 
Summary: AdS black disk model for smallx DIS
Lorenzo Cornalba, Miguel S. Costa1
and Jo~ao Penedones2
1
Centro de F´isica do Porto e Departamento de F´isica da Faculdade de Ci^encias da Universidade do Porto,
Rua do Campo Alegre 687, 4169007 Porto, Portugal
2
Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 931064030, USA
Using the approximate conformal invariance of QCD at high energies, we study saturation in Deep
Inelastic Scattering (DIS) from the dual AdS perspective. We consider a simple AdS black disk model
to describe the small Bjorken x regime inside the saturation region. Deep inside saturation the trans
verse and longitudinal structure functions have the same power law scaling, FT FL x
, where
the exponent is related to the expansion rate of the black disk with energy. Furthermore, in this
kinematical regime the ratio FL/FT is given by the universal value 1+
3+
, independently of the target.
We also consider virtual photonphoton scattering at high energies and obtain explicit expressions
and ratios for the total cross sections of transversally and longitudinally polarized photons in terms
of the single parameter of the black disk model.
