Eur. Phys. J. A 24, s2.33-s2.34 (2005)
DOI: 10.1140/epjad/s2005-04-006-2

Transverse single spin asymmetry in elastic electron-proton scattering

M. Gorchtein¹, P.A.M. Guichon² and M. Vanderhaeghen<sup>3

1</sup>  Università di Genova and Sezione INFN di Genova, 16146 Genova, Italy
²  SPhN/DAPNIA, CEA Saclay, F-91191 Gif sur Yvette, France
³  College of William and Mary & Jefferson Laboratory, Newport News, VA 23606, USA

(Received 15 October 2004 / Published online 08 February 2005)

Abstract

We discuss the two-photon exchange contribution to observables which involve lepton helicity flip in elastic lepton-nucleon scattering. This contribution is accessed through the single spin asymmetry for a lepton beam polarized normal to the scattering plane. We estimate this beam normal spin asymmetry at large momentum transfer using a parton model and we express the corresponding amplitude in terms of generalized parton distributions.

PACS: 25.30.Bf Elastic electron scattering - 12.38.Bx Perturbative calculations - 13.40Gp Electromagnetic form factors

© Società Italiana di Fisica, Springer-Verlag 2005