title: Theory of Small x Inclusive Photon Scattering, I

abstract:
  In the early eighties, L\'opez, Gonz\'alez-Arroyo and the present author
proved that, if at a given $Q_0^2$ large enough for perturbative QCD to be
valid, structure functions behave as a power of $x$ for $x\rightarrow 0$, then
for all larger $Q^2$ one has $$F_2(x,Q^2)\simeq
B_S[\alpha_s(Q^2)]^{-d_+}x^{-\lambda}
+B_{NS}[\alpha_s(Q^2)]^{-D_{11}}x^{0.5},$$ $$F_G(x,Q^2)\simeq
B_G[\alpha_s(Q^2)]^{-d_+}x^{-\lambda}$$
$$R(x,Q^2)=\frac{r_0\alpha_s(Q^2)}{\pi},$$ with $D_{11},\,d_+,\,B_G,\,r_0$
calculable in terms of $B_S,\,\lambda$. Moreover, it was suggested that the
``hard" part of the scattering cross section for real photons (Compton
scattering) obeys a similar law, so that $$\sigma_{\gamma p}\simeq B_{\gamma
p}s^{\lambda}+A_{\gamma p}\hat{\sigma}^P,$$ with a value of $\lambda$
comparable to that in the expression for the structure functions, and where
$\hat{\sigma}^P\sim\log^2s$ is a universal, Pomeron-type cross section, and
$A_{\gamma p},\, B_{\gamma p}$ are constants. In the present paper it is shown
that the recent HERA measurements may be described by these formulas, with a
chi-sqared/d.o.f. substantially less than unity, and with values of the
parameters compatible with those of the old fits of the '80s. Moreover, further
discussions are presented both on the low $Q^2$ limit, and the transition
between Compton and deep inelastic scattering, in particular in connection with
possible saturation of the coupling constant $\alpha_s(Q^2)$ at small $Q^2$;
and on the ultra high energy limit, and how one might test the so-called BFKL
conjecture, $$\lim_{x\rightarrow 0\atop Q^2\rightarrow \infty}F_2(x,Q^2)\sim
x^{-c_0\alpha_s}.$$\hb With respect to the last we find some evidence against


title: Polarized structure function $g_2$ in the CM bag model

abstract:
  The spin-dependent structure functions $g_1(x)$, $g_2(x)$, ${g}_2^{WW}(x)$
and ${\bar g}_2(x)$ and their moments are studied in the CM bag model. The
results show that (i) $\int_0^1g_2(x)dx=0$, i.e. the Burkhardt-Cottingham sum
rule holds, hence $g_2(x)$ must have at least one non-trivial zero besides
$x=0$ and $x=1$. (ii) $\int_0^1x^2g_2(x)dx$ is negative for the proton, neutron
and deuteron. (iii) $\int_0^1x^2g_2(x)dx$ is about one order of magnitude
smaller than $\int_0^1x^2g_1(x)dx$, hence the twist-3 matrix element is
approximately equal to the twist-2 matrix element. The results are compared
with most recent data and predictions from the MIT bag model, lattice QCD and
QCD sum rules.


title: Supercompositeness Inspired From Superstrings

abstract:
  String Unified Models based on the $k=1$ level of the Kac-Moody Algebra,
predict the existence of ``exotic'' new states which carry fractional electric
charges. We analyse the possibility of considering these ``exotics'' as preonic
matter which can be used to form the families and the gauge group breaking
higgs scalars. It is proposed that such a formation may occur provided that
these states transform non-trivially under a non-Abelian gauge group with a
relatively large rank in order to confine them at a sufficiently large scale.
Such a situation is natural in string derived unified models, since the role of
the confining group can be played by (part of) the Hidden symmetry. As an
example, we present a string derived toy model based on the $SU(4)\times
SU(2)_L \times SU(2)_R$ Pati-Salam gauge group.


title:
A Consistent model of Electroweak data including $Z\to b\overline{b}$
  and $Z\to c \overline{c}$

abstract:
  We have performed an overall fit to the electroweak data with the generation
blind $U(1)$ extension of the Standard Model. As input data for fitting we have
included the asymmetry parameters, the particle decay widths of $Z$, neutrino
scattering, and atomic parity violation. The QCD coupling $\alpha_s$ has been
constrained to the world average obtained from all data except the $Z$ width.
On the basis of our fit we have constructed a viable gauge model that not only
explains $R_b$ and $R_c$ but also provides a much better overall fit to the
data than the Standard Model. Despite its phenomenological viability, our model
is unfortunately not simple from the theoretical viewpoint. Atomic parity
violation experiments strongly disfavor more aesthetically appealing
alternatives that can be grand unified.


title: Resummation in hard QCD processes

abstract:
  We show that the resummation of large radiative corrections in QCD processes
can be performed both in covariant gauge and in axial gauge. We extend the
resummation technique to inclusive processes, concentrating on deeply inelastic
scattering, Drell-Yan production, and inclusive heavy meson decays in end-point
regions. Leading and next-to-leading logarithms produced by radiative
corrections are organized into Sudakov factors, whose expressions are the same
as those derived from the conventional Wilson-loop approach. The gauge
invariance of the resummation in the end-point region is demonstrated
explicitly.


title: The transverse lattice in 2+1 dimensions

abstract:
  Based on an idea due to Bardeen and Pearson, we formulate the light-front
Hamiltonian problem for SU(N) Yang-Mills theory in 2+1 dimensions using two
continuous space-time dimensions with the remaining space dimension discretized
on a lattice. We employ analytic and numerical methods to investigate the
string tension and the glueball spectrum in the large N limit. Our preliminary
results show qualitative agreement with recent Euclidean lattice Monte Carlo
simulations.


title: About the $Q^2$ dependence of asymmetry $A_1$

abstract:
  We analyse the proton and deutron data on spin dependent asymmetry
$A_1(x,Q^2)$ supposing the DIS structure functions $g_1(x,Q^2)$ and
$F_3(x,Q^2)$ have the similar $Q^2$-dependence. As a result, we have obtained
$\Gamma_1^p - \Gamma_1^n = 0.192$ at $Q^2= 10~{\rm GeV}^2$ and $\Gamma_1^p -
\Gamma_1^n = 0.165$ at $Q^2= 3~{\rm GeV}^2$, in the best agreement with the
Bjorken sum rule predictions.


title: The sunset diagram in SU(3) chiral perturbation theory

abstract:
  A general procedure for the calculation of a class of two-loop Feynman
diagrams is described. These are two-point functions containing three massive
propagators, raised to integer powers, in the denominator, and arbitrary
polynomials of the loop momenta in the numerator. The ultraviolet divergent
parts are calculated analytically, while the remaining finite parts are
obtained by a one-dimensional numerical integration, both below and above the
threshold. Integrals of this type occur, for example, in chiral perturbation
theory at order p^6.


title: $Z \to b {\bar b}$ in a composite model of fermions

abstract:
  A composite model of fermions is proposed to explain the "anomaly" in $Z
\rightarrow b {\bar b}$ and, to a lesser extent, in $Z \rightarrow c {\bar c}$.
It contains a {\em nonsequential} fourth family whose mass of one member (the
charge -1/3 quark) is constrained to be between 47 GeV and 49 GeV. The charge
+2/3 quark is constrained to lie between 67 GeV and 107 GeV. This opens up the
exciting prospect for near-future discoveries at LEP2 and possibly at the
Tevatron.


title: Associated Jet Production at HERA

abstract:
  We compare the BFKL prediction for the associated production of forward jets
at HERA with fixed-order matrix element calculations taking into account the
kinematical cuts imposed by experimental conditions. Comparison with H1 data of
the 1993 run favours the BFKL prediction. As a further signal of BFKL dynamics,
we propose to look for the azimuthal dependence of the forward jets.


title:
Relativistic Quantum Scattering of High Energy Fermions in the Presence
  of Phase Transition

abstract:
  We study the high energy behaviour of fermions hitting a general wall caused
by a first-order phase transition. The wall profile is introduced through a
general analytic function. The reflection coefficient is computed in the high
energy limit and expressed in terms of the poles of the wall profile function.
It is shown that the leading singularity gives the high energy behaviour.


title:
Effects Of The Quantity $\sigma_{TS}$ On The Spin Structure Functions Of
  Nucleons In The Resonance Region

abstract:
  In this paper, we investigate the effects of the quantity $\sigma_{TS}$ on
the spin-structure functions of nucleons in the resonance region. The Schwinger
sum rule for the spin structure function $g_2(x,Q^2)$ at the real photon limit
is derived for the nucleon treated as a composite system, and it provides a
crucial constraint on the longitudinal transition operator which has not been
treated consistently in the literature. The longitudinal amplitude $S_{\frac
12}$ is evaluated in the quark model with the transition operator that
generates the Schwinger sum rule. The numerical results of the quantity
$\sigma_{TS}$ are presented for both spin structure functions $g_1(x,Q^2)$ and
$g_2(x,Q^2)$ in the resonance region. Our results show that this quantity
  plays an important role in the low $Q^2$ region, which can be tested in the
future experiments at CEBAF.


title: Application of Sum rules to heavy baryon masses

abstract:
  Model independent sum rules are applied to recent measurements of heavy
c-baryon and d-baryon masses. The sum rules are generally satisfied to the same
degree as for the light (u,d,s) baryons.


title:
Ultrahigh-Energy Neutrino Interactions and Neutrino Telescope Event
  Rates

abstract:
  We present results for neutrino-nucleon cross sections for energies up to
10$^21$eV, of relevance to the detection of ultrahigh energy galactic and
extragalactic neutrinos. At the highest energies, our results are about 2.4
times larger than previous estimates. Using these new cross sections, we
predict neutrino telescope event rates for the upward moving muons initiated by
the neutrino interactions in the Earth and for contained-vertex events in the
PeV range due to neutrino-electron interactions. We show that future neutrino
detectors, such as AMANDA, BAIKAL, DUMAND and NESTOR have a very good chance of
detecting neutrinos which originate in the Active Galactic Nuclei.


title: Channel-Coupling Effects in High-Energy Hadron Collisions

abstract:
  The Two-Gluon Model of the Pomeron predicts strongly size-dependent
high-energy hadron cross sections. Yet experimental cross sections for radially
excited mesons appear surprisingly close in value. The strong coupling of these
mesons in hadron collisions also predicted by the model permits a qualitative
understanding of this puzzling behavior in terms of eigenmode propagation with
a common eigen-$\sigma$. A detailed semiempirical coupled-channel model of the
Pomeron is constructed to elucidate this and other features of high-energy
hadron cross sections.


title: The Next-to-Minimal Coleman-Weinberg Model

abstract:
  In the standard model (SM) the condition that the Higgs mass parameter
vanishes is stable under radiative corrections and yields a theory that can be
renormalized using dimensional regularization. Thus, this model allows to
predict the Higgs boson mass. However, it is phenomenologically ruled out in
its minimal version. Here, we present a phenomenologically viable, minimal
extension which only includes an additional SM singlet and a U(1)$_X$ gauge
symmetry.


title: Tau Decays and Chiral Perturbation Theory

abstract:
  In a small window of phase space, chiral perturbation theory can be used to
make standard model predictions for tau decays into two and three pions. For
$\tau \to 2\pi \nu_\tau$, we give the analytical result for the relevant form
factor $F_V$ up to two loops, then calculate the differential spectrum and
compare with available data. For $\tau \to 3 \pi \nu_\tau$, we have calculated
the hadronic matrix element to one loop. We discuss the decomposition of the
three pion states into partition states and we give detailed predictions for
the decay in terms of structure functions. We also compare with low energy
predictions of meson dominance models. Overall, we find good agreement, but
also some interesting discrepancies, which might have consequences beyond the
limit of validity of chiral perturbation theory.


title: Negative-parity Nucleon Resonance in the QCD Sum Rule

abstract:
  The negative-parity baryons are studied by a novel approach in the QCD sum
rule. It is found that the parity of the ground-state nucleon is determined by
the sign of the quark condensate. We predict the mass of negative-parity
nucleon.


title: Jet Production in Deep Inelastic Scattering at HERA

abstract:
  Two-jet cross sections in deep inelastic scattering at HERA are calculated in
next-to-leading order. The importance of higher order corrections and
recombination scheme dependencies is studied for various jetalgorithms. Some
implications for the determination of $\alpha_s(\mu_R^2)$, the determination of
the gluon density and the associated forward jet production in the low $x$
regime at HERA are briefly discussed.


title: Color-Octet Fraction in J/Psi Production and Absorption

abstract:
  The cross section between a $c \bar c$ pair and a nucleon is small and
sensitive to the $c - \bar c$ separation if the pair is in a color-singlet
state, but very large and insensitive to the separation if it is in a
color-octet state. We use this property in an absorption model involving both
color components to deduce the color structure of $c \bar c$ pairs produced in
$p(B)A \to \psi X$ reactions. Our analysis shows that the NA3, NA38 and E772
data are not inconsistent with the theoretical picture that color-octet and
color-singlet precursors are produced in roughly equal proportions if the
produced color-singlet precursors are pointlike and transparent. However, if
the color-singlet precursors are not transparent but have a cross section of a
few mb, these data do show a definite preference for a larger fraction of
color-singlet precursors. In either case, the color-octet fraction increases
with $x_F$, approaching unity as $x_F$ becomes large.


title: Systematics of soft final state interactions in $B$ decay

abstract:
  By using very general and well established features of soft strong
interactions we show, contrary to conventional expectations, that (i) soft
final state interactions (FSI) do not disappear for large $m_B$, (ii) inelastic
rescattering is expected to be the main source of soft FSI phases, and (iii)
flavor off-diagonal FSI are suppressed by a power of $m_B$, but are quite
likely to be significant at $m_B\simeq 5$~GeV. We briefly discuss the influence
of these interactions on tests of CP-violation and on theoretical calculations
of weak decays.


title:
Anomalous Transverse Distribution of Pions as a signal for the
  production of DCC's

abstract:
  We give evidence that the production of DCC's during a non-equilibrium phase
transition can lead to an anomalous transverse distribution of secondary pions
when compared to a more conventional boost invariant hydrodynamic flow in local
thermal equilibrium. Our results pertain to the linear $\sigma$ model,treated
in leading order in large-$N$, in a boost invariant approximation. We also show
that the interpolating number density of the field theory calculation plays the
role of a classical relativistic phase space number distribution in determining
the momentum distribution of pions in the center of mass frame.


title: Unification and Model Building, Astroparticle Physics and Neutrinos

abstract:
  This report summarises the work done during the Workshop on High Energy
Physics Phenomenology 4 (S.N.Bose National Centre for Basic Sciences, Calcutta,
India, Jan 2-14,1996) in Working Groups IV (Unification and Model Building) and
V (Astroparticle Physics and Neutrinos).


title: Particle Production in the Interstellar Medium

abstract:
  The flux of neutrinos and photons originating from cosmic ray interactions
with the interstellar medium in the galaxy is calculated based on current
models for high energy particle interactions. The contribution from a possible
dark matter halo of the galaxy is considered. The photon flux gets a
non-trivial attenuation due to interactions with the cosmic background
radiation. The neutrino fluxes are compared with those originating from the
Earth's atmosphere as well as from active galactic nuclei.


title: Scale dependence of quark mass matrices in models with flavor symmetries

abstract:
  Numerical correlations between fermion masses and mixings could indicate the
presence of a flavor symmetry at high energies. In general, the search for
these correlations using low-energy data requires an estimate of leading-log
radiative corrections. We present a complete analysis of the evolution between
the electroweak and the grand unification scales of quark mass parameters in
minimal supersymmetric models. We take $M_t=180$ GeV and consider all possible
values of $\tan \beta$. We also analize the possibility that the {\it top}
and/or the {\it bottom} Yukawa couplings result from an intermediate quasifixed
point (QFP) of the equations. We show that the quark mixings of the third
family do {\it not} have a QFP behaviour (in contrast to the masses, the
renormalization of all the mixings is linear), and we evaluate the low-energy
value of $V_{ub}$ which corresponds to $V_{ub}(M_X)=0$. Then we focus on the
renormalization-group corrections to {\it (i)} typical relations obtained in
models with flavor symmetries at the unification scale and {\it (ii)} a
superstring-motivated pattern of quark mass matrices. We show that in most of
the models the numerical prediction for $V_{ub}$ can be {\it corrected} in both
directions (by varying $\tan\beta$) due to {\it top} or {\it bottom} radiative
corrections.


title: High Energy Neutrino Production by Cosmic Ray Interactions in the Sun

abstract:
  The flux of neutrinos originating from cosmic ray interactions with matter in
the Sun has been calculated based on Monte Carlo models for high energy
particle interactions. The resulting flux at the Earth (within the Sun's solid
angle) is higher than the corresponding one from cosmic ray interactions with
the Earth atmosphere. The smallness of the absolute rate, however, precludes it
as a practical `standard candle' for neutrino telescopes and limits neutrino
oscillation searches. On the other hand, it facilitates dark matter searches
based on neutrinos from neutralino annihilation in the Sun.


title: Signals for Intrinsic Charm in High Energy Interactions

abstract:
  The prospects to test the hypothesis of intrinsic charm quarks in the proton
are investigated. We consider how this component can be directly or indirectly
probed in deep inelastic scattering at HERA and in fixed target experiments and
find that an overlooked signal might be present in existing NMC data. Applying
the intrinsic charm model to hadron collisions we compare the resulting charm
production cross-sections with those based on standard perturbative QCD and
available data. Extrapolating to higher energies we obtain predictions for
charm production at the Tevatron and LHC.


title: Resumming Phase Space Logarithms in Inclusive Semileptonic $B$ Decays

abstract:
  We study logarithms of the form $\ln(m_q/m_b)$ which arise in the inclusive
semileptonic decay of a bottom quark to a quark of mass $m_q$. We use the
renormalization group to resum the leading radiative corrections to these
terms, of the form $m_q^2\alpha_s^n\ln^n(m_q/m_b)$,
$m_q^3\alpha_s^{n+1}\ln^n(m_q/m_b)$ and $m_q^4\alpha_s^n\ln^{n+1}(m_q/m_b)$.
The first two resummations are trivial, while the latter involves a non-trivial
mixing of four-fermi operators in the $1/m_b$ expansion. We illustrate this
technique in a toy model in which the semileptonic decay is mediated by a
vector interaction, before treating the more complicated case of left-handed
decay.


title:
Searching for Heavy Quarks at NMC: A Simple Estimate of Background Muons
  from $\pi$ and $K$ decays

abstract:
  New physics can be searched for in deep inelastic scattering experiments. New
phenomena, like additional production mechanisms for heavy quarks, manifest
themselves through production and decays of short-lived hadrons, which give
additional muons in their decays. Muons from decays of light mesons can then be
a severe background, especially at fixed target experiments. In order to make a
first estimate of such a background a simple analytic method is here developed
and applied on the muon scattering experiment NMC.


title: Evolution of structure functions in a chiral potential model

abstract:
  Evolution of structure functions is studied in a chiral potential model which
incorporates the pion as the chiral symmetry restoring field. Evolution
equations for the quark and pion densities are derived in the lowest order at
large $Q^2$. The splitting function for quark emission from point-like pion is
flavor-dependent. This is shown to lead to nontrivial evolution of the
nonsinglet moments in the next order which is consistent with the observed
departure from the Gottfried sum rule.


title:
Single Spin Asymmetries in Inclusive High Energy Hadron-Hadron Collision
  Processes

abstract:
  Characteristics of the available data are briefly summarized. Different
theoretical approaches are reviewed with special attention to a
non-perturbative model which explicitly takes the orbital motion of the valence
quarks into account. The connection between such asymmetries and hyperon
polarization in unpolarized reactions is discussed.


title:
Dispersion-theoretical analysis of the nucleon electromagnetic form
  factors: Inclusion of time-like data

abstract:
  We update a recent dispersion--theoretical fit to the nucleon electromagnetic
form factors by including the existing data in the time--like region. We show
that while the time--like data for the proton can be described consistently
with the existing world space--like data, this is not the case for the neutron.
Another measurement of the process $e^+ e^- \to \bar n n$ is called for. We
furthermore sharpen the previous estimate of the separation between the
perturbative and the non--perturbative regime, which is characterized by a
scale parameter $\Lambda^2 \simeq 10\,$GeV$^2$.


title: Nucleon Structure Functions from a Chiral Soliton

abstract:
  Nucleon structure functions are studied within the chiral soliton approach to
the bosonized Nambu-Jona-Lasinio model. The valence quark approximation is
employed which is justified for moderate constituent quark masses ($\sim$ 400
MeV) as the contribution of the valence quark level dominates the predictions
of nucleon properties. As examples the unpolarized structure functions for the
${\nu}p$ and ${\bar \nu}p$ scattering and the structure functions entering the
Gottfried sum rule are discussed. For the latter the model prediction is found
to reasonably well agree with a corresponding low-scale parametrization of the
empirical data.


title: $\mu\to e\gamma$ Search with Polarized Muons

abstract:
  A search for the lepton-flavor violating $\mu^{+}\rightarrow e^{+}\gamma$
decay using polarized muons is proposed. By measuring the angular distribution
of $e^{+}$s with respect to the muon spin direction, in particular antiparallel
$e^{+}$s, the serious physics background from $\mu^{+}\rightarrow
e^{+}\nu\overline{\nu}\gamma$ as well as accidental background from normal muon
decay accompanied by a high-energy photon can be suppressed significantly. In
addition to the enhancement of the sensitivity, the angular distribution would
discriminate among different extensions to the Standard Model, once the signal
is observed.


title:
Pseudoscalar Glueball, eta'-meson and its Excitation in the Chiral
  Effective Lagrangian

abstract:
  A generalization of the chiral effective lagrangian of order $p^2$ is
proposed which involves the $\eta'$-meson, its excitation, and the pseudoscalar
(PS) glueball. Model-independent constraints are found for the contributions to
the lagrangian of the above singlet states. Those allow one to independently
identify the nature of these singlet states in the framework of the approach.
The mixing among the iso-singlet states (including $\eta^8$-state) is analysed,
and the hierarchy of the mixing angles is described which is defined by the
chiral and large-$N_c$ expansions. The recent PCAC results are reproduced,
which are related to the problem of the renormalization-group invariant
description of the $\eta'$ and the PS glueball, and a further analysis of this
problem is performed.


title:
Baryonic $Z'$ connection of LEP $R_{b,c}$ data with Tevatron
  $(W,Z,\gamma)b\bar b$ events

abstract:
  The mixing of a new $Z'$ boson with the $Z$ significantly improves the fit to
the LEP precision electroweak data, provided that the $Z'$ couples mainly to
quarks. If $M_{Z_2}<200$~GeV, the $s$-channel $Z_2$ production and
$(W,Z,\gamma)Z_2$ pair production cross sections at the Tevatron give an excess
above QCD of $b\bar b$ and $(W,Z,\gamma)b\bar b$ events, respectively, with
invariant mass $m(b\bar b)\approx M_{Z_2}$, which provide viable signals for
detection of the $Z_2$. The interference of the $Z_2$ with $\gamma,Z_1$ in
$e^+e^-\to \bar bb(\bar cc)$ at LEP\,1.5 energies is correlated with $R_b(R_c)$
and may be observable.


title:
The Limiting Curve of Leading Particles from Hadron-Nucleus Collisions
  at Infinite A

abstract:
  We argue that as the atomic number of the target nucleus $A \to \infty$, the
multiplicity of leading particles in hadron-nucleus collisions tends to a
finite limit. The limiting multiplicities for various particle production are
computed for both proton and pion projectiles. Signatures at finite A are
discussed. Data from 100 GeV/c central hadron-nucleus collisions are analyzed
and found to be in qualitative agreement with this picture.


title: Dilepton and Photon Productions from a Coherent Pion Oscillation

abstract:
  Since the electromagnetic current for a pion system coincides with the third
component of the isovector current, the isospin angular oscillation of a
coherent field can be a significant source for the electromagnetic emissions.
We study the characteristic dilepton and photon emissions from the classical
pion field oscillation in the QCD vacuum. The general analytical solution
obtained in the nonlinear sigma model is used to calculate the electromagnetic
current density, which exhibits a light-front singularity and decreases rapidly
as inverse square of the proper time due to a longitudinal expansion. The
momentum and invariant mass spectra of the direct photon and dilepton are found
to be a sensitive probe of the space-time evolution of the chiral condensate
field.


title:
Energy Spectrum of Secondary Leptons in $e^+ e^- \to t\bar{t}$ -
  Non-standard Interactions and CP Violation -

abstract:
  The process of top-quark pair production at future high-energy $e^+ e^-$
linear colliders has been investigated as a possible test of physics beyond the
Standard Model. Non-standard interactions have been assumed both for the
production and for the subsequent decay of the top quarks. The energy spectrum
of the single lepton $l^\pm$ and the energy correlation of $l^+$ and $l^-$
emerging from the process $e^+e^-\to t\bar{t}\to l^\pm X/l^+l^-X$ are
calculated. The energy- spectrum asymmetry of $l^+$ and $l^-$ is considered as
a measure of CP violation. An optimal method to determine whether CP violation
occurs in the production or in the decay processes is proposed.


title: Leptophobic Z' from Superstring Derived Models

abstract:
  It was recently suggested that the reported anomalies in $R_b$ and $R_c$ can
be interpreted as the effect of a heavy vector boson that couples to quarks and
is universally decoupled from leptons. We examine how an extra gauge boson with
this property can arise from superstring derived models. In a specific three
generation model we show that the $U(1)_{B-L}$ symmetry combines with the
horizontal flavor symmetries to form a universal leptophobic $U(1)$ symmetry.
In our model there is an enhancement of the color gauge group from twisted
sectors. The enhancement occurs after the breaking of the unifying gauge
symmetry by ``Wilson lines''. The leptophobic $U(1)$ symmetry then becomes a
generator of the color $SU(4)$ gauge group. We examine how similar symmetries
may appear in other string models without the enhancement. We propose that if
the current LEP anomalies persist it may be evidence for a certain class of
un--unified superstring models.


title: Four Fermions Productions at a $\gamma\gamma$ Collider

abstract:
  Using the recently proposed ALPHA algorithm (and the resulting code) I
compute the rate (at tree level) for the process
$\gamma\gamma\rightarrow\bar\nu_e e^- u \bar d$. The bulk of the contribution
is due to W pair production and decay. However a non negligible ($\sim10 \%$)
contribution comes from other channels, mainly the production and decay of a W
and a collinear charged fermion. Requiring that the reconstructed invariant $u
\bar d$ mass lies in the intervals $M_W\pm 5 $ GeV and $M_W\pm 20 $ GeV one
obtains a rate which is lower, by 25 \% and 4 \% respectively, than the rate
obtained in the $narrow$ $width$ approximation, thus demonstrating the
relevance of the finite W width.


title:
Contribution of intermediate stage gluons to J/Psi suppression in
  Lead-Lead collisions at 158 AGeV

abstract:
  We point out that dissociation of J/Psi by partons (mostly gluons) present in
the intermediate stage of heavy-ion collisions can explain J/Psi suppression
observed recently by the NA-50 Collaboration at the CERN-SPS in Pb-Pb
interactions. Suppression by intermediate stage gluons represents an additional
multiplicative factor to that given by Gerschel-Hufner mechanism. The agreement
with data on J/Psi suppression both in light- ions induced nuclear collisions
and in Pb-Pb interactions requires that the life-time of intermediate gluons
increases with nucleon numbers of colliding nuclei. In our model the energy
density of intermediate stage gluons in Pb-Pb collisions approaches for a short
time the critical density.


title: Nuclear Dependence of Structure Functions in Coordinate Space

abstract:
  The momentum distributions of partons in bound nucleons are known to depend
significantly on the size of the nucleus. The Fourier transform of the momentum
($\xbj$) distribution measures the overlap between Fock components of the
nucleon wave function which differ by a displacement of one parton along the
light cone. The magnitude of the overlap thus determines the average range of
mobility of the parton in the nucleon. By comparing the Fourier transforms of
structure functions for several nuclei we study the dependence of quark
mobility on nuclear size. We find a surprisingly small nuclear dependence
($<2\%$ for He, C and Ca) for displacements $t=z \lsim 2.5$ fm, after which a
nuclear suppression due to shadowing sets in. The nuclear effects observed in
momentum space for \mbox{$\xbj \lsim 0.4$} can be understood as a reflection of
only the large distance shadowing in coordinate space.


title:
On consistent determination of $\alpha_s$ from jet rates in deep
  inelastic scattering

abstract:
  For theoretically consistent determination of $\alpha_s$ from jet rates in
deep inelastic scattering the dependence on $\alpha_s$ of parton distribution
functions is in principle as important as that of hard scattering
cross--sections. For the kinematical region accessible at HERA we investigate
in detail numerical importance of these two sources of the $\alpha_s$
dependence of jet rates.


title:
On the Determination of $\Delta m$ and $\Delta \Gamma$ in Tagged
  $D^0$--$\bar D^0$ Decays

abstract:
  We consider the time dependence of the decays of tagged $D^0$ and $\bar{D}^0$
into CP-conjugate final states $f$ and $\bar{f}$, or into a CP eigenstate $F$.
We expand each decay width as $\exp (- \Gamma t)$ times a series in $\Gamma t$,
where $\Gamma$ is the average decay width of the mass eigenstates $D_H$ and
$D_L$, and examine the first three terms of the series. We show that
experimental information on the coefficients of these terms allows in principle
to compute all the relevant mixing parameters. In particular, depending on CP
violation or conservation, we discuss the different possibilities to extract
$\Delta m$ and $\Delta \Gamma$, i.e., the mass and decay-width differences of
the mass eigenstates. We also comment on consistency conditions among the
coefficients of the various decay-width expansions.


title: An investigation of the phase transition in the extended bag model

abstract:
  By proposing an Ansatz for the pressure (measured in terms of the bag
constant) of the hadronic gas in equilibrium, we have formulated a rather
simple method which allows one to analytically investigate the bulk
thermodynamic propertities in the vicinity of the phase transition. This makes
it also possible to take into account the nonperturbative vacuum effects from
both sides of the equilibrium condition. As an example of our approach, we have
calculated the crossover (critical or transition) temperature $T_c$ and the
critical chemical potential $\mu_c$ (as functions of the bag constant) from the
noninteracting quark-gluon plasma state equation. Our results for
$T_c(N_f=0)=241.5 MeV$ and $T_c(N_f=2)=160.6 MeV$ are in good agreement with
recent lattice data. The extensive densities such as the entropy density,
specific heat, etc. are calculated as well. A general scheme how to calculate
the latent heat, the critical density, etc. within the extended bad model is
also described and it is applied to the two models of the hadronic gas phase.


title:
Global Power Counting Analysis On Probing Electroweak Symmetry Breaking
  Mechanism At High Energy Colliders

abstract:
  We develop a precise power counting rule (a generalization of Weinberg's
counting method for the nonlinear sigma model) for the electroweak theories
formulated by chiral Lagrangians. Then we estimate the contributions of ``all''
next-to-leading order (NLO) bosonic operators to the amplitudes of the relevant
scattering processes which can be measured at high energy colliders, such as
the LHC and future Linear Colliders. Based upon these results, we globally
classify the sensitivities of testing all NLO bosonic operators for probing the
electroweak symmetry breaking mechanism at high energy colliders.


title:
The $\pi\pi$ Final State Interaction in $K\to\pi\pi$, $pp\to pp\pi\pi$
  and Related Processes

abstract:
  Final state interactions in the $S$--wave $\pi\pi$ system (I=0,2) are
re-examined on the basis of the Omn\`es-Mus\-khe\-li\-shvili equation and the
coupled channel formalism. The contributions to the pion scalar form factor
from $\rho$ and $f_2(1270)$ exchange in the $t$--channel and from the
$f_0(980)$ $s$--channel resonance are separately evaluated and the role of the
nontrivial polynomial in the Omn\`es function in a coupled channel situation is
elucidated. Applications are made to $K\to \pi\pi$ and $pp\to pp\pi\pi$. It is
found that the contribution from the $f_0$ resonance to the form-factor is
strongly reduced by a nearby zero.


title: Four-Loop Vacuum Energy Beta Function in O(N) Symmetric Scalar Theory

abstract:
  The beta function of the vacuum energy density is computed at the four-loop
level in massive O(N) symmetric phi^4 theory. Dimensional regularization is
used in conjunction with the MSbar scheme and all calculations are in momentum
space in the massive theory. The result is
  beta_v = g N/4+g^3 N(N+2)/96+g^4 N(N+2)(N+8)[12 zeta(3)-25]/1296+o(g^5).


title: Implications Of A Non-Standard Light Higgs Boson

abstract:
  Analyses of the vacuum stability of the electroweak theory indicate that new
physics occur at a scale of order of 1 TeV if a light Higgs is discovered at
LEP II. In this paper, we parameterize the effects of new physics in the
effective Lagrangian approach and examine its implication on the Higgs boson
production at LEP II. We consider the effect of higher dimension operator on
the Higgs potential and calculate the lower bound on the Higgs boson mass from
the requirement of vacuum stability. We show that if a Higgs boson is seen at
LEP II then under favourable conditions the deviation of the production cross
section from the standard model value could be significant and therefore the
presence of the new physics is detectable at LEP II.


title: Sudakov Factorization and Resummation

abstract:
  We present a unified derivation of the resummation of Sudakov logarithms,
directly from the factorization properties of cross sections in which they
occur. We rederive in this manner the well-known exponentiation of leading and
nonleading logarithmic enhancements near the edge of phase space for cross
sections such as deeply inelastic scattering, which are induced by an
electroweak hard scattering. For QCD hard-scattering processes, such as
heavy-quark production, we show that the resummation of nonleading logarithms
requires in general mixing in the space of the color tensors of the hard
scattering. The exponentiation of Sudakov logarithms implies that many weighted
cross sections obey particular evolution equations in momentum transfer, which
streamline the computation of their Sudakov exponents. We illustrate this
method with the resummation of soft-gluon enhancements of the inclusive
Drell-Yan cross section, in both DIS and $\overline{{\rm MS}}$ factorization
schemes.


title: Strange and Charmed Quarks in the Nucleon

abstract:
  We discuss the general method of the calculation of the nucleon matrix
elements of an operator associated with nonvalence quarks. The method is based
on the QCD sum rules and low energy theorems. As an application of these
considerations, we calculate the strange quark matrix element as well as the
momentum distribution of the strangeness in the nucleon. We also calculate the
singlet axial constant associated with $\eta'$ meson as well as an axial
constant associated with heavy quarks.


title: Hot quark-gluon matter with deconfined heavy quarks

abstract:
  The phase diagram of the quark-gluon matter evolution is presented for the
SU(3)-model with a new phase of heavy deconfined quarks which exists in a
rather wide range of temperatures and densities. Fitting the chiral phase
transition data to fix the model parameters we establish another
(deconfinement) phase transition which separates a new phase from hadronic
matter. The parameters and properties of the phase diagram are discussed in
comparison with lattice and other results.


title: $e^+ \ e^-$ into 4 fermions + $\gamma$ with ALPHA

abstract:
  We apply the iterative numerical algorithm ALPHA, which automatically
generates the N-point Green functions (as recently suggested \cite{alpha}) to
the computation of the production rate of four fermions and four fermions plus
photon in electron-positron annihilation. The discussion of the physical
results is preceded by an introduction on the algorithm.


title: Scaling Limit of Deeply Virtual Compton Scattering

abstract:
  I outline a perturbative QCD approach to the analysis of the deeply virtual
Compton scattering process $\gamma^* p \to \gamma p'$ in the limit of vanishing
momentum transfer $t= (p' - p)^2$. The DVCS amplitude in this limit exhibits a
scaling behaviour described by a two-argument distributions $F(x,y)$ which
specify the fractions of the initial momentum $p$ and the momentum transfer $r
\equiv p'-p$ carried by the constituents of the nucleon.The kernel
$R(x,y;\xi,\eta)$ governing the evolution of the non-forward distributions
$F(x,y)$ has a remarkable property: it produces the GLAPD evolution kernel
$P(x/\xi)$ when integrated over $y$ and reduces to the Brodsky-Lepage evolution
kernel $V(y,\eta)$ after the $x$-integration. This property is used to
construct the solution of the one-loop evolution equation for the flavour
non-singlet part of the non-forward quark distribution.


title: A Constituent Picture of Hadrons from Light-Front QCD

abstract:
  It may be possible to derive a constituent approximation for bound states in
QCD using hamiltonian light-front field theory. Cutoffs that violate explicit
gauge invariance and Lorentz covariance must be employed. A similarity
renormalization group and coupling coherence are used to compute the effective
hamiltonian as an expansion in powers of the canonical QCD running coupling
constant. At second order the QCD hamiltonian contains a confining interaction,
which is being studied using bound state perturbation theory. Explicit
constituent masses appear because of symmetry violations, and confinement also
produces mass gaps, leading to the possibility of an accurate non-perturbative
constituent approximation emerging in light-front QCD.


title: Two Topics in $b$ Physics

abstract:
  (1) A simple transversity analysis permits one to separate the P-even and
P-odd partial waves in such decays as $B_s \to J/\psi \phi$ and $B \to J/\psi
K^*$. This method is relevant to the separation of contributions of CP-even and
CP-odd final states in $B_s$ decays, and hence to the measurement of a possible
lifetime difference between mass eigenstates. (2) The enhancement $\Delta
\Gamma (\Lambda_b)$ of the $\Lambda_b$ decay rate due to four-fermion processes
is calculated in terms of the $\Sigma_b^* - \Sigma_b$ hyperfine splitting, the
$B^* - B$ hyperfine splitting, and the $B$ meson decay constant $f_B$. Despite
a relatively large hyperfine splitting observed by the DELPHI Collaboration,
the mechanism falls far short of being able to explain the observed
enhancement.


title:
Dominant Two-Loop Corrections to the MSSM Finite Temperature Effective
  Potential

abstract:
  We show that two-loop corrections to the finite temperature effective
potential in the MSSM can have a dramatic effect on the strength of the
electroweak phase transition, making it more strongly first order. The change
in the order parameter $v/T_c$ can be as large as 75\% of the one-loop daisy
improved result. This effect can be decisive to widen the region in parameter
space where erasure of the created baryons by sphaleron processes after the
transition is suppressed and hence, where electroweak baryogenesis might be
successful. We find an allowed region with $\tan\beta\simlt 4.5$ and a Higgs
boson with standard couplings and mass below $80\ GeV$ within the reach of LEP
II.


title: Z' Constraints from e+e- to f fbar at NLC

abstract:
  Constraints on extra neutral gauge bosons are obtained from
$e^+e^-\rightarrow f\bar f$ at NLC energies. Model independent limits on the
$Z'f\bar f$ couplings and lower limits on the $Z'$ mass are discussed. Typical
GUTs with $M_{Z'}$ up to (3 -- 6) $\sqrt{s}$ can be excluded. A distinction
between different GUT scenarios is possible if $M_{Z'}\le 3\sqrt{s}$. Radiative
corrections give only small changes to the $Z'$ exclusion limits provided that
appropriate cuts are applied. %The inclusion of systematic errors leads to
slightly worse results for %$M_{Z'}^{lim}$.


title: Heavy Hadron Spectrum and Interactions

abstract:
  Starting from the approximate symmetries of QCD, namely chiral symmetry for
light quarks and spin and flavor symmetry for heavy quarks, we investigate the
low-energy properties of heavy hadrons. For this purpose we construct a
consistent picture of quark-antiquark and quark-diquark interactions as a
low-energy approximation to the flavor dynamics in heavy mesons and heavy
baryons, respectively. Using standard functional integration tools, we derive
an effective Lagrangian in terms of heavy hadron fields and discuss several
properties, like the mass spectrum, coupling and decay constants, Isgur-Wise
form factors.


title:
Hydrodynamical analysis of symmetric nucleus-nucleus collisions at
  CERN/SPS energies

abstract:
  We present a coherent theoretical study of ultrarelativistic heavy-ion data
obtained at the CERN/SPS by the NA35/NA49 Collaborations using 3+1-dimensional
relativistic hydrodynamics. We find excellent agreement with the rapidity
spectra of negative hadrons and protons and with the correlation measurements
in two experiments: $S+S$ at 200 $AGeV$ and $Pb+Pb$ at 160 $AGeV$ (preliminary
results). Within our model this implies that for $Pb+Pb$ ($S+S$) a
quark-gluon-plasma of initial volume 174 $fm^3$ (24 $fm^3$) with a lifetime 3.4
$fm/c$ (1.5 $fm/c$) was formed. It is found that the Bose-Einstein correlation
measurements do not determine the maximal effective radii of the hadron sources
because of the large contributions from resonance decay at small momenta. Also
within this study we present an NA49 acceptance corrected two-pion
Bose-Einstein correlation function in the invariant variable, $Q_{inv}$.


title: Nucleon spin structure from the instanton vacuum

abstract:
  We discuss the evaluation of the nucleon isoscalar axial coupling,
$g_A^{(0)}$, in the instanton vacuum, using the $1/N_c$ expansion. This
approach allows a fully consistent treatment of the $U(1)_A$ anomaly. We
compute the nucleon matrix element of the topological charge density, $\langle
N | F\widetilde{F} | N \rangle$, and show that it reduces to the matrix element
of the divergence of the isoscalar axial quark current. Our arguments show that
the usual evaluation of $g_A^{(0)}$ in the chiral quark soliton model is
consistent with the $U(1)_A$ anomaly in leading order of $1/N_c$. Such
calculations give $g_A^{(0)} = 0.36$, which is in agreement with the recent
estimate by Ellis and Karliner.


title: Z -> b b-bar Excess from R-Parity Violation

abstract:
  The $\Zbb$ excess, $\Zcc$ deficit, and low left-right asymmetry $A_b$ may be
explained by a single term $\lam C^c B^c B^{\prime c}$ in the superpotential.
This operator violates R-parity and requires a sequential 4th generation.
1-loop diagrams involving squark exchange interfere with the tree-level
processes to give an excess of right-handed $b$ quarks, and a deficit of
right-handed $c$ quarks. Though the coupling must be large ($\lam\approx 2$ or
$3$), the model is phenomenologically and cosmologically acceptable.


title: Distributions in Four-Fermion Processes

abstract:
  The programs WPHACT and WTO, which are designed for computing cross sections
and other relevant observables in the $e^+e^-$ annihilation into four fermions,
are used to make detailed and complete predictions for the semi-leptonic and
fully hadronic channels $e^+e^- \to \barq q l\nu, \barq q \barq q$. Both the
total cross sections in the LEP~2 energy range and some of the most relevant
distributions are analyzed. Particular algorithms are introduced for the fully
hadronic channels in order to analyze the $WW$ physics and to properly define
the signal versus the background. With appropriate kinematical cuts it has been
shown that the Neutral Current background can be made vanishingly small when
the problem of determining the $W$ boson mass is addressed. The remaining
background from the complete Charge Current and Mixed processes is again small
but not completely negligible. A detailed discussion is performed on the
validity of the most relevant approximations such as the double-resonant one.
The inclusion of final state QCD correction, in its {\it naive} form (NQCD), is
discussed and various implementations are examined.


title: The Landau-Pomeranchuk-Migdal effect in QED

abstract:
  The calculation of the radiative energy loss encountered by a fast charged
particle which undergoes multiple scattering is being investigated. A detailed
derivation of the Landau-Pomeranchuk-Migdal coherent effect in QED is given,
focusing on the specific feature of the Coulomb interaction. As a result the
radiation intensity per unit length in the coherent regime is shown to be
proportional to $\sqrt \omega$ for a photon energy $\omega$ times a logarithmic
enhancement which is determined exactly.


title: Top Quark Polarization in Polarized $e^+e^-$ Annihilation near Threshold

abstract:
  Top quark polarization in $e^+e^-$ annihilation into $t\bar t$ is calculated
for linearly polarized beams. The Green function formalism is applied to this
reaction near threshold. The Lippmann--Schwinger equations for the $S$-wave and
$P$-wave Green functions are solved numerically for the QCD chromostatic
potential given by the two-loop formula for large momentum transfer and
Richardson's ansatz for intermediate and small momenta. $S$-$P$--wave
interference contributes to all components of the top quark polarization
vector. Rescattering of the decay products is considered. The mean values
$\langle n \ell \rangle$ of the charged lepton four-momentum projections on
appropriately chosen directions $n$ in semileptonic top decays are proposed as
experimentally observable quantities sensitive to top quark polarization. The
results for $\langle n \ell \rangle$ are obtained including $S$-$P$--wave
interference and rescattering of the decay products. It is demonstrated that
for the longitudinally polarized electron beam a highly polarized sample of top
quarks can be produced.


title:
Quark Distribution in the Pion from QCD Sum Rules with Nonlocal
  Condensates

abstract:
  We calculate the leading twist valence quark distribution in the pion in the
framework of QCD sum rules with nonlocal condensates. Particular attention has
been paid to the correct account for the bilocal power corrections.


title: The Complete |Delta S|=2 Hamiltonian in the Next-To-Leading Order

abstract:
  We present the complete next-to-leading order short-distance QCD corrections
to the effective \dstwo -hamiltonian in the Standard Model. The calculation of
the coefficient $\eta_3$ is described in great detail. It involves the two-loop
mixing of bilocal structures composed of two \dsone\ operators into \dstwo\
operators. The next-to-leading order corrections enhance $\eta_3$ by 27\% to
$\eta_3=0.47 \errorpm{+0.03}{-0.04}$ thereby affecting the phenomenology of
$\epsilon_K$ sizeably. $\eta_3$ depends on the physical input parameters $m_t$,
$m_c$ and $\laMSb$ only weakly. The quoted error stems from renormalization
scale dependences, which have reduced compared to the old leading log result.
The known calculation of $\eta_1$ and $\eta_2$ is repeated in order to compare
the structure of the three QCD coefficients. We further discuss some field
theoretical aspects of the calculation such as the renormalization group
equation for Green's functions with two operator insertions and the
renormalization scheme dependence caused by the presence of evanescent
operators.


title:
Spin asymmetries in one-jet production at RHIC with polarized proton
  beams : the effects of a hadrophilic Z'

abstract:
  We show that the measurement of some parity violating asymmetry in the
production of a large ET jet could reveal the presence of a new hadrophilic Z'
such as the one recently introduced to interpret possible departures from the
Standard Model predictions both at LEP and at CDF. Such a measurement could be
perform within a few years by the RHIC Spin Collaboration (RSC) using the
Relativistic Heavy Ion Collider (RHIC) as a polarized proton-proton collider.


title: QCD in e+e- collisions at 2 TeV

abstract:
  We discuss some topics in QCD studies at 2 TeV. Particular emphasis is given
to the separation of pure QCD events from the WW and the t-tbar backgrounds


title: On the evaluation of three--loop scalar integrals in the massive case

abstract:
  I describe a method to calculate a class of three-loop selfenergy diagrams
for arbitrary internal masses and external momentum. This method combines
analytical results and numerical integration, and is suitable for
implementation in a computer program to produce fast and accurate results. For
the class of Feynman diagrams considered in this paper this method leads to a
two-fold integral which needs to be evaluated numerically. Results are given
for a range of masses and external momentum.


title: Particle Physics Opportunities at $\mu^+\mu^-$ Colliders

abstract:
  We discuss the capabilities of future muon colliders to resolve important
particle physics questions. A collider with c.m. energy $\sqrt s = 100$ to
500~GeV offers the unique opportunity to produce Higgs bosons in the
$s$-channel and thereby measure the Higgs masses, total widths and several
partial widths to high precision. At this same machine, $t\bar t$ and $W^+W^-$
threshold studies would yield superior precision in the determination of $m_t$
and $m_W$. A multi-TeV $\mu^+\mu^-$ collider would open up the realm of physics
above the 1 TeV scale, allowing, for example, copious production of
supersymmetric particles up to the highest anticipated masses or a detailed
study of the strongly-interacting scenario of electroweak symmetry breaking.


title: Spectator effects in semileptonic decay of charmed baryons

abstract:
  It is shown that the absolute rate of the semileptonic decays of the $\Xi_c$
baryons can be as much as two times higher than the semileptonic decay rate of
$\Lambda_c$ due to the Pauli interference of the strange quark. This
interference effect is still larger in the semileptonic decay rate of
$\Omega_c$. An experimental measurement of the difference of these rates would
thus provide an important piece of information on the spectator effects in
decays of hadrons containing a heavy quark.


title: Remarks on a Technique of Measuring CP phase $\alpha$

abstract:
  We present a method to measure the CKM phase $\alpha$ and the tree and
penguin (strong and electroweak) amplitudes in $B \rightarrow \pi \pi$ decays,
based on isospin consideration and the weak assumption that all tree amplitudes
have a common strong phase and all penguin amplitudes have a different common
phase. The method needs only the time-independent measurements of the relevant
decay rates in $B \rightarrow \pi \pi$. We also propose a method to
experimentally examine the validity of the assumption that all penguin
amplitudes have the same strong phases, and to extract detailed informations
about the hadronic matrix elements.


title: A Multiple Commutator Formula for the Sum of Feynman Diagrams

abstract:
  In the presence of a large parameter, such as mass or energy, leading
behavior of individual Feynman diagrams often get cancelled in the sum. This is
known to happen in large-$N_c$ QCD in the presence of a baryon, and also in the
case of high-energy electron-electron as well as quark-quark scatterings. We
present an exact combinatorial formula, involving multiple commutators of the
vertices, which can be used to compute such cancellations. It is a non-abelian
generalization of the eikonal formula, and will be applied in subsequent
publications to study the consistency of large-$N_c$ QCD involving baryons, as
well as high-energy quark-quark scattering in ordinary QCD.


title: Supersymmetric Signatures at an $e$$\gamma$ Collider

abstract:
  High energy electron-photon colliders provide unique opportunities for
probing physics beyond the standard model. We have studied the experimental
signatures for two supersymmetric scenarios, with the lightest supersymmetric
particle (LSP) being either the lightest neutralino or the gravitino. In the
``neutralino LSP'' scenario favored by the minimal supersymmetric standard
model (MSSM), it is found that some basic parameters of the model, $\mu$,
$\tan\beta$, $M_1$ and $M_2$, may be uniquely determined from the outgoing
electron energy spectrum without assuming high scale unification of the masses
or couplings. In the ``gravitino LSP'' scenario which occurs naturally in
models of low energy dynamical supersymmetry breaking, it is possible to have
background-free signatures if the next-to-lightest supersymmetric particle
(NLSP) has a long decay length. In cases that the NLSP decays quickly, ways to
distinguish among the experimental signatures of the two scenarios and of the
standard model (SM) background are discussed.


title: The Experimental Investigation of Supersymmetry Breaking

abstract:
  If Nature is supersymmetric at the weak interaction scale, what can we hope
to learn from experiments on supersymmetric particles? The most mysterious
aspect of phenomenological supersymmetry is the mechanism of spontaneous
supersymmetry breaking. This mechanism ties the observable pattern of
supersymmetric particle masses to aspects of the underlying unified theory at
very small distance scales. In this article, I will discuss a systematic
experimental program to determine the mechanism of supersymmetry breaking. Both
$pp$ and $e^+e^-$ colliders of the next generation play an essential role.
[Lecture presented at the 1995 Yukawa International Symposium (YKIS`95), to
appear in the proceedings.]


title: Reheating and thermalization in a simple scalar model

abstract:
  We consider a simple model for the Universe reheating, which consists of a
single self--interacting scalar field in Minkowskian space--time. Making use of
the existence of an additional small parameter proportional to the amplitude of
the initial spatially homogeneous field oscillations, we show that the behavior
of the field can be found reliably. We describe the evolution of the system
from the homogeneous oscillations to the moment when thermalization is
completed. We compare our results with the Hartree--Fock approximation and
argue that some properties found for this model may be the common features of
realistic theories.


title: Bimodal Coherence in Dense Self-Interacting Neutrino Gases

abstract:
  Analytical solutions are obtained to the nonlinear equations describing
neutrino oscillations when explicit neutrino-antineutrino asymmetries are
present. Such a system occurs in the early Universe if neutrinos have a
non-zero chemical potential. Solutions to the equations lead to a new type of
coherent behavior governed by two modes. These bimodal solutions provide new
insights into dense neutrino gases and into neutrino oscillations in the early
Universe, thereby allowing one to surmise the flavor behavior of neutrinos with
a non-zero chemical potential.


title:
Strange quark distribution and corrections due to shadowing and isospin
  symmetry breaking

abstract:
  The strange sea quarks distributions of nucleons obtained by two global
analyses based on available structure function data of muon and neutrino deep
inelastic scatterings are different from the strange sea quark distribution
measured by the CCFR Collaboration from dimuon events in neutrino scattering.
We discuss possible contributions to this discrepancy from the nuclear
shadowing in the deuteron and from the isospin symmetry breaking in the sea
between the neutron and the proton.


title: GUTs with Exclusively Delta-B=1, Delta-L=0 R-Parity Violation

abstract:
  We study $R$-parity violation in the framework of GUTs, focusing on the case
that $R$-parity is broken exclusively through $\Delta B=1$, $\Delta L=0$
effective interactions. We construct two such models, an $SU(5)$
  and an $SU(5)\times U(1)_{X}$ model, in which $R$-parity breaking is induced
through interactions with extra supermassive fields. The presence of only the
Baryon Number violating operators ${d^c}{d^c}{u^c}$ requires an asymmetry
between quarks and leptons, which is achieved either by virtue of the Higgs
representations used or by modifications in the matter multiplets. The latter
possibility is realized in the second of the above models, where the
left-handed leptons have been removed from the representation in which they
normaly cohabit with the right-handed up quarks and enter as a combination of
the isodoublets in $(\bf {{\overline{5}},-3})$ and $(\bf {5,-2})$
representations. In both models the particle content below the GUT scale is
unaffected by the introduced $R$-parity breaking sector.


title: LEP1 - LEP2: Theory versus Experiment

abstract:
  The status of the standard model is briefly reviewed in the light of the most
recent set of experimental data, with particular emphasis to the limits on the
Higgs boson mass. The search for a light Higgs boson at LEP~2 is also briefly
analyzed.


title: Working Group Report on the Structure of the Proton

abstract:
  We summarize the developments on the structure of the proton that were
studied at the Workshop on "HERA Physics" that was held in Durham in September
1995. We survey the latest structure function data; we overview the QCD
interpretations of the measurements of the structure functions and of final
state processes; we discuss charm production and the spin properties of the
proton.


title: Dispersive contribution to CP violation in hyperon decays

abstract:
  Within the standard model, CP-violating asymmetries A(\Lambda^0_-) and
A(\Xi^-_-) have been estimated in short-distance calculations to occur at the
level of a few times 10^{-5}. We show here that in this model the dispersive
contribution tends to give asymmetries of similar size.


title: Colour connections in e+e- -annihilation

abstract:
  We have a very limited knowledge about how the confinement mechanism works in
processes like $\epea\epe\ra\epq\epqa\ggn\ldots\ggn$, when there are identical
colour charges. In this case the partons can be connected by a string or a
cluster chain in several different ways. We do not know if in such a situation
Nature chooses a particular configuration at random, or if some configuration
is dynamically favoured. Also in the perturbative parton cascade we have no
well founded recipe for describing the interference effects, which correspond
to non planar diagrams and are caused by identical colour charges. We have
studied two different models, and are in particular interested in the
possibility that a colour singlet gluon system hadronizes isolated from the
remainder of the state. Using double tagged events with heavy $\epc\epca$ or
$\epb\epba$ quarks, it appears to be possible to find a significant signal, if
such events appear in Nature.
  If this type of (re)connected states appear in Z decays it may also be an
indication that reconnection might appear between the decay products of two W's
in the reaction $\epea\epe\ra\gwp\gwm\ra\epq_1\epqa_2\epQ_1\epQa_2$ at LEP2.
This would be important e.g. for a precision measurement of the W mass.


title: bbbar fragmentation and B\pi correlations

abstract:
  We show that experimental data are in very good agreement with predictions
from the string fragmentation model by Bowler and Morris. We present a physical
interpretation and discuss the relation to results obtained from Perturbative
QCD and Local Hadron Parton Duality (LPHD). We also present implications for
B$\pi$ correlations and the possibility to use these as a tag to study CP
violation in B decays.


title:
Two-loop Anomalous Dimensions of Heavy Baryon Currents in Heavy Quark
  Effective Theory

abstract:
  We present results on the two-loop anomalous dimensions of the heavy baryon
HQET currents $J=(q^TC\Gamma\tau q)\Gamma'Q$ with arbitrary Dirac matrices
$\Gamma$ and $\Gamma'$. From our general result we obtain the two-loop
anomalous dimensions for currents with quantum numbers of the ground state
heavy baryons $\Lambda_Q$, $\Sigma_Q$ and $\Sigma_Q^*$. As a by-product of our
calculation and as an additional check we rederive the known two-loop anomalous
dimensions of mesonic scalar, pseudoscalar, vector, axial vector and tensor
currents $(J=\bar q\Gamma q)$ in massless QCD as well as in HQET.


title: On the triple pomeron contribution in the hard pomeron theory

abstract:
  Within the hard pomeron approach it is shown that the triple pomeron
interaction gives no contribution to the cross-section for a projectile with
large enough virtuality $g^{2}\ln Q^{2}\sim 1$. For small virtualities
$g^{2}\ln Q^{2}<<1$ its contribution is essential.


title: The Resummation of Soft Gluon in Hadronic Collisions

abstract:
  We compute the effects of soft gluon resummation for the production of high
mass systems in hadronic collisions. We carefully analyse the growth of the
perturbative expansion coefficients of the resummation formula. We propose an
expression consistent with the known leading and next-to-leading resummation
results, in which the coefficients grow much less than factorially. We apply
our formula to Drell--Yan pair production, heavy flavour production, and the
production of high invariant mass jet pairs in hadronic collisions. We find
that, with our formula, resummation effects become important only fairly close
to the threshold region. In the case of heavy flavour production we find that
resummation effects are small in the experimental configurations of practical
interest.


title:
Heavy Quark Effective Field Theory at O(1/m_Q^2). I. QCD Corrections to
  the Lagrangian

abstract:
  We present a new calculation of the renormalized HQET Lagrangian at order
O(1/m_Q^2) and discuss the consequences of the BRST invariance of QCD and the
reparameterization invariance of HQET. Our result corrects earlier, conflicting
calculations and sets the stage for the calculation of the renormalized
currents at order O(1/m_Q^2).


title: Exclusive Photoproduction of Large Momentum-Transfer K and K* Mesons

abstract:
  The reactions gamma p -> K+ Lambda and gamma p -> K* Lambda are analyzed
within perturbative QCD, allowing for diquarks as quasi-elementary constituents
of baryons. The diquark-model parameters and the quark-diquark distribution
amplitudes of proton and Lambda are taken from previous investigations of
electromagnetic baryon form factors and Compton-scattering off protons.
Unpolarized differential cross sections and polarization observables are
computed for different choices of the K and K* distribution amplitudes. The
asymptotic form of the K distribution amplitude (proportional to x1 x2) is
found to provide a satisfactory description of the K photoproduction data.


title: Electroweak Symmetry Breaking and Physics Beyond the Standard Model

abstract:
  In order to extend the Standard Model to TeV scale energies one must address
two basic questions: (1) What is the complete description of the effective
theory of fundamental particles at and below the electroweak scale? and (2)
What is the dynamics responsible for electroweak symmetry breaking? The answers
to these questions are crucial for addressing the third outstanding question of
particle physics: What are the origins of the Standard Model parameters? We
briefly summarize current theoretical approaches to answering these questions.


title: On the Mechanism of Open-Flavor Strong Decays

abstract:
  Open-flavor strong decays are mediated by $q\bar q$ pair production, which is
known to occur dominantly with \3p0 quantum numbers. The relation of the
phenomenological \3p0 model of these decays to ``microscopic" QCD decay
mechanisms has never been clearly established. In this paper we investigate
$q\bar q$ meson decay amplitudes assuming pair production from the scalar
confining interaction (sKs) and from one gluon exchange (OGE). sKs pair
production predicts decay amplitudes of approximately the correct magnitude and
D/S amplitude ratios in $b_1\to\omega\pi$ and $a_1\to\rho\pi$ which are close
to experiment. The OGE decay amplitude is found to be subdominant in most
cases, a notable exception being $^3$P$_0\to{}^1$S$_0+{}^1$S$_0$. The full
sKs~+~OGE amplitudes differ significantly from \3p0 model predictions in some
channels and can be distinguished experimentally, for example through an
accurate comparison of the D/S amplitude ratios in $b_1\to\omega\pi$ and
$a_1\to\rho\pi$.


title: Baryogenesis from Cosmic Strings at the Electroweak Scale

abstract:
  We explore the viability of baryogenesis from light scalar decays after the
electroweak phase transition. A minimal model of this kind is constructed with
new CP violating interactions involving a heavy fourth family. The departure
from thermal equilbrium must come from topological defects like cosmic strings,
and we show that almost any mechanism for producing the cosmic strings at the
electroweak scale results in a viable theory. Baryogenesis occurs in the fourth
generation but the baryon number is later transported to the visible
generations. This mechanism of indirect baryogenesis allows us to satisfy
experimental limits on the proton lifetime while still having perturbative
baryon number violation at low energies. The fourth family has very small
mixing angles which opens the possibility of distinct observable signatures in
collider experiments.


title: Neutrino Oscillations and Energy-Momentum Conservation

abstract:
  A description of neutrino oscillation phenomena is presented which is based
on relativistic quantum mechanics and includes both entangled state and source
dependent aspects, unlike both of the conventional approaches which use either
equal energies or equal momenta for the different neutrino mass eigenstates. To
second order in the neutrino masses, the standard result is recovered thus
showing an absence of source dependence to this order. The time dependence of
the wavefunction is found to be crucial to recovering the conventional result.
An ambiguity appears at fourth order in the neutrino masses which generally
leads to source dependence, but the standard formula can be promoted to this
order by a plausible convention.


title: Physical Implications of a Vector-like Extension of the Standard Model

abstract:
  Physical implications of a vector-like extension of the standard model for
heavier quarks and leptons with $SU(2)\times U(1)$ gauge symmetry and only one
Higgs doublet are discussed. This scheme incorporates infinitely many fermions,
and the chiral structure is realized by a non-vanishing analytic index of mass
matrices. The model is perturbatively well controllable, and the physical Higgs
particle generally mediates leptonic as well as quark flavor-changing processes
at a rate below the present experimental limit. This model illustrates a
general feature of models where some of the fermion masses are of non-Higgs
origin.


title:
Effects of Quark-Pomeron Coupling Structure in Diffractive Deep
  Inelastic Scattering

abstract:
  We study the contribution of diffractive $Q \bar Q$ production to the $F_2^D$
proton structure function and the longitudinal double-spin asymmetry in
polarized deep--inelastic $lp$ scattering. We show the strong dependence of the
$F_2^D$ structure function and the $A_{ll}$ asymmetry on the quark--pomeron
coupling structure.


title: Can one probe the structure function of the pomeron?

abstract:
  We discuss whether the diffractive structure functions defined by current
experiments at HERA are indeed probing the partonic structure function of the
pomeron. We observe that the {\it pseudorapidity} cuts commonly employed
require that the struck parton in the pomeron be far off mass shell in sizeable
regions of parameter space. As a result an interpretation in terms of
constituent partons within the pomeron is inadequate. One may nevertheless use
a partonic description for the {\it amplitude} for virtual photon-pomeron
scattering to compute a diffractive structure function for pseudorapidity gap
events. The resulting form may have significant scaling violation.


title: Electric dipole moments in supersymmetric theories

abstract:
  Intrinsic EDMs in microscopic systems at a level of sensitivity achievable in
experiments under way or foreseen are predicted in supersymmetric unified
theories. I describe this and other sources of measurable EDMs and I show how
these sources can be distinguished through experiments in different systems.


title: Large Majorana Mass from the Anomalous U(1) Gauge Symmetry

abstract:
  We show a new and simple model which induces large Majorana masses of
right-handed neutrinos. It is based on U(1)_X anomalous gauge symmetry, which
is cancelled by the Green-Schwarz mechanism. These Majorana masses can solve
the solar neutrino problem by the vacuum oscillation mechanism. The
superpotential of this model is scale invariant. The field contents are simple
extensions of the MSSM, which have four standard gauge singlet fields, two
extra vector-like fields, and right-handed neutrinos in addition to the MSSM.


title:
Analytic QCD running coupling with finite IR behaviour and universal
  ${\bar \alpha}_s(0)$ value

abstract:
  As is known from QED, a possible solution to the ghost-pole trouble can be
obtained by imposing the $Q^2$-analyticity imperative. Here, the pole is
compensated by the $\alpha$ non-analytic contribution that results in finite
coupling renormalization.
  We apply this idea to QCD and arrive at the $Q^2$ analytic
$\bar{\alpha}_s(Q)$. This solution corresponds to perturbation expansion, obeys
AF and, due to non-perturbative contribution, has a regular IR behaviour. It
does not contain any adjustable parameter and has a finite IR limit
$\bar{\alpha}_s(0)$ which depends only on group symmetry factors. In the
one-loop approximation it is equal to $4\pi/\beta_0 \simeq 1.40\,$ and turns
out to be surprisingly stable with respect to higher order corrections. On the
other hand, the IR behaviour of our new analytic solution agrees with recent
global low energy experimental estimates of $\bar{\alpha}_s(Q^2)$.


title:
Short-baseline neutrino oscillations and neutrinoless double-beta decay
  in schemes with an inverted mass spectrum

abstract:
  We have considered short-baseline neutrino oscillations, tritium beta-decay
and neutrinoless double-beta decay in two schemes with an inverted mass
spectrum and mixing of three and four massive neutrino fields. We have analyzed
the results of the latest experiments on the search for oscillations of
terrestrial neutrinos and we have discussed the compatibility of the LSND
indication in favor of neutrino oscillations with the results of the other
experiments. In the framework of the models under consideration, it is shown
that the observation of neutrinoless double-beta decay could allow to obtain
information about the CP violation in the lepton sector.


title: Resolution of the $\rb -\als$ crisis of the SM in an exotic ETC scenario

abstract:
  In this article we show that the $\rb -\als $ crisis of the SM can be
resolved in a commuting TC scenario with sideways gauge bosons only if the ETC
representation contains mirror technifermions. For a toy ETC model we estimate
the value of $\xi^2_t={\gel/ \guer}$ that is needed to produce the observed LEP
excess in $\rb$. It is also shown that the same value of $\xi^2_t$ resolvs the
$\als$ crisis of the SM but produces a $\delta \rho_{new}$ which is barely
within the present experimental bound.


title: Intermittency in a single event

abstract:
  The possibility to study intermittency in a single event of high multiplicity
is investigated in the framework of the $\alpha-$model. It is found that, for
cascade long enough, the dispersion of intermittency exponents obtained from
individual events is fairly small. This fact opens the possibility to study the
distribution of the intermittency parameters characterizing the cascades seen
(by observing intermittency) in particle spectra.


title: Physics of Quark--Gluon Plasma

abstract:
  In this lecture, we give a brief review of what theorists now know,
understand, or guess about static and kinetic properties of quark--gluon
plasma. A particular attention is payed to the problem of physical
observability, i.e. the physical meaningfulness of various characteristics of
$QGP$ discussed in the literature.


title: Sonoluminescence and the Heimlich Effect

abstract:
  The phenomenon of sonoluminescence (SL), originally observed some sixty years
ago, has recently become the focus of renewed interest, particularly with the
discovery that one can trap a single bubble and induce it to exhibit SL stably
over a large number of acoustical cycles.
  In this work we shall adopt a version of the provocative suggestion put
forward by Schwinger: the mechanism responsible for the radiation in SL is a
dynamic version of the Casimir effect. It has been known since Casimir's
original work in 1948 that the zero-point energy of quantum fields can be
modified by the presence of boundaries, and that these modifications generate
observable effects. For example, in Casimir's original work, the quantum
fluctuations of the electromagnetic field in the presence of a pair of
uncharged, parallel, perfectly conducting plates were shown to give rise to an
attractive force between the plates.


title: How To Find Charm in Nuclear Collisions at RHIC and LHC

abstract:
  Measurements of dilepton production from charm decay and Drell-Yan processes
respectively probe the gluon and sea quark distributions in hadronic
collisions. In nucleus-nucleus collisions, these hard scattering processes
constitute a `background' to thermal contributions from the hot matter produced
by the collision. To determine the magnitude and behavior of this background,
we calculate the hard scattering contribution to dilepton production in nuclear
collisions at RHIC and LHC at next to leading order in perturbative QCD.
Invariant mass, rapidity and transverse momentum distributions are presented.
We compare these results to optimistic hydrodynamic estimates of the thermal
dilepton production. We find that charm production from hard scattering is by
far the dominant contribution. Experiments therefore can measure the gluon
distribution in the nuclear target and projectile and, consequently, can
provide new information on gluon shadowing. We then illustrate how experimental
cuts on the rapidity gap between the leptons can aid in reducing the charm
background, thereby enhancing thermal information.


title: Is Zee Model The Model of Neutrino Masses?

abstract:
  Zee model leads naturally to two heavy, strongly degenerate and almost
maximally mixed neutrinos and to one light neutrino with small mixing. This
pattern coincides with the one needed for a solution of the atmospheric
neutrino problem by $\n_\m\A \n_\tau$ oscillations and for existence of the two
component hot dark matter in the Universe. Furthermore, the oscillations
$\bar\n_\m\A \bar\n_e$ can be in the range of sensitivity of KARMEN, LSND
experiments. Phenomenology of this scenario is considered and possibility to
check it in the forthcoming experiments is discussed. Scenario implies large
values and inverse flavour hierarchy of the couplings of the Zee boson with
fermions: $f_{e \tau} \ll f_{\mu \tau} \leq f_{e \mu} \sim 0.1$. Main
signatures of scenario are: strongly suppressed signal of $\n_\m\A \n_\tau$
oscillation in CHORUS and NOMAD experiments, so that positive result from these
experiments will rule out the scenario; possibility of observation of $\n_e\A
\n_\tau$ oscillations by CHORUS and NOMAD; corrections to the muon decay,
neutrino-electron scattering at the level of the experimental errors; branching
ratio $B(\mu \A e \gamma)$ bigger than $10^{-13}$. The solar neutrino problem
can be solved by introduction of additional very light singlet fermion without
appreciable changes of the active neutrino pattern.


title: Squeezed States and Particle Production in High Energy Collisions

abstract:
  Using the `quantum optical approach' we propose a model of multiplicity
distributions in high energy collisions based on squeezed coherent states.
  We show that the k-mode squeezed coherent state is the most general one in
describing hadronic mulitiplicity distributions in particle collision
processes, describing not only $p \bar p$ collisions but $e^{+}e^{-}$, $\nu p$
and diffractive collisions as well.
  The reason for this phenomenological fit has been gained by working out a
microscopic theory in which the squeezed coherent sources arise naturally if
one considers the Lorentz squeezing of hadrons and works in the covariant phase
space formalism .


title:
Dileptons from bremsstrahlung: going beyond the soft photon
  approximation

abstract:
  The traditional calculation of dilepton yields from bremsstrahlung relies on
the assumption that electromagnetic and strong processes factorize. We argue
that this assumption, embodied by the soft photon approximation, cannot hold
true for invariant mass spectra on very general grounds. Deriving a formula for
the dilepton cross section for pion-pion scattering that does not rely on such
factorization, we formulate the problem exactly in terms of three-particle
phase space invariants. Using a simple one boson exchange model for comparison,
we find that dilepton cross sections and yields are generally overestimated by
the soft photon approximation by factors 2--8. In extreme cases, overestimation
up to a factor 40 is possible.


title: Generalized moments and cumulants for samples of fixed multiplicity

abstract:
  Factorial moments and cumulants are usually defined with respect to the
unconditioned Poisson process. Conditioning a sample by selecting events of a
given overall multiplicity $N$ necessarily introduces correlations. By means of
Edgeworth expansions, we derive generalized cumulants which define correlations
with respect to an arbitrary process rather than just the Poisson case. The
results are applied to correlation measurements at fixed $N$, to redefining
short-range vs.\ long-range correlations and to normalization issues.


title:
Correlations, correlation integrals and application to Bose-Einstein
  interferometry

abstract:
  We review the basic notion of correlations in point processes, adapted to the
language of high energy physicists. The measurement of accessible information
on correlations by means of correlation integrals is summarized. Applications
to the measurement of Bose-Einstein interferometry as well as some pitfalls are
discussed.


title: Recent developments in rho-omega mixing

abstract:
  The topic of rho-omega mixing has received renewed interest in recent years
and has been studied using a variety of modern techniques. A brief history of
the subject is presented before summarising recent developments in the field.
The present status of our understanding is discussed.


title:
What are the right values of $\bar \Lambda$ and the heavy quark kinetic
  energy?

abstract:
  The values of two important parameters of the heavy quark effective theory,\,
$\bar \Lambda$ and $\mu_\pi^2$ (the mean value of the heavy quark three
momentum squared),\, have been determined recently in \cite {GKLW} from the
precise CLEO data on the shape of the electron spectrum in semileptonic B meson
decays. The values obtained in \cite{GKLW}: $\bar \Lambda=(0.55\pm
0.05)\,GeV,\, \mu_\pi^2=(0.35\pm 0.05)\,GeV^2,$ disagree with the result
obtained earlier in \cite{CH} from the D meson semileptonic width.
  The purpose of this note is to show that the main reason for a disagreement
is the secondary electron background present in the data,\, which influences
strongly the extracted values of $\bar \lambda$ and $\mu_\pi^2$. We determine
the amount of this background from the selfconsistency conditions,\, and
subtract it out.
  As a result,\, the values of $\bar \Lambda$ and $\mu_\pi^2$ become a factor
two smaller and agree with \cite{CH}.


title: Scaling approach to higher-twist corrections

abstract:
  Bjorken scaling is violetd. At large $x$-values ($0.7 \lesssim x \leq 1$) the
violation is mainly attributed to $\propto 1/Q^2$ (higher-twist) corrections.
We discuss how to incorporate such corrections by using a new scaling variable
$\bar x(x,Q^2)$ which accounts for the non-perturbative effects due to the
confining parton interaction in the final state. The approach can accomodate
also the remaining QCD logarithmic corrections and the behaviour of the
$F_2(x,Q^2)$ structure functions is reproduced, in a quite natural way, within
a wide kinematical range.


title: $B_s (B_d) \to \gamma \nu \bar \nu $ }

abstract:
  We study the loop induced rare decays $B_s(B_d)\to\gamma\nu\bar\nu$ within
the standard model. Both constituent quark model and pole model are used and
the branching ratios turn out to be of the orders of $10^{-8}$ for $B_s\to
\gamma \nu \bar \nu $ and $10^{-9}$ for $B_d \to \gamma \nu \bar \nu $. These
processes can be served to determine the decay constants of $B_s$ and $B_d$.


title: Relic neutralinos in a best-fitted MSSM

abstract:
  We examine the properties of relic neutralinos in the regions of the
parameter space selected by recent fits to all the electroweak observables
within the Minimal Supersymmetric Standard Model. We discuss the relic
neutralino cosmic abundance and the direct detection rates for these most
likely supersymmetric configurations. We employ the relevant experimental
bounds to constrain the set of the best-fit configurations and discuss the
discovery potential of the direct search for relic neutralinos.


title:
Dipole moments of tau as a sensitive probe for beyond standard model
  physics

abstract:
  CP violating dipole moments of leptons vanish at least to three loop order
and are estimated to be $({m_l\over Mev})\times 1.6\times 10^{- 40}$ e-cm in
the standard model (SM), where $m_l$ is the mass of the lepton. However they
can receive potentially large contributions in some beyond SM scenarios and
this makes them very sensitive probes of new physics. In this article we show
that a non universal interaction, involving leptoquarks to the quark-lepton
pair of the third generation through helicity unsuppressed couplings of the
order of ordinary gauge couplings, can generate electric and weak dipole
moments of the order of $10^{-19}$ e-cm for the tau lepton. This is greater
than pure supersymmetric (SUSY) and left-right (L-R) contributions by almost
three orders of magnitude. It is also greater than mirror fermionic
contribution by an order of magnitude.
  The measurements of $\dzt$ and $\dgt$ at LEP, SLC and TCF are expected to
reach sensitivities of $10^{-18}$ e-cm and $10^{-19}$ e-cm respectively in near
future. The observation of a non vanishing dipole moment of tau at these
facilities would therefore strongly favour superstring inspired light
leptoquark mediated interactions, over pure SUSY or L-R interactions and
perhaps also mirror generated mixings without some sort of quark-lepton
unification as its origin.


title:
Generalized screening theorem for Higgs decay processes in the
  two-doublet model

abstract:
  The radiative corrections to the decay processes of the neutral ($CP$-even)
Higgs boson ($H$) into a longitudinal gauge boson pair, {\it i.e.}, $H
\rightarrow Z_{L}Z_{L}$ and $H \rightarrow W_{L}^{+}W_{L}^{-}$ are analyzed in
the two-Higgs doublet model by assuming that all of the Higgs boson masses are
much greater than the $W$ and $Z$ bosons'. These calculations are motivated to
see if one could see potentially large virtual effects to these decay rates due
to the charged and $CP$-odd neutral Higgs boson masses ($m_{G}$ and $m_{A}$,
respectively) which are supposed to be larger than $m_{H}$. It is pointed out
that, although the radiative corrections to the decay width $\Gamma
(H\rightarrow W_{L}^{+}W_{L}^{-})$ depend sensitively in general on $m_{G}$ and
$m_{A}$, there occurs a screening effect, {\it i.e.,} cancellation in leading
terms once we set $m_{G}=m_{A}$, so that the radiative corrections tend to be
minimized. It is also pointed out that the decay rate $\Gamma (H\rightarrow
Z_{L}Z_{L})$ is fairly insensitive to the other heavier Higgs masses and is
possibly a good measuring tool of the Higgs mixing angle. The mechanism of
these screening phenomena in the Higgs decays is explained on the basis of a
new screening theorem, which we postulate with reference to the custodial
symmetry in the Higgs potential.


title:
Physically Motivated Approximation to a Parton Distribution Function in
  QCD

abstract:
  It has been suggested that parton distributions in coordinate space, so
called Ioffe-time distributions, provide a more natural object for
non-perturbative methods compared to the usual momentum distributions. In this
paper we argue that the shape of experimentally determined Ioffe-time
distributions of quarks in a nucleon target clearly indicates separation of
longitudinal scales, which is not easily recognizable in terms of conventional
longitudinal momentum space considerations. We demonstrate how to use this
observation to determine parton distributions, using non-perturbative
information about the first few moments and the Regge asymptotics at small $x$.


title: QCD evolution of the gluon density in a nucleus

abstract:
  The Glauber approach to the gluon density in a nucleus, suggested by A.
Mueller, is developed and studied in detail. Using the GRV parameterization for
the gluon density in a nucleon, the value as well as energy and $Q^2$
dependence of the gluon density in a nucleus is calculated. It is shown that
the shadowing corrections are under theoretical control and are essential in
the region of small $x$. They change crucially the value of the gluon density
as well as the value of the anomalous dimension of the nuclear structure
function, unlike of the nucleon one. The systematic theoretical way to treat
the correction to the Glauber approach is developed and a new evolution
equation is derived and solved. It is shown that the solution of the new
evolution equation can provide a selfconsistent matching of ``soft" high energy
phenomenology with ``hard" QCD physics.


title: The Spin--Symmetry of the Quark Model

abstract:
  Corrections to the exact heavy--quark symmetry results are expected to follow
the $1/m_{Q}$ mass effect of the heavy--quark. We show, by an explicit
calculation, that there is something other than the mass effect that suppresses
the breaking of the spin symmetry.


title:
QCD corrections to the production of a heavy quark pair plus a hard
  photon in $e^+ e^-$ annihilation

abstract:
  We present complete results for the $O(\alpha_s)$ corrections to the
production of a heavy quark pair plus a hard photon, in $e^+ e^-$ annihilation,
including both photon and $Z$ intermediate states. Virtual corrections are
calculated analytically in $4 - 2 \epsilon$ dimensions, together with the soft
approximation to the real emission diagrams. After cancellation of infrared
divergences, real and virtual contributions are combined numerically to obtain
the cross section for the production of two heavy quark jets plus a hard photon
in next-to-leading order. The resulting fully differential cross section can be
used to construct arbitrary distributions with the desired experimental cuts.


title:
Bound state studies in light-front QCD of mesons containing at least one
  heavy quark

abstract:
  We present a QCD bound-state calculation based on a renormalization
group-improved light-front Hamiltonian formalism. The QCD Hamiltonian is
determined to second order in the coupling, and it includes two-body confining
interactions. We make a momentum expansion, obtaining an equal-time-like
Schrodinger equation. This is solved for quark-antiquark constituent states,
and we obtain a set of self-consistent parameters by fitting B mesons. Applying
the approach to charmonium spectra leads to a prediction of the hyperfine
splitting between J/$\psi$(1S) and $\eta_c$(1S) which is in good agreement with
experiment.


title:
A complete analysis of FCNC and CP constraints in general SUSY
  extensions of the standard model

abstract:
  We analyze the full set of constraints on gluino- and photino-mediated SUSY
contributions to FCNC and CP violating phenomena. We use the mass insertion
method, hence providing a model-independent parameterization which can be
readily applied in testing extensions of the MSSM. In addition to clarifying
controversial points in the literature, we provide a more exhaustive analysis
of the CP constraints, in particular concerning
$\varepsilon^\prime/\varepsilon$. As physically meaningful applications of our
analysis, we study the implications in SUSY-GUT's and effective supergravities
with flavour non-universality. This allows us to detail the domain of
applicability and the correct procedure of implementation of the FC mass
insertion approach.


title: Power Corrections and Renormalons in Deep Inelastic Structure Functions

abstract:
  We study the power corrections (infrared renormalon contributions) to the
coefficient functions for non-singlet deep inelastic structure functions due to
gluon vacuum polarization insertions in one-loop graphs. Remarkably, for all
the structure functions $F_1$, $F_2$, $F_3$ and $g_1$, there are only two such
contributions, corresponding to $1/Q^2$ and $1/Q^4$ power corrections. We
compute their dependence on Bjorken $x$. The results could be used to model the
dominant higher-twist contributions.


title: Neutrino Mass in Physics and Astrophysics

abstract:
  The symmetry between quarks and leptons suggests that neutrinos should have
mass. As embodied in the grand unified theory SO(10) this yields masses that
can only be detected by neutrino oscillations. Such oscillations could be very
important for supernova physics. Present observations of solar neutrinos when
combined with standard solar model calculations imply particular parameters for
neutrino masses and mixings. If the solar model is somewhat relaxed quite
different possibilities emerge, which yield very different predictions for
future experiments.


title: The effective chiral lagrangian of the MSM at one and two loop order

abstract:
  The formalism of the matching conditions between transverse connected Green
functions is extended to include the two next to leading corrections, namely
the two-loop $M_{H}^{2}$ and the one-loop $1/M_{H}^{2}$ contributions to the
coefficients of the electroweak chiral lagrangian which are relevant to the
LEP1 physics: $a_{0}$, ${\hat a}_{1}$ and ${\hat a}_{8}$. We derive general
expressions for these three coefficients in terms of just bare gauge boson
self-energies. By means of the screening theorem, it is shown that the same
expressions can be used to get directly from a MSM calculation, the leading
Higgs mass contribution to these coefficients at each loop order. In a more
general framework, we solve the problems concerning the loss of gauge
invariance and the inclusion of only gauge invariant operators by proposing a
new formulation of the matching conditions at two and higher loop order. As an
example of the usefulness of using an electroweak chiral lagrangian to
parametrize the MSM, we will give a simple proof of an extra screening for the
renormalized photon self-energy in the on-shell scheme at all orders. In
addition it is shown the automatic cancellation of the unphysical $M_{H}^4$
terms in the other gauge boson self-energies at two-loops in this scheme.
Finally we will apply the obtained electroweak chiral lagrangian to compute the
different Higgs mass contributions to the bosonic part of $\Delta \rho$,
$\Delta r$ and $\Delta \kappa$, analyzing carefully the hierarchy between
corrections.


title: Light-Cone Quantization and Hadron Structure

abstract:
  In this talk, I review the use of the light-cone Fock expansion as a
tractable and consistent description of relativistic many-body systems and
bound states in quantum field theory and as a frame-independent representation
of the physics of the QCD parton model. Nonperturbative methods for computing
the spectrum and LC wavefunctions are briefly discussed. The light-cone Fock
state representation of hadrons also describes quantum fluctuations containing
intrinsic gluons, strangeness, and charm, and, in the case of nuclei, "hidden
color". Fock state components of hadrons with small transverse size, such as
those which dominate hard exclusive reactions, have small color dipole moments
and thus diminished hadronic interactions; i.e., "color transparency". The use
of light-cone Fock methods to compute loop amplitudes is illustrated by the
example of the electron anomalous moment in QED. In other applications, such as
the computation of the axial, magnetic, and quadrupole moments of light nuclei,
the QCD relativistic Fock state description provides new insights which go well
beyond the usual assumptions of traditional hadronic and nuclear physics.


title:
A Multi-scale Subtraction Scheme and Partial Renormalization Group
  Equations in the $O(N)$-symmetric $\phi^4$-theory

abstract:
  To resum large logarithms in multi-scale problems a generalization of $\MS$
is introduced allowing for as many renormalization scales as there are generic
scales in the problem. In the new \lq\lq minimal multi-scale subtraction
scheme'' standard perturbative boundary conditions become applicable. However,
the multi-loop beta functions depend on the various renormalization scale
ratios and a large logarithms resummation has to be performed on them. Using
these improved beta functions the \lq\lq partial'' renormalization group
equations corresponding to the renormalization point independence of physical
quantities allows one to resum the logarithms. As an application the leading
and next-to-leading order two-scale analysis of the effective potential in the
$O(N)$-symmetric $\phi^4$-theory is performed. This calculation indicates that
there is no stable vacuum in the broken phase of the theory for $1<N\leq4$.


title: The Quark/Antiquark Asymmetry of the Nucleon Sea

abstract:
  Although the distributions of sea quarks and antiquarks generated by
leading-twist QCD evolution through gluon splitting $g \rightarrow \bar q q$
are necessarily CP symmetric, the distributions of nonvalence quarks and
antiquarks which are intrinsic to the nucleon's bound state wavefunction need
not be identical. In this paper we investigate the sea quark/antiquark
asymmetries in the nucleon wavefunction which are generated by a light-cone
model of energetically-favored meson-baryon fluctuations. The model predicts
striking quark/antiquark asymmetries in the momentum and helicity distributions
for the down and strange contributions to the proton structure function: the
intrinsic $d$ and $s$ quarks in the proton sea are predicted to be negatively
polarized, whereas the intrinsic $\bar d$ and $\bar s$ antiquarks give zero
contributions to the proton spin. Such a picture is supported by experimental
phenomena related to the proton spin problem and the violation of the
Ellis-Jaffe sum rule. The light-cone meson-baryon fluctuation model also
suggests a structured momentum distribution asymmetry for strange quarks and
antiquarks which could be relevant to an outstanding conflict between two
different determinations of the strange quark sea in the nucleon. The model
predicts an excess of intrinsic $d \bar d$ pairs over $u \bar u$ pairs, as
supported by the Gottfried sum rule violation. We also predict that the
intrinsic charm and anticharm helicity and momentum distributions are not
identical.


title: Constraints on CP violating four-fermion interactions

abstract:
  It has been shown that CP violating electron-nucleon and nucleon-nucleon
interactions can induce atomic electric dipole moments and are therefore
constrained from experimental data. We show that using the experimental upper
bounds on neutron and electron electric dipole moments, one can also obtain
constraints, in some cases better ones, on these interactions. In addition
stringent constraints can also be obtained for muon-quark and tauon-quark
four-fermion CP violating interactions, which cannot be constrained from atomic
electric dipole moment experiments.


title: Estimate for the $0^{++}$ glueball mass in QCD

abstract:
  We obtain accurate result for the lightest glueball mass of QCD in 3
dimensions from lattice Hamiltonian field theory. Using the dimensional
reduction argument, a good approximation for confining theories, we suggest
that the $0^{++}$ glueball mass in 3+1 dimensional QCD be about $1.71$ GeV.