Threshold $J/\psi$ Photoproduction as a Probe of Nuclear Gluon Structure
Abstract
The nuclear EMC effect is the observation that quark distributions in bound nucleons experience significant modification at large relative to free nucleons. Despite decades of measurements verifying the presence of this effect in quarks across a wide range of nuclei, behavior of large- gluons in nuclei remains almost completely unknown. As the nuclear physics community seeks out new observables to try to elucidate the mechanisms behind the EMC effect, it becomes striking that we remain ignorant regarding the impact of nuclear effects on gluonic behavior. Recent photonuclear data using the Hall D photon beam have enabled the first measurement of photoproduction from nuclei near and below the energy threshold, with the results highlighted in Physical Review Letters as an Editors' Suggestion. These data have placed the first, and currently only, constraints on the behavior of large- gluons within bound nucleons. However, compared to the quantity of data which currently informs our knowledge of the quark-sector EMC effect, these data are extremely limited, and remain unable to conclusively observe or exclude large modification of gluon distributions. A high-luminosity photonuclear experiment will enable a precision measurement of incoherent photoproduction at and below the threshold region. This data will provide the first stringent constraints on nuclear modification of gluon structure or other exotic effects which could impact the production of from nuclei. We request 85 PAC days at Hall D using the GlueX detector with a 12 GeV electron beam energy and a coherent photon peak energy of GeV, split into 80 days using a He target and 5 calibration days using a H target.
Cite
@article{arxiv.2510.22076,
title = {Threshold $J/\psi$ Photoproduction as a Probe of Nuclear Gluon Structure},
author = {J. R. Pybus and D. Dutta and H. Gao and O. Hen and I. Korover and T. Kolar and A. Schmidt and A. Somov and H. Szumila-Vance and D. Androić and C. Ayerbe Gayoso and X. Bai and V. V. Berdnikov and S. Bhattarai and Z. Chen and E. O. Cohen and O. Cortes Becerra and K. Dehmelt and A. Deur and B. R. Devkota and L. Ehinger and L. El Fassi and S. Fang and P. Gautam and J. -O. Hansen and M. Hattawy and F. Hauenstein and D. Higinbotham and A. Hobart and Z. Huang and R. Jones and M. Junaid and V. Kakoyan and N. Kalantarians and T. Kutz and I. Larin and Y. Li and J. Lichtenstadt and C. -W. Lin and Y. Liu and B. Liu and H. Lu and V. Lyubovitskij and B. -Q. Ma and H. Marukyan and M. Maynes and M. D. McCaughan and B. McKinnon and C. Morean and D. Nguyen and M. Ouillon and B. Pandey and A. Panta and M. Paolone and I. Parshkin and S. Paul and J. Phelan and E. Piasetzky and H. Qi and S. Regmi and D. Romanov and A. Shahinyan and X. Shen and D. Smith and S. Somov and N. Sparveris and I. Strakovsky and A. Tadepalli and B. Tamang and R. Tyson and H. Voskanyan and R. Wagner and U. Weerasinghe and L. B. Weinstein and N. Wright and T. Xiao and Z. Ye and B. Yu and Y. Yu and Y. Zhang and Z. Zhang and Z. Zhang and Z. Zhao and H. Zhao and J. Zhou and X. Zhou and B. Zihlmann},
journal= {arXiv preprint arXiv:2510.22076},
year = {2025}
}
Comments
26 pages, 12 figures, porposal for Jefferson Lab Experiment E12-25-002, submitted to Jefferson Lab PAC 53 (2025)