DVCS amplitude at tree level: Transversality, twist-3, and factorization

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We study the virtual Compton amplitude in the generalized Bjorken region (q{sup 2} -> Infinity, t small) in QCD by means of a light-cone expansion of the product of e.m. currents in string operators in coordinate space. Electromagnetic gauge invariance (transversality) is maintained by including in addition to the twist-2 operators 'kinematical' twist-3 operators, which appear as total derivatives of twist-2 operators. The non-forward matrix elements of the elementary twist-2 operators are parametrized in terms of two-variable spectral functions (double distributions), from which twist-2 and 3 skewed distributions are obtained through reduction formulas. Our approach is equivalent to a Wandzura-Wilczek ... continued below

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Radyushkin, A.V. & Weiss, C. October 1, 2000.

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We study the virtual Compton amplitude in the generalized Bjorken region (q{sup 2} -> Infinity, t small) in QCD by means of a light-cone expansion of the product of e.m. currents in string operators in coordinate space. Electromagnetic gauge invariance (transversality) is maintained by including in addition to the twist-2 operators 'kinematical' twist-3 operators, which appear as total derivatives of twist-2 operators. The non-forward matrix elements of the elementary twist-2 operators are parametrized in terms of two-variable spectral functions (double distributions), from which twist-2 and 3 skewed distributions are obtained through reduction formulas. Our approach is equivalent to a Wandzura-Wilczek type approximation for the twist-3 skewed distributions. The resulting Compton amplitude is manifestly transverse up to terms of order t/q{sup 2}. We find that in this approximation the tensor amplitude for longitudinal polarization of the virtual photon is finite, while the one for transverse pol arization contains a divergence already at tree level. However, this divergence has zero projection on the polarization vector of the final photon, so that the physical helicity amplitudes are finite.

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439 Kilobytes pages

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  • Report No.: JLAB-THY-00-37
  • Report No.: DOE/ER/40150-1760
  • Report No.: hep-ph/0010296
  • Report No.: RUB-TPII-17/00
  • Grant Number: AC05-84ER40150
  • Office of Scientific & Technical Information Report Number: 766460
  • Archival Resource Key: ark:/67531/metadc718327

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  • October 1, 2000

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  • Sept. 29, 2015, 5:31 a.m.

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  • Feb. 5, 2016, 8:48 p.m.

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Radyushkin, A.V. & Weiss, C. DVCS amplitude at tree level: Transversality, twist-3, and factorization, article, October 1, 2000; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc718327/: accessed November 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.