163 research outputs found
Isolated photon + jet photoproduction as a tool to constrain the gluon distribution in the proton and the photon
We analyse how the reaction gamma p -> gamma + jet + X can serve to constrain
the gluon distributions. Our results are based on a code of partonic event
generator type which includes full NLO corrections. We conclude that there are
phase space domains in which either the gluon in the photon or the gluon in the
proton give important contributions to the cross section, which should be
observable in HERA experiments.Comment: 22 pages LaTeX, 14 figure
Real and Virtual Photoproduction of Large-pt Particles at NLO
In the first part of this paper we assess the possibility of observing the
gluon distribution in a real photon by measuring the photoproduction cross
section of large-pt photons. In the second part we calculate the virtual
photoproduction of large-pt forward pi0. The theoretical results are compared
with data and with BFKL-inspired predictions. These studies are done at the NLO
approximation.Comment: Latex, 8 pages with 4 figure
Is a Large Intrinsic k_T Needed to Describe Photon + Jet Photoproduction at HERA?
We study the photoproduction of an isolated photon and a jet based on a code
of partonic event generator type which includes the full set of next-to-leading
order corrections. We compare our results to a recent ZEUS analysis in which an
effective k_T of the incoming partons has been determined. We find that no
additional intrinsic k_T is needed to describe the data.Comment: 23 pages LaTeX, 12 figure
Beyond leading logarithm parton distributions in the photon
I discuss the parton distributions in the photon and the constraints coming from the jet production in photoproduction and in photon-photon collisions
Isolated prompt photon photoproduction at NLO
We present a full next-to-leading order code to calculate the photoproduction
of prompt photons. The code is a general purpose program of partonic event
generator type with large flexibility. We study the possibility to constrain
the photon structure functions and comment on isolation issues. A comparison to
ZEUS data is also shown.Comment: 22 pages LaTeX, 15 figure
A NLO calculation of the hadron-jet cross section in photoproduction reactions
We study the photoproduction of large-p_T charged hadrons in e p collisions,
both for the inclusive case and for the case where a jet in the final state is
also measured. Our results are obtained by a NLO generator of partonic events.
We discuss the sensitivity of the cross section to the renormalisation and
factorisation scales, and to various fragmentation function parametrisations.
The possibility to constrain the parton densities in the proton and in the
photon is assessed. Comparisons are made with H1 data for inclusive charged
hadron production.Comment: 28 pages LaTeX, 14 figure
Next-To-Leading Order Determination of Fragmentation Functions
We analyse LEP and PETRA data on single inclusive charged hadron
cross-sections to establish new sets of Next-to-Leading order Fragmentation
Functions. Data on hadro-production of large- hadrons are also used
to constrain the gluon Fragmentation Function. We carry out a critical
comparison with other NLO parametrizations
New NLO Parametrizations of the Parton Distributions in Real Photons
We present new NLO sets of parton distributions in real photons based on a
scheme invariant definition of the non-perturbative input. We compare the
theoretical predictions with LEP data and a best fit allows us to constrain the
parameters of the distributions. The shape of the gluon distribution is poorly
constrained and we consider the possibility to measure it in photoproduction
experiments. Three parametrizations which aim to take into account the
scattering of LEP data are proposed. They are compared to other NLO
parametrizations.Comment: 38 pages, 23 Postscript figures, fig. 6,7,8,9 improved, comparisons
with other NLO parametrizations, added reference
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