575 research outputs found
Unitarization of Total Cross Section and Coherent Effect in pQCD
A formula to unitarize the leading-log BFKL-Pomeron amplitude is derived
using a coherent property of two-body collision in the peripheral region. This
procedure also allows an algebraic characterization of the Reggeon in QCD based
on color, instead of the total angular momentum of the gluons being exchanged.Comment: Talk given at the DIS99 Meeting in Zeuthen, Germany. April, 1999. 3
page
A Higgs Test of Horizontal Symmetry
Identical interactions found in the three families of quarks and leptons
suggest the presence of a horizontal symmetry. We discuss how such a symmetry
can be tested by measuring the decay rates of Higgs into fermion pairs, and the
Higgs production cross section. Depending on the details, there is a chance
that the decay widths to the bottom-pair and the tau-pair may be down by more
than a factor of 3 or more compared to the usual values, and the fusion
production cross section of the Higgs also altered. Whatever the outcome, such
a test also serves to constraint horizontal symmetry models.Comment: version to be published in Physics Letter
String Organization of Field Theories: Duality and Gauge Invariance
String theories should reduce to ordinary four-dimensional field theories at
low energies. Yet the formulation of the two are so different that such a
connection, if it exists, is not immediately obvious. With the Schwinger
proper-time representation, and the spinor helicity technique, it has been
shown that field theories can indeed be written in a string-like manner, thus
resulting in simplifications in practical calculations, and providing novel
insights into gauge and gravitational theories. This paper continues the study
of string organization of field theories by focusing on the question of local
duality. It is shown that a single expression for the sum of many diagrams can
indeed be written for QED, thereby simulating the duality property in strings.
The relation between a single diagram and the dual sum is somewhat analogous to
the relation between a old- fashioned perturbation diagram and a Feynman
diagram. Dual expressions are particularly significant for gauge theories
because they are gauge invariant while expressions for single diagrams are not.Comment: 20 pages in Latex, including seven figures in postscrip
Perturbative Computation of Glueball Superpotentials
Using N=1 superspace techniques in four dimensions we show how to
perturbatively compute the superpotential generated for the glueball superfield
upon integrating out massive charged fields. The technique applies to arbitrary
gauge groups and representations. Moreover we show that for U(N) gauge theories
admitting a large N expansion the computation dramatically simplifies and we
prove the validity of the recently proposed recipe for computation of this
quantity in terms of planar diagrams of matrix integrals.Comment: 15 Pages, 2 Figure
On the Existence of the Quantum Action
We have previously proposed a conjecture stating that quantum mechanical
transition amplitudes can be parametrized in terms of a quantum action. Here we
give a proof of the conjecture and establish the existance of a local quantum
action in the case of imaginary time in the Feynman-Kac limit (when temperature
goes to zero). Moreover we discuss some symmetry properties of the quantum
action.Comment: revised version, Text (LaTeX
Magic Neutrino Mass Matrix and the Bjorken-Harrison-Scott Parameterization
Observed neutrino mixing can be described by a tribimaximal MNS matrix. The
resulting neutrino mass matrix in the basis of a diagonal charged lepton mass
matrix is both 2-3 symmetric and magic. By a magic matrix, I mean one whose row
sums and column sums are all identical. I study what happens if 2-3 symmetry is
broken but the magic symmetry is kept intact. In that case, the mixing matrix
is parameterized by a single complex parameter , in a form discussed
recently by Bjorken, Harrison, and Scott.Comment: Two references added. To appear in Physics Letters
Testing J/psi Production and Decay Properties in Hadronic Collisions
The polar and azimuthal angular distributions for the lepton pair arising
from the decay of a J/psi meson produced at transverse momentum p_T balanced by
a photon [or gluon] in hadronic collisions are calculated in the color singlet
model (CSM). It is shown that the general structure of the decay lepton
distribution is controlled by four invariant structure functions, which are
functions of the transverse momentum and the rapidity of the J/psi. We found
that two of these structure functions [the longitudinal and transverse
interference structure functions] are identical in the CSM. Analytical and
numerical results are given in the Collins-Soper and in the Gottfried-Jackson
frame. We present a Monte Carlo study of the effect of acceptance cuts applied
to the leptons and the photon for J/psi+ gamma production at the Tevatron.Comment: 22 pages (LaTeX) plus 11 postscript figures, MAD/PH/822, YUMS94-11.
Figures are available from the authors or as a compressed tar file via
anonymous ftp at phenom.physics.wisc.edu in directory
{}~pub/preprints/madph-94-822-figs.tar.
Unitarized Diffractive Scattering in QCD and Application to Virtual Photon Total Cross Sections
The problem of restoring Froissart bound to the BFKL-Pomeron is studied in an
extended leading-log approximation of QCD. We consider parton-parton scattering
amplitude and show that the sum of all Feynman-diagram contributions can be
written in an eikonal form. In this form dynamics is determined by the phase
shift, and subleading-logs of all orders needed to restore the Froissart bound
are automatically provided. The main technical difficulty is to find a way to
extract these subleading contributions without having to compute each Feynman
diagram beyond the leading order. We solve that problem by using nonabelian cut
diagrams introduced elsewhere. They can be considered as colour filters used to
isolate the multi-Reggeon contributions that supply these subleading-log terms.
Illustration of the formalism is given for amplitudes and phase shifts up to
three loops. For diffractive scattering, only phase shifts governed by one and
two Reggeon exchanges are needed. They can be computed from the
leading-log-Reggeon and the BFKL-Pomeron amplitudes. In applications, we argue
that the dependence of the energy-growth exponent on virtuality for
total cross section observed at HERA can be interpreted as the
first sign of a slowdown of energy growth towards satisfying the Froissart
bound. An attempt to understand these exponents with the present formalism is
discussed.Comment: 41 pages in revtex preprint format, with 10 figure
J/Psi Decay Lepton Distribution in Hadronic Collisions
We propose the measurement of the decay angular distribution of leptons from
J/Psi's produced at high transverse momentum balanced by a photon [or gluon] in
hadronic collisions. The polar and azimuthal angular distribution are
calculated in the color singlet model (CSM). It is shown that the general
structure of the decay lepton distribution is controlled by four invariant
structure functions, which are functions of the transverse momentum and the
rapidity of the J/Psi. We found that two of these structure functions [the
longitudinal and transverse interference structure functions] are identical in
the CSM. We present analytical and numerical results in the Collins-Soper and
in the Gottfried-Jackson frame.Comment: 8 pages, RevTex, 2 figures
The large-N(c) nuclear potential puzzle
An analysis of the baryon-baryon potential from the point of view of
large-N(c) QCD is performed. A comparison is made between the N(c)-scaling
behavior directly obtained from an analysis at the quark-gluon level to the
N(c)-scaling of the potential for a generic hadronic field theory in which it
arises via meson exchanges and for which the parameters of the theory are given
by their canonical large-N(c) scaling behavior. The purpose of this comparison
is to use large-N(c) consistency to test the widespread view that the
interaction between nuclei arises from QCD through the exchange of mesons.
Although at the one- and two-meson exchange level the scaling rules for the
potential derived from the hadronic theory matches the quark-gluon level
prediction, at the three- and higher-meson exchange level a generic hadronic
theory yields a potential which scales with N(c) faster than that of the
quark-gluon theory.Comment: 17 pages, LaTeX, 5 figure
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