Analysis of the electroproduction structure functions in the lowQ 2 region, combining the vector meson dominance and the parton model with possible scaling violation

Abstract

The nucleon structure functionF 2 is constructed and analysed for low values ofQ 2 using the generalised vector meson dominance representation with the largeQ 2 spectral function calculated from the analytic continuation of the parton model structure function. Various parametrisations of the parton distributions are considered. Possible effects of the largeQ 2 scaling violation on the lowQ 2 part of the structure function are investigated. The magnitude of the total contribution given by this asymptotic part can be as high as 50% of the vector meson contribution in the low-Q 2, low-χ region. The contribution of the valence quarks alone to the structure function at lowQ 2 turns out to be at least as important as the corresponding non-Pomeron Regge-pole-like terms coming from the vector meson part. Increase of the structure function with ν coming from the increase of the quark sea in the limit of small χ implied by QCD turns out to be relatively weak at lowQ 2. Predictions of the model are compared with available experimental data. The photoproduction cross section and the nuclear effects in the structure function are also briefly discussed.