title: Form Factors in D Meson Decays

abstract:
  We study the $d\Gamma / dq^2$ spectra and the branching fractions of the $D$
meson exclusive semileptonic decays with the lepton mass effects into
consideration. We investigate their sensitivity to form factor models, and find
that the decays to a pseudoscalar meson and a lepton pair are sensitive to the
property of the form factor $F_1(q^2)$, and those to a vector meson and a
lepton pair to the form factor $A_1(q^2)$. We also analyze the experimental
results of the branching fractions $\cal{B} (D^0\to K^- (or \pi^-) \pi^+)$ and
$\cal{B} (D^0\to K^- (or \pi^-) e^+ \nu)$, and show that it is implied that
$F_1(q^2)$ is of dipole type, instead of simple pole type which is commonly
assumed.


title: Pomeron Flux Renormalization: A Scaling Law in Diffraction

abstract:
  The pomeron flux renormalization hypothesis is reviewed and presented as a
scaling law in diffraction. Predictions for soft and hard diffraction based on
pomeron flux scaling are compared with experimental results.


title: Light-Cone Meson-Baryon Fluctuations and Single-Spin Asymmetries

abstract:
  We show that energetically favored meson-baryon fluctuations present in the
light-cone wave function of a transversely polarized proton can account for the
left-right asymmetries measured in inclusive meson production processes.


title:
Entanglement of Fock-space expansion and covariance in light-front
  Hamiltonian dynamics

abstract:
  We investigate in a model with scalar ``nucleons'' and mesons the
contributions of higher Fock states that are neglected in the ladder
approximation of the Lippmann-Schwinger equation. This leads to a breaking of
covariance, both in light-front and in instant-form Hamiltonian dynamics. The
lowest Fock sector neglected has two mesons in the intermediate state and
corresponds to the stretched box. First we show in a simplified example that
the contributions of higher Fock states are much smaller on the light-front
than in instant-form dynamics. Then we show for a scattering amplitude above
threshold that the stretched boxes are small, however, necessary to retain
covariance. For an off energy-shell amplitude covariance is not necessarily
maintained and this is confirmed by our calculations. Again, the stretched
boxes are found to be small.


title: Discovery potential for supersymmetry in CMS

abstract:
  This work summarizes and puts in an overall perspective studies done within
CMS concerning the discovery potential for squarks and gluinos, sleptons,
charginos and neutralinos, SUSY dark matter, lightest Higgs, sparticle mass
determination methods and the detector design optimisation in view of SUSY
searches. It represents the status of our understanding of these subjects as of
Summer 1997.
  As a benchmark model we used the minimal supergravity-inspired super-
symmetric standard model (mSUGRA) with a stable LSP. Discovery of SUSY at the
LHC should be relatively straightforward. It may occur through the observation
of a large excesses of events in missing E_T + jets, or with one or more
isolated leptons. An excess of trilepton events or of isolated dileptons with
E_T^miss, exhibiting a characteristic signature in the l^+l^- invariant mass
distribution could also be the first manifestation of SUSY production. Squark
and gluino production may represent a copious source of Higgs bosons through
cascade decays. The lightest SUSY Higgs h->bbbar may be reconstructed with a
signal/background ratio of order 1. The lightest supersymmetric particle of
SUSY models with conserved R-parity represents a very good candidate for the
cosmological dark matter. The region of parameter space where this is true is
well-covered by our searches, at least for tan(beta)=2.
  If supersymmetry exists at electroweak scale it could hardly escape detection
in CMS, and the study of supersymmetry will form a central part of our physics
program.


title: Theoretical description of the HERA data on $F_2$

abstract:
  It is shown that the CKMT model for the nucleon structure function $F_2$
gives a good description of the recent HERA data at low and moderate $Q^2$.
Also the fit to the same data obtained with a modified version of the model in
which a logarithmic dependence on $Q^2$ has been included, is presented. For
moderate values of $Q^2$, in the current available range of $x$, the first
parametrization leads to a better description of the data.


title: The Unpolarized Gluon Anomalous Dimension at Small x

abstract:
  We discuss the quantitative consequences of the resummation of the small-x
contributions to the anomalous dimensions beyond next-to-leading order in
alpha_s and up to next order in ln(1/x) (NLx) in a framework based on the
renormalization group equations. We find large and negative effects leading to
negative values for the {\sf total} splitting function P_{gg}(x,alpha_s)
already for x \lsim 0.01 at Q^2 \simeq 20 GeV^2. Terms less singular than those
under consideration turn out to be quantitatively as important and need to be
included. We derive the effects of the conformal part of the NLx contributions
to the anomalous dimensions and discuss the exponent omega describing the
s^omega behavior of inclusive cross sections.


title: Factorisation in Higher-Twist Single-Spin Amplitudes

abstract:
  We analyse the twist-three amplitudes that can give rise to single-spin
asymmetries in hadron-hadron scattering; in so doing we bring to light a novel
factorisation property. As already known, the requirement of an imaginary part
leads to consideration of twist-three contributions that are also related to
transverse spin in deep-inelastic scattering. In particular, when an external
line becomes soft in contributions arising from three-parton correlators, the
imaginary part of an internal propagator may be exposed. As shown here, it is
precisely this kinematical configuration that permits the factorisation. An
important feature is the resulting simplification: the calculation of tens of
Feynman diagrams normally contributing to such processes is reduced to the
evaluation of products of the simple factors derived here and known two-body
helicity amplitudes. We thus find clarifying relations between the
spin-dependent and spin-averaged cross-sections and formulate a series of
selection rules. In addition, the kinematical dependence of such asymmetries,
is rendered more transparent.


title: Random Matrices and Chiral Symmetry in QCD

abstract:
  In this talk we review some recent results from random matrix models as
applied to some non-perturbative issues in QCD. All of the issues we will
discuss touched upon the important phenomenon related to the spontaneous
breaking of chiral symmetry. The afore mentioned insights are: 1. Spontaneous
breakdown of chiral symmetry and disorder. 2. Universal microscopic properties
of the eigenvalues of the Dirac operator in the vacuum. 3. Universal
microscopic properties of the eigenvalues of the Dirac operator in matter. 4.
Structural changes of the Dirac spectrum - finite temperature. 5. Structural
changes of the Dirac spectrum - finite baryonic density - ``phony vacua'' 6.
Structural changes of the Dirac spectrum - finite baryonic density - ``true
vacua'' . 7. Phase diagram. 8. Critical parameters. 9. Critical exponents. 10.
$U(1)_A$ problem. 11. Screening of the pseudoscalar susceptibility. 12. Strong
CP violation (finite $\theta$).


title: BFKL Physics in Dijet Production at the LHC

abstract:
  The production in hadron-hadron collisions of jet pairs with large rapidity
separation and comparable modest transverse momentum is, in principle,
described by the perturbative QCD BFKL equation. The measurement of such jet
pairs appears well suited to the LHC detectors, with their ability to detect
forward jets. We present predictions for dijet cross sections and correlations
obtained using a BFKL Monte Carlo which allows kinematic and other subleading
effects to be incorporated. The enhanced phase space for gluon emission at the
LHC makes the BFKL behavior somewhat easier to observe than at the Tevatron,
although kinematic effects are still important. The production of forward jets
in association with heavy Higgs bosons via the gauge boson fusion mechanism is
also studied and compared with QCD dijet production.


title: Random Matrix Model for Wilson Fermions on the Lattice

abstract:
  We describe a random matrix model suitable for the simulation of the
eigenvalues of the Dirac operator on the lattice for Wilson fermions. We
compare the obtained global eigenvalue spectrum for various values of the
hopping parameter \kappa with lattice results of Kalkreuter. The agreement is
surprisingly good.


title: Measurement of Helicity Parameters in Top Quark Decay

abstract:
  The standard model(SM) predicts only a $g_{V-A}$ coupling in $t \to W^+ b$
decay. However, if additional Lorentz structures exist, they can manifest
themselves in high energy processes such as this via non-SM values of the
helicity parameters describing $t \to W^+ b$. Plots and tables of the values of
these helicity parameters are obtained for various coupling strengths. Three
phase-type ambiguities are uncovered: $g_{V-A} + g_{S+P}$ with effective-mass
scale $\Lambda_{S+P} \sim -35 GeV, g_{V-A} + g_{f_M + f_E}$ with $\Lambda_{f_M
+ f_E} \sim 53 GeV$, and an arbitrary sign-flip in the $b_L$ amplitudes $A_{X}
(\lambda_b = - 1/2) = - A_{V-A} (\lambda_b = - 1/2)$. These ambiguities are
analyzed so that they might be partially resolved when experiments resume at
the Fermilab Tevatron.


title: $\Lambda-\pi$ phase shift in Chiral Perturbation Theory

abstract:
  We calculate the S and P wave phase shifts in $\Lambda - \pi$ scattering at
the $\Xi$ mass using the full relativistic $SU(3)_L \times SU(3)_R$ chiral
perturbation theory. We get small phase shifts similar to previous calculations
using $ SU(2)_L \times SU(2)_R$ chiral perturbation theory in the heavy baryon
limit. We also consider possible off--shell effects in the coupling of the
Rarita-Schwinger particle $\Sigma^*(1385)$. Using SU(3) we estimate the
off--shell coupling of the $\Sigma^*$ to $\Lambda \pi$ from the off--shell
coupling of the $\Delta$ to $N \pi$ which is obtained from a fit to the
pion--nucleon data. We find that the contributions from the off--shell coupling
can be of the same size as the other terms in the $\Lambda \pi$ scattering
amplitude.


title: Indirect Search for CP Violation in Neutrino Oscillations

abstract:
  We propose the indirect search for the CP violating phase in the long
baseline $\n_\m \Ar\n_e$ oscillation experiment, in which two scenarios of the
neutrino mass hierarchy are discussed in the three family model. The CP
violatig phase effect is clearly found in the scenario: the LSND data plus the
atmospheric neutrino deficit. The phase dependence of the oscillation
probability is explicitly shown by using typical parameters of the K2K
experiment. The matter effect is negligibly small. In order to select the
scenario of the neutrino mass hierarchy, the measurement of the
$\n_e\Ar\n_\tau$ oscillation is also proposed in the long baseline experiment.


title: Rescuing Grand Unification Scenario for Neutrino Mass

abstract:
  The see-saw mechanism for neutrino masses based on the Grand Unification
leads to the mass of the heaviest neutrino ($\approx \nu_{\tau}$) in the range
$(2 - 3)\cdot 10^{-3}$ eV and hence to a solution of the solar neutrino problem
through the $\nu_e-\nu_\t$ conversion. We suggest the existence of a light
singlet fermion $S$ which mixes predominantly with muon neutrino through the
mixing mass $m_{\mu s} \sim O(1)$ eV. The introduction of such a singlet allows
one (i) to solve the atmospheric neutrino problem via the $\nu_{\mu}
\leftrightarrow S$ oscillations, (ii) to explain the LSND result and (iii) to
get two component hot dark matter in the Universe. The phenomenology of this
scenario is considered and the origin of the singlet as well as of the scale
$m_{\m s}$ is discussed.


title: Quark Asymmetries in the Proton

abstract:
  We review recent experimental and theoretical developments in the study of
the sea quark structure of the proton. In the light quark sector, we analyse
the recent pp and pD Drell-Yan data from the E866/NuSea experiment at Fermilab,
and their implication for the d-bar/u-bar asymmetry in the proton. The current
status of the strange content of the proton, including the possible difference
between strange and antistrange quark distributions and strangeness form
factors, is updated. Finally, we point out the ramifications of non-symmetric
charm and anticharm distributions in the nucleon for HERA event rates at large
x and Q^2.


title: Quark Mass Hierarchies, Flavor Mixing and Maximal CP-Violation

abstract:
  Flavor mixing and the quark mass spectrum are intimately related. In view of
the observed strong hierarchy of the quark and lepton masses and of the flavor
mixing angles it is argued that the description of flavor mixing must take this
into account. One particular interesting way to describe the flavor mixing
emerges, which is particularly suited for models of quark mass matrices based
on flavor symmetries. We conclude that the unitarity triangle important for $B$
physics should be close to or identical to a rectangular triangle. $CP$
violation is maximal in this sense.


title: Hadron Interactions - Hadron Sizes

abstract:
  A geometrical model of hadron-proton interactions has been extended to
describe gamma-proton total cross section measured in deep-inelastic scattering
at small x (x<0.04). Experimental data are consistent with this model assuming
that the hadronic fluctuation of the virtual photon has a size of <r^2> ~
1/(4m_q^2 + Q^2), where m_q is the mass of the light constituent quark.


title:
Pulsar velocities due to a violation of the equivalence principle by
  neutrinos

abstract:
  We consider the pulsar velocity problem and relate it to some unconventional
neutrino oscillation mechanisms based on a violation of the equivalence
principle by neutrinos. We show that the observed pulsar velocities may be
explained by violations at the level from 10^{-9} to 10^{-10} in the case of a
non-universal tensor neutrino-gravity coupling, whereas there is no solution in
the case of a non-universal scalar neutrino-gravity coupling. Neutrinos may
remain massless and the requisite magnetic field strength is similar to that in
the conventional mass oscillation mechanism.


title:
SU(3) Breaking in Hyperon Beta Decays: a Prediction for Xi^0 -> Sigma^+
  e nu-bar

abstract:
  On the basis of a previous analysis of hyperon semi-leptonic decay data, a
prediction is presented for g_1/f_1 in the Xi^0 -> Sigma^+ e nu-bar beta-decay.
The analysis takes into account SU(3) breaking in this sector via the inclusion
of mass-driven corrections. A rather precise measurement of the above channel
by the KTeV experiment at Fermilab will shortly be available. Since the
dependence on the SU(3) parameters, F and D, is identical to that of the
neutron beta-decay, such a measurement will provide a rather stringent test of
SU(3) and the models used to describe its violation in these decays. The
prediction given here for the above decay is g_1/f_1=1.17, which leads to a
rate of 0.80 x 10^6 s^-1 and thus a branching fraction of 2.3 x 10^-4.


title:
Tau Lepton Mixing with Charginos and its Effects on Chargino Searches at
  e+e- Colliders

abstract:
  In bilinear R-Parity violating models where a term \epsilon_3L_3H_2 is
introduced in the superpotential, the tau lepton can mix with charginos. We
show that this mixing is fully compatible with LEP1 precision measurements of
the Z\tau\tau and W\tau\nu_\tau couplings even for large values of \epsilon_3
and of the induced vacuum expectation value v_3 of the tau-sneutrino. The
single production of charginos at e+e- colliders is possible in this case and
we present numerical values of the cross-section at LEP1, LEP2 and an NLC. We
find maximum values of 10 pb at LEP1 and 1 fb at NLC, while the corresponding
values at LEP2 are too small to observe.


title: Inelastic photon-neutrino interactions using an effective Lagrangian

abstract:
  We justify the feasibility of substituting a photon leg by a neutrino current
in the Euler-Heisenberg Lagrangian to obtain an effective Lagrangian for the
process $\gamma\nu\to\gamma\gamma \nu$ and its crossed reactions. We establish
the link between these processes and the four-photon scattering in both the
Standard Model and the effective theory. As an application, we compute the
processes $\gamma\nu\to\gamma\gamma\nu$ and
$\gamma\gamma\to\gamma{\nu}\bar\nu$, give their polarized cross sections, and
show how to use the $\gamma\gamma\to\gamma\gamma$ results as a check. We settle
the question about the disagreement between two computations in the literature
concerning the reaction $\gamma\gamma\to \gamma \nu\bar\nu$.


title: Diffraction: Results and Conclusions

abstract:
  We summarize the main features of available experimental results on soft and
hard diffraction and draw conclusions about the nature of the pomeron.


title: The Electromagnetic Mass Difference of Pions at Low Temperature

abstract:
  We compute low temperature corrections to the electromagnetic mass difference
of pions in the chiral limit. The computation is done in a model independent
way in the framework of chiral perturbation theory, using the background field
method and the hard thermal loop approximation. We also generalize at low
temperature the sum rule of Das et al. We find that the mass difference between
the charged and neutral pions decreases at low temperature $T$ with respect to
the T=0 value. This is so in spite of the fact that charged particles always
get a thermal correction to their masses of order $\sim eT$, where $e$ is the
gauge coupling constant. Our result can be understood as a consequence of the
tendency towards chiral symmetry restoration at finite temperature.


title:
Chemical non-equilibrium and deconfinement in 200 A GeV Sulphur induced
  reactions

abstract:
  We interpret hadronic particle abundances produced in S--Au/W/Pb 200 A GeV
reactions in terms of the final state hadronic phase space model and determine
by a data fit of the chemical hadron freeze-out parameters. Allowing for the
flavor abundance non-equilibrium a highly significant fit to experimental
particle abundance data emerges, which supports possibility of strangeness
distillation. We find under different strategies stable values for freeze-out
temperature T_f=143\pm3 MeV, baryochemical potential \mu_B= 173\pm6 MeV, ratio
of strangeness (\gamma_s) and light quark (\gamma_q) phase space occupancies
\gamma_s/\gamma_q=0.60\pm0.02, and \gamma_q=1.22\pm0.05 without accounting for
collective expansion (radial flow). When introducing flow effects which allow a
consistent description of the transverse mass particle spectra, yielding
|v_c|=0.49\pm0.01c, we find \gamma_s/\gamma_q=0.69\pm0.03,
\gamma_q=1.41\pm0.08. The strange quark fugacity is fitted at
\lambda_s=1.00\pm0.02 suggesting chemical freeze-out directly from the
deconfined phase.


title: Bi-Maximal Mixing of Three Neutrinos

abstract:
  We show that if the solar and atmospheric data are both described by maximal
vacuum oscillations at the relevant mass scales then there exists a unique
mixing matrix for three neutrino flavors. The solution necessarily conserves CP
and automatically implies that there is no disappearance of atmospheric
$\nu_e$, consistent with indications from the Super-Kamiokande experiment. We
also investigate the consequences for three-neutrino mixing if the solar and
atmospheric oscillations exhibit mixing that is large but not maximal. For
non-maximal mixing $\nu_e\leftrightarrow\nu_\tau$ and
$\nu_e\leftrightarrow\nu_\mu$ oscillations are predicted that may be observable
in future long-baseline experiments.


title: A novel factorization for $F_L$ in the large $x$ limit

abstract:
  A novel factorization formula is presented for the longitudinal structure
function $F_L$ near the elastic region $x \to 1$ of deeply inelastic
scattering. In moment space this formula can resum all contributions to $F_L$
that are of order $\ln^k N/N$. This is achieved by defining a new jet function
which probes the transverse momentum of the struck parton in the target at
leading twist. The anomalous dimension $\gamma_{J^\prime}$ of this new jet
operator generates in moment space the logarithmic enhancements coming from the
fragmentation of the current jet in the final state. It is also shown how the
suggested factorization for $F_L$ is related to the corresponding one for $F_2$
in the same kinematic region.


title: Electromagnetic Fields in the QCD Vacuum

abstract:
  Quarks play an active role in shaping the QCD vacuum structure. Being dual
carriers of both `color' and `electric' charges they also respond to externally
applied electromagnetic fields. Thus, in principle, the vacuum of strong
interactions influences higher order QED processes such as photon-photon
scattering. We survey here the current status of the understanding of the
vacuum structure of strong interactions, and take a fresh look at its
electromagnetic properties.


title: Two-pion light-cone distribution amplitudes from the instanton vacuum

abstract:
  We calculate the two-pion light-cone distribution amplitudes in the effective
low-energy theory based on the instanton vacuum. These generalized distribution
amplitudes describe the soft (non-perturbative) part of the process
$\gamma^*\gamma \to \pi\pi$ in the region where the c.m. energy is much smaller
than the photon virtuality. They can also be used in the analysis of exclusive
processes such as $\gamma^* p \to p + 2\pi, 3\pi$ etc.


title: Dilepton and Photon Emission Rates from a Hadronic Gas III

abstract:
  We extend our early analyses of the dilepton and photon emission rates from a
hadronic gas to account for strange mesons using a density expansion. The
emission rates are reduced to vacuum correlation functions using three-flavor
chiral reduction formulas, and the latters are assessed in terms of empirical
data. Using a fire-ball, we compare our results to the low and intermediate
mass dilepton data available from CERN. Our results suggest that a baryon free
hadronic gas does not account for the excess of low mass dielectrons observed
at CERES but do well in accounting for the intermediate dimuons at HELIOS. The
same observations apply to the recent low and high $p_t$ dielectron rates from
CERES.


title: Testing neutrino magnetic moments with AGNs

abstract:
  We propose to test the magnetic transition moments of Majorana neutrinos by
comparing the fluxes of different flavours of neutrinos coming from active
galactic nuclei (AGN). We show that, with reasonable assumptions about the
magnetic field of the AGN, it is possible to obtain limits on
$\nu_{\tau}\nu_{e}$ and $\nu_{\tau}\nu_{\mu}$ transition moments which are
three to five orders of magnitude better than the laboratory limits. We also
point out that with certain parameter values the ratio
$\nu_{\tau}/\nu_{e,\mu}$, when measured from different sources, is expected to
vary from zero to values somewhat higher than one, providing an unambigious
signal of a magnetic transition within the AGN which cannot be explained by
neutrino oscillations.


title: $\Lambda_b \to \Lambda + D (\bar{D}^0)$ decays and CP-violation

abstract:
  It is shown that interference of the amplitudes for the decays $\Lambda_b \to
\Lambda D$ and $\Lambda_b \to \Lambda \bar{D}^0$ gives rise to CP-violation.


title: QCD coherence and jet rates in small x deep inelastic scattering

abstract:
  The contributions to the deep inelastic scattering structure function which
arise from emission of zero, one, two or three resolvable gluons and any number
of unresolvable ones are computed to order ${\bar \alpha}_{S}^{3}$. Coherence
effects are taken into account via angular ordering and are demonstrated to
yield (at the leading logarithm level) the identical results to those obtained
assuming the multi-Regge kinematics of BFKL.


title: From Notes to Chords in QCD

abstract:
  After a very brief overview recollecting the `classic' parts of QCD, that is
its application to describe hard processes and static properties of hadrons, I
survey recent work -- some very recent -- on QCD at non-zero temperature and
density. At finite temperature and zero density there is a compelling
theoretical framework allowing us to predict highly specific, non-trivial
dependence of the phase structure on the number of flavors and colors. Several
aspects have been rigorously, and successfully, tested against massive
numerical realizations of the microscopic theory. The theoretical description
of high density is nowhere near as mature, but some intriguing possibilities
have been put forward. The color/flavor locked state recently proposed for
three flavors has many remarkable features connected to its basic symmetry
structure, notably including chiral symmetry re-breaking and the existence
(unlike for two flavors) of a gauge invariant order parameter. I survey
potential applications to heavy ion collisions, astrophysics, and cosmology. A
noteworthy possibility is that stellar explosions are powered by release of QCD
latent heat.


title:
Asymmetry studies in Lambda 0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+
  production

abstract:
  We present a study on hyperon/anti-hyperon production asymmetries in the
framework of the recombination model. The production asymmetries for Lambda
0/Lambda 0-bar, Xi-/Xi+ and Omega-/Omega+ are studied as a function of x_F.
Predictions of the model are compared to preliminary data on
hyperon/anti-hyperon production asymmetries in 500 GeV/c pi- p interactions
from the Fermilab E791 experiment. The model predicts a growing asymmetry with
the number of valence quarks shared by the target and the produced hyperons in
the x_F < 0 region. In the positive x_F region, the model predicts constant
asymmetries for Lambda 0/Lambda 0-bar and Omega-/Omega+ production and a
growing asymmetry with x_F for Xi-/Xi+. We found a qualitatively good agreement
between the model predictions and data, showing that recombination is a
competitive mechanism in the hadronization process.


title: Gauge Kinetic Mixing and Leptophobic $Z'$ in $E_6$ and SO(10)

abstract:
  We examine the influence of gauge kinetic mixing on the couplings of a TeV
scale $Z'$ in both $E_6$ and SO(10) models. The strength of such mixing, which
arises due to the existence of incomplete matter representations at low scale,
can be described by a single parameter, $\delta$. The value of this parameter
can significantly influence the ability of both hadron and lepton colliders to
detect a $Z'$ using conventional search techniques. In addition, $\delta \neq
0$ also adds to the complexities involved in separating $E_6$ $Z'$ models from
those arising from alternative scenarios. Employing a reasonable set of
assumptions we have determined the allowed range for this parameter within a
wide class of models via an RGE analysis. In particular, given the requirements
of Standard Model gauge coupling unification, anomaly freedom and
perturbativity up to the GUT scale, we demonstrate that the necessary condition
for exact leptophobia in $\eta$ type $E_6$ models, $\delta=-1/3$, is impossible
to achieve in this scenario. Furthermore we show that the allowed range for
$\delta$ is rather restricted for arbitrary values of the mixing between the
$U(1)_\chi$ and $U(1)_\psi$ type couplings. The SO(10) $Z'$ model $\chi$ is
discussed as a separate case since it requires special attention.


title:
Dynamical determination of the unification scale by gauge-mediated
  supersymmetry breaking

abstract:
  We propose a mechanism for generating the GUT scale dynamically from the
Planck scale. The idea is that the GUT scale is fixed by the vacuum expectation
value of a "GUT modulus" field whose potential is exactly flat in the
supersymmetric limit. If supersymmetry is broken by gauge mediation, a
potential for the GUT modulus is generated at 2 loops, and slopes away from the
origin for a wide range of parameters. This potential is stabilized by
Planck-suppressed operators in the Kahler potential, and the GUT scale is fixed
to be of order M_* / (4\pi^2) (where M_* ~ 10^{18} GeV is the reduced Planck
scale) independently of the supersymmetry breaking scale. The cosmology of this
scenario is acceptable if there is an epoch of inflation with reheat
temperature small compared to the supersymmetry-breaking scale. We construct a
realistic GUT that realizes these ideas. The model is based on the gauge group
SU(6), and solves the doublet-triplet splitting problem by a sliding singlet
mechanism. The GUT sector contains no dimensionful couplings or tuned
parameters, and all mass scales other than the Planck scale are generated
dynamically. This model can be viewed as a realistic implementation of the
inverted hierarchy mechanism.


title:
Nuclear Corrections in Neutrino Deep Inelastic Scattering and the
  Extraction of the Strange Quark Distribution

abstract:
  Recent measurement of the structure function $F_2^\nu$ in neutrino deep
inelastic scattering allows us to compare structure function measured in
neutrino and charged lepton scattering for the first time with reasonable
precision. The comparison between neutrino and muon structure functions made by
the CCFR Collaboration indicates that there is a discrepancy between these
structure functions at small Bjorken x values. In this talk I examine two
effects which might account for the experimental discrepancy: nuclear shadowing
corrections for neutrinos and contributions from strange and anti strange
quarks.


title: Sterile Neutrinos in a Grand Unified Model

abstract:
  The recent experimental results indicating the neutrino oscillations may
strongly suggest that at least one more light neutrino species is required in
order to reconcile the existing data. In the simple GUT frameworks, this fact
seems difficult to preserve the parallelism between quarks and leptons. In this
letter, we investigate an SO(10) grand unified model with a pair of extra
generations in addition to the known three ones. Using the GUT relations, the
obtained neutrino mass matrix naturally indicates that one of the SU(2) singlet
(sterile) neutrino is very light and has large mixing with muon neutrino, which
can explain the atmospheric neutrino anomaly, and the hot dark matter neutrino
is also provided. The solar neutrino problem can be solved by the mixing with
muon neutrino consistently with quark mixing, namely, the Cabibbo angle.


title:
Probing anomalous top quark interactions at the Fermilab Tevatron
  Collider

abstract:
  We study the effects of dimension-six operators contributing to the $gt\bar
t$ vertex in top quark pair production at the Tevatron collider. We derive both
the limits from Run 1 data and the potential bounds from future runs (Run 2 and
3). Although the current constraints are not very strong, the future runs are
quite effective in probing these operators. We investigate the possibility of
disentangling different operators with the $t\bar t$ invariant mass
distribution and the top quark polarization asymmetry. We also study the
effects of a different set of operators contributing to single top production
via the $Wt\bar b$ coupling. We derive the current and potential future bounds
on these anomalous operators and find that the upgraded Tevatron can improve
the existing constraints from $R_b$ for one of the operators.


title: On the evaluation of sunset-type Feynman diagrams

abstract:
  We introduce an efficient configuration space technique which allows one to
compute a class of Feynman diagrams which generalize the scalar sunset topology
to any number of massive internal lines. General tensor vertex structures and
modifications of the propagators due to particle emission with vanishing
momenta can be included with only a little change of the basic technique
described for the scalar case. We discuss applications to the computation of
$n$-body phase space in $D$-dimensional space-time. Substantial simplifications
occur for odd space-time dimensions where the final results can be expressed in
closed form through rational functions. We present explicit analytical formulas
for three-dimensional space-time.


title:
Strongly first order electroweak phase transition induced by primordial
  hypermagnetic fields

abstract:
  We consider the effect of the presence of a hypermagnetic field at the
electroweak phase transition. Screening of the Z-component inside a bubble of
the broken phase delays the phase transition and makes it stronger first order.
We show that the sphaleron constraint can be evaded for m_H up to 100 GeV if a
B_Y\gsim 0.3 T^2 exists at the time of the EW phase transition, thus
resurrecting the possibility for baryogenesis within the minimal standard model
(provided enough CP violation can be obtained). We estimate that for m_H\gsim
100 GeV the Higgs condendsate behaves like a type II superconductor with
Z-vortices penetrating the bubble. Also, for such high Higgs masses the minimum
B_Y field required for a strong first order phase transition is large enough to
render the W-field unstable towards forming a condensate which changes the
simple picture of the symmetry breaking.


title: Dynamical Parton Distributions Revisited

abstract:
  Dynamical parton densities, generated radiatively from valence-like inputs at
some low resolution scale, are confronted with recent small-x data on deep
inelastic and other hard scattering processes. It is shown that within
theoretical uncertainties our previous (1994) dynamical/radiative parton
distributions are compatible with most recent data and still applicable within
the restricted accuracy margins of the presently available next-to-leading
order calculations. Due to recent high precision measurements we also present
an updated, more accurate, version of our (valence-like) dynamical input
distributions. Furthermore, our perturbatively stable parameter-free dynamical
predictions are extended to the extremely small-x region, 10^-8 ~< x ~< 10^-5,
relevant to questions concerning ultra-high-energy cosmic ray and neutrino
astronomy.


title:
Three-Family Perturbative String Vacua: Flat Directions and Effective
  Couplings

abstract:
  The properties of a class of quasi-realistic three-family perturbative
heterotic string vacua are addressed. String models in this class generically
contain an anomalous U(1), such that the nonzero Fayet-Iliopoulos term triggers
certain fields to acquire string scale VEV's along flat directions. This vacuum
shift reduces the rank of the gauge group and generates effective mass terms
and effective trilinear interactions. Techniques are discussed which yield a
systematic classification of the flat directions of a given string model which
can be proven to be F- flat to all orders. The effective superpotential along
such flat directions can then be calculated to all orders in the string (genus)
expansion.


title: DVCS at HERA

abstract:
  We demonstrate that perturbative QCD allows one to calculate the absolute
cross section of diffractive exclusive production of photons at large $Q^2$ at
HERA, while the aligned jet model allows one to estimate the cross section for
intermediate $Q^2 \sim 2 GeV^2$. Furthermore, we find that the imaginary part
of the amplitude for the production of real photons is larger than the
imaginary part of the corresponding DIS amplitude by a factor of about 2,
leading to predictions of a significant counting rate for the current
generation of experiments at HERA. We also find a large azimuthal angle
asymmetry in $ep$ scattering for HERA kinematics which allows one to directly
measure the real part of the DVCS amplitude and hence the nondiagonal parton
distributions.


title: Hadronic Interactions for High Energy Cosmic Ray Air Showers

abstract:
  Understanding hadronic interactions at high energies represents a very
important ingredient for modeling high energy cosmic ray air showers. In this
paper, we present a new approach to simulate hadronic interactions, including
hadron-hadron, hadron-nucleus, and nucleus-nucleus scattering, in the energy
range roughly between 10^11 and 10^17 eV. Such collisions are very complex,
being composed of many components, and therefore some strategy is needed to
construct a reliable model. The central point of our approach is the
hypothesis, that the behavior of high energy interactions is universal
(universality hypothesis). So, for example, the hadronization of partons in
nuclear interactions follows the same rules as the one in electron-positron
annihilation ; the radiation of off-shell partons in hadronic collisions is
based on the same principles as the one in deep inelastic scattering. We
construct a model for hadronic interactions in a modular fashion. The
individual modules, based on the universality hypothesis, are identified as
building blocks for more elementary interactions (like e^+ e^-, lepton-proton),
and can therefore be studied in a much simpler context. With these building
blocks under control, we can provide a quite reliable model for
nucleus-nucleus, hadron-nucleus and hadron-hadron scattering, providing in
particular very useful tests for the complicated numerical procedures using
Monte Carlo techniques.


title: Neutrino spin-flip effects in active galactic nuclei

abstract:
  We study the effects of neutrino spin-flip in the magnetic field, B_{AGN}, of
active galactic nuclei (AGN) for high-energy neutrinos (E > 10^{6} GeV)
originating from AGN induced by an interplay of the violation of equivalence
principle parameterized by $\Delta f$ and the twist in B_{AGN}. We point out
that a conversion effect may exist for $\Delta f \sim 10^{-34} (\delta
m^{2}/10^{-5} eV^{2})$ independent of gravity mixing angle. Observational
consequences for this conversion effect are discussed.


title: The Physical Spectrum of Conformal SU(N) Gauge Theories

abstract:
  We investigate the physical spectrum of vector-like SU(N) gauge theories with
infrared coupling close to but above the critical value for a conformal phase
transition. We use dispersion relations, the momentum dependence of the
dynamical fermion mass and resonance saturation. We show that the second
spectral function sum rule is substantially affected by the continuum
contribution, allowing for a reduction of the axial vector - vector mass
splitting with respect to QCD-like theories. In technicolor theories, this
feature can result in a small or even negative contribution to the electroweak
S parameter.


title:
Semihard Interactions in Nuclear Collisions Based on a Unified Approach
  to High Energy Scattering

abstract:
  Our ultimate goal is the construction of a model for interactions of two
nuclei in the energy range between several tens of GeV up to several TeV per
nucleon in the centre-of-mass system. Such nuclear collisions are very complex,
being composed of many components, and therefore some strategy is needed to
construct a reliable model. The central point of our approach is the
hypothesis, that the behavior of high energy interactions is universal
(universality hypothesis). So, for example, the hadronization of partons in
nuclear interactions follows the same rules as the one in electron-positron
annihilation; the radiation of off-shell partons in nuclear collisions is based
on the same principles as the one in deep inelastic scattering. We construct a
model for nuclear interactions in a modular fashion. The individual modules,
based on the universality hypothesis, are identified as building blocks for
more elementary interactions (like e^+ e^-, lepton-proton), and can therefore
be studied in a much simpler context. With these building blocks under control,
we can provide a quite reliable model for nucleus-nucleus scattering, providing
in particular very useful tests for the complicated numerical procedures using
Monte Carlo techniques.


title:
Supernova neutrino oscillations: Adiabaticity improvement by Majoron
  fields

abstract:
  If the lepton numbers are associated with global symmetries spontaneously
broken at a scale below 1 TeV, neutrino oscillations in supernovae produce
classic Majoron fields that perturb the neutrino propagation itself and may
change the oscillation patterns in the periods of largest $\nu $ fluxes. The
impact of the Majoron fields on the same transitions as $\nu_{e}\to \nu_{X}$
that presumably occur in the Sun is studied in the case of the non-adiabatic
MSW solution. It is shown how the back reaction of the Majoron fields may
improve the adiabaticity of these oscillations in a supernova environment which
has implications on the outgoing $\nu_{e}$ spectrum.


title: Lattice Determination of Heavy-Light Decay Constants

abstract:
  We report on the MILC collaboration's calculation of $f_B$, $f_{B_s}$, $f_D$,
$f_{D_s}$, and their ratios. Our central values come from the quenched
approximation, but the quenching error is estimated from $N_F=2$ dynamical
staggered lattices. We use Wilson light valence quarks and Wilson and static
heavy quarks. We find, for example, $f_B=157 \pm 11 {}^{+25}_{-9} {}^{+23}_{-0}
\MeV$, $f_{B_s}/f_B = 1.11 \pm 0.02 {}^{+0.04}_{-0.03} \pm 0.03$, $f_{D_s} =
210 \pm 9 {}^{+25}_{-9} {}^{+17}_{-1} \MeV$ and $f_{B}/f_{D_s} = 0.75 \pm 0.03
{}^{+0.04}_{-0.02} {}^{+0.08}_{-0.00}$, where the errors are statistical,
systematic (within the quenched approximation), and systematic (of quenching),
respectively.


title:
New Contributions to Neutralino Elastic Cross-sections from CP Violating
  Phases in the MSSM

abstract:
  We compute the four-Fermi neutralino-quark interaction Lagrangian including
contributions from the CP violating phases in the MSSM. We find that
neutralino-nucleus scattering cross-sections relevant for direct detection
experiments show a strong dependence on the value of the CP-violating phase
associated with the $\mu$ parameter, $\theta_\mu$. In some cases, for a broad
range of non-zero $\theta_\mu$, there are cancellations in the cross-sections
which reduce the cross-section by more than an order of magnitude. In other
cases, there may be enhancements as one varies $\theta_\mu$.


title: A model of anomalous production of strange baryons in nuclear collisions

abstract:
  We propose a simple model of production of strange baryons and antibaryons in
nuclear collisions at the CERN SPS. The model takes into account both the
increase of strangeness production in collisions of lighter ions and a
possibility of the formation of anomalous, strangeness rich matter in central
PbPb interactions. It is shown that ratios like $<\Omega>:<\Xi>:<\Lambda>$
depend strongly on the presence of anomalous matter and can be used to
determine its phenomenological parameters. In the model we assume that particle
composition of final state hadrons is essentially given by a rapid
recombination of quarks and antiquarks formed in tube-on-tube interactions of
incoming nucleons.


title:
Trace evaluation of matrix determinants and inversion of 4 $\times$ 4
  matrices in terms of Dirac covariants

abstract:
  In the following short paper we list some useful results concerning
determinants and inverses of matrices. First we show, how to calculate
determinants of $d \times d$ matrices, if their traces are known. As a next
step $4 \times 4$ matrices are expressed in terms of Dirac covariants. The
third step is the calculation of the corresponding inverse matrices in terms of
Dirac covariants.


title: Chiral symmetry and the pion gas virial expansion

abstract:
  In this work we study the thermodynamic properties of the pion gas starting
from the realistic elastic scattering phase-shifts obtained from Chiral
Perturbation Theory and using the virial expansion. In particular we study the
state equation and the behavior of the quark condensate as a function of the
temperature and the density.


title: Vacuum Birefringence in Strong Magnetic Fields

abstract:
  Table of Contents
  1. One-loop effective Lagrangian in spinor QED.
  2. Dispersion effects for low-frequency photons.
  3. Vacuum birefringence in magnetic fields.
  4. Light cone condition, effective Lagrangian approach.


title:
Pion electromagnetic formfactor in the space-like region and $P$-phase
  $\delta^1_1(s)$ of $\pi\pi$ scattering from the value of the modulus of
  formfactor in the time-like region.

abstract:
  The problem of determining the pion electromagnetic formfactor $F(q^2)$ in
the space-like region from the value of its modulus in the time-like region is
solved by the formfactor analyticity. If $F(q^2)$has no zeroes in the complex
plane then the formfactor in the space-like region is determined uniquely. If
$F(q^2)$has zeroes in the complex plane $q^2$ it can be obtained in the
space-like region within narrow limits using experimental data from the
time-like region. The formfactor phase $\phi(s)$ which coincides with the
$P$-wave phase $\delta^1_1(s)$ of the $\pi\pi$ scattering is calculated. The
value of the pion radius has been improved.


title: The perturbative proton form factor reexamined

abstract:
  We recalculate the proton Dirac form factor based on the perturbative QCD
factorization theorem which includes Sudakov suppression. The evolution scale
of the proton wave functions and the infrared cutoffs for the Sudakov
resummation are carefully chosen, such that the soft divergences from large
coupling constants are diminished and perturbative QCD predictions are
stablized. We find that the King-Sachrajda model for the proton wave function
leads to results which are in better agreement with experimental data compared
to the Chernyak-Zhitnitsky wave function.


title: Time-reversal-odd asymmetry in pion leptoproduction at HERMES

abstract:
  We estimate the size of the azimuthal asymmetry of the semi-inclusive pion
production in the deep-inelastic scattering of a polarized lepton beam off an
unpolarized nucleon target for the produced hadron, arising due to both
nonperturbative and perturbative effects.


title:
Van Alphen-de Haas effect for dense cold quark matter in a homogeneous
  magnetic field

abstract:
  We study the relativistic van Alphen--de Haas effect in cold dense quark
matter in a homogeneous magnetic field which arises from oscillations in the
effective potential of an underlying extended NJL-model. Finally, we discuss
the phase structure of the model in the parameter plane $(\mu,H)$ and the
solution of the mass gap equation.


title:
Induced symmetry breaking and a new phase of hadronic matter at high
  density

abstract:
  The notion induced symmetry breaking (ISB) is introduced as a generalization
of the spontaneous symmetry breaking mechanism and is illustrated in a simple
two flavor spin model. In the case of QCD at finite baryon density, I argue
that the quark interaction induced by zero sound satisfies the prerequisites
which are necessary for a ISB scenario. In this scenario, the quark condensate
sharply drops at the critical value of the chemical potential in coincidence
with a rapid increase of the baryon density. The spectrum of the light
particles is discussed below and above this phase transition. The consequences
of the ISB mechanism for heavy ion collisions are briefly addressed.


title:
How Isospin Violation Mocks ``New'' Physics: $\pi^0-\eta,\eta'$ Mixing
  in $B\to \pi\pi$ Decays

abstract:
  An isospin analysis of $B\to\pi\pi$ decays yields $\sin 2\alpha$, where
$\alpha$ is the usual CKM angle $\alpha\equiv arg [-V_{td}V_{tb}^\ast
/(V_{ud}V_{ub}^\ast)]$, without hadronic uncertainty if isospin is a perfect
symmetry. Isospin, however, is broken not only by electroweak effects but also
by the u and d quark mass difference. The latter generates $\pi^0-\eta, \eta'$
mixing and converts the isospin-perfect triangle relation between the
$B\to\pi\pi$ amplitudes to a quadrilateral. The combined isospin-violating
effects impact the extracted value of $\sin 2\alpha$ in a significant manner,
particularly if the latter is small.


title: Quarkonium Production through Hard Comover Scattering

abstract:
  We propose a qualitatively new mechanism for quarkonium production, motivated
by the global features of the experimental data and by the successes/failures
of existing models. In QCD, heavy quarks are created in conjunction with a
bremsstrahlung color field emitted by the colliding partons. We study the
effects of perturbative gluon exchange between the quark pair and a comoving
color field. Such scattering can flip the spin and color of the quarks to
create a non-vanishing overlap with the wave function of physical quarkonium.
Several observed features that are difficult to understand in current models
find simple explanations. Transverse gluon exchange produces unpolarized
J/psi's, the chi_c1 and chi_c2 states are produced at similar rates, and the
anomalous dependence of the J/psi cross section on the nuclear target size can
be qualitatively understood.


title:
Ambiguities in the zero momentum limit of the thermal
  $\pi^o\gamma\gamma$ triangle diagram

abstract:
  Modifications of the $\pi^o\to 2\gamma$ decay amplitude by thermal effects
have already been considered by several authors, leading to quite different
results. I consider in this paper the triangle diagram connecting a neutral
pion to two photons in a constituent quark model, within the real-time
formulation of thermal field theory and study the zero external momentum limit
of this diagram. It appears that this limit is not unique and depends strongly
on the kinematical configuration of the external particles. This non-uniqueness
is shown to explain the contradiction between existing results. I end with some
considerations suggesting that this decay amplitude may be significantly
modified by the resummation of hard thermal loops, due to infrared
singularities.


title: The Fayet-Iliopoulos term in Type-I string theory and M-theory

abstract:
  The magnitude of the Fayet-Iliopoulos term is calculated for
compactifications of Type-I string theory and Horava-Witten M-theory in which
there exists a pseudo-anomalous U(1)_X. Contrary to various conjectures, it is
found that in leading order in the perturbative expansion around the
weakly-coupled M-theory or Type-I limits, a result identical to that of the
weakly-coupled E_8xE_8 heterotic string is obtained. The result is independent
of the values chosen for the Type-I string scale or the size of the M-theory
11th dimension, only depending upon Newton's constant and the unified gauge
coupling.


title:
Effect of random magnetic field on active-sterile neutrino conversion in
  the supernova core

abstract:
  The active-sterile neutrino conversion is studied for neutrino propagating in
the axial potential generated by magnetised electron plasma in the supernova
medium. We consider the effect of random magnetic field $B_{rms}$ on the
average neutrino conversion probability. We obtained the constraint on $\Delta
m^2$ and $\sin^2 2\theta$ for different strength of the random magnetic fields,
by considering the positive definiteness of the average neutrino conversion
probability inside the supernova core. Our calculation shows that, $B_{rms}\le
0.63\times 10^{14}$ Gauss is preferable so that small values of $\Delta m^2$
can not be excluded.


title: Lepton Fluxes from Atmospheric Charm

abstract:
  We reexamine the charm contribution to atmospheric lepton fluxes in the
context of perturbative QCD. We include next-to-leading order corrections and
discuss theoretical uncertainties due to the extrapolations of the gluon
distributions at small-x. We show that the charm contribution to the
atmospheric muon flux becomes dominant over the conventional contribution from
pion and kaon decays at energies of about 10^5 GeV. We compare our fluxes with
previous calculations.


title: New results on heavy quarks near threshold

abstract:
  We review in brief the threshold expansion, a method to perform the expansion
of Feynman integrals near the heavy quark-antiquark threshold, and its relation
to the construction of two effective theories, non-relativistic QCD (NRQCD) and
potential-NRQCD. We then summarize recent next-to-next-to-leading order results
on the decay $J/\Psi\to l^+ l^-$, the bottom quark mass from $\Upsilon$ sum
rules and the top-anti-top production cross section near threshold in $e^+ e^-$
collisions.


title:
Fermion Masses and Gauge Mediated Supersymmetry Breaking from a Single
  U(1)

abstract:
  We present a supersymmetric model of flavor. A single U(1) gauge group is
responsible for both generating the flavor spectrum and communicating
supersymmetry breaking to the visible sector. The problem of Flavor Changing
Neutral Currents is overcome, in part using an `Effective Supersymmetry'
spectrum among the squarks, with the first two generations very heavy. All
masses are generated dynamically and the theory is completely renormalizable.
The model contains a simple Froggatt-Nielsen sector and communicates
supersymmetry breaking via gauge mediation without requiring a separate
messenger sector. By forcing the theory to be consistent with SU(5) Grand
Unification, the model predicts a large tan beta and a massless up quark. While
respecting the experimental bounds on CP violation in the K-system, the model
leads to a large enhancement of CP violation in B-(B bar) mixing as well as in
B decay amplitudes.


title:
Symmetry conserving approach to the quantization of the non-topological
  SU(3) soliton

abstract:
  We reconsider canonical quantization of the rotating soliton in the SU(3)
Chiral Quark-Soliton Model. We show that at the level of 1/N_c, in contrast to
the SU(2) version of the model, there appear terms which spoil the commutation
rules of the flavor generators. Terms of similar origin are also present in the
expressions for axial couplings and magnetic moments. We investigate the small
soliton limit of the model, and require that the results for the physical
observables reduce to the ones of the non-relativistic quark model. This
procedure allows to identify the troublesome terms. Next, we introduce a
symmetry conserving approach by subtracting these terms and discuss numerical
predictions obtained that way.


title: Vegas Revisited: Adaptive Monte Carlo Integration Beyond Factorization

abstract:
  We present a new adaptive Monte Carlo integration algorithm for ill-behaved
integrands with non-factorizable singularities. The algorithm combines Vegas
with multi channel sampling and performs significantly better than Vegas for a
large class of integrals appearing in physics.


title: Detecting supersymmetric Q-balls with neutron stars

abstract:
  Supersymmetric Q-balls trapped in neutron stars or white dwarfs may cause the
stars to explode. Trapping of Q-balls in neutron stars is shown to be less
likely, but trapping in neutron star progenitors more likely than hitherto
assumed, making neutron stars very sensitive Q-ball "detectors". White dwarfs
only trap potentially dangerous Q-balls in a narrow parameter range.


title: Evolution equations for high parton density QCD

abstract:
  This talk is given at "Continious Advances in QCD", Minnesota, April
16-19,1998. It is a brief report on our results in high parton density QCD. The
main goal of this talk is to discuss the new evolution equation which was
obtained and solved by A.Ayala, M. Ducati and E.Levin and by E. Gotsman, E.
Levin and U. Maor, and to share with you the physics can be recovered by this
equation.


title: Bose-Einstein condensation and independent production of pions

abstract:
  The influence of the HBT effect on the momentum spectra of independently
produced pions is studied using the method developed earlier for discussion of
multiplicity distributions. It is shown that in this case all the spectra and
multiparticle correlation functions are expressible in terms of one function of
two momenta. It is also shown that at the critical point all pions are
attracted into one quantum state and thus form a Bose-Einstein condensate.


title: The one-loop functional as a Berezinian

abstract:
  We employ notions familiar from supersymmetry for constructing the one-loop
functional of general quantum field theories with bosons and fermions (spin <
1). To demonstrate the advantages of such an approach for calculating one-loop
divergences, we analyse a simple Yukawa theory with two different versions of a
super-heat-kernel expansion. These methods also simplify the calculation of
one-loop divergences for non-renormalizable meson--baryon Lagrangians occurring
in chiral perturbation theory.


title:
JetViP 1.1: Calculating One- and Two-Jet Cross Sections with Virtual
  Photons in NLO QCD

abstract:
  JetViP is a computer program for the calculation of inclusive single- and
dijet cross sections in eP- and e-gamma-scattering in NLO QCD. The virtuality
of the photon, radiated by the incoming electron, can be chosen in a continuous
range, reaching from photoproduction into deep inelastic scattering. The
various contributions to the full jet cross section, including the resolved
photon contributions, are implemented. The calculation is based on the
phase-space-slicing method.


title: Long range forces induced by neutrinos at finite temperature

abstract:
  We revisit and extend previous work on neutrino mediated long range forces in
a backround at finite temperature. For Dirac neutrinos, we correct existing
results. We also give new results concerning spin-dependent as well as
spin-independent long range forces associated to Majorana neutrinos. An
interesting outcome of the investigation is that, for both types of neutrinos
whether massless or not, the effect of the relic neutrino heat bath is to
convert those forces into attractive ones in the supra-millimeter scale while
they stay repulsive within the sub-millimeter scale.


title:
Small-x behaviour of the polarized structure function
  $F_3^{\gamma}(x,Q^2)$

abstract:
  We study the small-$x$ behaviour of the polarized photon structure function
$F_3^{\ga}$, measuring the gluon transversity distribution, in the leading
logarithmic approximation of perturbative QCD. There are two contributions,
both arising from two-gluon exchange. The leading contribution to small-$x$ is
related to the BFKL pomeron and behaves like $x^{-1-\om_2}$, $\om_2 = {\cal
O}(\al_S)$. The other contribution includes in particular the ones summed by
the DGLAP equation and behaves like $x^{1-\om_0^{(+)}}$, $\om_0^{(+)} = {\cal
O}(\sqrt{\al_S})$.


title: Atmospheric and Solar Neutrinos with a Heavy Singlet

abstract:
  We follow a minimalistic approach to neutrino masses, by introducing a single
heavy singlet $N$ into the standard model (or supersymmetric standard model)
with a heavy Majorana mass $M$, which couples as a single right-handed neutrino
in a Dirac fashion to leptons, and induces a single light see-saw mass
$m_{\nu}\sim 5\times 10^{-2} eV$, leaving two neutrinos massless. This trivial
extension to the standard model may account for the atomospheric neutrino data
via $\nu_{\mu}\to \nu_{\tau}$ oscillations with near maximal mixing angle
$\theta_{23}\sim \pi/4$ and $\Delta m_{\mu \tau}^2 \sim 2.5\times 10^{-3}
eV^2$. In order to account for the solar neutrino data the model is extended to
SUSY GUT/ string-inspired type models which can naturally yield an additional
light tau neutrino mass $m_{\nu_{\tau}}\sim few \times 10^{-3} eV$ leading to
$\nu_{e L}\to (\cos \theta_{23}{\nu}_{\mu L} -\sin \theta_{23}{\nu}_{\tau L})$
oscillations with $\Delta m_{e1}^2\sim 10^{-5} eV^2$ and a mixing angle $\sin^2
2 \theta_1 \approx 10^{-2}$ in the correct range for the small angle MSW
solution to the solar neutrino problem. The model predicts $\nu_{e L}\to (\sin
\theta_{23}{\nu}_{\mu L} +\cos \theta_{23}{\nu}_{\tau L})$ oscillations with a
similar angle but a larger splitting $\Delta m_{e2}^2 \sim 2.5\times 10^{-3}
eV^2 $.


title:
Neutrino degeneracy effect on neutrino oscillations and primordial
  helium yield

abstract:
  In this work we present the results of our numerical analysis of the effect
of lepton asymmetries L on neutrino oscillations and consequently on helium
production in a model of cosmological nucleosynthesis with active-sterile
neutrino oscillations. We performed detail calculations of the neutron-proton
ratio till its freezing and the subsequent synthesis of helium-4 for a wide
range of values of the initial lepton asymmetry 10^{-4}-10^{-10} and for the
complete set of mixing parameters of the oscillation model described in
hep-ph/9707282: \delta m^2 \le 10^{-7} eV^2 and any \vartheta.
  We have found that there are significant modifications of neutrino number
densities and energy distributions over a large range of values of the initial
asymmetry. Hence, the previously derived (for the case of lepton asymmetry of
the order of the baryon one) nucleosynthesis limits on the oscillation
parameters are considerably altered. We have calculated the dependence of
primordially produced helium-4 on the parameters of the model Y_p(L, \delta
m^2, \vartheta). From the isohelium contours in the \delta m^2-\vartheta plane,
we have obtained limits on the neutrino mixing parameters corresponding to
nucleosynthesis with degenerate neutrinos. An intriguing new result of our
analysis is that the lepton asymmetry is able to tighten the nucleosynthesis
bounds on neutrino mixing parameters, besides its well known ability to relax
them.


title:
A Two Parameter Four Neutrino Mixing Model with an Exchange Symmetry of
  the Mass Doublet Neutrinos

abstract:
  In a model with four neutrino mass eigenstates grouping in two narrow
doublets the condition of maximal mixing of the doublet neutrino components
leads to a simple four-neutrino mixing matrix which is related to two connected
effective two-neutrino mixing patterns. As a result, large values of the
neutrino oscillation amplitudes for both the solar and atmospheric neutrino
anomalies appear quite naturally if the LSND data are accepted.


title:
Gluino Contribution to the 3-loop Quark Mass Anomalous Dimension in the
  Minimal Supersymmetric Standard Model

abstract:
  We deduce the gluino contribution to the three-loop QCD quark mass anomalous
dimension function within the minimal supersymmetric Standard Model (MSSM) from
its standard QCD expression. This work is a continuation of the program of
computation of MSSM renormalization group functions.


title: Phenomenological prediction of the properties of the B_{C} system

abstract:
  We present a comprehensive calculation of the energies, splittings and
electromagnetic decay rates of the bottom charmed meson system. Our calculated
result for the ground state lifetime is 0.38 \pm 0.03 ps, in good agreement
with the recent CDF measurement. In order to incorporate running coupling
constant effects, we choose Richardson's potential for the central potential
and take the spin-dependent potentials from the radiative one-loop expressions
of Pantaleone, Tye and Ng. The effects of a nonperturbative spin-orbit
potential are also included. Our parameters are determined from the low-lying
levels of the upsilon system (avg. dev. of 4.3 MeV) and charmonium (avg. dev.
of 19.9 MeV). We carry out detailed comparison with the earlier work of Eichten
and Quigg and lattice calculations. Our predicted result for the ground state
energy is 6286_{-6}^{+15} MeV. Our results are generally in agreement with the
earlier calculations. However, we find the two lowest 1^{+} states to be very
close to the j-j limit, in agreement with the NRQCD lattice calculations, but
at odds with many of the earlier phenomenological calculations. The
implications of this finding for the photon spectra of the 1P and 2S states are
discussed in some detail. Some strategies for the observation of these states
are discussed, and a table of their cascades to the ground state are presented.


title: Commensurate Scale Relations and the Abelian Correspondence Principle

abstract:
  Commensurate scale relations are perturbative QCD predictions which relate
observable to observable at fixed relative scales, independent of the choice of
intermediate renormalization scheme or other theoretical conventions. A
prominent example is the "generalized Crewther relation" which connects the
Bjorken and Gross-Llewellyn Smith deep inelastic scattering sum rules to
measurements of the $e^+ e^-$ annihilation cross section. Commensurate scale
relations also provide an extension of the standard minimal subtraction scheme
which is analytic in the quark masses, has non-ambiguous scale-setting
properties, and inherits the physical properties of the effective charge
$\alpha_V(Q^2)$ defined from the heavy quark potential. I also discuss a
property of perturbation theory, the "Abelian correspondence principle", which
provides an analytic constraint on non-Abelian gauge theory for $N_C \to 0.$


title: Chiral Symmetry Breaking in 2+1 dimensions due to Sphalerons

abstract:
  In 2+1 dimensional gauge thories with $SU(N_c)$ color and $2N_f$ flavors of
quarks in the fundamental representation, sphalerons, if present may lead to
quark condensation and chiral symmetry breaking. The effect is similar to
instanton induced chiral symmetry breaking in 3+1 dimensions and is due to the
interaction of quark propagators with sphalerons. The existence of sphalerons
requires that color symmetries be broken by a Higgs in the fundamental
representation. We show that the sphaleron effect may persist for arbitrarily
large $N_f$ but vanishes along with the mass of the gauge fields corresponding
to broken generators of $SU(N_c)$. The effect is inherently non-Abelian and
absent for QED.


title: Master Formulae Approach to Photon Fusion Reactions

abstract:
  We analyze the $\gamma\gamma\to \pi\pi, KK, \eta\eta, \pi\eta$ reactions
through $\sqrt{s}=2$ GeV, using the master formula approach to QCD with three
flavors. In this approach, the constraints of broken chiral symmetry, unitarity
and crossing symmetry are manifest in all channels. The pertinent vacuum
correlators are analyzed at tree level using straightforward resonance
saturation methods. A one-loop chiral power counting analysis at treshold is
also carried out and compared to standard chiral perturbation theory. Our
results are in overall agreement with the existing data in all channels. We
predict the strange meson polarizabilities and a very small cross section for
$\gamma\gamma\to\eta\eta$.


title:
Nonperturbative O(m_c^{-2}) Effects in B-> X_s photon from Heavy Quark
  Effective Theory

abstract:
  The nonperturbative contribution, suppressed by powers of the charm quark
mass m_c, in the inclusive decay B -> X_s photon is analyzed in the context of
heavy quark effective field theory (HQEFT). According to previous analyses, the
leading effects of O(1/m_c^2) arise from an external gluon attached to a charm
quark loop and can be expressed in terms of the chromomagnetic interaction of
the b quark inside the B meson. This is also true at leading order in the HQEFT
approach. However the structure of higher-dimensional operators is different
because the effects of external gluons alone do not give a complete set of
operators. A systematic method to derive all the high-dimensional operators can
be obtained in the HQEFT scheme using the operator product expansion.


title: BFKL gluon dynamics in the $p_T(D^*)$ spectra at HERA

abstract:
  In the framework of semihard QCD approach, with the emphasis on the BFKL
evolution of gluon distributions, we calculate the differential cross sections
of inclusive $D^{*\pm}$ mesons electroproduction at HERA and confront our
results with available
  ZEUS experimental data.


title:
Comment on ``Searching for Evolutions of Pure States into Mixed States
  in the Two-State System K-K''

abstract:
  It has been recently proposed to study generic dynamical evolutions of the
neutral kaon system that go beyond quantum mechanics. We explicitly show that,
unless the condition of complete positivity is enforced, those dynamics are
physically inconsistent and should be rejected.


title:
Techniques for one-loop calculations in constrained differential
  renormalization

abstract:
  We describe in detail the constrained procedure of differential
renormalization and develop the techniques required for one-loop calculations.
As an illustration we renormalize Scalar QED and show that the two-, three- and
four-point Ward identities are automatically satisfied.


title:
PQCD Analysis of Inclusive Semileptonic Decays of A Polarized Lambda_b
  Baryon

abstract:
  We investigate the Lambda_b polarization problem in the inclusive
semileptonic decays of a polarized Lambda_b baryon, using the modified
perturbative QCD formalism which includes Sudakov suppression. According to
HQEFT, we show that, at the leading order in the 1/M_b expansion, the polarized
and unpolarized distribution functions become one single universal distribution
function. To explore the mechanisms which determine the spin properties of a
polarized Lambda_b baryon, we construct four formalisms which are the naive
quark model (QM), the modified quark model (MQM), the naive parton model (PM)
and the modified parton model (MPM), and calculate their corresponding Lambda_b
polarizations, denoted as P's. The modified quark and parton models are with
Sudakov suppression. The resulting P's are -0.23 (QM), -0.94 (MQM), -0.37 (PM)
and -0.68 (MPM), respectively. We note that P_MQM (equal to -0.94) is very
close the b quark polarization asymmetry, A_RL=-0.94, calculated at the Z
vertex in Z -> b bar{b} process, and that P_MPM (equal to -0.68) is also very
close to the Lambda_b polarization (equal to -0.68) which was estimated from
the fragmentation processes under the heavy quark limit. Based on our analysis,
there exists no any paradox in the theoretical explanations of the Lambda_b
polarization for the experimental data.


title: A Consistent Calculation of Bubble-Nucleation Rates

abstract:
  We present a consistent picture of tunnelling in field theory. Our results
apply both to high-temperature field theories in four dimensions and to
zero-temperature three-dimensional ones. Our approach is based on the notion of
a coarse-grained potential U_k that incorporates the effect of fluctuations
with characteristic momenta above a given scale k. U_k is non-convex and
becomes equal to the convex effective potential for k --> 0. We demonstrate
that a consistent calculation of the nucleation rate must be performed at
non-zero values of k, larger than the typical scale of the saddle-point
configuration that dominates tunnelling. The nucleation rate is exponentially
suppressed by the action S_k of this saddle point. The pre-exponential factor
A_k, which includes the fluctuation determinant around the saddle-point
configuration, is well-defined and finite. Both S_k and A_k are k-dependent,
but this dependence cancels in the expression for the nucleation rate. This
picture breaks down in the limit of very weakly first-order phase transitions,
for which the pre-exponential factor compensates the exponential suppression.

categories: hep-ph cond-mat.stat-mech hep-lat hep-th


title: An electroweak model without Higgs particle

abstract:
  In this paper, applying general gauge field theory, we will construct an
electroweak model. In this new electroweak model, Higgs mechanism is not used,
so no Higgs particle exists in the model. In order to keep the masses of
intermediate gauge bosons non-zero, we will introduce two sets of gauge fields.
We need a vacuum potential to introduce symmetry breaking and to introduce the
masses of all fields. Except for theose terms concern of Higgs particle, the
fundamental dynamical properties of this model are similar to those of the
standard model. And in a proper limit, this model will approximately return to
the standard model.


title: Colour-Octet Effects in Radiative $\Upsilon$ Decays

abstract:
  We investigate the effects of colour-octet contributions to the radiative
$\Upsilon$ decay within the Bodwin, Braaten and Lepage NRQCD factorization
framework. Photons coming both from the coupling to hard processes (`direct')
and by collinear emission from light quarks (`fragmentation') are consistently
included at next-to-leading order (NLO) in $\alpha_s$. An estimate for the
non-perturbative matrix elements which enter in the final result is then
obtained. By comparing the NRQCD prediction at NLO for total decay rates with
the experimental data, it is found that the non-perturbative parameters must be
smaller than expected from the na\"\i ve scaling rules of NRQCD. Nevertheless,
colour-octet contributions to the shape of the photon spectrum turn out to be
significant.


title: Diffraction in Charged Current DIS

abstract:
  We present the QCD calculation of the diffractive structure function for
charged current DIS. In particular we analyse the perturbatively tractable
excitation of heavy quarks. We emphasize the peculiarities of the Regge
factorization breaking in excitation of open charm.


title: Parton distributions, d/u and higher twists at high x

abstract:
  We extract the ratio of the down (d) and up (u) parton distribution functions
(PDF's) from the ratio of deuteron and proton structure function F_2(d)/F_2(p)
measured by NMC. We use corrections for nuclear binding effects in the
deuteron, which are extracted from the nuclear dependence of SLAC F_2 data.
Significant corrections to the d quark distribution in standard PDF's are
required, especially at high x. The corrected d/u ratio is in agreement with
the QCD prediction of 0.2 at x=1. The predictions for the W asymmetry in hadron
colliders using PDF's with the corrected d/u ratio are in much better agreement
with recent CDF data at large rapidity. Using the updated d/u ratio and the
most recent world average for alpha_s, we perform a NLO global fit to all DIS
data for F_2 and R, and estimate the size of the higher twist contributions
using both a renormalon model and an empirical model. We find that with the
updated value of alpha_s, the magnitude of the higher twist terms is half the
value of previous analysis. With the inclusion of target mass and higher twist
corrections, the standard NLO PDF's with the updated d/u ratio describe the
SLAC F_2 data up to x=1.0. When the analysis is repeated in NNLO, we find that
the additional NNLO contributions to R account for most of the higher twist
effects extracted in the NLO fit. The analysis in NNLO indicates that the
higher twist effects in R, F_2 and xF_3 (e.g. GLS sum rule) are very small.


title: Parton distributions at high x

abstract:
  We extract the ratio of the down (d) and up (u) parton distribution functions
(PDF's) from the ratio of NMC deuteron and proton structure function
F_2(d)/F_2(p), using corrections for nuclear binding effects in the deuteron,
which are extracted from the nuclear dependence of SLAC F_2 data. Significant
corrections to the d quark distribution in standard PDF's are required,
especially at high x. The corrected d/u ratio is in agreement with the QCD
prediction of 0.2 at x=1. The predictions for the recent CDF W asymmetry data
using PDF's with the corrected d/u ratio give much better agreement at large
rapidity. Using the updated d/u ratio and the most recent world average for
alpha_s, we perform a NLO global fit to all DIS data for F_2 and R, and
estimate the size of the higher twist contributions using both a renormalon
model and an empirical model. We find that with the updated value of alpha_s,
the magnitude of the higher twist terms is half the value of previous analysis.
With the inclusion of target mass and higher twist corrections, the standard
NLO PDF's with the updated d/u ratio describe the SLAC F_2 data up to x=1.0.
When the analysis is repeated in NNLO, we find that the additional NNLO
contributions to R account for most of the higher twist effects extracted in
the NLO fit. The analysis in NNLO indicates that the higher twist effects in R,
F_2 and xF_3 (e.g. GLS sum rule) are very small.


title:
Effect of residual Bose-Einstein correlations on the Dalitz plot of
  hadronic charm meson decay

abstract:
  We show that the presence of residual Bose-Einstein correlations may affect
the resonant contribution of hadronic charm decays where two identical pions
appear in the final state. The distortion of the phase space of the reaction
would be visible in the dalitz plot. The decay D+ --> K- pi+ pi+ is discussed
but results can be generalized to any decay with identical bosons.


title:
Meson-Meson and Meson-Baryon Interactions in a chiral Non-perturbative
  Approach

abstract:
  A qualitative account of the meson-meson and meson-baryon interactions using
chiral Lagrangians and the inverse amplitude method in coupled channels is
done. The method, imposing exact unitarity, proves to be very useful tool to
extend the information contained in the chiral Lagrangians at energies beyond
the realm of applicability of chiral perturbation theory.


title: Spectrum of Cosmological Perturbations from Multiple-Stage Inflation

abstract:
  Within the context of supersymmetric hybrid inflation, we study a
multiple-stage inflationary scenario that can generate a primordial spectrum of
adiabatic density perturbations with a break at $k_b \simeq 0.05 h Mpc^{-1}$.
The presence of such a break is supported by the APM galaxy survey data. We
consider a specific model within this scenario and confront it with
observational data. We reproduce the angular power spectrum of CMB
anisotropies, and also account for the break in the power spectrum of galaxy
clustering. In addition, we find a value for $\sigma_8$ in agreement with the
one deduced from observations. A characteristic property of the spectrum is a
drop of the spectral index from $n \simeq 1$ to $n \sim 0.6$ at $k \sim k_b$.


title: Can the QCD running coupling have a causal analyticity structure?

abstract:
  Solving the QCD renormalization group equation at the 2-loop and 3-loop
orders we obtain explicit expressions for the coupling as a function of the
scale in terms of the Lambert W function. We study the nature of the ``Landau
singularities'' in the complex Q^2 plane and show that perturbative freezing
can lead, in certain cases, to an analyticity structure that is consistent with
causality. We analyze the Analytic Perturbation Theory (APT) approach which is
intended to remove the ``Landau singularities'', and show that at 2-loops it is
uniquely defined in terms of the Lambert W function, and that, depending on the
value of the first two beta function coefficients beta_0 and beta_1, it is
either consistent with perturbative freezing (for beta_1 < -beta_0^2) with an
infrared limit of -beta_0/beta_1 or leads to a non-perturbative infrared
coupling with a limit of 1/beta_0 (for beta_1 > -beta_0^2). The possibility of
a causal perturbative coupling is in accordance with the idea that a purely
perturbative Banks-Zaks phase with an infrared fixed-point exists in QCD if the
number of flavours (N_f) is increased. The causality condition implies that the
perturbative phase is realized for N_f \geq 10.


title: Meson electromagnetic form factors in a relativistic quark model

abstract:
  The main assumption of the model is that in soft processes mesons behave like
systems made of valence quarks and an effective vacuum- like field. The
4-momentum of the latter represents the relativistic generalization of the
potential energy. The electromagnetic form factors are expressed in terms of
the overlap integral of the initial and final wave functions written under the
form of Lorentz covariant distribution of quark momenta. The calculation is
fully Lorentz covariant and the form factors of the charged mesons are
normalized to unity at t=0.


title:
Gluon Polarization in e^+e^- -> t \bar t G: Polar Angle Dependence and
  Beam Polarization Effects

abstract:
  We calculate the linear and circular polarization of gluons produced in
conjunction with massive quarks in the annihilation process $e^+e^-\to q \bar q
G$. The linear polarization is calculated in the hadron event plane as well as
in the gluon-beam plane. Beam polarization and polar orientation effects are
included in our discussion. For typical top pair production energies at the
Next-Linear-Collider (NLC) the degree of linear polarization in the hadron
event plane remains close to its soft gluon value of 100% over most of the
energy spectrum of the gluon. The linear polarization in the gluon-beam plane
is generally smaller but peaks toward the hard end of the gluon spectrum. The
dependence of the linear polarization on beam polarization and on the polar
orientation of the gluon is small. The circular polarization is largest for
maximal gluon energies and shows a strong dependence on the longitudinal beam
polarization. The longitudinal polarization of the beam may therefore be used
to tune the circular polarization of the gluon. The massive quark results are
compared with the corresponding results for the massless quark case.


title: Anomalous Couplings in W Pair Production

abstract:
  I present a short overview over W pair production and studies of angular
differential cross-sections with and without initial state radiation applying
semi-analytical methods and using the Fortran program GENTLE. The influence of
anomalous couplings to this process is also discussed.


title:
The Solar Neutrino Problem and Solar Neutrino Oscillations in Vacuum and
  in Matter

abstract:
  The solar neutrino problem is reviewed and the possible vacuum oscillation
and MSW solutions of the problem are considered.


title:
Resummation of Threshold Corrections for Single-Particle Inclusive Cross
  Sections

abstract:
  We derive threshold resummations for single-particle and single-jet inclusive
cross sections, thus generalizing previous results at fixed invariant mass to a
wider class of cross sections with phenomenological interest. We confirm the
structure of our resummed expressions by comparison with explicit one-loop
calculations for direct photons and heavy quarks.


title:
Taming the Penguin in the B0(t) -> Pi+Pi- CP-asymmetry: Observables and
  Minimal Theoretical Input

abstract:
  Penguin contributions, being not negligible in general, can hide the
information on the CKM angle alpha coming from the measurement of the
time-dependent B0(t) -> pi+pi- CP-asymmetry. Nevertheless, we show that this
information can be summarized in a set of simple equations, expressing alpha as
a multi-valued function of a single theoretically unknown parameter, which
conveniently can be chosen as a well-defined ratio of penguin to tree
amplitudes. Using these exact analytic expressions, free of any assumption
besides the Standard Model, and some reasonable hypotheses to constrain the
modulus of the penguin amplitude, we derive several new upper bounds on the
penguin-induced shift |2alpha-2alpha_eff|, generalizing the recent result of
Grossman and Quinn. These bounds depend on the averaged branching ratios of
some decays (pi0pi0, K0K0bar, K+-pi-+) particularly sensitive to the penguin.
On the other hand, with further and less conservative approximations, we show
that the knowledge of the B+- -> Kpi+- branching ratio alone gives sufficient
information to extract the free parameter without the need of other
measurements, and without knowing |V_td| or |V_ub|. More generally, knowing the
modulus of the penguin amplitude with an accuracy of ~30% might result in an
extraction of alpha competitive with the experimentally more difficult isospin
analysis. We also show that our framework allows to recover most of the
previous approaches in a transparent and simple way, and in some cases to
improve them. In addition we discuss in detail the problem of the various kinds
of discrete ambiguities.


title: Cosmic Strings - Dead Again?

abstract:
  I report on recent numerical simulations of the simplest field theory with
cosmic string solutions, the Abelian Higgs model. We find that random networks
of string quickly converge to a scaling solution in which the network scale
length $\xi$ increases linearly with time. There are very few loops with sizes
less than $\xi$, and the strings are smooth, showing no signs of ``small scale
structure''. We claim that particle production is the dominant energy-loss
mechanism, not gravitational radiation as previously thought. For strings in
Grand Unified Models, stringent constraints can be placed from cosmic ray
observations on the string tension $\mu$: we estimate $G\mu < 10^{-9}$, three
orders of magnitude lower than the constraint from Cosmic Microwave Background
fluctuations.


title: Comment on ``Indirect CP violation in the B-system''

abstract:
  In a recent paper, Banuls and Bernabeu have claimed the existence of a new
form of indirect CP violation which would have its most prominent manifestation
in the $B_d$-$\bar B_d$ system. I analyse this claim in detail. I emphasize the
fact that it is necessary to take into account the precise experimental method
if one is to identify correctly the weak phase that one is about to measure.


title: Weak Hamiltonian, CP Violation and Rare Decays

abstract:
  These lectures describe in detail the effective Hamiltonians for weak decays
of mesons constructed by means of the operator product expansion and the
renormalization group method. We calculate Wilson coeffcients of local
operators, discuss mixing of operators under renormalization, the anomalous
dimensions of operators and anomalous dimension matrices. We elaborate on the
renormalzation scheme and renormalization scale dependences and their
cancellations in physical amplitudes. In particular we discuss the issue of
gamma-5 in D-dimensions and the role of evanescent operators in the calculation
of two-loop anomalous dimensions. We present an explicit calculation of the 6
times 6 one-loop anomalous dimension matrix involving current-current and
QCD-penguin operators and we give some hints how to properly calculate two-loop
anomalous dimensions of these operators. In the phenonomenological part of
these lectures we discuss in detail: CKM matrix, the unitarity triangle and its
determination, two-body non-leptonic B-decays and the generalized
factorization, the ratio epsilonprime/epsilon, B to X_s gamma, K^+ to pi^+ nu
barnu, K_L to pi^0 nu barnu, B to X_s nu barnu, B_s to mu bar mu and some
aspects of CP violation in B-decays.


title: The Phase Structure of an SU(N) Gauge Theory with N_f Flavors

abstract:
  We investigate the chiral phase transition in SU(N) gauge theories as the
number of quark flavors, $N_f$, is varied. We argue that the transition takes
place at a large enough value of $N_f$ so that it is governed by the infrared
fixed point of the $\beta$ function. We study the nature of the phase
transition analytically and numerically, and discuss the spectrum of the theory
as the critical value of $N_f$ is approached in both the symmetric and broken
phases. Since the transition is governed by a conformal fixed point, there are
no light excitations on the symmetric side. We extend previous work to include
higher order effects by developing a renormalization group estimate of the
critical coupling.


title: Topological Defects and Cosmology

abstract:
  Many particle physics models of matter admit solutions corresponding to
stable or long-lived topological defects. In the context of standard cosmology
it is then unavoidable that such defects will form during phase transitions in
the very early Universe. Certain types of defects lead to disastrous
consequences for cosmology, others may play a useful role, as possible seeds
for the formation of structure in the Universe, or in mediating baryon number
violating processes. In all cases, topological defects lead to a fruitful
interplay between particle physics and cosmology.


title: Solving QCD Using Multi-Regge Theory

abstract:
  This talk outlines the derivation of a high-energy, transverse momentum
cut-off, solution of QCD in which the Regge pole and ``single gluon''
properties of the pomeron are directly related to the confinement and chiral
symmetry breaking properties of the hadron spectrum. In first approximation,
the pomeron is a single reggeized gluon plus a ``wee parton'' component that
compensates for the color and particle properties of the gluon. This solution
corresponds to a supercritical phase of Reggeon Field Theory.


title: Radiative corrections to off-shell gauge-boson pair production

abstract:
  We give an overview of the problems and developments associated with the
calculation of radiative corrections to off-shell gauge-boson pair production
in e^+ e^- collisions.


title: A Four-Fermi Model in 0+1 Dimensions in Matter

abstract:
  The results of a number of constituent quark models in matter may be
understood in the mean-field approximation by using a simple four-fermi model
in 0+1 dimensions.


title: F-term Hybrid Inflation in Effective Supergravity Theories

abstract:
  We show that a particular class of effective low energy supergravity theories
motivated by string theory can provide a promising framework for models of
hybrid inflation in which the potential energy which drives inflation
originates from the F-term of the effective supergravity theory. In the class
of models considered the inflaton is protected from receiving mass during
inflation by a generalisation of the Heisenberg symmetry present in no-scale
supergravity models. The potential during inflation takes the positive definite
form $V\sim |F_S|^2 + |F_T|^2 -3$, which allows the possibility that $V\ll
m_{3/2}^2 M_P^2$ through the cancellation of the positive dilaton and moduli
contribution against the negative term. We discuss a toy example where this is
realised, then describe the application of this result to realistic models
focusing on a particular example in which the $\mu$ problem and the strong
CP-problem are addressed.


title: Self-dual homogeneous gluon field and electromagnetic structure of pion

abstract:
  The transition form factor, decay width and charge form factor of pion are
calculated within the model of induced nonlocal quark currents based on the
assumption that the nonperturbative QCD vacuum can be characterized by a
homogeneous (anti-)self-dual gluon field. It is shown that the interaction of
the quark spin with the vacuum gluon field, being responsible in the model for
the chiral symmetry breaking and the spectrum of light mesons, can also play
the decisive role in forming the transition form factor and two-photon decay
width. Asymptotic behavior of quark loops in the presence of the background
gluon field for large momentum transfer is discussed.


title: Chiral Disorder and QCD at Finite Chemical Potential

abstract:
  We investigate the effects of a finite chemical potential $\mu$ in QCD viewed
as a disordered medium. In the quenched approximation, $A_4=i\mu$ induces a
complex electric Aharonov-Bohm effect that causes the diagonal contribution to
the quark return probability to vanish at $\mu=m_{\pi}/2$ (half the pion mass).
In two-color QCD, the weak-localization contribution to the quark return
probability remains unaffected causing a mutation in the spectral statistics.
In full QCD, the complex electric flux is screened and the light quarks are
shown to diffuse asymmetrically with a substantial decrease in the conductivity
along the `spatial' directions. Mean-field arguments suggest that a d=1
percolation transition may take place in the range $1.5\rho_0<\rho<3\rho_0$,
where $\rho_0$ is nuclear matter density.


title: Limits on Cosmic Chiral Vortons

abstract:
  We study chiral vorton production for Witten-type superconducting string
models in the context of a recently developed analytic formalism. We delineate
three distinct scenarios: First, a low energy regime (including the electroweak
scale) where vortons can be a source of dark matter. Secondly, an intermediate
energy regime where the vorton density is too high to be compatible with the
standard cosmology (thereby excluding these models). Finally, a high energy
regime (including the GUT scale) in which no vortons are expected to form. The
vorton density is most sensitive to the order of the string-forming phase
transition and relatively insensitive to the current-forming transition. For a
second-order string transition, vorton production is cosmologically disastrous
for the range $10^{-28}\lsim G\mu \lsim 10^{-10}$ ($10^{5} GeV \lsim T_{c}
\lsim 10^{14} GeV$), while for the first-order case we can only exclude
$10^{-20}\lsim G\mu \lsim 10^{-14}$ ($10^{9} GeV \lsim T_{c} \lsim 10^{12}
GeV$). We provide a fitting formula which summarises our results.


title:
Progress in the Understanding of Dijet Production in Deep-Inelastic
  Scattering

abstract:
  Recent results on dijet production in deep-inelastic scattering from the H1
experiment at the ep-collider HERA are presented. Internal jet structure has
been studied in terms of jet shapes and subjet multiplicities in the Breit
frame. Both observables are seen to be well described by QCD models. We observe
a broadening of the jets towards the proton direction and at lower transverse
jet energies. Dijet rates and dijet cross sections have been measured over a
wide range of four momentum transfers (5 < Q^2 < 5000 GeV^2) and transverse jet
energies (25 < E^2_t,Breit < 1200 GeV^2) with different jet algorithms.
Perturbative QCD calculations in next-to-leading order in the strong coupling
constant give a good description of the data.


title: A resummation of large sub-leading corrections at small x

abstract:
  The NLL corrections to the BFKL kernel are known to be very large, to the
extent that even for small values of alpha_s, they lead to physical cross
sections which are not positive definite. It is shown in the context of a toy
model, that such pathological behaviour is an artifact of the truncation at NLL
order, and is associated in particular with double transverse logarithms. These
are resummed in a manner consistent with the full NLL kernel, and are shown to
change its properties quite considerably.


title:
On the numerical closeness of the effective phenomenological electroweak
  mixing angle $\theta$ and the $\MS$ parameter $\hat\theta$

abstract:
  It happens that $s^2$ and $\hat s^2$ are equal with 0.1% accuracy, though
they are split by radiative corrections and a natural estimate for their
difference is 1%. This degeneracy occurs only for $m_t$ value close to
$170\GeV$, so no deep physical reason can be attributed to it. However, another
puzzle of the Standard Model, the degeneracy of $s_\Eff^2$ and $s^2$, is not
independent of the previous one since a good physical reason exists for
$s_\Eff^2$ and $\hat s^2$ degeneracy. We present explicit formulas which relate
these three angles.


title: Sudakov Resummation for Prompt-Photon Production in Hadron Collisions

abstract:
  We present the explicit expressions for the resummation of large-x Sudakov
effects in the transverse-energy distribution of prompt-photons produced in
hadronic collisions, to next-to-leading logarithmic (NLL) accuracy.
Fragmentation processes do not contribute to the Sudakov resummation at NLL
level. In Mellin space, the resummed radiative factor factorizes in the product
of independent radiators for the two initial and the one final coloured partons
appearing in the Born process, times a simple factor describing the soft-gluon
interferences between initial and final states. The formulae are given in terms
of Mellin moments, and can be used for phenomenological applications using
standard techniques for the inverse-Mellin transforms. The calculations
presented in this work, when added to the existing works on DY and DIS
production, complete the theoretical ground-work necessary to carry out global
fits of parton densities with a uniform NLL accuracy in the large-x region.


title: Summary of the Diffractive Working Group at DIS98

abstract:
  Recent experimental and theoretical developments in the understanding of high
energy diffraction, presented in the working group on diffraction at DIS98 in
Brussels, are summarised. A template, giving the definition of the most
commonly used kinematical variables in diffraction, which was provided in the
working group sessions, is reproduced as a appendix. References to original
papers may be found within the individual contributions.


title: Single Top Quark Production via FCNC Couplings at Hadron Colliders

abstract:
  We calculate single top-quark production at hadron colliders via the
chromo-magnetic flavor-changing neutral current couplings $\bar tcg$ and $\bar
tug$. We find that the strength for the anomalous $\bar tcg$ ($\bar tug$)
coupling may be probed to $\kappa_c / \Lambda = 0.092 {TeV}^{-1}$ ($\kappa_u /
\Lambda = 0.026 {TeV}^{-1}$) at the Tevatron with $2 {fb}^{-1}$ of data and
$\kappa_c / \Lambda = 0.013 {TeV}^{-1}$ ($\kappa_u / \Lambda = 0.0061
{TeV}^{-1}$) at the LHC with $10 {fb}^{-1}$ of data. The two couplings may be
distinguished by a comparision of the single top signal with the direct top and
top decay signals for these couplings.


title: On the invisible decays of the Upsilon and J/Psi resonances

abstract:
  We estimate the most important corrections to the branching ratios for the
invisible decays of quarkonium states, arising from possible extensions of the
standard model. Among the possibilities considered are the presence of extra
Z-bosons, minimal supersymmetric extensions of the standard model with R-parity
violation, and decays into goldstinos. Prospects of detecting these corrections
at existing and future B-factories and tau-charm factories are discussed.


title: Do heavy sfermions decouple from low energy Standard Model?

abstract:
  We explore analytically how does the Standard Model emerge as the quantum low
energy effective theory of the Minimal Supersymmetric Standard Model (MSSM) in
the decoupling limit where the sparticles are much heavier than the electroweak
scale. In this work we integrate the sfermions to one-loop and compute their
contributions to the effective action for standard electroweak gauge bosons. A
proof of decoupling of sfermions is performed by analyzing the resulting
effective action in the asymptotic limit $m_{\tilde f} \gg m_z$. A discussion
on how the decoupling takes place in terms of both the sparticle physical
masses and the non-physical MSSM parameters is included.


title:
The Full Range of Predictions for B Physics From Iso-singlet Down Quark
  Mixing

abstract:
  We extend the range of predictions of the isosinglet (or vector) down quark
model to the fully allowed physical ranges, and also update this with the
effect of new physics constraints. We constrain the present allowed ranges of
sin(2*beta) and sin(2*alpha), gamma, x_s, and A_{B_s}. In models allowing
mixing to a new isosinglet down quark (as in E_6) flavor changing neutral
currents are induced that allow a Z^0 mediated contribution to B-Bbar mixing
and which bring in new phases. In (rho, eta), (x_s, sin(gamma)), and (x_s,
A_{B_s}) plots for the extra isosinglet down quark model which are herein
extended to the full physical range, we find new allowed regions that will
require experiments on sin(gamma) and/or x_s to verify or to rule out an extra
down quark contribution.