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EPJ C - Particles and Fields
Particles and Fields


Eur. Phys. J. C 21, 621-629 (2001)
DOI: 10.1007/s100520100760

Twist-4 photon helicity-flip amplitude in DVCS on a nucleon in the Wandzura-Wilczek approximation

N. Kivel1 and L. Mankiewicz2, 3

1  Institut für Theoretische Physik, Universität Regensburg, 93040 Regensburg, Germany
2  N. Copernicus Astronomical Center, ul. Bartycka 18, 00-716 Warsaw, Poland
3  Andrzej Soltan Institute for Nuclear Studies, Hoza 69, 00-689 Warsaw, Poland

(Received: 2 July 2001 / Revised version: 17 July 2001 / Published online: 31 August 2001 -© Springer-Verlag / Società Italiana di Fisica 2001 )

Abstract
We computed the twist-4 part of the photon spin-flip amplitude in deeply virtual Compton scattering on a nucleon in the Wandzura-Wilczek approximation. We found a factorizable contribution, which arises from photon scattering on quarks with non-zero angular momentum along the collision axis. As the genuine twist-2 amplitude arises at the NLO, for moderate virtualities of the hard photon, $Q^2 \le 10$ GeV2, a kinematical twist-4 correction can give a numerically important contribution to the photon helicity-flip amplitude.



© Società Italiana di Fisica, Springer-Verlag 2001

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