We test the Gerasimov-Drell-Hearn (GDH) sum rule numerically by calculating the total photon absorption cross sections σ1/2 and σ3/2 on the nucleon via photon excitation of baryon resonances in the constituent quark model. A total of seventeen, low-lying, non-strange baryon resonances are included in this calculation. The transverse and longitudinal interference cross section, σTL 1/2, is found...

We test the Gerasimov-Drell-Hearn (GDH) sum rule numerically by calculating the total photon absorption cross sections σ1/2 and σ3/2 on the nucleon via photon excitation of baryon resonances in the constituent quark model. A total of seventeen, low-lying, non-strange baryon resonances are included in this calculation. The transverse and longitudinal interference cross section, σ 1/2, is found t...

Exclusive photoproduction of all vector mesons by real and virtual photons is considered in the Soft Dipole Pomeron model. It is emphasized that being the Pomeron in this model a double Regge pole with intercept equal to one, we are led to rising cross-sections but the unitarity bounds are not violated. It is shown that all available data for ρ, ω, φ, J/ψ and Υ in the region of energies 1.7 ≤W ...

We extend the MRS(A) set of parton distributions, which provides an upto-date description of the structure of the proton probed by hard interactions, into the region of Q below 5 GeV. After physically-motivated modifications, we obtain a smooth description of the data on the structure function F2(x,Q ) all the way from Q = 10 to 10 GeV.