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Regge exchange contribution to deeply virtual compton scattering

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2009-08
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Polish Acad Sciences Inst Physics
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Recently we have shown that exclusive QCD photon-induced reactions at low Mandelstam-t are best described by Regge exchanges in the entire scaling region, and not only for low values of Bjorken- x. In this paper we explore this crucial Regge behavior in Deeply Virtual Compton Scattering from the point of view of collinear factorization, with the proton tensor written in terms of Generalized Parton Distributions, and we reproduce this feature. Thus it appears that in the Bjorken limit, a large class of hard, low-t exclusive processes are more sensitive to the meson cloud of the proton than to its fundamental quark structure. These process will then be described most efficiently by process- dependent Regge Exclusive Amplitudes rather than by universal Generalized Parton Distributions. We introduce such Regge Exclusive Amplitudes for Deeply Virtual Compton Scattering.
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We would like to thank S. Brodsky, P. Hoyer, JM. Laget, P. Kroll, D. Muller, A. Radyushkin and M. Strikman for useful discussions and comments. This work was supported in part by the US Department of Energy grant under contract DE FG0287ER40365, by the US National Science Foundation under grant PHY- 0555232, and by grants FPA 2004-02602, 2005-02327 (Spain). FJLE thanks also the Nuclear Theory Center at Indiana University and the Institute for Theoretical Physics at Graz University for their hospitality during the preparation of this work
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