Two-loop coefficient function for DVCS: vector contributions
V. M. Braun, A. N. Manashov, S. Moch, J. Schoenleber
Abstract
A bstract Using the approach based on conformal symmetry we calculate the two-loop coefficient function for the vector flavor-nonsinglet contribution to deeply-virtual Compton scattering (DVCS). The analytic expression for the coefficient function in momentum fraction space is presented in the $$ \overline{\mathrm{MS}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>MS</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> scheme. The corresponding next-to-next-to-leading order correction to the Compton form factor ℋ for a simple model of the generalized parton distribution appears to be rather large: a factor two smaller than the next-to-leading order correction, approximately ∼ 10% of the tree level result in the bulk of the kinematic range, for Q 2 = 4 GeV 2 .