title:
The Non-Trivial Phase of $\PHI ^4$-Theory in a Renormalisation Group
  Invariant Approach

abstract:
  Massless $\phi^{4}$-theory is investigated in zero and four space-time
dimensions. Path-integral linearisation of the $\phi ^{4}$-interaction defines
an effective theory, which is investigated in a loop-expansion around the mean
field. In zero dimensions this expansion converges rapidly to the exact
potential obtained numerically. In four dimensions its lowest order (mean-field
approximation) produces a real and convex effective potential. Two phases are
found. In one the renormalisation group improved one-loop effective potential
is recovered as the leading contribution near the classical minimum. This
phase, however, is unstable. The second (precarious) phase is found to have
lower vacuum energy density. In this phase a dynamical mass is generated. The
results are renormalisation group invariant.


title:
$\order(\Gamma)$ Corrections to $W$ pair production in $e^+e^-$ and
  $\gamma\gamma$ collisions

abstract:
  Several schemes to introduce finite width effects to reactions involving
unstable elementary particles are given and the differences between them are
investigated. The effects of the different schemes is investigated numerically
for $W$ pair production. In $e^+e^-\to W^+W^-$ we find that the effect of the
non-resonant graphs cannot be neglected for $\sqrt{s}\geq400\GeV$. There is no
difference between the various schemes to add these to the resonant graphs away
from threshold, although some violate gauge invariance. On the other hand, in
the reaction $\gamma\gamma\to W^+W^-$ the effect of the non-resonant graphs is
large everywhere, due to the $t$-channel pole. However, even requiring that the
outgoing lepton is observable ($p_\perp > .02\sqrt{s}$) reduces the
contribution to about 1\%. Again, the scheme dependence is negligible here.


title: Computation of Mini-Jet Inclusive Cross Sections

abstract:
  We apply the theory of parton-parton total cross sections at large ``s", due
to Lipatov and collaborators, to compute the inclusive cross section for jets
which accompany a large ``s" parton scattering process.


title: Leptoquarks at $e\gamma$ Colliders

abstract:
  We consider single production of leptoquarks (LQ's) at $e\gamma$ colliders,
for two values of the centre-of-mass energy, $\sqrt{s}=500$ GeV and 1 TeV. LQ's
with masses essentially up to the kinematic limit can be seen, even for
couplings as weak as $O(10^{-3})$-$O(10^{-2})\alpha_{em}$. It is possible to
detect LQ's of mass greater than $\sqrt{s}$ by looking for signals of virtual
LQ production in $e\gamma\to e q{\overline q}$.


title: Gauge boson masses dominantly generated by Higgs-triplet contributions?

abstract:
  We discuss a model in which the Standard Model (SM) Higgs sector has been
extended by additional real and complex triplets. The $\rho\approx 1$
constraint is satisfied by restricting the potential to have an enlarged
$\hisym $ global symmetry. This is fine tuning, which leads to a decreased
predictability in next-to-leading order. In this model, however, the triplet
vacuum expectation values may give the dominating contribution to the gauge
boson masses. Using a renormalization group argument we constrain this region
of the parameter space. Another interesting feature of this model is that one
of the neutral scalars doesn't couple to the fermion sector at tree level and
therefore could have a relatively large branching ratio to $2\gamma $'s. It is
coupled, however, to the $Z$-boson and therefore it could be produced at LEP
via the standard $e^+e^-\rightarrow Z\phi$ mechanism with rates comparable to
the ones of the Standard Model.


title: Solar Neutrinos

abstract:
  The status of solar neutrino experiments and their implications for both
nonstandard astrophysics ({\it e.g.,} cool sun models) and nonstandard neutrino
properties ({\it e.g.,} MSW conversions) are discussed. Assuming that all of
the experiments are correct, the relative rates observed by Kamiokande and
Homestake are hard to account for by a purely astrophysical solution, while MSW
conversions can describe all of the data. Assuming the standard solar model,
there are two allowed regions for MSW conversions into $\nu_\mu$ or $\nu_\tau$,
with the non-adiabatic solution giving a better fit than the large angle. For
conversions into sterile neutrinos there is only a nonadiabatic solution.
Allowing both MSW conversions and nonstandard astrophysics, the data
simultaneously determine the temperature of the core of the sun to within five
percent, consistent with the standard solar model prediction. The implications
of the atmospheric $\nu_\mu/\nu_e$ ratio and of a hot component of the dark
matter are briefly discussed, and the expectations of theoretical models
motivated by grand unification are summarized.


title: Flavor Changing Scalar Interactions

abstract:
  The smallness of fermion masses and mixing angles has recently been been
attributed to approximate global $U(1)$ symmetries, one for each fermion type.
The parameters associated with these symmetry breakings are estimated here
directly from observed masses and mixing angles. It turns out that although
flavor changing reaction rates may be acceptably small in electroweak theories
with several scalar doublets without imposing any special symmetries on the
scalars themselves, such theories generically yield too much CP violation in
the neutral kaon mass matrix. Hence in these theories CP must also be a good
approximate symmetry. Such models provide an alternative mechanism for CP
violation and have various interesting phenomenological features.


title:
Peculiar Velocities and Microwave Background Anisotropopies from Cosmic
  Strings

abstract:
  Using an analytic model we show that the predictions of the cosmic string
model for the peculiar velocities and the microwave background (MBR) anisotropy
depend on similar combinations of string evolution parameters. Normalizing from
the COBE detection of MBR anisotropy, and for certain reasonable values of
string network evolution parameters, we find that the magnitude of predicted
velocity flows is in good agreement with observations on small scales but is
inconsistent with observations on large scales ($ > 50 h^{-1}$Mpc). The Cosmic
Mach Number obtained from the cosmic string scenario is found to depend on a
single network evolution parameter and is consistent with observations on
scales $5h^{-1}$Mpc to $20h^{-1}$Mpc.


title:
Constraints from Nucleosynthesis and SN1987A on Majoron Emitting Double
  Beta Decay

abstract:
  We examine whether observable majoron emission in double beta decay can be
compatible with the big-bang nucleosynthesis (NS) and the observed neutrino
flux from SN1987A. It is found that the NS upper bound on $^4$He abundance
implies that the majoron-neutrino Yukawa coupling constant $g\leq 9\times
10^{-6}$ and its maximal value is allowed only when the scalar quartic coupling
constant $\lambda$ is extremely small, $\lambda\leq 100g^2$.
  It is also observed that, although quite less restrictive, SN1987A also
provides independent constraints on coupling constants.


title: The Weak Mixing Angle in String Theory and the Green-Schwarz Mechanism

abstract:
  Four-dimensional strings with the standard model gauge group $SU(3)\times
SU(2)\times U(1)$ give model-dependent predictions for the tree level weak
mixing-angle. In the presence of an extra pseudo-anomalous gauged- ${U(1)}_X$,
the value of the weak angle may be computed purely in terms of the charges of
the massless fermions of the theory, independently of the details of the
massive string sector. I present the simplest such $ {U(1)}_X$ which leads to
the canonical result $sin^2\theta _W=3/8$ in the supersymmetric standard model.
This is a sort of gauged Peccei-Quinn symmetry which requires the presence of
just the minimal set of Higgs doublets and forbids dimension-four $B$ and
$L$-violating terms. In this approach the cancellation of the $U(1)_X$
anomalies through a Green-Schwarz mechanism plays a crucial role. In a
different context (that of non-string low-energy supersymmetric models) I
briefly discuss wether this type of anomaly cancellation mechanism could be of
phenomenological relevance close to the electroweak scale. (Talk at the 23-th
Workshop of the INFN Eloisatron Project on Properties of Susy particles, Erice,
October 1992)


title: NJL breaking of supersymmetric GUTs

abstract:
  We analyze the breakdown of SUSY GUTs driven by Nambu--Jona--Lasinio
condensates. Starting with the most general gauge invariant and pure
K\"ahlerian Lagrangian up to quartic order we solve the one loop gap equation
and determine the breaking direction. This is done for various classes of
groups and spectra of fundamental particles which especially cover the most
promising unifying groups $SU(5)$, $SO(10)$ and $E_6$. Heavy masses for the
fundamental as well as for the composite particles are calculated. The results
are used to single out candidates which may lead to an acceptable low energy
theory. In these models we discuss some phenomenological aspects and point out
the difficulties in constructing phenomenological viable theories in our
scenario.


title: Production of $\eta$ Mesons Near Threshold

abstract:
  It is argued that the strong energy dependence of the $p\, d \rightarrow
\,^{3\!}H\!e\, \eta$ cross section near threshold is due to a final state
interaction between the $\eta$ meson and the $^3$He nucleus. The large
scattering length that this implies is in accord with optical potential
predictions and is evidence for a nearby virtual `$\!$`bound'$\!$' state in the
$\eta^3$He system. This model suggests that sharp structures should also be
seen close to production thresholds on other light nuclei.


title:
Determination of the reaction plane in ultrarelativistic nuclear
  collisions

abstract:
  In the particles produced in a nuclear collision undergo collective flow, the
reaction plane can in principle be determined through a global event analysis.
We show here that collective flow can be identified by evaluating the reaction
plane independently in two separate rapidity intervals, and studying the
correlation between the two results. We give an analytical expression for the
correlation function between the two planes as a function of their relative
angle. We also discuss how this correlation function is related to the
anisotropy of the transverse momentum distribution. Email contact:
ollie@amoco.saclay.cea.fr


title:
Associated $J/\psi + \gamma$ production as a probe of the polarized
  gluon distribution

abstract:
  Associated production of $J/\psi$ and a $\gamma$ has recently been proposed
as clean probe of the gluon distribution. The same mechanism can be used to
probe the polarized gluon content of the proton in polarized proton-proton
collisions. We study $J/\psi + \gamma$ production at both polarized fixed
target and polarized collider energies.


title:
Flavour Changing Neutral Currents, Weak-Scale Scalars and Rare Top
  Decays

abstract:
  We examine the decays $t\rightarrow c\gamma$ and $c Z^0$ in the Standard
Model with an extra scalar doublet and no discrete symmetry preventing
tree-level flavour changing neutral currents. The Yukawa couplings of the new
scalars are assumed to be proportional to fermion masses, evading bounds on
FCNC's from the light quark sector. These rare top decays may be visible at the
SSC.


title: Domain Wall Formation In The Post-Inflationary Universe

abstract:
  We consider the evolution of the probability distribution $\pp (\chi ,\chib,
\t)$, associated with an inhomogeneous light scalar field $\chi$ in the
Robertson-Walker Universe, where the inhomogeneities are produced by quantum
fluctuations during an earlier inflationary epoch. For a specific choice of
scalar potential which occurs in models of so called late-time phase
transitions in which domain walls are produced, $\pp$ is shown to evolve from a
Gaussian to a non-Gaussian distribution. The structure of the latter justifies
the recent use of 3-dimensional percolation theory to describe the initial
distribution of domain walls in these models.


title: The weak electroweak phase transition

abstract:
  We present a detailed analysis of the phase transition in the standard model
at finite temperature. Using an improved perturbation theory, where plasma
masses are determined from a set of one-loop gap equations, we evaluate the
effective potential $V_{eff}(\varphi,T)$ in next-to-leading order, i.e.,
including terms cubic in the gauge coupling $g$, the scalar self-coupling
$\lambda^{1/2}$ and the top-quark Yukawa coupling $f_t$. The gap equations
yield a non-vanishing magnetic plasma mass for the gauge bosons, originating
from the non-abelian self-interactions. We discuss in detail size and origin of
higher order effects and conclude that the phase transition is weakly
first-order up to Higgs masses of about $70\ GeV$, above which our calculation
is no longer self-consistent. For larger Higgs masses even an approximation
containing all $g^4$ contributions to $V_{eff}$ is not sufficient, at least a
full calculation to order $g^6$ is needed. These results turn out to be rather
insensitive to the top-quark mass in the range $m_t=100\ -\ 180\ GeV$. Using
Langer's theory of metastability we calculate the nucleation rate of critical
droplets and discuss some aspects of the cosmological electroweak phase
transition.


title: A Shadow Matter Universe

abstract:
  The cosmological and astrophysical implications of a shadow matter model
which could also have interesting experimental consequences are examined. The
model has identical microphysics for both the ordinary and shadow worlds but
requires a macroscopic asymmetry from nucleosynthesis constraints. It is
proposed that this macroscopic asymmetry can be generated at the quark-hadron
phase transition.


title: The Search for the Dark Matter: WIMPs and MACHOs

abstract:
  Review talk presented at the Texas/PASCOS Symposium, Berkeley, CA, Dec 1992.
We review the status of experiments and ideas relevant for the detection of the
dark matter which is suspected to be the dominant constituent of the Universe.
Great progress is being made and the chances are non-negligible that one of the
many currently in-progress experiments will discover the nature of the dark
matter. We discuss the main dark matter candidates, and review the experiments
relevant to each of them.


title:
Direct Channel Dominance in Goldstone Boson Scattering in the Resonance
  Region

abstract:
  We consider the scattering of Goldstone bosons in the range of intermediate
energies, and in particular focus our attention on the scattering of pions in
the $\rho$-resonance region. The chiral perturbation series is obtained to
order $E^4$ from a chiral $SU(2)\times SU(2)$ invariant effective Lagrangian.
At order $E^4$, we isolate the low-energy manifestation of heavy particle
exchange in the s-channel. We find that the contributions of this type to the
I=1 and I=2 amplitudes have a one parameter dependence. This observation
provides a symmetry rationale for Chanowitz's recent observation that in a
chiral model with an explicitly coupled $\rho$, the I=1 and I=2 channels are
strongly correlated. In order to realize, in a quantitative way, the fact that
in the resonance region the direct-channel dominates, we make use of a simple
and intuitive unitarization scheme. This allows us to derive a renormalization
constant-independent relation for the I=1 and I=2 phase shifts. With the
assumption of a $\rho$-resonance, this relation determines the position of a
pole at euclidean momentum in the I=2 channel. Through an analysis based on the
theory of redundant poles and the Adler sum rule we show that this ``tachyon''
pole actually represents a physical contribution to the unitary amplitude which
accounts for $\rho$ and $\epsilon$ exchange in the u-channel.


title: CTEQ Parton Distributions and Flavor Dependence of Sea Quarks

abstract:
  This paper describes salient features of new sets of parton distributions
obtained by the CTEQ Collaboration based on a comprehensive QCD global analysis
of all available data. The accuracy of the new data on deep inelastic
scattering structure functions obtained by the very high statistics NMC and
CCFR experiments provides unprecedented sensitivity to the flavor dependence of
the sea-quark distributions. In addition to much better determination of the
small x dependence of all parton distributions, we found: (i) the strange quark
distribution is much softer than the non-strange sea quarks and rises above the
latter at small-x; and (ii) the difference $\bar d-\bar u$ changes sign as a
function of x. A few alternative sets of viable distributions with conventional
assumptions are also discussed.


title: Resolution of the lambda Phi^4 Puzzle and a 2 Tev Higgs Boson

abstract:
  We argue that massless (lambda Phi^4)_4 is "trivial" without being entirely
trivial. It has a non-trivial effective potential which leads to spontaneous
symmetry breaking, but the particle excitations above the broken vacuum are
non-interacting. The key to this picture is the realization that the constant
background field (the mode with zero 4-momentum) renormalizes differently from
the fluctuation field (the finite-momentum modes). This picture reconciles
rigorous results and lattice calculations with one-loop and
Gaussian-approximation analyses. Because of "triviality", these latter two
methods should be effectively exact. Indeed, they yield the same renormalized
effective potential and the same relation m_h^2 = 8 pi^2 v^2 between the
particle mass and the physical vacuum expectation value. This relation predicts
a Higgs mass m_h about 2 TeV in the standard model. The non-interacting nature
of the scalar sector implies, by the equivalence theorem, that Higgs and gauge
bosons interact only weakly, through their gauge and Yukawa couplings.


title: Proving the Low Energy Theorem of Hidden Local Symmetry

abstract:
  Based on the Ward-Takahashi identity for the BRS symmetry, we prove to all
orders of the loop expansion the low energy theorem of hidden local symmetry
for the vector mesons (KSRF (I) relation) in the $U(N)_{\rm L}$ $\times$
$U(N)_{\rm R}$ / $U(N)_{\rm V}$ nonlinear chiral Lagrangian.


title: Low Energy Theorems of Hidden Local Symmetries

abstract:
  We prove to all orders of the loop expansion the low energy theorems of
hidden local symmetries in four-dimensional nonlinear sigma models based on the
coset space $G/H$, with $G$ and $H$ being arbitrary compact groups. Although
the models are non-renormalizable, the proof is done in an analogous manner to
the renormalization proof of gauge theories and two-dimensional nonlinear sigma
models by restricting ourselves to the operators with two derivatives (counting
a hidden gauge boson field as one derivative), i.e., with dimension 2, which
are the only operators relevant to the low energy limit. Through loop-wise
mathematical induction based on the Ward-Takahashi identity for the BRS
symmetry, we solve renormalization equation for the effective action up to
dimension-2 terms plus terms with the relevant BRS sources. We then show that
all the quantum corrections to the dimension-2 operators, including the finite
parts as well as the divergent ones, can be entirely absorbed into a
re-definition (renormalization) of the parameters and the fields in the
dimension-2 part of the tree-level Lagrangian.


title: Systematic Analysis Method for Color Transparency Experiments

abstract:
  We introduce a data analysis procedure for color transparency experiments
which is considerably less model dependent than the transparency ratio method.
The new method is based on fitting the shape of the A dependence of the nuclear
cross section at fixed momentum transfer to determine the effective attenuation
cross section for hadrons propagating through the nucleus. The procedure does
not require assumptions about the hard scattering rate inside the nuclear
medium. Instead, the hard scattering rate is deduced directly from the data.
The only theoretical input necessary is in modelling the attenuation due to the
nuclear medium, for which we use a simple exponential law. We apply this
procedure to the Brookhaven experiment of Carroll et al and find that it
clearly shows color transparency: the effective attenuation cross section in
events with momentum transfer $Q^2$ is approximately $40\ mb\ (2.2\
GeV^2/Q^2)$. The fit to the data also supports the idea that the hard
scattering inside the nuclear medium is closer to perturbative QCD predictions
than is the scattering of isolated protons in free space. We also discuss the
application of our approach to electroproduction experiments.


title: Higgs Mass Bound in the Minimal Standard Model

abstract:
  A brief review of the role of the Higgs mechanism and the ensuing Higgs
particle in the Minimal Standard Model is given. Then the property of
triviality of the scalar sector in the Minimal Standard Model and the upper
bound on the Higgs mass that follows is discussed. It is emphasized that the
bound is obtained by limiting cutoff effects on physical processes. Actions
that allow a parameterization and tuning of the leading cutoff effects are
studied both analytically, in the large $N$ limit of the generalization of the
$O(4)$ symmetry of the scalar sector to $O(N)$, and numerically for the
physical case $N = 4$. Combining those results we show that the Minimal
Standard Model will describe physics to an accuracy of a few percent up to
energies of the order 2 to 4 times the Higgs mass, $M_H$, only if $M_H \le 710
\pm 60 ~ GeV$. This bound is the result of a systematic search in the space of
dimension six operators and is expected to hold in the {\it continuum}.
(Complete postscript file can be obtained by anonymous ftp from
ftp.scri.fsu.edu as file "corfu_92.ps" from directory "pub/heller".)


title: Effective Field Theory for Plasmas at all Temperatures and Densities

abstract:
  The solution of the plasmon problem and the subsequent development of an
effective field theory approach to ultrarelativistic plasmas are reviewed. The
effective lagrangians that summarize collective effects in ultrarelativistic
quark-gluon and electron-photon plasmas are presented. A generalization that
describes an electromagnetic plasma at all temperatures and densities is
proposed.


title: The Schwinger Model and Perturbative Charge Screening

abstract:
  \noindent The well-known exact solution of the massless Schwinger model can
be simply obtained by perturbing around a vacuum without the Dirac sea of
filled negative energy states. The unusual vacuum structure changes the sign of
the $i\epsilon$ prescription at the negative energy pole of the free fermion
propagator. Consequently, all convergent fermion loop integrals vanish. The
logarithmically divergent two-point loop gives a mass $e/\sqrt\pi$ to the
photon, which turns into the free pointlike boson of the Schwinger model. We
discuss the possiblity of using corresponding expansions to describe charge
screening effects in the massive Schwinger model and the confinement phenomenon
of QCD.


title: Lee-Quigg-Thacker Bounds for Higgs Boson Masses in a Two-Doublet Model

abstract:
  Upper bounds for neutral as well as charged Higgs boson masses in a
two-doublet model are obtained on the basis of tree unitarity conditions \`a la
Lee, Quigg and Thacker. A wide variety of scattering processes are considered
so extensively that our bounds are more restrictive than those obtained
previously for neutral Higgs bosons and are also of a new kind for charged
Higgs boson. It is argued that at least one of the Higgs bosons should be
lighter than 580 ${\rm GeV}/c^{2}$.


title: Rotational covariance and light-front current matrix elements

abstract:
  Light-front current matrix elements for elastic scattering from hadrons with
spin~1 or greater must satisfy a nontrivial constraint associated with the
requirement of rotational covariance for the current operator. Using a model
$\rho$ meson as a prototype for hadronic quark models, this constraint and its
implications are studied at both low and high momentum transfers. In the
kinematic region appropriate for asymptotic QCD, helicity rules, together with
the rotational covariance condition, yield an additional relation between the
light-front current matrix elements.


title:
The Trace Anomaly in Chiral Dynamics: $\gamma \gamma \to \pi^0\pi^0$
  Scattering

abstract:
  The trace anomaly term in the low energy chiral Lagrangian is established by
deriving a low energy theorem for $\gamma \gamma \rightarrow \pi^0\pi^0$
scattering. It contributes to $\sigma(\gamma \gamma \rightarrow \pi^0\pi^0)$ in
the same order as the previously computed pion loop contribution. The coherent
sum of the two contributions explains the shape of the measured cross section,
while the magnitude is determined by the anomalous dimension of the quark mass
operator.


title: Phenomenological constraints on the flavour asymmetry of the nucleon sea

abstract:
  We study the possible flavour asymmetry, $\bar{u} \neq \bar{d}$, of the light
quark sea distributions of the proton. We discuss the information that is at
present available from data on deep-inelastic lepton-nucleon scattering and
from Drell-Yan production on various nuclear targets. We show that the ratio of
dilepton yields on hydrogen and deuterium targets is very sensitive to
$\bar{u}-\bar{d}$.


title: W, Z and Higgs Scattering at SSC Energies

abstract:
  We examine the scattering of longitudinal $W$, $Z$ and Higgs bosons in the
Standard Model using the equivalent Goldstone-boson Lagrangian. Our
calculations include the full one-loop scattering matrix between the states
$W^+_LW^-_L$, $Z_LZ_L$ and $HH$ with no restrictions on the relative sizes of
$M_H$ and $\sqrt{s}$. In addition to deriving the perturbative
eigen-amplitudes, we also obtain quite striking results by unitarizing the
amplitudes with the use of the K-matrix and Pad\'e techniques. (Complete
postscript file can be obtained by anonymous ftp from hal.physics.wayne.edu as
dpf92g.ps in directory pub/physics )


title:
Transverse Tau Polarization in Decays of the Top and Bottom Quarks in
  the Weinberg Model of CP Non-conservation

abstract:
  We show that the transverse polarization asymmetry of the $\tau$-lepton in
the decay $t\rightarrow b \tau \nu$ is extremely sensitive to CP violating
phases arising from the charged Higgs exchange in the Weinberg model of CP
non-conservation. Qualitatively, the polarization asymmetries are enhanced over
rate or energy asymmetries by a factor of $\approx {m_t\over m_\tau}\approx
O(100)$. Thus for optimal values of the parameters the method requires $\approx
10^4$ top pairs to be observable rather than $10^7$ needed for rate or energy
asymmetries. We also examine $\tau$ polarization in b decays via $b \rightarrow
c \nu \tau$ and find that it can also be very effective in constraining the CP
violation parameters of the extended Higgs sector.


title: Finite temperature effective action and thermalization of perturbations

abstract:
  The effective action is computed for the \lphi--theory at finite temperature
for small perturbations about a constant background field, using a generalized
tadpole method. We find the complete effective action, including the real and
imaginary parts, to all orders in derivatives and to order ${\cal
O}(\lambda^2)$. We demonstrate that the high $T$ approximation, where only the
zero Matsubara frequency is included, is incorrect for the imaginary part even
though it is UV-finite. The solutions of the dispersion relations show that
initial perturbations do not necessarily thermalize fast enough to be absent at
the onset of phase transition.


title: $b \to s \gamma$ Decay and Supersymmetry

abstract:
  The inclusive radiative $B$-decay is a sensitive probe of new physics,
especially if related to the virtual exchange of a charged Higgs boson.
Supersymmetric models provide a particularly interesting example. In the limit
of exact supersymmetry, BR($b \to s\gamma$)~=~0, due to the vanishing of any
magnetic-moment transition operator. We illustrate the impact of this
constraint for realistic values of the supersymmetry-breaking parameters.


title:
The Chiral Soliton of the Nambu Jona-Lasinio Model with Vector and Axial
  Vector Mesons

abstract:
  The self-consistent chiral soliton of the Nambu--Jona-Lasinio model including
the $\omega,\rho$ and $a_1$ (axial-) vector meson fields besides the chiral
angle is investigated. The resulting energy spectrum of the one particle Dirac
Hamiltonian is strongly distorted leading to a polarized Dirac sea which
carries the complete baryon number. This supports Witten's conjecture that
baryons can be described as topological solitons. The exploration of the
isoscalar mean squared radius of the nucleon exhibits that the repulsive
character of the isoscalar vector field $\omega$ as well as the attractive
features of the (axial-) vector mesons $\rho$ and $a_1$ are reproduced in the
Nambu--Jona-Lasinio model. The axial charge of the nucleon $g_A$ comes out far
too small. This can be understood as an artifact of the proper time
regularization prescription.


title:
Twist-4 Matrix Elements of the Nucleon from Recent DIS Data at CERN and
  SLAC

abstract:
  We analyse the recent precision measurements of the lepton-hadron deep
inelastic scattering at CERN and SLAC to extract model independent constraints
among the nucleon matrix elements of the twist-4 operators. We also study a
parameterization of these matrix elements and point out the possibility that
the matrix elements of the quark-gluon mixed operator has a negative value of
the order of $- (400 \pm 100\ {\rm MeV})^2$ at 5 GeV$^2$ renormalization scale.


title: Perturbative QCD data are consistent with light gluinos

abstract:
  We discuss systematically the consistency of light gluinos with data on
perturbative QCD from deep inelastic scattering, quarkonia, jets at LEP, and
the total hadronic cross-section in ${e^+ e^-}$ annihilation on the $Z$ peak
and elsewhere. We demonstrate that, in addition to the well-known increase in
the value of $\alpha_s(m_Z)$ inferred from lower-energy data due to the slower
running of $\alpha_s$ in the presence of light gluinos, the value of
$\alpha_s(m_Z)$ extracted from the LEP data must also be $increased$, as a
result of including the effects of virtual light gluinos. The effect of these
increases in other estimates of $\alpha_s(m_Z)$ is to make them more consistent
with the value extracted from the total $e^+ e^-$ cross-section, which would
otherwise appear distinctly higher. We discuss the possibility of looking for
light gluinos in four-jet events at LEP, and their possible implications for
scaling violations at HERA.


title: Bottom-Up Approach to Uniefied Supergravity Models

abstract:
  A new approach is proposed to phenomenological study of a generic unified
supergravity model, which reduces to the minimal supersymmetric standard model.
The model is effectively parametrized in terms of five low energy observables.
In consequence, it is easy to investigate systematically the parameter space of
the model, allowed by the requirement of radiative electroweak symmetry
breaking and by the present experimental limits. Radiative corrections due to
large Yukawa couplings and particle--sparticle mass splitting are included into
the analysis and found to have important effects, in particular on the degree
of fine tuning in the model. In this framework there are presented the
predictions of the model for various low energy physical observables and their
dependence on the values of the top quark mass and $\tan\beta$ is discussed.
Results are also given for the large $\tan\beta$ scenario, $\tan\beta\approx
m_t/m_b$. Our approach can be easily extended to non--minimal supergravity
models, which do not assume the universality of the soft breaking parameters at
the unification scale $M_X$. Such an extension will be particularly useful once
the masses of some sparticles are known, allowing for a model independent study
of the parameter space at $M_X$.


title: Leptonic Fritzsch Matrices and Neutrino Oscillations

abstract:
  It was recently shown by the authors that the Fritzsch ansatz for the quark
mass matrices prescribed at the supersymmetric grand unified scale is
compatible with a moderately heavy top quark ($m_t \simeq 120-150~GeV$). Here
we extend the ansatz to incorporate the charged leptons and the neutrinos. It
is found that the $\nu_e-\nu_\mu$ mixing angle is small and consistent with the
MSW solution of the solar neutrino puzzle. Furthermore, the model predicts
observable $\nu_\mu-\nu_\tau$ oscillations with sin$^22\theta_{\mu \tau} \simeq
0.1$ and $\nu_\tau$ mass in the $(1-3)~eV$ range.


title: Thermalisation of Longitudinal Gluons

abstract:
  In the usual real-time finite-temperature gauge theory both the physical and
the unphysical degrees of freedom are thermalised. We discuss the alternative
approach where only the physical transverse components of the gauge field have
bare thermal propagators, whereas the unphysical degrees of freedom are not
heated. We show how pinch singularities are avoided: sometimes this requires
resummation. If only the hard thermal loop is included in the resummation, the
spatially-longitudinal component of the gauge field, which contains an extra
collective plasmon mode, becomes fully thermalised, though the Faddeev-Popov
ghost and the remaining unphysical component of the gauge field remain frozen.


title:
Higgs-Boson Decay to Four Fermions Including a Single Top Quark Below $t
  \bar t$ Threshold

abstract:
  The rare decay modes Higgs $\rightarrow$ four light fermions, and Higgs
$\rightarrow$ single top-quark + three light fermions for $m_t<M_H<2m_t$, are
presented, and phenomenologically interpreted. The angular correlation between
fermion planes is presented as a test of the spin and intrinsic parity of the
Higgs particle. In Higgs decay to single top, two tree-level graphs contribute
in the standard model (SM); one couples the Higgs to $W^+W^-(\sim gM_W)$, and
one to $t\bar t(\sim g_{top\;yukawa}=m_t/246\GeV)$. The large Yukawa coupling
for $m_t>100\GeV$ makes the second amplitude competitive or dominant for most
$M_H,m_t$ values. Thus the Higgs decay rate to single top directly probes the
SM universal mechanism generating both gauge boson and fermion masses, and
offers a means to infer the Higgs-$t \bar t$ Yukawa coupling when $H\rightarrow
t \bar t$ is kinematically disallowed. We find that the modes $pp\rightarrow
Xt\bar t(H\rightarrow t\bar b W^{(*)})$ at the SSC, and $e^+ e^-\rightarrow
Z\,or\,\nu\bar{\nu} + (H\rightarrow t\bar b W^{(*)})$ at future high energy,
high luminosity colliders, may be measureable if $2m_t$ is not too far above
$M_H$. We classify non-standard Higgses as gaugeo-phobic, fermio-phobic or
fermio-philic, and discuss the Higgs$\rightarrow$ single top rates for these
classes.


title:
Schwinger-Dyson equations: Dynamical Chiral Symmetry Breaking and
  Confinement

abstract:
  A representative but not exhaustive review of the Schwinger-Dyson equation
(SDE) approach to the nonperturbative study of QCD is presented. The main focus
is the SDE for the quark self energy but studies of the gluon propagator and
quark-gluon vertex are also discussed insofar as they are important to the
quark SDE. The scope of this article is the application of these equations to
the study of dynamical chiral symmetry breaking, quark confinement and the
phenomenology of the spectrum and dynamics of QCD.


title:
Electroweak Corrections to the Supersymmetric Charged Higgs Fermionic
  Decay

abstract:
  One-loop radiative corrections to the charged Higgs coupling to two fermions
and to the charged Higgs fermionic decay are studied. A renormalization scheme
is proposed including the definition of the parameter $\tan\beta$ through the
coupling of the CP-odd Higgs boson to a charged lepton pair. Loops including
top and bottom quarks and squarks are considered using the unitary gauge. Large
corrections to the coupling are found when there is a substantial mixing in the
squark mass matrix, but these corrections are suprress in the decay rate.
Interesting applications to rare processes are discussed.


title:
Constraints on Supersymmetry due to b -> s \gamma : an Improved
  Calculation

abstract:
  The calculation of the one-loop induced decay rate b -> s \gamma is improved
by including radiative corrections to the charged Higgs mass and to the
charged-Higgs-fermion-fermion vertex. It is shown how the radiative corrections
modify the excluded zone in the \tan\beta-m_A plane, imposed by the
non-observation of this decay. In particular, a light CP-odd Higgs at large
\tan\beta becomes allowed.


title:
Emergence of Coherent Long Wavelength Oscillations After a Quench:
  Application to QCD

abstract:
  To model the dynamics of the chiral order parameter in a far from equilibrium
phase transition, we consider quenching in the O(4) linear sigma model. We
argue, and present numerical evidence, that in the period immediately following
the quench long wavelength modes of the pion field are amplified. This results
in large regions of coherent pion oscillations, and could lead to dramatic
phenomenological consequences in heavy ion collisions.


title:
First Order Phase Transition in a Two Higgs-doublet Model with
  $M_{h}>M_{W}$

abstract:
  We study the 3d effective field theory of a weakly coupled two Higgs-doublet
scalar model at high temperature. Our model has three scalar quartic couplings
and an $O(4)$ symmetry which is spontaneously broken by a nonzero scalar field
$vev$ at zero temperature. Using high temperature perturbation theory,
renormalization group arguments in $4-\epsilon$ dimensions, as well as $1/N$
expansion techniques in 3 dimensions, we argue that the transition from the
high temperature symmetry restoring phase to the low temperature phase is first
order for a range of scalar couplings. This result is not due to gauge
couplings. We discuss the implications of our results for baryogenesis in the
two Higgs-doublet electroweak model, especially when the lightest neutral Higgs
is heavier than the W--bosons.


title: Ten Dimensional SO(10) G.U.T. Models with Dynamical Symmetry Breaking

abstract:
  We discuss the derivation of $SO(10)$ G.U.T. models from higher dimensional
theories with intermediate breaking scales. We then present models based on the
Coset Space Dimensional Reduction Scheme with intermediate symmetry breaking
induced by four fermion condensates.


title:
The Anatomy of $\varepsilon'/\varepsilon$ Beyond Leading Logarithms with
  Improved Hadronic Matrix Elements

abstract:
  We use the recently calculated two--loop anomalous dimensions of
current-current operators, QCD and electroweak penguin operators to construct
the effective Hamiltonian for $\Delta S=1$ transitions beyond the leading
logarithmic approximation. We solve the renormalization group equations and
give the numerical values of Wilson coeff. functions. We propose a new
semi-phenomenological approach to hadronic matrix elements which incorporates
the data for $CP$-conserving $K \rightarrow \pi\pi$ amplitudes and allows to
determine the matrix elements of all $(V-A)\otimes (V-A)$ operators in any
renormalization scheme and do a renormalization group analysis of all hadronic
matrix elements $\langle Q_i(\mu) \rangle$. We compare critically our treatment
of these matrix elements with those given in the literature. We find in the NDR
scheme $\epe = (6.7 \pm 2.6)\times 10^{-4}$ in agreement with the experimental
findings of E731. We point out however that the increase of $\langle Q_6
\rangle$ by only a factor of two gives $\epe = (20.0 \pm 6.5)\times 10^{-4}$ in
agreement with the result of NA31. The dependence of $\epe$ on
$\Lambda_{\bar{MS}}$, $m_t$ and $\langle Q_{6,8} \rangle$ is presented.


title:
Post-COBE predictions for Inflationary Gravity Wave and Density
  Perturbation spectra

abstract:
  We assess the relative contribution to the COBE - measured microwave
anisotropy arising both from relic gravity waves as well as primordial density
perturbations originating during inflation. We show that the gravity wave
contribution to the CMBR anisotropy depends sensitively upon $n$ -- the
primordial spectral index ($\dk^2 \propto k^n$), increasing as $n$ deviates
from a Harrison - Zeldovich spectrum (n = 1). As a result, for $n < 0.84$ the
contribution from gravity waves towards $\delta T/ T $ is greater than the
corresponding contribution from density perturbations, whereas for $n > 0.84$
the reverse is true. ($ n = 0.84$ corresponds to an expansion index $p = 13.5$
in models with power-law inflation $a \propto t^p$. ) Our results show that for
a scale-invariant Harrison-Zeldovich spectrum generated by chaotic inflation,
gravity waves contribute approximately $24\%$ to the CMBR anisotropy measured
by COBE. Applying our results to the cold dark matter scenario for galaxy
formation, we find that in general CDM models with tilted power spectra ($n <
1$), require the biasing parameter to be greater than unity, on scales of
$16h_{50}^{-1} Mpc$. We also obtain an expression for the COBE - normalised
amplitude and spectrum of the stochastic gravity wave background and compare it
with the sensitivity of planned laser-interferometer gravity wave detectors.


title: Extraction of Coupling Information From $Z' \to jj$

abstract:
  An analysis by the ATLAS Collaboration has recently shown, contrary to
popular belief, that a combination of strategic cuts, excellent mass
resolution, and detailed knowledge of the QCD backgrounds from direct
measurements can be used to extract a signal in the $Z' \to jj$ channel in
excess of $6\sigma$ for certain classes of extended electroweak models. We
explore the possibility that the data extracted from $Z$ dijet peak will have
sufficient statistical power as to supply information on the couplings of the
$Z'$ provided it is used in conjunction with complimentary results from the $Z'
\to \ell^+ \ell^-$ `discovery' channel. We show, for a 1 TeV $Z'$ produced at
the SSC, that this technique can provide a powerful new tool with which to
identify the origin of $Z'$'s.


title: Sterile Neutrinos as Dark Matter

abstract:
  The simplest model that can accomodate a viable nonbaryonic dark matter
candidate is the standard electroweak theory with the addition of right-handed
or sterile neutrinos. We reexamine this model and find that the sterile
neutrinos can be either hot, warm, or cold dark matter. Since their only direct
coupling is to left-handed or active neutrinos, the most efficient production
mechanism is via neutrino oscillations. If the production rate is always less
than the expansion rate, then these neutrinos will never be in thermal
equilibrium. However, enough of them may be produced so that they provide the
missing mass necessary for closure. We consider a single generation of neutrino
fields $\left (\nu_L,\,\nu_R\right )$ with a Dirac mass, $\mu$, and a Majorana
mass for the right-handed components only, $M$. For $M\gg \mu$ we show that the
number density of sterile neutrinos is proportional to $\mu^2/M$ so that the
energy density today is {\it independent of} $M$. However $M$ is crucial in
determining the large scale structure of the Universe. In particular, $M\simeq
0.1-1.0 {\rm ~keV}$ leads to warm dark matter and a structure formation
scenario that may have some advantages over both the standard hot and cold dark
matter scenarios.


title: Reconstructing the Inflaton Potential---in Principle and in Practice

abstract:
  Generalizing the original work by Hodges and Blumenthal, we outline a
formalism which allows one, in principle, to reconstruct the potential of the
inflaton field from knowledge of the tensor gravitational wave spectrum or the
scalar density fluctuation spectrum, with special emphasis on the importance of
the tensor spectrum. We provide some illustrative examples of such
reconstruction. We then discuss in some detail the question of whether one can
use real observations to carry out this procedure. We conclude that in
practice, a full reconstruction of the functional form of the potential will
not be possible within the foreseeable future. However, with a knowledge of the
dark matter components, it should soon be possible to combine
intermediate-scale data with measurements of large-scale cosmic microwave
background anisotropies to yield useful information regarding the potential.


title: Enhancing the heavy Higgs signal with jet-jet profile cuts

abstract:
  The jet-jet profile, or detailed manner, in which transverse energy and mass
are distributed around the jet-jet system resulting from the hadronic decay of
a $Z$ boson in the process Higgs$\to ZZ$ at a proton-proton collider energy of
$40\tev$ is carefully examined. Two observables are defined that can be used to
help distinguish the $\ell^+\ell^-$-jet-jet signal from Higgs decay from the
``ordinary'' QCD background arising from the large transverse momentum
production of single $Z$ bosons plus the associated jets. By making cuts on
these observables, signal to background enhancement factors greater than $100$
can be obtained.


title: Exotic Fermions

abstract: I review the current limits on the mixing of ordinary and exotic fermions.


title:
One-Loop Analysis of the Electroweak Breaking in Supersymmetric Models
  and the Fine-Tuning Problems

abstract:
  We examine the electroweak breaking mechanism in the minimal supersymmetric
standard model (MSSM) using the {\em complete} one-loop effective potential
$V_1$. First, we study what is the region of the whole MSSM parameter space
(i.e. $M_{1/2},m_o,\mu,...$) that leads to a succesful $SU(2)\times U(1)$
breaking with an acceptable top quark mass. In doing this it is observed that
all the one-loop corrections to $V_1$ (even the apparently small ones) must be
taken into account in order to get reliable results. We find that the allowed
region of parameters is considerably enhanced with respect to former "improved"
tree level results. Next, we study the fine-tuning problem associated with the
high sensitivity of $M_Z$ to $h_t$ (the top Yukawa coupling). Again, we find
that this fine-tuning is appreciably smaller once the one-loop effects are
considered than in previous tree level calculations. Finally, we explore the
ambiguities and limitations of the ordinary criterion to estimate the degree of
fine-tuning. As a result of all this, the upper bounds on the MSSM parameters,
and hence on the supersymmetric masses, are substantially raised, thus
increasing the consistency between supersymmetry and observation.


title: Neutrino Interactions in Matter :

abstract:
  If a fermion is travelling through a medium, it can have matter-induced
magnetic and electric dipole moments. These contributions conserve chirality,
and can be non-vanishing even for a Majorana neutrino. Several implications for
neutrino physics are discussed.


title:
Effects of scalar mixing in ${g}{g} \rightarrow \mbox{Higgs} \rightarrow
  \ga\ga$

abstract:
  We discuss the effects of mixing of scalars belonging to left-- and
right--chiral MSSM super--multiplets on the process ${g}{g}\rightarrow \hnl
\rightarrow \ga\ga$, which is a promising channel for the discovery of the
lightest CP--even MSSM Higgs boson at the LHC and the SSC. The effects of the
left--right scalar mixing are small in most of parameter space. However, there
exist regions where the mixing is important. Due to mixing, there can be large
enhancements of the cross section in a region of parameter space where the
no--mixing approximation yields a value that is too low for experimental
discovery of the $\hnl$ at the LHC and the SSC.


title: Angular and energy correlations in Higgs decay

abstract:
  We discuss how correlations among momenta of the decay products may yield
information about the CP-parity of the Higgs particle. These are correlations
of decay planes defined by the momenta of pairs of particles as well as
correlations between energy differences. Our study includes finite-width
effects. In the narrow-width approximation the angular correlations coincide
with previously reported results. The correlations between energy differences
turn out to be a much better probe for CP determination than the previously
suggested angular correlations, especially for massive Higgs bosons.


title: Numerical Evolution of General Relativistic Voids

abstract:
  In this paper, we study the evolution of a relativistic, superhorizon-sized
void embedded in a Friedmann-Robertson-Walker universe. We numerically solve
the spherically symmetric general relativistic equations in comoving,
synchronous coordinates. Initially, the fluid inside the void is taken to be
homogeneous and nonexpanding. In a radiation- dominated universe, we find that
radiation diffuses into the void at approximately the speed of light as a
strong shock---the void collapses. We also find the surprising result that the
cosmic collapse time (the $1^{\rm st}$-crossing time) is much smaller than
previously thought, because it depends not only on the radius of the void, but
also on the ratio of the temperature inside the void to that outside. If the
ratio of the initial void radius to the outside Hubble radius is less than the
ratio of the outside temperature to that inside, then the collapse occurs in
less than the outside Hubble time. Thus, superhorizon-sized relativistic void
may thermalize and homogenize relatively quickly. These new simulations revise
the current picture of superhorizon-sized void evolution after first-order
inflation.


title: Supersymmetry and the Nelson-Barr Mechanism

abstract:
  One possible solution to the strong CP problem is that CP is an exact
symmetry, spontaneously broken at some scale. Some years ago, Nelson and Barr
suggested a mechanism for obtaining $\theta=0$ at tree level in this framework,
and showed that radiative corrections were small in some non-supersymmetric
models. Further investigations suggested that the same could be true in
supersymmetric theories. In this note, we show that these analyses assumed an
extraordinarily high degree of degeneracy among squark masses and among other
supersymmetry breaking parameters. We argue, using naturalness as well as
expectations from string theory, that this is not very plausible.


title:
Detecting the Supersymmetric Higgs Bosons: An Overview and the Role of
  $\gam\gam$ Collisions

abstract:
  I summarize the abilities of LEP-II, the SSC/LHC hadron colliders, and a
future high energy $\epem$ collider (NLC) to detect the Higgs bosons of the
Minimal Supersymmetric Model (MSSM). I then review the unique capabilities of a
back-scattered laser beam facility (BSLBF) at the NLC for detecting the heavier
neutral Higgs bosons (the $\hh$ and $\ha$) of the MSSM. A BSLBF could well
allow $\hh$ and $\ha$ discovery via inclusive $\gam\gam\rta \hh,\ha$ production
out to masses of order $0.8\sqrt s$, \ie\ roughly $400\gev$, at the NLC. In
addition, a BSLBF allows one to check for CP violation in the neutral Higgs
sector; such CP violation is predicted to be absent in the MSSM. (Full
postscript file available upon request. Macropackage phyzzx.tex required. To
appear in Proceedings of 23rd INFN Eloisatron Workshop.)


title: Electroweak Reactions in the Non-Perturbative Regime of QCD

abstract:
  In the first part of these lectures, I consider chiral perturbation theory in
the presence of matter fields. It allows to systematically work out the
consequences of the broken chiral symmetry of QCD. As examples, threshold pion
photo- and electroproduction and (spin-flip) nucleon Compton scattering are
considered. The second part deals with the quark structure of the nucleon at
low energies. The various electromagnetic and weak form factors are discussed.
It is shown how parity-violating electron and (anti)neutrino scattering off
nucleons and nuclei can be used as a tool to pin down strange matrix elements
of the proton. The calculation of QED, QCD and heavy quark corrections to these
processes is also touched upon. (Lectures given at the XXXII. Internationale
Universit{\"a}tswochen f{\"u}r Kern- und Teilchenphysik, Schladming, Austria,
February 24- March 5, 1993).


title:
Determination of $Z'$ Gauge Couplings to Quarks and Leptons at Future
  Hadron Colliders

abstract:
  We point out that at future hadron colliders the ratio of cross sections for
$pp\to Z'\to \ell^+\ell^-$ in two rapidity bins is a useful probe of the
relative couplings of the $Z'$ to $u$ and $d$ quarks. Combined with the
forward-backward asymmetry, the rare decay modes $Z'\to W \ell\nu_\ell$, and
three associated productions $pp\to Z'V$ ($V=Z,W,\gamma$), and assuming
inter-family universality, small $Z-Z'$ mixing, and the $Z'$ charge commuting
with the $SU_{2L}$ generators, three out of four normalized couplings could be
extracted. An analysis of the statistical uncertainties expected for the above
probes at the LHC for typical models with $M_{Z'}\simeq1$ TeV shows that one
lepton coupling and two combinations of quark couplings could be determined to
around 5\%, 20\%, and 30\%, respectively. This allows for a clear distinction
between models.


title:
Possible huge enhancement in the radiative decay of the weal W boson
  into the charmed $D_{s} $ meson

abstract:
  We point out that the rare decay mode $W^{\pm} \rightarrow \gamma +
D^{\pm}_{s} $ could be spectacularly enhanced, with a branching ratio around
$10^{-6} $ which is three order of magnitude larger than previous predictions.
Its observation will determine the W boson mass with great accuracy, providing
additional high precision tests of the standard model, as well as reveal
eventual deviation from the trilinear non-abelian gauge coupling.


title: Flavor Democracy in Standard Models at High Energies

abstract:
  It is possible that the standard model (SM) is replaced around some
transition energy $\E_{tr}$ by a new, possibly Higgsless, ``flavor gauge
theory'' such that the Yukawa (running) parameters of SM at $E \sim \E_{tr}$
show up an (approximate) flavor democracy (FD). We investigate the latter
possibility by studying the renormalization group equations for the Yukawa
couplings of SM with one and two Higgs doublets, by evolving them from given
physical values at low energies ($E \simeq 1 GeV$) to $\E_{tr}$ ($ \sim
\E_{pole}$) and comparing the resulting fermion masses and CKM matrix elements
at $E \simeq \E_{tr}$ for various $m_t^{phy}$ and ratios $v_u/v_d$ of vacuum
expectation values. We find that the minimal SM and the closely related SM with
two Higgs doublets (type I) show increasing deviation from FD when energy is
increased, but that SM with two Higgs doublets (type II) clearly tends to FD
with increasing energy - in both the quark and the leptonic sector (q-q and l-l
FD). Furthermore, we find within the type II model that, for $\E_{pole} \ll
\E_{Planck}$, $m_t^{phy}$ can be less than $200 GeV$ in most cases of chosen
$v_u/v_d$. Under the assumption that also the corresponding Yukawa couplings in
the quark and the leptonic sector at $E \simeq \E_{tr}$ are equal (l-q FD), we
derive estimates of bounds on masses of top quark and tau-neutrino, which are
compatible with experimental bounds.


title: The Hunting of the MR Model

abstract:
  We consider experimental signatures of the standard model's minimal
supersymmetric extension with a continuous $U(1)_R$ symmetry (MR model). We
focus on the ability of existing and planned electron-positron colliders to
probe this model and to distinguish it from both the standard model and the
standard model's minimal supersymmetric extension with a discrete $R$-parity.


title: On the generality of certain predictions for quark mixing

abstract:
  The relations ${ {|V_{ub}|} \over {|V_{cb}|} } = \sqrt{ { m_u \over m_c } }$
and ${ {|V_{td}|} \over {|V_{ts}|} } = \sqrt{ { m_d \over m_s } }$ are
significant successes of some specific models for quark masses. We show that
these relations are more general, resulting from a much wider class of models.
Consequences of these predictions for CP violating asymmetries in neutral B
meson decays are discussed.


title: Precision Tests of the Standard Model

abstract:
  The implications of recent precision $Z$-pole, $W$ mass, and weak neutral
current data for testing the standard electroweak model, constraining the $t$
quark and Higgs masses, \alsz, and grand unification are discussed. A fit to
all data yields $\siz = 0.2328 \pm 0.0007$ (\msb) or $\sinn \equiv 1 -
\mw^2/\mz^2 = 0.2267 \pm 0.0024$ (on-shell), where the uncertainties are mainly
from \mt. In the standard model one predicts $\mt = 150^{+19 + 15}_{-24 - 20}$
GeV, where the central value assumes \mh = 300 GeV and the second uncertainty
is for \mh $\ra$ 60 GeV ($-$) or 1 TeV (+). In the minimal supersymmetric
extension of the standard model (MSSM) one predicts $\mt = 134^{+23}_{-28} \pm
5$ GeV, where the difference is due the light Higgs scalar expected in the
MSSM. There is no significant constraint on \mh \ until \mt \ is known
independently.


title: Progress in QCD Using Lattice Gauge Theory

abstract:
  Review of results from lattice QCD of relevance to standard-model
phenomenology, to appear in Annual Review of Nuclear and Particle Science. KEY
WORDS: hadron masses, quark mixing (CKM) matrix, weak matrix elements, strong
coupling constant.


title: Nuclear Shadowing in a Parton Recombination Model

abstract:
  Deep inelastic structure functions $F_2^A(x)$ are investigated in a $Q^2$
rescaling model with parton recombination effects. We find that the model can
explain experimentally measured $F_2^A(x)$ structure functions reasonably well
in the wide Bjorken$-x$ range ($0.005<x<0.8$). In the very small $x$ region
($x<0.02$), recombination results are very sensitive to input sea-quark and
gluon distributions.


title: Flipped Angles and Phases: A Systematic Study

abstract:
  We discuss systematically the fermion mass and mixing matrices in a generic
\linebreak field-theoretical flipped $SU(5)$ model, with particular
applications to neutrino and baryon number-changing physics. We demonstrate
that the different quark flavour branching ratios in proton decay are related
to the Cabibbo-Kobayashi-Maskawa angles, whereas the lepton flavour branching
ratios are undetermined. The light neutrino mixing angles observable via
oscillation effects are related to the heavy conjugate (right-handed) neutrino
mass matrix, which also plays a key role in cosmological baryogenesis. The
ratios of neutrino and charged lepton decay modes in baryon decay may also be
related to neutrino oscillation parameters. Plausible Ans\"atze for the
generation structure of coupling matrices motivate additional relations between
physical observables, and yield a satisfactory baryon asymmetry.


title:
Inclusive particle production at HERA: Higher-order QCD corrections to
  the resolved quasi-real photon contribution

abstract:
  We calculate in next-to-leading order inclusive cross sections of
single-particle production via resolved photons in $ep$ collisions at HERA.
Transverse-momentum and rapidity distributions are presented and the scale
dependence is studied. The results are compared with first experimental data
from the H1 Collaboration at HERA.


title:
Complete On-Shell Renormalization Scheme for the Minimal Supersymmetric
  Higgs Sector

abstract:
  Systematic on-shell renormalization programme is carried out for the Higgs
and gauge boson sectors of the Minimal Supersymmetric Standard Model. Complete
1-loop results for the 2- and 3-point Green's functions are explicitly given.
The Higgs boson masses and the cross sections for the neutral scalar production
in the $e^+e^-$ colliders are calculated.


title:
Determination of pseudo-Goldstone boson-photon coupling by the
  differential time delay of pulsar signals

abstract:
  Pseudo-Goldstone bosons couple with photons through a P and T violating
interaction of the form ${\cal {L_I}}=g_{a\gamma \gamma}~ a F\tilde F$. Strong
magnetic fields in rotating compact stars induce a non-zero ${\vec E}\cdot{\vec
B}$ outside the stellar surface which acts as a source for the pseudo-scalar
field. Pulsar signals propagating through this pseudo-scalar `hair' suffer a
differential time lag between the left and the right circularly polarised modes
because of the P and T violating pseudoscalar boson-photon interaction.
Determination of this time lag upto a microsecond accuracy can lead to a
measurment of (or rule out) pseudo-Goldstone boson-photon coupling upto $g_{a
\gamma \gamma}\leq 4.6 \times 10^{-9}~GeV^{-1}$.


title:
Critical Analysis of Baryon Masses and Sigma-Terms in Heavy Baryon
  Chiral Perturbation Theory

abstract:
  We present an analysis of the octet baryon masses and the $\pi N$ and $KN$
$\sigma$--terms in the framework of heavy baryon chiral perturbation theory. At
next-to-leading order, ${\cal O}(q^3)$, knowledge of the baryon masses and
$\sigma_{\pi N}(0)$ allows to determine the three corresponding finite
low--energy constants and to predict the the two $KN$ $\sigma$--terms
$\sigma^{(1,2)}_{KN} (0)$. We also include the spin-3/2 decuplet in the
effective theory. The presence of the non--vanishing energy scale due to the
octet--decuplet splitting shifts the average octet baryon mass by an infinite
amount and leads to infinite renormalizations of the low--energy constants. The
first observable effect of the decuplet intermediate states to the baryon
masses starts out at order $q^4$. We argue that it is not sufficient to retain
only these but no other higher order terms to achieve a consistent description
of the three--flavor scalar sector of baryon CHPT. In addition, we critically
discuss an SU(2) result which allows to explain the large shift of $\sigma_{\pi
N}(2M_\pi^2) - \sigma_{\pi N}(0)$ via intermediate $\Delta (1232)$ states.


title: Saha and the Dyon

abstract:
  Meghnad Saha occupies a special role in the history of Indian science, having
been a pioneer in its organization already from the oppressive colonial period
and having left important legacies to post-colonial India like the Saha
Institute of Nuclear Physics. He is famous for his research in astrophysics,
and has also made important, but less well-known contributions to magnetic
monopole theory. This article attempts an elementary survey of this theory and
its implications with special emphasis on Saha's work and argues that the
latter has had wide ranging consequences for fundamental physics.


title: Axion Miniclusters and Bose Stars

abstract:
  Evolution of inhomogeneities in the axion field around the QCD epoch is
studied numerically, including for the first time important non-linear effects.
It is found that perturbations on scales corresponding to causally disconnected
regions at $T \sim 1 \, {\rm GeV}$ can lead to very dense axion clumps, with
present density $\rho_a \ga 10^{-8}\,{\rm g \, cm^{-3}}$. This is high enough
for the collisional $2a \rightarrow 2a$ process to lead to Bose--Einstein
relaxation in the gravitationally bound clumps of axions, forming Bose stars.


title:
Gauge Invariance and Anomalous Dimensions of a Light-Cone Wilson Loop in
  Light-Like Axial Gauge

abstract:
  Complete two-loop calculation of a dimensionally regularized Wilson loop with
light-like segments is performed in the light-like axial gauge with the
Mandelstam-Leibbrandt prescription for the gluon propagator. We find an
expression which {\it exactly} coincides with the one previously obtained for
the same Wilson loop in covariant Feynman gauge. The renormalization of Wilson
loop is performed in the $\MS-$scheme using a general procedure tailored to the
light-like axial gauge. We find that the renormalized Wilson loop obeys a
renormalization group equation with the same anomalous dimensions as in
covariant gauges. Physical implications of our result for investigation of
infrared asymptotics of perturbative QCD are pointed out.


title: Possible Implications of a Light Gluino

abstract:
  Light gluinos have been suggested in order to reconcile $\alpha_s$
determinations from low energy deep inelastic experiments with those inferred
from LEP measurements. {}From this hypothesis then one expects, in unified N=1
supergravity models, that also the "photino" will be light. We show that this
possibility is not in conflict with recent LEP measurements and also that
cosmology does not necessarily rule it out in any convincing way. Moreover it
leads to $upper$ limits on the masses of the other supersymmetric fermions, for
example, the lightest chargino should be lighter than about 75 GeV}


title:
Extracting W Boson Couplings from the $e^{+}e^{-}$ Production of Four
  Leptons

abstract:
  We consider the processes $e^{+}e^{-}\rightarrow \ell^{+} \ell^{\prime -}\nu
\bar{\nu}^{\prime}$, including all possible charged lepton combinations, with
regard to measuring parameters characterizing the $W$ boson. We calculate at
what level these processes can be used to measure anamolous triple-boson
vertice coupling parameters for the cases of $e^{+}e^{-}$ colliders at 500
$GeV$ and 1 $TeV$ center of mass energies.


title:
On the electroweak phase transition in the Minimal Supersymmetric
  Standard Model

abstract:
  We study the finite-temperature effective potential of the Minimal
Supersymmetric Standard Model, in the limit of only one light Higgs boson.
Because of the large top Yukawa coupling, there can be significant differences
with respect to the Standard Model case: for given values of the Higgs and top
masses, little supersymmetry breaking in the stop sector can make the phase
transition more strongly first-order. After including the full structure of the
stop mass matrix, the most important experimental constraints and the leading
plasma effects, we find that the present limits on Higgs and squark masses are
still compatible with the scenario of electroweak baryogenesis, in a small
region of parameter space corresponding to $m_h \simlt 70 \gev$ and $\msba
\simlt 105 \gev$.


title: Supersymmetric Higgs Bosons: a Theoretical Introduction

abstract:
  After an introduction to the Higgs sector of supersymmetric extensions of the
Standard Model, recent results on radiative corrections to Higgs boson masses
and couplings are reviewed. The phenomenology of supersymmetric Higgs searches
at large hadron colliders and at a possible linear $\epem$ collider is also
described. (Invited talk at the Workshop `Ten years of SUSY confronting
experiment', CERN, 7--9 September 1992, to appear in the Proceedings)


title: Self-mass for Massive Quark

abstract:
  We study the behavior of the self-mass for a quark with a current mass larger
than $\Lambda_QCD$, as a function of its Euclidean momentum and mass, in QCD.
An expression for the Bethe-Salpeter kernel of the Schwinger-Dyson (SD)
equation valid in both the infrared and ultraviolet regions is obtained based
on a renormalization group analysis. The resulting SD equation is solved
numerically. It is found that the quark constituent mass at zero momentum is
substantially enhanced due to its effective gauge interaction. The solution in
the ultraviolet region agrees well with the known asymptotic solution. The
self-mass scales exactly as the on-shell current mass at a fixed momentum.


title: Stitching the Yukawa Quilt

abstract:
  We develop a systematic analysis of quark mass matrices which, starting with
the measured values of quark masses and mixing angles, allows for a model
independent search for all possible (symmetric or hermitian) mass matrices
having texture zeroes at the unification scale. A survey of all six and five
texture zero structures yields a total of five possible solutions which may be
distinguished by improved measurements of the CKM matrix elements and which may
readily be extended to include lepton masses with the Georgi-Jarlskog texture.
The solutions naturally suggest a parameterisation for the mass matrices based
on a perturbative expansion and we present some speculations concerning the
origin of such structure.


title: Multiscalar amplitudes to all orders in perturbation theory

abstract:
  A method for calculating loop amplitudes at the multiboson threshold is
presented, based on Feynman-diagram techniques. We explicitly calculate the
one-loop amplitudes in both $\phi^4$-symmetric and broken symmetry cases, using
dimensional regularization. We argue that, to all orders in the perturbation
expansion, the unitarity-violating behaviour of the tree-order amplitudes
persists.


title: Nullification of multi-Higgs threshold amplitudes in the Standard Model

abstract:
  We show that nullification of all tree-order threshold amplitudes involving
Higgs particles in the Standard Model occurs, provided that certain equations
relating the masses of all existing elementary particles to the mass of the
Higgs scalar are satisfied. The possible role of these relations in restoring
the high-multiplicity unitarity and their phenomenological relevance are
briefly discussed.


title: Beyond the Standard Model with Effective Lagrangians

abstract:
  An Effective Lagrangian description is useful for describing potential
physics beyond the Standard Model. The method is illustrated by reference to
interactions among the electroweak bosons ($W^\pm$ \& $Z^0$). The resulting
estimates of the magnitude of these corrections suggest that they would be at
best marginally detectable at high energy $e^-e^+$ colliders or hadron
colliders. In loop calculations, contrary to lore, such deviations from
Standard Model self-couplings never give observable corrections that grow as a
power of the scale $\Lambda$ at which new physics enters, so there are never
effects proportional to powers of $\Lambda/M_W$.


title: R-Parity Violating SUSY Model

abstract:
  This is a phenomenological review of $R$ parity violating SUSY models, with
particular emphasis on explicit $R$ parity violation.


title: Radiative Electroweak Parameters

abstract:
  The status of the present precision measurements of electroweak observables
is reviewed with specific reference to the radiative parameters $S,T,U$ or
equivalently $\epsilon_1,\epsilon_2,\epsilon_3$. The significance of the
obliqueness hypothesis is underlined and the importance of the ``local fit''
method of extracting these parameters from the data is emphasized. Possible new
physics implications are briefly touched upon.


title: Chiral Symmetry and Electroweak pi,K,eta Processes

abstract:
  Recently the development of chiral perturbation theory has allowed the
generation of rigorous low-energy theorems for various hadronic processes based
only on the chiral invariance of the underlying QCD Lagrangian. Herein we
examine the experimental implications of chiral symmetry in the regime of
electroweak Goldstone boson interactions. Contribution to BNL Hadronic Beam
Physics Workshop.


title: Isospin splitting in heavy baryons and mesons

abstract:
  A recent general analysis of light-baryon isospin splittings is updated and
extended to charmed baryons.
  The measured $\Sigma_c$ and $\Xi_c$ splittings stand out as being difficult
to understand in terms of two-body forces alone.
  We also discuss heavy-light mesons; though the framework here is necessarily
less general, we nevertheless obtain some predictions that are not strongly
model-dependent.


title: Baryogenesis, Domain Walls and the Role of Gravity

abstract:
  It has been recently speculated that global symmetries are broken by gravity.
We propose a scenario for the generation of the baryon asymmetry in the early
Universe in which the domain walls predicted by theories with discrete
symmetries become unstable due to these Planck scale effects. The relative
motion of the decaying walls can provide a mechanism for the departure from
thermal equilibrium necessary to have a nonvanishing baryon asymmetry. In
particular, we implement this idea within the frameworks of the Left-Right and
Quark-Lepton symmetric models.


title: From Kaon-Nuclear Interactions to Kaon Condensation

abstract:
  An effective chiral Lagrangian in heavy-fermion formalism whose parameters
are constrained by kaon-nucleon and kaon-nuclear interactions next to the
leading order in chiral expansion is used to describe kaon condensation in
dense ``neutron star" matter. The critical density is found to be robust with
respect to the parameters of the chiral Lagrangian and comes out to be
$\rho_c\sim (3 - 4)\rho_0$. Once kaon condensation sets in, the system is no
longer composed of neutron matter but of nuclear matter. Possible consequences
on stellar collapse with the formation of compact ``nuclear stars" or
light-mass black holes are pointed out.


title: See-saw Enhancement of Lepton Mixing

abstract:
  The see-saw mechanism of neutrino mass generation may enhance lepton mixing
up to maximal even if the Dirac mass matrices of leptons have structure similar
to that in the quark sector. Two sets of conditions for such an enhancement are
found. The first one includes the see-saw generation of heavy Majorana masses
for right-handed neutrinos and a universality of
  Yukawa couplings which can follow from the unification of neutrinos with new
superheavy neutral leptons. The second set is related to lepton number symmetry
of the Yukawa interactions in the Dirac basis of neutrinos. Models which
realize these conditions have strong hierarchy or strong degeneration of
Majorana masses of the right-handed neutrinos.


title:
Effective-Lagrangian approach to precision measurements: the anomalous
  magnetic moment of the muon

abstract:
  We investigate the use of effective Lagrangians to describe the effects on
high-precision observables of physics beyond the Standard Model. Using the
anomalous magnetic moment of the muon as an example, we detail the use of
effective vertices in loop calculations. We then provide estimates of the
sensitivity of new experiments measuring the muon's $ g - 2 $ to the scale of
physics underlying the Standard Model.


title: Heavy Top Quark Effects in Vertices with Light External Fermions

abstract:
  We extend our previous work on non-linear realization of the top quark field,
which is a consequence of its being much heavier than any other scales. One
loop effective Lagrangian to account for virtual top effects is constructed in
this article, for processes where there are two external fermions, as well as
any number of bosons. Particularly, we focus on those terms which have power
dependence on the top mass $m_t$.


title: Integral correlation measures for multiparticle physics

abstract:
  We report on a considerable improvement in the technique of measuring
multiparticle correlations via integrals over correlation functions. A
modification of measures used in the characterization of chaotic dynamical
sytems permits fast and flexible calculation of factorial moments and cumulants
as well as their differential versions. Higher order correlation integral
measurements even of large multiplicity events such as encountered in heavy ion
collisons are now feasible. The change from ``ordinary'' to ``factorial''
powers may have important consequences in other fields such as the study of
galaxy correlations and Bose-Einstein interferometry.


title: Search for the intermediate Mass Higgs Signal at TeV $e\gamma$ colliders

abstract:
  The intermediate mass Higgs (IMH) can be abundantly produced through the
process $e^-\gamma \rightarrow W^-H\nu$ at TeV $e^-\gamma$ colliders, which are
realized by the laser back-scattering method. We search for the signature of
$W^-H \rightarrow (jj)(b\bar b)$ plus missing transverse momentum, with and
without considering the $b$-tagging. We also analyse all the potential
backgrounds from $e^-\gamma \rightarrow W^-Z\nu,\,W^-W^+e^-,\,ZZe^-,\, \bar t
b\nu$ and $t\bar t e^-$. With our selective acceptance cuts these backgrounds
are reduced to a manageable level. We find that for the entire intermediate
mass range 60 -- 150~GeV the Higgs discovery should be viable. We also present
detail formulas for the helicity amplitudes of these processes.


title: Power Corrections to QCD Sum Rules for Compton Scattering

abstract:
  We extend previous work on sum rules for the invariant amplitudes of pion
Compton scattering by deriving a complete lowest order perturbative spectral
function - and its leading non perturbative power corr ections - for a specific
combination of the two helicities $(H_1 + H_2)$ of this process. Using some
properties of a modified version of the Borel transform, we develop a method of
calculation of the gluonic corrections which can be easily extended to other
similar reactions, such as proton Compton scattering. A preliminary comparison
of the new sum rule with the pion form factor sum rule is made.


title: New Bounds on Leptoquark Couplings

abstract:
  We derive new bounds on scalar leptoquark couplings from K^0 K^0 bar, D^0 D^0
bar and B^0 B^0 bar mixing. Although leptoquarks contribute to these processes
only at one loop, their contribution is large, due to the lack of GIM
cancelation. Our bounds have two important features: (i) They bound g^4/M^2, in
contrast to the hitherto known bounds on g^2/M^2, and are consequently stronger
at high masses. (ii) The bound from D^0 D^0 bar mixing is the first FCNC bound
in the up sector for chirally-coupled leptoquarks, and is similar in strength
to the K^0 K^0 bar and B^0 B^0 bar bounds. Together, these bounds strongly
constrain any leptoquark that couples to left handed quarks.


title: Decorated-box-diagram-contributions to Bhabha scattering. (I)

abstract:
  We evaluate, in the high-energy limit, $s\gg|t|\gg m^2\gg\lambda^2$, the sum
of amplitudes corresponding to a class of Feynman diagrams describing two-loop
virtual photonic corrections to Bhabha scattering. The diagrams considered are
box and crossed box diagrams with an extra photon decorating one of the fermion
lines. The mathematical method employed is that of Mellin transforms. In the
eikonal approximation, this sum of two-loop amplitudes has previously been
evaluated, and found to be equal to the sum of the box and crossed box
amplitudes, multiplied by the electric form factor of the electron. We obtain a
similar factorization, but with the form factor replaced by another expression
involving the logarithms $\log(\lambda^2/m^2)$ and $\log(\lambda^2/|t|)$.


title: Phenomenological Description of an Unstable Fermion

abstract:
  We present a phenomenological description for an unstable fermion based upon
one-loop renormalization of quantum field theory. It is emphasized that wave
function renormalization can introduce important $CP$-conserving and
$CP$-violating phases. Implications for the study of $CP$ violation are
examined. Applications are given to $CP$-violating asymmetries in the $t$
decays: $t\to bW^+, bH^+$, in which we show that a naive calculation following
the standard rule either is incomplete or violates $CPT$.


title: Skyrmions and Semilocal Strings in Cosmology

abstract:
  It has been pointed out that cosmic string solutions can exist in gauge field
theories with broken symmetry even when $\pi _1(G/H)$ is trivial. The stability
of such semilocal defects is not guaranteed by topology and depends on
dynamical considerations. In the literature it has been tacitly assumed that if
stable, such strings would form in the Early Universe in a manner analogous to
the formation of a network of more robust topologically-stable strings. In this
paper we find that except for unnaturally small values of the correlation
length, a network of semilocal strings does not form. Instead, delocalized
skyrmionic string configurations, which expand with the Hubble flow, dominate.


title: Calculated Electron Fluxes at Airplane Altitudes

abstract:
  A precision measurement of atmospheric electron fluxes has been performed on
a Japanese commercial airliner (Enomoto, {\it et al.}, 1991). We have performed
a monte carlo calculation of the cosmic ray secondary electron fluxes expected
in this experiment. The monte carlo uses the hadronic portion of our neutrino
flux cascade program combined with the electromagnetic cascade portion of the
CERN library program GEANT. Our results give good agreement with the data,
provided we boost the overall normalization of the primary cosmic ray flux by
12\% over the normalization used in the neutrino flux calculation.


title: Accurate Neutralino Relic Density Computations in Supergravity Models

abstract:
  We investigate the question of the proper thermal averaging of neutralino
annihilation amplitudes which possess poles and thresholds, as they impact on
the calculated neutralino relic density and therefore on the cosmological
viability of supersymmetric models. We focus on two typical resonances, namely
the $Z$ boson and the lightest Higgs boson ($h$). In the context of
supergravity models with radiative electroweak symmetry breaking, an
exploration of the whole parameter space of the model is possible and the
overall relevance of these sophisticated analyses can be ascertained. As an
example we chose the minimal $SU(5)$ supergravity model since the presence of
such poles is essential to obtain a cosmologically acceptable model. We find
that the proper thermal averaging is important for individual points in
parameter space and that the fraction of cosmologically acceptable points is
increased somewhat by the accurate procedure. However, qualitatively the new
set of points is very similar to that obtained previously using the usual
series approximations to the thermal average. We conclude that all
phenomenological analyses based on the previously determined cosmologically
allowed set remain valid.


title: Static Properties of Quark Solitons

abstract:
  It has been conjectured that at distances smaller than the confinement scale
but large enough to allow for nonperturbative effects, QCD is described by an
effective $SU(N_c {\times} N_f)_L\times SU(N_c {\times} N_f)_R$ chiral
Lagrangian. The soliton solutions of such a Lagrangian are extended objects
with spin ${1\over 2}$. For $N_c{=}3$, $N_f{=}3$ they are triplets of color and
flavor and have baryon number ${1\over3}$, to be identified as constituent
quarks. We investigate in detail the static properties of such
constituent-quark solitons for the simplest case $N_f{=}1, N_c{=}3$. The mass
of these objects comes from the energy of the static soliton and from quantum
effects, described semiclassically by rotation of collective coordinates around
the classical solution. The quantum corrections tend to be large, but can be
controlled by exploring the Lagrangian's parameter space so as to maximize the
inertia tensor. We comment on the acceptable parameter space and discuss the
model's further predictive power.


title: Exact Supersymmetric Amplitude for \kkb\/ and \bbb\/ Mixing

abstract:
  We present the most general supersymmetric amplitude for \kkb\/ and \bbb\/
mixing resulting from gluino box diagrams. We use this amplitude to place
general constraints on the magnitude of flavor-changing squark mass mixings,
and compare these constraints to theoretical predictions both in and beyond the
Minimal Supersymmetric Standard Model.


title:
Parameter--free calculation of $D \rightarrow P P$ in a weak--gauged
  $U(4)_L \otimes U(4)_R$ Chiral Lagrangian Model

abstract:
  We analyze the decay modes of charmed mesons into two--pseudoscalars in a
weak--gauged U(4)_L x U(4)_R chiral lagrangian model. The calculation is free
of unknown parameters and only requires as inputs the masses of pseudoscalars
and the decay constant of the pion. The general pattern of the results at
leading order compares reasonably well with the experimental data.


title: Electroweak Magnetism, W-condensation and Anti-Screening

abstract:
  We review how external magnetic fields act as perfect probes of the
non-abelian nature of the electroweak theory.


title:
The Process " Pbar P -> E- E+ " with Polarized Initial Particles and
  Proton Form Factors in Time-Like Region

abstract:
  The discussion on the asymptotical behaviour of the form factors in the
space-like and time-like regions have been corrected and clarified. Fig.3 has
been replaced by an improved analysis of the data.


title: Probes of Heavy Meson Substructure in $e^+ e^-$ annihilation

abstract:
  We apply Heavy Quark Effective Theory to the production of $0^-$ and $1^-$
$Q\bar{q}$ states in $e^+ e^-$ annihilation. We show that HQET implies that the
electric quadrupole amplitudes vanish and we propose tests for this theory. We
also show how HQET can be applied to distinguish the $^3D_1$ and $^3S_1$
$Q\bar{Q}$ states.


title: Unified Universal Seesaw Models

abstract:
  A set of Grand Unified Theories based upon the gauge groups $SU(5)_\L \times
SU(5)_\R$, $SO(10)_\L \times SO(10)_\R$ and $SU(4)_\C \times SU(4)_\L \times
SU(4)_\R$ is explored. Several novel features distinguish these theories from
the well-known $SU(5)$, $SO(10)$ and $SU(4)_\C \times SU(2)_\L \times SU(2)_\R$
models which they generalize. Firstly, Standard Model quarks and leptons are
accompanied by and mix with heavy $SU(2)_\L \times SU(2)_\R$ singlet partners.
The resulting fermion mass matrices are seesaw in form. Discrete parity
symmetries render the determinants of these mass matrices real and eliminate CP
violating gauge terms. The unified seesaw models consequently provide a
possible resolution to the strong CP problem. Secondly, $\sinsq$ at the
unification scale is numerically smaller than the experimentally measured $Z$
scale value. The weak angle must therefore increase as it evolves down in
energy. Finally, proton decay is suppressed by small seesaw mixing factors in
all these theories.


title: Top Quark and Charged Higgs: Linked by Radiative Corrections

abstract:
  Some aspects of the phenomenology of the top quark and the charged Higgs are
studied, emphasizing relations due to radiative corrections. Production
mechanisms at the SSC are mentioned, and decay modes are analyzed including
radiative corrections to the charged Higgs mass and couplings. The constraints
due to the decay b-> s \gamma are discussed. Calculations are performed in the
context of the Minimal Supersymmetric Model.


title: QCD Predictions for Lepton Spectra in Inclusive Heavy Flavour Decays

abstract:
  We derive the lepton spectrum in semileptonic beauty decays from a
nonperturbative treatment of QCD; it is based on an expansion in $1/m_Q$ with
$m_Q$ being the heavy flavour quark mass. The leading corrections arising on
the $1/m_Q$ level are completely expressed in terms of the difference in the
mass of the heavy hadron and the quark. Nontrivial effects appear in $1/m_Q^2$
terms affecting mainly the endpoint region; they are different for meson and
baryon decays as well as for beauty and charm decays.


title: Why a Scalar Explanation of the L3 Events is Implausible

abstract:
  We investigate the question of whether an additional light neutral scalar can
explain the $l^+ l^- \gamma \gamma$ events with high invariant mass photon
pairs recently observed by the L3 collaboration. We parameterize the low energy
effects of the unknown dynamics in terms of higher dimensional effective
operators. We show that operators which allow for the scalar to be produced and
decay into photon pairs will allow other observable processes that should have
been seen in current experiments.


title: Tau Polarimetry with Inclusive Decays

abstract:
  The spin asymmetry parameter $A_\tau$ characterizing the angular distribution
of the total hadron momentum in the decay of a polarized tau can be calculated
rigorously using perturbative QCD and the operator product expansion.
Perturbative QCD corrections to the free quark result $A_\tau = 1/3$ can be
expressed as a power series in $\alpha_s(M_\tau)$ and nonperturbative QCD
corrections can be expanded systematically in powers of $1/M_\tau^2$. The QCD
prediction is $A_\tau = 0.41 \pm 0.02$. In the decay of a high energy tau into
hadrons, the value of the hadronic energy distribution $dR_\tau/dz$ evaluated
at the maximum hadronic energy fraction $z = 1$ can also be calculated
rigorously from QCD.


title: Observing the Inflaton Potential

abstract:
  We show how observations of the density perturbation (scalar) spectrum and
the gravitational wave (tensor) spectrum allow a reconstruction of the
potential responsible for cosmological inflation. A complete functional
reconstruction or a perturbative approximation about a single scale are
possible; the suitability of each approach depends on the data available.
Consistency equations between the scalar and tensor spectra are derived, which
provide a powerful signal of inflation.


title: Constraints on Majoron Models, Neutrino Masses and Baryogenesis

abstract:
  We derive strong contraints on the Yukawa couplings and the vacuum
expectation value in the singlet majoron model, taking into account the
possibility of a small gravitationally induced mass for the majoron. If the
present baryon asymmetry was created earlier than at the electroweak phase
transition, then to preserve it from the combined effects of lepton number
violating interactions and electroweak sphalerons, we find that stringent
constraints on the Yukawa couplings, $h < 10^{-7}$, and the majoron scale, $v_s
< v_{EW}$, must be satisfied. We also carefully rederive baryogenesis bounds on
neutrino masses, finding that in general they apply not to the masses
themselves, but only to related parameters, and they are numerically somewhat
less stringent than has previously been claimed.


title: Reduced Effective Lagrangians

abstract:
  Effective Lagrangians, including those that are spontaneously broken, contain
redundant terms. It is shown that the classical equations of motion may be used
to simplify the effective Lagrangian, even when quantum loops are to be
considered.


title: Phenomenology of Spin Zero Mesons and Glueballs

abstract:
  We discuss the phenomenology of scalar and pseudoscalar mesons, emphasizing
those which do not carry manifest flavor quantum numbers. Many of the
properties of these mesons are still not fully understood. Some of them
probably do not have the usual two-quark (quark-antiquark) structure, but may
be mixed with glueball states or other exotics. %, hybrids, or four-quark
states. We construct or discuss simple models for these mesons and point out
which measurements can shed light on their composition.


title: Quark correlation functions in deep inelastic semi-inclusive processes

abstract:
  We investigate one-particle semi-inclusive processes in lepton-hadron
scattering. In unpolarized scattering order $Q^{-1}$ corrections appear only
when transverse momenta are detected. We consider the twist two and three
matrix elements and calculate the semi-inclusive structure functions in terms
of quark correlation functions. We find that at twist three level not only the
standard quark distribution and fragmentation function contribute, but also two
new transverse "profile functions". We demonstrate explicit gauge invariance of
the hadronic tensor at the twist three level. The results of our approach are
used to calculate expressions for some cross sections for semi-inclusive
processes.


title:
Strongly Interacting W's and Z's and the Existence of a Heavy Fourth
  Generation of Fermions

abstract:
  By employing the dictum that axiomatic principles are devoid of predictive
power, we find that the elastic unitarity constraint, applied to strong
W$_L$W$_L$ scattering, does not alter the assumed spectrum of intermediate
states. We consider intermediate states involving a heavy Higgs and heavy
fermions of a hypothetical fourth generation doublet. In contrast to recent
studies, we find no p-wave resonance, and therefore no violation of the S
parameter upper bound. We conclude that the elastic unitarity constraint sheds
no light on the existence of a heavy fourth generation.


title: On the Evaluation of Thermal Corrections to False Vacuum Decay Rates

abstract:
  We examine the computation of the nucleation barrier used in the expression
for false vacuum decay rates in finite temperature field theory. By a detailed
analysis of the determinantal prefactor, we show that the correct bounce
solution used in the computation of the nucleation barrier should not include
loop corrections coming from the scalar field undergoing decay. Temperature
corrections to the bounce appear from loop contributions from other fields
coupled to the scalar field. We compute the nucleation barrier for a model of
scalar fields coupled to fermions, and compare our results to the expression
commonly used in the literature. We find that, for large enough self-couplings,
the inclusion of scalar loops in the expression of the nucleation barrier leads
to an underestimate of the decay rate in the neighborhood of the critical
temperature.


title: SUSY signals at HERA in the no-scale flipped SU(5) supergravity model

abstract:
  Sparticle production and detection at HERA are studied within the recently
proposed no-scale flipped $SU(5)$ supergravity model. Among the various
reaction channels that could lead to sparticle production at HERA, only the
following are within its limit of sensitivity in this model: $e^-p\to \tilde
e^-_{L,R}\chi^0_i+X, \tilde \nu_e\chi^-_1+X$, where $\chi^0_i(i=1,2)$ are the
two lightest neutralinos and $\chi^-_1$ is the lightest chargino. We study the
elastic and deep-inelastic contributions to the cross sections using the
Weizs\"acker-Williams approximation. We find that the most promising
supersymmetric production channel is right-handed selectron ($\tilde e_{R}$)
plus first neutralino ($\chi^0_1$), with one hard electron and missing energy
signature. The $\tilde\nu_e\chi^-_1$ channel leads to comparable rates but also
allows jet final states. A right-handedly polarized electron beam at HERA would
shut off the latter channel and allow preferentially the former one. With an
integrated luminosity of ${\cal L}=100\ipb$, HERA can extend the present LEPI
lower bounds on $m_{\tilde e_R}, m_{\tilde\nu_e},m_{\chi^0_1}$ by
$\approx25\GeV$, while ${\cal L}=1000\ipb$ will make HERA competitive with
LEPII. We also show that the Leading Proton Spectrometer (LPS) at HERA is an
excellent supersymmetry detector which can provide indirect information about
the sparticle masses by measuring the leading proton longitudinal momentum
distribution.


title: Decoupling in Non-Perturbative Background Fields: the Thermal Sphaleron

abstract:
  Standard decoupling of heavy fermions may fail when there are
non-perturbative variations in a scalar field which gives masses to the
fermions. One situation of phenomenological relevance is the case of sphalerons
in the presence of fermions at finite temperatures. The free energy of a simple
model is determined using a non-perturbative technique to study the effect of
fermions on the scalar field. The effects of quantum and thermal fermionic
fluctuations on the free energy of the thermal sphaleron are calculated,
including contributions from the gradients of the scalar field to all orders.


title: Measuring Charm and Bottom Quark Masses

abstract:
  The meaning and the extraction of heavy quark masses are discussed. A simple
production model is presented which incorporates the running of the heavy quark
mass into perturbative calculations. The model offers the possibilities of (i)
understanding the differing charmed mass values extracted from different
experiments, (ii) determining the short--distance mass relevent to quark mass
matrix and mixing angle studies, and (iii) determining the long--distance charm
mass, which determines the charm quark threshold and sensitively affects the
extraction of $\sin^2\theta_w $. Threshold and forward angle production offer
the best possibilities to test the model and extract meaningful charm/bottom
masses.


title: Large Multiplicity Gluon Production in QCD

abstract:
  We compute the approximate cross section $\sigma_n^{(0)}$ for producing $n-2$
{\it resolved} gluons in a gluon-gluon collision, using the Parke-Taylor
formula regularized in a Lorentz invariant manner. We find, in double leading
logarithm approximation, that \[ \sigma_{n}^{(0)} \approx \frac{1}{s} \left(
\frac{N_c\alpha_s}{2 \pi \sqrt{12}}
  \ \ln^{2} (s/s_{cut})\right)^{n-2}\ \ , \] where $\sqrt{s_{cut}}$ is the
minimum invariant mass for a resolved gluon pair. There is no factor of
$1/(n-2)!$ multiplying the expression. We present additional numerical results,
and comment on their implications for perturbative calculations of $n$-jet
cross sections at colliders.


title:
Ratios of $W^\pm\gamma$ and $Z\gamma$ Cross Sections: New Tools in
  Probing the Weak Boson Sector at the Tevatron

abstract:
  The ratios ${\cal R}_{\gamma ,\ell}=B(Z\to\ell^+\ell^-)\cdot\sigma(Z\gamma)
/\allowbreak B(W\to\ell\nu)\cdot\sigma(W^\pm\gamma)$, ${\cal R}_{\gamma , \nu}=
B(Z\to\bar\nu\nu)\cdot\sigma(Z\gamma)/\allowbreak B(W\to\ell\nu)\cdot\sigma(W^
\pm\gamma)$, ${\cal R}_{W\gamma}=\sigma(W^\pm\gamma)/\allowbreak\sigma(W^\pm)$,
and ${\cal R}_{Z\gamma}=\sigma(Z\gamma)/\allowbreak\sigma(Z)$ are studied as
tools to probe the electroweak boson self-interactions. As a function of the
minimum photon transverse momentum, ${\cal R}_{\gamma ,\ell}$ and ${\cal R}_{
\gamma ,\nu}$ are found to directly reflect the radiation zero present in $W^
\pm\gamma$ production in the Standard Model. All four ratios are sensitive to
anomalous $WW\gamma$ and/or $ZZ\gamma/Z\gamma\gamma$ couplings. The sensitivity
of the cross section ratios to the cuts imposed on the final state particles,
as well as the systematic uncertainties resulting from different
parametrizations of parton distribution functions, the choice of the
factorization scale $Q^2$, and from higher order QCD corrections are explored.
Taking into account these uncertainties, sensitivity limits for anomalous three
gauge boson couplings, based on a measurement of the cross section ratios with
an integrated luminosity of 25~pb$^{-1}$ at the Tevatron, are estimated.


title: The Electroweak Chiral Lagrangian and New Precision Measurements

abstract:
  A revised and complete list of the electroweak chiral lagrangian operators up
to dimension-four is provided. The connection of these operators to the $S$,
$T$ and $U$ parameters and the parameters describing the triple gauge boson
vertices $WW\gamma$ and $WWZ$ is made, and the size of these parameters from
new heavy physics is estimated using a one flavor-doublet model of heavy
fermions. The coefficients of the chiral lagrangian operators are also computed
in this model.


title:
Re-Examination of Generation of Baryon and Lepton Number Asymmetries by
  Heavy Particle Decay

abstract:
  It is shown that wave function renormalization can introduce an important
contribution to the generation of baryon and lepton number asymmetries by heavy
particle decay. These terms, omitted in previous analyses, are of the same
order of magnitude as the standard terms. A complete cancellation of leading
terms can result in some interesting cases.