Exclusive ρ0 electroproduction on the proton at CLAS
ABSTRACT The ep → e
pρ0 reaction has been measured using the 5.754GeV 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 , Q2 and t dependences of the cross-section are compared to theoretical calculations based on the 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.