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

Abstract

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.

Authors:
;
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Energy Research (ER) (US)
OSTI Identifier:
766460
Report Number(s):
JLAB-THY-00-37; DOE/ER/40150-1760; hep-ph/0010296; RUB-TPII-17/00
TRN: AH200037%%418
DOE Contract Number:  
AC05-84ER40150
Resource Type:
Journal Article
Resource Relation:
Other Information: No journal information given for this prepring; PBD: 1 Oct 2000
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AMPLITUDES; FACTORIZATION; GAUGE INVARIANCE; LIGHT CONE; MATRIX ELEMENTS; QUANTUM CHROMODYNAMICS; SPECTRAL FUNCTIONS; TREES

Citation Formats

Radyushkin, A V, and Weiss, C. DVCS amplitude at tree level: Transversality, twist-3, and factorization. United States: N. p., 2000. Web.
Radyushkin, A V, & Weiss, C. DVCS amplitude at tree level: Transversality, twist-3, and factorization. United States.
Radyushkin, A V, and Weiss, C. 2000. "DVCS amplitude at tree level: Transversality, twist-3, and factorization". United States. https://www.osti.gov/servlets/purl/766460.
@article{osti_766460,
title = {DVCS amplitude at tree level: Transversality, twist-3, and factorization},
author = {Radyushkin, A V and Weiss, C},
abstractNote = {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.},
doi = {},
url = {https://www.osti.gov/biblio/766460}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Oct 01 00:00:00 EDT 2000},
month = {Sun Oct 01 00:00:00 EDT 2000}
}