title:
QCD with Large Number of Quarks: Effects of the Instanton --
  Anti-instanton Pairs

abstract:
  We calculate the contribution of the instanton -- anti-instanton ($I\bar I$)
pairs to the vacuum energy of QCD-like theories with $N_f$ light fermions using
the saddle point method. We find a qualitative change of the behavior: for $N_f
\ge 6$ it starts to oscillate with $N_f$. Similar behaviour was known for
quantum mechanical systems interacting with fermions. We discuss the possible
consequences of this phenomenon, and its relation to the mechanism of chiral
symmetry breaking in these theories. We also discuss the asymptotics of the
perturbative series associated with the $I\bar I$ contribution, comparing our
results with those in literature.


title:
Bounds on Contact Interactions from LEP1 Data and the High-Q^2 HERA
  Events

abstract:
  A contact four-fermion interaction between light quarks and electrons has
been evoked as a possible explanation for the excess of events observed by HERA
at high-$Q^2$. We explore the 1-loop effects of such interaction in $\Gamma(Z^0
\to e^+ e^-)$ measured at LEP and impose strong bounds on the lower limit of
the effective scale. Our results are able to discard some of the contact
interactions as possible explanation for the HERA events.


title: Violating R-Parity at the B-factory

abstract:
  Supersymmetry without R-parity contains new tree-level contributions to
B-decays. A brief summary is provided of the current experimental bounds on
those tree-level contributions which are relevant to B physics. Signals to look
for are outlined in the context of CP violation and rare decays. For the first
time, the signature of general R-parity violating models is described.
B-factory experiments will provide an opportunity to look for this signal.


title: Signatures of Parton Exogamy in e+ e- -> W+ W- -> hadrons

abstract:
  We propose possible signatures of `exogamous' combinations between partons in
the different W+ and W- hadron showers in e+e- -> W+W- events with purely
hadronic final states. Within the space-time model for hadronic shower
development that we have proposed previously, we find a possible difference of
about 10 % between the mean hadronic multiplicity in such purely hadronic final
states and twice the hadronic multiplicity in events in which one W decays
hadronically and the other leptonically, i.e., <N_had(2W)> \ne 2 <N_{had}(W)>,
associated with the formation of hadronic clusters by `exogamous' pairs of
partons. We discuss the dependence of this possible difference in multiplicity
on the center-of-mass energy, on the hadron momenta, and on the angular
separation between the $W^{\pm}$ dijets. If it were observed, any such
multiplicity difference would indicate that the W's do not hadronize
independently, and hence raise questions about the accuracy with which the W
mass could be determined from purely hadronic final states.


title:
Two-loop matching of the dipole operators for $b \to s \gamma$ and $b
  \to s gluon$

abstract:
  The order $\alpha_s$ corrections to the Wilson coefficients of the dipole
operators ($O_7,O_8$) at the matching scale $\mu =m_W$ are a crucial ingredient
for a complete next- to-leading logarithmic calculation of the branching ratio
for $b \to s \gamma$. Given the phenomenological relevance and the fact that
this two-loop calculation has been done so far only by one group [1], we
present a detailed re-calculation using a different method. Our results are in
complete agreement with those in ref. [1].


title: R-invariant Natural Unification

abstract:
  We construct R-invariant unification models where a pair of massless Higgs
doublets is naturally obtained. The masslessness of the Higgs doublets is
guaranteed by the unbroken R symmetry. Mass generation for the Higgs doublets
is considered from various viewpoints.


title:
CP Violation and Matter Effect in Long Baseline Neutrino Oscillation
  Experiments

abstract:
  We show simple methods how to separate pure CP violating effect from matter
effect in long baseline neutrino oscillation experiments with three generations
of neutrinos. We give compact formulae for neutrino oscillation probabilities
assuming one of the three neutrino masses (presumably tau-neutrino mass) to be
much larger than the other masses and the effective mass due to matter effect.
Two methods are shown: One is to observe envelopes of the curves of oscillation
probabilities as functions of neutrino energy; a merit of this method is that
only a single detector is enough to determine the presence of CP violation. The
other is to compare experiments with at least two different baseline lengths;
this has a merit that it needs only narrow energy range of oscillation data.


title:
Restrictions on the Hadronic Contribution to the Muon $(g-2)$-factor and
  to the Pion Electromagnetic Formfactor from Analytical Properties of the Pion
  Electromagnetic Formfactor

abstract:
  We investigate restrictions on the hadronic contribution to the muon $(g-2)$
factor and to the pion electromagnetic formfactor from the analytical
properties of the pion formfactor and the experimental data of the pion
formfactor in the space-like [1] region. The values of the pion formfactor of
[1] have been improved (see Table 1) and the values of the pion formfactor have
been calculated at 20 additional points (see Table 2).


title: Charming Penguins in B decays

abstract:
  Full expressions of the $B^0_d \to \pi^+ \pi^-$ and $B^0_d \to \pi^0 \pi^0$
amplitudes, given in terms of matrix elements of operators of the effective
weak Hamiltonian, are used to study the dependence of the relevant branching
ratios on the different contributions. The uncertainty in the extraction of the
weak phase $\alpha$ from the measurement of the time-dependent asymmetry in
$B^0_d \to \pi^+ \pi^-$ decays is also analyzed. We find that, among several
effects which may enhance the $B^0_d \to \pi^0 \pi^0$ branching ratio, the most
important is due to ``charming penguin" diagrams that have never been studied
before. These diagrams easily increase $BR(B^0_d \to \pi^0 \pi^0)$ up to a
value of $1-3 \times 10^{-6}$. The same effect produces, however, a large error
in the extraction of $\alpha$ from the measurement of the $B^0_d \to \pi^+
\pi^-$ time-dependent asymmetry. We show that it is possible to determine
charming-penguin amplitudes from the experimental measurement of many decay
rates. Their effect is impressive in $B^+ \to \pi^+ K^0$ and $B^0_d \to K^+
\pi^-$ decays, where charming-penguin contributions easily give values of
$BR(B^+ \to \pi^+ K^0)$ and $BR(B^0_d \to K^+ \pi^-)$ of about $1 \times
10^{-5}$. Among other possibilities, we also suggest to use $B^0_d \to K^0 \bar
K^0$, the BR of which can be as large as $2-3 \times 10^{-6}$, to determine the
size of charming-penguin amplitudes.


title: Can topological defects be formed during preheating ?

abstract:
  We study the dynamics of a scalar field \Phi with the potential
g(|\Phi|^2-\eta^2)^2/2 (g=self-coupling constant, \eta=symmetry breaking scale)
after inflation and make clear whether topological defects can ever be formed
during preheating. In particular, we pay attention to GUT defects (\eta \sim
10^{15}GeV - 10^{17}GeV), and consider three types of fluctuations. The first
one is produced due to parametric resonance, the second is due to the negative
curvature of the potential, and the last is created during inflation. We search
for the parameter region that nonthermal fluctuations of the scalar field
produced through the parametric resonant decay of its homogeneous part do not
lead to defect formation. We find that this region is rather wide, and the GUT
defects are not produced after inflation. This fact shows that the positiveness
of the effective mass square of the field and production of large fluctuations
whose amplitude is as large as that of homogeneous mode are not enough
conditions for full symmetry restoration.


title: Higgs Boson Production at the LHC

abstract:
  Recent theoretical progress in the evaluation of Higgs boson production at
the LHC within the Standard Model and its minimal supersymmetric extension is
reviewed. In particular the two-loop QCD corrections to the squark loop
contributions to scalar Higgs production in the MSSM and soft gluon resummation
effects in Standard and SUSY Higgs production via the gluon fusion mechanism
are discussed.


title:
Perturbative Part of the Non-Singlet Structure Function F_2 in the
  Large-N_F Limit

abstract:
  We have calculated $\bar{MS}$ Wilson coefficients and anomalous dimensions
for the non-singlet part of the structure function F_2 in the large-N_F limit.
Our result agrees with exact two and three loop calculations and gives the
leading N_F dependence of the perturbative non-singlet Wilson coefficients to
all orders in $\alpha_S$.


title: Asymptotic expansions of two-loop Feynman diagrams in the Sudakov limit

abstract:
  Recently presented explicit formulae for asymptotic expansions of Feynman
diagrams in the Sudakov limit are applied to typical two-loop diagrams. For a
diagram with one non-zero mass these formulae provide an algorithm for
analytical calculation of all powers and logarithms, i.e. coefficients in the
corresponding expansion $(Q^2)^{-2} \sum_{n,j=0} c_{nj} t^{-n} \ln^j t$, with
$t=Q^2/m^2$ and $j \leq 4$. Results for the coefficients at several first
powers are presented. For a diagram with two non-zero masses, results for all
the logarithms and the leading power, i.e. the coefficients $c_{nj}$ for n=0
and j=4,3,2,1,0 are obtained. A typical feature of these explicit formulae
(written through a sum over a specific family of subgraphs of a given graph,
similar to asymptotic expansions for off-shell limits of momenta and masses) is
an interplay between ultraviolet, collinear and infrared divergences which
represent themselves as poles in the parameter $\eps=(4-d)/2$ of dimensional
regularization. In particular, in the case of the second diagram, which is free
from the divergences, individual terms of the asymptotic expansion involve all
the three kinds of divergences resulting in poles, up to $1/\eps^4$, which are
successfully canceled in the sum.


title: Do the quark masses run? Extracting $m_b(m_Z)$ from LEP data

abstract:
  We present the first results of next-to-leading order QCD corrections to
three jet heavy quark production at LEP including mass effects. Among other
applications, this calculation can be used to extract the bottom quark mass
from LEP data, and therefore to test the running of masses as predicted by QCD.


title: Quark mass effects in QCD jets

abstract:
  The effects induced by the quark masses in three-jet observables have been
studied in this thesis. In particular, we have explored a new method: the study
of three-jet observables at LEP, different from QCD Sum Rules and Lattice
calculations, for determining the b-quark mass. Among other advantages, it
would allow to extract the b quark mass far from threshold, in contrast to the
other methods described above and it would provide a test of the QCD
Renormalization Group predictions. From our NLO calculation, we have estimated,
by exploring the $\mu$-dependence of our prediction at m_Z, a theoretical
b-quark mass uncertainty of at most 250(MeV) in the DURHAM algorithm, 300(MeV)
for JADE and EM and 500(MeV) for the E algorithm. Furthermore, quark mass
effects are expected to be quite more important in top production at NLC (Next
Linear Collider) and our calculation would be of a great interest.


title:
Dimensionally Regularized Box and Phase Space integrals involving gluons
  and massive quarks

abstract:
  The basic box and phase space integrals needed to compute at second order the
three-jet decay rate of the Z-boson into massive quarks are presented in this
paper. Dimensional Regularization is used to regularize the infrared
divergences that appear in intermediate steps. Finally, the cancellation of
these divergences among the virtual and the real contributions is showed
explicitly.


title: Yukawa Textures from Family Symmetry and Unification

abstract:
  In this letter, we show how the combination of both a gauged U(1)_X family
symmetry and an extended vertical gauge symmetry in a single model, allows for
the presence of additional Clebsch texture zeroes in the fermion mass matrices.
This leads to new structures for the textures, with increased predictivity, as
compared to schemes with enhanced family symmetries only. We illustrate these
ideas in the context of the Pati-Salam gauge group SU(4)xSU(2)_LxSU(2)_R$
supplemented by a U(1)_X gauged family symmetry. In the case of symmetric mass
matrices, two of the solutions of Ramond, Roberts and Ross that may not be
obtained by family symmetries only, are accurately reproduced. For
non-symmetric textures, new structures arise in models of this type. To
distinguish between the solutions in this latter case, we performed a numerical
fit to the charged fermion mass and mixing data. The best solution we found
allows a fit with a total chi^2 of 0.39, for three degrees of freedom.


title: Majorana Neutrinos and Gravitational Oscillation

abstract:
  We analyze the possibility of encountering resonant transitions of high
energy Majorana neutrinos produced in Active Galactic Nuclei (AGN). We consider
gravitational, electromagnetic and matter effects and show that the latter are
ignorable. Resonant oscillations due to the gravitational interactions are
shown to occur at energies in the PeV range for magnetic moments in the
$10^{-17} \mu_B$ range. Coherent precession will dominate for larger magnetic
moments. The alllowed regions for gravitational resonant transitions are
obtained.


title:
Spin-Dependent Twist-Four Matrix Elements from g_1 Data in the Resonance
  Region

abstract:
  Matrix elements of spin-dependent twist-four operators are extracted from
recent data on the spin-dependent g_1 structure function of the proton and
deuteron in the resonance region. We emphasize the need to include the elastic
contributions to the first moments of the structure functions at Q^2 < 2 GeV^2.
The coefficients of the 1/Q^2 corrections to the Ellis-Jaffe sum rules are
found to be 0.04 \pm 0.02 and 0.03 \pm 0.04 GeV^2 for the proton and neutron,
respectively.


title:
Decay Constant Ratios $f_{\eta_c}/f_{J/\psi}$ and
  $f_{\eta_b}/f_\Upsilon$

abstract:
  We calculate the decay constant ratios $f_{\eta_c}/f_{J/\psi}$ and
$f_{\eta_b}/f_\Upsilon$. In the calculation we take into account the mock meson
structures of the mesons, as well as the difference of the wave functions at
origin of the vector and pseudoscalar mesons studied by Ahmady and Mendel. We
find that the different spin structures of the mesons much affect the ratios.
We incorporate our results in the prediction of the branching ratios of $B\to K
\eta_c$.


title:
Wavefunction corrections and off-forward gluon distributions in
  diffractive $J/\psi$ electroproduction

abstract:
  Diffractive production of $J/\Psi$ particles by virtual photons on a proton
target is studied with a view towards understanding two important corrections
to the leading order result. First, the effect of Fermi motion of the heavy
quarks is studied by performing a systematic expansion in the relative
velocity, and a simple correction factor is derived. This is considerably less
than estimated previously. Second, since the kinematics necessarily requires
that non-zero momentum be transferred to the proton, off-forward gluon
distributions are probed by the scattering process. To estimate the importance
of the off-forwardness, we compute, in leading order perturbation theory, the
extent of deviation from the usual forward gluon distribution in a quark.


title: Soft interactions

abstract:
  Existing data on total cross sections, on elastic scattering at small,
moderate and large values of $t$, and on diffraction dissociation, reveal a
surprisingly simple phenomenology, but they throw up many questions for the LHC
to answer.


title:
Search for the scalar $a_0$ and $f_0$ mesons in the reactions
  $e^+e^-\to\gamma\pi^0\pi^0(\eta)$

abstract:
  It is shown that the reactions $e^+e^-\to\gamma\pi^0\pi^0(\eta)$ give a good
chance for observing scalar $a_0$ and $f_0$ mesons. In the photon energy region
less then 100 MeV the vector meson contributions $e^+e^-\to V^0\to\pi^0
V'^0\to\gamma\pi^0\pi^0(\eta)$ are negligible in comparison with the scalar
mesons $e^+e^-\to\phi\to\gamma f_0(a_0)\to\gamma\pi^0\pi^0(\eta)$ for
$BR(\phi\to\gamma f_0(a_0)\to\gamma\pi^0\pi^0(\eta))$ greater than
$5\cdot10^{-6}(10^{-5})$. Using two-channel treatment of the $\pi\pi$
scattering the predictions for $BR(\phi\to\gamma (f_0+\sigma)\to\gamma\pi\pi)$
are derived. The four quark model, the model of $K\bar K$ molecule and
the$s\bar s$ model of scalar $f_0$ and $a_0$ mesons are discussed.


title: The Gerasimov-Drell-Hearn sum rule and the infinite-momentum limit

abstract:
  We study the current-algebra approach to the Gerasimov-Drell-Hearn sum rule,
paying particular attention to the infinite-momentum limit. Employing the
order-alpha^2 Weinberg-Salam model of weak interactions as a testing ground, we
find that the legitimacy of the infinite-momentum limit is intimately connected
with the validity of the naive equal-times algebra of electric charge
densities. Our results considerably reduce the reliability of a recently
proposed modification of the Gerasimov-Drell-Hearn sum rule, originating from
an anomalous charge-density algebra.


title:
Like-Sign Dileptons at the Fermilab Tevatron Revisited in the Light of
  the HERA High-$Q^2$ Anomaly

abstract:
  We re-examine like-sign dilepton signals at the Fermilab Tevatron assuming
that the excess high-$Q^2$ events recently seen at HERA are due to scalar
resonances such as squarks of $R$-parity-violating supersymmetry. For gluinos
in the mass range of 200--350 GeV, the like-sign dilepton signal can help to
make the crucial distinction between the most favoured squark explanation and
other proposed solutions.


title: Higher Orders in the Colour-Octet Model of J/\psi Production

abstract:
  We study the hadro- and photo-production of $\bar cc$ and $\bar bb$ mesons at
low transverse momentum to high orders in the relative velocity of the pair, v,
in non-relativistic QCD. We evaluate cross sections to order v^7 for $\eta_c$,
sufficient for studies of photo-production in the almost-elastic region. For
all other charmonium states we find the cross section to order v^9, sufficient
for studies of the ratio of $\chi_{c1}$ and $\chi_{c2}$ production rates. We
find recurrence formulae for generating terms at even higher orders, should
they be needed.


title:
The electromagnetic effects in isospin symmetry breakings of q{\bar q}
  systems

abstract:
  The isospin symmetry breakings of q{\bar q} are investigated in the QCD sum
rule method. The electromagnetic effects are evaluated following the procedure
requiring that the electromagnetic effects for charged meson be gauge
invariant. We find that the electromagnetic effects are also dominant in the
isospin violations of rho meson, which have been shown to be the case in the
mass splittings of pions. The numerical results for the difference of pion
decay constants and the masses of rho mesons are presented, which are
consistent with the data.


title: Single leptoquark production at high-energy e+ e- colliders

abstract:
  A study of the production and the decay of scalar and vector leptoquarks at
high-energy e+ e- colliders is presented. All tree-order contributions to
single leptoquark production have been calculated and incorporated in the Monte
Carlo event generator ERATO-LQ.


title: Exotic Anti-Decuplet of Baryons: Prediction from Chiral Solitons

abstract:
  We predict an exotic Z^+ baryon (having spin 1/2, isospin 0 and strangeness
+1) with a relatively low mass of about 1530 MeV and total width of less than
15 MeV. It seems that this region of masses has avoided thorough searches in
the past.


title:
b-tau Unification and neutrino masses in SU(5) extensions of the MSSM
  with radiative electroweak symmetry breaking

abstract:
  We make a complete analysis of the Yukawa coupling unification in SU(5)
extensions of the MSSM in the framework of the radiative symmetry breaking
scenario. Both logarithmic and finite threshold corrections of sparticles have
been included in the determination of the gauge and Yukawa couplings at M_Z.
The effect of the heavy masses of each model in the renormalization group
equations is also included. We find that in the minimal SU(5) model b-tau
Yukawa unification can be achieved for too large a value of alpha_s. On the
other hand the Peccei-Quinn version of the Missing Doublet model, with the
effect of the right handed neutrino also included, exhibits b-tau unification
in excellent agreement with all low energy experimental data. Unification of
all Yukawa couplings is also discussed.


title: Four-Fermion Effective Interactions and Recent Data at HERA

abstract:
  We discuss the possibility of explaining the excess in the cross section at
high-Q^2 recently found at HERA in terms of four-fermion effective
interactions. To avoid the constraints from low-energy data, we select three
special cases in which the contact interaction is a product of vector-vector,
axial-axial and vector-axial currents. For these a satisfactory fit of HERA
data is possible, while keeping agreement with LEPII and CDF data, for an
interaction scale $\Lambda =3.5$ TeV. As the statistics of the experiments
improves-and if the effect persists-it will be soon possible to discriminate
between such contact terms and the alternative explanation in terms of
leptoquark exchange.


title:
Resurrection of Charge Symmetry Violation for <\rho^0 H_{em} \omega> ~
  5000 MeV^2

abstract:
  We review the theoretical predictions for \rho ^0-\omega mixing and conclude
in many ways that <\rho^0 H_{em} \omega>~ -5000 MeV^2, more in line with
earlier analyses of charge symmetry violation and with present data.


title:
Non-perturbative dynamics of the heavy-light quark system in the
  non-recoil limit

abstract:
  Starting from the relativistic gauge-invariant quark-antiquark Green function
we obtain the relevant interaction in the one-body limit, which can be
interpreted as the kernel of a non-perturbative Dirac equation. We study this
kernel in different kinematic regions, reproducing, in particular, for heavy
quark the potential case and sum rules results. We discuss the relevance of the
result for heavy-light mesons and the relation with the phenomenological Dirac
equations used up to now in the literature.


title:
From the Feynman-Schwinger representation to the non-perturbative
  relativistic bound state interaction

abstract:
  We write the 4-point Green function in QCD in the Feynman-Schwinger
representation and show that all the dynamical information are contained in the
Wilson loop average. We work out the QED case in order to obtain the usual
Bethe-Salpeter kernel. Finally we discuss the QCD case in the non-perturbative
regime giving some insight in the nature of the interaction kernel.


title: Contact Terms, Compositeness, and Atomic Parity Violation

abstract:
  The most severe constraints on quark-lepton four-fermion contact interactions
come from the agreement of atomic parity violation measurements with the
Standard Model. In this letter I note that for contact interactions which arise
in theories of composite quarks and leptons, other approximate global
symmetries than parity can eliminate the contribution of contact terms to
atomic parity violation. The most stringent tests of compositeness therefore
come from the high energy collider experiments at LEP II, HERA, and the
Tevatron.


title:
Forward-backward asymmetry in e+e- -> nu nubar Z from anomalous CP-odd
  WWZ couplings

abstract:
  Anomalous CP-odd W+W-Z couplings can give rise to a forward-backward
asymmetry in the Z angular distribution in the e+e- centre-of-mass frame in the
process e+e- -> nu nubar Z. Of the three CP-odd couplings possible, only the
imaginary part of one of the couplings, f_4^Z, which is C odd and P even,
contributes to the forward-backward asymmetry. It is found that a limit of the
order of 0.1 can be placed on this coupling at a Next Linear Collider with
centre-of-mass energy of 500 GeV and integrated luminosity of 50 fb^{-1}.


title: Future Directions in Higgs Phenomenology

abstract:
  The search for the weakly-coupled Higgs sector at future colliders consists
of three phases: discovery of a Higgs candidate, verification of the Higgs
interpretation of the signal, and precision measurements of Higgs sector
properties. The discovery of one Higgs boson with Standard Model properties is
not sufficient to expose the underlying structure of the electroweak symmetry
breaking dynamics. It is critical to search for evidence for a non-minimal
Higgs sector and/or new physics associated with electroweak symmetry breaking
dynamics.


title: Behavior of Neutrinos in Stochastic Magnetic Fields

abstract:
  If massive neutrinos possess magnetic moments, they can undergo spin flip in
a magnetic field. The magnetic fields needed for a meaningful measurement of
neutrino moments could be very high and may occur in astronomical objects such
as some supernovae or active galactic nuclei: they are typically chaotic ones.
We develop the general theory of the passage of neutrinos through such fields.
We also develop a simple model which becomes solvable in the high energy limit.
Both helicities occur with equal probability, independently of the initial
distribution. Observational consequences are discussed.


title: Charmonium in the instantaneous approximation

abstract:
  The charmonium system is studied in a Salpeter model with a vector plus
scalar potential. We use a kinematical formalism based on the one developed by
Suttorp, and present general eigenvalue equations and expressions for decay
observables in an onium system for such a potential both in the Feynman and
Coulomb gauges. Special attention is paid to the problem with renormalization
of the lepton pair decays, and we argue that they must be defined relative to
one of the experimental decay widths because renormalization of the vertex
function is not possible. The parameters of the model are determined by a fit
to the mass spectrum and the lepton pair decay rates. Two gamma decays and E1
and M1 transitions are then calculated and found to be well accounted for. No
significant differences in the results in Feynman or Coulomb gauge are found. A
comparison is made, regarding the electromagnetic transitions, between the full
and reduced Salpeter equation. A large difference is found showing the
importance of using the full Salpeter equation.


title: Small-x asymptotics of structure function g_2

abstract:
  Nonsinglet structure function g_2(x) for deep inelastic scattering of a
lepton on a constituent quark is calculated in the double logarithmic
approximation at x<<1. Small-x asymptotics of g_2 is shown to have the same
singular behaviour as asymptotics of the nonsinglet structure function g_1.


title: Lambda_c/Lambda_c-bar production asymmetries in pp and pi^- p collisions

abstract:
  We study Lambda_c/Lambda}_c-bar production asymmetries in pp and pi- p
collisions using a recently proposed two component model. The model includes
heavy baryon production by the usual mechanism of parton fusion and
fragmentation plus recombination of valence and sea quarks from the beam and
target hadrons. We compare our results with experimental data on asymmetries
measured recently.


title: Towards the Light Front Variables for High Energy Production Processes

abstract:
  Scale invariant presentation of inclusive spectra in terms of light front
variables is proposed. The variables introduced go over to the well-known
scaling variables x_F = 2p_z/sqrt(s) and x_T=2p_T/sqrt{s} in the high p_z and
high p_T limits respectively. So Some surface is found in the phase space of
produced pi-mesons in the inclusive reaction anti p p -> pi+- X at 22.4 GeV/c,
which separates two groups of particles with significantly different
characteristics. In one of these regions a naive statistical model seems to be
in a good agreement with data, whereas it fails in the second region. Key
words: Light front, inclusive, hadron-hadron, electron-positron, relativistic
heavy ions, deep inelastic.


title: The Standard Model Intermediate Mass Higgs Boson

abstract:
  We consider the phenomenology of the Standard Model intermediate mass Higgs
boson, $71 GeV < M_h < 2 M_W$. The motivation for a Higgs boson in this mass
region is emphasized. The branching ratios for the Higgs boson, including
electroweak and QCD radiative corrections, are presented, along with production
cross sections for $e^+e^-, \mu^+\mu^-, \gamma\gamma$, and hadronic
interactions. Search strategies are surveyed briefly.


title: Anomalous Couplings in e^+ e^- --> W^+ W^- gamma at LEP2 and NLC

abstract:
  We present sensitivity limits on the coefficients of a dimension-6 effective
Lagrangian that parametrizes the possible effects of new physics beyond the
Standard Model. Our results are based on the study of the process $e^+ e^- \to
W^+ W^- \gamma$ at LEP2 and NLC energies. In our calculations, we include all
the new anomalous interactions, involving vector and Higgs bosons, and take
into account the Standard Model irreducible background. We analyse the impact
of these new interactions on the total cross section, including the effects of
the initial electron and final W polarizations. We then focus on the operators
that will not be constrained by the $e^+ e^- \to W^+ W^-$ process, obtaining
limits based on the photon energy distribution.


title: Large-order Behaviour due to Ultraviolet Renormalons in QCD

abstract:
  Ultraviolet renormalons, contrary to their infrared counterparts, lead to a
universal contribution to the large-order behaviour of perturbative expansions
in QCD. In this letter, we determine nature of the leading ultraviolet
renormalon singularity for the inclusive hadroproduction cross section in $e^+
e^-$ annihilation, for hadronic $\tau$ decays and the moments of deep-inelastic
scattering structure functions. We comment on the relevance of ultraviolet
renormalons to estimates in low orders of perturbation theory.


title: B - L Mediated Supersymmetry Breaking

abstract:
  I present a realistic model of dynamical supersymmetry breaking, in which a
$U(1)_{B-L}$ gauge interaction communicates supersymmetry breaking to the
standard fields. A distinctive superpartner spectrum is predicted in this
model.


title: Weakly-Coupled Higgs Bosons and Precision Electroweak Physics

abstract:
  We examine the prospects for discovering and elucidating the weakly-coupled
Higgs sector at future collider experiments. The Higgs search consists of three
phases: (i) discovery of a Higgs candidate, (ii) verification of the Higgs
interpretation of the signal, and (iii) precision measurements of Higgs sector
properties. The discovery of one Higgs boson with Standard Model properties is
not sufficient to expose the underlying structure of the electroweak symmetry
breaking dynamics. It is critical to search for evidence for a non-minimal
Higgs sector and/or new physics associated with electroweak symmetry breaking
dynamics. An improvement in precision electroweak data at future colliders can
play a useful role in confirming the theoretical interpretation of the Higgs
search results.


title:
Precision observables in SU(2) x U(1) models with an additional Higgs
  triplet

abstract:
  Electroweak precision observables are calculated at complete 1-loop order in
the extension of the standard model by an extra Higgs triplet, where the
$\rho$-parameter can be different from unity already at the tree level. One
additional data point is required for fixing the input parameters. In the
on-shell renormalization scheme the leptonic mixing angle $\sin^2\theta_e$ at
the $Z$ peak is chosen, together with the conventional input $\alpha, M_Z,
G_{\mu}, m_t$. The calculated observables depend on the mass of the doublet
Higgs boson $H^0$ and on the masses of the extra non-standard Higgs bosons as
free parameters. The predictions of the standard model and the triplet model
coincide for all observables in the experimental range of the top mass
$m_t=175\pm 6$ GeV. In the triplet model, all observables which show a
dependence on the doublet Higgs mass $M_{H^0}$ are consistent with a low value
of $M_{H^0}$.


title: CP-Violation in b Quark Radiative Inclusive Decays

abstract:
  The direct CP-violations in $SU(2)_{L}\times SU(2)_{R} \times U(1)$ model and
two-Higgs doublet extension of the standard model for $b \to d\gamma$ and $b
\to s\gamma$ decays are investigated. The calculated value of CP-asymmetry for
these two models and for $b \to d\gamma$ and $b \to s\gamma$ decays for the
wide range of parameters may exceed the value, predicted by the standard model
and has a sign opposite to that of the latter.


title:
Cancellation of Leading Divergencies in Left-Right Electroweak Model and
  Heavy Particles

abstract:
  The fine-tuning principles are analyzed in search for estimations of heavy
particle masses in the left-right (LR) symmetric model. The modification of
Veltman condition based on the hypothesis of the compensation between fermion
and boson vacuum energies within the LR Model multiplets is proposed. The
hypothesis is supplied with the requirement of the stability under rescaling.
With regard to these requirements the necessity of existence of right-handed
Majorana neutrinos with masses of order of right-handed gauge bosons is shown
and estimations on the top-quark mass which are in a good agreement with the
experimental value are obtained.


title:
The hard scattering amplitude for the higher helicity components of the
  pion form factor

abstract:
  For obtaining the spin space wave function of the pion meson in the
light-cone formalism from the naive quark model, it is necessary to take into
account Wigner rotation. Consequently there are higher helicity
($\lambda_1+\lambda_2=\pm 1$) components in the light-cone spin space wave
function of the pion besides the usual helicity ($\lambda_1+\lambda_2=0$)
components. For the pion electromagnetic form factor, we calculate the
hard-scattering amplitude for the higher helicity components in the light-cone
perturbation theory. It is found that the hard-scattering amplitude for the
higher helicity components is of order $1/Q^4$, which is vanishingly small
compared to that of the ordinary helicity component at very high $Q^2$ but
should be considered in the $Q^2$ region where experimental data are available.


title:
Nuclear Effect in Higher-Dimensional Factorial Moment Analysis of the
  ^{16}O-, ^{32}S- and ^{197}Au-Em Interaction Data at 200, 60 and 11 A GeV/c

abstract:
  The anomalous behavior of 2-dimensional factorial moment in nucleus-nucleus
collisions is studied in some detail using both mini-bias and central collision
data of ^{16}O-, ^{32}S- and ^{197}Au-Em interactions from EMU01 experiment.
The correct value for the effective Hurst exponent in the analysis of
higher-dimensional factorial moment is found to be greater than unity, showing
clearly the existence of superposition effect in nucleus-nucleus collisions.


title: Isoscalar resonances with J^{PC}=1^{--} in e^+e^-annihilation

abstract:
  The analysis of the vector isoscalar excitations in the energy range between
1 and 2 GeV of the $e^+e^-$ annihilation is presented for the final states
$\pi^+\pi^-\pi^0$, $\omega\pi^+\pi^-$, $K^+K^-$, $K^0_SK^\pm\pi^\mp$ and
$K^{\ast0}K^-\pi^++ c.c$. The effects of both the resonance mixing and the
successive opening of multiparticle channels, with the energy dependent partial
widths, are taken into account. The work extends our previous analysis
hep-ph/9609216 of the vector isovector excitations and is aimed to compare the
existing data with the predictions of the $q\bar q$ model. It is shown that
this hypothesis does not contradict the data.


title: QCD at Finite Extension

abstract:
  A study of QCD at finite extension is presented and the relation to QCD at
finite temperature and in the infinite momentum frame is discussed. The
dynamics of Polyakov loops is investigated and shown to be described by
functional integrals with finite range of integration. Consequences of this
non-Gaussian form of the generating functional concerning the QCD vacuum,
gluonic excitations and confinement are discussed.


title: Coherent Photo- and Leptoproduction of Vector Mesons from Deuterium

abstract:
  We discuss the coherent photo- and leptoproduction of vector mesons from
deuterium at intermediate (virtual) photon energies, 3 GeV < nu < 30 GeV. These
processes provide several options to explore the space-time evolution of small
size quark-gluon configurations. Furthermore, we study the dependence of the
production cross section on the energy and momentum transfer t due to
variations of the finite longitudinal interaction length. Kinematic regions are
determined where the production cross section is most sensitive to the final
state interaction of the initially produced hadronic wave packet. For
unpolarized deuteron targets this double scattering contribution can be
investigated mainly at large values of the momentum transfer t. For polarized
targets kinematic windows sensitive to double scattering are available also at
moderate t. We suggest several methods for an investigation of color coherence
effects at intermediate energies.


title: Gyromagnetic Ratios of Bound Particles

abstract:
  A new approach to calculation of the binding corrections to the magnetic
moments of the constituents in a loosely bound system, based on the
Bargmann-Michel-Telegdi equation, is suggested. Binding corrections are
calculated in this framework, and the results confirm earlier calculations
performed by other methods. Our method clearly demonstrates independence of the
binding corrections on the magnitude of the spin of the constituents.


title:
$h^0\to W^+W^-\ra \ell^+\ell^{'-}\nu_\ell{\bar \nu}_{\ell'}$ as the
  Dominant SM Higgs Search Mode at the LHC for $M_{h^0}$= 155-180 GeV

abstract:
  We show that the Standard Model Higgs decay $h^0 \to W^+W ^- \to l^+ l^- \nu
{\bar\nu}$ is the most sensitive mode for SM Higgs searches in the range
155-180 GeV. The previously considered mode $h^0 \to Z^0 Z^{0*} \to l^+ l^-
l^+l^-$ has a significantly lower search sensitivity. We place particular
emphasis on two new cuts based on (i) the boost and (ii) the spin-correlation
of the $W^+W^-$-system. The distribution we obtain from our combined cuts shows
a mass sensitive peak which probably allows a mass determination to $\pm$ 5 GeV
for 5 fb^{-1}. This contribution complements our earlier published paper.


title: Higgs studies in polarized gamma-gamma collisions

abstract:
  The study of an intermediate mass Higgs boson, via the process gamma-gamma ->
H -> bbbar from an initiallypolarized J_z = 0 state, has been advocated as an
important feasible goal of a future photon linear collider. The crucial
argument was the m_b^2/s suppression of the background process gamma-gamma (J_z
= 0) -> bbbar. We critically review the contribution of the radiative
background processes (in which the m_b^2/s suppression is absent) to the
quasi-two-jet-like events with at least one, but preferably two, tagged
energetic b jets. Within a complete study of the radiative processes, we find
that a sizeable background contribution can come from the helicity-violating
gamma-gamma (J_z = 0) -> bbbar process accompanied by soft gluon emission.
These latter radiative corrections contain a new type of double logarithmic
(DL) terms. We clarify the physical nature of these novel DL corrections.
Despite the fact that the one-loop DL terms are comparable or even larger than
the Born term, fortunately we find that the calculation of the cross section in
the two-loop approximation is sufficient for a reliable evaluation of the
background to the Higgs signal.


title: Inverse Amplitude Method and Chiral Zeros

abstract:
  The inverse amplitude method has previously been successfully applied to
$\pi\pi$ scattering in order to extend the range of applicability of chiral
perturbation theory. However, in order to take the chiral zeros into account
systematically, the previous derivation of the inverse amplitude method has to
be modified. It is shown how this can be done to both one and two loops in the
chiral expansion. In the physical region, the inclusion of these chiral zeros
has very little significance, whereas they become essential in the
sub-threshold region. Finally, the crossing properties of the inverse amplitude
method are investigated in the sub-threshold region.


title:
Two-Loop Corrections to the Electromagnetic Vertex for Energies close to
  Threshold

abstract:
  Two-loop contributions to the electromagnetic form factors are calculated in
the kinematic regime close to the fermion-antifermion threshold. The results
are presented in an expansion in the velocity $\beta$ of the fermions in the
c.m. frame up to next-to-next-to leading order in $\beta$. The existence of a
new Coulomb singularity logarithmic in $\beta$, which is closely related to the
$O(\alpha^2\ln\alpha)$ corrections known from positronium decays, is
demonstrated. It is shown that due to this Coulomb singularity $O(\alpha^2)$
relativistic corrections to the non-relativistic cross section of heavy
fermion-antifermion pair production in $e^+e^-$ annihilation cannot be
determined by means of conventional multi-loop perturbation theory.


title: Testing Multiple Gluon Dynamics at the Tevatron

abstract:
  We propose the measurement of the ratio $R_{CSS}(Q_T^{\min}) \equiv
\frac{\sigma (Q_T>Q_T^{\min})}{\sigma _{Total}}$ to study the effects of the
multiple soft gluon radiation, predicted by QCD, on the transverse momentum
($Q_T$) distribution of the weak gauge bosons $W^{\pm }$ and $Z^0$ produced at
the Tevatron. We compare the prediction of the extended Collins-Soper-Sterman
resummation formalism with the next-to-leading and next-to-next-to-leading
order calculations. We show that both the rich dynamics of the QCD multiple
soft gluon radiation and the non-perturbative sector of QCD can be tested by
measuring $R_{CSS}$.


title:
Nucleon Vector Strangeness Form Factors: Multi-pion Continuum and the
  OZI Rule

abstract:
  We estimate the 3 \pi continuum contribution to the nucleon strange quark
vector current form factors, including the effect of a 3 \pi <----> \rho \pi
resonance. We find the magnitude of this OZI-violating contribution to be
comparable to that of typical OZI-allowed contributions. We also study the
isoscalar electromagnetic form factors, and find that the presence of a \rho
\pi resonance in the multi-pion continuum may generate an appreciable
contribution.


title: Implication of the Modified Gottfried Sum Rule

abstract:
  Implication of the modified Gottfried sum rule is discussed by focusing its
theoretical bases, the range of validity, and physical interpretation.


title:
Nonperturbative Explanation of the Enhancement Factors in QCD Sum Rule
  for the rho Meson

abstract:
  Taking the sum rule for the rho meson as an example, we study the possibility
of explaining the phenomenological enhamcement factors for certain terms in the
vacuum expectation value of the operator product expansion in the QCD sum rule.
We take a QCD motivated extended Nambu-Jona-Lasinio (ENJL) model as the low
energy effective Lagrangian for QCD with which we calculate the nonperturbative
contributions to the vacuum condensate expansion to obtain the enhancement
factors. Our result shows that such nonperturbative contributions can cause
large enough enhancement factors which can be consistent with the
phenomenological values.


title: Grand unification and heavy axion

abstract:
  We argue that sufficiently complex grand unified theories involving extra
strong intractions that confine at very short distances, may lead to a heavy
axion solution of the CP problem of QCD. This axion may have a mass within
accessible energy range, and its low energy interactions emerge through mixing
with axial Higgs boson(s). Another signature of this scenario is softly broken
Peccei-Quinn symmetry in the electroweak Higgs sector. We present a toy GUT
exhibiting these features.


title: CP violation from new quarks in the chiral limit

abstract:
  We characterize CP violation in the SU(2)xU(1) model due to an extra
vector-like quark or sequential family, giving special emphasis to the chiral
limit m_{u,d,s}=0. In this limit, CP is conserved in the three generation
Standard Model (SM), thus implying that all CP violation is due to the two new
CP violating phases whose effects may manifest either at high energy in
processes involving the new quark or as deviations from SM unitarity equalities
among imaginary parts of invariant quartets (or, equivalently, areas of
unitarity triangles). In our analysis we use an invariant formulation,
independent of the choice of weak quark basis or the phase convention in the
generalized Cabibbo-Kobayashi-Maskawa matrix. We identify the three weak-basis
invariants, as well as the three imaginary parts of quartets B_{1-3} which, in
the chiral limit, give the strength of CP violation beyond the SM. We find that
for an extra vector-like quark |B_i| <= 10^{-4}, whereas for an extra
sequential family |B_i| <= 10^{-2}.


title: Melosh Rotation and the Nucleon Tensor Charge

abstract:
  By making use of the effect of the Melosh rotation, we show that one can
estimate, in a simple way, the nucleon tensor charge in a relativistic quark
model formulated on the light-cone. We discuss the physical significance of our
results and compare them with those recently obtained in different
phenomenological models.


title: Constraints on the Higgs boson properties from the effective potential

abstract:
  We review the constraints on Higgs boson properties from effective potential
methods. In the Standard Model, the requirement of stability (or metastability)
of the standard electroweak minimum puts an upper bound on the scale of new
physics as a function of the Higgs mass. This upper bound is below the Planck
scale if the Higgs weights $\simlt$ 130 GeV. In supersymmetric extensions of
the Standard Model the former methods are useful to compute the Higgs mass
spectrum, and couplings, after resumming higher loop effects. In particular, if
the Higgs mass weights $\simgt$ 130 GeV, the minimal supersymmetric extension
of the Standard Model will be ruled out, while its non-minimal supersymmetric
extension containing singlets is only marginally allowed.


title: Conformal Phase Transition

abstract:
  The conception of the conformal phase transition (CPT), which is relevant for
the description of non-perturbative dynamics in gauge theories, is discussed.


title: Resummation of phi^4 free energy up to an arbitrary order

abstract:
  The consistency condition, which guarantees a well organized small-coupling
asymptotic expansion for the thermodynamics of massless $\phi^4$-theory, is
generalized to any desired order of the perturbative treatment. Based on a
strong conjecture about forbidden two-particle reducible diagrams, this
condition is derived in terms of functions of four-momentum in place of the
common toy mass in previous treatments. It has the form of a set of gap
equations and marks the position in the space of these functions at which the
free energy is extremal.


title:
Inelastic neutrino and antineutrino scattering on nuclei and
  ``strangeness'' of the nucleon

abstract:
  Possibilities to extract information on the strange form factors of the
nucleon from neutrino (antineutrino) inelastic scattering on nuclei, in an
energy range from 200 MeV to 1 GeV and more, are investigated in detail. All
calculations are performed within two relativistic independent particle models
(Fermi gas and shell model); the final state interactions of the ejected
nucleon are taken into account through relativistic optical model potentials.
We have shown that the values of the cross sections significantly depend on the
nuclear model (especially in the lower energy range). However the NC/CC
neutrino-antineutrino asymmetry in a medium--high energy range shows a rather
small dependence on the model and allows to disentangle different values of the
parameters that characterize the strange form factors. We have calculated also
the ratio of the cross sections for inelastic NC scattering of neutrinos on
nuclei, with the emission of a proton and of a neutron. Our calculations show
that this ratio depends rather weakly on the nuclear model and confirm previous
conclusions on the rather strong dependence of this ratio upon the axial
strange form factors.


title: Gluon Polarization in $e^+e^-\to t\bar tG$

abstract:
  We calculate the linear polarization of gluons radiated off top quarks
produced in e^+e^- annihilations. For typical top pair production energies at
the Next-Linear-Collider (NLC) the degree of linear polarization remains close
to its soft gluon value of 100% over almost the whole energy spectrum of the
gluon. The massive quark results are compared with the corresponding results
for the massless quark case.


title: Asymptotically Free Partons at High Energy

abstract:
  We describe the application of renormalization group improved perturbative
QCD to inelastic lepton-hadron scattering at high center-of-mass energy but
comparatively low photon virtuality. We construct a high energy factorization
theorem which complements the mass factorization theorem used for processes
with high virtualities. From it we derive a renormalization group equation
which resums all large logarithms at high energy, thereby extending to this
regime asymptotic freedom and thus the full range of perturbative computational
techniques. We discuss the solution of this equation in various limits, and in
particular show that the high energy behaviour of physical cross-sections is
consistent with phenomenological expectations and unitarity bounds.


title: Ultraviolet Renormalon at All Orders

abstract: This paper has been replaced by hep-ph/9908225.


title: Number of Electrons per Collision as a Quark-Gluon Plasma Signal

abstract:
  We investigate whether the total number of electrons per collision, as a
function of beam energy, is a potential quark-gluon-plasma (QGP) signature. At
high beam energies, we find that, after experimental removal of the noise
induced by Dalitz decays, the number of produced electrons is increased many
times fold from the existence of the QGP. The robustness of the potential
signal to differing theoretical assumptions makes it an attractive experimental
parameter.


title: Unpolarized and polarized quark distributions in the large-Nc limit

abstract:
  The isosinglet unpolarized and isovector polarized twist-2 quark
distributions of the nucleon at low normalization point are calculated in the
large-Nc limit. The nucleon is described as a soliton of the effective chiral
theory. We derive the expressions for the distribution functions in the
large-Nc limit starting from their definition as numbers of partons carrying
momentum fraction x in the infinite momentum frame. We develop a numerical
method for computation of the quark and antiquark distributions as sums over
the quark single-particle levels in the pion field of the soliton. The
contributions of the discrete bound-state level as well as the Dirac continuum
are taken into account. The quark- and antiquark distributions obtained
explicitly satisfy all general requirements. Results are in reasonable
agreement with parametrizations of the data at low normalization point.


title: String-Scale Baryogenesis

abstract:
  Baryogenesis scenarios at the string scale are considered. The observed
baryon to entropy ratio, $n_B /s \sim 10^{-10}$, can be explained in these
scenarios.


title: Non-Equilibrium Production of Photons via \pi^0\to 2\gamma in DCC's

abstract:
  We study production of photons via the non-equilibrium relaxation of a
Disoriented Chiral Condensate with the chiral order parameter having a large
initial amplitude along the \pi^0 direction. Assuming the validity of the low
energy coupling of the neutral pion to photons via the U_A(1) anomalous vertex,
we find that for large initial amplitudes along the \pi^0 direction, photon
production is enhanced by parametric amplification. These processes are
non-perturbative with a large contribution during the non-equilibrium stages of
the evolution and result in a distinct distribution of the produced photons and
a polarization asymmetry. For initial amplitudes of the \pi^0 component of the
order parameter between 200-400 MeV, corresponding to energy densities between
1-12 GeV/fm^3 we find a peak in the photon distribution at energies between
\approx 300 -600 MeV. We also find polarization asymmetries typically between
5-10%. We discuss the potential experimental impact of these results as well as
the problems associated with its detection.


title: Landau equations and asymptotic operation

abstract:
  The pinched/non-pinched classification of intersections of causal
singularities of propagators in Minkowski space is reconsidered in the context
of the theory of asymptotic operation as a first step towards extension of the
latter to non-Euclidean asymptotic regimes. A highly visual
distribution-theoretic technique of singular wave fronts is tailored to the
needs of the theory of Feynman diagrams. Besides a simple derivation of the
usual Landau equations in the case of the conventional singularities, the
technique naturally extends to other types of singularities e.g. due to linear
denominators in non-covariant gauges etc. As another application, the results
of Euclidean asymptotic operation are extended to a class of quasi-Euclidean
asymptotic regimes in Minkowski space.


title: Towards systematic near-threshold calculations in perturbative QFT

abstract:
  For any near-threshold asymptotic regime and for any Feynman diagram
(involving loop and/or phase space integrals), a systematic prescription for
explicitly constructing all-logs, all-powers (all-twists) expansions in
perfectly factorized form with explicit integrals for coefficients, is
presented. The distribution-theoretic nature of the method of asymptotic
operation employed allows treatment of totally exclusive phase space in the
same manner as loop integrals.


title: The Proton Spin Structure in a Light-Cone Qaurk-Spectator-Diquark Model

abstract:
  It is shown that the proton spin problem raised by the Ellis-Jaffe sum rule
violation does not in conflict with the SU(6) quark model, provided that the
relativistic effect from the quark transversal motions, the flavor asymmetry
between the $u$ and $d$ valence quarks, and the intrinsic quark-antiquark pairs
generated by the non-perturbative meson-baryon fluctuations of the nucleon sea
are taken into account. The meson-baryon fluctuations of the nucleon sea
provide a consistent picture for connecting the proton spin structure with a
number of other anomalies observed in the proton's structure, such as the
flavor asymmetry of the nucleon sea implied by the violation of the Gottfried
sum rule and the discrepancy between two different measurements of the strange
quark distributions in the nucleon sea.


title: 2/3 Splitting in SUSY GUT -- Higgs as Goldstone Boson

abstract:
  We briefly review the GIFT (Goltstones instead of Fine Tuning) mechanism
which provides a promising solution to the doublet-triplet splitting problem
and some other puzzles of the supersymmetric grand unification as are the
$\mu$-problem, the fermion mass problem, etc. It can be naturally implemented
by extending the minimal SUSY SU(5) model to the gauge SU(6) theory.


title:
QCD Corrections and the Leptoquark Interpretation of the HERA High Q^2
  Events

abstract:
  The excess of high-$Q^2$ events found by H1 and ZEUS at HERA in $e^+p$
deep-inelastic scattering above the Standard Model prediction motivates us to
calculate the NLO QCD corrections to the HERA scalar leptoquark (or squark)
production cross sections. We find that the corrections are significant, of
order 50% in the mass range of interest. We also calculate the leptoquark
average transverse momentum squared and find it to be rather small. Various
leptoquark production cross sections at the Tevatron $p \bar p$ collider are
also considered. We investigate in detail the leptoquark interpretation of the
HERA data. First we assume a minimal leptoquark model with a single diagonal
Yukawa coupling to first family lepton and quark mass eigenstates only. In this
case constraints from atomic parity violating experiments allow only isodoublet
scalar leptoquark production at HERA. This interpretation can be confirmed or
ruled out in the near future by high luminosity data at the Tevatron. The
Tevatron data already appear to rule out the vector leptoquark interpretation
of the HERA data. We also consider a more general model which allows for all
possible left-handed, right-handed, flavour and lepton number changing
couplings. The allowed values of the Yukawa couplings of this general model
offer several different interpretations of the data which are radically
different from the minimal model solutions. However these somewhat ad hoc tuned
solutions can easily be tested by future HERA experiments.


title: Unification or Compositeness?

abstract:
  The status of precision electroweak data, tests of the standard model,
determination of its parameters, and constraints on new physics, are surveyed.


title:
Non-relativistic effective theory for Quarkonium Production in Hadron
  Collisions

abstract:
  I review recent progress in understanding inclusive quarkonium production in
hadron collisions. The first part focuses on non-relativistic QCD as an
effective theory. I discuss its differences from and similarities with
effective theories describing bound states of a single heavy quark, as far as
matching calculations beyond tree-level and power counting are concerned. The
second part summarizes predictions for charmonium and bottomonium production at
collider and fixed target experiments and their comparison with data. The
emphasis here is on novel signatures due to color octet production,
polarization of quarkonia and the $\chi_1/\chi_2$ ratio in fixed target
collisions.


title: Discriminating New Physics Scenarios at NLC: The Role of Polarization

abstract:
  We explore the potential of the Next Linear Collider (NLC), operating in the
$e\gamma$ mode, to disentangle new physics scenarios on single $W$ production.
We study the effects related with the exchange of composite fermion in the
reaction $e\gamma \to W \nu_e$, and compare with those arising from trilinear
gauge boson anomalous couplings. We stress the role played by the initial state
polarization to increase the reach of this machine and to discriminate the
possible origin of the new phenomena.


title:
Supersymmetric $W$ Boson Decays as a Means to Search for Charginos and
  Neutralinos

abstract:
  If the sneutrino mass is below the chargino mass, the dominant decay mode of
the lightest chargino is via a two-body decay channel $\chi^{\pm}_1 \ra
\tilde{\nu} + l^{\pm}$. Sneutrinos are invisible in $R$-parity conserving
supersymmetric models and, if the mass gap $m(\chi^{\pm}_1)-m(\tilde{\nu})$ is
sufficiently small, the soft decay lepton may escape detection leading to
invisible chargino decays. This ``blind spot'' of the supersymmetry parameter
space would jeopardize the chargino search at LEP2. We point out that such a
scenario can be tested by searching for single $W$ events in $e^+e^- \ra
W^+W^-$, with one $W$ boson decaying to visible leptons or quark jets, and the
second $W$ boson decaying to invisible charginos and neutralinos.


title:
Leading-order analysis of the twist-3 space- and time-like cut vertices
  in QCD

abstract:
  We review the recent theoretical progress in the construction and solution of
the evolution equations which govern the scale dependence for the twist-three
structure and fragmentation functions of the nucleon.


title: Formation and Decay of Scalar Leptoquarks/Squarks in ep collisions

abstract:
  The cross sections for the formation of scalar resonances, leptoquarks or
squarks, in electron/positron-proton collisions at HERA are presented including
next-to-leading order QCD corrections. Depending mildly on the mass of the
resonances, the K-factors increase the production cross sections by up to 30%
if the target quarks are valence quarks. The QCD corrections to the partial
decay widths of leptoquarks/squarks to leptons and quarks are small. The
electron spectrum in the decays is softened nevertheless by perturbative gluon
radiation at a level of 3.4 GeV for a leptoquark/squark mass of 200 GeV.


title: Reconciling Supersymmetry and Left-Right Symmetry

abstract:
  We construct the minimal supersymmetric left-right theory and show that at
the renormalizable level it requires the existence of an intermediate $B-L$
breaking scale. The subsequent symmetry breaking down to MSSM automatically
preserves R-symmetry. Furthermore, unlike in the nonsupersymmetric version of
the theory, the see-saw mechanism takes its canonical form. The theory predicts
the existence of a triplet of Higgs scalars much lighter than the $B-L$
breaking scale.


title:
Electron Electric Dipole Moment from CP Violation in the Charged Higgs
  Sector

abstract:
  The leading contributions to the electron (or muon) electric dipole moment
due to CP violation in the charged Higgs sector are at the two-loop level. A
careful analysis of the model-independent contribution is provided. We also
consider specific scenarios to demonstrate how charged Higgs sector CP
violation can naturally give rise to large electric dipole moments. Numerical
results show that the electron electric dipole moment in such models can lie at
the experimentally accessible level.


title:
Supersymmetry with R-Parity Breaking: Contact Interactions and Resonance
  Formation in Leptonic Processes at LEP2

abstract:
  In supersymmetric theories with R-parity breaking, trilinear couplings of two
leptons to scalar sleptons are possible. In electron-positron collisions such
interactions would manifest themselves through contact terms in Bhabha
scattering and in annihilation to mu or tau pair Interpreting the high x, high
Q2 DIS HERA events as charm squark production with squark masses of order 200
GeV, the formation of tau sneutrinos with a mass in the range close to the LEP2
energy or even in reach, is an exciting speculation which can be investigated
in the coming LEP2 runs with energies close to 200 GeV.


title: Key Distributions for Charmless Semileptonic B Decay

abstract:
  We present theoretical predictions for a few phenomenologically interesting
distributions in the semileptonic b->u decays which are affected by Fermi
motion. The perturbative effects are incorporated at the one-loop level and
appear to be very moderate. Our treatment of Fermi motion is based directly on
QCD, being encoded in the universal distribution function F(x). The decay
distributions in the charged lepton energy, invariant mass of hadrons, hadron
energy, and q^2 are given. We note that typically about 90% of all decay events
are expected to have M_X < M_D; this feature can be exploited in determination
of |V_ub|.


title: Prompt J/psi production at e^+e^- colliders

abstract:
  In this paper, we discuss the prompt j/psi production at e^+e^- colliders via
color-singlet and color-octet production mechanisms. The color-singlet
production processes include 1) e^+e^- to J/\psi gg; 2) e^+e^- to J/\psi
c\bar{c}; 3) e^+e^- to q \bar q ggJ/\psi and e^+e^- to q \bar q g\chi_c
followed by \chi_c to J/\psi \gamma. The color-octet production processes
include 1) e^+e^- to J/\psi g; 2) e^+e^- to j/psi q\bar q. Of all these
production channels, we find that the color-octet contributions dominate over
the color-singlet contributions at any energy scales. At low energies
(\sqrt{s}< 20 GeV), the dominant channel is e^+e^- to J/\psi g whereas at high
energies e+e^- to j/psi q\bar q will take the leading part. We also find that
the energy spectrum for the color-octet j/psi production in process e^+e^- to
j/psi q\bar q is very soft, and the mean energy of the produced j/psi is only
about 10 GeV~ 20 GeV even at very high energies (e.g. at 1000 GeV). The
extraction of color-octet matrix elements from j/psi production in e^+e^-
collisions is also discussed.


title: Calculations of penguin diagrams in B decays

abstract:
  We analyze the effects of the space-like penguin diagrams in two body B
decays $B^-\to K^-{\bar K}^0$ and $B^-\to \pi^-{\bar K}^0$. Special attention
is paid to the operator $Q_6$, whose contribution is large in the BSW model,
but vanishes in the PQCD method in the approximation of neglecting the masses
in the final states. Suppressions of the space-like penguin diagrams are found
in the PQCD method, which implies that the contributions of the space-like
penguins are small compared to those of the time-like penguins.


title:
Comment on: ``Search for direct photons from S-Au Collisions at 200
  GeV/nucleon'' by the CERES Collaboration

abstract:
  In this note we comment on a recent publication in this journal by the CERES
(NA45) Collaboration. The authors report to have determined an upper limit on
the direct photon yield relative to the decay photon yield in S+Au collisions
of 14 % and 7 % by two different methods, respectively. We argue that these
limits are unsupported by the results and analysis of the CERES data. The
systematic error estimates quoted in the CERES analysis are consistently overly
optimistic. Using more realistic estimates of the various error contributions
and propagating them appropriately we arrive at a direct photon upper limit
which at best is 20% of the inclusive photon yield, and most probably is much
higher.


title:
Same-sign dileptons as a signature for heavy Majorana neutrinos in
  hadron-hadron collisions

abstract:
  We discuss the possibility of same-sign dileptons as a signature for Majorana
neutrinos. The production mechanism is given by a single heavy neutrino
production and decay proton-proton -> l^{\pm} N X -> l^{\pm} l^{\pm} X'. Cross
section and distributions are presented for the LHC energies.


title: Supersymmetry and FCNC effects

abstract:
  We consider Flavour Changing Neutral Current processes in the framework of
the supersymmetric extension of the Standard Model. FCNC constraints on the
structure of sfermion mass matrices are reviewed. Furthermore, we analyze
supersymmetric contributions to FCNC transitions which remain in the limit of
flavour-conserving sfermion mass matrices. Implications of the FCNC constraints
on the structure of sfermion mass matrices for SUSY breaking and sfermion mass
generation are discussed. We conclude that the supersymmetric flavour problem
is intriguing but perhaps not as severe as it is commonly believed.


title: Hybrid Inflation with Quasi-canonical Supergravity

abstract:
  We construct a hybrid inflationary model associated with the superheavy scale
of the minimal supersymmetric standard model which is based on the simplest
superpotential for symmetry breaking and in which the inflaton potential along
the inflationary trajectory is essentially provided by quasi-canonical
supergravity. The resulting spectrum of adiabatic density perturbations is blue
and the duration of inflation sufficient but rather limited.


title: R-Parity Violating Supersymmetry at HERA

abstract:
  The phenomenology and prospects for a discovery of R-parity violating
Supersymmetry at HERA are analysed. Emphasis is put on the direct resonant
production of squarks by electron-quark fusion and all possible subsequent
decay modes of the squarks are considered. In particular, the full consequences
of the mixing in the supersymmetric gaugino-higgsino sector are taken into
account. A rich phenomenology emerges for HERA which offers a unique
sensitivity to new R-parity violating couplings and good discriminating power
against free parameters of the theory.


title: A unified BFKL and GLAP description of $F_2$ data

abstract:
  We argue that the use of the universal unintegrated gluon distribution and
the $k_T$ (or high energy) factorization theorem provides the natural framework
for describing observables at small x. We introduce a coupled pair of evolution
equations for the unintegrated gluon distribution and the sea quark
distribution which incorporate both the resummed leading $ln (1/x)$ BFKL
contributions and the resummed leading $ln (Q^2)$ GLAP contributions. We solve
these unified equations in the perturbative QCD domain using simple parametic
forms of the nonperturbative part of the integrated distributions. With only
two (physically motivated) input parameters we find that this $k_T$
factorization approach gives an excellent description of the measurements of
$F_2 (x,Q^2)$ at HERA. In this way the unified evolution equations allow us to
determine the gluon and sea quark distributions and, moreover, to see the x
domain where the resummed $ln (1/x)$ effects become significant. We use $k_T$
factorization to predict the longitudinal structure function $F_L (x,Q^2)$ and
the charm component of $F_2 (x,Q^2)$.


title:
Signatures of CP-violation in $\gamma \gamma \to H$ using polarized
  beams

abstract:
  The possibility of observing CP-violation in the process $\gamma \gamma \to
H$ is investigated for masses of the Higgs particle in the interval $M_z \lsim
m_H \lsim 2 m_t$, using a 0.5TeV tunable linear $e^{+} e^{-}$ collider through
laser backscattering. The use of polarized beams allows the formation of two
different asymmetries sensitive to CP-violating New Physics (NP) interactions
among the gauge and Higgs bosons. It is shown that very low values of the
corresponding NP couplings can be probed, for a large range of the Higgs mass.


title:
Comment on the Burkhardt - Cottingham and Generalized
  Gerasimov-Drell-Hearn Sum Rules for the neutron

abstract:
  A description of the generalized Gerasimov-Drell-Hearn sum rule for neutron
is suggested, using its relation to the Burkhardt-Cottingham sum rule.


title:
Comment on the Prediction of Two-loop Standard Chiral Perturbation
  Theory for Low-Energy \pi\pi Scattering

abstract:
  Four of the six parameters defining the two-loop \pi\pi scattering amplitude
have been determined using Roy dispersion relations. Combining this information
with the Standard \chi PT expressions, we obtain the threshold parameters,
low-energy phases and the O(p^4) constants $l_1^r, l_2^r$. The result $l_2^r (
M_{\rho} ) = ( 1.6 \pm 0.4 \pm 0.9 ) \times 10^{-3} ( {\bar l_2} = 4.17 \pm
0.19 \pm 0.43$) reproduces the correct D-waves but it is incompatible with
existing Standard \chi PT analyses of $K_{l4}$ form factors beyond one loop.


title:
Nondiagonal Parton Distributions in the Leading Logarithmic
  Approximation

abstract:
  In this paper we make predictions for nondiagonal parton distributions in a
proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA,
solve the nondiagonal GLAP evolution equations with a modified version of the
CTEQ-package and comment on the range of applicability of the LLA in the
asymmetric regime. We show that the nondiagonal gluon distribution
$g(x_{1},x_{2},t,\mu^2)$ can be well approximated at small $x$ by the
conventional gluon density $xG(x,\mu^2)$.
  Keywords: Hard Diffractive Scattering, Nondiagonal distributions, Evolution


title:
Direct Top Quark Production at Hadron Colliders as a Probe of New
  Physics

abstract:
  We examine the effect of an anomalous flavor changing chromomagnetic moment
which allows direct top quark production (two partons combining into an
unaccompanied single top quark in the s-channel) at hadron colliders. We
consider both t-c-g and t-u-g couplings. We find that the anomalous charm quark
coupling parameter $\kappa_c / \Lambda$ can be measured down to $.06
TeV^{-1}(.009 TeV^{-1}$) at the Tevatron with the Main Injector upgrade(LHC).
The anomalous up quark coupling parameter $\kappa_u / \Lambda$ can be measured
to $.02 TeV^{-1}(.003 TeV^{-1}$) at the Tevatron(LHC).


title: Nonperturbative Renormalization in Light-Cone Quantization

abstract:
  Two approaches to nonperturbative renormalization are discussed for theories
quantized on the light cone. One is tailored specifically to a calculation of
the dressed-electron state in quantum electrodynamics, where an invariant-mass
cutoff is used as a regulator and a Tamm-Dancoff truncation is made to include
no more than two photons. The other approach is based on Pauli-Villars
regulators and is applied to Yukawa theory and a related soluble model. In both
cases discretized light-cone quantization is used to obtain a finite matrix
problem that can be solved nonperturbatively.


title: Higgs Boson Decays into Light Gravitinos

abstract:
  We study decays of the neutral and charged Higgs bosons of the minimal
supersymmetric standard model into a very light gravitino and a neutralino or
chargino. Present experimental constraints already imply that the lighter
scalar Higgs boson can only have a very small branching ratio into this mode.
However, if the gravitino mass is below $\sim 0.5$ eV, the heavier neutral and
charged Higgs boson decays into a gravitino can be important or even dominant.
We discuss the resulting signature for associate production of the heavy
CP-even and the CP-odd states at future $e^+ e^-$ colliders, and comment on
Higgs boson production at hadron colliders.


title: Mean Charge of the Light Sea Quarks in the Proton

abstract:
  The modified Gottfried sum rule multiplied by 3/2 can be interpreted as the
one to measure the mean $I_3$ of the [(quark) - (antiquark)] in the proton .
Based on this interpretation we find the sum rule which can be understood as
the one to measure the mean charge of the light sea quarks (u,d,s) in the
proton, and show that it takes the value 0.23 for the proton and 0.34 for the
neutron .


title: Comments on Neutrino Tests of Special Relativity

abstract:
  We point out that the assumption of Lorentz noninvariance examined recently
by Coleman and Glashow leads to neutrino flavor oscillations which are
phenomenologically equivalent to those obtained by assuming the neutrinos
violate the principle of equivalence. We then comment on the limits on Lorentz
noninvariance which can be derived from solar, atmospheric, and accelerator
neutrino experiments.


title:
The Extraction of Light Quark Masses From Sum Rule Analyses of Axial and
  Vector Current Ward Identities

abstract:
  We re-examine the use of sum rules in the extraction of light quark masses
and discuss a number of potential problems with existing analyses. The most
important issue is that of the overall normalization of the hadronic spectral
functions should not be fixed by assuming complete resonance dominance of the
continuum threshold region as it can overestimate the resonance contributions
to spectral integrals by factors as large as $\sim 5$. The second important
uncertainty comes from the assumed location, $s_0$, of the onset of duality
with perturbative QCD, as the extracted quark masses depend very sensitively on
this parameter. The assumption of duality and the requirement of positivity of
$\rho_5(s)$ imposes very severe constraints on the shape of the relevant
spectral function in the dual region, and leads to rigorous lower bounds for
$m_u+m_d$ as a function of $s_0$. In the extractions of $m_s$ we find that the
conventional choice of the value of $s_0$ is not physical. For a more
reasonable choice of $s_0$ we are not able to find a solution that is stable
with respect to variations of the Borel transform parameter. This problem can
be overcome only if the hadronic spectral function is determined up to
significantly larger values of $s$ than is currently possible. Finally, we also
estimate the error associated with the convergence of perturbative QCD
expressions used in the sum rule analyses. Our conclusion is that, taking all
of these issues into account, the resulting sum rule estimates for both
$m_u+m_d$ and $m_s$ could easily have uncertainties as large as a factor of 2.


title:
Radiative corrections for pion and kaon production at $e^+e^-$ colliders
  of energies below 2 GeV

abstract:
  Processes of electron-positron annihilation into charged pions and kaons are
considered. Radiative corrections are taken into account exactly in the first
order and within the leading logarithmic approximation in higher orders. A
combined approach for accounting exact calculations and electron structure
functions is used. An accuracy of the calculation can be estimated about 0.2%.


title:
Electroweak baryon and lepton number violating processes at high
  energies by the valley instanton

abstract:
  We calculate the cross sections of the baryon and lepton number violating
processes. The proper valley method enables us to calculate the multi-boson
processes, which have the possibility to observation. The mass corrections of
the gauge boson, Higgs particle and top quark are evaluated and the group
integration and the phase space integration are performed analytically and
numerically.


title: CP-violating Signals in the First-round Experiments of a B-meson Factory

abstract:
  Determination of the characteristic CP-violating quantity \sin (2\beta)
should be the central goal of a B-meson factory in its first-round experiments.
Except the gold-plated channels B_d\to \psi K_S and \psi K_L, three other types
of B_d decays to CP eigenstates can also serve for the extraction of \sin
(2\beta) in the standard model: (a) the CP-forbidden transitions
(B_d\bar{B}_d)_{\Upsilon (4S)} \to (X_c K_S) (X_c K_S) and $(X_c K_L) (X_c
K_L), where X_c = \psi, \psi', \eta_c, etc; (b) the decay modes B_d\to
D^{(*)+}D^{(*)-} and D^{(*)0}\bar{D}^{(*)0}, whose amplitudes have simple
isospin relations; and (c) the decay modes B_d\to (f_{CP})_D + (\pi^0, \rho^0,
a^0_1, etc), in which f_{CP} is a CP eigenstate (such as \pi^+\pi^-, K^+K^- or
K_S \pi^0) arising from either D^0 or \bar{D}^0 in the neglect of D^0-\bar{D}^0
mixing. We carry out an analysis of the CP-violating signals existing in these
typical processes, without loss of the possibility that new physics might
significantly affect B^0_d-\bar{B}^0_d or K^0-\bar{K}^0 mixing. We also show
that the magnitude of \sin (2\beta) can be well determined, in terms of only
|V_{us}|, m_d/m_s and m_u/m_c, from a variety of quark mass ansatze.


title: Possible Signals of D^0-\bar{D}^0 Mixing and CP Violation

abstract:
  In view of the discovery potential associated with the future experiments of
high-luminosity fixed target facilities, B-meson factories and \tau-charm
factories, we highlight some typical signals of D^0-\bar{D}^0 mixing and CP
violation which are likely to show up in neutral D-meson decays to the
semileptonic final states, the hadronic CP eigenstates, the hadronic non-CP
eigenstates and the CP-forbidden states. Both time-dependent and
time-integrated measurements are discussed, and particular interest is paid to
D^0/\bar{D}^0 \to K_{S,L}+\pi^0 and D^0/\bar{D}^0\to K^{\pm}\pi^{\mp}
transitions.


title:
HERA high $Q^2$ events as indications of excited leptons with weak
  isotopic spin 3/2

abstract:
  The H1 and ZEUS anomalous events are interpreted as being due to the
production and the decay of excited leptons $E$, which correspond to spin 1/2
resonances of the first generation lepton doublet ($\nu_e, e$) with W triplet.
This assumption is supported by considering of Bethe-Salpeter equation in the
ladder approximation with anomalous triple gauge boson vertex. The solution
with weak isospin $I = 3/2$ is shown to exist for zero mass state, that means
M_E$ is small in comparison with TeV mass scale. The coupling of $E$ with
leptons and $W$ is defined by the normalization condition. Calculation of the
$E$ width and the production cross-sections agrees with HERA data for value of
the triple $W$ coupling constant $\lambda \simeq 0.5$. Isotopic relations for
different channels are presented as a tool for checking the interpretation.


title: Measure of the size of CP violation in extended models

abstract:
  In this letter we introduce a possible measure of the size of CP violation in
the Standard Model and its extensions, based on quantities invariant under the
change of weak quark basis. We also introduce a measure of the ``average size''
of CP violation in a model, which can be used to compare the size of CP
violation in models involving extra sequential or vector-like quarks, or
left-right symmetry.


title: Physics at ELFE

abstract:
  I review some central physics opportunities at the 15 ... 30 GeV continuous
beam electron accelerator ELFE, proposed to be built in conjunction with the
DESY linear collider. Our present detailed knowledge of single parton
distributions in hadrons and nuclei needs to be supplemented by measurements of
compact valence quark configurations, accessible through hard exclusive
scattering, and of compact multiparton subsystems which contribute to
semi-inclusive processes. Cumulative (x>1, x_F>1) processes in nuclei measure
short-range correlations between partons belonging to different nucleons in the
same nucleus. The same configurations may give rise to subthreshold production
of light hadrons and charm. The challenges of understanding high energy
charmonium production indicate that charmonium will be a sensitive probe of
color dynamics at ELFE. At low energies, charmonium forms inside the target
nucleus, allowing a determination of $c\bar c$ bound state interactions in
nuclear matter.


title:
Dimension-six CP-violating operators of the third-family quarks and
  their effects at colliders

abstract:
  We listed all possible dimension-six CP-violating $SU_c(3)\times
SU_L(2)\times U_Y(1)$ invariant operators involving the third-family quarks,
which can be generated by new physics at a higher energy scale. The expressions
of these operators after electroweak symmetry breaking and the induced
effective couplings $Wt\bar b$, $Xb\bar b$ and $Xt\bar t$ $(X=Z,\gamma,g,H)$
are also presented. We have evaluated sample contributions of these operators
to CP-odd asymmetries of transverse polarization of top quark in single top
production at the upgraded Tevatron, the similar effect in top-antitop pair
production at the NLC, and the CP-odd observables of momentum correlations
among the top quark decay products at the NLC. The energy and luminosity
sensitivity in probing these CP-violating new physics has also been studied.


title: CPT Violation and the Standard Model

abstract:
  Spontaneous CPT breaking arising in string theory has been suggested as a
possible observable experimental signature in neutral-meson systems. We provide
a theoretical framework for the treatment of low-energy effects of spontaneous
CPT violation and the attendant partial Lorentz breaking. The analysis is
within the context of conventional relativistic quantum mechanics and quantum
field theory in four dimensions. We use the framework to develop a
CPT-violating extension to the minimal standard model that could serve as a
basis for establishing quantitative CPT bounds.


title: Neutrino - Modulino Mixing

abstract:
  We suggest the existence of a light singlet fermion, $S$, which interacts
with observable matter only via a Planck mass suppressed interaction: $\sim
m_{3/2}/M_P$, where $m_{3/2}$ is the supergravity gravitino mass. If the mass
of the singlet equals $\sim m_{3/2}^2/M_P$, then $\nu_e \to S$ resonance
conversion solves the solar neutrino problem or leads to observable effects.
The $\nu S$-mixing changes supernova neutrino fluxes and has an impact on the
primordial nucleosynthesis. The singlet $S$ can originate as the supersymmetric
partner of the moduli fields in supergravity or low energy effective theory
steaming from superstrings. The $\nu S$-mixing may be accompanied by observable
R-parity breaking effects.


title:
Classical Gluon Radiation in Ultrarelativistic Nucleus-Nucleus
  Collisions

abstract:
  The classical Yang-Mills equations are solved perturbatively in covariant
gauge for a collision of two ultrarelativistic nuclei. The nuclei are taken as
ensembles of classical color charges on eikonal trajectories. The classical
gluon field is computed in coordinate space up to cubic order in the coupling
constant g. We construct the Feynman diagrams corresponding to this field and
show the equivalence of the classical and diagrammatic approaches. An argument
is given which demonstrates that at higher orders in g the classical
description of the process breaks down. As an application, we calculate the
energy, number, and multiplicity distributions of produced soft gluons and
reproduce earlier results by Gunion and Bertsch and by Kovner, McLerran, and
Weigert.


title:
Constraints on neutrino parameters and doubly charged Higgs particles in
  the $e^-e^- \to W^-W^-$ process

abstract:
  Doubly charged Higgs s-channel resonances are analyzed in the $e^-e^- \to
W^-W^-$ process. In our analysis recent stringent constraint on an effective
neutrino mass $<m_{\nu}>$ coming from neutrinoless double-$\beta$ decay is
implemented. It is shown that due to a very restrictive limit on $<m_{\nu}>$
the doubly charged Higgs resonance predicted by the Standard Model with
additional Higgs triplets is below the detection limit. For the same reason
also the $\Delta_L^{--}$ resonance can not be visible in the framework of the
conventional Left-Right symmetric model. The situation is quite different for
the $\Delta_R^{--}$ pole and large signal is possible here. Contributions of
the s, t and u channels to the cross section around the $\Delta_R^{--}$ peak
are also discussed.


title: Charm production in deep inelastic and diffractive scattering

abstract:
  We consider the production of charm by real and virtual photons. Special
attention is paid to diffractive charm production, which provides information
on the gluonic content of the Pomeron. Our calculations are based on the gluon
distributions of the CKMT-model, which is shown to lead to agreement with the
data on open charm production in deep inelastic scattering. We compare
predictions for diffractive charm production of different models for the
distribution of gluons in the Pomeron. Experiments at HERA should be able to
discriminate between them. Predictions for beauty production in diffractive and
non-diffractive interactions of photons are also given.


title:
Sensitivity to a new right-handed charged current in polarized hadronic
  collisions at RHIC

abstract:
  In the context of general $SU(2)_L\otimes SU(2)_R\otimes U(1)$ models a
relatively light W' is still allowed in some scenarios with a heavy
right-handed neutrino and a quark mixing matrix $U^R$ close to unity. We
explore the consequences of the presence of this new charged current on the
parity violating spin asymmetries which could be induced in one-jet inclusive
production in polarized proton-proton or proton-neutron collisions. Such
measurements could be performed within a few years at the Brookhaven
Relativistic Heavy Ion Collider (RHIC) running part of the time as a polarized
hadronic collider.


title: CP Violation from Slepton Oscillations at the LHC and NLC

abstract:
  In supersymmetric theories the charged sleptons of different generations may
oscillate amongst themselves while they decay. In the case of three generation
oscillations, superpartner production at the LHC and NLC may lead to an
observable $CP$-violating signal $N(e^+\mu^-) - N(\mu^+e^-)$. This signal is
proportional to a $CP$-violating invariant of the slepton mass matrix,
$\widetilde{J}$, which is not constrained by searches for the electric dipole
moment of the electron. The sensitivity of the LHC and NLC to this signal is
highly dependent on superpartner masses, but $\widetilde{J}$ may be probed to a
level of $10^{-3}$. Observation of the $CP$-violating signal would imply a
definite structure for the slepton mass matrices and have strong implications
for models of flavor and SUSY breaking.


title:
Improving the Fine Tuning in Models of Low Energy Gauge Mediated
  Supersymmetry Breaking

abstract:
  The fine tuning in models of low energy gauge mediated supersymmetry breaking
required to obtain the correct $Z$ mass is quantified. To alleviate the fine
tuning problem, a model with split $(5+\bar{5})$ messenger fields is presented.
This model has additional triplets in the low energy theory which get a mass of
$O(500)$ GeV from a coupling to a singlet. The improvement in fine tuning is
quantified and the spectrum in this model is discussed. The same model with the
above singlet coupled to the Higgs doublets to generate the $\mu$ term is also
discussed. A Grand Unified version of the model is constructed and a known
doublet-triplet splitting mechanism is used to split the messenger
$(5+\bar{5})$'s. A complete model is presented and some phenomenological
constraints are discussed.


title: Nonforward Parton Distributions

abstract:
  Applications of perturbative QCD to deeply virtual Compton scattering and
hard exclusive electroproduction processes require a generalization of usual
parton distributions for the case when long-distance information is accumulated
in nonforward matrix elements <p'|O|p> of quark and gluon light-cone operators.
We describe two types of nonperturbative functions parametrizing such matrix
elements: double distributions F(x,y;t) and nonforward distribution functions
F_\zeta (X;t), discuss their spectral properties, evolution equations which
they satisfy, basic uses and general aspects of factorization for hard
exclusive processes.


title: The $K_L \to \pi^0 \nu \bar\nu$ Decay Beyond the Standard Model

abstract:
  The $K_L \to \pi^0 \nu \bar\nu$ decay is analyzed in a model independent way.
When lepton flavor is conserved, this decay mode is a manifestation of CP
violating interference between mixing and decay. Consequently, a theoretically
clean relation between the measured rate and electroweak parameters holds in
any given model.


title:
Top quark pair production via polarized and unpolarized photons in
  Supersymmetric QCD

abstract:
  QCD corrections to top quark pair production via fusion of both polarized and
unpolarized photons are calculated in Supersymmetric Model. The corrections are
found to be sizable. The dependence of the corrections on the masses of the
supersymmetric particles is also investigated. Furthermore, we studied CP
asymmetry effects arising from the complex couplings in the MSSM. The CP
violating parameter can reach $10^{-2}$ for favorable parameter values.


title: Classical antiparticles

abstract:
  We review how antiparticles may be introduced in classical relativistic
mechanics, and emphasize that many of their paradoxical properties can be more
transparently understood in the classical than in the quantum domain.


title: Mass of tau neutrino in SO(10) GUT-s

abstract:
  We investigate the allowed ranges of masses for an unstable tau neutrino in
the context of SO(10) GUT-s. In light of the new nucleosynthesis results we
obtain that there is a narrow window for m_{\nu_\tau} where the LEP, neutrino
oscillation and nucleosynthesis data are compatible. This window, which depends
on the effective number of neutrinos contributing to nucleosynthesis, has
important cosmological consequences and will be tested by ongoing neutrino
oscillation and LEP II experiments.


title: Vector Meson Masses in Chiral Perturbation Theory

abstract:
  We discuss the vector meson masses within the context of Chiral Perturbation
Theory performing an expansion in terms of the momenta, quark masses and 1/Nc.
We extend the previous analysis to include isospin breaking effects and also
include up to order $p^4$. We discuss vector meson chiral perturbation theory
in some detail and present a derivation from a relativistic lagrangian. The
unknown coefficients are estimated in various ways. We also discuss the
relevance of electromagnetic corrections and the implications of the present
calculation for the determination of quark masses.


title: R-parity Violation and Semileptonic Decays of B-meson

abstract:
  We investigate the effects of R-parity violation on the semileptonic decays
of B-meson in the minimal supersymmetric standard model with explicit R-parity
violation and discuss its physical implications. We find that the semileptonic
decays of B-meson can be largely affected by the R-parity violation.


title: QCD aspects of leptoquark production at HERA

abstract:
  If a leptoquark is produced at HERA as a narrow resonance, various effects
tend to broaden the measurable mass distribution considerably. These effects
are discussed here, with special emphasis on initial- and final-state QCD
radiation. A proper understanding is important to assess the significance of
data and to devise strategies for better mass reconstruction.


title:
Strong WW Scattering Physics: A Comparative Study for the LHC, NLC and a
  Muon Collider

abstract:
  We discuss the model independent parameterization for a strongly interacting
electroweak sector. Phenomenological studies are made to probe such a sector
for future colliders such as the LHC, $e^+e^-$ Linear collider and a muon
collider.


title: Quasiparticles and the quantum fluctuations of local observables

abstract:
  The role that quasiparticles play in a strong interaction system with
spontaneous symmetry breaking is examined. We find, using a non- perturbative
cluster decomposition method, that the quasiparticles do not saturate the
physical local observables at small distances. The fermion number density
serves as a clearcut example. A component due to localized random quantum
fluctuations of the order parameter(s) in the vacuum state and the
contributions of ``quasiparticles'' corresponding to other local minima of the
effective potential is needed. At large distances, the ordinary quasiparticle
picture emerges in the response of the system to classical background fields
but the above mentioned component acts as a source for them.


title: Strong Coupling Electroweak Symmetry Breaking

abstract:
  We review models of electroweak symmetry breaking due to new strong
interactions at the TeV energy scale and discuss the prospects for their
experimental tests. We emphasize the direct observation of the new interactions
through high-energy scattering of vector bosons. We also discuss indirect
probes of the new interactions and exotic particles predicted by specific
theoretical models. [Working group summary report from the Snowmass `96 summer
study, to appear in the proceedings.]


title: Reduction of Couplings and Finiteness in Realistic Supersymmetric GUTs

abstract:
  Reduction of couplings in supersymmetric GUTs is achieved by searching for
renormalization group invariant (RGI) relations among couplings which hold
beyond the unification scale. Finiteness is due to the fact that there exist
RGI relations among couplings that guarantee the vanishing of the
beta-functions of a N=1 supersymmetric GUT even to all orders in perturbation
theory. Of particular interest are the relations among gauge and Yukawa
couplings which lead to very interesting predictions of the top quark mass


title: CP Violation and Scalar Lepton Flavor Oscillation

abstract:
  Lepton flavor violation can be induced in supersymmetry by the mixing of two
or more of the leptonic scalar partners, Krashnikov and Arkani-Hamed et al.
pointed out that this effect may be observable at the Next Linear Collider,
through slepton pair production with subsequent lepton flavor violating decays.
If the slepton mixing involves all three generations, CP violation from the
Cabibbo-Kobayashi-Maskawa phase could lead to CP violating asymmetries between
the observed LFV decays. We lay down the formalism and give simple expressions
for the CP violating asymmetry in the transition probabilities, and consider
possible signals at future colliders.


title: Higgs Boson Search At Photon Collider For $M_H=140-190$ GeV

abstract:
  A Higgs boson within the mass range $M_H=140-190$ GeV can be discovered at a
photon collider in the reaction $\gamma\gamma\to WW$ (with real or virtual W)
with the luminosity integral about 1 fb$^{-1}$. The reasonable resolution in
the effective mass of the WW system is required.


title: Stops in R-parity Breaking Model for High-$Q^2$ Events at HERA

abstract:
  We investigate an event excess in the reaction $e^+p \to e^+ X$ with large
$x$ and high $Q^2$ observed at HERA and show that the events could naturally be
interpreted as a signature of the production of the scalar top quarks (stops)
in a supersymmetric model with $R$-parity breaking interactions. The HERA
events are characterized by the broad mass distribution and in fact it can be
simulated by our specific scenario if we consider almost degenerate two mass
eigenstates $\tilde{t_1}$ and $\tilde{t_2}$ of the stops.


title: Mass Corrections to the Vector Current Correlator

abstract:
  Three-loop QCD corrections to the vector current correlator are considered.
The large momentum procedure is applied in order to evaluate mass corrections
up to order $(m^2/q^2)^6$. The inclusion of the first seven terms to the ratio
$R=\sigma(e^+e^- \to hadrons)/\sigma(e^+e^- \to \mu^+\mu^-)$ leads to reliable
predictions from the high energy region down to relatively close to threshold.


title: $b \to s \ell\overline{\ell}$ process and multi-Higgs doublet model

abstract:
  Rare $b$ decay processes are analyzed in the multi-Higgs doublet model.
Taking account of the constraint from the $b\to s \gamma$ process, the
branching ratio and the forward-backward asymmetry of the final leptons for the
$b\to s \ell^+ \ell^-$ process are calculated. It is shown that the branching
ratio can be a few times larger than the standard model prediction and the
asymmetry can be significantly different from that in the standard model.
Combining these observable quantities it is possible to determine complex
coupling constants associated with the charged Higgs mixing matrix. The CP
violating charge asymmetry in the $b\to s \ell^+ \ell^-$ process and the
branching ratio of the $b\to s \nu\bar{\nu}$ process are also calculated.


title: Discovering and Studying Bileptons with e-e- Collisions

abstract:
  We analyze the prospects for discovering and unraveling the nature of
doubly-charged bileptons at a linear collider of the next generation running in
its electron-electron colliding mode. We stress the importance of initial state
radiation, beam spread and polarization, and compute the discovery bounds. The
gauge nature of vector bileptons can be determined by studying hard photon
emission.


title:
Scalar tau Signal at LEP 2 in models with Gauge Mediated Supersymmetry
  Breaking

abstract:
  In theories with gauge mediated supersymmetry breaking, the scalar tau,
(${\tilde \tau_1}$) is the lightest observable superpartner for part of the
parameter space. At LEP 2, the production of such a $\tilde \tau_1$ pair and
their subsequent decays give rise to a pair of $\tau$ leptons plus missing
energy from the unobserved gravitinos. The angular distributions of the
$\tau$'s are different from those arising from the production and decay of W
pairs, and thus will constitute an interesting signal for supersymmetry. We
also consider ${\tilde \tau_1}$ pair production in the complementary part of
parameter space where the lightest neutralino is lighter than the $\tilde
\tau_1$.