title: Suppressing dimension-5 operators in general SU(5) models

abstract:
  We discuss dimension-5 operators in supersymmetric models containing extra
hypercharge 1/3 color-triplets. We derive a general formula relating
dimension-5 operator to the color-triplet mass matrix. We show that certain
zeros in the triplet mass-matrix together with some triplet coupling selection
rules can lead to elimination of dimension-5 operators. In particular we focus
on SU(5) models and show that (a) Dimension-5 operators can be eliminated in
the standard SU(5) model by the introduction of an extra pair of 5+5b Higgses
with specific couplings (b) Flipped SU(5) models with extra 10+10b Higgses are
free of dimension-5 operators (c) Flipped SU(5) models with extra 5+5b and/or
extra 10+10b Higgses can be made free of dimension-5 operators for a textured
form of the triplet mass-matrix accompanied by constraints on the 5-plet
couplings to matter. Our analysis is motivated by the recently put forward
M-theory phenomenological framework that requires a strong string coupling and
reintroduces the problem of eliminating dimension-5 operators.


title: Leptoquark Production and Identification at High Energy Lepton Colliders

abstract:
  Leptoquarks can be produced in substantial numbers for masses very close to
the collider centre of mass energy in $e^+e^-$, $e\gamma$, and $\mu^+\mu^-$
collisions due to the quark content of the photon resulting in equivalently
high discovery limits. Using polarization asymmetries in an $e\gamma$ collider
the ten different types of leptoquarks listed by Buchm\"uller, R\"uckl and
Wyler can be distinquished from one another for leptoquark masses essentially
up to the kinematic limit. Thus, if a leptoquark were discovered, an $e\gamma$
collider could play a crucial role in determining its origins.


title: Collapse of topological texture

abstract:
  We study analytically the process of a topological texture collapse in the
approximation of a scaling ansatz in the nonlinear sigma-model. In this
approximation we show that in flat space-time topological texture eventually
collapses while in the case of spatially flat expanding universe its fate
depends on the rate of expansion. If the universe is inflationary, then there
is a possibility that texture will expand eternally; in the case of exponential
inflation the texture may also shrink or expand eternally to a finite limiting
size, although this behavior is degenerate. In the case of power law
noninflationary expansion topological texture eventually collapses. In a cold
matter dominated universe we find that texture which is formed comoving with
the universe expansion starts collapsing when its spatial size becomes
comparable to the Hubble size, which result is in agreement with the previous
considerations. In the nonlinear sigma-model approximation we consider also the
final stage of the collapsing ellipsoidal topological texture. We show that
during collapse of such a texture at least two of its principal dimensions
shrink to zero in a similar way, so that their ratio remains finite. The third
dimension may remain finite (collapse of cigar type), or it may also shrink to
zero similar to the other two dimensions (collapse of scaling type), or shrink
to zero similar to the product of the remaining two dimensions (collapse of
pancake type).


title: Lorentz Covariant Spin-Grouping of Baryon Resonances

abstract:
  A well pronounced spin--grouping of baryon resonances to O(4) partial waves
is found in baryon spectra and shown to be well interpreted in terms of Lorentz
group representations of the type (1/2 +l', 1/2 +l')* [(1/2, 0)+(0,1/2)] with
l' integer. In this way the relativistic description of finite dimensional
resonance towers containing higher-spin states becomes possible. It is further
argued that the nucleon excitations into the l'=1 and l'=2 multiplets are
chiral phase transitions.


title:
Accurate prediction of electroweak observables and impact on the Higgs
  mass bound

abstract:
  I discuss the importance of the $O(g^4 m_t^2/\mw^2)$ corrections to the
effective electroweak angle and Mw in the indirect determination of the Higgs
mass. I emphasize the r\^ole of a very precise Mw measurement on the Mh
estimate.


title: Fermi Motion and Quark Off-Shellness in Elastic Vector-Meson Production

abstract:
  We study ways of implementing Fermi momentum in elastic vector-meson
production, and find that the usual on-shell assumption of quark models and
quark wave functions cannot reproduce the ratio of the longitudinal cross
section to the transverse one. We propose a new approach which allows the
quarks to be off-shell, and which naturally reproduces the data. As a
consequence, we prove that the asymptotic form of the transverse cross section
is different from 1/Q^8. In this new model, we show that the mass, t and Q2
dependence of the cross sections are also reproduced. We also make predictions
concerning the production of excited states such as the rho' and the psi'.


title: Baryon masses in a loop expansion with form factor

abstract:
  We show that the average multiplet masses in the baryon octet and decuplet
can be fitted with an average error of only $0.5\pm 0.3$ MeV in a meson loop
expansion with chiral SU(6) couplings, with the hadrons treated as composite
particles using a baryon-meson form factor. The form factor suppresses
unphysical short distance effects and leads to a controllable expansion. We
find, in contrast to the results of standard chiral perturbation theory, that
pion loops are as important as kaon or eta loops as would be expected when only
intermediate- and long-distance contributions are retained. We also find that
the contributions of decuplet intermediate states are important in the
calculation of the masses, and those states must be included explicitly in a
consistent theory. These results agree with those of our recent loop-expansion
analysis of the baryon magnetic moments. We show, finally, that the parts of
the loop contributions that change the tree-level structure of the baryon
masses are small, but largely account for the violations of the baryon mass sum
rules which hold at tree level.


title: Random Matrix Theory and QCD at nonzero chemical potential

abstract:
  In this lecture we give a brief review of chiral Random Matrix Theory (chRMT)
and its applications to QCD at nonzero chemical potential. We present both
analytical arguments involving chiral perturbation theory and numerical
evidence from lattice QCD simulations showing that correlations of the smallest
Dirac eigenvalues are described by chRMT. We discuss the range of validity of
chRMT and emphasize the importance of universality. For chRMT's at $\mu \ne 0 $
we identify universal properties of the Dirac eigenvalues and study the effect
of quenching on the distribution of Yang-Lee zeros.


title:
The scale dependent nuclear effects in parton distributions for
  practical applications

abstract:
  The scale dependence of the ratios of parton distributions in a proton of a
nucleus $A$ and in the free proton, $R_i^A(x,Q^2)=f_{i/A}(x,Q^2)/f_i(x,Q^2)$,
is studied within the framework of the lowest order leading-twist DGLAP
evolution. By evolving the initial nuclear distributions obtained with the
GRV-LO and CTEQ4L sets at a scale $Q_0^2$, we show that the ratios
$R_i^A(x,Q^2)$ are only moderately sensitive to the choice of a specific modern
set of free parton distributions. We propose that to a good first
approximation, this parton distribution set-dependence of the nuclear ratios
$R_i^A(x,Q^2)$ can be neglected in practical applications. With this result, we
offer a numerical parametrization of $R_i^A(x,Q^2)$ for all parton flavours $i$
in any $A>2$, and at any $10^{-6}\le x \le 1$ and any $Q^2\ge 2.25$ GeV$^2$ for
computing cross sections of hard processes in nuclear collisions.


title: Pion form factors with improved infrared factorization

abstract:
  We calculate electromagnetic pion form factors with an analytic model for
$\alpha_{\rm s}(Q^2)$ which is infrared (IR) finite without invoking a
``freezing'' hypothesis. We show that for the asymptotic pion distribution
amplitude, $F_{\pi ^{0}\gamma ^{*}\gamma}$ agrees well with the data, whereas
the IR-enhanced hard contribution to $F_{\pi}$ and the soft (nonfactorizing)
part can jointly account for the data.


title: Classical effective theory for hot QCD

abstract:
  In high temperature QCD, the perturbation theory is plagued with infrared
divergences which reflect long-range non-perturbative phenomena. I argue that
it is possible to study such phenomena within a classical thermal field theory
which can be put on a three-dimensional lattice. The classical theory is an
effective theory for the soft, non-perturbative modes, as obtained after
integrating out the hard modes in perturbation theory. It is well suited for
numerical studies of the non-perturbative real-time dynamics, which cannot be
studied within the standard, imaginary-time formulations of lattice QCD.


title: Bounds on Schr\"odinger Energies

abstract:
  Elementary introduction to the application of Mathematica 3.0 to the solution
of bound-state problems in quantum theory by standard variational procedures,
with particular emphasis on the computation of precise upper bounds on energy
levels of the system under consideration.


title: In-medium modification of $\rho$-mesons produced in heavy ion collisions

abstract:
  The mass shift $\Delta m_{\rho}$ and width broadening $\Delta\Gamma_{\rho}$
of $\rho$ mesons produced in heavy ion collisions is estimated using a general
formula which relates the in-medium mass shift of a particle to the real part
of the forward scattering amplitude ${\rm Re} f(E)$ of this particle on
constituents of the medium and $\Delta\Gamma$ to the corresponding cross
section. It is found that in high energy ($E/A \ga 100~$GeV) heavy ion
collisions the $\rho$ width broadening is large and $\rho$ (or $\omega$) peak
could hardly be observed in $e^+e^-(\mu^+\mu^-)$ effective mass distributions.
In low energy collisions ($E/A \sim$ a few GeV) a broad (a few hundred MeV)
enhancement is expected at the position of the $\rho$ peak.


title: A renormalisation-group treatment of two-body scattering

abstract:
  Nonrelativistic two-body scattering by a short-ranged potential is studied
using the renormalisation group. Two fixed points are identified: a trivial one
and one describing systems with a bound state at zero energy. The eigenvalues
of the linearised renormalisation group are used to assign a systematic
power-counting to terms in the potential near each of these fixed points. The
expansion around the nontrivial fixed point is shown to be equivalent to the
effective-range expansion.


title: Hadronization with a confining equation of state

abstract:
  We present a fast hadronization model for the constituent quark plasma (CQP)
produced in relativistic heavy ion collisions at SPS. The model is based on
rate equations and on a confining equation of state inspired by the string
phenomenology. We display the time evolution of the relevant physical
quantities during the hadronization process and the final hadron
multiplicities. The results indicate that the hadronization of CQP is fast.


title: The Gluon Condensate in QCD at Finite Temperature

abstract:
  We begin with the discussion of the relationship between the trace of the
energy momentum tensor and the gluon condensate at finite temperatures. Using
the recent numerical data from the simulations of lattice gauge theory for
quantum chromodynamics(QCD) we present the computational evaluations for the
gluon condensate. A short discussion of the properties of deconfinement and the
implications on the high temperature limit are included. We also mention the
case of the massive quarks where some of the properties of the condensate
appear to change. We put together these results with some ideas related to the
dilatation current. We draw the conclusion that the nature of the strong
interactions implies that the thermodynamics of quarks and gluons never
approach even at very high temperatures that of an ideal ultrarelativistic gas.


title:
Active-active and active-sterile neutrino oscillation solutions to the
  atmospheric neutrino anomaly

abstract:
  We perform a fit to the full data set corresponding to 33.3 kt-yr of data of
the Super-Kamiokande experiment as well as to all other experiments in order to
compare the two most likely solutions to the atmospheric neutrino anomaly in
terms of oscillations in the $\nu_\mu \to \nu_\tau$ and $\nu_\mu \to \nu_s$
channels. Using state-of-the-art atmospheric neutrino fluxes we have determined
the allowed regions of oscillation parameters for both channels. We find that
the $\Delta m^2$ values for the active-sterile oscillations (both for positive
and negative $\Delta m^2$) are higher than for the $\nu_\mu \to \nu_\tau$ case,
and that the increased Super-Kamiokande sample slightly favours $\nu_\mu \to
\nu_\tau$ oscillations over oscillations into a sterile species $\nu_s$,
$\nu_\mu \to \nu_s$, and disfavours $\nu_\mu \to \nu_e$. We also give the
zenith angle distributions predicted for the best fit points in each of the
possible oscillation channels. Finally we compare our determinations of the
atmospheric neutrino oscillation parameters with the expected sensitivities of
future long-baseline experiments K2K, MINOS, ICARUS, OPERA and NOE.


title: Solar models and neutrino deficit

abstract:
  The existing measurements of the solar neutrino flux are compared with the
predictions of all models capable of reproducing the other solar observables.
These predictions are supplemented by the hypothesis of neutrino oscillations
with mass differences large enough to render energy-independent the depletion
of the solar nu(e) flux. It is concluded that the data are consistent with this
hypothesis and that an energy-dependence of the solar neutrino deficit must be
regarded as an attractive possibility but not as a compelling reality.


title: Gauged $B - 3 L_\tau$ and Baryogenesis

abstract:
  It has recently been shown that by extending the minimal standard model to
include a right-handed partner to $\nu_\tau$, it is possible to gauge the $B -
3 L_\tau$ quantum number consistently. If we add two scalar triplets, one
trivial ($\xi_1$) and one nontrivial ($\xi_2$) under $B - 3 L_\tau$, it is
possible also to have desirable neutrino masses and mixing for neutrino
oscillations. At the same time, a lepton asymmetry can be generated in the
early universe through the novel mechanism of the decay of the heavier $\xi_1$
into the lighter $\xi_2$ plus a neutral singlet ($\zeta^0$). This lepton
asymmetry then gets converted into a baryon asymmetry at the electroweak phase
transition.


title: Models of Supersymmetric $U(2)\times U(1)$ Flavor Symmetry

abstract:
  We use a $U(2)\times U(1)$ horizontal symmetry in order to construct
supersymmetric models where the flavor structure of both quarks and leptons is
induced naturally. The supersymmetric flavor changing neutral currents problem
is solved by the degeneracy between sfermions induced by the U(2) symmetry. The
additional U(1) enables the generation of mass ratios that cannot be generated
by U(2) alone. The resulting phenomenology differs from that of models with
either abelian or $U(2)\times GUT$ symmetries. Our models give rise to
interesting neutrino spectra, which can incorporate the Super-Kamiokande
results regarding atmospheric neutrinos.


title: $b\to s\gamma$ Decay in Supersymmetric Theories

abstract:
  Recent advances in the calculation of the $b\to s\gamma$ decay branching
ratio are presented in the context of supersymmetric theories. Theoretical
accuracy increased by inclusion of the next-to-leading order QCD corrections
makes it possible to significantly decrease scale dependence of the result.
Comparison with the latest CLEO experimental results then allows to limit
supersymmetric loop contributions to the process and consequently constrain the
parameter space of supersymmetric extensions of the Standard Model. We discuss
these constraints both in the minimal supergravity inspired model (SUGRA) and
in the simplest gauge-mediated supersymmetry breaking model (GMSB) both of
which are interesting from the point of view of the searches for supersymmetry
at present and future colliders. Our analysis also includes the interesting
region of large $\tan \beta$ relevant for models with Yukawa coupling
unification.


title: Neutrino mixing and see-saw mechanism

abstract:
  Models of neutrino masses are discussed capable of explaining in a natural
way the maximal mixing between $\nu_{\mu}$ and $\nu_{\tau}$ observed by the
Super-Kamiokande collaboration. For three generations of leptons two classes of
such models are found implying: a) $\Delta {m_{23}}^2 \ll \Delta {m_{12}}^2
\approx \Delta {m_{13}}^2 $ and a small mixing between $\nu_{e}$ and the other
two neutrinos, b) $\Delta {m_{12}}^2 \ll \Delta {m_{13}}^2 \approx \Delta
{m_{23}}^2$ and a nearly maximal mixing for solar neutrino oscillations in
vacuum.


title:
Production of $e^+e^-$ pairs to all orders in $Z\alpha$ for collisions
  of high-energy muons with heavy nuclei

abstract:
  The $e^+e^-$ pair production in collisions of muon with atoms is considered
to all orders in the parameter $Z\alpha$. We obtain energy distribution of
$e^+$ and $e^-$ as well as energy loss of muon passing through matter with
heavy atoms. The found corrections to the Born contribution do not depend on
the details of the target properties except of a simple factor. For the
considered example of Pb target the muon energy loss corrections vary from -65
% to -10 % depending on the pair energy.


title: R-Parity Violating Signals at Existing Colliders

abstract:
  Formation of the $s$-channel slepton resonances at LEP2 or Tevatron at
current energies is an exciting possibility in R-parity violating SUSY models.
Existing LEP2 and Tevatron data can be exploited to look for sleptons, or to
derive bounds on the Yukawa couplings of sleptons to quark and lepton pairs.


title:
Formation of color-singlet gluon-clusters and inelastic diffractive
  scattering. Part I: Theoretical arguments and experimental indications for
  self-organized criticality (SOC) in systems of interacting soft gluons

abstract:
  It is proposed, that color-singlet gluon-clusters can be formed in hadrons as
a consequence of self-organized criticality (SOC) in systems of interacting
soft gluons, and that the properties of such spatiotemporal complexities can be
probed experimentally by examing inelastic diffractive scattering. Theoretical
arguments and experimental evidences supporting the proposed picture are
presented --- together with the result of a systematic analysis of the existing
data for inelastic diffractive scattering processes performed at different
incident energies, and/or by using different beam-particles. It is shown that
the size- and the lifetime-distributions of such gluon-clusters can be directly
extracted from the data, and the obtained results exhibit universal power-law
behaviors --- in accordance with the expected SOC-fingerprints.


title:
Formation of color-singlet gluon-clusters and inelastic diffractive
  scattering. Part II: Derivation of the $t$- and $M_x^2/s$-dependence of
  cross-sections in the SOC-approach

abstract:
  The $t$-dependence and the $(M_x^2/s)$-dependence of the double differential
cross-sections for inelastic diffractive scattering off proton-target are
discussed. Here $t$ stands for the four-momentum-transfer squared, $M_x$ for
the missing mass, and $\sqrt{s}$ for the total c.m.s. energy. It is shown, that
the space-time properties of the color-singlet gluon-clusters due to SOC,
discussed in Part I, lead to simple analytical formulae for $d^2\sigma/dt
d(M_x^2/s)$ and for $d\sigma/dt$, and that the obtained results are in good
agreement with the existing data. Further experiments are suggested.


title: Implications of the Superkamiokande result on the nature of new physics

abstract:
  It is remarked that the SuperKamiokande (SK) discovery of $\nu_\mu$ to
$\nu_\tau$ (or $\nu_X$)-oscillation, with a $\delta m^2 \approx 10^{-2}-10^{-3}
eV^2$ and $sin^2 2 \theta > 0.8$, provides a clear need for the right-handed
(RH) neutrinos. This in turn reinforces the ideas of the left-right symmetric
gauge structure $SU(2)_L \times SU(2)_R$ as well as SU(4)-color, for which the
RH neutrinos are a compelling feature. It is noted that by assuming (a) that
B-L and $I_{3R}$, contained in a string-derived $G(224) = SU(2)_L \times
SU(2)_R \times SU(4)^c$ or SO(10), break near the GUT-scale, as opposed to an
intermediate scale, (b) the see-saw mechanism, and (c) the SU(4)-color relation
between the Dirac mass of the tau neutrino and $m_{top}$, one obtains a mass
for $\nu^\tau_L$ which is just about what is observed. This is assuming that
the SK group is actually seeing $\nu^\mu_L - \nu^\tau_L$ (rather than
$\nu_L^\mu - \nu_X$) oscillation. Following a very recent work by Babu, Wilczek
and myself, it is furthermore noted that one can quite plausibly obtain a large
$\nu_L^\mu-\nu_L^\tau$ oscillation angle, as observed, in spite of highly
non-degenerate masses of the light neutrinos: e.g. with
$m(\nu_L^\mu)/m(\nu_L^\tau)\approx 1/10-1/20$. Such non-degeneracy is of course
natural to see-saw. In this case, $\nu^e_L - \nu^\mu_L$ oscillation can be
relevant to the small angle MSW explanation of the solar neutrino puzzle.
Implications of the mass of $\nu^\tau_L$ suggested by the SK result, on proton
decay are noted. Comments are made at the end on how the SuperKamiokande result
supplements the LEP result in selecting out the route to higher unification.


title: Gluon Resummation in Vector Boson Production and Decay

abstract:
  After a brief review on the technique of resumming the large logarithmic
terms $\alpha^n_s \ln^m(Q^2/Q^2_T)$ due to the effects of multiple gluon
emission predicted by the QCD theory, I discuss its application in the
production of $W^\pm$, $Z$ and $\gamma \gamma$ in hadron collision.


title: The K^{+}--->\pi^{+}\nu\bar{nu} Rare Decay in Two Higgs Doublet Model

abstract:
  The rare k+--->pi+ \nu \bar{\nu} decay is investigated in the context of type
II two-Higgs-doublet model (2HDM). By using the existing experimental data of
the branching ratio, restrictions on the free parameters of the model m_H, and
tan\beta are obtained: tan\beta belong to the range 0.7- o.8, and m_H belong to
the range 500- 700 GeV.


title:
Three-Flavor QCD at High Density: Color Flavor Locking and Chiral
  Symmetry Breaking

abstract:
  We propose a symmetry breaking scheme for QCD with three massless quarks at
high baryon density wherein the color and flavor
SU(3)_{color}xSU(3)_{L}xSU(3)_{R} symmetries are broken down to the diagonal
subgroup SU(3)_{color+L+R} by the formation of a condensate of quark Cooper
pairs. We discuss general properties that follow from this hypothesis,
including the existence of gaps for quark and gluon excitations, the existence
of Nambu-Goldstone bosons which are excitations of the diquark condensate, and
the existence of a modified electromagnetic gauge interaction which is unbroken
and which assigns integral charge to the elementary excitations. We present
mean-field results for a Hamiltonian in which the interaction between quarks is
modelled by that induced by single-gluon exchange. We find gaps of order 10-100
MeV for plausible values of the coupling. We discuss the effects of nonzero
temperature, nonzero quark masses and instanton-induced interactions on our
results.


title: Generalized Neutrino Mixing from the Atmospheric Anomaly

abstract:
  We determine the neutrino mixing and mass parameters that are allowed by the
Super-Kamiokande atmospheric neutrino data in a three-neutrino model with one
mass-squared difference contributing to the oscillations. We find that although
$\nu_\mu\to\nu_\tau$ oscillations are favored, $\nu_\mu\to \nu_e$ oscillations
with amplitude as large as 0.18 are allowed even after accounting for the limit
from the CHOOZ reactor experiment. The range of allowed parameters permit
observable $\nu_\mu\leftrightarrow\nu_e$ and $\nu_e\to\nu_\tau$ oscillations in
future long-baseline experiments.


title:
Detecting new physics contributions to the D0-D0bar mixing through their
  effects on B decays

abstract:
  New physics effects may yield a detectable mass difference in the D0-D0bar
system, Delta m_D. Here we show that this has an important impact on some B -->
D decays. The effect involves a new source of CP violation, which arises from
the interference between the phases in the B --> D decays and those in the
D0-D0bar system. This interference is naturally large. New physics may well
manifest itself through Delta m_D contributions to these B decays.


title: Effects of Heavy States on the Effective N=1 Supersymmetric Action

abstract:
  Using the power of superspace formalism, we investigate the decoupling
effects of heavy states in N=1 supersymmetric field theory. We find that
"mixed" couplings in the superpotential between the heavy and light fields
contribute to the effective superpotential at the leading order, and also
contribute to the effective K\"{a}hler potential (in the next to leading
order). Mixed couplings in the K\"{a}hler potential always contribute to the
effective K\"{a}hler potential at the leading order. Several examples are
presented which illustrate the effects explicitly.


title: Superstring Axion, Gaugino Condensation, and Discrete Symmetries

abstract:
  Here I present the effect of gaugino condensation and discrete symmetries to
the model-independent axion potential, collaborated with Georgi and Nilles
[hep-ph/9805510].


title: Hadronic Charmless B Decays and Nonfactorizable Effects

abstract: Hadronic charmless B decays and their nonfactorizable effects are reviewed.


title: Polarization in diffractive electroproduction of light vector mesons

abstract:
  We study in perturbative QCD the helicity ampltiudes of the process
$\gamma^{*} p \to \rho p $ at large virtualities $Q$ of the photon
$\gamma^{*}$. We estimate all spin flip amplitudes taking into account an
important effect of the scale behaviour of the gluon density. The transition of
a transverse virtual photon to a longitudinal vector meson is not small at
typical HERA conditions. This helicity non-conserving amplitude leads by
interference to a measurable effect in the distribution of the angle between
the electron scattering and the meson production planes.


title: Bi-Maximal Neutrino Mixing in SO(10)_{GUT}

abstract:
  We find a grand unified SO(10) model which accommodates the bi-maximal
neutrino mixing for vacuum-oscillation solutions to the atmospheric and the
solar neutrino problems. This model maintains the original SO(10) mass relation
between neutrino and up-type quark masses, $m_{\nu_2} / m_{\nu_3} \sim
(m_{c}/m_{t})^2$.


title: Another look at $\pi\pi$ scattering in the scalar channel

abstract:
  We set up a general framework to describe $\pi\pi$ scattering below 1 GeV
based on chiral low-energy expansion with possible spin-0 and 1 resonances.
Partial wave amplitudes are obtained with the $N/D$ method, which satisfy
unitarity, analyticity and approximate crossing symmetry. Comparison with the
phase shift data in the J=0 channel favors a scalar resonance near the $\rho$
mass.


title: Supersymmetric Neutrino Masses and Mixing with R-parity Violation

abstract:
  In the context of the minimal supersymmetric standard model, nonzero neutrino
masses and mixing can be generated through renormalizable lepton number (and
thus R-parity) violating operators. It is examined whether neutrino mass
matrices from tree and one-loop contributions can account for two mass-squared
differences and mixing angles that explain current experimental data. By
accommodating, in particular, the solar and atmospheric neutrino data, we find
interesting restrictions not only on the free parameters of the theory, such as
lepton number violating couplings and soft-parameters, but also on the
oscillation parameters of atmospheric neutrinos.


title:
Comment on the paper: ``The perturbative proton form factor reexamined''
  by Kundu et al

abstract:
  We point out some serious problems in the investigation of Kundu et al. which
claims agreement with the existing data of the proton form factor, calculated
without taking into account the intrinsic k_{perp}-dependence of the proton
wave function.


title: D-wave heavy quarkonium production in fixed target experiments

abstract:
  We calculate the $D$-wave heavy quarkonium production at fixed target
experiments under the NRQCD factorization formalism. We find that the color
octet contributions are two orders of magnitude larger than color-singlet
contributions if color-octet matrix elements are taken according to the NRQCD
velocity scaling rules. Within the theoretical uncertainties, the prediction
for the production rate of $2^{--}$ $D$-wave charmonium state agrees with the
preliminary result of E705 and other experiments. Searching for the $1^{--}$
$D$-wave state $\psi(3770)$ is further suggested.


title: An operator expansion for the elastic limit

abstract:
  A leading twist expansion in terms of bi-local operators is proposed for the
structure functions of deeply inelastic scattering near the elastic limit $x
\to 1$, which is also applicable to a range of other processes. Operators of
increasing dimensions contribute to logarithmically enhanced terms which are
supressed by corresponding powers of $1-x$. For the longitudinal structure
function, in moment ($N$) space, all the logarithmic contributions of order
$\ln^k N/N$ are shown to be resummable in terms of the anomalous dimension of
the leading operator in the expansion.


title: Linear sigma model and chiral symmetry at finite temperature

abstract:
  The chiral phase transition is investigated within the framework of the
linear sigma model at finite temperature. We concentrate on the meson sector of
the model and calculate the finite temperature effective potential in the
Hartree approximation by using the Cornwall-Jackiw-Tomboulis formalism of
composite operators. The effective potential is calculated for N=4 involving
the usual sigma and three pions and in the large N approximation involving N-1
pion fields. In the N=4 case we have examined the theory both in the chiral
limit and with the presence of a symmetry breaking term which generates the
pion masses. In both cases we have solved the system of the resulting gap
equations for the thermal effective masses of the particles numerically and we
have investigated the evolution of the effective potential. In the N=4 case
there is indication of a first order phase transition and the Goldstone theorem
is not satisfied. The situation is different in the general case using the
large $N$ approximation, the Goldstone theorem is satisfied and the phase
transition is of the second order. For this analysis we have ignored quantum
effects and we used the imaginary time formalism for calculations.


title:
All-Orders Resummation of Leading Logarithmic Contributions to Heavy
  Quark Production in Polarized \gamma \gamma Collisions

abstract:
  The measurements of the $\gamma\gamma$ and $b \bar b$ partial decay widths of
an intermediate-mass Standard Model Higgs boson are among the most important
goals of a future photon linear collider. While in an initially polarized
$J_z=0$ state the background process $\gamma\gamma \to b \bar b$ is suppressed
by $\frac{m^2_b}{s}$, radiative corrections remove this suppression and are
known to be very sizable at theone-loop level. In particular a new type of
purely hard double logarithmic (DL) correction can even make the cross section
negative at this order in perturbation theory. The second order term of the
series is also known and enters with a positive sign at the two loop level.
  From a theoretical as well as a practical point of view it is
clearlydesirable to resum this series and to know its high energy behavior.
  In this paper, we derive the series of these novel ``non-Sudakov'' logarithms
to all orders and calculate the high energy limit analytically. We also give
explicit three loop corrections in the DL-approximation as a check of our
results and show that the three loop structure also reveals the higher order
behavior of mixed hard and soft double logarithms. We are thus able to resum
the virtual DL-corrections to $\gamma\gamma (J_z=0) \to b \bar b$ to all
orders.


title: Heavy quark limit in the light front quark model

abstract:
  An explicit relativistic light-front model is presented which gives the
momentum transfer dependent form factors of weak hadronic currents among heavy
pseudoscalar and vector mesons in the whole accessible kinematical region
$0\leq q^2 \leq q^2_{\max} $. It is shown that in the limit of infinite masses
of active quarks these form factors can be expressed in terms of universal
Isgur-Wise function. The explisit expression for this function is obtained. It
is shown that neglecting of pair creation from the vacuum in calculations of
form factors does not violate Luke's theorem.


title: Masses of Orbitally Excited Baryons in Large N_c QCD

abstract:
  We present the first phenomenological study of the masses of orbitally
excited baryons in large N_c QCD. Restricting here to the nonstrange sector of
the L=1 baryons, the 1/N_c expansion is used to order and select a basis of
effective operators that spans the nine observables (seven masses and two
mixing angles). Fits are performed using subsets of the complete set of nine
operators, including corrections up to O(1/N_c) where leading order is N_c^1.
This study shows that the 1/N_c expansion provides an excellent framework for
analyzing the mass spectrum, and uncovers a new hierarchy of operator
contributions.


title: Axion potential, topological defects and CP-odd bubbles in QCD

abstract:
  It follows on general grounds that the theta dependence in QCD is more
complicated than suggested by the large N_c approach or instanton arguments.
Generically, the vacuum energy E_{vac}(\theta) is a multi-valued function of
\theta admitting the existence of metastable states. We discuss decays of such
metastable vacua in the theory with and without the axion, and point out the
potential relevance of this and related phenomena for constraining a dark
matter axion. Based on the analysis of the axion potential, an idea for a new
axion search experiment at RHIC is suggested. It is noted that the false vacuum
decay proceeds with maximal violation of CP, even if \theta = 0. We further
speculate that the famous Sakharov criteria for baryogenesis could be satisfied
at the QCD scale.


title:
Inverting the Supersymmetric Standard Model Spectrum: from Physical to
  Lagrangian Ino Parameters

abstract:
  We examine the possibility of recovering the supersymmetric (and soft
supersymmetry breaking) Lagrangian parameters as direct {\em analytical}
expressions of appropriate physical masses, for the unconstrained (but CP and
R-parity conserving) minimal supersymmetric standard model. We concentrate
mainly on the algebraically non-trivial "inversion" for the ino parameters, and
obtain, for given values of $\tan\beta$, simple analytical expressions for the
$\mu$, $M_1$ and $M_2$ parameters in terms of three arbitrary input physical
masses, namely either two chargino and one neutralino masses, or alternatively
one chargino and two neutralino masses. We illustrate and discuss in detail the
possible occurrence of ambiguities in this reconstruction. The dependence of
the resulting ino Lagrangian parameters upon physical masses is illustrated,
and some simple generic behaviour uncovered in this way. We finally briefly
sketch generalizing such an inversion to the full set of MSSM Lagrangian
parameters.


title:
On the Size of the Chiral Condensate, Generalized Chiral Perturbation
  Theory and the DIRAC experiment

abstract:
  In the near future, the DIRAC collaboration will measure pion-pion scattering
lengths with great precision. Those measurements are likely to shed some light
on the problem of the size of the chiral quark-antiquark condensate. Although
it is usually assumed to be as a large as (-225 MeV)^3, in the last years a
more general approach, has been developed to accommodate either a large or a
small alternative (-100 MeV)^3. Such a low value would also modify the standard
temperature estimate at which the chiral phase transition occurs. In this work
we briefly review the basic theoretical ideas related to this issue as well as
the experiment that could help to establish any of the two scenarios.


title: Interactions of a neutrino with an extremely light scalar

abstract:
  An extremely light scalar weakly interacting with light neutrinos has
interesting consequences in stellar evolution, neutrino oscillations and
laboratory neutrino mass measurements. In this paper we construct realistic
gauge models for such scalar-neutrino interactions.


title: Preheating of Fermions

abstract:
  In inflationary cosmology, the particles constituting the Universe are
created after inflation in the process of reheating due to their interaction
with the oscillating inflaton field. In the bosonic sector, the leading channel
of particle production is the non-perturbative regime of parametric resonance,
preheating, during which bosons are created exponentially fast. Pauli blocking
prohibits the unbounded creation of fermions. For this reason, it has been
silently assumed that the creation of fermions can be treated with perturbation
theory for the decay of individual inflatons. We consider the production of
fermions interacting with the coherently oscillating inflatons. We find that
the actual particle production occurs in a regime of the parametric excitation
of fermions, leading to preheating of fermions. Fermion preheating differs
significantly from the perturbative expectation. It turns out that the number
density of fermions varies periodically with time. The total number of fermions
quickly saturates to an average value within a broad range of momenta $\propto
q^{1/4}$, where $q$ is the usual resonance parameter. The resonant excitation
of fermions may affect the transfer inflaton energy, estimations of the
reheating temperature, and the abundance of superheavy fermions and gravitinos.
Back in the bosonic sector, outside of the parametric resonance bands there is
an additional effect of parametric excitation of bosons with bounded occupation
number in the momentum range $\propto q^{1/4}$.


title: Single-top-quark production at hadron colliders

abstract:
  Single-top-quark production probes the charged-current weak interaction of
the top quark, and provides a direct measurement of the CKM matrix element
V_{tb}. We perform two independent analyses to quantify the accuracy with which
the W-gluon fusion (gq -> t\bar{b}q) and (q\bar{q} -> t\bar{b}) signals can be
extracted from the backgrounds at both the Tevatron and the LHC. Although
perturbation theory breaks down at low transverse momentum for the W-gluon
fusion \bar{b} differential cross section, we show how to obtain a reliable
cross section integrated over low \bar{b} transverse momenta up to a cutoff. We
estimate the accuracy with which V_{tb} can be measured in both analyses,
including theoretical and statistical uncertainties. We also show that the
polarization of the top quark in W-gluon fusion can be detected at the Fermilab
Tevatron and the CERN LHC.


title: The $Z_2\times Z_2$ Orbifold and the SUSY Flavor Problem

abstract:
  The characteristic property of the $Z_2\times Z_2$ orbifold is its cyclic
permutation symmetry. It is argued that this property may be instrumental in
explaining simultaneously the fermion mass hierarchy and the squark mass
degeneracy. Detailed studies in free fermionic models that preserve the cyclic
permutation symmetry of anomalous U(1) charges of the three generations are
discussed.


title: Spinless Salpeter Equation: Analytic Results

abstract:
  The spinless Salpeter equation is the combination of relativistic kinematics
with some static interaction potential. The nonlocal nature of the Hamiltonian
resulting from this approximation renders difficult to obtain rigorous analytic
statements on resulting solutions. In view of this rather unsatisfactory state
of affairs, we calculate analyic upper bounds on the involved energy levels,
and, for the Coulomb potential, on the ground-state energy at the critical
value of the coupling constant.


title: Formation of Black Holes in First Order Phase Transitions

abstract:
  A new mechanism of black hole formation in a first order phase transition is
proposed. In vacuum bubble collisions the interaction of bubble walls leads to
the formation of nontrivial vacuum configuration. The consequent collapse of
this vacuum configuration induces the black hole formation with high
probability. Observational constraints on the spectrum of primordial black
holes allow to obtain new nontrivial restrictions on parameters of inflation
models with first order phase transitions.


title:
Phenomenology, Astrophysics and Cosmology of Theories with
  Sub-Millimeter Dimensions and TeV Scale Quantum Gravity

abstract:
  We recently proposed a solution to the hierarchy problem not relying on
low-energy supersymmetry or technicolor. Instead, the problem is nullified by
bringing quantum gravity down to the TeV scale. This is accomplished by the
presence of $n \geq 2$ new dimensions of sub-millimeter size, with the SM
fields localised on a 3-brane in the higher dimensional space. In this paper we
systematically study the experimental viability of this scenario. Constraints
arise both from strong quantum gravitational effects at the TeV scale, and more
importantly from the production of massless higher dimensional gravitons with
TeV suppressed couplings. Theories with $n>2$ are safe due mainly to the
infrared softness of higher dimensional gravity. For $n=2$, the six dimensional
Planck scale must be pushed above $\sim 30$ TeV to avoid cooling SN1987A and
distortions of the diffuse photon background. Nevertheless, the particular
implementation of our framework within type I string theory can evade all
constraints, for any $n \geq 2$, with string scale $m_s \sim 1$ TeV. We also
explore novel phenomena resulting from the existence of new states propagating
in the higher dimensional space. The Peccei-Quinn solution to the strong CP
problem is revived with a weak scale axion in the bulk. Gauge fields in the
bulk can mediate repulsive forces $\sim 10^6 - 10^8$ times stronger than
gravity at sub-mm distances, and may help stabilize the proton.
Higher-dimensional gravitons produced on our brane and captured on a different
"fat" brane can provide a natural dark matter candidate.


title: A Model of Interacting Partons for Hadronic Structure Functions

abstract:
  We present a model for the structure of baryons in which the valence partons
interact through a linear potential. This model can be derived from QCD in the
approximation where the transverse momenta are ignored. We compare the parton
structure function predicted by our model with a standard global fit to Deep
Inelastic Scattering data. The only parameter we can adjust is the fraction of
the baryon momentum carried by the valence partons. Our prediction agrees well
with data except for small values of the Bjorken scaling variable.


title:
Quark-Gluon Plasma in Pb--Pb 158 A GeV collisions: Evidence from strange
  particle abundances and the Coulomb effect

abstract:
  The hadronic particle production data from relativistic nuclear Pb--Pb 158 A
GeV collisions are successfully described within the chemical non-equilibrium
model, provided that the analysis treats Omega and anti-Omega abundances with
care. We further show that there is a subtle influence of the Coulomb potential
on strange quarks in quark matter which is also seen in our data analysis, and
this Coulomb effect confirms the finding made by chemical analysis in the
S--Au/W/Pb 200 A GeV collisions that the hadron particle source is deconfined
with respect to strange quark propagation. Physical freeze-out conditions
(pressure, specific energy, entropy, and strangeness) are evaluated and
considerable universality of hadron freeze-out between the two different
collision systems is established.


title:
Flavor violation and $\tan{\beta}$ in gauge mediated models with
  messenger-matter mixing

abstract:
  We consider the Minimal Gauge Mediated Model (MGMM) with either fundamental
or antisymmetric messenger multiplets and study consequences of
messenger-matter mixing. We find that in these models, unlike MGMM without
mixing, wide range of $\tan\beta$ is allowed. It is shown that existing
experimental limits on processes with lepton flavor violation, and on
$K^0-\bar{K}^0$, $D^0-\bar{D}^0$ and $B^0-\bar{B}^0$ - mixing place significant
constraints on relevant coupling constants and mixing parameters. On the other
hand, the contributions of the messenger-matter mixing to the rates of $\tau
\to e\gamma$, $\tau \to \mu\gamma$ and $b\to s\gamma$ may be well below the
present experimental limits depending on the value of $\tan\beta$. We also
point out the possibility of sizeable slepton oscillations in this model.


title: Compactification for a Three-Brane Universe

abstract:
  A fully realistic and systematic effective field theory model of a 3-brane
universe is constructed. It consists of a six-dimensional gravitating
spacetime, containing several, approximately parallel (3+1)-dimensional
defects, or ``3-branes''. The Standard Model particles are confined to live on
one of the 3-branes while different four-dimensional field theories may inhabit
the others, in literally a case of ``parallel universes''. The effective field
theory is valid up to the six-dimensional Planck scale, where it must be
replaced by a more fundamental theory of gravity and 3-brane structure. Each
3-brane induces a conical geometry in the two dimensions transverse to it.
Collectively, the curvature induced by the 3-branes can compactify the extra
dimensions into a space of spherical topology. It is possible to take the
six-dimensional Planck scale to be not much larger than the weak scale, and the
compact space not much smaller than a millimeter, thereby realizing the recent
proposal by Arkani-Hamed, Dimopoulos and Dvali for eliminating the Gauge
Hierearchy Problem. In this case, an extra force is required to stabilize the
compact space against collapse. This is provided by a six-dimensional (compact)
U(1) gauge field with a magnetic flux quantum trapped in the compact space. The
nature of the Cosmological Constant Problem in this scenario is discussed.


title:
Probing Higgs Bosons with Large Bottom Yukawa Coupling at Hadron
  Colliders

abstract:
  The small mass of the bottom quark, relative to its weak isospin partner, the
top quark, makes the bottom an effective probe of new physics in Higgs and top
sectors. We study the Higgs boson production associated with bottom quarks,
ppbar/pp to phi+b+bbar to 4b, at the Fermilab Tevatron and the CERN LHC. We
find that strong and model-independent constraints on the size of the
phi-b-bbar coupling can be obtained for a wide range of Higgs boson masses.
Their implications for the composite Higgs models with strong dynamics
associated with the third family quarks (such as the top-condensate/topcolor
models with naturally large bottom Yukawa couplings), and for the
supersymmetric models with large tan(beta), are analyzed. We conclude that the
Tevatron and the LHC can put stringent bounds on these models, if the
phi+b+bbar signal is not found.


title: Higgs-mediated FCNC in Supersymmetic Models with Large $\tan\beta$

abstract:
  In the supersymmetric models with nontrivial flavour structure in the
soft-breaking sector the exchange of neutral Higgses mediates $\Delta F=2$
transitions. This mechanism is studied for $\Delta S, \Delta B=2$ processes and
for a generic form of the soft-breaking terms. We find that Higgs-mediated FCNC
amplitudes increase very rapidly with $\tan\beta$ and can exceed $SUSY$ box
contribution by up to two orders of magnitude when $\tan\beta\sim m_t/m_b$.


title: Self-Consistent Approximations to Non-Equilibrium Many-Body Theory

abstract:
  Within the non-equilibrium Green's function technique on the real time
contour, the Phi-functional method of Baym is reviewed and generalized to
arbitrary non-equilibrium many-particle systems. The scheme may be closed at
any desired order in the number of loops or vertices of the generating
functional. It defines effective theories, which provide a closed set of
coupled classical field and Dyson equations, which are self-consistent,
conserving and thermodynamically consistent. The approach permits to include
unstable particles and therefore unifies the description of resonances with all
other particles, which obtain a mass width by collisions, decays or creation
processes in dense matter. The inclusion of classical fields enables the
treatment of soft modes and phase instabilities. The method can be taken as a
starting point for adequate and consistent quantum improvements of the
in-medium rates in transport theories.


title: Charmonium and lepton pair production with medium energy antiprotons

abstract:
  The medium energy antiproton beam facility which is under discussion at GSI
offers new opportunities to study the QCD of heavy flavours, nuclear structure
and exotic mesons. We discuss these topics and briefly highlight other problems
in charm production and proton structure.


title: Neutrino Mass Textures from Oscillations with Maximal Mixing

abstract:
  We study the implications of neutrino oscillations with maximal mixing for
the neutrino Dirac and Majorana matrices in the see-saw mechanism for three non
degenerate neutrino masses. We find the form of the Dirac matrix for a
structure-less Majorana matrix and, conversely, the structure of the Majorana
matrix if the Dirac matrix is according to our naive intuition. We give some
examples of Majorana matrices that, in a 3 X 3 context, lead to maximal mixing
without too much fine tuning and cross talk with the Dirac input.


title: Lifetimes of doubly charmed baryons: $\Xi_{cc}^{+}$ and $\Xi_{cc}^{++}$

abstract:
  We have performed a detailed investigation of total lifetimes for the
$\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$ baryons in the framework of operator product
expansion over the inverse mass of charmed quark, whereas, to estimate matrix
elements of operators obtained in OPE, some approximations of nonrelativistic
QCD are used. This approach allows one to take into account the corrections to
the spectator decays of $c$-quarks, which reflect the fact, that these quarks
are bound, as well as the contributions, connected to the effects of both the
Pauli interference for the $\Xi_{cc}^{++}$-baryon and the weak scattering for
the $\Xi_{cc}^{+}$-baryon. The realization of such program leads to the
following estimates for the total lifetimes of doubly charmed baryons:
$\tau_{\Xi_{cc}^{++}}=0.43\pm 0.1~ps$ and $\tau_{\Xi_{cc}^{+}}=0.11\pm
0.01~ps$.


title:
Phenomenological Analysis of Data on Inclusive and Semi-inclusive Spin
  Asymmetries

abstract:
  We present a phenomenological analysis of data on both inclusive and
semi-inclusive spin asymmetries. We examine the impact of the semi-inclusive
results presented by SMC on the determination of polarized parton distributions
performing global fits with different sets of observables. We discuss the
flavour dependence of the polarized sea inside a nucleon.


title: Effective Lagrangians in $2 + \epsilon$ Dimensions

abstract:
  The failure of the the loop expansion and effective lagrangians in two
dimensions, which traditionally hinges on a power counting argument is
considered. We establish that the book keeping device for the loop expansion, a
role played by (the reciprocal of) the pion-decay constant itself vanishes for
$d=2$, thereby going beyond the power counting argument. We point the
connection of our results to the distinct phases of the candidate for the
effective lagrangians, the non-linear sigma model, in $d=2+\epsilon$, and
eventually for $d=2$. In light of our results, we recall some of the relavant
features of the multi-flavor Schwinger and large $N_f$ $QCD_2$ as candidates
for the underlying theory in $d=2$.


title: On the instanton-induced portion of the nucleon strangeness

abstract:
  We calculate the instanton contribution to the proton strangeness in the MIT
bag enriched by the presence of a dilute instanton liquid. The evaluation is
based on expressing the nucleon matrix elements of bilinear strange quark
operators in terms of a model valence nucleon state and interactions producing
quark-antiquark fluctuations on top of that valence state. Our method combines
the usage of the evolution operator containing a strangeness source, and the
Feynman-Hellmann theorem. It enables one to evaluate the strangeness in
different Lorentz channels in, essentially, the same way. Only the scalar
channel is found to be affected by the interaction induced by the random
instanton liquid.


title: Off-Forward Parton Distributions

abstract:
  Recently, there have been some interesting developments involving off-forward
parton distributions of the nucleon, deeply virtual Compton scattering, and
hard diffractive vector-meson production. These developments are triggered by
the realization that the off-forward distributions contain information about
the internal spin structure of the nucleon and that diffractive
electroproduction of vector mesons depends on these unconventional
distributions. This paper gives a brief overview of the recent developments.


title: Problems with Atmospheric Neutrino Oscillations

abstract:
  The neutrino oscillation hypothesis does a poor job of representing the
atmospheric neutrino anomaly. The anomaly is observed over 4 decades in path
length and at least a factor of 30 in energy. This restricts the potential
oscillation solutions to those with large amplitudes and mixing mass
differences that are ruled out by other observations. The $\Delta m^{2}$ region
in the range $10^{-4} - 10^{-2}$ leads to inconsistencies within the
atmospheric neutrino data itself. The observed value of $R$ seems to be
incompatible with the $\Delta m^{2}$ implied by recent results


title:
Solar neutrino interactions: Using charged currents at SNO to tell
  neutral currents at Super-Kamiokande

abstract:
  In the presence of flavor oscillations, muon and tau neutrinos can contribute
to the Super-Kamiokande (SK) solar neutrino signal through the neutral current
process \nu_{\mu,\tau} e^{-}\to \nu_{\mu,\tau} e^{-}. We show how to separate
the \nu_e and \nu_{\mu,\tau} event rates in SK in a model independent way, by
using the rate of the charged current process \nu_e d \to p p e^{-} from the
Sudbury Neutrino Observatory (SNO) experiment, with an appropriate choice of
the SK and SNO energy thresholds. Under the additional hypothesis of no
oscillations into sterile states, we also show how to determine the absolute
^{8}B neutrino flux from the same data set, independently of the \nu_e survival
probability.


title:
Finite dimensional systems with random external fields and Neutrino
  propagation in fluctuating media

abstract:
  We develop the general formalism for the study of neutrino propagation in
presence of stochastic media. This formalism allows the systematic derivation
of evolution equations for averaged quantities as survival probabilities and
higher order distribution moments. The formalism applies equally to any finite
dimensional Schroedinger equation in presence of a stochastic external force.
New integro-differential equations valid for finite correlated processes are
obtained for the first time. For the particular case of exponentially
correlated processes a second order ordinary equation is obtained. As a
consequence, the Redfield equation valid for Gaussian delta-correlated noise is
rederived in a simple way. The formalism, together with the quantum correlation
theorem is applied to the computation of higher moments and correlation
functions of practical interest in forthcoming high precision neutrino
experiments. It is shown that equal and not equal time correlators follow
similar differential equations.


title:
QCD at high Baryon Density and Temperature: Competing Condensates and
  the Tricritical Point

abstract:
  The phase diagram of strongly interacting matter is explored as a function of
temperature and baryon number density. We investigate the possible simultaneous
formation of condensates in the conventional quark--anti-quark channel
(breaking chiral symmetry) and in a quark--quark channel leading to color
superconductivity: the spontaneous breaking of color symmetry via the formation
of quark Cooper pairs. We point out that for two massless quark flavors a
tricritical point in the phase diagram separates a chiral symmetry restoring
first order transition at high densities from the second order transition at
high temperatures. Away from the chiral limit this tricritical point becomes a
second order phase transition with Ising model exponents, suggesting that a
long correlation length may develop in heavy ion collisions in which the phase
transition is traversed at the appropriate density.


title: Constraints on Axion Models from $K^+\to\pi^+ a$

abstract:
  We explore a new class of axion models in which some, but not all, of the
left-handed quarks have a Peccei-Quinn symmetry. These models are potentially
afflicted by flavour changing neutral currents. We derive the bounds on the
Peccei-Quinn symmetry-breaking scale from bounds on the $K^+\to \pi^+ a$
branching ratio, showing that in some cases they are even stronger than the
astrophysical ones, but still not strong enough to kill off the models.


title: New CP-violating parameters in cascade decays

abstract:
  We consider decay chains of the type P -> M + ... -> f + ..., where M is a
neutral meson that may mix with its antiparticle Mbar, before decaying into the
final state f. P may be either a heavier neutral meson or a charged meson. We
perform a rephasing-invariant analysis of the quantities that show up in such
cascade decays. If the decay P -> M + ... (or the decay P -> Mbar + ...) is
forbidden, we find the usual lambda_f parameters describing the interference
between the mixing of a neutral meson system and the decay from that system
into the final state f. However, when both the P -> M + ... and P -> Mbar + ...
decays are allowed, we find a new class of rephasing-invariant parameters,
xi_i, that measure the interference between the mixing of a neutral meson
system and the decay from the initial state *into that system*. We show that
the quantities lambda_f and xi_i are necessary and sufficient to describe all
the interference effects present in the most general cascade decay. We discuss
the various cascade decays in turn, highlighting the special features of each
one.


title: Phenomenological Study of Excited Baryons

abstract:
  We study baryon excited states for quark confinement and chiral symmetry
breaking. In the first part we discuss spatially deformed baryon excitations.
As signals of deformation, we study masses and electromagnetic transitions.
Such a study of spatial structure is expected to provide information on quark
binding mechanism and hence quark confinement. In the second part, we consider
the chiral symmetry for baryons and study positive and negative parity baryons.
We show that there are two distinctive representations of chiral symmetry for
baryons. We investigate their phenomenological consequences in terms of linear
sigma models.


title: Single spin asymmetries and vector meson production in DIS

abstract:
  We discuss possible measurements and origins of single spin asymmetries in
DIS and of some unusual spin properties of vector mesons produced in lepton-
nucleon, photon-nucleon and photon-photon interactions. Such effects have
already been observed in other processes.


title:
Mixing and decay constants of pseudoscalar mesons: Octet-singlet vs.
  quark flavor basis

abstract:
  Although eta-eta' mixing is qualitatively well understood as a consequence of
the U(1)_A anomaly in QCD together with a broken SU(3) flavor symmetry, until
recently the values of decay and mixing parameters of the eta and eta' were
only approximately known, e.g. values for the octet-singlet mixing angle
between -20 degrees and -10 degrees could be found in the literature. New
experimental data, especially for the reactions gamma gamma* -> eta, eta' and B
-> eta' K, together with new theoretical results from higher order corrections
in chiral perturbation theory stimulated a phenomenological re-analysis of this
subject, which led to a coherent qualitative and quantitative picture of
eta-eta' mixing and even of eta-eta'-eta_c mixing.


title:
Dynamical symmetry restoration for a higher-derivative four-fermion
  model in an external electromagnetic field

abstract:
  A four-fermion model with additional higher-derivative terms is investigated
in an external electromagnetic field. The effective potential in the leading
order of large-N expansion is calculated in external constant magnetic and
electric fields.
  It is shown that, in contrast to the former results concerning the universal
character of "magnetic catalysis" in dynamical symmetry breaking, in the
present higher-derivative model the magnetic field restores chiral symmetry
broken initially on the tree level. Numerical results describing a second-order
phase transition that accompanies the symmetry restoration at the quantum level
are presented.


title: DIS'98 Structure Functions Summary, Part II

abstract:
  Recent results presented in the structure functions working group are briefly
summarized for the following topics: The theoretical treatment of heavy quarks
in structure functions, higher-order corrections for the leading-twist
evolution (including small-x resummations), the present status of the proton's
parton densities, and the impact of higher twists on determinations of the
strong coupling constant. The reader is referred to Part I for accounts of the
transition to the photoproduction region, pion and photon structure results,
and high-Q^2 phenomena.


title: Green's Functions for Neutrino Mixing

abstract:
  The Green's function formalism for neutrino mixing is presented and the exact
oscillation formula is obtained. The usual Pontecorvo formula is recovered in
the relativistic limit.


title: Neutrino Spin Flavour Precession in Fluctuating Solar Magnetic Fields

abstract:
  The effect of a random magnetic field in the convective zone of the Sun on
resonant neutrino spin oscillations, i.e. transitions of the type
$\nu_{eL}\to\tilde\nu_{\mu R}$, is considered. The average survival probability
and the expected experimental signals in the existing solar neutrino
experiments are computed as a function of the level of the noise and magnitude
of a constant magnetic field in the convective zone. From comparison with
observed detection rates we conclude that the RSFP solutions to the SNP with
negligible mixing angle are stable under the presence of low or moderate levels
of noise. Detection rates, specially in the Homestake experiment, are however
sensitive to large levels of noise. As a consequence, an upper limit on small
scale magnetic fluctuations is obtained from the combined solar data:
$\surd\langle B^2\rangle< 140-200 $ kG for the scale $L_0\sim 1000 $ km and
transition moment $\mu=10^{-11} \mu_B$.


title: Constraints on Axion Models

abstract:
  Two particular classes of axion models are presented, each one yielding a
lower bound on the axion decay constant, based though on different
considerations. In the first class only some, and not all, of the right-handed
quarks have PQ charges, whereas in the second one the left-handed sector of the
same quarks is taken into account as well. In the first case we find that
bounds coming from astrophysics are significantly relaxed compared with those
for the DFSZ. As for the second class, the astrophysical constraints proved to
be less severe (with one exception), than those coming from FCNC processes.


title: Signals of R-Parity Violation at a Muon Collider

abstract:
  We investigate the effects of R-parity-violating $LL\bar E$ and $LQ\bar D$
operators on the production of fermion pairs at a $\mu^+ \mu^-$ collider with
high energy and luminosity. We show that comparison of angular distributions
leads to useful discovery limits for the R-parity-violating couplings,
especially if the exchanged sfermions turn out to be heavy. Products of these
couplings can also be probed well beyond present experimental limits,
especially for the second and third generations. Finally, we compare results at
a muon collider with those obtainable from an $e^+ e^-$ linear collider with
similar energy and luminosity.


title: Studies of the motion and decay of axion walls bounded by strings

abstract:
  We discuss the appearance at the QCD phase transition, and the subsequent
decay, of axion walls bounded by strings in N=1 axion models. We argue on
intuitive grounds that the main decay mechanism is into barely relativistic
axions. We present numerical simulations of the decay process. In these
simulations, the decay happens immediately, in a time scale of order the light
travel time, and the average energy of the radiated axions is $<\omega_a >
\simeq 7 m_a$ for $v_a/m_a \simeq 500$. $<\omega_a>$ is found to increase
approximately linearly with $\ln(v_a/m_a)$. Extrapolation of this behaviour
yields $<\omega_a> \sim 60 m_a$ in axion models of interest. We find that the
contribution to the cosmological energy density of axions from wall decay is of
the same order of magnitude as that from vacuum realignment, with however large
uncertainties. The velocity dispersion of axions from wall decay is found to be
larger, by a factor $10^3$ or so, than that of axions from vacuum realignment
and string decay. We discuss the implications of this for the formation and
evolution of axion miniclusters and for the direct detection of axion dark
matter on Earth. Finally we discuss the cosmology of axion models with $N>1$ in
which the domain wall problem is solved by introducing a small U$_{PQ}$(1)
breaking interaction. We find that in this case the walls decay into
gravitational waves.


title:
Spectroscopy of doubly charmed baryons: $\Xi_{cc}^{+}$ and
  $\Xi_{cc}^{++}$

abstract:
  Using the quark-diquark approximation in the framework of Buchm\" uller-Tye
potential model, we investigate the spectroscopy of doubly charmed baryons:
$\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$. Our results include the masses, parameters
of radial wave functions of states with the different excitations of both
diquark and light quark-diquark system. We calculate the values of fine and
hyperfine splittings of these levels and discuss some new features, connected
to the identity of heavy quarks, in the dynamics of hadronic and radiative
transitions between the states of these baryons.


title: A New Cosmological Paradigm: the Cosmological Constant and Dark Matter

abstract:
  The Standard Cosmological Model of the 1980's is no more. I describe the
definitive evidence that the density of matter is insufficient to result in a
flat universe, as well as the mounting evidence that the cosmological constant
is not zero. I finally discuss the implications of these results for particle
physics and direct searches for non-baryonic dark matter, and demonstrate that
the new news is good news.


title:
CP Violating Lepton Asymmetries from B Decays and Their Implication for
  Supersymmetric Flavor Models

abstract:
  The lepton and dilepton charge asymmetries from $B_{d}$ and $B_{s}$ are
predicted to be small in the standard model, whereas new physics could increase
their values significantly. In this paper, we explore the use of the lepton
asymmetries as a probe of the flavor structure of supersymmetric theories. In
particular, we determine the sensitivity to parameters of various models. We
find that in many interesting models which attempt to address the
supersymmetric flavor problem, the mixing structure is such that it could be
possible to detect new physics. The predictions are model dependent; with a
measurement in both the $B_s$ and $B_d$ systems one can hope to constrain the
flavor physics model, especially once squarks are detected and their masses
measured. Thus, lepton charge asymmetries can be used as an alternative means
of searching for new physics and distinguishing among potential solutions to
the flavor problem. They are interesting precisely because they are small in
the standard model and are therefore necessarily evidence of new physics.


title: Non-factorizable contributions in hadronic weak decays of charm mesons

abstract:
  Two body decays of charm mesons are studied by describing their amplitude in
terms of a sum of factorizable and non-factorizable ones. The former is
estimated by using a naive factorization while the latter is calculated by
using a hard pseudo-scalar-meson approximation. The hard pseudo-scalar-meson
amplitude is given by a sum of the so-called equal-time commutator term and
surface term which contains all possible pole contributions of various mesons,
not only the ordinary $\{q\bar q\}$ but also four-quark $\{qq\bar q\bar q\}$,
hybrid $\{q\bar qg\}$ and glue-balls.
  Naively factorized amplitudes for the spectator decays which lead to too big
rates can interfere destructively with exotic meson pole amplitudes and the
total amplitudes can reproduce their observed rates. The non-factorizable
contributions can supply sufficiently large contributions to the color
suppressed decays which are strongly suppressed in the naive factorization. A
possible solution to the long standing puzzle that the ratio of decay rates for
$D^0\to K^+K^-$ to $D^0\to \pi^+\pi^-$ is around 2.5 is given by different
contributions of exotic meson poles.


title:
Beamstrahlung induced Minijet Backgrounds at future colliders and a
  model for sigma^{inel}_{\gamma \gamma}

abstract:
  The phenomenon of beamstrahlung can give rise to potentially dangerous
hadronic backgrounds due to minjet production at the future linear colliders as
well as at the \gamma \gamma colliders that are under consideration. In this
talk I will review briefly the current estimates of these backgrounds and
predictions of the eikonalised minijet model for \siginel. I end by pointing
out issues that need to be studied in more detail to firm up our estimates of
these backgrounds.


title:
Field Strength Correlator and an Infrared Fixed Point of the Wilsonian
  Exact Renormalization Group Equations

abstract:
  The correlator of two field strengths is computed from an effective action
for Yang Mills theories, which contains both gluons and an auxiliary
antisymmetric tensor field for the field strength as local variables. This
action allows to relate explicitly many different approaches to confinement,
and is computed using Wilsonian renormalization group equations with the bare
Yang Mills action as starting point. Due to the inclusion of a higher
dimensional operator in the ghost sector the running gauge coupling becomes
vanishingly small at a critical scale k_c, and the resulting low energy action
resembles the action of a confining string theory proposed by Polyakov.


title:
WEXTER and ERAFITTER: two programs to fit M_W at LEP2 using the best
  measurable kinematical variables

abstract:
  In this paper, we present two programs to fit M_W at LEP2 using the best
measurable kinematical variables. The theoretical probabilities of observing
the final-state kinematical configurations are computed by integrating over the
quantities that are not well measured. Therefore, an event-by-event kinematical
reconstruction is avoided. M_W is then determined through a maximum likelihood
fit.


title:
Bose-Einstein condensation and independent emission: statistical physics
  interpretation

abstract:
  Recent results on effects of Bose-Einstein symmetrization in a system of
independently produced particles are interpreted in terms of statistical
physics. For a large class of distributions, the effective sizes of the system
in momentum and in configuration space are shown to shrink when quantum
interference is taken into account.


title: Long-Range Interactions of Small Color Dipoles

abstract:
  We study the scattering of small color dipoles (e.g., heavy quarkonium
states) at low energies. We find that even though the couplings of color
dipoles to the gluon field can be described in perturbation theory, at large
distances the interaction becomes totally non--perturbative. The structure of
the scattering amplitude, however, is fixed by the (broken) chiral and scale
symmetries of QCD; the leading long--distance contribution arises from the
correlated two--pion exchange. We use the spectral representation technique to
evaluate both perturbative and non-perturbative contributions to the scattering
amplitude. Our main result is the sum rule which relates the overall strength
of the non--perturbative interaction between color dipoles to the energy
density of QCD vacuum.


title:
On the absence of fifth-order contributions to the nucleon mass in
  heavy-baryon chiral perturbation theory

abstract:
  (New version with some expanded discussion; figures and minor typos
corrected.)
  We have calculated the contribution proportional to the fifth power of the
pion mass in the chiral expansion of the nucleon mass in two flavour HBCPT.
Only one irreducible two-loop integral enters, and this vanishes. All other
corrections in the heavy-baryon limit can be absorbed in the physical
pion-nucleon coupling constant which enters in the third order term, and so
there are no contributions at fifth order. Including finite nucleon mass
corrections, the only contribution agrees with the expansion of the
relativistic one-loop graph in powers of the ration of the pion and nucleon
masses, and is only 0.3% of the third order term. This is an encouraging result
for the convergence of two-flavour heavy-baryon chiral perturbation theory.


title:
Worldline Approach to Forward and Fixed Angle fermion-fermion Scattering
  in Yang-Mills Theories at High Energies

abstract:
  Worldline techniques are employed to study the general behaviour of the
fermion-fermion collision amplitude at very high energies in a non-abelian
gauge field theory for the forward and fixed angle scattering cases. A central
objective of this work is to demonstrate the simplicity by which the worldline
methodology isolates that sector of the full theory which carries the soft
physics, relevant to each process. Anomalous dimensions pertaining to a given
soft sector are identified and subseuently used to facilitate the
renormalization group running of the respective four point functions. Gluon
reggeization is achieved for forward, while Sudakov suppression is established
for fixed angle scattering.


title:
Dynamical Neutrino Mass Matrix: Large (Small) Mixing Solution to
  Atmospheric (Solar) Neutrino Oscillations

abstract:
  In the wake of the SuperKamiokande announcement of atmospheric neutrino
oscillations which favor the large mixing of $\nu_\mu$ with $\nu_\tau$, there
is considerable theoretical activity towards a possible understanding of the
solar neutrino deficit also in terms of the mixing of $\nu_e$ with the other
two neutrinos. A specific dynamical model is presented here for the first time
which naturally chooses the large (small) mixing solution to atmospheric
(solar) neutrino oscillations.


title: Hybrid Baryons in Large-N_c QCD

abstract:
  We study the properties and couplings of hybrid baryons in the large-$N_c$
expansion. These are color-neutral baryon states which contain in addition to
$N_c$ quarks also one constituent gluon. Hybrid baryons with both symmetric and
mixed symmetric orbital wave functions are considered. We introduce a Hartree
description for these states, similar to the one used by Witten for ordinary
baryons. It is shown that the Hartree equations for $N_c (N_c-1)$ quarks for
symmetric (mixed symmetric) states in these states coincide with those in
ordinary baryons in the large-$N_c$ limit. The energy due to the gluon field is
of order $\Lambda_{QCD}$. Under the assumption of color confinement, our
results prove the existence of hybrid baryons made up of heavy quarks in the
large $N_c$ limit and provides a justification for the constituent gluon
picture of these states. The couplings of the hybrid baryons to mesons of
arbitrary spin are computed in the quark model. Using constraints from the
large $N_c$ scaling laws for the meson-baryon scattering amplitudes, we write
down consistency conditions for the meson couplings of the hybrid baryons.
These consistency conditions are solved explicitly with results in agreement
with those in the quark model for the respective couplings.


title:
Open Charm, Photon and Dilepton Production in an Increasingly Strongly
  Interacting Parton Plasma

abstract:
  We examine the effects of the new equilibration scenario of the increasingly
strongly interacting parton plasma and of the non-equilibrium environment have
on the production of open charm, photon and dilepton at LHC and at RHIC
energies. We show that an out-of-equilibrium effect, not shown before, changes
significantly the relative yield of the two main partonic contributions to
photon production in the higher $p_T$ range, and higher orders for
electromagnetic emissions have increased significance in the new scenario
especially at RHIC energies. We argue that the effects of the new scenario are
not restricted just to the parton phase but will continue through to the later
hadron gas phase with potentially positive implications for the detection of
the quark-gluon plasma.


title: The DLLA limit of BFKL in the Dipole Picture

abstract:
  In this work we obtain the DLLA limit of BFKL in the dipole picture and
compare it with HERA data. We demonstrate that in leading-logarithmic-
approximation, where $\alpha_s$ is fixed, a transition between the BFKL
dynamics and the DLLA limit can be obtained in the region of $Q^2 \approx 150
GeV^2$. We compare this result with the DLLA predictions obtained with
$\alpha_s$ running. In this case a transition is obtained at low $Q^2$ $(\le 5
GeV^2)$. This demonstrates the importance of the next-to-leading order
corrections to the BFKL dynamics. Our conclusion is that the $F_2$ structure
function is not the best observable for the determination of the dynamics,
since there is great freedom in the choice of the parameters used in both BFKL
and DLLA predictions.


title:
Gauge Mediated Supersymmetry Signals at the Tevatron Involving Tau
  Leptons

abstract:
  We consider the phenomenology of GMSB models where the lighter stau is the
next to lightest supersymmetric particle. In this situation the dominant
signals for supersymmetry at the Tevatron are events where two or three high
p_T tau leptons accompanied by large missing transverse energy are produced.
This leads to signatures that are very different from the photonic signals for
GMSB (where the lightest neutralino is the NLSP) and the dilepton and trilepton
signals in the usual supergravity models (involving e and/or mu only) that have
been investigated extensively. We find that the inclusive 2 tau-jet signature
could be observable at the Tevatron Run II, while the inclusive 3 tau-jet
signature could be important at Run III.


title: Determination of the scalar glueball mass in QCD sum rules

abstract:
  The $0^{++}$ glueball mass is analyzed in the QCD sum rules. We show that in
order to determine the $0^{++}$ glueball mass by using the QCD sum rules
method, it is necessary to clarify the following three ingredients: (1) to
choose the appropriate moment with acceptable parameters which satisfy all of
the criteria; (2) to take account into the radiative corrections; (3) to
estimate an additional contribution to the glueball mass from the lowest lying
${\bar q}q$ resonance. We conclude that it is the key point to choose suitable
moments to determine the $0^{++}$ glueball mass, the radiative corrections do
not affect it sensitively and the composite resonance have a little effect on
it.


title: Unified derivation of evolution equations

abstract:
  We derive the evolution equations of parton distribution functions
appropriate in different kinematic regions in a unified and simple way using
the resummation technique. They include the
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation for large momentum transfer
$Q$, the Balitskii-Fadin-Kuraev-Lipatov equation for a small Bjorken variable
$x$, and the Ciafaloni-Catani-Fiorani-Marchesini equation which embodies the
above two equations. The relation among these equations is explored, and
possible applications of our approach are proposed.


title: Exclusive charmless $B_s$ hadronic decays into $\eta'$ and $\eta$

abstract:
  Using the next-to-leading order QCD-corrected effective Hamiltonian,
charmless exclusive nonleptonic decays of the $B_s$ meson into $\eta$ or
$\eta'$ are calculated within the generalized factorization approach.
Nonfactorizable contributions, which can be parametrized in terms of the
effective number of colors $N_c^{\rm eff}$ for $P P$ and $V P$ decay modes, are
studied in two different schemes: (i) the one with the "homogeneous" structure
in which $(N_c^{\rm eff})_1 \approx (N_c^{\rm eff})_2 \approx ... \approx
(N_c^{\rm eff})_{10}$ is assumed, and (ii) the "heterogeneous" one in which the
possibility of $N_c^{\rm eff}(V+A) \neq N_c^{\rm eff}(V-A)$ is considered,
where $N_c^{\rm eff}(V+A)$ denotes the effective value of colors for the
$(V-A)(V+A)$ penguin operators and $N_c^{\rm eff}(V-A)$ for the $(V-A)(V-A)$
ones. For processes depending on the $N_c^{\rm eff}$-stable $a_i$ such as
$\bar{B_s} \to (\pi,\rho) (\eta^{'},\eta)$, the predicted branching ratios are
not sensitive to the factorization approach we choose. While for the processes
depending on the $N_c^{\rm eff}$-sensitive $a_i$ such as $\bar{B_s} \to \omega
\eta^{(')}$, there is a wide range for the branching ratios depending on the
choice of the $N_c^{\rm eff}$ involved. We have included the QCD anomaly effect
in our calculations and found that it is important for $\bar{B_s} \to
\eta^{(')} \eta^{(')}$. The effect of the $(c\bar c) \to \eta'$ mechanism is
found to be tiny due to a possible CKM-suppression and the suppression in the
decay constants except for the $\bar{B_s} \to \phi \eta$ decay within the
"naive" factorization approach, where the internal $W$ diagram is
CKM-suppressed and the penguin contributions are compensated.


title:
SU(3) Breaking in Hyperon Beta Decays: a Prediction for Xi0 -> Sigma+ e
  anti-neutrino

abstract:
  SU(3) breaking in hyperon semi-leptonic decays is discussed. The SU(3)
parameters $F$ and $D$, relevant to the ``proton-spin puzzle'', are extracted
and a prediction is presented for the decay Xi0 -> Sigma+ e anti-neutrino,
currently under study by the KTeV collaboration. The values found are g1/f1 =
1.16+/-0.03+/-0.01 and Gamma = (0.80+/-0.03+/-0.01) x 10^6 s^-1.


title: The low-energy constants of the pion-nucleon system

abstract:
  Recent analyses of low-energy pion-nucleon experimental data have provided
clear evidence for the violation of the isospin symmetry of the strong
interaction. In the present work, it is shown that the single-charge-exchange
reaction is the culprit for the effect. Given the present experimental
uncertainties, no evidence for isospin breaking was found in the two
elastic-scattering processes for pion laboratory kinetic energies between 20
and 100 MeV. In agreement with most of the recent determinations, the value for
the charged-pion coupling constant, extracted herein, is `small'. The energy
dependence of the s- and p-wave hadronic phase shifts, obtained from low-energy
elastic-scattering data exclusively, as well as their values in tabular form
(including meaningful uncertainties), are provided. Discrepancies with two
`standard' phase-shift solutions in the s-wave part of the interaction are
seen; small differences may be observed in three of the p-wave channels.


title: Quark energy loss in an expanding quark-gluon plasma

abstract:
  We study the quark energy loss in an expanding quark-gluon plasma. The
expanding plasma produced in high energy AA-collision is described by Bjorken's
model. The dependence of the energy loss on the infrared cutoff for the
radiated gluons, on the quark mass, and on the initial conditions of QCD plasma
is investigated.


title: Real Compton Scattering at High Transverse Momentum Transfer

abstract:
  We discuss the physics motivation for a program of Real Compton Scattering on
the proton in the regime where both the incident energy and the transverse
momentum transfer are large. It is shown that such a program can test which of
the various hard scattering mechanisms is dominant and can allow a measurement
of a new generalized form factor that is sensitive to both the flavor and spin
structure of the proton. It is further shown that the measurements are
experimentally feasible using existing or already planned equipment up to
incident energies of 12 GeV.


title: Possible large direct CP asymmetry in hadronic B+- -> \pi+- \eta' decays

abstract:
  We calculate the branching ratio and direct CP asymmetry in nonleptonic two
body B decays B^+- ->\pi^+- \eta'. It is shown that the tree diagram and gluon
fusion mechanism via penguin diagram have comparable contributions to these
decays which, as a result, could provide an interesting venue for investigating
CP violation. Our estimate shows that the direct CP asymmetry in the above
decays could be as large as 75% which along with a branching ratio B(B^-
->\pi^- \eta')=3.4 X 10^{-6} should be accessible to experiment in the near
future.


title: Soft Superweak CP Violation and the Strong CP Puzzle

abstract:
  We discuss a class of models in which CP is violated softly in a heavy sector
adjoined to the standard model. Heavy-sector loops produce the observed CP
violation in kaon physics, yielding a tiny and probably undetectable value for
$\epsilon^\prime$. All other CP-violating parameters in the effective
low-energy standard model, including the area of the unitarity triangle and
$\bar\theta$, are finite, calculable and can be made very small. The leading
contribution to $\bar\theta$ comes from a four-loop graph. These models offer a
natural realization of superweak CP violation and can resolve the strong CP
puzzle. In one realization of this idea, CP is violated in the mass matrix of
heavy majorana neutrinos.


title: Scalar Glueball Mixing and Decay

abstract:
  We provide the first explanation of the counter-intuitive scalar glueball
couplings to pseudoscalar mesons found in lattice QCD and predict hitherto
uncalculated decay modes. Significant a_1 pi and (pi pi)_S (pi pi)_S couplings
are found. We demonstrate the equivalence of linear and quadratic mass matrices
for glueball-quarkonium mixing. The equivalence of formalisms which deal with a
glueball-quarkonium basis and only a quarkonium basis is demonstrated. We show
that the f_0(1500) is not the heaviest state arising from glueball-quarkonium
mixing for a glueball mass consistent with lattice QCD. The masses and
couplings of scalar mesons, as well as their valence content, are calculated.


title:
Symmetric and Antisymmetric Spin-Orbit Forces in YN Interaction by a
  Quark Model

abstract:
  The symmetric and antisymmetric spin-orbit forces (SLS and ALS) in the YN
interaction are investigated for relative P-wave systems by a valence quark
model with the instanton-induced interaction (III). The size of the adiabatic
potential at the zero range is shown for each of the YN channels. The nonlocal
RGM potential of the LS and ALS forces are also shown for typical YN channels.
The size of ALS is comparable to SLS. The channel dependence of ALS, which is
determined by the flavor SU(3) symmetry when the one-gluon exchange (OGE)
and/or the meson exchange interaction are used, deviates after introducing III.
In most of the two-baryon channels, including the two-nucleon channel, the
spin-orbit force of the YN interaction is strong. A few exceptional channels,
however, are found where III and OGE are canceled to each other, and the
spin-orbit force becomes small.


title: Resolved Photon Processes

abstract:
  After giving a very brief introduction to the resolved photon processes, I
will summarise the latest experimental information from HERA, on resolved
photon contribution to large pt jet production as well as to direct photon
production. I will point out the interesting role that resolved photon
processes can play in increasing our understanding of the dynamics of the
Quarkonium production. I will then discuss the newer information on the parton
content of virtual photons as well as the kt distribution of the partons in the
photon. I will end by giving predictions of an eikonalised minijet model for
siggg which crucially uses the experimental measurement of the abovementioned
kt distribution and comparing them with data.


title: Realizations of Thermal Supersymmetry

abstract:
  We investigate realizations of supersymmetry at finite temperature in terms
of thermal superfields, in a thermally constrained superspace: the Grassmann
coordinates are promoted to be time-dependent and antiperiodic, with a period
given by the inverse temperature. This approach allows to formulate a
Kubo-Martin-Schwinger (KMS) condition at the level of thermal superfield
propagators. The latter is proven directly in thermal superspace, and is shown
to imply the correct (bosonic and fermionic) KMS conditions for the component
fields. In thermal superspace, we formulate thermal covariant derivatives and
supercharges and derive the thermal super-Poincar\'e algebra. Finally, we
briefly investigate field realizations of this thermal supersymmetry algebra,
focussing on the Wess-Zumino model. The thermal superspace formalism is used to
characterize the breaking of global supersymmetry at finite temperature.


title:
Single Meson Photoproduction via Higher Twist Mechanism and IR
  Renormalons

abstract:
  Single pseudoscalar and vector mesons hard semi-inclusive photoproduction
$\gamma h \to MX" via higher twist (HT) mechanism is calculated using the QCD
running coupling constant method. The structure of infrared renormalon
singularities of the HT subprocess cross section and the Borel sum for it are
found. The problem of normalization of HT process cross section in terms of the
meson elm form factor is discussed.


title:
Photoproduction of Heavy Quarks in Next-to-Leading Order QCD with
  Longitudinally Polarized Initial States

abstract:
  We present all relevant details of our calculation of the complete
next-to-leading order (O(alpha_s^2 alpha)) QCD corrections to heavy flavor
photoproduction with longitudinally polarized point-like photons and hadrons.
In particular we provide analytical results for the virtual plus soft gluon
cross section. We carefully address the relevance of remaining theoretical
uncertainties by varying, for instance, the factorization and renormalization
scales independently. Such studies are of importance for a meaningful first
direct determination of the polarized gluon density Delta g from the total
charm production spin asymmetry by the upcoming COMPASS experiment. It is shown
that the scale uncertainty is considerably reduced in next-to-leading order,
but the dependence on the charm quark mass is sizable at fixed target energies.
Finally, we study several differential single-inclusive heavy quark
distributions and, for the polarized HERA option, the total bottom spin
asymmetry.


title: Saturating the Bound on the Scale of Fermion Mass Generation

abstract:
  Recently, Jaeger and Willenbrock have shown that the Appelquist and Chanowitz
bound on the scale of top-quark mass generation can formally be saturated in a
particular limit of a two-Higgs doublet model. In this note I present an
alternate derivation of their result. I perform a coupled channel analysis for
f fbar to V_L V_L and V_L V_L to V_L V_L scattering and derive the conditions
on the parameters required for f fbar to V_L V_L scattering to be relevant to
unitarity. I also show that it is not possible to saturate the bound on fermion
mass generation in the two-Higgs model while maintaining tree-level unitarity
in Higgs scattering at high energies.


title:
Comment on Octet Baryon Magnetic Moments in the Chiral Quark Model with
  Configuration Mixing

abstract:
  The importance of exchange currents, and of conserving isotopic spin at both
the quark and baryon levels in application of the chiral quark model to any
calculation of baryon magnetic moments is emphasized.


title:
Chiral Phase Transition of QCD at Finite Temperature and Density from
  Schwinger-Dyson Equation

abstract:
  We study the chiral phase transition of QCD at finite temperature and density
by numerically solving Schwinger-Dyson equation for the quark propagator with
the improved ladder approximation in the Landau gauge. Using the solution we
calculate a pion decay constant from a generalized version of Pagels-Stokar
formula. Chiral phase transition point is determined by analyzing an effective
potential for the quark propagator. We find solutions for which chiral symmetry
is broken while the value of the effective potential is larger than that for
the chiral symmetric vacuum. These solutions correspond to meta-stable states,
and the chiral symmetric vacuum is energetically favored. We present a phase
diagram on the general temperature--chemical potential plane, and show that
phase transitions are of first order in wide range.


title: Cascade decays of triplet Higgs bosons at LEP2

abstract:
  We study the Georgi-Machacek two triplet, one doublet model in the context of
LEP2, and show that cascade decays of Higgs bosons to lighter Higgs bosons and
a virtual vector boson may play a major role. Such decays would allow the Higgs
bosons of this model to escape current searches, and in particular are of great
importance for the members of the five-plet which will always decay to the
three-plet giving rise to cascade signatures.


title: MSSM with Large tan$\beta$ Constrained by Minimal SO(10) Unification

abstract:
  Study of the MSSM in large tan$\beta$ regime has to include correlations
between the constraints presented by the low energy values of the b quark mass
and $BR(b\to s\gamma)$. Both quantities receive SUSY contributions enhanced by
tan$\beta$ and have a major impact on the MSSM analysis. Here we summarize the
results of such a study constrained by minimal SO(10) unification. We show the
best fits, in the $(m_0,M_{1/2})$ plane, obtained in the global analysis
spanned over the gauge, Yukawa and SUSY parameter space at the unification
scale. Two distinct fits describe the available low-energy data very well. The
fits differ by the overall sign of the $b\to s\gamma$ decay amplitude. We
conclude that an attractive SO(10)-derived regime of the MSSM remains a viable
option.


title: Infrared Quasi Fixed Points and Mass Predictions in the MSSM

abstract:
  We consider the infrared quasi-fixed point solutions of the renormalization
group equations for the top-quark Yukawa coupling and soft supersymmetry
breaking parameters in the MSSM. The IR quasi-fixed points together with the
values of the gauge couplings, the top-quark and Z-boson masses allow one to
predict masses of the Higgs bosons, the stop squarks and the lightest chargino
as functions of the only free parameter $m_{1/2}$ or the gluino mass. The mass
of the lightest Higgs boson for $\mu>0$ and $M_{SUSY} \approx 1$ TeV is found
to be $m_h=(94.3+1.6+0.6\pm5\pm0.4)$ GeV. The case with $\mu<0$ is excluded by
experimental data.


title: The neutrino ground state in a neutron star

abstract:
  We address a recent claim that the stability of neutron stars implies a lower
bound on the mass of the neutrino. We argue that the result obtained by some
previous authors is due to an improper summation of an infrared-sensitive
series and that a non-perturbative "resummation" of the series yields a finite
and well-behaved result. The stability of neutron stars thus gives no lower
bound on the mass of the neutrino.


title: An analysis of Precision Electroweak Measurements: Summer 98 Update

abstract:
  We update our analysis of precision electroweak measurements using the latest
data announced at Moriond, March 1998. Possible oblique corrections from new
physics are parametrized using the STU formalism of Ref.[1], and non-oblique
corrections to the Zbb vertex are parametrized using the xi_b zeta_b formalism
of Ref.[2]. The implications of the analysis on minimal SU(5) grand unification
is discussed.


title:
The final-state interaction in the two-body nonleptonic decay of a heavy
  particle

abstract:
  We attempt to understand the final-state interaction in the two-body
nonleptonic decay of a heavy particle for which many multibody decay channels
are also open. No matter how many multibody channels couple to the two-body
channels, the analyticity of the S-matrix relates the phase and the magnitude
of the two-body decay amplitude through a dispersion relation. In general,
however, the phase cannot be determined by strong interactions alone. The
dispersion relation requires on a general ground that the final-state
interaction phases be small for the two-body decay amplitudes when the initial
particle is very heavy. We then analyze the final-state interaction phases in
terms of the s-channel eigenstates of the S-matrix and obtain semiquantitative
results applicable to the B decay with a random S-matrix hypothesis. We use the
high-energy scattering date and the dual resonance model as a guide to the
relevant aspects of strong interactions at long and intermediate distances.


title: Unification with Low String Scale

abstract:
  I argue that in open-string theory with hierarchically small (or large) extra
dimensions, gauge groups can unify naturally with logarithmically-running
coupling constants at the high Kaluza-Klein (or string-winding) scale.
  This opens up the possibility of rescuing the standard logarithmic
unification at $M_U\sim 10^{15-18}$ GeV even if the fundamental-string scale is
much lower, at intermediate or possibly even electroweak scales. I also
explain, however, why a low type-I string scale may not suffice to obliterate
the ultraviolet problems usually associated with the gauge hierarchy.


title: General Gauge Field Theory And Its Application

abstract:
  A gauge field model, which simultaneously has strict local gauge symmetry and
contains massive general gauge bosons, is discussed in this paper. The model
has SU(N) gauge symmetry. In order to introduce the mass term of gauge fields
directly without violating the gauge symmetry of the theory, two sets of gauge
fields will be introduced into the theory. After some transformations, one set
of gauge fields obtain masses and another set of gauge fields keep massless. In
the limit $\alpha \longrightarrow 0$ or $\alpha \longrightarrow \infty$, the
gauge field model discussed in this paper will return to Yang-Mills gauge field
model. Finally, some applications of this model are discussed.