Andreas Freund

Proof of factorization for deeply virtual Compton scattering in QCD

We show that factorization holds for the deeply virtual Compton scattering amplitude in QCD, up to power suppressed terms, to all orders in perturbation theory. The theorem applies to the production of off-shell photons as well as real photons. We give a detailed treatment of the situation where one of the two partons joining the parton density to the hard scattering has zero longitudinal momentum. {copyright} {ital 1999} {ital The American Physical Society}

Modeling generalized parton distributions to describe deeply virtual Compton scattering data

We present a new model for generalized parton distributions (GPDs), based on the aligned jet model, which successfully describes the deeply virtual Compton scattering (DVCS) data from H1, ZEUS, HERMES and CLAS. We also present an easily implementable and flexible algorithm for their construction. This new model is necessary since the most widely used models for GPDs, which are based on factorized double distributions, cannot, in their current form, describe the DVCS data when employed in a full QCD analysis. We demonstrate explicitly the reason for the shortcoming in the data description. We also highlight several non-perturbative input parameters which could be used to tune the GPDs, and the

NONDIAGONAL PARTON DISTRIBUTIONS IN THE LEADING LOGARITHMIC APPROXIMATION

t

Proof of factorization for electroproduction of multiple mesons and exclusive gamma* gamma production of multiple hadrons

-dependence, to the DVCS data using a fitting procedure.

Deeply virtual compton scattering at HERA – A probe of asymptotia

In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution g(x 1 , x 2 , t, µ 2) can be well approximated at small x by the conventional gluon density xG(x, µ 2).Abstract In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution g ( x 1 , x 2 , t , μ 2 ) can be well approximated at small x by the conventional gluon density xG ( x , μ 2 ).

On the extraction of skewed parton distributions from experiment

In the following, we will present a generalization of the proof of factorization for electroproduction of vector mesons to the production of several mesons such as

STUDY OF NONDIAGONAL PARTON DISTRIBUTION MODELS

\pi^+\pi^-

Single spin asymmetry in deeply virtual Compton scattering

and a proof of factorization for exclusive

Extraction of skewed parton distributions from experiment

\gamma^* \gamma

Direct estimation of sizes of higher-order graphs

production of several hadrons for example