653 research outputs found
The triple pomeron interaction in the perturbative QCD
The triple pomeron interaction is studied in the perturbative approach of
BFKL-Bartels. At finite momentum transfers the contribution
factorizes in the standard manner with a triple-pomeron vertex proportional to
. At the contribution is finite, although it grows faster
with energy than for finite and does not factorize.Comment: 17 pages, 4 figures, LATE
A New Odderon Solution in Perturbative QCD
We present and discuss a new bound state solution of the three gluon system
in perturbative QCD. It carries the quantum numbers of the odderon, has
intercept at one and couples to the impact factor .Comment: 11 pages, latex, 1 figur
Regge Asymptotics of Scattering with Flavour Exchange in QCD
The contribution to the perturbative Regge asymptotics of the exchange of two
reggeized fermions with opposite helicity is investigated. The methods of
conformal symmetry known for the case of gluon exchange are extended to this
case where double-logarithmic contributions dominate the asymptotics. The Regge
trajectories at large momentum transfer are calculated.Comment: 18 pages LATEX, 3 figures using package FEYNMAN, N3-9
The Reggeon 2 Reggeons Particle vertex in the Lipatov effective action formalism
The vertex for gluon emission during the splitting of a reggeized gluon into
two is constructed in the framework of Lipatov effective action formalism. Its
reduction to a pure transverse form for the diffractive amplitude gives the
standard Bartels vertex plus an additional contribution corresponding to the
emission from a pointlike splitting vertex. This additional contribution turns
out to be given by a longitudinal integral divergent both in the ultraviolet
and infrared. A certain specific recipe for this part, including the principal
value prescription for the integration, allows to eliminate this unwanted
contribution.Comment: 4 figures; misprints corrected; to be published in Eur.Phys.J.
Vector Meson Photoproduction from the BFKL Equation II: Phenomenology
Diffractive vector meson photoproduction accompanied by proton dissociation
is studied for large momentum transfer. The process is described by the
non-forward BFKL equation which we use to compare to data collected at the HERA
collider.Comment: 39 pages, 29 figure
Deformed Spectral Representation of the BFKL Kernel and the Bootstrap for Gluon Reggeization
We investigate the space of functions in which the BFKL kernel acts. For the
amplitudes which describe the scattering of colorless projectiles it is
convenient to define, in transverse coordinates, the Moebius space in which the
solutions to the BFKL equation vanish as the coordinates of the two reggeized
gluons coincide. However, in order to fulfill the bootstrap relation for the
BFKL kernel it is necessary to modify the space of functions. We define and
investigate a new space of functions and show explicitly that the bootstrap
relation is valid for the corresponding spectral form of the kernel. We
calculate the generators of the resulting deformed representation of the
sl(2,C) algebra.Comment: 22 pages, 1 figur
QCD perturbation theory at large orders with large renormalization scales in the large limit
We examine the QCD perturbation series at large orders, for different values
of the 'large renormalization scale'. It is found that if we let this
scale grow exponentially with the order, the divergent series can be turned
into an expansion that converges to the Borel integral, with a certain cut off.
In the case of the first IR renormalon at , corresponding to a
dimension four operator in the operator product expansion, this qualitatively
improves the perturbative predictions. Furthermore, our results allow us to
establish formulations of the principle of minimal sensitivity and the fastest
apparent convergence criterion that result in a convergent expansion.Comment: 14 pages, 5 figures, elaborated conclusion
t-channel Approach to Reggeon Interactions in QCD
Starting from the multi-Regge effective action for high-energy scattering in
QCD a -channel approach can be developed which is similar to the approach by
White based on general Regge arguments. The BFKL kernel of reggeized gluon
interaction, contributions to the reggeized gluon vertex
function and the one-loop correction to the BFKL kernel are considered. The
conditions are discussed under which this approach can provide a simple
estimante of the next-to-leading logarithmic corrections to the BFKL
perturbative pomeron intercept.Comment: latex , 17 figures appended as compressed uuencoded eps file
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
A QCD motivated model for soft interactions at high energies
In this paper we develop an approach to soft scattering processes at high
energies,which is based on two mechanisms: Good-Walker mechanism for low mass
diffractionand multi-Pomeron interactions for high mass diffraction. The
pricipal idea, that allows us to specify the theory for Pomeron interactions,
is that the so called soft processes occur at rather short distances
(r^2 \propto 1 /^2 \propto \alpha'_\pom \approx 0.01 GeV^{-2}), where
perturbative QCD is valid. The value of the Pomeron slope \alpha'_\pom was
obtained from the fit to experimental data. Using this theoretical approach we
suggest a model that fits all soft data in the ISR-Tevatron energy range, the
total, elastic, single and double diffractive cross sections, including
dependence of the differential elastic cross section, and the mass dependence
of single diffraction. In this model we calculate the survival probability of
diffractive Higgs production, and obtained a value for this observable, which
is smaller than 1% at the LHC energy range.Comment: 33pp,20 figures in eps file
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