2,554 research outputs found
Hard diffraction -- 20 years later
The idea of diffractive processes with a hard scale involved, to resolve the
underlying parton dynamics, was published 1985 and experimentally verified
1988. Today hard diffraction is an active research field with high-quality data
and new theoretical models. The trend from Regge-based pomeron models to
QCD-based parton level models has given insights on QCD dynamics involving
perturbative gluon exchange mechanisms, including the predicted BFKL-dynamics,
as well as novel ideas on non-perturbative colour fields and their
interactions. Extrapolations to the LHC include the interesting possibility of
diffractive Higgs production.Comment: 14 pages, 19 figures. Invited talk at XXII International Symposium on
Lepton-Photon Interactions at High Energy, Uppsala, Sweden, June 30-July 5,
200
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
Can one probe the structure function of the pomeron?
We discuss whether the diffractive structure functions defined by current
experiments at HERA are indeed probing the partonic structure function of the
pomeron. We observe that the {\it pseudorapidity} cuts commonly employed
require that the struck parton in the pomeron be far off mass shell in sizeable
regions of parameter space. As a result an interpretation in terms of
constituent partons within the pomeron is inadequate. One may nevertheless use
a partonic description for the {\it amplitude} for virtual photon-pomeron
scattering to compute a diffractive structure function for pseudorapidity gap
events. The resulting form may have significant scaling violation.Comment: 11 pages LaTeX, uses epsf, 5 eps figures appended as a uuencoded
gzipped tarred fil
Rapidity Gaps in DIS through Soft Colour Interactions
We present a new mechanism for the creation of large rapidity gaps in DIS
events at HERA. Soft colour interactions between perturbatively produced
partons and colour-charges in the proton remnant, modifies the colour structure
for hadronization giving colour singlet systems that are well separated in
rapidity. An explicit model is presented that, although the detailed results
depend on the initial state parton emission, can describe both the observed
rapidity gaps and, in addition, the forward energy flow in an inclusive event
sample.Comment: 4 pages Latex, 4 encapsulated Postscript figures, uses qcdparis.sty,
tar-compressed and uuencoded with uufiles, Presented by GI at workshop `DIS
and QCD', Paris, April 1995, minor Postscript problem fixe
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