Exploring Nucleon Structure and the Proton Mass Problem through Holographic QCD

Abstract

Understanding the internal structure of the proton-including the distributions of quarks and gluons and their contributions to proton properties such as mass-remains a central challenge in quantum chromodynamics (QCD). While quark generalized parton distributions (GPDs) have been studied extensively, a unified approach that simultaneously extracts quark parton distribution functions (PDFs), gravitational form factors (GFFs), and gluon GPDs from experimental constraints is still lacking. Moreover, the role of gluons in proton mass generation, particularly through the trace anomaly mechanism, requires deeper theoretical and phenomenological exploration. In this study, we begin by extracting quark GPDs in protons using a parameterization method based on the electromagnetic form factors provided by Light-Front Holographic QCD (LFHQCD), from which we derive both quark PDFs and their GFFs. We then extend this approach to model gluon GPDs. Our calculations show consistency with experimental data and lattice QCD results and successfully reproduce soft Pomeron behavior. Furthermore, we investigate near-threshold $J/\psi$ production using gauge/string duality to quantify the contribution of the trace anomaly to the proton mass. Our results demonstrate that the parameterization method provides a consistent framework for describing both quark and gluon structure, bridging GPDs, PDFs, and GFFs. The analysis of $J/\psi$ production confirms that the trace anomaly contributes significantly ($\sim 24\%$) to the proton mass, with the calculated cross-section dependence on momentum transfer $t$ in agreement with experimental observations. This work advances the understanding of proton structure by integrating quark and gluon degrees of freedom and elucidating the origin of proton mass within QCD.

12 pages, 7 figures

References in corpus (42)

• Hard Exclusive Reactions and the Structure of Hadrons
• Light-Front Holographic QCD and Emerging Confinement
• The Pomeron and Gauge/String Duality
• High-precision determination of the electric and magnetic form factors of the proton
• Meson Spectroscopy in AdS/CFT with Flavour
• Exclusive photoproduction of J/psi mesons at HERA
• The electric and magnetic form factors of the proton
• Parton distributions and lattice QCD calculations: a community white paper
• Revisiting the mechanical properties of the nucleon
• Generalized Parton Distributions in the valence region from Deeply Virtual Compton Scattering
• Proton and neutron electromagnetic form factors and uncertainties
• Universality of Generalized Parton Distributions in Light-Front Holographic QCD
• Glueball Regge trajectories and the Pomeron -- a lattice study --
• On the hadron mass decomposition
• Generalized parton distributions in AdS/QCD
• Diffractive photoproduction of $J/\psi$ and ${\rm Y}$ using holographic QCD: gravitational form factors and GPD of gluons in the proton
• Introduction to GPDs and TMDs
• Holographic $J/\psi$ production near threshold and the proton mass problem
• Photoproduction of charm near threshold
• Two-gluon form factor of the nucleon and $J/\psi$ photoproduction
• Precision Nucleon Charges and Form Factors Using 2+1-flavor Lattice QCD
• Quark and gluon contributions to the QCD trace anomaly
• Perspective on the origin of hadron masses
• Gravitational form factors of the proton from lattice QCD
• A Model for Soft High-Energy Scattering: Tensor Pomeron and Vector Odderon
• Analysis of nucleon electromagnetic form factors from light-front holographic QCD : The spacelike region
• Accessing the real part of the forward $J/\psi$-p scattering amplitude from $J/\psi$ photo-production on protons around threshold
• The Origin of Proton Mass from J/$\mathrm{\Psi }$ Photo-production Data
• Perturbative Calculations of Gravitational Form Factors at Large Momentum Transfer
• Deeply Virtual Compton Scattering from Gauge/Gravity Duality
• Three-loop formula for quark and gluon contributions to the QCD trace anomaly
• The Tensor Pomeron and Low-x Deep Inelastic Scattering
• Form Factors and Two-Photon Exchange in High-Energy Elastic Electron-Proton Scattering
• Two-gluon and trigluon glueballs from dynamical holography QCD
• Precision calculation of the electromagnetic radii of the proton and neutron from lattice QCD
• Regge theory in a Holographic dual of QCD in the Veneziano Limit
• Soft photon anomaly and gauge/string duality
• Electroproduction of heavy vector mesons using holographic QCD: from near threshold to high energy regimes
• Two- and three-gluon glueballs of $C=+$
• Scaling of PDFs, TMDs, and GPDs in soft-wall AdS/QCD
• Analysis of the contribution of the quantum anomaly energy to the proton mass
• Proton mass decomposition