55 research outputs found
Quark-Antiquark-Gluon Jets in DIS Diffractive Dissociation
We study the diffractive production of jets with large transverse
momenta in the region of large diffractive masses (small ). Cross
sections for transverse and longitudinal photons are obtained in the leading
log 1/x_{\fP} and log approximation, keeping all powers in log
. We perform a numerical study and illustrate the angular
distribution of the three jets. We also estimate the integrated diffractive
three jet cross section and compare with the dijet cross section obtained
before.Comment: 28 pages (Latex), 20 figures (Postscript
The colour dipole approach to small-x processes
We explain why it is possible to formulate a wide variety of high energy
(small-x) photon-proton processes in terms of a universal dipole cross section
and compare and contrast various parameterizations of this function that exist
in the literature.Comment: 6 pages, latex, 2 figures. Contribution to Durham Collider Workshop
(Sept 99) proceeding
A QCD analysis of diffractive deep-inelastic scattering data
We perform a novel type of analysis of diffractive deep-inelastic scattering
data, in which the input parton distributions of the Pomeron are parameterised
using the perturbative QCD expressions. In particular, we treat individually
the components of the Pomeron of different size. We are able to describe
simultaneously both the recent ZEUS and H1 diffractive data. In addition to the
usual two-gluon model for the perturbative Pomeron, we allow for the
possibility that it may be made from two sea quarks.Comment: 13 pages, 5 figures. Version published in Eur. Phys. J.
Azimuthal Distribution of Quark-Antiquark Jets in DIS Diffractive Dissociation
We investigate the azimuthal distribution of quark-antiquark jets in DIS
diffractive dissociation with large transverse momentum. In this kinematical
region the matrix element is expressed in terms of the gluon structure
function. For the transverse part of the cross section we find a -distribution with the maximum at , i.e.\ the jets
prefer a direction perpendicular to the electron plane. This is in contrast to
boson gluon fusion where the jet cross section for transversely
polarized bosons peaks at and . We discuss the origin of
this striking difference and present numerical results relevant for the
diffractive dissociation at HERA.Comment: 12 pages, latex, 7 figure
Quark-Antiquark Production in DIS Diffractive Dissociation
We calculate the cross section for the production of two jets with large
transverse momenta \kf^2 in DIS diffractive dissociation for both transverse
and longitudinally polarized photons. The scale which defines the hardness of
the pomeron is found to be \kf^2\frac{Q^2+M^2}{M^2}. We present analytic
expressions and discuss numerical results relevant for the diffractive
dissociation at HERA.Comment: 16 pages, latex, 14 figures include
Diffractive parton distributions from perturbative QCD
The asymptotic collinear factorisation theorem, which holds for diffractive
deep-inelastic scattering, has important modifications in the sub-asymptotic
HERA regime. We use perturbative QCD to quantify these modifications. The
diffractive parton distributions are shown to satisfy an inhomogeneous
evolution equation. We emphasise that it is necessary to include both the
gluonic and sea-quark t-channel components of the perturbative Pomeron. The
corresponding Pomeron-to-parton splitting functions are derived in the
Appendix.Comment: 34 pages, 13 figures. Version published in Eur. Phys. J.
Energy Dependence of the Contribution of Pion Exchange to Large-Rapidity-Gap Events in Deep Inelastic Scattering
We study the energy dependence of the contribution of pion exchange to
large-rapidity-gap events in deep inelastic scattering. The results show that
this contribution can be quite significant at low energy and that the LRG
events observed by E665 collaboration in \mu Xe and \mu D interactions at 490
can be reasonably well described in terms of meson exchange. We also show
that the distribution of the maximum rapidity for all hadrons is quite
different from that for charged hadrons only and that the former exhibits also
shoulder-like structure for events at 490 similar to that at HERA.Comment: 12 pages, 4 figures, Phys. Rev. D (in press
Diffractive Production of Vector Mesons at Large t
The cross section for elastic vector meson production in photon-proton
interactions at large is considered using the exact analytic solution of
the BFKL equation in the azimuthally symmetric limit. We use a
non-relativistic model for the vector meson production and find a small
shrinkage in the -distribution with increasing energy.Comment: 13 pages plus 3 figures (uuencoded
On the exciton binding energy in a quantum well
We consider a model describing the one-dimensional confinement of an exciton
in a symmetrical, rectangular quantum-well structure and derive upper and lower
bounds for the binding energy of the exciton. Based on these bounds, we
study the dependence of on the width of the confining potential with a
higher accuracy than previous reports. For an infinitely deep potential the
binding energy varies as expected from at large widths to at
small widths. For a finite potential, but without consideration of a mass
mismatch or a dielectric mismatch, we substantiate earlier results that the
binding energy approaches the value for both small and large widths,
having a characteristic peak for some intermediate size of the slab. Taking the
mismatch into account, this result will in general no longer be true. For the
specific case of a quantum-well
structure, however, and in contrast to previous findings, the peak structure is
shown to survive.Comment: 32 pages, ReVTeX, including 9 figure
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