174 research outputs found
Soft Colour Interactions and Diffractive Hard Scattering at the Tevatron
We make a brief presentation of the soft colour interactions models, the Soft
Colour Interaction and the Generalised Area Law, and summarise the results when
they are applied to p-pbar scattering. The models give a good description of
the Tevatron data on production of W, bottom and jets in diffractive events, as
well as jets with two rapidity gaps, alternatively leading particles. We also
give predictions for diffractive J/psi production and discuss diffractive Higgs
production at the Tevatron and LHC.Comment: 5 pages, 4 figures, uses JHEP style. Talk presented at the
International Europhysics Conference on High Energy Physics (EPS HEP 2001),
Budapest, 12-18 July 200
Testing the dynamics of high energy scattering using vector meson production
I review work on diffractive vector meson production in photon-proton
collisions at high energy and large momentum transfer, accompanied by proton
dissociation and a large rapidity gap. This process provides a test of the high
energy scattering dynamics, but is also sensitive to the details of the
treatment of the vector meson vertex.
The emphasis is on the description of the process by a solution of the
non-forward BFKL equation, i.e. the equation describing the evolution of
scattering amplitudes in the high-energy limit of QCD. The formation of the
vector meson and the non-perturbative modeling needed is also briefly
discussed.Comment: 17 pages, 8 figures. Brief review to appear in Mod. Phys. Lett.
Soft Colour Interactions in Non-perturbative QCD
Improved understanding of non-perturbative QCD dynamics can be obtained in
terms of soft colour exchange models. Their essence is the variation of colour
string-field topologies giving a unified description of final states in high
energy interactions. In particular, both events with and without large rapidity
gaps are obtained in agreement with data from ep at HERA and ppbar at the
Tevatron, where also the surprisingly large production rate of high-p_T
charmonium and bottomonium is reproduced.Comment: 4 pages, contribution to PANIC 99 conference proceedings, to appear
in Nucl. Phys. A. Uses espcrc1.st
Rapidity Gaps from Colour String Topologies
Diffractive deep inelastic scattering at HERA and diffractive W and jet
production at the Tevatron are well described by soft colour exchange models.
Their essence is the variation of colour string-field topologies giving both
gap and no-gap events, with a smooth transition and thereby a unified
description of all final states.Comment: 3 pages, 6 eps figures, contribution to the DIS 99 workshop
proceedings, uses npb.st
Hard diffraction from parton rescattering in QCD
We analyze the QCD dynamics of diffractive deep inelastic scattering. The
presence of a rapidity gap between the target and diffractive system requires
that the target remnant emerges in a color singlet state, which we show is made
possible by the soft rescattering of the struck quark. This rescattering is
described by the path-ordered exponential (Wilson line) in the expression for
the parton distribution function of the target. The multiple scattering of the
struck parton via instantaneous interactions in the target generates dominantly
imaginary diffractive amplitudes, giving rise to an "effective pomeron"
exchange. The pomeron is not an intrinsic part of the proton but a dynamical
effect of the interaction. This picture also applies to diffraction in
hadron-initiated processes. Due to the different color environment the
rescattering is different in virtual photon- and hadron-induced processes,
explaining the observed non-universality of diffractive parton distributions.
This framework provides a theoretical basis for the phenomenologically
successful Soft Color Interaction model which includes rescattering effects and
thus generates a variety of final states with rapidity gaps. We discuss
developments of the SCI model to account for the color coherence features of
the underlying subprocesses.Comment: 12 pages, 9 figures, REVTeX4. Somewhat expanded and modified version,
two new subsections added. To appear in PR
Prompt neutrino fluxes from atmospheric charm
We calculate the prompt neutrino flux from atmospheric charm production by
cosmic rays, using the dipole picture in a perturbative QCD framework, which
incorporates the parton saturation effects present at high energies. We compare
our results with the next-to-leading order perturbative QCD result and find
that saturation effects are large for neutrino energies above 10^6 GeV, leading
to a substantial suppression of the prompt neutrino flux. We comment on the
range of prompt neutrino fluxes due to theoretical uncertainties.Comment: 13 pages with 11 figures; expanded discussion, added references,
version to be published in Phys. Rev.
Diffractive Higgs boson production at the Tevatron and LHC
Improved possibilities to find the Higgs boson in diffractive events, having
less hadronic activity, depend on whether the cross section is large enough.
Based on the soft color interaction models that successfully describe
diffractive hard scattering at HERA and the Tevatron, we find that only a few
diffractive Higgs events may be produced at the Tevatron, but we predict a
substantial rate at the LHC.Comment: 4 pages, 4 figures, uses Revtex
Color Evaporation and Elastic Photoproduction at DESY HERA
The diffractive photoproduction of vector mesons is usually described
considering the two-gluon (Pomeron) exchange, non-diagonal parton distributions
and the contribution of the real part to the cross section. In this letter we
analyze the diffractive photoproduction of the at HERA using an
alternative model, the Color Evaporation Model (CEM), where the cross section
is simply determined by the boson-gluon cross section and an assumption for the
production of the colorless state. We verify that, similarly to the
case, the HERA data for this process can be well described by the CEM.
Moreover, we propose the analyzes of the ratio to discriminate between the distinct approaches.Comment: 7 pages, 3 figures, accepted for publication in PRD (Brief Reports
Resummation in nonlinear equation for high energy factorizable gluon density and its extension to include coherence
Motivated by forthcoming p-Pb experiments at Large Hadron Collider which
require both knowledge of gluon densities accounting for saturation and for
processes at a wide range of we study basic momentum space evolution
equations of high energy QCD factorization. Solutions of those equations might
be used to form a set of gluon densities to calculate observables in
generalized high energy factorization. Moreover in order to provide a framework
for predictions for exclusive final states in p-Pb scattering with high
we rewrite the equation for the high energy factorizable gluon density in a
resummed form, similarly to what has been done in \cite{Kutak:2011fu} for the
BK equation. The resummed equation is then extended to account for colour
coherence. This introduces an external scale to the evolution of the gluon
density, and therefore makes it applicable in studies of final states.Comment: 14 pages, appendix added, accepted for publication in JHE
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