Differential cross sections of deep inelastic scattering of charged leptons from hadrons are investigated by using the gauge/string duality. We consider vector mesons derived from different holographic dual models obtaining a general expression. We focus on the strongly coupled regime of dual gauge theories for different values of the Bjorken parameter. We find new predictions which are particularly interesting for differential scattering cross sections of polarized leptons scattered off polarized vector mesons. We also carry out a detailed comparison of the moments of the structure functions with lattice QCD results.

Deep inelastic scattering of leptons from hadrons at small values of the Bjorken parameter x is studied from superstring theory. In particular, we focus on single-flavored scalar and vector mesons in the large N limit. This is studied in terms of different holographic dual models with flavor Dp-branes in type IIA and type IIB superstring theories, in the strong coupling limit of the corresponding dual gauge theories. We derive the hadronic tensor and the structure functions for scalar and polarized vector mesons. In particular, for polarized vector mesons we obtain the eight structure functions at small values of the Bjorken parameter. The main result is that we obtain new relations of the Callan-Gross type for several structure functions. These relations have similarities for all different Dp-brane models that we consider. This would suggest their universal character, and therefore, it is possible that they hold for strongly coupled QCD in the large N limit.10 When considering more than one Dp-brane there is an additional factor which accounts for the non-Abelian structure. In the present case N f = 1 therefore this factor is just 1.11 Note that here we use the index notation of [18].

1/N 2 corrections to deep inelastic scattering (DIS) of charged leptons from glueballs at strong coupling are investigated in the framework of the gauge/gravity duality. The structure functions F 1 and F 2 (and also F L ) are studied at subleading order in the 1/N 2 expansion, in terms of q 2 and the Bjorken parameter x. The relevant type IIB supergravity one-loop diagrams (which correspond to DIS with two-hadron final states) are studied in detail, while n-loop diagrams (corresponding to DIS with (n + 1)-hadron final states) are briefly discussed. The 1/N 2n and Λ 2 /q 2 dependence of the structure functions is analyzed. Within this context two very different limits are considered: one is the large N limit and the other one is when the virtual photon momentum transfer q is much larger than the infrared confining scale Λ. These limits do not commute.