Generalized parton distributions in AdS/QCD

Abstract

The nucleon helicity-independent generalized parton distributions (GPDs) of quarks are calculated in the zero skewness case, in the framework of the AdS/QCD model. The present approach is based on a matching procedure of sum rules relating the electromagnetic form factors to GPDs and AdS modes.

Nucleon structure including high Fock states in AdS/QCD

“…We follow the procedure pursued in Refs. [18,20,22,24]. Dropping the vector and axial fields, and rescaling the fermionic fields as…”

“…The relevant AdS/QCD action for the description of the nucleon electromagnetic and axial form factors is constructed in terms of the fermion fields Ψ ±,τ (x, z) with spin J = 1/2 and scaling dimension τ (the isospin index corresponding to the proton and neutron components is suppressed for simplicity), the vector field V M (x, z) with spin J = 1 (holographic analogue of the electromagnetic field) and the axial field A M (x, z) (holographic analogue of the axial isovector field) [18,20,22,24]:…”

“…where ∂ = γ µ ∂ µ , δ ± = ±1 and the fermion field ψ i,τ (x, z) satisfies the following equation of motion (EOM) [18,20,22,24]:…”

“…Its presence is necessary due to the following reason. The form of the potential U F (z) is constrained in order to get solutions of the EOMs for the fermionic Kaluza-Klein (KK) modes of left and right chirality, and to have the correct asymptotics of the nucleon electromagnetic form factors at large Q 2 [18,20,22].…”

“…[9,15,18,20,22,24,25], where the mass spectrum of light and heavy baryons, and electromagnetic and gravitational form factors have been calculated. We should stress that during last years significant progress in understanding of baryon structure using methods of AdS/QCD has been achieved [20,[26][27][28][29][30][31][32].…”