semileptonic form factors
using dispersion relations, and from it produce a two-parameter description of
the B -> B elastic form factor. We use heavy quark symmetry to relate this
function to B -> D* l nu form factors, and extract
|V_cb|=0.0355^{+0.0029}_{-0.0025} from experimental data with a least squares
fit. Our method eliminates model-dependent uncertainties inherent in choosing a
parametrization for the extrapolation of the differential decay rate to
threshold.


title: Probing u-bar/d-bar Asymmetry in the Proton via W and Z Production

abstract:
  The sensitivity of $W$ and $Z$ production at RHIC to the possible $\bar
u/\bar d$ asymmetry in the proton is studied. The ratios of the $W^+$ over
$W^-$ production cross sections in $p + p$ collision, as well as the ratios of
the $W^+$ and $Z$ production cross sections for $p + p$ over $p + d$
collisions, are shown to be sensitive to this asymmetry. Predictions of various
theoretical models for these ratios are presented.


title: Probing u-bar/d-bar Asymmetry in the Proton via Quarkonium Production

abstract:
  The sensitivity of proton-induced $J/\psi$ and $\Upsilon$ production to the
possible $\bar u/\bar d$ asymmetry in the nucleon is studied. The ratio of the
quarkonium production cross sections at large $x_F$ on hydrogen over deuterium
targets, $\sigma (p+p) / \sigma (p+d)$, is shown to be sensitive to this
asymmetry. Predictions of various theoretical models for this ratio are
presented.


title: Effective Field Theories

abstract:
  These lectures introduce some of the basic notions of effective field
theories, as used in particle physics. The topics discussed are the $\Delta
S=1$ and $\Delta S =2$ weak interactions, and chiral perturbation theory as
applied to mesons, baryons, and hadrons containing heavy quarks.


title: Numerical solution of $Q^2$ evolution equations in a brute-force method

abstract:
  We investigate numerical solution of $Q^2$ evolution equations for structure
functions in the nucleon and in nuclei.
(Dokshitzer-Gribov-Lipatov-)Altarelli-Parisi and Mueller-Qiu evolution
equations are solved in a brute-force method. Spin-independent
flavor-nonsinglet and singlet equations with next-to-leading-order $\alpha_s$
corrections are studied. Dividing the variables $x$ and $Q^2$ into small steps,
we simply solve the integrodifferential equations. Numerical results indicate
that accuracy is better than 2\% in the region $10^{-4}<x<0.8$ if more than
two-hundred $Q^2$ steps and more than one-thousand $x$ steps are taken. The
numerical solution is discussed in detail, and evolution results are compared
with $Q^2$ dependent data in CDHSW, SLAC, BCDMS, EMC, NMC, Fermilab-E665, ZEUS,
and H1 experiments. We provide a FORTRAN program for Q$^2$ evolution (and
``devolution'') of nonsinglet-quark, singlet-quark, $q_i+\bar q_i$, and gluon
distributions (and corresponding structure functions) in the nucleon and in
nuclei. This is a very useful program for studying spin-independent structure
functions.


title:
Renormalization Effect on Large Neutrino Flavor Mixing in the Minimal
  Supersymmetric Standard Model

abstract:
  In the minimal supersymmetric standard model, we have studied the evolution
of the neutrino flavor mixing by using the renormalization group equation(RGE)
with the Georgi-Jarlskog texture for the Yukawa coupling matrices.For the large
Yukawa coupling of the charged lepton, i.e.,$\tan\b \gg 1$, the neutrino flavor
mixing increases significantly with running down to the electroweak scale by
the RGE. If one wishes to get the large neutrino flavor mixing $\sin \th_{23}$
at the electroweak scale, which is suggested by the muon neutrino deficit in
the atomospheric neutrino flux, the initial condition $\sin \th_{23}\geq 0.27$
is required at the GUT scale. Combined with the see-saw enhancement of the
neutrino flavor mixing, the large mixing is naturally reproduced by setting the
reasonable initial condition.


title: Elastic Charge Form Factors of $\pi$ and K Mesons

abstract:
  The elastic charge form factors of the charged $\pi$ and $K$ mesons are
calculated in modified impulse approximation using instant form of relativistic
Hamiltonian dynamics. Our approach gives pion and kaon electromagnetic form
factors in the large range of momentum transfer. The results are in good
agreement with the available data. Relativistic effects are large at all values
of momentum transfers. The pion and kaon form factors at large $Q^2$ depend
strongly on the choice of model. The experiments on pion form factor at large
momentum transfer planned at CEBAF will choose between such models. In the case
of kaon such a choosing may be performed only if supplemented by accurate
measurements of kaon MSR.


title:
Neutralino dark matter in supersymmetric models with non--universal
  scalar mass terms

abstract:
  Neutralino dark matter is studied in the context of a supergravity scheme
  where the scalar mass terms are not constrained by universality conditions at
the grand unification scale. We analyse in detail the consequences of the
relaxation of this universality assumption on the supersymmetric parameter
space, on the neutralino relic abundance and on the event rate for the direct
detection of relic neutralinos.


title: Leptonic and Semileptonic Decays of Charm and Bottom Hadrons

abstract:
  We review the experimental measurements and theoretical descriptions of
leptonic and semileptonic decays of particles containing a single heavy quark,
either charm or bottom. Measurements of bottom semileptonic decays are used to
determine the magnitudes of two fundamental parameters of the standard model,
the Cabibbo-Kobayashi-Maskawa matrix elements $V_{cb}$ and $V_{ub}$. These
parameters are connected with the physics of quark flavor and mass, and they
have important implications for the breakdown of CP symmetry. To extract
precise values of $|V_{cb}|$ and $|V_{ub}|$ from measurements, however,
requires a good understanding of the decay dynamics. Measurements of both charm
and bottom decay distributions provide information on the interactions
governing these processes. The underlying weak transition in each case is
relatively simple, but the strong interactions that bind the quarks into
hadrons introduce complications. We also discuss new theoretical approaches,
especially heavy-quark effective theory and lattice QCD, which are providing
insights and predictions now being tested by experiment. An international
effort at many laboratories will rapidly advance knowledge of this physics
during the next decade.


title: Effect of magnetic field on the strange star

abstract:
  We study the effect of a magnetic field on the strage quark matter and apply
to strange star. We found that the strange star becomes more compact in
presence of strong magnetic field.


title: Charmed Baryons with $J = 3/2$

abstract:
  The width of a recently discovered excited charmed-strange baryon, a
candidate for a state $\Xi_c^*$ with spin 3/2, is calculated. In the absence of
configuration mixing between the ground-state (spin-1/2) charmed-strange baryon
$\Xi_c^{(a)}$ and the spin-1/2 state $\Xi_c^{(s)}$ lying about 95 MeV above it,
one finds $\tilde \Gamma(\Xi^*_c \to \Xi_c^{(a)} \pi) = (3/4) \tilde
\Gamma(\Xi^* \to \Xi \pi)$ and $\tilde \Gamma(\Xi^*_c \to \Xi_c^{(s)} \pi) =
(1/4) \tilde \Gamma(\Xi^* \to \Xi \pi)$, where the tilde denotes the partial
width with kinematic factors removed. Assuming a kinematic factor for P-wave
decay of $p_{\rm cm}^3$, one predicts $\Gamma(\Xi^*_c \to \Xi_c^{(a)} \pi) =
2.3$ MeV, while the $\Xi^*_c \to \Xi_c^{(s)} \pi$ channel is closed. Some
suggestions are given for detecting the $\Sigma_c^*$, the spin-3/2 charmed
nonstrange baryon, and the $\Omega_c^*$, the spin-3/2 charmed doubly-strange
baryon.


title: The Missing Doublet Model Revamped

abstract:
  We revisit the Missing Doublet Model (MDM) as a means to address the apparent
difficulties of the minimal $SU(5)$ supergravity model in dealing with the
doublet-triplet splitting problem, the prediction of $\alpha_3(M_Z)$, and the
proton lifetime. We revamp the original MDM by extending its observable sector
to include fields and interactions that naturally suppress the dimension-five
proton decay operators and that allow see-saw neutrino masses. We also endow
the model with a hidden sector which (via gaugino condensation) triggers
supersymmetry breaking of the desired magnitude, and (via hidden matter
condensation) yields a new dynamical intermediate scale for the right-handed
neutrino masses ($\sim10^{10}\GeV$), and provides an effective Higgs mixing
parameter $\mu$. The model is consistent with gauge coupling unification for
experimentally acceptable values of $\alpha_3(M_Z)$, and with proton decay
limits even for large values of $\tan\beta$. The right-handed neutrinos can be
produced subsequent to inflation, and their out-of-equilibrium decays induce a
lepton asymmetry which is later reprocessed (via sphaleron interactions) into a
baryon asymmetry at the electroweak scale. The resulting see-saw neutrino
masses provide a candidate for the hot dark matter component of the Universe
($m_{\nu_\tau}\sim{\cal O}(10\eV)$) and are consistent with the MSW solution to
the solar neutrino problem. We finally compare the features of this traditional
GUT model with that of the readily string-derivable $SU(5)\times U(1)$ model,
and discuss the prospects of deriving the revamped MDM from string theory.


title: A Decisive Test of Superstring-Inspired E(6) Models

abstract:
  We point out that in a large class of superstring--inspired $E(6)$ models,
either an e+e- collider operating at a center--of--mass energy $\rs= 1.5$ TeV
or higher must detect the pair production of charged or neutral exotic leptons,
or an e+e- collider with $\rs \geq 300$ GeV must discover at least one light
neutral Higgs boson with invisible branching ratio exceeding 50\%. If neither
of these two signals is seen, the lightest neutral exotic lepton would
overclose the universe, and the model could be completely excluded, independent
of the values of the numerous free parameters. Future Higgs searches might
lower the energy of the e+e- collider needed to test these models decisively.
The only assumptions we have to make are that $R-$parity is exact, so that the
lightest exotic lepton is stable if it is lighter than the lightest neutralino,
and that no $SO(10)$ singlet scalar gets a vacuum expectation of order
$10^{10}$ GeV or higher. If the second condition is violated, the model
effectively reduces to an $SO(10)$ model as far as collider experiments are
concerned.


title: Radiative rare $B$ decays revisited

abstract:
  We reexamine contributions of higher $K$-resonances to the radiative rare
decays $b\rar s\gamma$ in the limit where both $b$- and $s$-quark are
considered heavy. Using the non-relativistic quark model, and the form factor
definitions consistent with the HQET covariant trace formalism, we find
significant disagreement with previous work which also used heavy quark
symmetry, and excellent agreement with experimental results. In particular, the
two largest fractions of the inclusive $b\rar s\gamma$ branching ratio are
found to be $(16.8\pm 6.4)\%$ for $B\rar K^{*}(892)\gamma$ and $(6.2\pm 2.9)\%$
for $B\rar K_{2}^{*}(1430)\gamma$ decays. We also compare the contribution from
the radiative decays into the eight $K$-meson states to the inclusive
experimental $b\rar s\gamma$ mass distribution.


title: Some Signals for a Light Neutralino

abstract:
  If a light gaugino sector exists in the supersymmetric standard model then
the mass of lightest neutralino may be of the order of 1 GeV or less. As a
consequence of neutral flavor violation in supersymmetric theories $B_s$-meson
may decay into a pair of lightest neutralinos in such a case. It is found that
the parameter space for such light neutralinos can be appreciably constrained
by looking for such decays. We also show how a rare B-decays ($B
\longrightarrow K(K^{*}) + invisible$ channels) can help us in probing a light
neutralino in B-factories in a reasonably model- independent manner. Finally,
we observe that that the decay of a tau-lepton into a muon and a pair of light
neutralinos can cause a violation of weak universality which is larger in
magnitude than that from any source known so far.


title: Anomalous g^5_z coupling at $\gamma\gamma$ colliders

abstract:
  We study the constraints on the anomalous coupling $g^Z_5$ that can be
obtained from the analysis of the reaction $\gamma\gamma \rightarrow W^+ W^- Z$
at future linear $e^+e^-$ colliders. We find out that a $0.5$ ($1$) TeV
$e^+e^-$ collider operating in the $\gamma\gamma$ mode can probe values of
$g_5^Z$ of the order of $0.15$ ($4.5 \times 10^{-2}$) for an integrated
luminosity of $10$ fb$^{-1}$. This shows that the ability to search for this
anomalous interaction of the $\gamma\gamma$ mode is better than the one of the
usual $e^+e^-$ mode, and it is similar to the ability of the $e\gamma$ mode.


title: Some issues in soft SUSY-breaking terms from dilaton/moduli sectors

abstract:
  We study the structure of the soft SUSY-breaking terms obtained from some
classes of 4-D strings under the assumption of dilaton/moduli dominance in the
process of SUSY-breaking. We generalize previous analysis in several ways and
in particular consider the new features appearing when several moduli fields
contribute to SUSY breaking (instead of an overall modulus $T$). Some
qualitative features indeed change in the multimoduli case.A general discussion
for symmetric Abelian orbifolds as well as explicit examples are given. Certain
general sum-rules involving soft terms of different particles are shown to
apply to large classes of models. Unlike in the overall modulus $T$ case,
gauginos may be lighter than scalars even at the tree-level. However, if one
insists in getting that pattern of soft terms, these sum rules force some of
the scalars to get negative mass$^2$. These tachyonic masses could be a problem
for standard model 4-D strings but an advantage in the case of string-GUTs.We
also discuss the possible effects of off-diagonal metrics for the matter fields
which may give rise to flavour-changing neutral currents. Different sources for
the bilinear $B$ soft term are studied. It is found that the Giudice-Masiero
mechanism for generating a ``$\mu $-term'', as naturally implemented in
orbifolds, leads to the prediction $|tg\beta |=1$ at the string scale,
independently of the Goldstino direction.


title: Deep-Inelastic Onium Scattering

abstract:
  Using the colour dipole approach of the QCD perturbative (BFKL) Pomeron
exchange in onium-onium scattering, we compute the cross section for small but
hierarchically different onium sizes. A specific term dependent on the
size-ratio is generated. In deep inelastic onium scattering it appears as a
scaling violation contribution to the quark structure function near the BFKL
singularity. We find that the extension of the formalism for deep inelastic
onium scattering to the proton structure function provides a remarkably good
3-parameter fit to HERA data at small x with a simple physical interpretation
in terms of the dipole formulation.


title: Heavy Quark Production In Hadronic Collisions

abstract:
  We review the physics of heavy quark and quarkonium production in high energy
hadronic collisions. We discuss the status of the theoretical calculations and
compare the current results with the most recent measurements from the Tevatron
collider experiments.


title: Small-x Effects in W + jets Production at the Tevatron

abstract:
  The jet structure in events with Drell-Yan-produced W bosons is discussed,
and a new model for describing such event is presented. The model is shown to
explain recent measurements of the W-jet rapidity correlation and predicts a
transverse energy flow at high W rapidities (corresponding to probing small-x
partons in one of the incoming protons) higher than conventional parton cascade
event generators.


title:
Relativistic Description of Exclusive Heavy-to-Light Semileptonic Decays
  $B\to\pi(\rho)e\nu$

abstract:
  The method of calculating electroweak decay matrix elements between
heavy-heavy and heavy-light meson states is developed in the framework of
relativistic quark model based on the quasipotential approach in quantum field
theory. This method is applied for the study of exclusive semileptonic
$B\to\pi(\rho)$ decays. It is shown that the large value of the final
$\pi(\rho)$ meson recoil momentum allows for the expansion in inverse powers of
$b$-quark mass of the decay form factors at $q^2=0$, where $q^2$ is a momentum
carried by the lepton pair. This $1/m_b$ expansion considerably simplifies the
analysis of these decays and is carried out up to the second order. The
$q^2$-dependence of the form factors is investigated. It is found that the
$q^2$-behaviour of the axial form factor $A_1$ is different from the other form
factors. It is argued that the ratios $\Gamma(B\to\rho e\nu)/\Gamma(B\to\pi
e\nu)$ and $\Gamma_L/\Gamma_T$ are sensitive probes of the $A_1$
$q^2$-dependence, and thus their experimental measurement may discriminate
between different approaches. We find $\Gamma(B\to\pi e\nu)=(3.0\pm0.6)
\times|V_{ub}|^2\times10^{12}$s$^{-1}$ and $\Gamma(B\to\rho e\nu) =(5.4\pm
1.2)\times|V_{ub}|^2\times10^{12}$s$^{-1}$. The relation between semileptonic
and rare radiative $B$-decays is discussed.


title: Higgs Boson Masses in Supersymmetric Theories

abstract:
  The Higgs boson mass problem is considered in the next to minimal
supersymmetric standard model. The Higgs potential and the renormalization
group equations for the gauge, Yukawa and scalar coupling constants are
analyzed. The restrictions for the Higgs boson masses are found for the cases
of presence and absence of spontaneous CP- violation.


title: The $\xi(2220)$ Revistited

abstract:
  We calculated the decay widths of the $1^3F_2$ and $1^3F_4$ $s\bar{s}$ mesons
and compared them to the measured properties of the $\xi(2220)$ (now known as
the $f_4(2220)$). Including previously neglected decay modes we found that the
width of the $^3F_2$ state $s\bar{s}$ meson is much larger than previously
believed making this explanation unlikely. On the other hand the predicted
width of the $^3F_4$ state, although broader than the observed width, is
consistent within the uncertainties of the model. This interpretation predicts
large partial widths to $K K^*(892)$ and $K^*(892) K^*(892)$ final states which
should be looked for. A second possibility that would account for the different
properties of the $\xi(2220)$ seen in different experiments is that two
hadronic states exist at this mass. The first would be a broader $^3F_4$
$s\bar{s}$ state which is seen in hadron beam experiments while the second
would be a narrow state with high glue content seen in the gluon rich $J/\psi$
radiative decay. Further experimental results are needed to sort this out.


title:
Two-photon decays of the lightest Higgs boson of supersymmetry at the
  LHC

abstract:
  We discuss the production and two-photon decay of the lightest Higgs boson
(h) of the minimal supersymmetric standard model at the CERN Large Hadron
Collider. Since the observability of the signal is quite model dependent, we
conduct a thorough scan of the parameter space of minimal supersymmetry,
including experimental and theoretical constraints. If kinematically allowed,
supersymmetric decay modes of h may be important, and can even dominate all
others. The coupling of h to $b\overline b$ can be different from that of a
standard model Higgs boson; this can diminish (or enhance, but only if
tan$\beta$ is very large) the h -> $\gamma\gamma$ signal. We emphasize the
importance of a full treatment of radiative corrections in the Higgs sector for
obtaining the h $b\overline b$ coupling. If supersymmetric particles are not
too heavy, their contributions in loops can either enhance or suppress both the
production cross-section and the h -> $\gamma\gamma$ branching fraction. We
discuss the relative importance of these factors in the context of various
scenarios for the discovery of supersymmetry. Even if h is not detected at the
LHC, h may still exist in its expected mass region.


title: Standard Model Parameters from Quarkonia using Lattice QCD

abstract:
  Quarkonia -- mesons made of a heavy quark and anti-quark -- have been
extensively studied experimentally. Theoretical calculations of quarkonia based
on lattice QCD are possible with control over the systematic errors. The
comparison with experimental measurements of the quarkonia spectra leads to
determinations of Standard Model parameters: the strong coupling, $\alpha_s$,
and the heavy quark masses.


title: Improving the Measurement of the Top Quark Mass

abstract:
  Two possible ways to improve the mass resolution for observing hadronic top
quark decay $t \to bW \to 3 jets$ are studied: (1) using fixed cones in the
rest frames of the $t$ and $W$ to define the decay jets, instead of the
traditional cones in the rest frame of the detector; and (2) using the jet
angles in the top rest frame to measure $m_t/m_W$. By Monte Carlo simulation,
the second method is found to give a useful improvement in the mass resolution.
It can be combined with the usual invariant mass method to get an even better
mass measurement. The improved resolution can be used to make a more accurate
determination of the top quark mass, and to improve the discrimination between
$t \bar t$ events and background for studies of the production mechanism.


title: Charmed Baryon Masses in Chiral Perturbation Theory

abstract:
  The masses of the charmed baryons in the ${\bf 6}$ representation of $SU(3)$
obey an equal spacing rule at lowest order in $SU(3)$ breaking, ${\cal
O}(m_s)$. We compute the corrections to this relation at order ${\cal
O}(m_s^{3/2})$ arising from meson loops using chiral perturbation theory
combined with heavy quark symmetry and find them to be small. We also examine
the hyperfine interaction responsible for the splitting between the
$J^\pi={3\over 2}^+$ and $J^\pi={1\over 2}^+$ baryons in the \ss\
representation. The results also hold in the b-baryon sector.


title: A SUSY SO(10) GUT with an Intermediate Scale

abstract:
  We examine a superpotential for an SO(10) GUT and show that if the parameters
of the superpotential are in a certain region, the SO(10) GUT has an
intermediate symmetry ${\rm SU(2)}_L \otimes {\rm SU(2)}_R \otimes {\rm
SU(3)}_C \otimes {\rm U(1)}_{B-L}$ which breaks down to the group of the
Standard Model at an intermediate scale $10^{10-12}$ GeV. In the model by the
breakdown of the symmetry right-handed neutrinos acquire mass of the
intermediate scale through a renormalizable Yukawa coupling.


title: The QCD Analysis of the Structure Functions and Effective Nucleon Mass

abstract:
  On the basis of the target mass corrections to structure functions of
deep-inelastic scattering of leptons, we evaluate effective nucleon mass that
turns out to be twice $M_{nucl.}$ for deep-inelastic scattering on the nucleus
target and equals $M_{nucl.}$ for the hydrogen target.


title:
W- and Z-Boson Interactions in Supersymmetric Models with Explicit
  R-Parity Violation

abstract:
  The minimal supersymmetric Standard Model with explicit R-parity
nonconservation contains bilinear terms involving the left-handed lepton
superfields and the Higgs chiral multiplet with hypercharge Y=+1, which cannot
in general be rotated away in the presence of soft-supersymmetry- breaking
interactions. These bilinear lepton-number-violating terms are found to give
rise to non-zero vacuum expectation values of the scalar neutrinos. This leads
to nonuniversal and flavour-violating tree-level couplings of the W and Z
bosons to charged leptons and neutrinos. The parameter space of this novel
scenario is systematically analyzed and further restricted by a number of
laboratory, astrophysical, and cosmological constraints. The possibility that
our minimal model can account for the KARMEN anomaly is examined.


title: CP Violation and Flavour Mixing in the Standard Model

abstract:
  We review and update the constraints on the parameters of the quark flavour
mixing matrix $V_{CKM}$ in the standard model and estimate the resulting CP
asymmetries in $B$ decays, taking into account recent experimental and
theoretical developments. In performing our fits, we use inputs from the
measurements of the following quantities: (i) $\abseps$, the CP-violating
parameter in $K$ decays, (ii) $\delmd$, the mass difference due to the
\bdbdbar\ mixing, (iii) the matrix elements $\absvcb$ and $\absvub$, (iv)
$B$-hadron lifetimes, and (v) the top quark mass. The experimental input in
points (ii) - (v) has improved compared to our previous fits. With the updated
CKM matrix we present the currently-allowed range of the ratios
$|V_{td}/V_{ts}|$ and $|V_{td}/V_{ub}|$, as well as the standard model
predictions for the \bsbsbar\ mixing parameter $\xs$ (or, equivalently,
$\delms$) and the quantities $\sin 2\alpha$, $\sin 2\beta$ and $\sin^2\gamma$,
which characterize the CP-asymmetries in $B$-decays. Various theoretical issues
related to the so-called ``penguin-pollution," are of importance for the
determination of the phases $\alpha$ and $\gamma$ from the CP-asymmetries in
$B$ decays, are also discussed. (to be published in the proc. of the Pisa heavy
flavour physics conference.)


title: The Neutrino Masses in SUSY GUT

abstract:
  The neutrino mass problem in $SU(4) \times SU(2)_{L} \times SU(2)_{R}$ SUSY
GUT obtained from the compactification of $E_{8} \times E_{8}$ heterotic string
is analyzed. The estimated values of the neutrino masses and mixing angles can
explain the experimental data on solar neutrino flux.


title: Angular Distributions of Massive Quarks and Leptons Close to Threshold

abstract:
  Predictions for the angular distribution of massive quarks and leptons are
presented, including QCD and QED corrections. Recent results for the fermionic
part of the two-loop corrections to the electromagnetic form factors are
combined with the BLM scale fixing prescription. Two distinctly different
scales arise as arguments of $\alpha_s(\mu^2)$ near threshold: the relative
momentum of the quarks governing the soft gluon exchange responsible for the
Coulomb potential, and a large momentum scale approximately equal to twice the
quark mass for the corrections induced by transverse gluons. Numerical
predictions for charmed, bottom, and top quarks are given. One obtains a direct
determination of $\alpha_V(Q^2)$, the coupling in the heavy quark potential,
which can be compared with lattice gauge theory predictions. The corresponding
QED results for $\tau$ pair production allow for a measurement of the magnetic
moment of the $\tau$ and could be tested at a future $\tau$-charm factory.


title: Reconciling sterile neutrinos with big bang nucleosynthesis

abstract:
  We re-examine the big bang nucleosynthesis (BBN) bounds on the mixing of
neutrinos with sterile species. These bounds depend on the assumption that the
relic neutrino asymmetry $L_{\nu}$ is very small. We show that for $L_{\nu}$
large enough (greater than about $10^{-5}$) the standard BBN bounds do not
apply. We apply this result to the sterile neutrino solution to the atmospheric
neutrino anomaly and show that for $L_{\nu} > 7 \times 10^{-5}$ it is
consistent with BBN. The BBN bounds on sterile neutrinos mixing with electron
neutrinos can also be weakened considerably.


title: Charmonium Composition and Nuclear Suppression

abstract:
  We study charmonium production in hadron-nucleus collisions through the
intermediate next-to-leading Fock space component $|(\bar{c}c)_8 g>$, formed by
a colour octet $\bar{c}c$ pair and a gluon. We estimate the size of this state
and show that its interaction with nucleons accounts for the observed
charmonium suppression in nuclear interactions.


title:
Elastic Neutrino-Nucleon and Antineutrino-Nucleon Scattering and Strange
  Form Factors of the Nucleons

abstract:
  Elastic scattering of neutrinos and antineutrinos on nucleons is considered.
It is shown that the measurement of the neutrino-antineutrino asymmetry would
allow to obtain model independent informations on the strange axial and vector
form factors. The ratio of the magnetic form factors of the proton and neutron,
on which the asymmetry depends, is investigated in detail. The asymmetry is
calculated under different assumptions on the behavior of the strange vector
and axial form factors.


title: Physics of Single-Top Quark Production at Hadron Colliders

abstract:
  We discuss the physics of single-top quark production and decay at hadron
colliders, such as the Tevatron, the \tevstar~and the LHC. Our study includes
how to measure the mass and the width of the top quark produced from a
{\hbox{single-$t$}} or a single-$\bar t$ process. We also show how to probe new
physics by studying the couplings of $t$-${b}$-$W$ and show what can be
improved from measuring the production rate of single-top events. We also
discuss how to probe CP properties of the top quark by measuring the single-top
production rate. Finally, we present a Monte Carlo study on the detection of
single-top events in hadron collisions.


title: A Simple Description of Strange Dibaryons in the Skyrme Model

abstract:
  We study strange dibaryons based on the SU(2)-embedded B=2 toroidal soliton.
Treating the excursions of the soliton into strange directions as small rigid
oscillations, we obtain a good approximation to the bound state approach. We
calculate the dibaryon mass formula to order 1/N and find that the doubly
strange I=J=0 dibaryon is bound by about 90 MeV.


title: The non-Abelian Debye screening length beyond leading order

abstract:
  In quantum electrodynamics, static electric fields are screened at non-zero
temperatures by charges in the plasma. The inverse screening length, or Debye
mass, may be analyzed in perturbation theory and is of order $eT$ at
relativistic temperatures. An analogous situation occurs when non-Abelian gauge
theories are studied perturbatively, but the perturbative analysis breaks down
when corrections of order $e^2 T$ are considered. At this order, the Debye mass
depends on the non-perturbative physics of confinement, and a perturbative
``definition'' of the Debye mass as the pole of a gluon propagator does not
even make sense. In this work, we show how the Debye mass can be defined
non-perturbatively in a manifestly gauge invariant manner (in vector-like gauge
theories with zero chemical potential). In addition, we show how the $O(e^2 T)$
correction could be determined by a fairly simple, three-dimensional, numerical
lattice calculation of the perimeter-law behavior of large, adjoint-charge
Wilson loops.


title: Experimental limits on antigravity in extended supergravity

abstract:
  The available tests of the equivalence principle constrain the mass of the
Higgs-like boson appearing in extended supergravity theories. We determine the
constraints imposed by the present and future high precision experiments on the
antigravity fields arising from $N=2,8$ supergravity.


title: Pion (Kaon) and Sigma polarizabilities

abstract:
  We report the results of the working group on ``Pion (Kaon) and Sigma
Polarizabilities''. Interesting possibilities to measure these polarizabilities
include the radiative pion photoproduction in the MAMI experiment at Mainz, as
well as at the GRAAL facility (actually the latter is being considered for an
experimental determination of the pion polarizabilities here for the first
time), the experimental plans on Primakoff effect at FNAL, and the measurements
at the Frascati $\Phi$-factory DA$\Phi$NE.


title:
QCD corrections to the decay $H^+ \to \st \bar{\sb}$ in the Minimal
  Supersymmetric Standard Model

abstract:
  We calculate the supersymmetric ${\cal O}(\alpha_s)$ QCD corrections to the
width of the decay $H^+ \rightarrow \st\bar{\sb}$ within the Minimal
Supersymmetric Standard Model. We find that the QCD corrections are
significant, but that they do not invalidate our previous conclusionat
tree-level on the dominance of the $\st\bar{\sb}$ mode in a wide parameter
region.


title: Order (Z\alpha)^4 m/M Ry Correction to Hydrogen Levels

abstract:
  The first in m/M and fourth in Z\alpha (pure recoil) correction to a hydrogen
energy level is found. This correction comprises two contributions, one coming
from the atomic scale, the other from distances of the Compton wavelength
order. Two different perturbation schemes are used to calculate the former. One
of them exploits as unperturbed the solution to the Dirac-Coulomb problem, the
nucleus' slow motion being the source of the perturbation. The alternative
scheme treats both the electron and the nucleus as slow, while relativistic
effects are considered perturbatively. The short-distance contribution is found
in the Feynman and Coulomb gauges. Recent results for P levels are confirmed,
in contrast with those for S levels. Numerically, the shift equals 2.77 kHz for
the ground state and 0.51 kHz for 2S state.


title: BFKL versus HERA

abstract:
  The BFKL equation and the kT-factorization theorem are used to obtain
predictions for F2 in the small Bjorken-x region over a wide range of Q**2. The
dependence on the parameters, especially on those concerning the infrared
region, is discussed. After a background fit to recent experimental data
obtained at HERA and at Fermilab (E665 experiment), we find that the predicted,
almost Q**2 independent BFKL slope lambda >= 0.5 appears to be too steep at
lower Q**2 values. Thus there seems to be a chance that future HERA data can
distinguish between pure BFKL and conventional field theoretic renormalization
group approaches.


title:
Multiparton interactions and production of minijets in high energy
  hadronic collisions

abstract:
  We discuss the inclusive cross section to produce two minijets with a large
separation in rapidity in high energy hadronic collisions. The contribution to
the inclusive cross section from the exchange of a BFKL Pomeron is compared
with the contribution from the exchange of two BFKL Pomerons, which is induced
by the unitarization of the semi-hard interaction. The effect of the multiple
exchange is studied both as a function of the azimuthal correlation and as a
function of the transverse momentum of the observed minijets.


title: Kaon-Nucleon Couplings for Weak Decays of Hypernuclei

abstract:
  We investigate the weak kaon-nucleon (NNK) S-wave and P-wave interactions
using heavy baryon chiral perturbation theory. The leading 1-loop SU(3)
breaking contributions to the $ppK$, $pnK$, and $nnK$ couplings are computed.
We find that they suppress all NNK amplitudes by $30\%$ to $50\%$. The ratio of
neutron-induced to proton-induced hypernuclear decay widths is sensitive to
such reductions. It has been argued that the discrepancy between the predicted
and observed P-wave amplitudes in $\Delta s=1$ hyperon decay results from an
accidental cancellation between tree-level amplitudes, and is not a fundamental
problem for chiral perturbation theory. Agreement between experimentally
determined NNK P-wave amplitudes and our estimates would support this
explanation.


title: Flavor Mixing Signals For Realistic Supersymmetric Unification

abstract:
  The gauge interactions of any supersymmetric extension of the standard model
involve new flavor mixing matrices. The assumptions involved in the
construction of minimal supersymmetric models, both $SU(3) \times SU(2) \times
U(1)$ and grand unified theories, force a large degree of triviality on these
matrices. However, the requirement of realistic quark and lepton masses in
supersymmetric grand unified theories forces these matrices to be non-trivial.
This leads to important new dominant contributions to the neutron electric
dipole moment and to the decay mode $p \to K^o\mu^+$, and suggests that there
may be important weak scale radiative corrections to the Yukawa coupling matrix
of the up quarks. The lepton flavor violating signal $\mu \to e\gamma$ is
studied in these theories when $\tan\beta$ is sufficiently large that radiative
effects of couplings other than $\lambda_t$ must be included. The naive
expectation that large $\tan\beta$ will force sleptons to unacceptably large
masses is not borne out: radiative suppressions to the leptonic flavor mixing
angles allow regions where the sleptons are as light as 300 GeV, provided the
top Yukawa coupling in the unified theory is near the minimal value consistent
with $m_t$.


title: Static Parameters of Hadrons and Quantum Groups

abstract:
  We study the static properties of hadrons, assuming quantum group symmetry.
We calculate the magnetic moment, axial form factor and A-symmetry, using
$SU_q(2)$ and $SU_q(3)$ quantum groups. The results are fitted with
experimental data, giving an interval of $0.9<q<1.1$. Some of the implications
for the deformation parameter are discussed.


title:
Low-Energy Effective Lagrangian from Non-Minimal Supergravity with
  Unified Gauge Symmetry

abstract:
  From general supergravity theory with unified gauge symmetry, we obtain the
low-energy effective Lagrangian by taking the flat limit and integrating out
the superheavy fields in model-independent manner. The scalar potential
possesses some excellent features. Some light fields classified by using
supersymmetric fermion mass, in general, would get intermediate masses at the
tree level after the supersymmetry is broken. We show that the stability of
weak scale can be guaranteed under some conditions. There exist extra
non-universal contributions to soft supersymmetry breaking terms which can give
an impact on phenomenological study.


title:
Phenomenology of Light Gauginos: I. Motivation, Masses, Lifetimes and
  Limits

abstract:
  I explore an economical variant on supersymmetric standard models which may
be indicated on cosmological grounds and is shown to have no SUSY-CP problem.
Demanding radiative electroweak symmetry breaking suggests that the Higgs is
light; other scalar masses may be ~ 100-200 GeV or less. In this case the
gluino and photino, while massless at tree level, have 1-loop masses m(gluino)
~ 100 - 600 MeV and m(photino) ~ 100 - 1000 MeV. New hadrons with mass ~ 1 - 3
GeV are predicted and their lifetimes estimated. Existing experimental limits
are discussed.


title: Phenomenology of Light Gauginos: II. Experimental Signatures

abstract:
  When SUSY breaking produces only dimension-2 terms in the minimal
supersymmetric standard model, the parameters of the theory can be rather well
constrained. This paper deals with strategies for the detection of the new
hadrons predicted in the 1-3 GeV mass range. Some limits are obtained. New
signatures for squarks are also given. Squark masses as small as 45 GeV are not
yet excluded.


title: A low $\alpha_s$ and its consequences for unified model building

abstract:
  We review various ways of obtaining consistency between the idea of
supersymmetric grand unification and an apparent low value of $\alpha_s \sim
0.112$ indicated by several low energy experiments. We argue that to reconcile
the low value of $\alpha_s$ with the predictions of supersymmetric GUTs, we
need to go beyond the standard minimal supersymmetric GUT scenario and invoke
new physics either at $10^{11}-10^{12}$ GeV, or at the GUT scale.


title: Quo Vadis, Fascinum?

abstract:
  The recent progress in our understanding of heavy-flavour decays allows us to
define more reliably which future measurements on charm decays are needed to
further advance our understanding of QCD and to get our theoretical tools ready
for treating beauty decays. After sketching the theoretical landscape I list
those required measurements. I argue that some -- in particular those
concerning inclusive semileptonic charm decays and their lepton spectra -- can
presumably be performed only at a tau-charm factory.


title:
Sensitivity of the LHC to Electroweak Symmetry Breaking: Equivalence
  Theorem as a Criterion

abstract:
  Based upon our recent study on the intrinsic connection between the
longitudinal weak-boson scatterings and probing the electroweak symmetry
breaking (EWSB) mechanism, we reveal the profound physical content of the
Equivalence Theorem (ET) as being able to discriminate physical processes which
are sensitive/insensitive to probing the EWSB sector. With this physical
content of the ET as a criterion, we analyze the complete set of the bosonic
operators in the electroweak chiral Lagrangian and systematically classify the
sensitivities to probing all these operators at the CERN LHC via the weak-boson
fusion in $W^\pm W^\pm$ channel. This is achieved by developing a precise power
counting rule (a generalization from Weinberg's counting method) to {\it
separately} count the power dependences on the energy $E$ and all relevant mass
scales.


title: A Geometry of the Generations

abstract:
  We propose a geometric theory of flavor based on the discrete group
$(S_3)^3$, in the context of the minimal supersymmetric standard model. The
group treats three objects symmetrically, while making fundamental distinctions
between the generations. The top quark is the only heavy quark in the symmetry
limit, and the first and second generation squarks are degenerate. The
hierarchical nature of Yukawa matrices is a consequence of a sequential
breaking of $(S_3)^3$.


title: Accessing directly the strange quark content of the proton at HERA

abstract:
  We investigate a double-spin asymmetry for the semi-inclusive $\Lambda$
hyperon production in the longitudinally deep inelastic lepton-proton
scattering, the sign of which can provide us with important information about
the strange quark helicity distribution in the proton.On the basis of the
interpretation of the longitudinal deep inelastic lepton-nucleon scattering
data as a negative strange quark polarization in the proton and the preliminary
results on the measurement of the longitudinal $\Lambda$ polarization at the
$Z$ resonance in electron-positron annihilation,we predict a minus sign for the
suggested observable. The experimental condition required for our suggestion is
met by the HERA facilities, so the asymmetry considered can be measured by the
HERMES experiments at HERA in the near future.


title: Table-Top Time Reversal Violation

abstract:
  Many electrical and mechanical systems with two normal modes are appropriate
for illustrating the quantum mechanics of neutral kaons. The illustration of
CP- or time-reversal-violation in the neutral kaon system by mechanical or
electrical analogues is more subtle. Some possibilities which could be realized
in a table-top demonstration are suggested.


title: Strangeness in the Scalar Form Factor of the Nucleon

abstract:
  The scalar form factor of the nucleon and related physical quantities are
investigated in the framework of the semibosonized SU(3) Nambu-Jona-Lasinio
soliton model. We take into account the rotational $1/N_c$ corrections and
linear $m_s$ corrections. The strangeness content of the nucleon in the scalar
form factor is discussed in detail. In particular, it is found that the $m_s$
corrections play an essential role of reducing the $\langle N | \bar{s} s | N
\rangle$ arising from the leading order and rotational $1/N_c$ contributions.
We obtain the $\sigma_{\pi N} (0)=40.80\;\mbox{MeV}$, $\Delta \sigma =
\sigma_{\pi N} (2m^{2}_{\pi})-\sigma_{\pi N} (0) = 18.18\;\mbox{MeV}$ and
$\langle r^2\rangle^{S}_{N} = 1.50\;\mbox{fm}^2$.
  The results are in a remarkable agreement with empirical data analyzed by
Gasser, Leutwyler, and Sainio~\cite{gls}.


title: Gravitational Perturbations of Relativistic Membranes and Strings

abstract:
  We consider gravitationally induced perturbations of relativistic
Dirac--Goto--Nambu membranes and strings (or {\it p}-branes). The dynamics are
described by the first and second fundamental tensors, and related curvature
tensors in an {\it n}-dimensional spacetime. We show how equations of motion
can be derived for the perturbations within a general gauge and then discuss
how various simple gauge choices can be used to simplify the equations of
motion for specific applications. We also show how the same equations of motion
can be derived from an effective action by a variational principle. Finally, we
compare these equations of motion to those using more familiar notation for
brane dynamics, which involves the induced metric on the worldsheet. This work
sets up a general formalism for understanding the effects of backreaction on
brane dynamics and the background curvature.


title: Radiative Backreaction on Global Strings

abstract:
  We consider radiative backreaction for global strings using the Kalb-Ramond
formalism. In analogy to the point electron in classical electrodynamics, we
show how local radiative corrections to the equations of motion allow one to
remove the divergence in the self field and calculate a first order
approximation to the radiation backreaction force. The effects of this
backreaction force are studied numerically by resubstituting the equations of
motion to suppress exponentially growing solutions. By direct comparison with
numerical field theory simulations and analytic radiation calculations we
establish that the `local backreaction approximation' provides a satisfactory
quantitative description of radiative damping for a wide variety of string
configurations. Finally, we discuss the relevance of this work to the evolution
of a network of global strings and their possible cosmological consequences.
These methods can also be applied to describe the effects of gravitational
radiation backreaction on local strings, electromagnetic radiation backreaction
on superconducting strings and other forms of string radiative backreaction.


title:
Quantum Corrections to the Weizs\"acker--Williams Distribution Function
  as Small x

abstract:
  We compute the quantum corrections to the gluon distribution function in the
background of a non--Abelian Weizs\"acker--Williams field. These corrections
are valid to all orders in the effective coupling $\alpha_s \mu$, where $\mu^2$
denotes the average valence quark color charge squared per unit area. We find
$\ln(1/x)$ logarithmic corrections to the classical gluon distribution
function. The one loop corrections to the classical Weizs\"acker-Williams field
do not contribute to these singular terms in the distribution function. Their
effect is to cause the running of $\alpha_s$.


title: A variety of CP violating B decays

abstract:
  A variety of CP violating asymmetries in $B^0$ decays is predicted in the
Standard Model in terms of CKM (Cabibbo-Kobayashi-Maskawa) complex phases.
These phases can also be determined from rate measurements of certain $B^+$ and
$B^-$ decays. We focus on the following processes: $B^0\to\psi
K_S,~\pi^+\pi^-,~\pi^0\pi^0, ~\rho^{\pm}\pi^{\mp},~B_s\to D^+_s K^-,~\pi^0\eta,
~B^+\to D^0(\Dbar)K^+,~\pi^+\pi^0,~\pi^0 K^+,~ \pi^+ K^0,~\eta K^+$ and their
charge-conjugates. Complications due to gluonic-penguin and electroweak-penguin
amplitudes are dealt with and are resolved. The importance of final state
interaction phases in charged $B$ decay asymmetries is demonstrated in
$B^+\to\chi_{c0}\pi^+,~~\chi_{c0}\to\pi^+\pi^-$ through the effect of the
$\chi_{c0}$ width.


title: Measurement of $V_{ub}$

abstract:
  The most recent experimental measurements of the weak mixing angle $V_{ub}$
are summarized. Inclusive and exclusive analysis techniques are described,
including a new exclusive analysis by the CLEO collaboration measuring the
$B\rightarrow \pi\ell\nu$ branching ratio. Future prospects are discussed.


title: Thermal phase transition in QCD

abstract:
  We give a review of modern theoretical understanding of the problem of
thermal phase transition in $QCD$. The existence or non-existence of such
transition depends on the nature of the gauge group, the number of light quark
flavors , and on the value of quark masses. Numerical lattice measurements
indicate that the phase transition {\it does} not occur for the experimentally
observed values of quark masses.


title:
Polarisation-Asymmetry Correlation in Allowed $\beta$-Decay: a Probe for
  Right-Handed Currents

abstract:
  The sensitivity of polarisation-asymmetry correlation experiments to charged
currents of right-handed chirality contributing to allowed $\beta$-decay is
considered in the most general context possible, independently of any type of
approximation nor of any specific model for physics beyond the Standard Model
of the electroweak interactions. Results are then particularised to general
Left-Right Symmetric Models, and experimental prospects offered by mirror
nuclei are assessed explicitly on general grounds. In order of decreasing
interest, the cases of $^{17}$F, $^{41}$Sc and $^{25}$Al are the most
attractive, providing sensitivities better or comparable to allowed pure
Gamow-Teller transitions, with the advantage however, that recoil order
corrections are smaller in the case of super-allowed decays.


title: Chiral symmetry breaking in strongly coupled QED?

abstract:
  The coupled system of renormalized Dyson-Schwinger equations for the electron
self-energy and the photon propagator are supplied with the tree level vertex
as Ansatz for the renormalized three point function. The system is investigated
numerically. In the case of a massive electron, the theory is ``weakly
renormalizable'', i.e.\ cutoff independent for values of the cutoff below an
upper limit. In this regime of cutoff independence, the quenched approximation
yields good results for the electron self-energy. In the chiral limit, a
logarithmic cutoff dependence of the electron self-energy is found. The
question, whether a regime of cutoff independence with a spontaneously broken
chiral symmetry exists in strongly coupled QED, remains open.


title: Bose-Einstein source of intermittency in hadronic interactions

abstract:
  The multi-particle Bose-Einstein correlations are the source of
''intermittency'' in high energy hadronic collisions. The power-law like
increase of factorial moments with decreasing bin size was obtained by complete
event weighing technique with gaussian approximation of space-time particle
emitting source shape. The value of source size parameter was found to be
higher than the common one fitted with the help of the standard Handbury
Brown-Twiss procedure.


title:
Semihard diffractive production of neutral mesons by off shell photons
  and the range of pQCD validity

abstract:
  We study the dependence on photon virtuality $Q^2$ for the semihard
quasi--elastic photoproduction of neutral vector mesons on a quark, gluon or
real photon (at $s\gg p_{\bot}^2, Q^2; p_{\bot}^2 \gg \mu^2 \approx (0.3$
GeV)$^2$). To this end we calculate the corresponding amplitudes (in an
analytical form) in the lowest nontrivial approximation of the perturbative
QCD. The amplitudes for the production of mesons consisting of light quarks
vary very rapidly with the photon virtuality near $Q^2=0$.
  We estimate the bound of the pQCD validity region for such processes. For the
process with mass shell photon the obtained bound is very high, and this region
seems beyond opportunities of real experiment. This bound decreases fast with
the increase of $Q^2$, and we expect that the virtual photoproduction at HERA
provides the opportunity to test the pQCD results. The signature of this region
is discussed.


title: Anomaly-Free Gauged R-Symmetry

abstract:
  We review the gauging of an R-symmetry in local and global susy. We then
construct the first anomaly-free models. We break the R-symmetry and susy at
the Planck scale and discuss the low-energy effects. We include a solution to
the mu-problem, and the prediction of observable effects at HERA. The models
also nicely allow for GUT-scale baryogenesis and R-parity violation without the
sphaleron interactions erasing the baryon-asymmetry.


title: Q**2 Dependence of Nuclear Shadowing

abstract:
  We re-examine the predictions of a two-phase model of shadowing in nuclear
deep-inelastic scattering in light of new NMC data on the x, A and Q**2
dependence of the ratios of structure functions. The model, which combines
vector meson dominance at low Q**2 with diffractive Pomeron exchange for large
Q**2, agrees with the observed small, but non-zero, slopes in log Q**2, which
indicate the importance of higher twist shadowing effects in the transition
region, 0.1 < Q**2 < 1 GeV**2. We note also that the latest E665 data on the
deuteron to proton ratio suggests the presence of a small amount of shadowing
in the deuteron.


title:
Decay Rates, Structure Functions and New Physics Effects in Hadronic Tau
  Decays

abstract:
  Hadronic decays rates of the $\tau$ lepton into multi meson final states are
presented. The structure of the hadronic matrix elements for various decay
modes is discussed. The formalism of structure functions allows for a detailed
test of these matrix elements. Various correlations are discussed which are
sensitive to possible CP violation and new physics effects in the decay modes.


title: Rest Frame Valence Quark Model for Deep Inelastic Scattering

abstract:
  A rest frame valence quark model is applied to the deep inelastic scattering
of charged leptons by protons. The parameters of the model are determined by a
fit to unpolarized electron cross sections. The model then can be used to
calculate the asymmetry in polarized deep inelastic scattering. The predicted
spin-dependent structure function g1p is in good agreement with recent
measurements. This indicates that, in the proton rest system, the spin of the
proton is carried by the valence quarks.


title:
Large Tree Level CP Violation in $e^+e^-\to t\bar{t}H^0$ in The Two
  Higgs Doublet Model

abstract:
  We find a large CP violation effect within the Two-Higgs-Doublet-Model for
the reaction $e^+e^-\to t\bar{t}H^0$ at future linear colliders. The
CP-asymmetry arises already at the tree level as a result of interference
between diagrams with $H^0$ emission from $t$ (and $\bar{t}$) and its emission
from a $Z^0$ and can be about 10--20\%. In the best case one needs a few
hundred $t\bar{t}H^0$ events to observe CP violation at the 3$\sigma$ level.


title: Perturbative Static Four-Quark Potentials

abstract:
  A first attempt to understand hadron dynamics at low energies in terms of the
fundamental quark and gluon degrees of freedom incorporates the effects of the
gluonic field into a potential depending only on the spatial positions of the
quarks, which are considered in the infinite mass limit. A suitable framework
for calculating such potentials between static quarks, i.e.\ a generalization
of the Wilson loop will be discussed.
  Making a connection with recent Monte Carlo lattice simulations for the
lowest two energies of a system of two quarks and two antiquarks, the static
$qq\bar{q}\bar{q}$-potential will be calculated in perturbation theory to
fourth order. The result will be shown to be exactly equal to the prediction of
a straightforward two-body approach, which in Monte Carlo lattice simulations
has been found to be a reasonable approximation for very small interquark
distances.


title: Cosmological Baryon Asymmetry and Kaon CP Violation from a Common Source

abstract:
  We extend an earlier model for radiatively generated fermion masses based on
the Pati-Salam group to include CP violation. Spontaneous CP violation in the
early universe gives rise to a complex mass matrix for heavy sterile neutrinos.
The out-of-equilibrium decay of these neutrinos generates a $B-L$ asymmetry.
The sterile neutrinos also act as a mass seed in generating one-loop (complex)
mass matrices for the quarks. Thus, the two low energy manifestations of CP
violation -- the CKM phase and the baryon number asymmetry -- can both be
traced in a calculable way to a common source.


title: Inverse Neutrinoless Double Beta Decay Revisited

abstract:
  We critically reexamine the prospects for the observation of the $\Delta L=2$
lepton-number-violating process $\eeWW$ using the $e^-e^-$ option of a
high-energy $e^+e^-$ collider (NLC). We find that, except in the most contrived
scenarios, constraints from neutrinoless double beta decay render the process
unobservable at an NLC of $\sqrt{s}<2$ TeV. Other $\Delta L=2$ processes such
as $\ggllww$, $\egnllw$, $\eennll$ ($\ell=\mu,\tau$), and $\egeww$, which use
various options of the NLC, require a $\sqrt{s}$ of at least 4 TeV for
observability.


title: Photon Intensity Interferometry for Expanding Sources

abstract:
  Using Quantum Field Theory we derive a general formula for the double
inclusive spectra of photons radiated by a system in local equilibrium. The
derived expression differs significantly from the one mostly used up to now in
photon intensity interferometry of heavy--ion collisions. We present a
covariant expression for double inclusive spectra adapted for usage in
numerical simulations. Application to a schematic model with a Bj\o rken type
expansion gives strong evidence for the need of reinvestigating photon--photon
correlations for expanding sources.


title: Diffractive light vector meson production at large momentum transfers

abstract:
  The diffractive process $\gamma^*(Q^2) p\to V+X$ (where $V= \rho^0, \omega ,
\phi$ are the vector mesons, consisted of light quarks, $X$ represents the
hadrons to that a proton dissociates) is studied. We consider the region of
large momentum transfers, $|t|>>\Lambda^2_{QCD}$, and large energies, s. In the
leading log approximation of perturbative QCD ( using BFKL equation ) the
asymptotic behaviour of the cross section in the limit $s\to\infty , s>>|t|,
Q^2$ is obtained.
  We compare the results derived from BFKL equation with that obtained in the
lowest order of QCD (two--gluon exchange in the $t$- channel). The possibility
to investigate these reactions at HERA is discussed.


title: Gauged R-symmetry, Fermion and Higgs Mass Problem

abstract:
  We consider the simplest model of $SU(3) \times SU(2) \times U(1)_Y \times
U(1)_R$ gauge symmetry with one extra singlet field whose vacuum expectation
value breaks the horizontal $R$-symmetry $U(1)_R$ and gives rise to Yukawa
textures. The $U(1)_R$ symmetry is able to provide both acceptable fermion mass
hierarchies and a natural solution to the $\mu$ problem only if its mixed
anomalies are cancelled by the Green-Schwarz mechanism. When the canonical
normalization $g_3^2=g_2^2={5\over3}g_1^2$ of the gauge coupling constants is
assumed, the Higgs mass parameter $\mu \sim m_{3/2}$ can arise taking into
acount the uncertainty in the ultraviolet relation $m_e m_\mu m_\tau/m_d m_s
m_b \simeq \lambda^q$ with $q \neq 0$. When $q=0$ is taken only a suppressed
value of $\mu \sim \lambda m_{3/2}$ can be obtained.


title:
Cosmological Relic Density from Minimal Supergravity with Implications
  for Collider Physics

abstract:
  Working within the framework of the minimal supergravity model with gauge
coupling unification and radiative electroweak symmetry breaking, we evaluate
the cosmological relic density from lightest neutralinos produced in the early
universe. Our numerical calculation is distinct in that it involves direct
evaluation of neutralino annihilation cross sections using helicity amplitude
techniques, and thus avoids the usual expansion as a power series in terms of
neutralino velocity. Thus, our calculation includes relativistic Boltzmann
averaging, neutralino annihilation threshold effects, and proper treatment of
integration over Breit-Wigner poles. We map out regions of parameter space that
give rise to interesting cosmological dark matter relic densities. We compare
these regions with recent calculations of the reach for supersymmetry by LEP2
and Tevatron Main Injector era experiments. The cosmologically favored regions
overlap considerably with the regions where large trilepton signals are
expected to occur at the Tevatron. The CERN LHC $pp$ collider can make a
thorough exploration of the cosmologically favored region via gluino and squark
searches. In addition, over most of the favored region, sleptons ought to be
light enough to be detectable at both LHC and at a $\sqrt{s}=500$ GeV $e^+e^-$
collider.


title: Fermion Masses and Mixings in a String-Inspired Model

abstract:
  We study quark and lepton mass matrix textures in a model containing an
additional $U(1)_X$ gauge symmetry with origins in string compactification. The
$U(1)_X$ symmetry is broken near the string scale, and we assume that the
anomalies are canceled by the Green-Schwarz mechanism. We also assume that
fermion mass matrices are generated by an additional scalar field through an
approach analogous to that of Froggatt and Nielsen. By requiring that
supersymmetry not be broken at the high scale, we can derive the vacuum
expectation value of this scalar field to then predict fermion masses and
mixings for any given $X$ charge assignment. We examine the possible solutions,
and although in the simplest model they do not completely agree with
experiment, the results are close enough to merit further inspection.


title: Confinement and complex singularities in QED3

abstract:
  The standard approximations of the Dyson--Schwinger equation lead to complex
singularities of the fermion propagator. In three-dimensional QED one can show
that this phenomenon might be related to confinement: a confining potential
leads to mass-like singularities at complex momenta, and thus to the absence of
a mass singularity on the real timelike axis. The correct treatment of the
vacuum polarization is essential for the confining nature of QED3.


title: Hyperon Decays in Chiral Perturbation Theory Revisited

abstract:
  The discrepancies found between S-wave and P-wave fits for hyperon decays are
reinvestigated using the heavy baryon chiral Lagrangian formalism.
  The agreement is found to improve through the inclusion of previously omitted
diagrams. The S-waves are unaffected by this, but the P-wave predictions are
modified. A correlated fit to the chiral parameters is performed and the
results discussed.


title:
Scaling laws for density correlations and fluctuations in multiparticle
  dynamics

abstract:
  Experimental data are presented on particle correlations and fluctuations in
various high-energy multiparticle collisions, with special emphasis on evidence
for scaling-law evolution in small phase-space domains. The notions of
intermittency and fractality as related to the above findings are described.
Phenomenological and theoretical work on the subject is reviewed.


title: Glueball Interpretation of $\xi$(2230)

abstract:
  On the basis of the results of $\xi(2230)\rightarrow\pi^{+}\pi^{-}, p\bar{p}$
and $K\bar{K}$, measured by the BES Collaboration in radiative J/$\psi$ decays,
combined with the upper limit of Br($\xi\rightarrow
p\bar{p}$)Br($\xi\rightarrow K\bar{K}$), measured by PS185 experiment, we argue
that the distinctive properties of $\xi$(2230), the flavor-symmetric decays and
the narrow partial decay widths to $\pi\pi$ and $K\bar{K}$ as well as its
copious production in radiative J/$\psi$ decay, would strongly favor the
glueball interpretation of $\xi$(2230).


title: Quark Model Explanation of the $N^*\to N\eta$ Branching Ratios

abstract:
  The constituent quark model can explain the strong selectivity of the $N\eta$
decay branching ratios of the nucleon resonances if the fine structure
interaction between the constituent quarks is described in terms of Goldstone
boson exchange. This chiral quark model predicts that the resonances $N(1535)$,
$N(1710)$, $\Lambda(1670)$, $\Sigma(1750)$, which have mixed flavor and spin
symmetry $[21]_{FS} [21]_F [21]_S$ wavefunctions in lowest order, should have
large $N\eta$ branching ratios, while $N\eta$ decay of the other resonances
that have different flavor-spin symmetry should be strongly suppressed in
agreement with the experimental branching ratios.


title: Strangeness content of the nucleon within the NJL soliton model

abstract:
  We investigated the form factors of the nucleon associated with the nonet
vector current in the framework of the generalized Yabu--Ando approach to the
chiral soliton of the Nambu--Jona--Lasinio model. We introduce a variational
parameter to improve the predictions for the baryon mass splittings and, in
addition, we take into account $1/N_c$ rotational corrections to accommodate
the empirical isovector magnetic moment of the nucleon. We find that the
strange magnetic moment lies between -0.05 and 0.25.


title: Light Singlet Fermions and Neutrino Physics

abstract:
  The existence of a light singlet fermion mixed with the electron neutrino is
hinted by the simultaneous explanation of various neutrino anomalies. We show
that supersymmetry can provide a natural framework for the existence and the
desired properties of such a fermion. Quasi Goldstone fermions (QGF) of
spontaneously broken global symmetries like the Peccei-Quinn symmetry or lepton
number can mix properly with the neutrinos provided the presence of the
R-parity breaking term $\e LH_2$. The lightness of QGF can be a consequence of
non-minimal K\"ahler potentials like that of no-scale supergravity. In order to
keep R-parity, such a sterile component has to be placed in a new singlet
superfield with no vacuum expectation value. In the context of the standard
seesaw mechanism the lightness of such a singlet can be understood by imposing
a $R$-symmetry.


title:
Bubble wall dynamics, generalised Yukawa couplings and adequate
  electroweak baryogenesis in two-Higgs-doublet model

abstract:
  Baryogenesis at the electroweak scale depends on divers but identifiable
details of bubble wall dynamics and the particle physics. We show that
inclusion of the dynamics of relative phase in two-Higgs-doublet model (2HDM)
enhances the adiabatic order of the mechanism proposed by
McLerran-Shaposhnikov-Turok-Voloshin where the scalar-scalar-vector triangle
diagram with top quark in the loop gives rise to a significant contribution to
the effective chemical potential biasing the Chern-Simons number. We also show
that in 2HDM with less stringent constraints on Yukawa couplings than those
imposed by natural flavour conservation, there are additional diagrams
contributing to the effective chemical potential. These two effects can combine
with several others to produce adequate baryon asymmetry at the electroweak
scale.


title: Baryogenesis at the Electroweak Scale

abstract:
  The realisation that the electroweak anomaly can induce significant baryon
number violation at high temperature and that the standard models of particle
physics and cosmology contain all the ingredients needed for baryogenesis has
led to vigourous search for viable models. The conclusions so far are that the
Standard Model of particle physics cannot produce baryon asymmetry of required
magnitude. It has too little $CP$ violation and sphaleronic transitions wipe
out any asymmetry produced if the Higgs is heavier than about 50 GeV, a range
already excluded by accelerator experiments. We review the sphaleron solution,
its connection to the high temperature anomalous rate and then summarise
possibilities where phenomenologically testable extensions of the Standard
Model may yet explain the baryon asymmetry of the Universe.


title: QED Interconnection Effects on W Momentum Distributions at LEP 2

abstract:
  The process $\ee \to \W^+\W^- \to \f_1 \fbar_2 \, \f_3 \fbar_4$ contains
charges in the initial, intermediate and final stages. This gives a rich
selection of possible QED interconnection effects. Coulomb interaction is the
simplest of these, and can thus be used to explore consequences. We study a
number of experimental observables, with emphasis on those related to the W
momentum distribution. Second-order Coulomb effects are shown to be practically
negligible. The limited LEP~2 statistics will not allow detailed tests, so any
theory uncertainty will be reflected in the systematic error on the W mass.
Currently the uncertainty from this source may be as high as 20~MeV.


title:
Flavor-Changing Magnetic Dipole Moment and Oscillation of a Neutrino in
  a Degenerate Electron Plasma

abstract:
  The standard model prediction for a magnetic dipole moment of a neutrino is
proportional to the neutrino mass and extremely small. It also generates a
flavor-changing process, but the GIM mechanism reduces the corresponding
amplitude. These properties of a neutrino magnetic moment change drastically in
a degenerate electron plasma. We have shown that an electron-hole excitation
gives a contribution proportional to the electrons' Fermi momentum. Since this
effect is absent in \(\mu\) and \(\tau\) sector, the GIM cancellation does not
work. The magnetic moment induces a neutrino oscillation if a strong enough
magnetic field exists in the plasma. The required magnitude of the field
strength that affects the \nue\ burst from a supernova is estimated to be the
order of \(10^8 \) Gauss.


title:
Two -loop $O(G_F{M_H}^2)$ radiative corrections to the Higgs decay width
  $H \to \gamma \gamma $ for large Higgs boson masses

abstract:
  This note is devoted to the calculation of the two-loop $O(G_F {M_H}^2)$
radiative corrections to the Higgs decay width $H \to \gamma \gamma $ for large
values of the Higgs boson mass $M_H$ within the Minimal Standard Model.
  The use of the Equivalence Theorem makes it possible to reduce the problem to
the consideration of the physical Higgs boson field and the Goldstone bosons
$w^{+},w^{-},z$. We present analytical results for the various two- and
three-particle absorptive parts of two-loop contributions, using dispersive
techniques, analytic results for all but one of the dispersive contributions.
The typical size of the correction is $\sim ~30 $ percent for a Higgs boson
mass of order $1~TeV$.


title: Rare Radiative $B$ Decays in the Standard Model

abstract:
  A status report on the theory and phenomenology of rare radiative $B$ decays
in the standard model is presented with emphasis on the measured decays $B \to
X_s \gamma$ and $B \to K^* \gamma$. Standard model is in agreement with
experiments though this comparison is not completely quantitative due to
imprecise data and lack of the complete next-to-leading order contributions to
the decay rates. Despite this, it is possible to extract non-perturbative
parameters from the shape of the photon energy spectrum in $B \to X_s \gamma$,
such as the $b$-quark mass and the kinetic energy of the $b$ quark in $B$
hadron. The measured decay rate $\BBGAMAXS =(2.32\pm 0.67) \times 10^{-4}$ can
also be used to extract the CKM ratio $\absvts/\absvcb$, yielding
$\absvts/\absvcb =1.10 \pm 0.43$. Issues bearing on the determination of the
parameters of the CKM matrix from the CKM-suppressed decays $B \to X_d +
\gamma$ and $B \to (\rho,\omega) + \gamma$ are also discussed. It is argued
that valuable and independent constraints on the CKM matrix can be obtained
from the measurements of these decays, in particular those involving neutral
$B$-mesons (to appear in the Proceedings of the XXXth Rencontres de Moriond
``Electroweak Interactions and Unified Theories'', Les Arcs, France, March
1995).


title: Modifications of the Hubble Law in a Scale-Dependent Cosmology

abstract:
  We study some observational consequences of a recently proposed
scale--dependent cosmological model for an inhomogeneous Universe. In this
model the Universe is pictured as being inside a highly dense and rapidly
expanding shell with the underdense center. For nearby objects ($z \ll 1$), the
linear Hubble diagram is shown to remain valid even in this model, which has
been demonstrated both analytically and numerically. For large $z$, we present
some numerical results of the redshift--luminosity distance relation and the
behavior of the mass density as a function of the redshift. It is shown that
the Hubble diagram in this model for a locally $open$ Universe ($\Omega(t_0, r
\sim 0)=0.1$) resembles that of the $flat$ Friedmann cosmology. This implies
that study of the Hubble diagram cannot uniquely determine the value of $q_0$
or $\Omega_0$ in a model--independent way. The model also accounts for the fact
that $\Omega_0$ is an increasing function of the redshift.


title:
Dijet Cross Sections at O($\alpha\alpha_s^2$) in Photon-Proton
  Collisions

abstract:
  We have calculated inclusive two-jet production in low $Q^2$ $ep$ collisions
at O($\alpha\alpha_s^2$) superimposing direct and resolved contributions. The
results are compared with recent experimental data from the ZEUS collaboration
at HERA.


title: The $Z \to b \bar b$ Excess and Top Decay

abstract:
  The apparent excess of $Z \rightarrow b \bar b$ events at LEP may be an
indication of new physics beyond the standard model. However, in either the
two-Higgs-doublet model or the minimal supersymmetric standard model, any
explanation would lead to an important new decay mode of the top quark and
suppresses the $t \rightarrow W b$ branching fraction, which goes against what
has been observed at the Tevatron. In the two-Higgs-doublet model, the
branching fraction of $Z \rightarrow b \bar b$ + a light boson which decays
predominantly into $b \bar b$ would be at least of order 10$^{-4}$.


title: The Top-Quark Width in the Light of $Z$-Boson Physics

abstract:
  We discuss possible non-standard contributions to the top-quark width,
particularly the virtual effects on the standard decay $t\rightarrow W^+\,b$
within the context of the MSSM. We also place a renewed emphasis on the
unconventional mode $t\rightarrow H^+\,b$ in the light of recent analyses of
$Z$-boson observables. It turns out that in the region of parameter space
highlighted by $Z$-boson physics, the charged Higgs mode should exhibite an
appreciable branching fraction as compared to the standard decay of the top
quark. Remarkably enough, the corresponding quantum effects in this region are
also rather large, slowly decoupling, and most likely resolvable in the next
generation of experiments at Tevatron and at LHC.


title: The Decuplet Revisited in $\chi$PT

abstract:
  The paper deals with two issues. First, we explore the quantitiative
importance of higher multiplets for properties of the $\Delta$ decuplet in
chiral perturbation theory. In particular, it is found that the lowest order
one--loop contributions from the Roper octet to the decuplet masses and
magnetic moments are substantial. The relevance of these results to the chiral
expansion in general is discussed. The exact values of the magnetic moments
depend upon delicate cancellations involving ill--determined coupling
constants. Second, we present new relations between the magnetic moments of the
$\Delta$ decuplet that are independent of all couplings. They are exact at the
order of the chiral expansion used in this paper.


title: Event Structure in the Production of High Mass Photon Pairs

abstract:
  The event structure associated with the production of massive photon pairs is
studied to ${\cal O}(\alpha^2/alpha_s)$. The cross sections for two photon and
two photon plus one jet events are given. The Dalitz plot structure of events
with two photons and a jet is also presented. These distributions will provide
checks on our understanding of the production mechanisms for massive photon
pairs, a signal thought to be important for searches for the Higgs boson in the
intermediate mass region.


title: Bounds on Scalar Leptoquarks from the LEP Data

abstract:
  We obtain the constraints on scalar leptoquarks coming from radiative
corrections to $Z$ physics. We perform a global fitting to the LEP data
including the contributions of the most general effective Lagrangian for scalar
leptoquarks, which exhibits the $SU(2)_L \times U(1)_Y$ gauge invariance. Our
bounds on leptoquarks that couple to the top quark are much stronger than the
ones obtained from low energy experiments.


title: Effective potential methods and the Higgs mass spectrum in the MSSM

abstract:
  We generalize the analytical expressions for the two-loop leading-log neutral
Higgs boson masses and mixing angles to the case of general left- and
right-handed soft supersymmetry breaking stop and sbottom masses and
left--right mixing mass parameters ($m_Q, m_U, m_D, A_t, A_b$). This
generalization is essential for the computation of Higgs masses and couplings
in the presence of light stops. At high scales we use the minimal
supersymmetric standard model effective potential, while at low scales we
consider the two-Higgs doublet model (renormalization group improved) effective
potential, with general matching conditions at the thresholds where the squarks
decouple. We define physical (pole) masses for the top-quark, by including QCD
self-energies, and for the neutral Higgs bosons, by including the leading
one-loop electroweak self-energies where the top/stop and bottom/sbottom
sectors propagate. For $m_Q=m_U=m_D$ and moderate left--right mixing mass
parameters, for which the mass expansion in terms of renormalizable Higgs
quartic couplings is reliable, we find excellent agreement with previously
obtained results.