Deep inelastic scattering cross sections from the gauge/string duality

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.Facultad de Ciencias ExactasInstituto de Física La Plat

Deep inelastic scattering off scalar mesons in the 1/N expansion from the D3D7-brane system

Deep inelastic scattering (DIS) of charged leptons off scalar mesons in the 1/N expansion is studied by using the gauge/gravity duality. We focus on the D3D7-brane system and investigate the corresponding structure functions by considering both the high energy limit and the 1/N expansion. These limits do not commute. From the D7-brane DBI action we derive a Lagrangian at sub-leading order in the D7-brane fluctuations and obtain a number of interactions some of which become relevant for two-hadron final-state DIS. By considering first the high energy limit followed by the large N one, our results fit lattice QCD data within 1.27% for the first three moments of F2 for the lightest pseudoscalar meson.Instituto de Física La Plat

Towards 1/N corrections to deep inelastic scattering from the gauge/gravity duality

1/N2 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 F1 and F2 (and also FL) are studied at subleading order in the 1/N2 expansion, in terms of q2 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/N2n and Λ2/q2 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.Facultad de Ciencias ExactasInstituto de Física La Plat

DIS off glueballs from string theory: the role of the chiral anomaly and the Chern-Simons term

We calculate the structure function F3(x, q2) of the hadronic tensor of deep inelastic scattering (DIS) of charged leptons from glueballs of N= 4 SYM theory at strong coupling and at small values of the Bjorken parameter in the gauge/string theory duality framework. This is done in terms of type IIB superstring theory scattering amplitudes. From the AdS5 perspective, the relevant part of the scattering amplitude comes from the five-dimensional non-Abelian Chern-Simons terms in the SU(4) gauged supergravity obtained from dimensional reduction on S5. From type IIB superstring theory we derive an effective Lagrangian describing the four-point interaction in the local approximation. The exponentially small regime of the Bjorken parameter is investigated using Pomeron techniques.Facultad de Ciencias ExactasInstituto de Física La Plat

Hadron structure functions at small x from string theory

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.Facultad de Ciencias ExactasInstituto de Física La Plat

Deep inelastic scattering cross sections from the gauge/string duality

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.Facultad de Ciencias ExactasInstituto de Física La Plat

Deep inelastic scattering off scalar mesons in the 1/N expansion from the D3D7-brane system

Deep inelastic scattering (DIS) of charged leptons off scalar mesons in the 1/N expansion is studied by using the gauge/gravity duality. We focus on the D3D7-brane system and investigate the corresponding structure functions by considering both the high energy limit and the 1/N expansion. These limits do not commute. From the D7-brane DBI action we derive a Lagrangian at sub-leading order in the D7-brane fluctuations and obtain a number of interactions some of which become relevant for two-hadron final-state DIS. By considering first the high energy limit followed by the large N one, our results fit lattice QCD data within 1.27% for the first three moments of F2 for the lightest pseudoscalar meson.Instituto de Física La Plat

Deep inelastic scattering from polarized spin-1/2 hadrons at low x from string theory

We study polarized deep inelastic scattering of charged leptons from spin-1/2 hadrons at low values of the Bjorken parameter and large 't Hooft coupling in terms of the gauge/string theory duality. We calculate the structure functions from type IIB superstring theory scattering amplitudes. We discuss the role of the non-Abelian Chern-Simons term and the Pauli term from the five-dimensional SU(4) gauged supergravity. Furthermore, the exponentially small-x regime where Regge physics becomes important is analyzed in detail for the antisymmetric structure functions. In this case the holographic dual picture of the Pomeron exchange is realized by a Reggeized gauge field. We compare our results with experimental data of the proton antisymmetric structure function g1, obtaining a very good level of agreement.Facultad de Ciencias ExactasInstituto de Física La Plat