Lepton-pair production in virtual Compton scattering off the proton
Abstract
We show that lepton-pair production in virtual Compton scattering offers, through interference with the well-known Bethe-Heitler process, a sensitive probe to separate longitudinal and transverse response at positive photon invariant masses. This interference can be measured directly in terms of an asymmetry. The role of off-shell effects in the NNγ vertices is investigated as well. An additional NNγγ contact term in the amplitude, included to ensure gauge invariance of the model, cancels a substantial part of the off-shell effects, but introduces ambiguities which affect observables. The response of nucleon resonances is also investigated.
- Publication:
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Physics Letters B
- Pub Date:
- February 1997
- DOI:
- 10.1016/S0370-2693(97)00389-4
- arXiv:
- arXiv:nucl-th/9701042
- Bibcode:
- 1997PhLB..402....1K
- Keywords:
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- Nuclear Theory
- E-Print:
- 8 pages, LaTeX , 2 figures. To appear in Phys. Lett. B