Nucleon Strong-Interactions Size From Charmonium Photoproduction
Abstract
Protons and neutrons differ dramatically in their electromagnetic sizes, but are bound by the strong (color) force and have nearly identical masses, like two twin states of the same ``nucleon". To reveal the overall spatial extent, it must be examined through the strong interaction rather than electromagnetism. The J/ψ particle, a compact color-charge dipole of a charm quark and antiquark, provides an ideal probe. Recent high-precision measurements of near-threshold J/ψ production at Jefferson Lab offer a more precise glimpse of the proton's gluonic spatial structure. Combining these data with recent quark-sector results, we extract the distribution of the color field underlying mass generation in the nucleon and find it extends beyond both charge and mass distributions, revealing the nucleon's overall strong-interaction spatial extent of 0.94± 0.09 fm.
Related
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- Exclusive dimuon production and coherent charmonium photoproduction at forward rapidity in ultra-peripheral Pb–Pb collisions at √(sNN)=5.36 TeV
- Charmonium-nucleon femtoscopy as a possible probe of the nucleon gravitational form factor
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- Probing the Size of Neutron and Proton Single-Particle Orbitals from Nucleon Knockout Reactions
BibTeX
@misc{ji2026nucleon,
title = {{Nucleon Strong-Interactions Size From Charmonium Photoproduction}},
author = {Xiangdong Ji and Sylvester Joosten and Zein-Eddine Meziani and Dimitra A. Pefkou},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09318},
eprint = {2609.09318},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09318},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Nucleon Strong-Interactions Size From Charmonium Photoproduction
AU - Xiangdong Ji
AU - Sylvester Joosten
AU - Zein-Eddine Meziani
AU - Dimitra A. Pefkou
PY - 2026
DA - 2026/09/10
PB - arXiv
DO - 10.48550/arxiv.2609.09318
UR - https://arxiv.org/abs/2609.09318
AB - Protons and neutrons differ dramatically in their electromagnetic sizes, but are bound by the strong (color) force and have nearly identical masses, like two twin states of the same ``nucleon". To reveal the overall spatial extent, it must be examined through the strong interaction rather than electromagnetism. The J/ψ particle, a compact color-charge dipole of a charm quark and antiquark, provides an ideal probe. Recent high-precision measurements of near-threshold J/ψ production at Jefferson Lab offer a more precise glimpse of the proton's gluonic spatial structure. Combining these data with recent quark-sector results, we extract the distribution of the color field underlying mass generation in the nucleon and find it extends beyond both charge and mass distributions, revealing the nucleon's overall strong-interaction spatial extent of 0.94± 0.09 fm.
ER -