title:
LEPTO 6.5 - A Monte Carlo Generator for Deep Inelastic Lepton-Nucleon
  Scattering

abstract:
  Physics and programming aspects are discussed for a Fortran 77 Monte Carlo
program to simulate complete events in deep inelastic lepton-nucleon
scattering. The parton level interaction is based on the standard model
electroweak cross sections, which are fully implemented in leading order for
any lepton of arbitrary polarization, and different parametrizations of parton
density functions can be used. First order QCD matrix elements for gluon
radiation and boson-gluon fusion are implemented and higher order QCD radiation
is treated using parton showers. Hadronization is performed using the Lund
string model, implemented in {\sc Jetset}/{\sc Pythia}. Rapidity gap events are
generated through a model based on soft colour interactions.


title:
MAJOR 1.5 - A Monte Carlo Generator for Heavy Majorana Neutrinos in $ep$
  Collisions

abstract:
  The Monte Carlo generator {\sc Major} 1.5 simulates the production and decay
of heavy Majorana neutrinos via lepton mixing or exchange of `light'
right-handed $W$-bosons in deep inelastic scattering, i.e. $e^{\pm} p
\rightarrow {N} X \rightarrow{e}^{\pm} W^{\mp} X$ or $\nu_e Z X$. Physics and
programming aspects are described in this manual.


title: Is There a Hot Electroweak Phase Transition at $m_H\gsim m_W$?

abstract:
  We provide non-perturbative evidence for the fact that there is no hot
electroweak phase transition at large Higgs masses, $m_H = 95$, 120 and 180
GeV. This means that the line of first order phase transitions separating the
symmetric and broken phases at small $m_H$ has an end point $m_{H,c}$. In the
minimal standard electroweak theory 70 GeV $<m_{H,c}<$ 95 GeV and most likely
$m_{H,c} \approx 80$ GeV. If the electroweak theory is weakly coupled and the
Higgs boson is found to be heavier than the critical value (which depends on
the theory in question), cosmological remnants from the electroweak epoch are
improbable.


title: The \Xi_Q - \Xi_Q' Mixing and Heavy Baryon Masses

abstract:
  We examine the $\Xi_Q - \Xi'_Q$ mixing and heavy baryon masses in the heavy
quark effective theory with the $\mq$ corrections. In the conventional baryon
assignment, we obtain the mixing angle $\cos^2 \theta = 0.87\pm 0.03$ in virtue
of the Gell-Mann-Okubo mass relation. On the other hand, if we adopt the new
baryon assignment given by Falk, the allowed region of the $\Sigma_c$ mass is
upper from 2372 MeV.


title: Phenomenological Introduction to Direct Dark Matter Detection

abstract:
  The dark matter of our galactic halo may be constituted by elementary
particles that interact weakly with ordinary matter (WIMPs). In spite of the
very low counting rates expected for these dark matter particles to scatter off
nuclei in a laboratory detector, such direct WIMP searches are possible and are
experimentally carried out at present. An introduction to the theoretical
ingredients entering the counting rates predictions, together with a short
discussion of the major theoretical uncertainties, is here presented.


title:
Relativistic Calculation of Structure Functions b_{1,2}(X) of the
  Deuteron

abstract:
  The structure functions b_{1,2}^D(X) of the deuteron are studied within
covariant approach. It is shown that usual nonrelativistic convolution model
result in incorrect behavior of this structure functions at small X and
violates the exact sum rules. Realistic calculations are carried out with the
Bethe-Salpeter amplitude of the deuteron and compared with the nonrelativistic
results.


title: Parametrization of Realistic Bethe-Salpeter Amplitude for the Deuteron

abstract:
  The parametrization of the realistic Bethe-Salpeter amplitude for the
deuteron is given. Eight components of the amplitude in the Euclidean space are
presented as an analytical fit to the numerical solution of the Bethe-Salpeter
equation in the ladder approximation. An applicability of the parametrization
to the observables of the deuteron is briefly discussed.


title: Non-Factorization in $(B, B_s) \to P(V) \psi$ Decays

abstract:
  Available experimental data on decay rate and polarization are used to
investigate non-factorization contribution to processes of the kind $B
\rightarrow K \psi$, and $B \rightarrow K^* \psi$ using five theoretical models
for the formfactors. Using the knowledge on non-factorization gained from $B$
decays we study the processes $B_s \rightarrow (\eta', \eta) \psi$, and $B_s
\rightarrow \phi \psi$ where experimental data are very limited.


title: Nuclear Effects on the Spin-Dependent Structure Functions

abstract:
  This paper has been withdrawn by the author due to the appearence of enlarged
version with one new author name more (hep-ph/0012293).


title: Quantitative Tests of Color Evaporation: Charmonium Production

abstract:
  The color evaporation model simply states that charmonium production is
described by the same dynamics as $D \bar D$ production, {\em i.e.}, by the
formation of a colored $c \bar c$ pair. Its color happens to be bleached by
soft final-state interactions. We show that the model gives a complete picture
of charmonium production including low-energy production by proton, photon and
antiproton beams, and high-energy production at the Tevatron and HERA. Our
analysis includes the first next-to-leading-order calculation in the color
evaporation model.


title:
Exact Event Rates of Lepton Flavor Violating Processes in Supersymmetric
  SU(5) Model

abstract:
  Event rates of various lepton flavor violating processes in the minimal
supersymmetric SU(5) model are calculated, using exact formulas which include
Yukawa vertices of lepton-slepton-Higgsino. We find subtlety in evaluating
event rates due to partial cancellation between diagrams. This cancellation
typically reduces the event rates significantly, and the size of the reduction
strongly depends on superparticle mass spectrum.


title: Probing the Parton Densities of Virtual Photons at ep Colliders

abstract:
  The feasibility of an experimental determination of the parton distributions
of virtual photons at high energy $ep$ colliders is studied in the context of
the DESY-HERA collider. Recently proposed parton densities of virtual photons
are utilized to evaluate the appropriate production processes and their
relevant kinematical regions. It is demonstrated that high $E_T$ jet production
with $E_T\,\simeq 5-7\, {\rm{GeV}}$ and $b\bar{b}$ production can probe the
parton distributions of virtual photons up to virtualities of a few
${\rm{GeV}}^2$. A useful leading order parametrization of our proposed photonic
parton densities, suitable for further studies of these issues, is presented.


title: Hard Diffraction From Quasi-Elastic Dipole Scattering

abstract:
  The contribution to diffraction dissociation of virtual photons due to
quasi-elastic scattering of the $q$-$\bar q$ component is calculated in the
framework of the QCD dipole picture. Both longitudinal and transverse
components of the cross-section are given. It is shown that, at fixed mass of
the diffractively produced system, quantum mechanical interference plays an
important r\^ ole. Phenomenological consequences are discussed.


title: RPA-Approach to the Excitations of the Nucleon, Part I: Theory

abstract:
  In this paper we develop a theoretical framework which allows us to study
excitations of the nucleon. Assuming an effective two-body interaction as a
model for low-energy QCD, we derive a relativistic TDHF equation for a
many-body system of quarks. To render the Dirac-sea contribution tothe mean
field finite, we introduce a symmetry conserving regularization scheme. In the
small amplitude limit we derive an RPA equation. The structure of the $ph$
interaction and modifications due to the regularization scheme are discussed.
We give a prescription to obtain a nucleon state with good angular momentum (J)
and isospin (T) quantum numbers on mean-field level. To study excitations, we
develop a tensor-RPA approach, which is an extension of the conventional RPA
techniques to systems with a nonscalar ground state. This allows us to
construct excited states with good (J/T) quantum numbers. We discuss a method
to reduce the overcomplete $ph$-space and compute the tensor-RPA interaction
matrix elements. Finally we extend our scheme to include ({3/2}^+,
{3/2})-states.


title: The Problem of Mass and Mass Generation

abstract:
  The mass problem in particle physics for other fields is discussed. While the
problem of the nuclear masses has been resolved within the QCD framework, 3
parameters of the ``Standard Model'' are related to the fermion sector. The
origin of the ferion masses remains unresolved. We discuss attempts to explain
the observed hierarchical features of the mass spectrum by a symmetry. relating
the mass eigenvalues to the flavor mixing angles.


title: Resonant Conversion of Massless Neutrinos in Supernovae

abstract:
  It has been noted for a long time that, in some circumstances, {\sl massless}
neutrinos may be {\sl mixed} in the leptonic charged current. Conventional
neutrino oscillation searches in vacuum are insensitive to this mixing. We
discuss the effects of resonant massless-neutrino conversions in the dense
medium of a supernova. In particular, we show how the detected $\bar\nu_e$
energy spectra from SN1987a and the supernova $r$-process nucleosynthesis may
be used to provide very stringent constraints on the mixing of {\sl massless}
neutrinos.


title:
Large multiplicity fluctuations and saturation effects in onium
  collisions

abstract:
  This paper studies two related questions in high energy onium-onium
scattering: the probability of producing an unusually large number of particles
in a collision, where it is found that the cross section for producing a
central multiplicity proportional to $k$ should decrease exponentially in
$\sqrt{k}$. Secondly, the nature of gluon (dipole) evolution when dipole
densities become so high that saturation effects due to dipole-dipole
interactions become important: measures of saturation are developed to help
understand when saturation becomes important, and further information is
obtained by exploiting changes of frame, which interchange unitarity and
saturation corrections.


title: Studying trilinear gauge couplings at LEP2 using optimal observables

abstract:
  We study the sensitivity of the processes `e+ e- -> lepton (l) neutrino (v)
quark (u) antiquark (d)' at LEP2 energies on the non-standard trilinear gauge
couplings (TGC), using the optimal observables method. All relevant leading
logarithmic corrections to the tree-order cross section, as well as
experimental resolution effects have been studied. Taking into account
correlations among the different TGC parameters we show that the limits on the
TGC can reach the level of 0.15~(1sd) at 161 GeV with 100 pb$^{-1}$, a
challenge for the first LEP2 phase. At higher energies this can be improved
drastically, reaching the level of 0.02~(1sd).


title:
Properties of the hard pomeron with a running coupling constant and the
  high-energy scattering

abstract:
  The equation for the hard pomeron with a running coupling introduced on the
basis of the bootstrap requirement is solved numerically. Two supercritical
pomerons are found with the intercept minus 1 of the leading one of the order
0.35-0.5 and that of the subleading one half as large. The contribution of
multipomeron exchanges is found to be essential only at extremely high energies
of the order of 100 TeV. Comparison of the cross-sections and structure
functions to the present experimental data seems to indicate that the
asymptotical regime has not yet been achieved.


title:
The problem of the spin of the proton and elastic neutrino-proton
  scattering

abstract:
  Talk presented by S.M. Bilenky at the Adriatico Research Conference on
"Trends in Collider Spin Physics", ICTP, Trieste, December 1995.


title: MSSM and Z width: implications on top quark and Higgs physics

abstract:
  We discuss the one-loop quantum corrections to the top quark width and to the
hadronic widths of the Higgs bosons of the MSSM, and emphasize the results
obtained in particular regions of the MSSM parameter space which have been
proposed to alleviate the anomalies observed in the decay modes of the $Z$ into
$b\bar{b}$ and $c\bar{c}$. We find that the corrections can be large and should
be visible through the measurement of the top quark production cross-sections
in future experiments at the Tevatron and at the LHC.


title: Binary Boosts

abstract:
  The relativistic motion of an isolated two--body system (bound or unbound) of
given lab energy $K^{0}$ in QED is separated into cms motion and relative
motion. The relative motion equation ${\cal K}_{L} \psi_{L} ({\bf r}_{L} ) =0$
contains the momentum eigenvalue ${\bf K}$ of the cms motion. It is greatly
simplified by a binary boost to the atomic rest frame, where $K^{0}$ and ${\bf
K}$ appear only in a Lorentz--invariant combination. This boost is not a
product of single--particle boosts, which are useful only for perturbative
interactions. CPT--invariance is demonstrated, and orthogonality relations are
derived.


title: Diquark Structure in Heavy Quark Baryons in a Geometric Model

abstract:
  Using a geometric model for the study of the structure of hadrons, we study
baryons having one, two and three heavy quarks. The study reveals diquark
structure in baryons with one and two heavy quarks but not with three heavy
identical quarks.


title: Gaugino Condensation in the Early Universe

abstract:
  We examine the process of formation of the gaugino condensation within a
Nambu-Jona-Lasinio type approach. We construct an effective Lagrangian
description for the gaugino condensation which include a Weyl compensator
superfield whose vacuum expectation value is related to the gaugino
condensation.


title: $O(\alpha^2 G_F m^2_t)$ Contributions to $H\to\gamma\gamma$

abstract:
  The rare decay $H\to \gamma\gamma$ is a promising detection channel for an
intermediate mass Higgs boson. We compute its two-loop $O(\alpha^2 G_F m_t^2)$
correction in the standard model and find that the relative correction to the
decay rate runs between $0.7%$ and $0.5%$ for $M_H=80-150$ GeV. The analogous
correction to the amplitude for $gg\to H$ is recovered as a special case. The
generalization of our result to other models is also briefly indicated.


title: Top Quark Production to ${\cal{O}}(\alpha_s^2)$

abstract:
  The cross-section for the production of $t\bar{t}$ pairs in
$e^+e^-$-annihilation via a virtual photon is determined up to order
$\alpha_s^2$. For the cm-energies of interest the effect of the top mass may
not be considered as a small parameter and the full mass dependence must be
included.


title: grc4f v1.1: a Four-fermion Event Generator for e+e- Collisions

abstract:
  grc4f is a Monte-Carlo package for generating e+e- to 4-fermion processes in
the standard model. All of the 76 LEP-2 allowed fermionic final state processes
evaluated at tree level are included in version 1.1. grc4f addresses event
simulation requirements at e+e- colliders such as LEP and up-coming linear
colliders. Most of the attractive aspects of grc4f come from its link to the
GRACE system: a Feynman diagram automatic computation system. The GRACE system
has been used to produce the computational code for all final states, giving a
higher level of confidence in the calculation correctness. Based on the
helicity amplitude calculation technique, all fermion masses can be kept finite
and helicity information can be propagated down to the final state particles.
The phase space integration of the matrix element gives the total and
differential cross sections, then unweighted events are Generated. Initial
state radiation (ISR) corrections are implemented in two ways, one is based on
the electron structure function formalism and the second uses the parton shower
algorithm called QEDPS. The latter can also be applied for final state
radiation (FSR) though the interference with the ISR is not yet taken into
account. Parton shower and hadronization of the final quarks are performed
through an interface to JETSET. Coulomb correction between two intermediate
W's, anomalous coupling as well as gluon contributions in the hadronic
processes are also included.


title:
Searches for Clean Anomalous Gauge Couplings effects at present and
  future $e^+e^-$ colliders

abstract:
  We consider the virtual effects of a general type of Anomalous (triple) Gauge
Couplings on various experimental observables in the process of
electron-positron annihilation into a final fermion-antifermion state. We show
that the use of a recently proposed "$Z$-peak subtracted" theoretical
description of the process allows to reduce substantially the number of
relevant parameters of the model, so that a calculation of observability limits
can be performed in a rather simple way. As an illustration of our approach, we
discuss the cases of future measurements at LEP2 and at a new 500 GeV linear
collider.


title:
Bloch-Nordsieck Summation and Partonic Distributions in Impact Parameter
  Space

abstract:
  A model for the parton distributions of hadrons in impact parameter space has
been constructed using soft gluon summation. This model incorporates the
salient features of distributions obtained from the intrinsic transverse
momentum behaviour of hadrons. Under the assumption that the intrinsic
behaviour is dominated by soft gluon emission stimulated by the scattering
process, the b-spectrum becomes softer and softer as the scattering energy
increases. In minijet models for the inclusive cross-sections, this will
counter the increase from $\sigma_{jet}$ .


title: Melting of the quark condenstate in the NJL model with meson loops

abstract:
  Temperature dependence of the quark condensate is studied in the
Nambu--Jona-Lasinio model with meson loops. Substantial differences are found
compared to the results with quark loops only.


title: A Top Quark Soliton and its Anomalous Chromomagnetic Moment

abstract:
  We show that under the assumption of dynamical symmetry breaking of electro
weak interactions by a top quark condensate, motivated by the Top Mode Standard
Model, the top quark in this effective theory can be considered then as chiral
color soliton (qualiton). This is realized in an effective four-fermion
interaction with chiral $SU(3)_c$ as well as $SU(2)_L\otimes U_Y(1)$ symmetry.
In the pure top sector the qualiton consists of a top valence quark and a Dirac
sea of top and anti-top quark coupled to a color octet of Goldstone pions. The
mass spectra, isoscalar quadratic radii and the anomalous chromomagnetic moment
due to a non-trivial color form factor are calculated with zero and finite
current top masses and effects at the Hadron Colliders are discussed. The
anomalous chromomagnetic moment turns out to have a value consistent with the
top production rates of the D0- and CDF-measurements.


title:
The 3-loop QCD calculation of the moments of deep inelastic structure
  functions

abstract:
  We present the analytic next-to-next-to-leading perturbative QCD corrections
in the leading twist approximation for the moments N=2,4,6,8 of the flavour
singlet deep inelastic structure functions F_2 and F_L. We calculate the
three-loop anomalous dimensions of the corresponding singlet operators and the
three-loop coefficient functions of the structure functions F_L and F_2. In
addition, we obtained the 10th moment for the non-singlet structure functions
in the same order of perturbative QCD. We perform an analysis of the obtained
results.


title:
Anomalous Chromomagnetic Moments of Quarks and Large Transverse Energy
  Jets

abstract:
  We consider the jet cross sections for gluons coupling to quarks with an
anomalous chromomagnetic moment. We then apply this to the deviation and bounds
from QCD found in the CDF and D0 Fermilab data, respectively, to find a range
of possible values for the anomalous moments. The quadratic and quartic terms
in the anomalous moments can fit to the rise of a deviation with transverse
energy. Since previous analyses have been done on the top quark total cross
section, here we assume the same moment on all quarks except the top and find
the range $|\kappa'| \equiv |\kappa/(2 m_q)| = 1.0\pm 0.3$ TeV$^{-1}$ for the
CDF data. Assuming the anomalous moment is present only on a charm or bottom
quark which is pair produced results in a range $|\kappa'_{b,c}| = 3.5 \pm 1.0
$ TeV$^{-1}$. The magnitudes here are compared with anomalous magnetic moments
that could account for $R_b$ and found to be in the same general range, as well
as not inconsistent with LEP and SLD bounds on $\Delta \Gamma_{\text{had}}$.


title: CP violating decays in leptogenesis scenarios

abstract:
  We compute the CP violation in the decays of heavy electroweak singlet
neutrinos, arising from both the one--loop vertex corrections and the wave
function mixing. We extend the computation to the supersymmetric version of the
model and discuss the implications for the generation of a lepton number
asymmetry by the out of equilibrium decay of the heavy (s)neutrinos in the
early Universe, to be reprocessed later in the observed baryon excess by
anomalous electroweak processes.


title:
The Dynamical Retardation Corrections to the Mass Spectrum of Heavy
  Quarkonia

abstract:
  A new version for the relativistic generalization of the wide class of static
quark--antiquark confining potentials is suggested. The comparison of this
approach with other ones, known in literature, is considered. With the use of
Logunov--Tavkhelidze quasipotential approach the first--order retardation
corrections to the heavy quarkonia mass spectrum are calculated. As expected,
these corrections turn out to be small for all low--lying heavy meson states.


title:
A comparative study on two characteristic parametrizations for high
  energy pp and \=pp total cross sections

abstract:
  Available high energy data for both pp and \=pp total cross sections ($ 5 \
GeV \ < \ \sqrt s \ < \ 1.8 \ TeV$) are described by means of two well-known
distinct parametrizations, characteristic of theoretical (``Regge-like"
expression) and experimental (``Froissart-Martin-like" expression) practices,
respectively. Both are compared from the statistical point of view. For the
whole set of present data, statistical analysis ($\chi^2/d.o.f.$) seems to
favour a ``Froissart-like" ((ln $s$)$^{\gamma \approx 2}$ ) rise of the total
cross section rather than a ``Regge-like" ($s^{\epsilon}$) one.


title: Species Doubling and Chiral Lagrangians

abstract:
  Coupling gauge fields to the chiral currents from an effective Lagrangian for
pseudoscalar mesons naturally gives rise to a species doubling phenomenon
similar to that seen with fermionic fields in lattice gauge theory.


title: A General Algorithm for Calculating Jet Cross Sections in NLO QCD

abstract:
  We present a new general algorithm for calculating arbitrary jet cross
sections in arbitrary scattering processes to next-to-leading accuracy in
perturbative QCD. The algorithm is based on the subtraction method. The key
ingredients are new factorization formulae, called dipole formulae, which
implement in a Lorentz covariant way both the usual soft and collinear
approximations, smoothly interpolating the two. The corresponding dipole phase
space obeys exact factorization, so that the dipole contributions to the cross
section can be exactly integrated analytically over the whole of phase space.
We obtain explicit analytic results for any jet observable in any scattering or
fragmentation process in lepton, lepton-hadron or hadron-hadron collisions. All
the analytical formulae necessary to construct a numerical program for
next-to-leading order QCD calculations are provided. The algorithm is
straightforwardly implementable in general purpose Monte Carlo programs.


title:
Isolated Prompt Photon Production in Hadronic Final States of $e^+e^-$
  Annihilation

abstract:
  We provide complete analytic expressions for the isolated prompt photon
production cross section in $e^+e^-$ annihilation reactions through one-loop
order in quantum chromodynamics (QCD) perturbation theory. Functional
dependences on the isolation cone size $\delta$ and isolation energy parameter
$\epsilon$ are derived. The energy dependence as well as the full angular
dependence of the cross section on $\theta_\gamma$ are displayed, where
$\theta_\gamma$ specifies the direction of the photon with respect to the
$e^+e^-$ collision axis. We point out that conventional perturbative QCD
factorization breaks down for isolated photon production in $e^+e^-$
annihilation reactions in a specific region of phase space. We discuss the
implications of this breakdown for the extraction of fragmentation functions
from $e^+e^-$ annihilation data and for computations of prompt photon
production in hadron-hadron reactions.


title: Stable Superstring Relics

abstract:
  We investigate the cosmological constraints on exotic stable matter states
which arise in realistic free fermionic superstring models. These states appear
in the superstring models due to a ``Wilson--line'' breaking of the unifying
non--Abelian gauge symmetry. In the models that we consider the unifying
$SO(10)$ gauge symmetry is broken at the string level to $SO(6)\times SO(4)$,
$SU(5)\times U(1)$ or $SU(3)\times SU(2)\times U(1)^2$. The exotic matter
states are classified according to the patterns of the $SO(10)$ symmetry
breaking. In $SO(6)\times SO(4)$ and $SU(5)\times U(1)$ type models one obtains
fractionally charged states with $Q_{\rm e.m.}=\pm1/2$. In $SU(3)\times
SU(2)\times U(1)^2$ type models one also obtains states with the regular
charges under the Standard Model gauge group but with ``fractional'' charges
under the $U(1)_{Z^\prime}$ symmetry. These states include down--like color
triplets and electroweak doublets, as well as states which are Standard Model
singlets. By analyzing the renormalizable and nonrenormalizable terms of the
superpotential in a specific superstring model, we show that these exotic
states can be stable. We investigate the cosmological constraints on the masses
and relic density of the exotic states. We propose that, while the abundance
and the masses of the fractionally charged states are highly constrained, the
Standard Model -- like states, and in particular the Standard Model singlet,
are good dark matter candidates.


title:
Determining the top-antitop and $ZZ$ Couplings of a Neutral Higgs Boson
  of Arbitrary CP Nature at the NLC

abstract:
  The optimal procedure for extracting the coefficients of different components
of a cross section which takes the form of unknown coefficients times functions
of known kinematical form is developed. When applied to $\epem\to t\anti
t+$Higgs production at $\rts=1\tev$ and integrated luminosity of $200\fbi$, we
find that the $t\anti t\to$Higgs CP-even and CP-odd couplings and, to a lesser
extent, the $ZZ\to$Higgs (CP-even) coupling can be extracted with reasonable
errors, assuming the Higgs sector parameter choices yield a significant
production rate. Indeed, the composition of a mixed-CP Higgs eigenstate can be
determined with sufficient accuracy that a SM-like CP-even Higgs boson can be
distinguished from a purely CP-odd Higgs boson at a high level of statistical
significance, and vice versa.


title:
Lattice Computations of Small-x Parton Distributions in a Model of
  Parton Densities in Very Large Nuclei

abstract:
  Using weak coupling methods McLerran and Venugopalan~\cite{LV1} expressed the
parton distributions in large nuclei as correlation functions of a two
dimensional Euclidean field theory. The theory has the dimensionful coupling
$g^2 \mu $, where $\mu^2\sim A^{1/3}$ is the valence quark color charge squared
per unit area. We use a lattice regularization to investigate these correlation
functions both analytically and numerically for the simplified case of $SU(2)$
gauge theory. In weak coupling ($g^2\mu L<< 5$), where $L$ is the transverse
size of the nucleus, the numerical results agree with the {\it analytic}
lattice weak coupling results. For $g^2\mu L>> 5$, no solutions exist at
O($a^4$) where $a$ is the lattice spacing. This suggests an ill-defined
infrared behavior for the two dimensional theory. A recent proposal of McLerran
et al.~\cite{Kovner} for an {\it analytic} solution of the classical problem is
discussed briefly.


title: A Non-perturbative Treatment of Heavy Quarks and Mesons

abstract:
  A formalism for studying heavy quarks in terms of model Dyson-Schwinger
equations is developed. The formalism is the natural extension of a technique
which has proved successful in a number of studies of light hadron physics. The
dressed heavy quark propagator, calculated to leading order in the inverse
quark mass, is incorporated in a treatment of mesons consisting of a heavy
quark and light antiquark via the ladder approximation Bethe-Salpeter equation.
In the limit of infinite heavy quark mass the model is found to respect the
spectrum degeneracies present in Heavy Quark Effective Theory. An exploratory
numerical analysis of a simple form of the model is carried out to assess its
viability for studying $D$ and $B$ mesons.


title: GUT's have the ability to defy sphalerons

abstract:
  We show that the baryon asymmetry produced by the out of equilibrium decay of
heavy $GUT$ scalars can be the baryon asymmetry that is observed today. No
restrictions need be imposed on the initial values of $B$, $L$ and $B-L$, nor
on the neutrino masses; no new symmetries need be gauged nor new fermions
introduced. We find two mechanisms that can bring this about for any $GUT$
gauge group. Two illustrative models are discussed that are robust, and need
just two (at most four) more $GUT$ scalar fields than the minimum model. The
additional scalar fields can also help in generating an adequately large value
of the CP violation parameter and in efficiently annihilating the monopoles.
Our work should firmly re-establish heavy $GUT$ scalars as probable progenitors
of today's baryon asymmetry.


title:
Photoproduction of Jets and Heavy Flavors at Future Polarized ep -
  Colliders

abstract:
  We study photoproduction of jets and heavy flavors in a polarized collider
mode of HERA and in polarized $ep$ collisions at $\sqrt{S}\approx 30$ GeV. We
examine the sensitivity of the cross sections and their asymmetries to the
proton's polarized gluon distribution and to the completely unknown parton
distributions of longitudinally polarized photons.


title: The BFKL Pomeron: Can it be Detected?

abstract: The BFKL pomeron is swamped by the soft pomeron, at least at t=0.


title: Analytic scaling solutions for cosmic domain walls

abstract:
  A relativistic generalisation of a well-known method for approximating the
dynamics of topological defects in condensed matter is constructed, and applied
to the evolution of domain walls in a cosmological context. It is shown that
there are self-similar ``scaling'' solutions, for which one can in principle
calculate many quantities of interest without recourse to numerical
simulations. Here, the area density in the scaling regime is calculated in
various backgrounds. Remarkably good agreement with numerical simulations is
obtained.


title: Probing SUSY in FCNC and CP Violating Phenomena

abstract:
  We analyze constraints on low-energy flavour-changing sfermion mass terms,
coming from FCNC and CP violating processes, in the model-independent framework
of the mass insertion method. We discuss the relevance of these constraints as
tests of supersymmetric extensions of the standard model; in particular, we
consider grand-unified models and models with non-universal soft breaking
terms.


title:
Probing CP Violation in $\gamma\gamma\to W^+W^-$ with Polarized Photon
  Beams

abstract:
  We demonstrate in a general framework that polarized photons by backscattered
laser beams of adjustable frequencies at a TeV linear $e^+e^-$ collider provide
us with a very efficient mechanism to probe CP violation in two-photon
collisions. CP violation in the process $\gamma\gamma\rightarrow W^+W^-$ is
investigated in detail with linearly polarized photon beams. There are two
useful CP-odd asymmetries that do not require detailed information on $W$ decay
products. The sensitivity to the CP-odd form factors are studied quantitatively
by assuming a perfect $e$-$\gamma$ conversion and the 20 fb$^{-1}$ $e^+e^-$
integrated luminosity at the $e^+e^-$ c.m. energies $\sqrt{s}=0.5$ and $1.0$
TeV. The sensitivity is so high that such experiments will allow us to probe
new CP violation effects beyond the limits from some specific models with
reasonable physics assumptions. We find that a counting experiment of $W^+W^-$
events in the two-photon mode with adjustable laser frequencies can have much
stronger sensitivity to the CP-odd $\gamma(\gamma) WW$ form factors than can a
$W^+W^-$ decay-correlation experiment with a perfect detector achieve in the
$e^+e^-$ mode.
  PACS number(s): 14.70.Bh, 14.70.Hp, 13.88.+e


title: Mixing Transformations in Quantum Field Theory and Neutrino Oscillations

abstract:
  Field mixing transformations are studied in quantum field theory and the
generator of the transformations is found to induce an SU(2) coherent structure
in the vacuum state, both for bosons and for fermions. The Fock space for mixed
fields is unitarily inequivalent to the Fock space of the unmixed fields in the
infinite volume limit. We study neutrino mixing and oscillations and find that
the oscillation amplitude is depressed by a factor which is momentum and mass
dependent. The usual formula is recovered in the relativistic limit.
Phenomenological features of the modified oscillation formula are discussed.
Finally, preliminary results of the Green's function formalism are presented.


title: On The Difficulty of Computing Higher-Twist Corrections

abstract:
  We discuss the evaluation of power corrections to hard scattering and decay
processes for which an operator product expansion is applicable. The Wilson
coefficient of the leading-twist operator is the difference of two perturbative
series, each of which has a renormalon ambiguity of the same order as the power
corrections themselves, but which cancel in the difference. We stress the
necessity of calculating this coefficient function to sufficiently high orders
in perturbation theory so as to make the uncertainty of the same order or
smaller than the relevant power corrections. We investigate in some simple
examples whether this can be achieved. Our conclusion is that in most of the
theoretical calculations which include power corrections, the uncertainties are
at least comparable to the power corrections themselves, and that it will be a
very difficult task to improve the situation.


title: On the dispersive two-photon K_L -> \mu^+ \mu^- amplitude

abstract:
  We present a full account of the two-loop electroweak, two-photon mediated
short-distance dispersive $K_L \to\mu^+\mu^-$ decay amplitude. QCD corrections
change the sign of this amplitude and reduce it by an order of magnitude. Thus,
the QCD-corrected two-loop amplitude represents only a small fraction (with the
central value of 5 %) of the one-loop weak short-distance contribution, and has
the same sign. In combination with a recent measurement, the standard-model
prediction of the short-distance amplitude, completed in this paper, provides a
constraint on the otherwise uncertain long-distance dispersive amplitude.


title: Seeking Supersymmetry at LEP

abstract:
  1. Scope and motivation
  2. Lightning review of CMSSM
  3. LEP 1 bounds and LEP 1.5 results
  4. LEP 2 futurology
  5. Bottomline


title: Heavy SUSY Higgs Bosons at $e^+e^-$ Linear Colliders

abstract:
  The production mechanisms and decay modes of the heavy neutral and charged
Higgs bosons in the Minimal Supersymmetric Standard Model are investigated at
future $e^+ e^-$ colliders in the TeV energy regime. We generate supersymmetric
particle spectra by requiring the MSSM Higgs potential to produce correct
radiative electroweak symmetry breaking, and we assume a common scalar mass
$m_0$, gaugino mass $m_{1/2}$ and trilinear coupling $A$, as well as gauge and
Yukawa coupling unification at the Grand Unification scale. Particular emphasis
is put on the low $\tb$ solution in this scenario where decays of the Higgs
bosons to Standard Model particles compete with decays to supersymmetric
charginos/neutralinos as well as sfermions. In the high $\tb$ case, the
supersymmetric spectrum is either too heavy or the supersymmetric decay modes
are suppressed, since the Higgs bosons decay almost exclusively into $b$ and
$\tau$ pairs. The main production mechanisms for the heavy Higgs particles are
the associated $AH$ production and $H^+H^-$ pair production with cross sections
of the order of a few fb.


title: QCD Corrections to the Top Decay Mode $t \ra \tilde{t} \chi^0$

abstract:
  In supersymmetric theories, the top quark can decay into its scalar partner
plus a neutralino, with an appreciable rate. We calculate the $O(\alpha_s)$ QCD
corrections to this decay mode in the minimal supersymmetric extension of the
Standard Model. These corrections can be either positive or negative and
increase logarithmically with the gluino mass. For gluino masses below 1 TeV,
they are at most of the order of ten percent and therefore, well under control.


title: Perturbative QCD approach and particle energy spectra

abstract:
  The Modified Leading Log Approximation of QCD and the local parton hadron
duality picture are shown to give a fully satisfactory description of data on
charged particle energy spectra in $e^+e^-$ annihilation. The analysis of data
in terms of moments points out the running of $\alpha_s$ both at very low $cms$
energy (${\cal O}$(3 GeV)) and at very low particle energy (${\cal O}$(200-500
MeV)). The study of the universal soft limit of energy spectra at low particle
energy is proposed as a test of QCD coherence. The extension of this approach
at identified particles' spectra is discussed.


title: Phenomenology of Heavy Meson Chiral Lagrangians

abstract:
  The approximate symmetries of Quantum ChromoDynamics in the infinite heavy
quark ($Q=c,b$) mass limit ($m_Q \to \infty$) and in the chiral limit for the
light quarks ($m_q \to 0,\;q=\,u,\,d,\,s$) can be used together to build up an
effective chiral lagrangian for heavy and light mesons describing strong
interactions among effective meson fields as well as their couplings to
electromagnetic and weak currents, including the relevant symmetry breaking
terms. The effective theory includes heavy ($Q \bar q$) mesons of both negative
and positive parity, light pseudoscalars, as well as light vector mesons. We
summarize the estimates for the parameters entering the effective lagrangian
and discuss in particular some phenomenologically important couplings, such as
$g_{B^* B \pi}$. The hyperfine splitting of heavy mesons is discussed in
detail. The effective lagrangian allows for the possibility to describe
consistently weak couplings of heavy ($B,\, D$) to light ($\pi,\, \rho, \,
K^*,\,$ etc.) mesons. The method has however its own limitations, due to the
requirement that the light meson momenta should be small, and we discuss how
such limitations can be circumvented through reasonable ansatz on the form
factors. Flavour conserving (e. g. $B^* \to B\, \gamma$) and flavour changing
(e. g. $B \to K^* \, \gamma$) radiative decays provide another field of
applications of effective lagrangians; they are discussed together with their
phenomenological implications. Finally we analyze effective lagrangians
describing heavy charmonium- like ($\bar Q Q$) mesons and their strong and
electromagnetic interactions. The role of approximate heavy quark symmetries
for this case and the phenomenological tests of these models are also
discussed.


title: The Number of Neutrinos and the Left-Right Symmetric Model

abstract:
  The meaning of $N_\nu$ in the Left-Right Symmetric Model (LRSM) is discussed.
In its original definition $N_\nu$ is the number of neutrinos or generations of
leptons, so, in the Standard Model its value is three. However the
determination of $N_\nu$ in experiments and in astrophysical observations is
subject to different theoretical interpretations. We present arguments that
gives $N_\nu$ as a parameter of the LRSM. Using an experimental value for the
rate $Gamma_{inv}/Gamma_{l\bar{l}}$ we calculate the bound $2.90\leq
N_{\nu_LR}\leq 3.04$ (90 % C. L.), where $N_{\nu_LR}$ is a function of the
left-right mixing angle $\phi$. This range is less restrictive than the one of
the standard model.


title: Isospin corrections to charmless semileptonic $B \to V$ transitions

abstract:
  We compute isospin corrections to the charmless semileptonic $B \rightarrow
V$ transitions arising from $\rho-\omega$ mixing and discuss its relevance in
the determination of $V_{ub}$.


title: CP Nonconservation in $p\bar p\to t\bar b X$ at the Tevatron

abstract:
  The reaction $p\bar p\to t\bar bX$ is found to be rather rich in exhibiting
several different types of CP asymmetries. The spin of the top quark plays an
important role. Asymmetries are related to form factors arising from radiative
corrections of the $tbW$ production vertex due to non-standard physics. As
illustrations, effects are studied in two Higgs Doublet Models and in
Supersymmetric Models; asymmetries up to a few percent may be possible.


title: Phase ordering dynamics of cosmological models

abstract:
  The ordering dynamics of the Higgs field is studied, using techniques
inspired by the study of phase ordering in condensed matter physics, as a first
step to understanding the evolution of cosmic structure through the formation
of topological defects in the early universe. The common feature of these
different physical processes is scaling. A fully analytical approximate scheme
-- the linear-gaussian approach -- is proposed to evaluate 1-point, 2-point,
etc.\ scaling functions for the ordering dynamics of the $O(n)$-symmetric
Higgs-field models.


title: Neutrinos and Electromagnetic Gauge Invariance

abstract:
  It is discussed a recently proposed connection among U(1)$_{\rm em}$
electromagnetic gauge invariance and the nature of the neutrino mass terms in
the framework of $\mbox {SU(3)}_C\otimes G_W \otimes {\mbox U(1)}_N$, $G_W$ =
SU(3)$_L$, extensions of the Standard Model. The impossibility of that
connection, also in the extended case $G_W $ = SU(4)$_L$, is demonstrated.


title: Three-gluon vertex in arbitrary gauge and dimension

abstract:
  One-loop off-shell contributions to the three-gluon vertex are calculated, in
arbitrary covariant gauge and in arbitrary space-time dimension, including
quark-loop contributions (with massless quarks). It is shown how one can get
the results for all on-shell limits of interest directly from the general
off-shell expression. The corresponding general expressions for the one-loop
ghost-gluon vertex are also obtained. They allow for a check of consistency
with the Ward--Slavnov--Taylor identity.


title:
Weak Decay Form Factors of Heavy Pseudoscalar Mesons within a
  Light-Front Constituent Quark Model

abstract:
  The transition form factors describing the semileptonic decays of heavy
pseudoscalar mesons are investigated within a relativistic constituent quark
model formulated on the light-front. For the first time, the form factors are
calculated in the whole accessible kinematical region, adopting meson wave
functions derived from various effective $q \bar{q}$ interactions able to
describe the meson mass spectra. It is shown that the decay rates of the $B \to
D \ell \nu_{\ell}$, $D \to K \ell \nu_{\ell}$ and $D \to \pi \ell \nu_{\ell}$
weak decays are mainly governed by the effects of the confinement scale,
whereas the $B \to \pi \ell \nu_{\ell}$ decay rate is sensitive to the
high-momentum components generated in the meson wave functions by the effective
one-gluon-exchange interaction. Our results are consistent with available
experimental data and predictions of lattice $QCD$ calculations and $QCD$ sum
rules.


title: New Supernova Constraints on Sterile Neutrino Production

abstract:
  We consider the possibility that a light sterile-neutrino species $\nu_S$ can
be produced by $\nu_e$ scattering during the cooling of a proto-neutron star.
If we parameterize the sterile neutrino production cross-section by a parameter
$A$ as $\sigma (\nu_e X\rightarrow \nu_S X) = A \sigma(\nu_e X\rightarrow \nu_e
X)$, where $X$ is an electron, neutron or proton, we show that $A$ is
constrained by limits to the conversion of $\nu_e$ to $\nu_S$ in the region
between the sterile-neutrino trapping region and the electron-neutrino trapping
region. This consideration excludes values of $A$ in the range between $10^{-4}
\la A \la 10^{-1}$.


title: Do About Half the Top Quarks at FNAL Come From Gluino Decays?

abstract:
  We argue that it is possible to make a consistent picture of FNAL data
including the production and decay of gluinos and squarks. The additional cross
section is several pb, about the size of that for Standard Model (SM) top quark
pair production. If the stop squark mass is small enough, about half of the top
quarks decay to stop squarks, and the loss of SM top quark pair production rate
is compensated by the supersymmetric processes. This behavior is consistent
with the reported top quark decay rates in various modes and other aspects of
the data, and suggests several other possible decay signatures. This picture
can be tested easily with more data, perhaps even with the data in hand, and
demonstrates the potential power of a hadron collider to determine
supersymmetric parameters. It also has implications for the top mass
measurement and the interpretation of the LEP $R_b$ excess.


title:
The Polarization Asymmetry and Triple Gauge Boson Couplings in $\gamma
  e$ Collisions at the NLC

abstract:
  We examine the capability of the NLC in the $\gamma e$ collider mode to probe
the CP-conserving $\gamma WW$ and $\gamma ZZ$ anomalous couplings through the
use of the polarization asymmetry. When combined with other measurements, very
strong constraints on both varieties of anomalous couplings can be obtained.
[To appear in {\it Physics and Technology of the Next Linear Collider}, eds.
D.\ Burke and M.\ Peskin, reports submitted to Snowmass 1996.]


title: Gauge Coupling Unification in Left-Right Symmetric Models

abstract:
  We explore possibilities of gauge coupling unification in left--right
symmetric models with non--minimal particle content. In addition to unification
we require the absence of anomalies and sufficient proton lifetime. Numerous
previously unknown solutions are presented where unification occurs within the
latest experimental errors. Solutions exist where the scale of left--right
symmetry breaking can be as low as ${\cal O}(TeV)$ or the scale $M_R$ as high
as the Planck scale.


title: Physics of heavy neutrinos

abstract:
  Theoretical and experimental situation in physics of heavy neutrinos
$(M_N>M_Z)$ is briefly presented. Various experimental bounds on heavy neutrino
masses and mixings are shortly reviewed. Special attention is paid to
possibility of detecting heavy neutrinos in future lepton linear colliders.


title: Neutrino Masses and Family Symmetries

abstract:
  The hypothesis of an additional abelian symmetry acting in a different way on
the three families of leptons leads to interesting predictions in the neutrino
sector. Contrary to what happens in most seesaw models, the structures of the
Dirac and the Majorana matrices are determined without any ansatz, and the
neutrino masses and mixing angles are fixed once the lepton charges under the
family symmetry have been chosen. Two explicit models using this idea are
presented.


title:
Azimuthal Distribution of Quark-Antiquark Jets in DIS Diffractive
  Dissociation

abstract:
  We investigate the azimuthal distribution of quark-antiquark jets in DIS
diffractive dissociation with large transverse momentum. In this kinematical
region the matrix element is expressed in terms of the gluon structure
function. For the transverse part of the cross section we find a $\cos(2
\phi)$-distribution with the maximum at $\phi = \pm \pi/2$, i.e.\ the jets
prefer a direction perpendicular to the electron plane. This is in contrast to
boson gluon fusion where the $q\bar{q}$ jet cross section for transversely
polarized bosons peaks at $\phi=0$ and $\phi=\pi$. We discuss the origin of
this striking difference and present numerical results relevant for the
diffractive dissociation at HERA.


title: Gluon Regge Trajectory in the two-loop Approximation

abstract:
  Evaluating two-loop integrals in the transverse momentum space we obtain the
trajectory of the Reggeized gluon in QCD in an explicit form in the two-loop
approximation. It is presented as an expansion in powers of $(D-4)$ for the
space-time dimension $D$ tending to the physical value $D=4$. As the result of
a remarkable cancellation the third order pole in$D-4$ disappears in the
trajectory and the expansion starts with $(D-4)^{-2}$.


title: Heavy-quark correlations in deep inelastic scattering

abstract:
  We discuss results for heavy quark correlations in next-to-leading order QCD
in deep inelastic electroproduction.


title: Leptophobic $Z'$ in stringy flipped SU(5)

abstract:
  We show that leptophobic $Z'$ gauge bosons occur naturally in flipped SU(5)
and may shift $R_b$ in an interesting way without upsetting the good values of
$\Gamma_{had}$ and $R_c$. Within a string-derived version of the model, we
study three possible scenarios and the constraints imposed on model building
that would allow the new symmetry to remain unbroken down to low energies. Such
$Z'$ gauge boson has generation non-universal couplings to quarks that violate
parity maximally in the up-quark sector, and may contribute significantly to
spin asymmetries in polarized $pp$ scattering experiments now being prepared
for RHIC.


title: Beyond Intermittency: Erraticity

abstract:
  Erraticity analysis of multiparticle production data is introduced as a way
of extracting the maximum amount of information on self-similar fluctuations.
It is presented as the next logical step to take beyond the intermittency
analysis. An erraticity spectrum $e(\alpha)$ can be determined analogous to the
multifractal spectrum $f(\alpha)$. An analytical example is presented to
elucidate the method of analysis and the type of results that can be obtained.


title:
Anomalous Chromoelectric and Chromomagnetic Moments of the Top Quark at
  the NLC

abstract:
  The production of top quark pairs in association with a hard gluon in
$e^+e^-$ collisions at the NLC provides an opportunity to probe for anomalous
$t\bar tg$ couplings, \eg, the chromoelectric and chromomagnetic moments of the
top. We demonstrate that an examination of the energy spectrum of the
additional gluon jet can yield strong constraints on the size of these two
anomalous couplings. The results are shown to be quite sensitive to the cut on
the minimum gluon jet energy needed to remove events where the final state
$b$-quark radiates strongly. The possibility of using additional observables to
improve the sensitivity to anomalous couplings is briefly discussed. [To appear
in {\it Physics and Technology of the Next Linear Collider}, eds. D.\ Burke and
M.\ Peskin, reports submitted to Snowmass 1996.]


title:
Cancellation of Infrared Divergences in Hadronic Annihilation Decays of
  Heavy Quarkonia

abstract:
  In the framework of a newly developed factorization formalism which is based
on NRQCD, explicit cancellations are shown for the infrared divergences that
appeared in the previously calculated hadronic annihilation decay rates of
P-wave and D-wave heavy quarkonia. We extend them to a more general case that
to leading order in $v^2$ and next-to-leading order in $\alpha_s$, the infrared
divergences in the annihilation amplitudes of color-singlet
$Q\bar{Q}(^{2S+1}L_J)$ pair can be removed by including the contributions of
color-octet operators $Q\bar{Q}(^{2S+1}(L-1)_{J'})$,
$Q\bar{Q}(^{2S+1}(L-3)_{J''})$, ... in NRQCD. We also give the decay widths of
$^3D_J\rightarrow LH$ at leading order in $\alpha_s$.


title:
Note on restoring manifest rotational symmetry in hyperfine and fine
  structure in light-front QED

abstract:
  We study the part of the renormalized, cutoff QED light-front Hamiltonian
that does not change particle number. The Hamiltonian contains interactions
that must be treated in second-order bound state perturbation theory to obtain
hyperfine structure. We show that a simple unitary transformation leads
directly to the familiar Breit-Fermi spin-spin and tensor interactions, which
can be treated in degenerate first-order bound-state perturbation theory, thus
simplifying analytic light-front QED calculations. To the order in momenta we
need to consider, this transformation is equivalent to a Melosh rotation. We
also study how the similarity transformation affects spin-orbit interactions.


title: Tadpole Method and Supersymmetric O(N) Sigma Model

abstract:
  We examine the phase structures of the supersymmetric O(N) sigma model in two
and three dimensions by using the tadpole method. Using this simple method, the
calculation is largely simplified and the characteristics of this theory become
clear. We also examine the problem of the fictitious negative energy state.


title:
Unitarity Constraints on the B and B^* Form Factors from QCD Analyticity
  and Heavy Meson Spin Symmetry

abstract:
  A method of deriving bounds on the weak meson form factors, based on
perturbative QCD, analyticity and unitarity, is generalized in order to fully
exploit heavy quark spin symmetry in the ground state $(L=0)$ doublet of
pseudoscalar $(B)$ and vector $(B^*)$ mesons. All the relevant form factors of
these mesons are taken into account in the unitarity sum. They are treated as
independent functions along the timelike axis, being related by spin symmetry
only near the zero recoil point. Heavy quark vacuum polarisation up to three
loops in perturbative QCD and the experimental cross sections $\sigma(e^+e^-
\rightarrow \Upsilon)$ are used as input. We obtain bounds on the charge radius
of the elastic form factor of the $B$ meson, which considerably improve
previous results derived in the same framework.


title:
Study on $\nu_{\mu}$, $\nu_{\tau}$ Decays and CP-Non Invariance at Early
  Epoch of the Universe

abstract:
  We study the $\nu_{\mu}$ and $\nu_{\tau}$ decays in the early epoch of the
universe. If $m_{\nu_{\tau}}>2m_e$, there would be a CP asymmetry between
$\nu_{\tau}\rightarrow e^++e^-+\nu_e$ and $\bar{\nu}_{\tau} \rightarrow
e^++e^-+\bar{\nu}_e$. The resultant CP non-invariance is a function of
temperature and density and can reach $10^{-7}$ for a reasonable temperature
range, but it is noticed that if $m_{\nu_{\tau}}>2m_{\mu}\sim 200$ MeV, the CP
non-invariance can be much larger.


title:
Next-to-next-to-leading order QCD analysis of the CCFR data for xF_3 and
  F_2 structure functions of the deep-inelastic neutrino-nucleon scattering

abstract:
  The next-to-next-to-leading order (NNLO) non-singlet QCD analysis of the
experimental data of the CCFR collaboration for the $xF_3$ and $F_2$ structure
functions of the deep-inelastic scattering of neutrinos and antineutrinos on
the nucleon by means of the Jacobi polinomial expansion method is made. The
target mass corrections are also taken into account. We demonstrate that the
NNLO corrections have the important: they are decreasing the difference between
the values of $\alpha_s(M_Z)$, extracted from the NLO fit of $xF_3$ data and
from the NLO non-singlet fit of the combined $xF_3$ and $F_2$ CCFR data. The
obtained NNLO results for $\alpha_s(M_Z)$ are :$\alpha_s(M_Z)=0.109 \pm
0.003(stat) \pm 0.005(syst) \pm 0.003 (theor)$ (from $xF_3$ data) and
$\alpha_s(M_Z)=0.111\pm 0.002 (stat) \pm 0.003 (syst) \pm 0.003 (theor)$ (from
the combined $xF_3$ and $F_2$ data). We also estimate the values of the order
$O(\alpha_s^2)$-corrections to the Gottfried sum rule.


title: On axion-mediated macroscopic forces again

abstract:
  In a supersymmetric unified theory or in a generic model where a large
neutron electric dipole moment $d_N$ is expected, close to the present bound,
we estimate the relation g_aNN = 10^{-21\pm1}(d_N/10^{-25} e cm)(10^10 GeV/f_a)
between d_N itself, the scalar coupling g_{aNN} to nucleons of the axion,
assumed to exist, and the breaking scale, f_a, of the Peccei-Quinn symmetry.
Newly developing techniques to search for sub-cm macroscopic forces might
reveal a signal due to axion exchange at least in a favorable range of f_a.


title: Soft Gluon Radiation in Top Events: Effect of Hadronic $W$ Decays

abstract:
  In reconstructing the top quark momentum from its decay products, one must
account for extra jets that can result from radiation of gluons. In this paper
we study soft gluon radiation in top production and decay at the Fermilab
Tevatron. We consider the cases where one or both $W$ bosons decays
hadronically, {\it i.e.}, where at least one of the top quarks can be fully
reconstructed. We show results for gluon distributions at the Tevatron and find
that radiation from the $W$ decay products contributes substantially in the
central region.


title:
Probing Weak Anomalous Top Quark Couplings with Final State Gluons at
  the NLC

abstract:
  The rate and corresponding gluon jet energy distribution for the process
$e^+e^- \to t\bar tg$ are sensitive to the presence of anomalous dipole-like
couplings of the top to the photon and $Z$ at the production vertex. For
sizeable anomalous couplings of this type substantial deviations from the
expectations of the Standard Model are likely. We explore the capability of the
NLC to discover or place bounds on these types of top quark couplings. The
resulting constraints are found to be quite complementary to those which arise
from direct probes of the top quark production vertex. [To appear in {\it
Physics and Technology of the Next Linear Collider}, eds. D.\ Burke and M.\
Peskin, reports submitted to Snowmass 1996.]


title: Large N Expansion and Softly Broken Supersymmetry

abstract:
  We examine the supersymmetric non-linear O(N) sigma model with a soft
breaking term. In two dimensions, we found that the mass difference between
supersymmetric partner fields vanishes accidentally. In three dimensions, the
mass difference is observed but O(N) symmetry is always broken also in the
strong coupling region.


title:
Boundary Conditions and Correlations in Path Integrals for Quantum Field
  Theory of Thermal and Non-Equilibrium States

abstract:
  For thermal equilibrium systems it is shown, how the Kubo-Martin-Schwinger
boundary condition may be used to factorize the generating functional of Green
functions at least on the level of the full two-point function. Genuine
non-equilibrium system exhibit correlations that one may also incorporate in
the path integral. One one hand this provides a natural tool for a perturbative
expansion including these correlations. On the other hand it allows to prove
that in general non-equilibrium systems the generating functional does not
factorize.


title: Universal Spacing for Heavy Quarkonium Dissociation

abstract:
  When a heavy quark and the corresponding antiquark are separated by more than
$1.4 - 1.5$ fm, it becomes energetically favorable for a light quark-antiquark
pair to be produced, leading to fragmentation into a pair of flavored mesons.
The relation of this critical quark separation to other dimensional constants
of the strong interactions (such as the pion decay constant, the QCD scale, and
the light-quark constituent mass) is discussed.


title: Physics Cahiers No. 1

abstract:
  We begin herewith the editing of physics notes taken in the course of Journal
Club seminars at INFN-LNF in 1996. The activity consists of informal talks
about work in progress and/or review of (more or less) recent physics results
of interest to our laboratory. In the section titles the name of the speakers
appear, together with the topics discussed in the seminars. We plan to publish
these notes twice a year.


title:
Resummation of threshold corrections in QCD to power accuracy: the
  Drell-Yan cross section as a case study

abstract:
  Resummation of large infrared logarithms in perturbation theory can, in
certain circumstances, enhance the sensitivity to small gluon momenta and
introduce spurious nonperturbative contributions. In particular, different
procedures -- equivalent in perturbation theory -- to organize this resummation
can differ by $1/Q$ power corrections. The question arises whether one can
formulate resummation procedures that are explicitly consistent with the
infrared behaviour of finite-order Feynman diagrams. We explain how this
problem can be treated and resolved in Drell-Yan (lepton pair) production and
briefly discuss more complicated cases, such as top quark production and event
shape variables in the $e^+e^-$ annihilation.


title: Some tests for the helicity structure of the pomeron in $ep$ collisions

abstract:
  We discuss the reaction $e p \to e \tilde{p} X$ in the one-photon exchange
approximation, where it is in essence the reaction $\gamma^{*} p \to \tilde{p}
X$. A large rapidity gap is required between the particle or particles of the
proton remnant $\tilde{p}$ and those of $X$. We define a suitable azimuthal
angle $\varphi$ between a leptonic and a hadronic plane. The dependence of the
cross section on $\varphi$ is given explicitly and can be used to extract cross
sections and interference terms for the reaction $\gamma^{*} p \to \tilde{p} X$
corresponding to the various helicities of the virtual photon $\gamma^{*}$. The
interference terms can be used to test models for the large rapidity gap events
in a sensitive way. We discuss in detail models with factorizing Pomeron
exchange and in particular the Donnachie-Landshoff Pomeron model. We make some
remarks on soft colour exchange models and on possible effects of QCD
background vacuum fields. We conclude with a suggestion to look for Odderon
exchange in exclusive deep inelastic high energy reactions like $\gamma^{*} p
\to \tilde{p} \pi^{0}$ and $\gamma^{*} p \to \tilde{p} \eta$.


title: Quark and Lepton Mass Matrices from Horizontal U(1) Symmetry

abstract:
  In the simplest model of horizontal U(1) symmetry with one singlet added to
the supersymmetric standard model, we systematically reconstruct quark mass
matrices from the low-energy data to prove that there are only two mass
matrices found by Binetruy et.~al.. The same U(1) symmetry constrains the
hierarchical structure of L-violating couplings, from which we build radiative
neutrino mass matrices accommodating the solar and hot dark matter neutrino
masses and mixing. We find a few patterns of acceptable charged lepton and
neutrino mass matrices, most of which are consistent with large $\tan\beta
\simeq m_t/m_b$ only.


title: Alternative Approach to Gaugino Condensation

abstract:
  We examine the mechanism of gaugino condensation in supersymmetric theories
within a Nambu-Jona-Lasinio type approach. We investigate the effective
Lagrangian description of higher energy theories that include some moduli
fields in the gauge coupling constant. First we consider supersymmetric QCD
with and without a mass term. We can find a phase transition in massless
theory, but when we add a mass term, such a phase transition disappears. We
also examine a model with a dilaton dependent coupling constant and find that
it is very similar to supersymmetric QCD. Application of our method to
supergravity is also examined.


title: Bunching Parameter and Intermittency in High-Energy Collisions

abstract:
  We introduce the parameter of bunching for an analysis of the intermittent
structure of multihadron production in high-energy collisions following an
analogy with photon counting in quantum optics. A power-law singularity is
shown to exist for second-order bunching parameters in small phase-space
intervals for the case of a monofractal structure of the multiplicity
distribution and a similar form for the high-order parameters for the case of
multifractality. The approximation of the high-order bunching parameters by the
second-order provides a good description of the anomalous fractal dimensions
for a number of experimental data with multifractal behavior.


title: Bin-Bin Correlation Measurement by the Bunching-Parameter Method

abstract:
  A new method for the experimental study of bin-bin correlations is proposed.
It is shown that this method is able to reveal important additional information
on bin-bin correlations, beyond that of factorial-correlator measurements.


title:
The impossible regularization of the Nambu Jona-Lasinio model with
  vector interactions

abstract:
  We show that the procedure of regularizing the real part of the euclidean
action, while leaving the imaginary part unregularized, leads to a non-analytic
and highly singular functional of the fields. It is customary to work with an
imaginary time component of the vector field, in order to avoid regularization
of the anomalous processes. We show that this procedure is flawed by the fact
that a stationary point of the action occurs for a real, not imaginary, time
component of the vector field. Furthermore the action in the vicinity of the
stationary point is singular. The regularized action is thus not suitable for
an evaluation of the partition function using a saddle point method. We discuss
proposed solutions to this problem, as well as other regularizations. They all
lead to practical problems.


title: Cosmic Vortons and Particle Physics Constraints

abstract:
  We investigate the cosmological consequences of particle physics theories
that admit stable loops of superconducting cosmic string - {\it vortons}.
General symmetry breaking schemes are considered, in which strings are formed
at one energy scale and subsequently become superconducting in a secondary
phase transition at what may be a considerably lower energy scale. We estimate
the abundances of the ensuing vortons, and thereby derive constraints on the
relevant particle physics models from cosmological observations. These
constraints significantly restrict the category of admissible Grand Unified
theories, but are quite compatible with recently proposed effects whereby
superconducting strings may have been formed close to the electroweak phase
transition.


title: The Soft Pomeron

abstract:
  The soft pomeron successfully correlates a wide variety of data. Its
properties seem rather simple: it couples to single quarks and its coupling
factorises.


title: On Dual Descriptions of Intermittency in a Jet

abstract:
  Models of intermittent behaviour are usually formulated using a set of
multiplicative random weights on a Cayley tree. However, intermittency in
particle multiproduction from QCD jets is related to fragmentation of an
additive quantum number, e.g. energy-momentum. We exhibit the non-trivial
stochastic mapping between these {\it additive} and {\it multiplicative}
cascading processes.


title:
Gauge-Invariant Resummation Formalism for Two-Point Correlation
  Functions

abstract:
  The consistent description of unstable particles, renormalons, or other
Schwinger--Dyson-type of solutions within the framework of perturbative gauge
field theories necessitates the definition and resummation of off-shell Green's
functions, which must respect several crucial physical requirements. A
formalism is presented for resummation of off-shell two-point correlation
functions, which is mainly based on arguments of analyticity, unitarity, gauge
invariance and renormalizability. The analytic results obtained with various
methods, including the background field gauges and the pinch technique are
confronted with the physical requirements imposed; to one-loop order the pinch
technique approach satisfies all of them. Using renormalization group
arguments, we discuss issues of uniqueness of the resummation procedure related
to the latter method.


title:
Electric dipole moments and b-$\tau$ unification in the presence of an
  intermediate scale in SUSY grand unification

abstract:
  We show that an intermediate gauge symmetry breaking scale can be a
significant source of electric dipole moments for the electron and neutron in
supersymmetric grand unified theories. New phases, similar to that of the CKM
matrix, appear which do not arise from the supersymmetry (SUSY) breaking
operators. To illustrate, we choose some grand unified SUSY models having an
intermediate gauge symmetry breaking scale with some attractive features. We
also show how well the $b-\tau$ unification hypothesis works in this class of
models.


title: Sphalerons in the MSSM

abstract:
  We construct the sphaleron solution, at zero and finite temperature, in the
Minimal Supersymmetric Standard Model as a function of the supersymmetric
parameters, including the leading one-loop corrections to the effective
potential in the presence of the sphaleron. At zero temperature we have
included the one-loop radiative corrections, dominated by the top/stop sector.
The sphaleron energy $E_{\rm MSSM}$ mainly depends on an effective Higgs mass
${\displaystyle m_h^{\rm eff}=\lim_{m_A\gg m_W} m_h}$, where $m_h$ is the
lightest CP-even Higgs mass and $m_A$ the pseudoscalar mass. We have compared
it with the Standard Model result, with $m_h^{\rm SM}=m_h^{\rm eff}$, and found
small differences (1-2\%) in all cases. At finite temperature we have included
the one-loop effective potential improved by daisy diagram resummation. The
sphaleron energy at the critical temperature can be encoded in the temperature
dependence of the vacuum expectation value of the Higgs field with an error
$\simlt 10$\%. The light stop scenario has been re-examined and the existence
of a window where baryon asymmetry is not erased after the phase transition,
confirmed. Although large (low) values of $m_h$ ($m_A$) are disfavoured by the
strength of the phase transition, that window (along with LEP results) allows
for $m_h\simlt 80$ GeV, $m_A\simgt 110$ GeV and $A_t\simlt 0.4\; m_Q$.


title: The Quark Mass Problem and CP-Violation

abstract:
  A simple breaking of the subnuclear democracy among the quarks leads to a
mixing between the second and the third family, in agreement with observation.
Introducing the mixing between the first and the second family, one finds an
interesting pattern of maximal CP-violation as well as a complete determination
of the elements of the CKM matrix and of the unitarity triangles.


title: Proton structure functions in the dipole picture of BFKL dynamics

abstract:
  The $F_2$, $F_G$, $R = F_L/F_T$ proton structure functions are derived in the
QCD dipole picture. Assuming $k_T$ and renormalization-group factorization, we
relate deep-inelastic proton scattering to deep-inelastic onium scattering. We
get a three-parameter fit of the 1994 H1 data in the low-$x,$ moderate $Q^2$
range. The ratios $F_G/F_2$ and $R$ are predicted without further adjustment.
The dipole picture of BFKL dynamics is shown to provide a relevant model for
quantitatively describing the proton structure functions at HERA. The
predictions for $F_2$ and $F_G$ are compatible with the next-to-leading order
DGLAP analysis, while $R$ is expected to be significantly lower at very small
$x$.


title: Beyond the Standard Model

abstract:
  Elementary introduction to physics beyond the Standard Model. Lectures
delivered at the 1995 European School of High-Energy Physics in Dubna, Russia.


title: Perturbative Regge asymptotics in the case of non-vacuum exchange

abstract:
  Some results on the perturbative Regge asymptotics are reviewed. The concepts
of the reggeon interaction approach and the double logarithmic approximation
are outlined. Contribution to the Zeuthen Workshop on QCD and QED at higher
order, Rheinsberg, April 1996.


title:
Calculation of Feynman diagrams with zero mass threshold from their
  small momentum expansion

abstract:
  A method of calculating Feynman diagrams from their small momentum expansion
[1] is extended to diagrams with zero mass thresholds. We start from the
asymptotic expansion in large masses [2] (applied to the case when all $M_i^2$
are large compared to all momenta squared). Using dimensional regularization, a
finite result is obtained in terms of powers of logarithms (describing the
zero-threshold singularity) times power series in the momentum squared.
Surprisingly, these latter ones represent functions, which not only have the
expected physical `second threshold' but have a branchcut singularity as well
below threshold at a mirror position. These can be understood as
pseudothresholds corresponding to solutions of the Landau equations. In the
spacelike region the imaginary parts from the various contributions cancel. For
the two-loop examples with one mass $M$, in the timelike region for $q^2
\approx M^2$ we obtain approximations of high precision. This will be of
relevance in particular for the calculation of the decay $Z \to b\bar{b}$ in
the $m_b=0$ approximation.


title: Family Structure from Periodic Solutions of an Improved Gap Equation

abstract:
  Fermion mass models usually contain a horizontal symmetry and therefore fail
to predict the exponential mass spectrum of the Standard Model in a natural
way. In dynamical symmetry breaking there are different concepts to introduce a
fermion mass spectrum, which automatically has the desired hierarchy. In
constructing a specific model we show that in some modified gap equations
periodic solutions with several fermion poles appear. The stability of these
excitations and the application of this toy model are discussed. The mass
ratios turn out to be approximately $e^\pi$ and $e^{2\pi}$. Thus the model
explains the large ratios of fermion masses between successive generations in
the Standard Model without introducing large or small numbers by hand.


title: Gauge boson pair production at LEP and NLC

abstract:
  We compute the dominant one-loop radiative corrections to the cross-section
for $e^+ e^- \rightarrow V_1 V_2$ $(V_{1/2} = \gamma, Z, W^\pm$) in the MSSM.
We find that the genuine vertex corrections are very small. The oblique
corrections are potentially large enough to be tested at LEP-II or NLC.
However, the sensitivity is below the one from other high precision
electro-weak measurements but can serve as a self-consistency check.


title:
NLO predictions for the growth of $F_2$ at small $x$ and comparison with
  experimental data

abstract:
  We present parametrizations for the proton structure function $F_2$ in the
next to leading order in perturbative QCD. The calculations show that the
dominant term to $F_2(x,Q^2)$ should grow as $x^{-\ls}$ for small $x$ values,
with the exponent $\ls$ being essentially independent of $Q^2$. Comparisons
with the most recent H1 and ZEUS data confirm the value $\ls \sim 0.35$
obtained previously from fits to low energy data.


title: Physics Motivations for a Muon Collider

abstract:
  Future muon colliders will have remarkable capability for revealing and
studying physics beyond the Standard Model. A first muon collider with variable
c.m.\ energy in the range $\sqrt s = 100$ to 500~GeV provides unique
opportunities for discovery and factory-like production of Higgs bosons in the
$s$-channel. For excellent (but achievable) machine energy resolution, the
total width and $\mupmum$ coupling of a SM-like Higgs boson with mass $\lsim
2\mw$ (as particularly relevant to supersymmetric/GUT models) can be directly
measured with substantial precision. Multiplication of measured branching
ratios by the total width yields the corresponding couplings. As a result, the
light CP-even SM-like Higgs of the minimal supersymmetric model can be
distinguished from the Higgs of the minimal Standard Model over a larger
portion of supersymmetric parameter space than otherwise possible. Scan
discovery and detailed measurements of total widths and some partial widths of
the heavier CP-even and CP-odd Higgs bosons of the minimal supersymmetric model
are possible for Higgs masses up to the maximum $\rts$. The excellent energy
resolution, absence of beamstrahlung and mild bremsstrahlung at the first muon
collider would allow increased precision for the measurement of $\mt$ and $\mw$
via $t\anti t$ and $\wp\wm$ threshold studies. A multi-TeV $\mm$ collider would
open up the realm of physics above the 1 TeV scale. Pair production of
supersymmetric particles up to masses even higher than consistent with
naturalness would be possible, guaranteeing that the heavier gauginos and
possibly very massive squarks would be abundantly produced and that their
properties could be studied. Very importantly, the multi-TeV collider would
guarantee our ability to perform a detailed study of a strongly-interacting


title: B --> D(D^*) Form Factors in a Bethe-Salpeter model

abstract:
  We calculate the form factors for the semileptonic decays of the $B$ meson to
$D$ and $D^*$ mesons in a Bethe-Salpeter model. We show that our model is
consistent with the constraints of Heavy Quark Effective Theory (HQET) and we
extract the matrix elements that represent the $1/m_Q$ corrections to the form
factors in HQET. With available data, we obtain $V_{cb} $=$ (31.9 \pm
1.4)\times10^{-3}$.


title:
Search for supersymmetry with a light gravitino at the Fermilab Tevatron
  and CERN LEP colliders

abstract:
  We analyze the prospects for discovering supersymmetry at the Fermilab
Tevatron and CERN LEP colliders in the scenario that the lightest
supersymmetric particle is a gravitino of mass < 1 keV. We consider in
particular the case that the lightest neutralino has a nearly 100% branching
fraction into gravitino + photon within the detector. This implies that
supersymmetric events should contain both missing (transverse) energy and two
energetic photons. Therefore one can search for supersymmetry simply through
inclusive production of superpartners. We consider the exclusion and reach
capabilities of the Tevatron in exploring the supersymmetric parameter space,
and study the efficiencies which can be achieved in this search. We also
consider the discovery reach and backgrounds at LEP with $\sqrt{s} =$ 160, 175,
and 190 GeV.


title: Lambda Oscillations and the Conservation Laws

abstract:
  Lowe, Bassalleck, Burkhardt, Rusek, Stephenson, and Goldman assert, under the
assumption of decays at fixed space-time points, that Kaon induced Lambda
oscillations disappear. We find, under the same assumption, that energy
conservation and momentum conservation also disappear. Ordinary particles can
exhibit quantum oscillations.


title: Weak Mixing Angles as Dynamical Degrees of Freedom

abstract:
  In an analogy to the case of axion, which converts the $\Theta$-angle into a
dynamical degree of freedom, we are trying to imagine a situation where the
quark mixing angles turn out to be dynamical degrees of freedom
(pseudo-Goldstone bosons), and their vacuum expectation values are obtained
from the minimization of the vacuum energy. We present an explicit
supersymmetric model with horizontal symmetry, where such a mechanism can be
realized. It implies one relation between the quark masses and the CKM mixing
angles: $s_{13}s_{23}/s_{12}=(m_s/m_b)^2$, which is fulfilled within present
experimental accuracy. We believe, however, that the idea might be more general
than this concrete model, and it can be implemented in more profound
frameworks.


title:
Fixing the renormalisation scheme in NNLO perturbative QCD using
  conformal limit arguments

abstract:
  We discuss how the renormalisation scheme ambiguities in QCD can be fixed,
when two observables are related, by requiring the coefficients in the
perturbative expansion relating the two observables to have their conformal
limit values, i.e. to be independent of the $\beta$-function of the
renormalised coupling. We show how the next-to-leading order BLM automatic
scale fixing method can be extended to next-to-next-to-leading order to fix
both the renormalisation scale and $\beta_2$ in a unique way. As an example we
apply the method to the relation between Bjorken's sum rule and $R_{e+e-}$ and
compare with experimental data as well as other scheme fixing methods.


title: The Extended Chiral Bosonisation And Pion-Diquark Effective Action

abstract:
  We consider bosonisation of the low-energy QCD based on integrating the
anomaly of the extended chiral (E$\chi$) transformation which depends both on
pseudoscalar meson and scalar diquark fields as parameters. The relationship
between extended chiral and usual chiral anomalies and related anomalous
actions is studied. The effective action for the extended chiral field $\U$
depending on complete set of anomalous generators of the E$\chi$-transformation
is given. The terms of this effective action relevant to interaction of pions
and $\bar 3_c$ scalar diquarks are written down explicitly.


title: A leptophobic massive vector boson at the Tevatron and the LHC

abstract:
  Recent measurements of the single inclusive jet cross section at the Tevatron
by the CDF Collaboration maybe suggest a modified picture of QCD in the large
$E_T$ range. One possible explanation of the measured jet excess is the
introduction of a neutral heavy vector boson $Z'$. A parameter fit of this new
model to the CDF data, in leading order perturbation theory, is performed, and
the question of how the corresponding single inclusive jet cross sections and
the dijet angular distributions at the LHC are affected by this additional $Z'$
is discussed. We conclude that the $Z'$ will play a pivotal role for typical
LHC centre-of-mass energies, thus providing a direct test of this theory.


title: Next-to-Leading Corrections to the BFKL Equation

abstract:
  Using the helicity formalism in the high-energy limit, we compute the
amplitudes which generate the real next-to-leading-logarithmic corrections to
the BFKL equation. Accordingly, we provide a list of all the off-shell vertices
necessary to build such amplitudes.


title: MeV neutrinos in double beta decay

abstract:
  The effect of Majorana neutrinos in the MeV mass range on the double beta
decay of various isotopes is studied on pure phenomenological arguments. By
using only experimental half life data, limits on the mixing parameter
$U_{eh}^2$ of the order 10$^{-7}$ can be derived. Also the possible
achievements of upcoming experiments and some consequences are outlined.


title: Higher Order QCD Corrections to $b\to c\overline{c}s$

abstract:
  We calculate the ${\cal O}(\alpha_s^2 \beta_0 )$ corrections to the decay
rate $b\rightarrow c\bar c s$. For reasonable values of $m_c/m_b$ this term is
of the same order as both the one-loop and $\CO(\alpha_s^2 \log^2 m_W/m_b)$
corrections to the decay rate. For $m_c/m_b=0.3$ the $\CO(\alpha_s^2\beta_0)$
corrections enhance the rate by $\sim 18\%$ . We also discuss the
$\CO(\alpha_s^2\beta_0)$ corrections to $R_\tau$, the $B$ semileptonic
branching fraction and the charm multiplicity.


title: Unusual Charged Higgs Signals at LEP-2

abstract:
  We have made a detailed study of the signals produced at LEP-2 from charged
scalar bosons whose dominant decay channels are into four fermions. The event
rates as well as kinematics of the final states are discussed when such scalars
are either pair-produced or are generated through a tree-level interaction
involving a charged scalar, the W and the Z. The backgrounds in both cases are
discussed. We also suggest the possibility of reconstructing the mass of such a
scalar at LEP-2.


title:
Experimental Consequences of a Minimal Messenger Model for Supersymmetry
  Breaking

abstract:
  We calculate the low-lying spectrum of new particles expected in a minimal
model wherein supersymmetry breaking at < 100 TeV is indirectly transmitted to
the Standard Model. We calculate the couplings of these particles relevant to
their most nearly accessible experimental signatures, and estimate those
signatures quantitatively. Running of various couplings plays a crucial role in
the phenomenology, specifically in generating an adequate $\neutralino_1 -
\slepton_R$ splitting.


title:
Convergence of Discretized Light Cone Quantization in the small mass
  limit

abstract:
  I discuss the slow convergence of Discretized Light Cone Quantization (DLCQ)
in the small mass limit and suggest a solution.


title:
Coulomb wave function correction including momentum resolution for
  charged hadron pairs: Analysis of data for $\pi^+\pi^-$ pair production in
  $p\;+$ Ta reaction at 70 GeV/c

abstract:
  We propose a new method for the Coulomb wave function correction including
the momentum resolution for charged hadron pairs and apply it to the precise
data on $\pi^+\pi^-$ correlations obtained in $p + \mbox{Ta}$ reaction at 70
GeV/c. It is found that interaction regions of this reaction (assuming Gaussian
source function) are $5.6 \pm 3.0$ and $4.4 \pm 2.6$ fm for the thicknesses of
the target $8$ and $1.4$ microns, respectively. The physical picture of the
source size obtained in this way is discussed.


title:
Possible Measurements of Single and Double Spin Asymmetries with
  HERA--$\vec{N}$

abstract:
  The physics scope of a possible future experiment utilizing an internal
polarized nucleon target in the HERA proton beam is discussed. By measuring
single spin asymmetries in inclusive particle production at 820~GeV beam energy
the higher-twist sector of perturbative QCD can be probed with good statistical
sensitivity. To support the physics case for proton polarization at HERA, we
consider the measurement of double spin asymmetries in photon plus jet
production. It appears possible to determine the polarized gluon distribution
in the range 0.1~$\leq x_{gluon} \leq$~0.4 with good accuracy.


title:
SUSY--QCD corrections to scalar quark decays into charginos and
  neutralinos

abstract:
  We calculate the supersymmetric QCD corrections in order $\alpha_s$ to the
decays $\squark_i \to q' \chargino_j$ (i,j = 1,2) and $\squark_i \to q
\neutralino_k$ (k = 1,...4) within the Minimal Supersymmetric Standard Model.
In particular we consider the decays of squarks of the third generation,
$\stop_i$ and $\sbottom_i$ (i = 1,2), where the left--right mixing must be
taken into account. The corrections turn out to be of about 10\%, except for
higgsino--like charginos or neutralinos, where they can go up to 40\%.


title:
Is CP Violation Observable in Long Baseline Neutrino Oscillation
  Experiments ?

abstract:
  We have studied CP violation originated by the phase of the neutrino mixing
matrix in the long baseline neutrino oscillation experiments. The direct
measurements of CP violation is the difference of the transition probabilities
between CP-conjugate channels. In those experiments, the CP violating effect is
not suppressed if the highest neutrino mass scale is taken to be $1\sim 5 \eV$,
which is appropriate for the cosmological hot dark matter. Assuming the
hierarchy for the neutrino masses, the upper bounds of CP violation have been
caluculated for three cases, in which mixings are constrained by the recent
short baseline ones. The calculated upper bounds are larger than $10^{-2}$,
which will be observable in the long baseline accelerator experiments. The
matter effect, which is not CP invariant, has been also estimated in those
experiments.


title: Automatic Calculation of SUSY-particle Production

abstract:
  We introduce a new method to treat Majorana fermions and interactions with
fermion-number violation on the GRACE system which has been developed for the
automatic computation of the matrix elements for the processes of the standard
model. Thus we have constructed a system for the automatic computation of
cross-sections for the processes of the minimal SUSY standard model (MSSM).


title: Fermion Virtual Effects in $e^+ e^- -> W^+ W^-$ Cross Section

abstract:
  We analyse the contribution of new heavy virtual fermions to the $e^+e^-
\rightarrow W^+W^-$ cross section. We find that there exists a relevant
interplay between trilinear and bilinear oblique corrections. The result
strongly depends on the chiral or vector--like nature of the new fermions. As
for the chiral case we consider sequential fermions: one obtains substantial
deviation from the Standard model prediction, making the effect possibly
detectable at $\sqrt{s}=500$ or $1000$ GeV linear colliders. As an example for
the vector--like case we take a SUSY extension with heavy charginos and
neutralinos: due to cancellation, the final effect turns out to be negligible.


title:
Measurement of muon polarization in $K^+\to\pi^0\mu^+\nu_\mu$ at a
  $\phi$ factory

abstract:
  The potentiality of an experiment measuring the muon polarization in
$K^+\rightarrow\pi^0\mu^+\nu_\mu$ at a $\phi$ factory is discussed, with
particular attention to the possibility of revealing unexpected violation of
Time reversal invariancethrough the transverse polarization component. An
experimental method is proposed which is based on the reconstruction of the
$K^+\rightarrow\pi^0\mu^+\nu_\mu$ decay products after stopping the charged
kaons in a target placed around the beam pipe. The muon polarization is
measured by observing the asymmetry in the angular distribution of positrons
from the $\mu^+ \rightarrow e^+ \nu \bar{\nu}$ decay of muons stopped in a
polarization analyser. It is shown that an error $\sigma_P\simeq 5\cdot
10^{-4}$ on each muon polarization component can be obtained, which represents
a factor ten improvement with respect to current limits on T invariance
violation in the $K^+\rightarrow\pi^0\mu^+\nu_\mu$ decay and a precise
measurement of the $Re\xi$ parameter at the level of $2\cdot 10^{-3}$.


title: A Dynamical Model for Nuclear Structure Functions

abstract:
  We construct a dynamical model for the parton distributions in a nucleus by
perturbative evolution of input distributions from a low starting scale. These
input distributions are obtained by modifications of the corresponding free
nucleon ones; the modifications being determined by standard nuclear physics
considerations. The model gives good agreement with existing data. Its
extension to the spin dependent case enables an estimation of nuclear
modifications to asymmetries observed in recent doubly polarised deep inelastic
scattering experiments. Although the structure functions themselves are very
different from the free nucleon ones, their ratio is insensitive to these
changes.


title: Invariant formulation of CP violation for four quark families

abstract:
  We find a minimal set of constraints which are independent of the choice of
weak quark basis and necessary and sufficient for CP conservation for four
quark families, including also the case of degenerate quark masses. These
invariant conditions are written in the mass eigenstate basis as a function of
the fermion masses and charged current mixings. CP violation is then related to
the areas of three unitarity quadrangles and the CP violating effects of the
fourth family are discussed in the case of small mixings.


title:
Enhanced Supersymmetric Corrections to Top-Quark Production at the
  Tevatron

abstract:
  We calculate the one-loop supersymmetric electroweak-like and QCD-like
corrections to the top-quark pair-production cross section at the Tevatron,
including the important effects of non-degenerate top-squarks and left-right
top-squark mixing. The largest electroweak effects yield a negative shift in
the cross section and are enhanced right below the threshold for top-quark
decay into top-squark and higgsino-like neutralino, and can be as large as
$-35\%$. The largest QCD effects are positive and are enhanced for light
top-squark masses, and can be as large as $20\%$. Such shifts greatly exceed
the present theoretical uncertainty in the Standard Model prediction, and
therefore may be experimentally observable. We also explore the one-loop shifts
in scenarios containing light top-squarks and higgsino-like neutralinos that
have been recently proposed to explain various apparent experimental anomalies.


title: High-Energy Approximation of One-Loop Feynman Integrals

abstract:
  We provide high-energy approximations for all one-loop scalar 3- and 4-point
functions and the corresponding tensor integrals that appear in scattering
processes with four external on-shell particles. Our expressions are valid if
all kinematical invariants are much larger than the internal and external
masses. They contain all leading-order terms of the integrals.


title: Renormalization in light--cone gauge: how to do it in a consistent way

abstract:
  We summarize several basic features concerning canonical equal time
quantization and renormalization of Yang--Mills theories in light--cone gauge.
We describe a ``two component" formulation which is reminiscent of the
light--cone hamiltonian perturbation rules. Finally we review the derivation of
the one--loop Altarelli--Parisi densities, using the correct causal
prescription on the ``spurious" pole.


title:
Hidden Local Symmetry for Anomalous Processes with Isospin/SU(3)
  Breaking Effects

abstract:
  We show that isospin/SU(3) breaking terms can be introduced to the anomalous
VVP coupling in the hidden local symmetry scheme without changing
Wess-Zumino-Witten term in the low-energy limit. We make the analysis for
anomalous processes of 2-body and 3-body decays; radiative vector meson
decays(V \to P\gamma), conversion decays of photon into a lepton pair(V \to P
l^+ l^-) and hadronic anomalous decays(V \to PPP). The predictions successfully
reproduce all experimental data of anomalous decays. In particular, we predict
the decay widths of \rho^0 \to \pi^0 \gamma and \phi \to \eta' \gamma as 101
\pm 9 keV and 0.508 \pm 0.035 keV, respectively, which will be tested in the
DAFNE \phi-factory. Moreover, prediction is also made for \phi \to \pi^0 e^+
e^-, \rho \to 3\pi, K^* \to K \pi \pi and so on, for which only the
experimental upper bounds are available now.


title: To rescue a star

abstract:
  Massless neutrinos are exchanged in a neutron star, leading to long range
interactions. Many body forces of this type follow and we resum them. Their net
contribution to the total energy is negligible as compared to the star mass.
The stability of the star is not in danger, contrary to recent assertions.


title:
More nonperturbative corrections to the fine and hyperfine splitting in
  the heavy quarkonium

abstract:
  The leading nonperturbative effects to the fine and hyperfine splitting were
calculated some time ago. Recently, they have been used in order to obtain
realistic numerical results for the lower levels in bottomonium systems. We
point out that a contribution of the same order $O(\Lambda_{QCD}^4/m^3
\alpha_s^2)$ has been overlooked. We calculate it in this paper.


title:
Deep-Inelastic Final States in a Space-Time Description of Shower
  Development and Hadronization

abstract:
  We extend a quantum kinetic approach to the description of hadronic showers
in space, time and momentum space to deep-inelastic $ep$ collisions, with
particular reference to experiments at HERA. We follow the history of hard
scattering events back to the initial hadronic state and forward to the
formation of colour-singlet pre-hadronic clusters and their decays into
hadrons. The time evolution of the space-like initial-state shower and the
time-like secondary partons are treated similarly, and cluster formation is
treated using a spatial criterion motivated by confinement and a
non-perturbative model for hadronization. We calculate the time evolution of
particle distributions in rapidity, transverse and longitudinal space. We also
compare the transverse hadronic energy flow and the distribution of observed
hadronic masses with experimental data from HERA, and find encouraging results.
The techniques developed in this paper may be applied in the future to more
complicated processes such as eA, pp, pA and AA collisions.


title: Physics Prospects at Future e+e- Colliders

abstract:
  I discuss the physics prospects at future high--energy $e^+ e^-$ linear
colliders. After summarizing some aspects of these future machines, I will
review a few topics in the Standard Model which can be studied at these
colliders: top quark, $W/Z$ vector bosons and Higgs particles physics. A brief
discussion on the exploration of extensions of the Standard Model such as
Supersymmetry and Grand Unified Theories at $\ee$ colliders will also be given.
(Invited talk given at Les Rencontres de Physique de la Vall\'ee d'Aoste, La
Thuile March 3-9 1996).


title:
The stability of the MSW solution to the solar neutrino problem with
  respect to random matter density perturbations

abstract:
  We present a generalization of the resonant neutrino conversion in matter,
including a random component in the matter density profile. The study is
focused on the effect of such matter perturbations upon both large and small
mixing angle MSW solutions to the solar neutrino problem. This is carried out
both for the active-active $\nu_e \ra \nu_{\mu,\tau}$ as well as active-sterile
$\nu_e \ra \nu_s$ conversion channels. We find that the small mixing MSW
solution is much more stable (especially in $\delta m^2$) than the large mixing
solution. Future solar neutrino experiments, such as Borexino, could probe
solar matter density noise at the few percent level.


title: Double-logarithmic Scaling of the Structure Function F_2 at small x

abstract:
  Recent data on the structure function F_2(x,Q^2) at small values of x are
analysed and compared with theoretical expectations. It is shown that the
observed rise at small x is consistent with a logarithmic increase, growing
logarithmically also with Q^2. A stronger increase, which may be incompatible
with unitarity when extrapolated to asymptotically small values of x, cannot be
inferred from present data.


title:
One-loop QCD Correction for Inclusive Jet Production and Drell-Yan
  Process in Composite Models

abstract:
  We calculate the one-loop QCD correction for inclusive jet cross section and
Drell-Yan process in a general low-energy effective Lagrangian for composite
quarks and leptons.


title: Signals for Double Parton Scattering at the Fermilab Tevatron

abstract:
  Four double-parton scattering processes are examined at the Fermilab Tevatron
energy. With optimized kinematical cuts and realistic parton level simulation
for both signals and backgrounds, we find large samples of four-jet and
three-jet+one-photon events with signal to background ratio being 20\%-30\%,
and much cleaner signals from two-jet+two-photon and two-jet+$e^+e^-$ final
states. The last channel may provide the first unambiguous observation of
multiple parton interactions, even with the existing data sample accumulated by
the Tevatron collider experiments.