Exclusive ${\rho }^0$ electroproduction on the proton at CLAS

Abstract

The $ep\to e^{\prime }p{\rho }^0$ reaction has been measured, using the 5.754 GeV electron beam of Jefferson Lab and the CLAS detector. This represents the largest ever set of data for this reaction in the valence region. Integrated and differential cross sections are presented. The $W$, $Q^2$ and $t$ dependences of the cross section are compared to theoretical calculations based on $t$-channel meson-exchange Regge theory on the one hand and on quark handbag diagrams related to Generalized Parton Distributions (GPDs) on the other hand. The Regge approach can describe at the $\approx$ 30% level most of the features of the present data while the two GPD calculations that are presented in this article which succesfully reproduce the high energy data strongly underestimate the present data. The question is then raised whether this discrepancy originates from an incomplete or inexact way of modelling the GPDs or the associated hard scattering amplitude or whether the GPD formalism is simply inapplicable in this region due to higher-twists contributions, incalculable at present.

29 pages, 29 figures

References in corpus (9)

• The role of the quark and gluon GPDs in hard vector-meson electroproduction
• Deeply Virtual Compton Scattering Beam-Spin Asymmetries
• Exclusive rho^0 production in deep inelastic scattering at HERA
• A fitter code for Deep Virtual Compton Scattering and Generalized Parton Distributions
• Implication of the overlap representation for modelling generalized parton distributions
• Electroproduction of $\varphi (1020)$ mesons at $1.4\le Q^2\le$ GeV${}^2$ measured with the CLAS spectrometer
• Some numerical studies of the evolution of generalized parton distributions
• Discussion on the recent proton-DVCS results of Jefferson Lab
• Exclusive rho^0 electroproduction on the proton : GPDs or not GPDs ?

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