Generalised parton distributions at HERA and prospects for COMPASS

• DOI: 10.1016/j.physletb.2007.10.036
• Publication Date: 2007-10-26T09:58:47Z
• Authors: L. Schoeffel
• Keywords: DGLAP; Ansatz; ZEUS (particle detector); Compass; Parton shower

We present a model of generalised parton distributions based on forward ansatz in the DGLAP region. discuss some aspects parametrisations, as dependence t, with factorised and non-factorised approaches, where t is square four-momentum exchanged at hadron vertex. The predictions this are then compared DVCS cross sections from H1 ZEUS, related observable, skewing factor, defined following ratio imaginary amplitudes: R≡ImA(γ∗+p→γ+p)|t=0/ImA(γ∗+p→γ∗+p)|t=0. It an interesting quantity including both non-forward kinematics non-diagonal effects. Finally, we beam charge asymmetry, which certainly most sensitive observable to different hypothesis needed GPDs parametrisations. show that approximations done for lead significant differences HERMES kinematic domain prospects given COMPASS.