title: Fermionic fluctuation corrections to bubble nucleation

abstract:
  We determine the fermionic corrections to the nucleation rate of bubbles at
the electroweak phase transition. The fermion determinant is evaluated exactly
and by using the gradient expansion. The gradient expansion is found to be a
reliable approximation and is used to extrapolate to the large values of $\nu_n
= (2n+1)\pi T$ needed in the Matsubara sum. The contribution to effective
action is found to be negative and to be given, essentially, by the gradient
terms, the finite part of the wave function renormalization. Only the top quark
contribution is evaluated, it is of the same order as the Higgs- and W-boson
contributions found previously, but of opposite sign.


title:
A Constraint to the Parity-Conserving Parameter of the
  Neutron-Antineutron Oscillations

abstract:
  The phenomenology of neutrino oscillations is extended to the neutron-
antineutron oscillations predicted by the grand unified theories. There are six
parameters in general describing the one-flavor oscillations: two real Majorana
masses (of opposite signs), three Euler's angles, and a phase multiplier "chi".
The sum of the Majorana masses, treated as a small parity- violating parameter
"epsilon", induces the nuclear decays (A,Z) -> (A-2,Z) and determines the
oscillation rate of neutrons in the vacuum. We derive a constraint to a small
parity-conserving parameter "epsilon-prime" representing a combination of two
Euler's angles. This parameter gives no significant contribution to the neutron
oscillation rate in the vacuum, while contributes to the nuclear decay rate.
The nuclear stability implies "epsilon-prime" < 1/year. Absence of the vacuum
neutron oscillations together with existence of the nuclear decays (A,Z) ->
(A-2,Z) would become simplest manifestation of the "epsilon-prime" =/ 0.


title: A New Twist on $Z \to b {\bar b}$

abstract:
  A new mechanism is proposed to explain the "anomaly" in $Z \rightarrow b
{\bar b}$ resulting in a prediction of a new, non-sequential fourth family
whose masses could all be below $M_W$, thus opening up an exciting porpect for
near-future discoveries at LEP2 and possibly at the Tevatron.


title:
On the Thermal Regeneration Rate for Light Gravitinos in the Early
  Universe

abstract:
  We investigate the light gravitino regeneration rate in the early Universe in
models based on $N=1$ supergravity. Motivated by a recent claim by Fischler, we
evaluate finite-temperature effects on the gravitino regeneration rate due to
the hot primordial plasma for a wide range of the supersymmetry-breaking scale
$F$. We find that thermal corrections to the gravitino pole mass and to the
Goldstino coupling are negligible for a wide range of temperatures, thereby
justifying the extension of the equivalence theorem for the helicity-1/2
gravitino and Goldstino to a hot primordial plasma background. Utilizing the
Braaten-Pisarski resummation method, the helicity-1/2 gravitino regeneration
rate is found to be $0.25 \alpha_s(T) \log(1/\alpha_s(T))|{m_{\rm soft}/F}|^2
T^3(1 + \alpha_s(T) \log(1/\alpha_s(T)) + T^2 / |F|)$ up to a calculable,
model-dependent ${\cal O}(1)$ numerical factor. We review the implications of
this regeneration rate for supergravity cosmology, focusing in particular on
scenaria for baryogenesis.


title: What can we learn from the $Z \to b\bar{b} $ vertex?

abstract:
  I stress the fact that a complete study of possible New Physics effects in
the $Z \rightarrow b\bar{b}$ vertex requires a combined analysis of the ratio
$R_b= \Gamma(Z \rightarrow b\bar{b})/ \Gamma(Z \rightarrow hadrons)$ and the
longitudinally polarized forward backward asymmetry, $A_b$.
  This is illustrated with a number of models such as the two Higgs-doublet
model, the MSSM, Technicolour and models with an extra $Z'$. The use of
effective lagrangean techniques is briefly discussed.


title:
Coarse-Grained Fluctuation Probabilities in the Standard Model and
  Subcritical Bubbles

abstract:
  We compute systematically the probability for fluctuations of the Higgs
field, averaged over a given spatial scale, to exceed a specified value, in the
Standard Model. For the particular case of interest of averages over one
coherence volume we show that, even in the worst possible case of taking the
one-loop improved effective potential parameters, the probability for the field
to fluctuate from the symmetric to the asymmetric minimum before the latter
becomes stable is very small for Higgs masses of the order of those of the $W$
and $Z$ bosons, whereas the converse is more likely. As such, metastability
should be satisfied dynamically at the Electroweak phase transition and its
dynamics should therefore proceed by the usual mechanism of bubble nucleation
with subcritical fluctuations playing no particularly relevant role in it.


title:
W ANOMALOUS MOMENTS AND THE POLARIZATION ASYMMETRY ZERO IN gamma e --> W
  nu

abstract:
  We show from general principles that there must be a center of mass energy,
$\sqrt s_0$, where the polarization asymmetry $A=\Delta \sigma({\gamma e \to W
\nu })/ \sigma({\gamma e \to W \nu })$ for circularly-polarized photon and
electron beams vanishes. In the case of the Standard Model, the crossing point
where the asymmetry changes sign occurs in Born approximation at $\sqrt
s_{\gamma e} = 3.1583\ldots M_W \simeq 254$ GeV. We demonstrate the sensitivity
of the position of the polarization asymmetry zero to modifications of the SM
trilinear $\gamma W W$ coupling. Given reasonable assumptions for the
luminosity and energy range for the Next Linear Collider(NLC) with a
backscattered laser beam, we show that the zero point, $\sqrt s_0$, of the
polarization asymmetry may be determined with sufficient precision to constrain
the anomalous couplings of the $W$ to better than the 1\% level at $95\%$ CL.
In addition to the fact that only a limited range of energy is required, the
polarization asymmetry measurements have the important advantage that many of
the systematic errors cancel in taking cross section ratios. The position of
the zero thus provides an additional weapon in the arsenal used to probe
anomalous trilinear gauge couplings.


title: Matching the HQET to Coulomb Type Bound States

abstract:
  We show that the infinite imaginary anomalous dimensions of certain heavy
quark-antiquark currents in the HQET arise due to an inappropriate commutation
of two limits, namely coinciding velocities and infinite cut-off. This
commutation is not apparent when dimensional regularization is used, but it can
be made manifest in a cut-off regularization. We argue that operators
containing heavy quark and antiquark fields with the same velocity in the HQET
must not be matched to perturbative QCD but to Coulomb-type bound state
contributions. We show how to do so at one loop level.


title: THE ORTHOPOSITRONIUM DECAY PUZZLE AND PRIMORDIAL NUCLEOSYNTHESIS

abstract:
  The discrepancy between the experimental decay rate of orthopositronium
(o-Ps) and the QED theoretical prediction can be solved by invoking decays of
o-Ps into exotic particles with branching ratios of the order of 10^{-3}. We
show that considerations based on primordial nucleosynthesis and effective
Lagrangians place a very stringent upper bound: B = Gamma(o-Ps -> ``exotic'' +
...)/Gamma(o-Ps) <= 2 x 10^{-15}, ruling out the exotic decay solution to the
puzzle.


title: How strong can the coupling of leptonic photons be?

abstract:
  Consequences of possible existence of leptonic photon are considered for a
range of values of leptonic charge. In the case of a strong Coulomb-like
leptonic repulsion between electrons the existence of ordinary condensed matter
is impossible: antineutrinos cannot neutralize this destructive repulsion. The
upper limit of leptonic charge is inferred from the E\"{o}tv\"os type
experiments. If however there exist light stable scalar bosons with leptonic
charge (e.g. singlet antisneutrinos) they may neutralize the electron
repulsion. Possible experimental manifestations of such leptonic bosons in
gases and condensed matter are briefly discussed.


title: Magnetic Monopole and the Finite Photon Mass: Are They Compatible?

abstract:
  We analyze the role played by the gauge invariance for the existence of Dirac
monopole. To this end, we consider the electrodynamics with massive photon and
ask if the magnetic charge can be introduced there. We show that the derivation
of the Dirac quantization condition based on the angular momentum algebra
cannot be generalized to the case of massive electrodynamics. Possible
implications of this result are briefly discussed.


title: Moments of the photon spectrum in the inclusive $B\to X_s\gamma$ decay

abstract:
  The moments of the photon spectrum in the inclusive $B\to X_s\,\gamma$ decay
can be calculated to order $\alpha_s$ accuracy at present, without knowing the
$\alpha_s$ corrections to the effective Hamiltonian. We discuss the standard
model predictions, and how the moments of the photon spectrum are related to
certain matrix elements of the heavy quark effective theory. The sensitivity of
these moments to new physics is small, and they provide a model-independent
determination of the $b$ quark pole mass (at order $\alpha_s$), or
equivalently, the matrix elements $\bar\Lambda$ and $\lambda_1$ of the
effective theory.


title: Form Factors for Exclusive Semileptonic $B$--Decays

abstract:
  We developed the new parton model approach for exclusive semileptonic decays
of $B$-meson to $D,~D^*$ by extending the inclusive parton model, and by
combining with the results of the HQET, motivated by Drell-Yan process. Without
the nearest pole dominance ans\"atze, we {\bf derived} the dependences of
hadronic form factors on $q^2$. We also calculated numerically the slope of the
Isgur-Wise function, which is consistent with the experimental results.


title: On the Coulomb Effects on the W Line Shape at LEP2

abstract:
  One of the most powerful methods for obtaining a precision measurement of M_W
at LEP2 is from direct reconstruction of the invariant mass distribution of W
bosons produced in e+e- --> W+W-. We investigate the effects on the W line
shape, and in particular on the average invariant mass, of phase-space and
first-order Coulomb corrections. The latter are shown to have a non-negligible
effect on the reconstructed mass, inducing shifts of order -20 MeV at collision
energies above threshold, compared to the Born approximation cross section. The
sign and magnitude of the effect can be understood in a simple model
calculation in which one of the W bosons is assumed to be stable.


title:
Chiral Prediction for the $\pi N$ Scattering Length $a^-$ to Order
  ${\cal O}(M_\pi^4)$

abstract:
  We evaluate the S-wave pion--nucleon scattering length $a^-$ in the framework
of heavy baryon chiral perturbation theory up--to--and--including terms of
order $M_\pi^4$. We show that the order $M_\pi^4$ piece of the isovector
amplitude at threshold, $T^-_{\rm thr}$, vanishes exactly. We predict for the
isovector scattering length, $0.088 \, M_{\pi^+}^{-1} \le a^- \le 0.096 \,
M_{\pi^+}^{-1}$.


title: On the Marriage of Chiral Perturbation Theory and Dispersion Relations

abstract:
  I describe the methodology for the use of dispersion relations in connection
with chiral perturbation theory. The conditions for matching the two formalisms
are given at $O(E^2)$ and $O(E^4)$. The two have several complementary
features, as well as some limitations, and these are described by the use of
examples, which include chiral sum rules related to the Weinberg sum rules,
form factors, and a more complicated reaction, $\gamma \gamma \rightarrow \pi
\pi$. (Invited talk presented at the International Workshop on Chiral Dynamics
in Hadrons and Nuclei, Feb 6-10, 1995, Seoul, Korea)


title: Dred, universality and the superparticle spectrum

abstract:
  Recent work on the use of dimensional reduction for the regularisation of
non--supersymmetric theories is reviewed. It is then shown that there exists a
class of theories for which a universal form of the soft supersymmetry breaking
terms is invariant under renormalisation. It is argued that this universal form
might be approached as an infra--red fixed point for the unified theory above
the unification scale. The superparticle spectrum is calculated for these
theories.


title: Strong coupling of excited heavy mesons

abstract:
  We compute the strong coupling constant $G_{B^{**} B \pi} \; (G_{D^{**} D
\pi})$, where $B^{**}$ ($D^{**}$) is the $0^+$ $P-$wave $b \bar q \; (c \bar
q)$ state, by QCD sum rules and by light-cone sum rules. The two methods give
compatible results in the limit $m_Q \to \infty$, with a rather large value of
the coupling constant. We apply the results to the calculation of the hadronic
widths of the positive parity $B$ and $D$ states and to the chiral loop
contribution to the ratio $f_{D_s}/f_D$.


title:
WWGENPV - A Monte Carlo Event Generator For Four-Fermion Production in
  $e^+ e^- \to W^+ W^- \to 4f$

abstract:
  The Monte Carlo program {\tt WWGENPV}, designed for computing distributions
and generating events for the four-fermion process $e^+ e^- \to W^+ W^- \to
4f$, is described. It is based on the calculation of the exact tree-level
matrix element of the four-fermion reaction and includes initial-state
radiation in the leading-log approximation within the structure function
approach. The program can be used in a two-fold way: as a Monte Carlo
integrator for weighted events, providing predictions for the total cross
section, the $W$ invariant-mass distribution, the radiative energy and
invariant-mass loss; as a true event generator of unweighted events, useful for
simulation purposes.


title:
Double Pion Photoproduction on the Nucleon: Study of the Isospin
  Channels

abstract:
  A model for the gamma p ----> pion+ pion- p reaction developed earlier is
extended to account for all isospin channels. The model includes N,
Delta(1232), N^*(1440) and N^*(1520) as intermediate baryonic states and the
rho-meson as an intermediate two pion resonance. Although many terms contribute
to the cross section, some channels exhibit particular sensitivity to certain
mechanisms of resonance excitation or decay and the reactions provide novel
information on such mechanisms. In particular the gamma N ----> N^*(1520) ---->
Delta(1232) pion process affects all the channels and is a key ingredient in
the interpretation of the data. Comparison is made with all available data and
the agreement is good in some channels. The remaining discrepancies in some
other channels are discussed.


title: First Lattice Calculation of The B-meson Binding and Kinetic Energies

abstract:
  We present the first lattice calculation of the B-meson binding energy
$\labar$ and of the kinetic energy $-\lambda_1/2 m_Q$ of the heavy-quark inside
the pseudoscalar B-meson. This calculation has required the non-perturbative
subtraction of the power divergences present in matrix elements of the
Lagrangian operator $\bar h D_4 h$ and of the kinetic energy operator $\bar h
\vec D^2 h$. The non-perturbative renormalisation of the relevant operators has
been implemented by imposing suitable renormalisation conditions on quark
matrix elements, in the Landau gauge. Our numerical results have been obtained
from several independent numerical simulations at $\beta=6.0$ and $6.2$, and
using, for the meson correlators, the results obtained by the APE group at the
same values of $\beta$. Our best estimate, obtained by combining results at
different values of $\beta$, is $\labar =190 \err{50}{30}$ MeV. For the
$\overline{MS}$ running mass, we obtain $\overline {m}_b(\overline {m}_b) =4.17
\pm 0.06$ GeV, in reasonable agreement with previous determinations. From a
subset of 36 configurations, we were only able to establish a loose upper bound
on the $b$-quark kinetic energy in a $B$-meson, $\lambda_1=\langle B \vert \bar
h \vec{D}^{2} h \vert B \rangle /(2 M_B )<$~1\, GeV$^2$. This shows that a much
larger statistical sample is needed to determine this important parameter.


title: BOSE-FERMI SYMMETRY: A CRUCIAL ELEMENT IN ACHIEVING UNIFICATION

abstract:
  This talk is dedicated to honor the memory of Professor S.N. Bose. I survey
the crucial roles played by Bose-Fermi symmetry in all recent attempts at
higher unification, which include the ideas of (i) the conventional approach to
grand unification; (ii) the preonic approach; and (iii) superstrings.


title: BEAUTY HADRON PRODUCTION AT HERA-B ENERGY IN DUAL PARTON MODELS

abstract:
  Production of charmed and beauty mesons and baryons in hadron-nucleon
collisions at not very high energy is considered in the framework of the
Quark-Gluon String Model. We take into account the possible corrections to the
model which disappear at asymptotically high energies but could be important at
comparatively low energies, essentially in the case of heavy flavour
production. The case of nuclear targets is also considered and the
$A$-dependence of charmed and beauty hadron yields is calculated. Predictions
for the case of beauty hadron production at $\sqrt{s}$ = 39 GeV are presented.


title: Inclusive and Exclusive Semi-Leptonic Decays of $B$ Mesons

abstract:
  In this paper, the semileptonic decays of heavy mesons are treated fully
relativistically. By means of an effective vertex, the effect of Fermi momentum
are included both at the inclusive and at the exclusive levels, and the spin of
both parent and daughter particles are taken into account. The differential
decay rates with respect to the lepton energy and momentum transfer are
compared with data from ARGUS and CLEO.


title: CP-Violation and the Quark Mass Matrices

abstract:
  We study a class of quark mass matrix models with the $\cal CP$-violating
phase determined through making the $\cal CP$-violating parameter $J$ an
extremum. These models assume that $m_u \ll m_c \ll m_t$ and that $m_d \ll m_s
\ll m_b$. They have $\left|{V_{ub}\over{V_{cb}}}\right|\approx{\sqrt{m_u
\over{m_c}}}$, $\left|{V_{td}\over{V_{ts}}}\right|\approx{\sqrt{m_d
\over{m_s}}}$ and $|V_{us}|\approx|V_{cd}|\approx{\sqrt{{m_d \over{m_s}}+{m_u
\over{m_c}}}}$. The Wolfenstein parameters $\rho$ and $\eta$ are found to be
related by $\rho\approx\eta^2$. Finally, we examine a special class of such
models where the masses are constrained to be roughly in geometric progression.
Further application of the extremal condition to $J$ then leads to ${\sqrt{m_d
\over{m_s}}}\approx 3{\sqrt{m_u \over{m_c}}}$ and hence
$\eta\approx\frac{1}{3}$, for maximal $J$.


title: Winding Number Correlation Functions and Cosmic String Formation

abstract:
  We develop winding number correlation functions that allow us to assess the
role of field fluctuations on vortex formation in an Abelian gauge theory. We
compute the behavior of these correlation functions in simple circumstances and
show how fluctuations are important in the vicinity of the phase transition. We
further show that, in our approximation, the emerging population of
long/infinite string is produced by the classical dynamics of the fields alone,
being essentially unaffected by field fluctuations.


title: WILSON'S EXPANSION WITH POWER ACCURACY

abstract:
  Because of the infrared renormalons, it is difficult to get power accuracy in
the traditional approach to the Wilson's operator product expansion. Based on a
new perturbative renormalization scheme for power-divergent operators, I
propose a practical version of the OPE that allows to calculate power
corrections to desired accuracy. The method is applied to the expansion of the
vector-current correlation function in QCD vacuum, in which field theoretical
status of the gluon condensate is discussed.


title: $R_b$ in supersymmetric models

abstract:
  We compute the supersymmetric contribution to $R_{b}\equiv \Gamma (Z\to
b{\bar b})/\Gamma (Z\to {\rm hadrons})$ in a variety of supersymmetric models.
In the context of supergravity models with universal
soft-supersymmetry-breaking and radiative electroweak breaking we find $R^{\rm
susy}_b\lsim0.0004$, which does not shift significantly the Standard Model
prediction ($R^{\rm SM}_b=0.2157$ for $m_t=175\GeV$; $R^{\rm
exp}_b=0.2204\pm0.0020$). We also compute $R_b$ in the minimal supersymmetric
standard model (MSSM), and delineate the region of parameter space which yields
interestingly large values of $R_b$. This region entails light charginos and
top-squarks, but is {\em strongly} restricted by the {\em combined} constraints
from $B(b\to s\gamma)$ and a not-too-large invisible top-quark branching ratio:
only a few percent of the points with $R^{\rm susy}_b>0.0020\,(1\sigma)$ are
allowed.


title: Summary of the XXX Rencontre de Moriond QCD Session

abstract:
  The main topics covered in this summary talk are the Large Hadron Collider,
heavy ion collisions, renormalons, parton distribution functions, measurements
of the strong coupling and the top quark. Of special interest this year was the
discovery of the top quark by the CDF and D0 groups at Fermilab. I conclude
that the evidence is compelling and that the best fit of the Standard Model top
hypothesis to the data gives a top mass of $170 +/- 9 GeV with a good
chisquared.


title:
Detecting the intermediate-mass Higgs boson through the associate
  production channel pp --> t + anti-t + H + X

abstract:
  We examine the detection of the intermediate-mass Higgs boson (IMH) at LHC
through the associate production channel pp-->t+(anti-t)+H+X-->l+photon+
photon+X'. It is shown that by applying kinematic cuts or b-tagging on the
final state jets, the main backgrounds of W(-->l+nu)+photon+photon+(n-jet) can
be reduced substantially without significant loss of signals. It is possible to
detect the Higgs boson at LHC through the pp-->t+(anti-t)+H+X channel using a
modest photon detector with mass resolution of about 3% of the photon pair
invariant mass.


title:
Relativistic Description of Exclusive Semileptonic Decays of Heavy
  Mesons

abstract:
  Using quasipotential approach, we have studied exclusive semileptonic decays
of heavy mesons with the account of relativistic effects. Due to more complete
relativistic description of the $s$ quark more precise expressions for
semileptonic form factors are obtained. Various differential distributions in
exclusive semileptonic decays of heavy mesons are calculated. It is argued that
consistent account of relativistic effects and HQET motivated choice of the
parameters of quark-antiquark potential allow to get reliable value for the
ratio $A_2(0)/A_1(0)$ in the $D\to K^*l\nu_l$ decay as well as the
ratio~$\Gamma(D\to K^*l\nu_l)/\Gamma(D\to Kl\nu_l)$. All calculated branching
ratios are in accord with available experimental data.


title: Supersymmetric radiative corrections to neutrino indices of refraction

abstract:
  We compute the one-loop effects on the neutrino propagation through matter
induced by virtual supersymmetric particles. We show that, in the minimal
version of the supersymmetric standard model, a non-degeneracy between sleptons
of the second and third generations can have sizeable effects on the
$\nu_\mu$--$\nu_\tau$ oscillations in matter. In particular, we discuss how
this could affect the detection of the energetic neutrino fluxes arising from
annihilation of supersymmetric dark matter in the center of the sun.


title: Effective couplings and Perturbative Unification

abstract:
  In this paper we study the influence of the threshold effects due to massive
degrees of freedom in the evolution with scale of gauge coupling constants. We
first describe in detail the (standard) mass dependent renormalization
prescription we use. This guides us to introduce and work with effective
couplings, which are finite, process independent, and include complete
threshold effects. We compute the evolution of the effective couplings in both,
the Standard Model and its Minimal Supersymmetric extension, from \mz\ to the
high energy region. We find that the effects from thresholds due to the
standard massive gauge bosons are non--negligible, contrary to what is
generally assumed when using other, less--accurate, descriptions of the
thresholds, as for example in the step--function approximation. Moreover, we
find that thresholds are relevant when studying perturbative SUSY unification,
changing the conclusions reached when using the step--function approach. We
find that threshold effects bring conflict between the known experimental data
at $m_Z$, the naturalness upper bound on the masses of SUSY partners and the
$perturbative$ unification of couplings.


title:
The ratio $F_2^n/F_2^p$ from the analysis of data using a new scaling
  variable

abstract:
  We analyze the proton and deuteron structure functions at large $x$ using a
recently introduced scaling variable $\bar x$. This variable includes power
corrections to $x$-scaling, and thus allows us to reach the Bjorken limit at
moderate $Q^2$. Using available data we extract the ratio $F_2^n(x)/F_2^p(x)$
for $x\leq 0.85$. Contrary to earlier expectations this ratio tends to the
value $\sim$2/3 for $x\to 1$, which corresponds to the quark model prediction
for equal distributions of valence quarks.


title:
LARGE LOGARITHM BEHAVIOUR OF e^+e^- JET CROSS SECTIONS AND EVENT SHAPE
  DISTRIBUTIONS IN O(alpha_s^2)

abstract:
  We have calculated the leading and next-to-leading logarithm coefficients of
$O(\alpha_s^2)$ $e^+e^-$ annihilation jet cross sections, thrust distribution
and energy-energy correlation in the two-jet limit when the jet resolution and
the event shape variables vanish. We have compared our results with
expectations based on leading logarithm approximations used to resum the
pertubative cross sections where this is possible. There is good agreement for
the leading and next-to-leading coefficients of jet cross sections in the
Durham scheme. Also for the thrust distribution and energy-energy correlation
we find results which are consistent with the leading logarithm predictions.


title: A MODEL FOR THE CHARMED $D_s^{+}$ MESON DECAYS INTO THREE PIONS

abstract:
  We propose a phenomenological three component model describing the decay
amplitude of the process $D_{s}^{+} \ra 3\pi$. The first component is a
constant background, the second one is a Breit-Wigner amplitude associated to a
quasi two-body $f_{0}(980) \pi^{+}$ state and the third one another
Breit-Wigner amplitude corresponding to a possible quasi two-body $\rho(770)
\pi$ state. We show that it is possible to reproduce the observed total rate
for $D_{s}^{+} \ra \pi^{+}\pi^{+}\pi^{-}$ as well as the two other measured
branching ratios for the non resonant part and the resonant $f_{0}\pi^{+}$ one.
Implication of the $\rho\pi^{+}$ state, of which an experimental limit has been
given, is discussed. An upper bound in the 10 MeV range for the decay constant
$f_{\pi'}$ of the $\pi(1300)$ meson is obtained .
  Predictions are given for the $D_{s}^{+} \ra \pi^{0}\pi^{0}\pi^{+}$ rate as
well as for the $\pi^{+}$ and $\pi^{-}$ ($\pi^{0}$ and $\pi^{+}$) energy
distributions for these two decay modes $D_{s}^{+} \ra \pi^{+}\pi^{+}\pi^{-}$
($D_{s}^{+} \ra \pi^{0}\pi^{0}\pi^{+}$) respectively.


title: Differential Distributions for Heavy Flavour Production at HERA

abstract:
  We compute pseudorapidity and transverse momentum distributions for charm and
bottom production at HERA. We examine the effect of next-to-leading order QCD
corrections, the effect of possible intrinsic transverse momenta of the
incoming partons, and of fragmentation. We compare our results with full Monte
Carlo simulation using HERWIG. The importance of the hadronic component of the
photon is also studied. We examine the possibility to distinguish among
different parametrizations of the photon parton densities using charm
production data, and the possibilty to extract information about the small-$x$
behaviour of the gluon density of the proton. We also give a prediction for the
transverse momentum and pseudorapidity distributions for bottom production at
HERA.


title: HYPERON RADIATIVE DECAYS IN THE BOUND STATE SOLITON MODEL

abstract:
  The radiative decays of hyperons are studied in the framework of the bound
state soliton model. Detailed predictions for the total decay widths and the
E2/M1 ratios corresponding to decuplet--to--octet electromagnetic transitions
are presented in relation to future planned experiments at CEBAF and Fermilab.
The results are compared to those obtained in quark based models.


title: STERILE NEUTRINOS AS A SOLUTION TO ALL NEUTRINO ANOMALIES

abstract:
  The sterile neutrino solutions to different irregular results and
observations in neutrino physics are studied. It is pointed out that
introducing sterile neutrinos helps to solve simultaneously the observed
anomalies. It is argued that sterile neutrinos can solve the conflict between
dark matter neutrinos, LSND result and supernova nucleosynthesis. Other
supernova constraints for sterile neutrinos are revised. Possibilities to avoid
the big bang nucleosynthesis constraints for sterile neutrinos are explored. It
is claimed that sterile neutrinos can solve the crisis in big bang
nucleosynthesis. It is pointed out that sterile neutrinos can provide a
consistent explanation to the anomalies observed at Karmen. It is argued that
sterile neutrinos are valid dark matter candidates. It is claimed that the
conversions to sterile states are consistent solutions to both the solar and
the atmospheric neutrino problems, and cannot be ruled out by cosmological or
astrophysical arguments. Models for the masses and the interactions of sterile
neutrinos are reviewed.


title: The Pooltable Analogy to Axion Physics

abstract:
  An imaginary character named TSP finds himself in a playroom whose floor is
tilted to one side. However, the pooltable in the playroom is horizontal. TSP
wonders how this can be. In doing so, he embarks upon an intellectual journey
which parallels that which has been travelled during the past two decades by
physicists interested in the Strong $CP$ Problem and axion physics.


title: Prospects for spin physics at RHIC

abstract:
  The proposal to perform polarized proton-proton collisions at collider
energies at RHIC is reviewed. After a brief reminder of the desirability of
high energy spin physics measurements, we discuss the machine parameters and
detector features which are taken to define a program of spin physics at RHIC.
Some of the many physics processes which can provide information on polarized
parton distributions and the spin-dependence of QCD and the electroweak model
at RHIC energies are discussed. (To appear in the proceedings of the
International Symposium on Particle Theory and Phenomenology, Iowa State
University, May 22-24, 1995.)


title:
NEW CORRECTIONS OF ORDER $\alpha^3(Z\alpha)^4$ AND $\alpha^2(Z\alpha)^6$
  TO THE LAMB SHIFT

abstract:
  Two corrections to the Lamb shift, induced by the polarization operator
insertions in the external photon lines are calculated.


title:
Top Mass Analyses for the Reported Top-Antitop Production and Decay
  Events

abstract:
  We have analyzed the available data on $p\bar{p}\,\rightarrow\, t\, \bar{t}$
followed by the decays ($t\rightarrow bW^{+},\: \bar{t}\rightarrow
\bar{b}W^{-}$) which lead to $e^{\pm}\mu^{\mp}2 \mathrm{jets}$ or $l^{\pm}4
\mathrm{jets}$ configurations, using a likelihood method we proposed earlier.
The outcome is compared with the recent CDF analysis. In an appendix, we
discuss the nature of the additional ``slow'' $\mu^{+}$ observed in one CDF
dilepton event, concluding that it is most probably a ``tertiary lepton''
resulting from the decay sequence $b\rightarrow c +\mathrm{hadrons}$, followed
by $c\rightarrow s \mu^{+} \nu$.


title: Determination of alpha_s from F_2^p at HERA

abstract:
  We compute the proton structure function F_2^p at small x and large Q^2 at
next-to-leading order in alpha_s(Q^2), including summations of all leading and
subleading logarithms of Q^2 and 1/x in a way consistent with momentum
conservation. We perform a detailed comparison to the 1993 HERA data, and show
that they may be used to determine alpha_s(M_Z^2)=0.120 pm 0.005(exp) pm
0.009(th). The theoretical error is dominated by the renormalization and
factorization scheme ambiguities.


title: LARGE CORRELATIONS IN PARTICLE PRODUCTION AND SQUEEZING PHENOMENA

abstract:
  Recent developments in studies of multiparticle correlations in high energy
particle collisions are reviewed. Both experimental data and theoretical
results in quantum chromodynamics are discussed. Application of the developed
methods to the coherent, squeezed and correlated states of photons is
considered. Some speculations concerning possible coherent and squeezed states
of pion fields as well as their specific features are described.


title: Estimates of B-decays into K-Resonances and Dileptons

abstract:
  Short and long distance contributions to the exclusive B-decays into various
K-resonances and dileptons, i.e. B --> Ki l l ( l = e, mu , nu ), are examined.
The heavy quark effective theory has been used to calculate the hadronic matrix
elements. Substantial branching fractions are obtained for the dileptonic
B-decays into some higher excited states of K-mesons. The long distance
(resonance) contributions to these exclusive rare B-decay modes dominate the
short distance contributions mostly by two orders of magnitude. It is pointed
out that, excluding the resonance contributions, the P-wave channels are
dominant, accounting for about 50% of the inclusive B --> X_s l l branching
fraction.


title:
How to Measure Chromo-magnetic Vacuum Background Field in $e^{+}e^{-}\to
  jets$, Hadron-Hadron and Nucleus-Nucleus Collisions

abstract:
  We propose a new type of the measurement which is sensitive to the QCD vacuum
color-magnetic fluctuations: A measure of the axial assymetry of the hadronic
final states produced in the high energy $e^{+}e^{-}$ collisions is related to
the chromomagnetic vacuum field strength.


title: Calculation of Heat-Kernel Coefficients and Usage of Computer Algebra

abstract:
  The calculation of heat-kernel coefficients with the classical DeWitt
algorithm has been discussed. We present the explicit form of the coefficients
up to $h_5$ in the general case and up to $h_7^{min}$ for the minimal parts.
The results are compared with the expressions in other papers. A method to
optimize the usage of memory for working with large expressions on universal
computer algebra systems has been proposed.


title:
Photoproduction of the Eta-Prime Mesons as a New Tool to Probe Baryon
  Resonances

abstract:
  We examine eta prime photoproduction, as a novel tool to study baryon
resonances around 2 GeV, of particular interest to the quark shell model, which
predicts a number of them. We find important roles of the form factors at the
strong vertices, and show that the N^*(2080) can be probed efficiently by this
reaction.


title: Probing Trilinear Gauge Boson Couplings at Colliders

abstract:
  A direct measurement of the trilinear $WW\gamma$ and $WWZ$ couplings is
possible in the pair production of electroweak bosons at $e^+e^-$ and hadron
colliders. This talk addresses some of the theoretical issues: the
parameterization of ``anomalous couplings'' in terms of form factors and
effective Lagrangians, the complementary information which can be obtained in
$e^+e^-$ vs. hadron collider experiments, and a novel way to implement finite
$W$-width effects in a gauge invariant manner.


title:
Extraction of the Ratio of the Neutron to Proton Structure Functions
  from Deep Inelastic Scattering

abstract:
  We study the nuclear ($A$) dependence of the European Muon Collaboration
(EMC) effect at high values of $x$ ($x \geq 0.6$). Our approach makes use of
conventional nuclear degrees of freedom within the Relativistic Impulse
Approximation. By performing a non-relativistic series expansion we demonstrate
that relativistic corrections make a substantial contribution to the effect at
$x \gtrsim 0.6$ and show that the ratio of neutron to proton structure
functions extracted from a global fit to all nuclei is not inconsistent with
values obtained from the deuteron.


title:
Modification of the Equivalent Photon Approximation for Resolved Photon
  Processes

abstract:
  We propose a modification of the equivalent photon approximation (EPA) for
processes which involve the parton content of the photon, to take into account
the suppression of the photonic parton fluxes due to the virtuality of the
photon. We present simple, physically motivated ans\"atze to model this
suppression and show that even though the parton content of the electron no
longer factorizes into an electron flux function and a photon structure
function, it is still possible to express it as a single integral. We also show
that for the TRISTAN experiments its effect can be numerically of the same size
as that of the NLO corrections. Further, we discuss a possible measurement at
HERA, which can provide an experimental handle on the effect we model through
our ans\"atze.


title:
Calculation of Long-Distance Effects in Exclusive Weak Radiative Decays
  of B-Mesons

abstract:
  We calculate the contribution of the weak annihilation to the $B\rightarrow
\rho\gamma$ decay amplitude by means of QCD sum rules using the photon
light-cone wave function. We find that this long-distance contribution amounts
to about 10\% of the leading short-distance effect in $B^-\rightarrow
\rho^-\gamma$. On the other hand, weak annihilation is the dominant source of
the corresponding $D$ meson decays and according to our estimates, yields
branching ratios of $O(10^{-4})$ for $D^0\rightarrow \bar{K}^{*0}\gamma$,
$O(10^{-5})$ for $D_s\rightarrow \rho^+\gamma$, and $O(10^{-6})$ for
$D^-\rightarrow \rho^-\gamma$ and for $D^0\rightarrow \rho^0\gamma$.


title:
Probing flavor changing top-charm-scalar interactions in $e^+e^-$
  collisions

abstract:
  Due to the very large mass of the top-quark, probing the flavor changing
top-charm-scalar vertex is clearly very important. Fortunately the largeness of
$m_t$ endows a unique signature to the resulting reaction i.e., $e^+e^-\to
t\bar c (\bar t c)$ that should be helpful in identification of such events. A
two Higgs doublet model, without natural flavor conservation, is used to give
an illustrative estimate for the rate for these reactions.


title:
STATUS OF PERTURBATIVE QCD EVALUATION OF HADRONIC DECAY RATES OF THE Z
  AND HIGGS BOSONS

abstract:
  We review the current status of the high order perturbative QCD evaluation of
the hadronic decay rates of the Z and Higgs bosons. A systematic classification
of the various types of QCD corrections to $O(\alpha_s^2)$ and $O(\alpha_s^3)$
is made and their numerical status is clarified.


title: The triple pomeron interaction in the perturbative QCD

abstract:
  The triple pomeron interaction is studied in the perturbative approach of
BFKL-Bartels. At finite momentum transfers $\sqrt{-t}$ the contribution
factorizes in the standard manner with a triple-pomeron vertex proportional to
$1/\sqrt{-t}$. At $t=0$ the contribution is finite, although it grows faster
with energy than for finite $t$ and does not factorize.


title: SHOULD SPARTICLE MASSES UNIFY AT THE GUT SCALE?

abstract:
  Gauge and Yukawa (for the third family) coupling unification seem to be the
best predictions of the grand-unified theories (GUTs). In supersymmetric GUTs,
one also expects that the sparticle masses unify at the GUT scale (for
sparticles embedded in the same GUT multiplet). I show under what circumstances
GUTs do not lead to sparticle mass unification. In particular, I give examples
of SU(5) and SO(10) SUSY GUTs in which squarks and sleptons of a family have
different tree-level masses at the unification scale. The models have
interesting relations between Yukawa couplings.
  For example, I present an SO(10) GUT that allows for a large ratio of the top
to bottom Yukawas, accounting for the large $m_t /m_b$. The splittings can also
be induced in the Higgs soft masses and accommodate the electroweak breaking.


title:
Reason of Large Scale Difference of the Results in the Neutron-
  antineutron Oscillation Problem

abstract:
  We expose a grave drawback hidden in the standard model of
neutron-antineutron transitions in a medium. Correcting it, one improves a
limit on the free-space neutron-antineutron oscillation time by 31 orders of
magnitude.


title:
Estimates of the Weak Annihilation Contributions to the Decays $B \to
  \rho + \gamma$ and $B \to \omega + \gamma$

abstract:
  The dominant long-distance contributions to the exclusive radiative decays $B
\to \rho (\omega) + \gamma$ involve photon emission from the light quarks at
large distances, which cannot be treated perturbatively. We point out that this
emission can be described in a theoretically consistent way as the magnetic
excitation of quarks in the QCD vacuum and estimate the corresponding
parity-conserving and parity-violating amplitudes using the light-cone QCD sum
rule approach. These are then combined with the corresponding short-distance
contribution from the magnetic moment operator in the same approach, derived
earlier, to estimate the decay rates $\Gamma (B \to \rho(\omega) + \gamma)$.
The implications of this result for the determination of the
Cabibbo-Kobayashi-Maskawa (CKM) matrix elements in radiative $B$ decays are
worked out.


title: Effective Models of the Electroweak Phase Transition

abstract:
  The consecutive integration over the distinct mass scales ${\cal O}(T),{\cal
O}(gT)$ leads to a hierarchy of effective models for the electroweak phase
transition. Different techniques for the realisation of such strategy are
reviewed. Advantages and difficulties resulting from the use of reduced models
are discussed.


title: JET PHYSICS IN DEEPLY INELASTIC SCATTERING AT HERA

abstract:
  We give an overview of jet physics in deeply inelastic scattering at HERA.
The problem of jet definitions, the scale dependence of jet cross sections and
some applications are discussed. (Talk presented at the Workshop on Deeply
Inelastic Scattering and QCD, Paris, April 1995. To appear in the proceedings.)


title: Z Boson Observables in the MSSM

abstract:
  A combined analysis for Z boson observables and the quantity \Delta r within
the framework of the Minimal Supersymmetric Standard Model is presented.
Contributions from supersymmetric particles are discussed and upper and lower
bounds for the MSSM predictions are given.


title: TEST OF T AND CP VIOLATION IN LEPTONIC DECAY OF tau^+-

abstract:
  The $\tau^\pm$, highly polarized in the direction of the incident beam, can
be obtained from the $e^\pm$ collider with the polarized incident $e^-$ (and
preferably also the $e^+$) beam. This polarization vector $\longvec
w_i=(w_1+w_2)/(1+w_1w_2) \widehat e_z$ can be used to construct the $T$ odd
rotationally invariant product $(\longvec w_i\times\longvec p_\mu)$. $\longvec
w_\mu$, where $w_1$ and $w_2$ are longitudinal polarization vectors of $e^-$
and $e^+$ respectively; $\longvec p_\mu$ and $\longvec w_\mu$ are the momentum
and polarization of the muon in the decay $\tau^-\rarrow \mu^-+
\bar\nu_\mu+\nu_\tau$. T is violated by the existence of such a term. CP can be
tested by comparing it with a similar term in $\tau^+$ decay. If T violation in
such a decay is milliweak or stronger, one can find it using the proposed
polarized $\tau$-charm factory with luminosity of $1 \sim 3 \times
10^{33}/\cm^2/\sec$. One can test whether T (and CP) violation is due to the
charged Higgs boson exchange by doing a similar experiment for the $\mu^\pm$
decay.


title: Bottom quark production cross section at fixed-target $pp$ experiments

abstract:
  The cross section for bottom quark production at fixed-target energies is
calculated for a wide range of beam momenta. A detailed analysis is given for
the HERA-B experiment. We consider both the order $\alpha_s^3$ cross section
and the resummation of soft gluon corrections in all orders of QCD perturbation
theory. The inclusive transverse momentum and rapidity distributions, including
resummation, for bottom quark production at HERA-B are also presented.


title: Effects of the $U_A(1)$ Anomaly on $\eta \to 2 \gamma$ Decay

abstract:
  We study the $\eta \to 2 \gamma$ decay using an extended three-flavor
Nambu-Jona-Lasinio model that includes the 't~Hooft instanton induced
interaction. The $\eta$ meson mass and the $\eta \to 2 \gamma$ decay width are
reproduced simultaneously with a rather strong instanton induced interaction.
The calculated $\eta$ decay constant is $f_\eta = 2.23 f_\pi$ and it suggests
that the $\eta$ meson is no longer the Goldstone boson.


title:
The asymptotic behaviour of the $\pi^0$ $\gamma^\ast$ $\gamma^\ast$
  vertex

abstract:
  The Bjorken-Johnson-Low theorem applied to the $\gamma^\ast \to \gamma^\ast
\pi^0$ process provides us with a rather remarkable asymptotic behaviour for
the $\pi^0 \gamma^\ast \gamma^\ast$ vertex. We compare our result with previous
QCD- inspired estimates and argue that the predicted behaviour is quite
consistent with the present data on hadronic $J/\Psi$ decays and ensures the
matching of long- and short-distance radiative corrections to $\pi^+ \to e^+
\nu_e$.


title:
Electroweak Fermion-loop Contributions to the Muon Anomalous Magnetic
  Moment

abstract:
  The two-loop electroweak corrections to the anomalous magnetic moment of the
muon, generated by fermionic loops, are calculated. An interesting role of the
top quark in the anomaly cancellation is observed. New corrections, including
terms of order $G_\mu \alpha m_t^2$, are computed and a class of diagrams
previously thought to vanish are found to be important. The total fermionic
correction is $-(23\pm 3) \times 10^{-11}$ which decreases the electroweak
effects on $g-2$, predicted from one-loop calculations, by 12\%. We give an
updated theoretical prediction for $g-2$ of the muon.


title:
The decay $\rho^0 \to \pi^+ \pi^- \gamma$ and the chiral invariant
  interactions of vector mesons

abstract:
  Using the close relationship between the low--energy constants of chiral
perturbation theory and the chiral invariant interactions of the vector meson
resonances with the pseudoscalar mesons, we investigate the process $\rho^0 \ra
\pi^+ \pi^- \gamma$. Compared with the contribution from the pure
bremsstrahlung mechanism, we find an enhancement of the decay rate near the
endpoint of the photon energy spectrum. Such a particular shape of the
differential decay rate has indeed been observed experimentally and turns out
to be an important confirmation of the theoretical concept of chiral vector
meson dominance.


title: Invisible Events with Radiative Photons at LEP

abstract:
  A study of the radiative neutrino counting reaction $e^+ e^- \to \nu {\bar
\nu} \gamma$ at LEP1 and LEP2 energies is presented. An approximate expression
for the spectrum of the observed photon is derived within the framework of the
$p_t$-dependent structure function approach. This is compared with an exact
expression and found in agreement within the foreseen experimental accuracy.
This model describing single-photon radiation can be applied to the more
general case of initial-state single-photon emission accompanying invisible
final-state events. Higher-order QED corrections due to undetected
initial-state radiation are also included. The implementation in a Monte Carlo
event generator is briefly described.


title:
Multiple Hard Interactions in Gamma-Gamma and Gamma-P Physics at LEP and
  HERA

abstract:
  At $e^+e^-$ and $ep$ colliders, the large fluxes of almost on-shell photons
accompanying the lepton beams lead to the photoproduction of jets. As the
centre-of-mass energy is increased, regions of smaller $x$ in the parton
densities are explored and these are regions of high parton density. As a
result, the probability for more than one hard partonic scattering occurring in
a single $\gamma \gamma$ or $\gamma p$ collision can become significant. This
effect has been simulated using an eikonal prescription combined with the
HERWIG Monte Carlo program. The possible effects of multiple hard interactions
on event shapes and jet cross sections have been studied in this framework at a
range of energies relevant to HERA and LEPII. The results indicate that the
effects could be significant.


title: Uncertainties on the CP Phase $\bfalpha$ due to Penguin Diagrams

abstract:
  A major problem in the determination of the the CP angle $\alpha$, that
should be measured through modes of the type $B_d, \bar{B}_d \to \pi \pi ,
\cdots ,$ is the uncertainty coming from Penguin diagrams. We consider the
different ground state modes $\pi \pi$, $\pi \rho$, $\rho \rho$, and, assuming
the FSI phases to be negligible, we investigate the amount of uncertainty
coming from Penguins that can be parametrized by a dilution factor $D$ and an
angle shift $\Delta \alpha$. The parameter $D$ is either 1 or very close to 1
in all these modes, and it can be measured independently, up to a sign
ambiguity, by the $t$ dependence. Assuming factorization, we show that $\Delta
\alpha$ is much smaller for the modes $\rho \pi$ and $\rho \rho$ than for $\pi
\pi$, and we plot their allowed region as a function of $\alpha$ itself.
Moreover, we show that most of the modes contribute to the asymmetry with the
same sign, and define for their sum an effective $D_{eff}$ and an effective
$\Delta \alpha_{eff}$, an average of $\Delta \alpha$ for the different modes.
It turns out that $D_{eff}$ is of the order of 0.9, $\Delta \alpha_{eff}$ is
between 5 $\%$ and 10 $\%$ and, relative to $\pi \pi$, the statistical gain for
the sum is of about a factor 10. Finally, we compute the ratios $K\pi /\pi \pi
, \cdots$ that test the strength of the Penguins and depend on the CP angles,
as emphasized by Silva and Wolfenstein and by Deandrea et al.


title: Proton decay and realistic models of quark and lepton masses

abstract:
  It is shown that in realistic SUSY GUT models of quark and lepton masses both
the proton decay rate and branching ratios differ in general from those
predicted in the minimal $SU(5)$ supersymmetric model. The observation of
proton decay, and in particular the branching ratio $B[(p \rightarrow \pi^+
\overline{\nu})/(p \rightarrow K^+ \overline{\nu})]$, would thus allow decisive
tests of these fermion mass schemes. It is shown that the charged lepton decay
modes $p \rightarrow K^0 \mu^+, p \rightarrow K^0 e^+$ arising through gluino
dressing diagrams are significant and comparable to the neutrino modes in large
tan$\beta$ models. Moreover, it is found that in certain classes of models the
Higgsino-mediated proton decay amplitudes are proportional to a model-dependent
group-theoretical factor which in some cases can be quite small. The most
interesting such class consists of $SO(10)$ models in which the dominant
flavor-symmetric contribution to the up-quark mass matrix comes from an
effective operator of the form ${\bf 16}_i{\bf 16}_j {\bf 10}_H {\bf 45}_H$,
where $\langle {\bf 45}_H \rangle$ points approximately in the $I_{3R}$
direction. This class includes a recent model of quark and lepton masses
proposed by the authors.


title: Self-Maintained Coherent Oscillations in Dense Neutrino Gases

abstract:
  We present analytical solutions to the nonlinear equations describing the
behavior of a gas of neutrinos with two flavors. Self-maintained coherent
flavor oscillations are shown to occur when the gas density exceeds a critical
value determined by the neutrino masses and the mean neutrino energy in the
gas. Similar oscillations may have occurred in the early Universe.


title:
High Energy Hadron-Nucleus Cross Sections and Their Extrapolation to
  Cosmic Ray Energies

abstract:
  Old models of the scattering of composite systems based on the Glauber model
of multiple diffraction are applied to hadron-nucleus scattering. We obtain an
excellent fit with only two free parameters to the highest energy
hadron-nucleus data available. Because of the quality of the fit and the
simplicity of the model it is argued that it should continue to be reliable up
to the highest cosmic ray energies. Logarithmic extrapolations of proton-proton
and proton-antiproton data are used to calculate the proton-air cross sections
at very high energy. Finally, it is observed that if the exponential behavior
of the proton-antiproton diffraction peak continues into the few TeV energy
range it will violate partial wave unitarity. We propose a simple modification
that will guarantee unitarity throughout the cosmic ray energy region.


title: Radiative Decay $ B \to l \nu \gamma $ in the Light Cone QCD Approach

abstract:
  We calculate to the leading twist 2 accuracy the rate for the decay $ B_{u}
\rightarrow l \nu \gamma $ using the light cone QCD sume rules. We find $ Br(
B_{u} \rightarrow l \nu \gamma) \simeq 2 \cdot 10^{-6} $. The results are used
to test the applicability of the constituent quark model approximation to the
same process.The latter estimate is proportional to $ 1/m_{u}^{2} $, where $
m_{u} \simeq \bar{\Lambda}_{u} $ is the "constituent quark mass", indicating
that the process is of long distance type. We find that the two approaches
yield similar results for the rate with the choice $ m_{u} \simeq 430-480 \;MeV
$. This indicates that the constituent quark model may be used for estimates of
the radiative "annihilation" contribution to this and other radiative decays.
We point out that this decay may be useful for the measurement of $ |V_{ub}|$.


title: Quark Confinement in a Constituent Quark Model

abstract:
  On the level of an effective quark theory, we define confinement by the
absence of quark anti-quark thresholds in correlation functions. We then
propose a confining Nambu-Jona-Lasinio-type model. The confinement is
implemented in analogy to Anderson localization in condensed matter systems. We
study the model's phase structure as well as its behavior under extreme
conditions, i.e.\ high temperature and/or high density.


title: Search for Large Rapidity Gap Events in e^+ e^- Annihilation

abstract:
  We investigate the cross-section for the production of a low-mass
colour-singlet cluster in $e^+e^-$ annihilation with a large rapidity gap
between the colour-singlet cluster and the other jets. It is argued that such
events are the cross-channel analogue of large-rapidity-gap events in
deep-inelastic scattering, and therefore could in principle be used to
investigate the analytic continuation of the BFKL pomeron to the positive-$t$
kinematic regime, where one would expect the trajectory to pass through
glueball states. The cross section can be calculated in perturbative QCD, so
that the infrared scale arising from non-perturbative effects, which prevents
an exponential fall-off with rapidity gap in the case of deep-inelastic
scattering, is absent in $e^+ e^-$ annihilation. Correspondingly, the cross
section for such events decreases rapidly with increasing rapidity gap.


title:
On Continuous Ambiguities in Model-Independent Partial Wave Analysis.
  Part 1

abstract:
  A problem of amplitude reconstruction in terms of the given angular
distribution is considered. Solution of this problem is not unique. A class of
amplitudes, correspondent to one and the same angular distribution, forms a
region in projection onto a finite set of spherical harmonics. An explicit
parametrization of a boundary of the region is obtained. A shape of the region
of ambiguities is studied in particular example. A scheme of partial-wave
analysis, which describes all solutions in the limits of the region, is
proposed.


title:
On Continuous Ambiguities in Model-Independent Partial Wave Analysis.
  Part 2

abstract:
  A problem of density matrix determination in terms of the given angular
distribution of decay products is considered.


title: Hybrid Excitations of the QCD String with Quarks

abstract:
  The model for constituent glue is presented starting from the perturbation
theory in nonperturbative QCD vacuum. Green function is constructed for a
system containing qqbar pair and gluon propagating in the vacuum background
field, and Hamiltonian approach to the problem is formulated. The masses of
lowest qqbarg hybrids with light quarks are evaluated, and implication of
results for the spectroscopy of exotic states is discussed.


title: Suppression of Psi' and J/Psi in High-Energy Heavy-Ion Collisions

abstract:
  The experimental ratio of $\psi'$ to $J/\psi$ is approximately a constant in
$pA$ collisions, but decreases as the transverse energy increases in
nucleus-nucleus collisions. These peculiar features can be explained as arising
from approximately the same $c \bar c$-baryon absorption cross section for
$\psi'$ and $J/\psi$ but greater disruption probabilities for $\psi'$ than for
$J/\psi$ due to the interaction of the $c\bar c$ system with soft particles
produced in baryon-baryon collisions.


title: Coherence Effects in Neutrino Oscillations

abstract:
  We study the effect of coherent and incoherent broadening on neutrino
oscillations both in vacuum and in the presence of matter (the MSW effect). We
show under very general assumptions that it is not possible to distinguish
experimentally neutrinos produced in some region of space as wave packets from
those produced in the same region of space as plane waves with the same energy
distribution.


title: Automorphisms in Gauge Theories and the Definition of CP and P

abstract:
  We study the possibilities to define CP and parity in general gauge theories
by utilizing the intimate connection of these discrete symmetries with the
group of automorphisms of the gauge Lie algebra. Special emphasis is put on the
scalar gauge interactions and the CP invariance of the Yukawa couplings.


title: Flavor Symmetry Breaking in the 1/N Expansion

abstract:
  The breaking of flavor SU(3) symmetry in the axial couplings and magnetic
moments of baryons is analyzed in the $1/N_c$ expansion. A simple meson loop
graph which is known to be of order $\sqrt{m_s}$ and leading order in $1/N_c$
correctly predicts the pattern of symmetry breaking in the magnetic moments. It
is, however, not possible to use this graph to predict the magnitude of the
breaking. The situation with the axial couplings is less clear. In this case
the breakings are relatively small and do not appear to follow an obvious
pattern. Nevertheless there is a clear indication that, with symmetry breaking
taken into account, the F/D ratio (defined in the presence of SU(3) breaking)
is considerably less than the SU(6) value of 2/3. With sizeable uncertainty, we
find F/D \approx 0.44. The quantity 3F-D which is relevant for the analysis of
spin-dependent deep inelastic scattering is considerably smaller than the SU(6)
value of unity. The new value, 3F-D=0.27+-0.09, is consistent with vanishing
strange-quark spin in the nucleon.


title:
Baryons and Dark Matter from the Late Decay of a Supersymmetric
  Condensate

abstract:
  The possibility that both the baryon asymmetry and dark matter arise from the
late decay of a population of supersymmetric particles is considered. If the
decay takes place below the LSP freeze out temperature, a nonthermal
distribution of LSPs results. With conserved $R$ parity these relic LSPs
contribute to the dark matter density. A net asymmetry can exist in the
population of decaying particles if it arises from coherent production along a
supersymmetric flat direction. The asymmetry is transferred to baryons if the
condensate decays through the lowest order nonrenormalizable operators which
couple to $R$ odd combinations of standard model particles. This also ensures
at least one LSP per decay. The relic baryon and LSP number densities are then
roughly equal. The ratio of baryon to dark matter densities is then naturally
$\Omegab / \OmegaLSP \sim {\cal O}(\mb / \mLSP)$. The resulting upper limit on
the LSP mass is model dependent but in the range ${\cal O}(30-140)$ GeV. The
total relic density is related to the order at which the flat direction which
gives rise to the condensate is lifted. The observed density is obtained for a
direction which is lifted by a fourth order Planck scale suppressed operator in
the superpotential.


title:
Finite $N_c$ Results for $F/D$ Ratios of the Baryon Vertices and $I=J$
  Rule

abstract:
  We calculate the $F/D$ ratios of spin-nonflip baryon vertex for an arbitrary
number of color degrees of freedom $N_c$ both in the non-relativistic quark
model with the $SU(6)$ spin-flavor symmetry and in the chiral soliton model
with $SU(3)$ flavor symmetry. We find that the spin-nonflip $F/D$ ratio tends
to $-1$ in the limit of $N_c \to \infty$. We show that this leading value $F/D=
-1$ of spin-nonflip baryon vertex in the $1/N_c$ expansion corresponds to the
isoscalar dominance while the well known leading value $F/D=1/3$ of the
spin-flip vertex corresponds to the isovector dominance. We discuss origins of
the dominance of isovector in spin-flip and isoscalar in spin-nonflip baryon
vertices, referred to as the $I=J$ rule. \par In terms of the matrix elements
of the operator which transform as the generator $\lambda^8$ of the $SU(3)$
symmetry we derive the model independent isoscalar formula for baryon vertices
and apply this to the mass formula and the isoscalar part of the baryon
magnetic moments. The same Okubo-Gell-Mann mass relation and its refined
relation among the octet baryons as the one for the case $N_c=3$ is derived
model independently for arbitrary color degrees of freedom $N_c$. Contrary to
$\lambda^8$,


title: Effective Charges in Non-Abelian Gauge Theories

abstract:
  The question of the definition of effective charges for non-abelian gauge
theories is discussed, focusing in particular on both the pinch technique and
background field method approaches. It is argued that there does exist a unique
generalization of the QED concept of an effective charge to non-abelian
theories, and that this generalization is given by the pinch technique. The
discussion is set in the wider (and controversial) context of the definition of
gauge-independent Green function-like quantities in general in such theories.


title: Dominating constituent of the $\Theta$ meson

abstract:
  On the basis of the relation between values of the coupling constants
determined from data fit it is concluded that the dominating constituent of the
$\Theta$ meson is the glueball. The possibility that $\Theta$ meson decays into
two $\sigma(750)$ mesons is suggested.


title:
Particle Currents in a Space-Time dependent and CP-violating Higgs
  Background: a Field Theory Approach

abstract:
  Motivated by cosmological applications like electroweak baryogenesis, we
develop a field theoretic approach to the computation of particle currents on a
space-time dependent and CP-violating Higgs background. We consider the
Standard Model model with two Higgs doublets and CP violation in the scalar
sector, and compute both fermionic and Higgs currents by means of an expansion
in the background fields. We discuss the gauge dependence of the results and
the renormalization of the current operators, showing that in the limit of
local equilibrium, no extra renormalization conditions are needed in order to
specify the system completely.


title: On the non-perturbative part of the photon structure function

abstract:
  We discuss a dispersion relation in the photon mass and show how (in
principle) model-independent constraints on the parton distribution functions
of the photon, notably a momentum sumrule, can be obtained. We present two sets
of parametrizations, SaS~1 and~2, corresponding to two rather extreme
realizations of the non-perturbative part. Inclusive electron scattering off a
real photon is found to be insufficient to constrain the non-perturbative
components. The additional sensitivity provided by the photon virtuality is
outlined. Previous approaches to model the non-perturbative input distributions
are commented upon.


title:
The Proton Spin Puzzle and $\Lambda$ Polarization in Deep--Inelastic
  Scattering

abstract:
  We point out that measurements of longitudinal $\Lambda$ polarization in the
target fragmentation region of deep--inelastic $\nu \,N$ and $\mu \,N$ or $e \,
N$ scattering may test dynamical mechanisms invoked to explain the proton spin
puzzle. A previously-proposed model for polarized $\bar s s$ pairs in the
proton wave function reproduces successfully the negative $\Lambda$
polarization found in the WA59 $\bar \nu \, N$ experiment, and makes
predictions that could be tested in future $\mu \, N$ and $e \, N$ experiments.


title:
Exploratory study of shrinkage of the diffraction cone for the
  generalized BFKL pomeron

abstract:
  In color dipole gBFKL dynamics, we describe the emerging gBFKL phenomenology
of a subasymptotic energy dependence of the diffraction slope and discuss
possibilities of testing the gBFKL predictions in exclusive photo- and
electroproduction of vector mesons $V$ at HERA. A substantial shrinkage of the
diffraction cone $\gamma^{*}p\rightarrow Vp$ processes from the CERN/FNAL to
HERA range of energy $W$ is predicted. This subasymptotic shrinkage is faster
than expected from the small slope of pomeron's Regge trajectory
$\alpha_{\Pom}'$. We point out that the diffraction slope is a scaling function
of $(m_{V}^{2}+Q^{2})$, what relates production of different vector mesons.


title: Can hadrons survive the chiral phase transition ?

abstract:
  We study mesonic and baryonic correlation functions in the temporal
directions in the vicinity of the critical temperature $T\simeq T_c$ using the
instanton liquid model. In this model chiral symmetry restoration is driven by
the formation of instanton-antiinstanton molecules. Although we find the
signals for all hadronic poles to be drastically reduced, some hadronic states
seem to survive the phase transition, as loosely bound $U(N_f)\times U(N_f)$
chiral multiplets in the plasma phase. These states are the $0^+ - 0^-$ mesons
$(\pi,\sigma,\eta',\delta)$ and the $N(\frac{1}{2}^+) - N(\frac{1}{2}^-)$
baryons.


title: Successful Supersymmetric Inflation

abstract:
  We reconsider the problems of cosmological inflation in effective
supergravity theories. A singlet field in a hidden sector is demonstrated to
yield an acceptable inflationary potential, without fine tuning. In the
simplest such model, the requirement of generating the microwave background
anisotropy measured by COBE fixes the inflationary scale to be about $10^{14}$
GeV, implying a reheat temperature of order $10^{5}$ GeV. This is low enough to
solve the gravitino problem but high enough to allow baryogenesis after
inflation. Such consistency requires that the generation of gravitational waves
be negligible and that the spectrum of scalar density perturbations depart
significantly from scale-invariance, thus improving the fit to large-scale
structure in an universe dominated by cold dark matter. We also consider the
problems associated with gravitino production through inflaton decay and with
other weakly coupled fields such as the moduli encountered in (compactified)
string theories.


title:
Dynamics of Two Higgs Doublet CP Violation and Baryogenesis at the
  Electroweak Phase Transition

abstract:
  We quantitatively study the charge transport mechanism of electroweak
baryogenesis in a realistic two-Higgs-doublet model, comparing the
contributions from quarks and leptons reflecting from electroweak domain walls,
and comparing the exact profile of the CP-violating phase with a commonly used
ansatz. We note that the phenomenon of spontaneous CP violation at high
temperature can occur in this model, even when there is no CP violation at zero
temperature. We include all known effects which are likely to influence the
baryon production rate, including strong sphalerons, the nontrivial dispersion
relations of the quasiparticles in the plasma, and Debye screening of gauged
charges. We confirm the claim of Joyce, Prokopec and Turok that the reflection
of tau leptons from the wall gives the dominant effect. We conclude that this
mechanism is marginally strong enough to produce the observed baryon asymmetry
of the universe.


title: Diffusion and Debye Screening Near Expanding Domain Walls

abstract:
  We study the effect of Debye screening of hypercharge when a net fermion
number is reflected from a domain wall during a first order phase transition,
which may be relevant for electroweak baryogenesis. We give a simple method for
computing the effect of screening within the diffusion approximation, whose
results are compatible with those of a more elaborate treatment based on the
Boltzmann equation. Our formalism takes into account the differences in
mobility of different particle species. We believe it is conceptually simpler
than other accounts of screening that have appeared in this context. Somewhat
surprisingly, we find that Debye screening can actually {\it enhance}
electroweak baryogenesis by a modest factor ($\sim 2$).


title:
Exact and Approximate Radiation Amplitude Zeros --- Phenomenological
  Aspects

abstract:
  We review the phenomenological aspects of the exact and approximate Radiation
Amplitude Zeros (RAZ) and discuss the prospects of searches for these zeros at
current and future collider experiments.


title:
Final State Interactions and CP Violation in $K_L \to \pi^+ \pi^- e^+
  e^-$

abstract:
  Using chiral perturbation theory we calculate the imaginary parts of the $K_L
\rightarrow \pi^+ \pi^- e^+ e^-$ form factors that arise from $\pi \pi
\rightarrow \pi^+ \pi^-$ and $\pi \pi \rightarrow \pi^+ \pi^- \gamma^*$
rescattering. We discuss their influence on CP violating variables in $K_L
\rightarrow \pi^+ \pi^- e^+ e^-$.


title:
A Simplified Approach to Determine $\alpha$ and the Penguin Amplitude in
  $B_{d}\to \pi\pi$

abstract:
  The effect of inelastic final-state interactions (IFSI's) on the
determination of the weak phase $\alpha$ from the isospin triangles of
$B\rightarrow \pi\pi$ is qualitatively illustrated. Neglecting the electroweak
penguins and IFSI's and assuming the dominance of the top-quark loop in strong
penguin diagrams, we propose an experimentally accessible way to approximately
determine $\alpha$ and the penguin amplitude in $B_{d}\rightarrow \pi\pi$. This
approach relies on a simplified isospin consideration and the factorization
approximation, and its feasibility is irrelevant to the time-dependent
measurements of $B_d\rightarrow \pi\pi$.


title: Tau Polarization Asymmetry in $B\to X_s\tau^+\tau^-$

abstract:
  Rare $B$ decays provide an opportunity to probe for new physics beyond the
Standard Model. In this paper, we propose to measure the tau polarization in
the inclusive decay $B\to X_s\tau^+\tau^-$ and discuss how it can be used, in
conjunction with other observables, to completely determine the parameters of
the flavor-changing low-energy effective Hamiltonian. Both the Standard Model
and several new physics scenarios are examined. This process has a large enough
branching fraction, $\sim {\rm few}\times 10^{-7}$, such that sufficient
statistics will be provided by the B-Factories currently under construction.


title: Extended PCAC Relation

abstract:
  We explore a consistent way to extend the partially conserved axial vector
current (PCAC) relation and corresponding current algebra results. The paper
includes investigations of a chiral Ward-Takahashi identity, the explicit
chiral symmetry breaking by a finite current quark mass, the modifica- tion of
the PCAC relation and its consequences. Two explicit relations between the
nucleon axial vector form factor $g_A(q^2)$, pseudo-scalar form factor $
g_P(q^2)$ and the pion-nucleon coupling constant $g_{\pi NN}(q^2)$ is obtained.
One of the relation is confirmed, within the experimental error, by observation
in the $0<-q^2 <0.2$ $\mbox{GeV}^2$ region. The other one, which relates
$g_A(q^2)$ and $f_\pi(q^2) g_{\pi NN}(q^2)$ is studied by using known empirical
facts and dispersion relation. Thoeretical uncertainties are evaluated. Certain
inconsistencies, which is in favor of the introduction of diquark condensation,
is discovered. We briefly discuss how diquark condensation could provide an
answer to the question of where about of the quark numbers in a nucleon and a
nucleus, which is raised in explaining puzzles observed in the violation of
Gottfried sum rule and EMC effects.


title:
Fermion mass effects on ${\Gamma(Z\ra b\bar{b} + a~light~Higgs)}$ in a
  two-Higgs-doublet model

abstract:
  Large fermion mass effect on the Yukawa process $Z \ra b\bar{b}\ra b\bar{b} h
(A)$ in the entire range of the neutral Higgs boson masses is found. It is
particularly important for light Higgs bosons, which are still not excluded
experimentally in a general two-Higgs-doublet model.


title: Higgs effects in top quark pair production

abstract:
  Top quark production in $p\bar p$ and $e^+e^-$ collisions is enhanced by the
exchange of a Higgs boson. The enhancement factors are calculated in the
threshold region using the Greens function method.


title: Toy Models of Non-perturbative Asymptotic Freedom in $\phi^3_6$

abstract:
  We study idealizations of the full nonlinear Schwinger-Dyson equations for
the asymptotically free theory of $\phi^3$ in six dimensions in its meta-stable
vacuum. We begin with the cubic nonlinearity and go on to all-order
nonlinearities which contain instanton effects. We show how our toy models of
the cubic Schwinger-Dyson equations contain the usual diseases of perturbation
theory in the massless limit (e.g., factorially divergent $\beta-$functions,
singular Borel-transform kernels associated with infrared renormalons) and show
how these models yield specific mechanisms for removing such singularities when
there is a mass gap. In the all-order nonlinear equation we show how to recover
the usual renormalization-group-improved instanton effects and associated
factorial divergences.


title: Chiral Symmetry, Heavy Quark Symmetry and Bound States

abstract:
  I investigate the bound state problems of lowest-lying mesons and heavy
mesons. Chiral symmetry is essential when one consider lowest-lying mesons.
Heavy quark symmetry plays an central role in considering the semi-leptonic
form factors of heavy mesons. Various properties based on the symmetries are
revealed using Bethe-Salpeter equations.


title: Axion-photon Couplings in Invisible Axion Models

abstract:
  We reexamine the axion-photon couplings in various invisible axion models
motivated by the recent proposal of using optical interferometry at the ASST
facility in the SSCL to search for axion. We illustrate that the assignment of
$U(1)_{PQ}$ charges for the fermion fields plays an important role in
determining the couplings. Several simple non-minimal invisible axion models
with suppressed and enhanced axion-photon couplings are constructed,
respectively. We also discuss the implications of possible new experiments to
detect solar axions by conversion to $X$-rays in a static magnetic apparatus
tracking the sun.


title: Gauge Coupling Unification in General SUSY Models

abstract:
  We study the effects of additional fields on the unification of gauge
couplings in supersymmetric models. We find that the effects are quite
constrained by the requirement of SU(5) gauge invariance. In general, we find
that any extension of the MSSM will form complete SU(5) multiplets or spoil
gauge coupling unification.


title: Incompatibility of different customary kaon phase convention

abstract:
  The conventions that Wu and Yang assumed for the kaon phases in the context
of $CP$ symmetrical two-pion decay channels fix the relative kaon phase. This
fact, apparently not emphasized sufficiently in the past, has recently been
overlooked by Hayakawa and Sanda. In particular, Wu and Yang fix the relative
phase to a different value than the one resulting from the convention
$CP|K^{0}\rangle = |\overline{K^{0}}\rangle$. The difference between the two
values is made up of possible contributions from $CPT$- and direct
$CP$-violations during the decay of a kaon into a two-pion state of isospin
zero.


title: A diquark model for baryons containing one heavy quark

abstract:
  We present a phenomenological ansatz for coupling a heavy quark with two
light quarks to form a heavy baryon. The heavy quark is treated in the heavy
mass limit, and the light quark dynamics is approximated by propagating scalar
and axial vector 'diquarks'. The resulting effective lagrangian, which
incorporates heavy quark and chiral symmetry, describes interactions of heavy
baryons with Goldstone bosons in the low energy region. As an application, the
Isgur--Wise form factors are estimated.


title:
Baryon QCD sum rules in an external isovector-scalar field and baryon
  isospin mass splittings

abstract:
  Within the QCD sum-rule approach in an external field, we calculate the
baryon matrix element of isovector-scalar current, $H_{\rm B}=\langle
B|\overline{u}u- \overline{d}d|B\rangle/2M_{\rm B}$, for octet baryons, which
appears in the response of the correlator of baryon interpolating fields to a
constant isovector-scalar external field. The sum rules are obtained for a
general baryon interpolating field with an appropriate form for the
phenomenological ansatz of the spectral density.
  The key phenomenological input is the response of the quark condensates to
the external field. To first order in the quark mass difference $\delta
m=m_d-m_u$, the non-electromagnetic part of the baryon isospin mass splitting
is given by the product of $\delta m$ and $H_{\rm B}$. Therefore, QCD sum-rule
calculation of $H_{\rm B}$ leads to an estimate of the octet baryon isospin
mass splittings. The resulting values are comparable to the experimental
values; however, the sum-rule predictions for $H_{\rm B}$ are sensitive to the
values of the response of the quark condensates to the external source, which
are not well determined.


title: Creating Matter at the Electroweak Phase Transition

abstract:
  I summarize recent results (work done in collaboration with Kimmo Kainulainen
and Axel Vischer) in which we make quantitative predictions for the baryon
asymmetry of the universe in the charge transport mechanism of electroweak
baryogenesis. Making favorable assumptions about the unknown quantities
relevant to the problem, we find that the mechanism is marginally capable of
creating a baryon asymmetry as large as that observed. (Talk presented at Great
Lakes Cosmology Workshop, Case Western Reserve University, and at MRST `95,
University of Rochester, May 6-8, 1995.)


title: Fermion masses and mixing from an extra gauge symmetry

abstract:
  Assuming that a horizontal abelian (gauge) symmetry is at the origin of
texture zeros in the fermion mass matrices we show how realistic mass patterns
can be generated in the presence of scalar fields whose vacuum expectation
value breaks the extra $U(1)$ symmetry. In the simplest scenario with just one
pair of singlet fields and under the assumption of L-R symmetry one obtains
quark mass matrices {\it \`a la Fritzsch}. The $U(1)$ symmetry can be made
anomaly free by the Green-Schwarz mechanism in which case the canonical
unification of the gauge couplings emerges as its byproduct. The generation of
neutrino masses requires either two extra heavy scalar (Higgs) fields to
determine the texture structure of the righthanded neutrino mass matrix or the
latter will contain a hierarchy of scales.


title:
Multiple Gluon Effects in $q+\bar q\to t+\bar t + X$ at FNAL Energies:
  Semi-Analytical Results

abstract:
  We apply our Yennie-Frautschi-Suura exponentiated cross section formulas for
the parton processes $q + {^(} \bar q {^)}{^\prime} \ra q{^\prime}{^\prime} +
{^(} \bar q {^)}{^\prime}{^\prime}{^\prime} + n(G)$ to the process $q + \bar q
\ra t + \bar t + n(G)$ at FNAL energies, where G is a QCD gluon. We use
semi-analytical methods to compute the ratio $r_{exp}=\sigma_{exp}/\sigma_B$,
where $\sigma_{exp}$ is our soft gluon YFS exponentiated cross section and
$\sigma_B$ is the Born cross section. For $m_t= 0.176(0.199)$TeV, we get
$r_{exp}=1.65(1.48)$, respectively, for $q=u$ for example. These results are
not inconsistent with the recent observations by CDF and D0.


title: Resummed Predictions for the Structure Function F2 at Small x

abstract:
  We report the results of including resummed splitting functions in the QCD
evolution equations at small x, and discuss the predictions that follow for the
deep inelastic structure functions.
  *Contribution at XXX Rencontres de Moriond, Les Arcs, March 1995


title:
The Direct and Indirect Detection of Weakly Interacting Dark Matter
  Particles

abstract:
  An ever-increasing body of evidence suggests that weakly interacting massive
particles (WIMPs) constitute the bulk of the matter in the Universe.
Experimental data, dimensional analysis and Standard Model particle physics are
sufficient to evaluate and compare the performance of detectors searching for
such particles either directly (e.g.\ by their scattering in germanium
detectors), or indirectly (e.g.\ by observing their annihilation into neutrinos
in underground detectors). We conclude that the direct method is superior if
the WIMP interacts coherently and its mass is lower or comparable to the weak
boson mass. In all other cases, i.e.\ for relatively heavy WIMPs and for WIMPs
interacting incoherently, the indirect method will be competitive or superior,
but it is, of course, held hostage to the successful deployment of high energy
neutrino telescopes with effective area in the $\sim10^4$--$10^5$~m$^2$ range
and with appropriately low threshold. The rule of thumb is that a kilogram of
germanium is roughly equivalent to a $10^4$~m$^2$ neutrino telescope, although
the signal-to-noise is, at least theoretically, superior for the neutrino
detector. The energy resolution of the neutrino telescope may be exploited to
measure the WIMP mass and suppress the background. A kilometer-size detector
probes WIMP masses up to the TeV-range, beyond which they are excluded by
cosmological considerations.


title:
Flavor-Changing Neutral Current Constraints in Topcolor-Assisted
  Technicolor

abstract:
  It is argued that the topcolor models recently proposed by Hill [1] may face
significant constraints from flavor-changing neutral current processes (such as
$B-\bar{B}$ mixing) unless the mixing angles between down-type quarks are
small. The flavor-changing processes are mediated by scalar bound states which
are likely to be light as a result of the near critical dynamics of the
$b$-quark sector. The consequences of the latter on the bottom quark mass are
also briefly discussed.


title: Searching for $B_c$ mesons in the ATLAS experiment at LHC

abstract:
  We discuss the feasibility of the observation of the signal from $B_c$ mesons
in the ATLAS experiment of the LHC collider at a luminosity of ${\approx}\
10^{33}$cm$^{-2}$s$^{-1}$. In particular we address the decay mode
$B_c{\rightarrow}J/\psi \pi$ followed by the leptonic decay
$J/\psi{\rightarrow}\mu^+\mu^-$, which should permit an accurate measurement of
the $B_c$ mass. We performed a Monte Carlo study of the signal and background
concluding that a precision of $40$ MeV for the $B_c$ mass could be achieved
after one year of running.


title:
Prospects for the extraction of ${\mid}V_{cb}{\mid}$ from $B_c\ {\to}\
  J/\psi\ {\mu}^+\ {\nu}$ decays at LHC

abstract:
  We discuss the possibility of extracting ${\mid}V_{cb}{\mid}$ from the future
measurement at LHC of the $B_c\ {\rightarrow}\ J/\psi\ {\mu}^+\ {\nu}$ decay
rate followed by the leptonic decay $J/\psi\ {\rightarrow}\ \mu^+\mu^-$. We
examine in detail the influence of the measurement of the muons' momenta and
vertex reconstruction in the final uncertainty of ${\mid}V_{cb}{\mid}$, as well
as the required theoretical inputs at both the production and weak decay level,
and their reliability in this regard. We stress the relevance of a rigorous
description of the fragmentation contributions to inclusive production at large
transverse momentum of heavy quarkonia in $pp$ collisions.


title: Electric quadrupole moments of the decuplet baryons in the Skyrme model

abstract:
  The electric quadrupole moments of the decuplet baryons are calculated in the
bound state approach of the Skyrme model. In this approach, all the quadrupole
moments of the decuplets are found to be proportional to the third component of
the baryon isospin. Contrary to the SU(3) collective model, the kaonic
contribution is as important as the pionic one. The transitional quadrupole
moments of the hyperons are also predicted.


title:
Pion Observables in the Extended NJL Model with Vector and Axial-Vector
  Mesons

abstract:
  The momentum-space bosonization method of a Nambu and Jona-Lasinio type model
with vector and axial-vector mesons is applied to $\pi\pi$ scattering. Unlike
the case in earlier published papers, we obtain the $\pi\pi$ scattering
amplitude using the linear and nonlinear realizations of chiral symmetry and
fully taking into account the momentum dependence of meson vertices. We show
the full physical equivalence between these two approaches. The chiral
expansion procedure in this model is discussed in detail. Chiral expansions of
the quark mass, pion mass and constant $f_\pi$ are obtained. The low-energy
$\pi \pi $ phase shifts are compared to the available data. We also study the
scalar form factor of the pion.


title: On the Four--Photon Decay of the Neutral Pion

abstract:
  The dominant contribution to the $\pi^0 \to 4\gamma$ branching ratio, coming
from purely electromagnetic photon-splitting graph, is calculated. The result
$Br(\pi^0 \to 4\gamma) \simeq (2.6 \pm 0.1) \cdot 10^{-11}$ is about three
orders of magnitude below the present experimental limit.


title:
Model-independent analysis of $\bbox{B}$-$\bbox{\bar B}$ mixing and
  $\bbox{CP}$ violation in $\bbox{B}$ decays

abstract:
  We present a framework to analyze effects of new physics beyond the standard
model on $B$-$\bar B$ mixing and $CP$ violation in $B$ decays in a
model-independent manner. Assuming that tree level decay amplitudes are
dominated by the standard model ones, new physics contribution to the $B$-$\bar
B$ mixing can be extracted from several measurements at $B$ factories. Using
this framework, we show the present constraint on new physics contribution to
the $B$-$\bar B$ mixing, and illustrate constraints expected to be given by
future experiments at $B$ factories. We also point out a possibility that $CP$
asymmetries in $B\rightarrow\psi K_S$, $B\rightarrow\pi\pi$, and $B\rightarrow
DK$ modes look consistent with the standard model, even if a large new physics
contribution is present in the $B$-$\bar B$ mixing.


title:
A Predictive Superunification $SO(10)\times \Delta_{48}(SU(3))\times
  U(1)$ Model for Fermion Masses and Mixings

abstract:
  Based on a few basic assumptions, a predictive supersymmetric grand
unification $G_{U}=SO(10)\times \Delta_{48}(SU(3))\times U(1)$ model is
proposed. Thus, all the observed 45 chiral fermions with additional 3
right-handed neutrinos are unified into an irreducible triplet 16-dimensional
spinor representation of $G_{U}$. Electroweak symmetry breaking naturally
requires two Higgs doublets which belong to a single 10 representation of
$SO(10)$. The model provides an unified description for all the Yukawa and
gauge couplings. With a given structure of the physical vacuum, the fermion
masses and mixings are predicted in terms of two basic parameters.


title: Comments on long distance contribution to $K^+\to\pi^+\nu\bar{\nu}$

abstract:
  We study the long distance contribution to $K^+\to\pi^+\nu\bar{\nu$ by using
chiral perturbation theory. We find that the tree level $O(P^2)$ contribution
vanishes identically without assuming the large $N_c$ limit. The leading
contribution arises from the one-loop amplitude, which is $O(P^4)$ in the
chiral power counting. The branching ratio of the long distance contribution is
found to be of order $10^{-7}$ smaller compared with that of short distance one
and hence is completely negligible.


title: Infrared Behaviour of the Gluon Propagator: Confining or Confined?

abstract:
  The possible infrared behaviour of the gluon propagator is studied
analytically, using the Schwinger-Dyson equations, in both the axial and the
Landau gauge. The possibility of a gluon propagator less singular than
$1/k^{2}$ when $k^{2} \rightarrow 0$ is investigated and found to be
inconsistent, despite claims to the contrary, whereas an infrared enhanced one
is consistent. The implications for confinement are discussed.


title: Spacings of Quarkonium Levels with the Same Principal Quantum Number

abstract:
  The spacings between bound-state levels of the Schr\"odinger equation with
the same principal quantum number $N$ but orbital angular momenta $\ell$
differing by unity are found to be nearly equal for a wide range of power
potentials $V = \lambda r^\nu$, with $E_{N \ell} \approx F(\nu, N) - G(\nu,N)
\ell$. Semiclassical approximations are in accord with this behavior. The
result is applied to estimates of masses for quarkonium levels which have not
yet been observed, including the 2P $c \bar c$ states and the 1D $b \bar b$
states.


title: $B$ Physics: Theoretical Aspects

abstract:
  Some aspects of $B$ physics relevant for experiments in hadron colliders are
discussed. These include the determination of parameters of the CKM Matrix and
confirmation of its role in CP violation, studies of mixing of nonstrange and
strange $B$ mesons, lifetimes of hadrons containing $b$ quarks, the use of
``same-side'' tagging of neutral $B$ mesons via correlations with charged pions
through fragmentation or resonances, and the determination of CKM phases
through the study of decays of $B$ mesons to pairs of light hadrons.


title: Infrared Renormalons and Power Suppressed Effects in $e^+e^-$ Jet Events

abstract:
  We study the effect of infrared renormalons upon shape variables that are
commonly used to determine the strong coupling constant in $e^+e^-$
annihilation into hadronic jets. We consider the model of QCD in the limit of
large $n_f$. We find a wide variety of different behaviours of shape variables
with respect to power suppressed effects induced by infrared renormalons. In
particular, we find that oblateness is affected by $1/Q$ non--perturbative
effects even away from the two jet region, and the energy--energy correlation
is affected by $1/Q$ non--perturbative effects for all values of the angle. On
the contrary, variables like thrust, the $c$ parameter, the heavy jet mass, and
others, do not develop any $1/Q$ correction away from the two jet region at the
leading $n_f$ level. We argue that $1/Q$ corrections will eventually arise at
subleading $n_f$ level, but that they could maintain an extra $\as(Q)$
suppression. We conjecture therefore that the leading power correction to shape
variables will have in general the form $\alpha^n_{\rm S}(Q)/Q$, and it may
therefore be possible to classify shape variables according to the value of
$n$.


title: Sum rules for charmed baryon masses

abstract:
  The measured masses of the three charge states of the charmed $\Sigma_c$
baryon are found to be in disagreement with a sum rule based on the quark
model, but relying on no detailed assumptions about the form of the
interaction. This poses a significant problem for the charmed baryon sector of
the quark model. Other relations among charmed baryon masses are also
discussed.


title: Consequences of an Abelian Family Symmetry

abstract:
  The addition of an Abelian family symmetry to the Minimal Supersymmetric
Standard Model reproduces the observed hierarchies of quark and lepton masses
and quark mixing angles, only if it is anomalous. Green-Schwarz compensation of
its anomalies requires the electroweak mixing angle to be $\sin^2\theta_w=3/8$
at the string scale, without any assumed GUT structure, suggesting a
superstring origin for the standard model. The analysis is extended to neutrino
masses and the lepton mixing matrix.


title: Renormalization of Effective Hamiltonians

abstract:
  We introduce a way of implementing Wilson renormalization within the context
of the theory of effective Hamiltonians. Our renormalization scheme involves
manipulations at the level of the generalized $G$--matrix and is independent of
any specific kinematics. We show how to calculate the beta function within this
context and exhibit our method using simple scale--invariant quantum mechanical
systems.


title: Possible pre-LEP200 SUSY threshold signals

abstract:
  If $R$-parity is not conserved, the SUSY-threshold production process $e^+e^-
\to \chi_1^0\chi_1^0$ could be detectable with relatively low luminosity. Hence
an interesting mass range for the lightest SUSY particle $\chi_1^0$ could be
explored at the CERN LEP collider during its intermediate energy development,
even before the full LEP200 upgrade is completed. We present cross section
formulas and discuss event rates and detection for the three distinct decay
options: $\chi_1^0\to 2\, {\rm charged \; leptons}\, +\, {\rm neutrino}$,
$\chi_1^0\to {\rm lepton}\, +2\, {\rm quarks}$, and $\chi_1^0\to 3\, {\rm
quarks}$.


title: Precision Tests of Quantum Chromodynamics and the Standard Model

abstract:
  We discuss three topics relevant to testing the Standard Model to high
precision: commensurate scale relations, which relate observables to each other
in pertubation theory without renormalization scale or scheme ambiguity, the
relationship of compositeness to anomalous moments, and new methods for
measuring the anomalous magnetic and quadrupole moments of the W and Z.


title: Small Angle Bhabha Scattering for LEP

abstract:
  We present the results of our calculations to a one, two, and three loop
approximation of the e$^+$e$^-$$\rightarrow$e$^+$e$^-$ Bhabha scattering
cross-section at small angles. All terms contributing to the radiatively
corrected cross-section, within an accuracy of $\delta\sigma/ \sigma = 0.1 \%
$, are explicitely evaluated and presented in an analytic form. $O(\alpha)$ and
$O(\alpha^2)$ contributions are kept up to next-to-leading logarithmic
accuracy, and $O(\alpha^3)$ terms are taken into account to the leading
logarithmic approximation. We define an experimentally measurable cross-section
by integrating the calculated distributions over a given range of final-state
energies and angles. The cross-sections for exclusive channels as well as for
the totally integrated distributions are also given.


title: Fracture Functions

abstract:
  We present a new approach to semi-inclusive hard processes in QCD by means of
$\it Fracture\;Functions$, hybrids between structure and fragmentation
functions. We briefly motivate and describe it together with a list of possible
applications.


title: Smooth Hybrid Inflation

abstract:
  We propose a variant of hybrid inflation which is applicable in a wide class
of supersymmetric grand unified models. The observed temperature perturbations
of cosmic background radiation can be reproduced with natural values of the
parameters of the theory and a grand unification scale which is consistent with
the unification of the minimal supersymmetric standard model gauge couplings as
measured at LEP. The termination of inflation is smooth and does not produce
any topological defects. Finally, we present a specific supersymmetric model
where our smooth hybrid inflationary scenario is realized.


title:
Probing the HHH vertex in e+e-, e-gamma and gamma-gamma collisions for
  light and intermediate Higgs bosons

abstract:
  We have studied double Higgs production at future linear colliders while
paying special attention to the option of high-energy and high-luminosity
photon beams. The main purpose was to examine the feasibility of e+e-, e-gamma
and gamma-gamma colliders in order to probe the anomalous triple Higgs
coupling, which is crucial for understanding the Standard Model. We considered
mainly the cases of light and intermediate Higgs bosons. Double Higgs
production is almost background free, except in the MH=MZ mass range, which is
discussed separately. It is shown that for a light Higgs boson the HHH coupling
can be measured even at e+e- collider at 500 GeV. For a intermediate Higgs
boson a collider in the TeV region is suitable for such an investigation. We
have estimated the bounds on the anomalous HHH coupling, which can be
experimentally established using future linear colliders.


title:
Studying Anomalous $WW\gamma$ and $WWZ$ Couplings with Polarized
  $p\bar{p}$ Collisions

abstract:
  We calculate tree-level cross-sections for $W^{+}\gamma$ and $W^{+}W^{-}$
production in proton-antiproton collisions, with one $W$ decaying to leptons,
with anomalous electroweak triple-boson coupling parameters $\Delta\kappa$ and
$\lambda$. We compare the unpolarized cross-sections to those for a polarized
proton beam, to study how a polarized proton beam would improve experimental
tests of anomalous couplings.


title: New Bounds on R-parity Violating Couplings

abstract:
  We use information from rare nonleptonic decays of heavy-quark mesons to put
new bounds on the magnitudes of certain product combinations of baryon
nonconserving R-parity violating couplings in supersymmetric models. Product
combinations of lepton and baryon nonconserving R-parity violating couplings
are also considered in the light of existing bounds on nucleon decay. Contrary
to popular impression, a few such combinations are shown to remain essentially
unconstrained.


title:
TOPAZ0 2.0 - A Program for Computing De-Convoluted and Realistic
  Observables Around the $Z^0$ Peak

abstract:
  The program {\tt TOPAZ0} is designed for computing $Z^0$ parameters,
de-convoluted and QED-dressed cross sections and forward-backward asymmetries
of $e^+ e^-$ annihilation into fermion pairs and of Bhabha scattering around
the $Z^0$ peak, over both a completely inclusive experimental set-up and a
realistic one, i.e. with cuts on acollinearity, energy or invariant mass and
angular acceptance of the outgoing fermions. The new version, 2.0, offers the
possibility of imposing different experimental cuts on cross sections and
forward-backward asymmetries in a single run, and includes radiative
corrections whose effect can become relevant in view of the present and
foreseen experimental accuracy. Moreover, an additional option is included,
which allows an estimate of the theoretical uncertainty due to unknown
higher-order effects, both of electroweak and QCD origin. With respect to the
version 1.0, the code is available in the form of {\tt SUBROUTINE}, in order to
render more viable the use of the program for aims not planned by the {\tt
TOPAZ0} package itself.


title: Tensor interactions and $\tau$ decays

abstract:
  We study the effects of charged tensor weak currents on the
strangeness-changing decays of the $\tau$ lepton. First, we use the available
information on the $K^+_{e3}$ form factors to obtain BR$(\tau^- \rightarrow
K^-\pi^0 \nu_{\tau})\sim {\cal O}(10^{-4})$ when the $K\pi$ system is produced
in an antisymmetric tensor configuration. Then, we propose a mechanism for the
direct production of the $K_2^*(1430)$ in $\tau$ decays. Using the current
upper limit on this decay we set a bound on the symmetric tensor interactions.