%0 Journal Article
%A Llanes Estrada, Felipe José
%A Brodsky, Stanley J
%A Szczepaniak, Adam P
%T Local two-photon couplings and the J=0 fixed pole in real and virtual Compton scattering
%D 2009
%@ 1550-7998
%U https://hdl.handle.net/20.500.14352/43970
%X The local coupling of two photons to the fundamental quark currents of a hadron gives an energy-independent contribution to the Compton amplitude proportional to the charge squared of the struck quark, a contribution which has no analog in hadron scattering reactions. We show that this local contribution has a real phase and is universal, giving the same contribution for real or virtual Compton scattering for any photon virtuality and skewness at fixed momentum transfer squared t. The t dependence of this J=0 fixed Regge pole is parameterized by a yet unmeasured even charge conjugation form factor of the target nucleon. The t=0 limit gives an important constraint on the dependence of the nucleon mass on the quark mass through the Weisberger relation. We discuss how this 1/x form factor can be extracted from high-energy deeply virtual Compton scattering and examine predictions given by models of the H generalized parton distribution.
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