Abstract
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.
Highlights
Of a spin-1/2 hadron is usually written in terms of symmetric (S) and antisymmetric (A) tensors under Lorentz indices exchange [1, 2]1
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
This approach leads to effective Lagrangians from which one can construct the leading-diagram contributions which are t-channel Feynman diagrams in the bulk theory. Their corresponding schematic representation is shown in figure 3. This is related to the Feynman diagrams presented in figure 4, corresponding to the √calculations of√the symmetric and antisymmetric structure functions in the range exp (− λ) x 1/ λ that we introduce in sections 2 and 3, respectively
Summary
We are interested in the calculation of the t-channel supergravity process at tree-level, but in this case the exchanged field has spin one. The Chern-Simons term involves the full set of non-Abelian gauge fields ACm associated to the SU(4) symmetry group. It is easy to see that the t-channel propagating gauge boson ACm can only have color numbers C = 8 or C = 15 (see for example [3, 4]). These indices are associated with two diagonal matrices in the Lie algebra of SU(4). The idea is to write a heuristic effective Lagrangian, for which we have to consider the corresponding t-channel gauge field propagator and couple the ACm coming from the Chern-Simons current to the dilatino current. A similar method can be used for the Pauli term contribution
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