Hadronic properties of the photon

Currently it is no doubt that high energy photons (real or virtual) have a hadronic component leading to photon shadowing in its interaction with nuclei. We shortly consider the difficulties appeared in the models like vector dominance model (VDM) and stress that these problems can be solved in a color dipole model inspired by Quantum Chromodynamics (QCD). From the other hand, the color dipole model allows one to investigate the impact of vector meson polarization on their interaction with nucleons and nuclei, the challenge which is crucial for studying, for instance, such a fundamental effect as color transparency.

BACKWARD RAPIDITY DISTRIBUTIONS IN COLOR DIPOLE MODEL

The color dipole model is traditionally applied to forward rapidities. Alternatively, we employ the dipole model to obtain backward rapidity distributions. We have chosen to work with dilepton production in pAu and pp collisions at RHIC and LHC energies. The results are best understood with the help of a nuclear modification factor RpA as a function of transverse momentum and of rapidity. As it is found, dilepton production at backward rapidities is very dependent on nuclear effects.