Polarized gluon distribution in the proton from holographic light-front QCD

TL;DR

This paper derives the gluon distribution functions in the proton using holographic light-front QCD, aligning with experimental data and predicting the gluon contribution to proton spin.

Contribution

It introduces a holographic QCD approach to calculate both polarized and unpolarized gluon PDFs, incorporating constraints from the Veneziano model and Pomeron coupling.

Findings

Gluon helicity asymmetry matches experimental measurements.

Predicted gluon helicity contribution to proton spin: ΔG ≈ 0.22.

Consistent with global analyses and lattice QCD results.

Abstract

We obtain the gluon parton distribution functions (PDFs) in the proton within the extended light-front holographic QCD framework, where the proton couples with the spin-two Pomeron in Anti-de Sitter space, together with constraints imposed by the Veneziano model. The gluon helicity asymmetry, after satisfying the perturbative QCD constraints at small and large longitudinal momentum regions, agrees with existing experimental measurements. The polarized gluon distribution is consistent with global analyses. We predict the gluon helicity contribution to the proton spin, $\Delta G=0.221^{+0.056}_{-0.044}$, close to the recent analysis with updated data sets and PHENIX measurement and the lattice QCD simulations. We subsequently present the unpolarized and polarized gluon generalized parton distributions in the proton.