Abstract
The holographic light-front QCD framework provides a unified nonperturbative description of the hadron mass spectrum, form factors and quark distributions. In this article we extend holographic QCD in order to describe the gluonic distribution in both the proton and pion from the coupling of the metric fluctuations induced by the spin-two Pomeron with the energy momentum tensor in anti--de Sitter space, together with constraints imposed by the Veneziano model{\color{blue},} without additional free parameters. The gluonic and quark distributions are shown to have significantly different effective QCD scales.
Highlights
The gluonic composition of hadrons plays a key role in understanding the confining phase of quantum chromodynamics (QCD), which is still an unresolved issue in modern particle physics
The coupling of the rank-two energy-momentum tensor (EMT), the tensor which couples to gravity [1,2,3], provides fundamental constraints on the quark and gluon generalized parton distribution functions (GPDs) of a hadron [4,5,6]
We note that the overall normalization of the gluon distribution from our calculation seems overestimated in comparison with some recent global analyses, which may arise from neglecting higher Fock states for the gluon Gravitational form factors (GFFs)
Summary
The gluonic composition of hadrons plays a key role in understanding the confining phase of quantum chromodynamics (QCD), which is still an unresolved issue in modern particle physics. We present an extended holographic light-front (LF) QCD framework for studying the gluon GFFs and provide predictions for the intrinsic gluon distributions of hadrons without introducing additional parameters. The effective confining interaction for mesons and baryons is determined by an underlying superconformal algebraic structure [22,23,24], which leads to unexpected connections across the full hadron spectrum [25] It reproduces the structure of hadronic spectra as predicted by dual models, most prominently the Veneziano model [26] with its typical features; linear Regge trajectories with a universal slope and the existence of “daughter trajectories”. The juudgi and judgi Fock states should provide the leading contributions to the intrinsic gluon distributions of, respectively, the proton and pion coupled to a spin-two current with its characteristic Reggeized t-channel particle exchange.
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