Local two-photon couplings and the J=0 fixed pole in real and virtual Compton scattering
- Theory Group, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, 94025 Menlo Park, California (United States)
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.
- OSTI ID:
- 21259884
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 79, Issue 3; Other Information: DOI: 10.1103/PhysRevD.79.033012; (c) 2009 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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