1,417 research outputs found
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.
Remarks on the determination of the Landau gauge OPE for the Asymmetric three gluon vertex
We compute a compact OPE formula describing power corrections to the
perturbative expression for the asymmetric -renormalized
running coupling constant up to the leading logarithm. By the use of the
phenomelogical hypothesis leading to the factorization of the condensates
through a perturbative vacuum insertion, the only relevant condensate in the
game is . The validity of the OPE formula is tested by searching for a
good-quality coherent description of previous lattice evaluations of
-renormalized gluon propagator and running coupling.Comment: 12 pages, 3 figures (2 generated by the macro: axodraw.sty
The pomeron-pomeron interaction in the perturbative QCD
The pomeron-pomeron interaction is studied in the perturbative approach of
BFKL-Bartels. The total pomeron-pomeron cross-section is proportional to
where is the c.m.
energy and are the virtualities of the colliding pomerons. Upon
calculating the coefficient the cross-section is found to be of the order 2.2
mb at TeV and GeV/c.Comment: 12 pages in LaTeX plus 2 postscript file
Gluon shadowing in the low x region probed by the LHC
Starting from an unintegrated gluon distribution which satisfies a `unified'
equation which embodies both BFKL and DGLAP behaviour, we compute the shadowing
corrections to the integrated gluon in the small x domain that will be
accessible at the LHC. The corrections are calculated via the Korchegov
equation, which incorporates the leading ln(1/x) triple-Pomeron vertex, and are
approximately resummed using a simple Pade technique. We find that the
shadowing corrections to xg(x,Q^2) are rather small in the HERA domain, but
lead to a factor of 2 suppression in the region x \sim 10^-6, Q^2 \sim 4 GeV^2
accessible to experiments at the LHC.Comment: LaTeX, 8 pages including 1 figure, second version with extra comments
and references, accepted by Physics Letters
Two parton shower background for associate W Higgs production
The estimates of the background for the associate W Higgs production, which
stems from the two parton shower production. It is about 1 - 2.5 times larger
than the signal. However, this background does not depend on the rapidity
difference between the W and the pair, while the signal peaks when
the rapidity difference is zero. The detailed calculations for the enhanced
diagrams' contribution to this process, are presented, and it is shown that the
overlapping singularities, being important theoretically, lead to a negligible
contribution for the LHC range of energiesComment: 35 pages and 10 figures in eps file
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
Nonlinear QCD Evolution: Saturation without Unitarization
We consider the perturbative description of saturation based on the nonlinear
QCD evolution equation of Balitsky and Kovchegov (BK). Although the nonlinear
corrections lead to saturation of the scattering amplitude locally in impact
parameter space, we show that they do not unitarize the total cross section.
The total cross section for the scattering of a strongly interacting probe on a
hadronic target is found to grow exponentially with rapidity. The origin of
this violation of unitarity is the presence of long range Coulomb fields away
from the saturation region. The growth of these fields with rapidity is not
tempered by the nonlinearity of the BK equation.Comment: 4 pages, RevTe
Evaluation of the Maser-equipped Radar Set AN/MPS-34 and Area Precipitation Measurement Indicator: Final Report
published or submitted for publicationis peer reviewedOpe
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