Münster 2002 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 9: Poster Session: Theory
HK 9.17: Poster
Tuesday, March 12, 2002, 10:30–12:45, Foyer Chemie
Simple picture of twist–3 effects in deeply–virtual Compton scattering — •C. Weiss2 and A.V. Radyushkin1 — 1Theory Group, Jefferson Lab, Newport News, VA 23606, USA, and Old Dominion University, Norfolk, VA 23529, USA — 2Institut für Theoretische Physik, Universität Regensburg, D–93053 Regensburg, Germany
Deeply–virtual Compton scattering (DVCS) is being widely discussed as a process which allows to measure the generalized parton distributions (GPD’s) of the nucleon. While the original QCD treatment included only the twist–2 contribution to the DVCS amplitude [1], various investigations have shown that gauge invariance requires one to include also certain kinematical twist–3 contributions, leading to more complicated relations between the GPD’s and the observable cross sections (Wandzura–Wilczek–type relations) [2]. We show that these twist–3 contributions can be understood in a simple way, as a spin rotation applied to the twist–2 part of the quark density matrix in the target [3]. This allows for a very compact representation of the twist–3 effects, as well as for a simple physical interpretation.
[1] X. Ji, Phys. Rev. D55 (1997) 7114; A. V. Radyushkin, Phys. Rev.D56 (1997) 5524
[2] A. V. Radyushkin and C. Weiss, Phys. Lett. B493 (2000) 332; Phys. Rev. D 63 (2001) 114012
[3] A. V. Radyushkin and C. Weiss, Phys. Rev. D 64 (2001) 097504