167 research outputs found
On timelike and spacelike deeply virtual Compton scattering at next to leading order
We study timelike and spacelike virtual Compton scattering in the generalized
Bjorken scaling regime at next to leading order in the strong coupling
constant, in the medium energy range which will be studied intensely at JLab12
and in the COMPASS-II experiment at CERN. We show that the Born amplitudes get
sizeable O(\alpha_s) corrections and, even at moderate energies, the gluonic
contributions are by no means negligible. We stress that the timelike and
spacelike cases are complementary and that their difference deserves much
special attention
Timelike vs spacelike DVCS from JLab, Compass to ultraperipheral collisions and AFTER@LHC
Timelike and spacelike virtual Compton scattering in the generalized Bjorken
scaling regime are complementary tools to access generalized parton
distributions. We stress that the gluonic contributions are by no means
negligible, even in the medium energy range which will be studied intensely at
JLab12 and in the COMPASS-II experiment at CERN. Ultraperipheral collisions
with proton or ion beams may also be used at RHIC and at collider or fixed
target experiments at LHC.Comment: 7 pages, Presented at the Low x workshop, May 30 - June 4 2013,
Rehovot and Eilat, Israe
Spacelike and Timelike Compton Scattering: Progress report
We present some recent results on the analysis of hard scattering processes
in the framework of Generalized Parton Distributions. In particular we compute
DVCS observables on unpolarized targets with the Kroll - Goloskokov model
(suited to DVMP analysis). We also discuss NLO contributions to DVCS and TCS
processes for various kinematic settings.Comment: To appear in the proceedings of the 20th International Workshop on
Deep-Inelastic Scattering and Related Subjects held in Bonn (March 26 - 30,
2012
Extraction of the Compton Form Factor H from DVCS measurements at Jefferson Lab
In the framework of Generalised Parton Distributions, we study the
helicity-dependent and independent cross sections measured in Hall A and the
beam spin asymmetries measured in Hall B at Jefferson Laboratory. We perform a
global fit of these data and fits on each kinematical bin. We extract the real
and imaginary parts of the Compton Form Factor under the main
hypothesis of dominance of the Generalised Parton Distribution and twist 2
accuracy. We discuss our results and compare to previous extractions as well as
to the VGG model. We pay extra attention to the estimation of errors on the
extraction of .Comment: 24 pages, 8 figure
NLO QCD corrections for DVCS and TCS
The inclusion of QCD corrections to the Born amplitude of deeply virtual
Compton scattering in both spacelike (DVCS) and timelike (TCS) regimes modifies
the extraction process of generalized parton distributions (GPDs) from
observables. In particular, gluon contributions are by no means negligible even
in the medium energy range accessible at JLab12. We emphasize the
complementarity of spacelike and timelike measurements and raise the question
of factorization scale dependence of the O(alpha_S) results.Comment: 6 pages, 6 figures, Proceedings of the conference Photon 2013, 20-24
May 2013 Paris, France, to be published in Proceedings of Scienc
Test of two new parameterizations of the Generalized Parton Distribution
In 2011 Radyushkin outlined the practical implementation of the One-Component
Double Distribution formalism in realistic Generalized Parton Distribution
models. We compare the One-Component Double Distribution framework to the
standard one and compute Deeply Virtual Compton Scattering observables for
both. In particular the new implementation is more flexible, offering a greater
range of variation of the real and imaginary parts of the associated Compton
Form Factor while still allowing to recover results similar to the classical
approach. Moreover the polynomiality property is satisfied up to the highest
order. Although the comparison to experimental data may be improved, the
One-Component Double Distribution modeling is thus an attractive alternative.Comment: 38 pages, 12 figure
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