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JLab and J-PARC measurements for $J / ψ$ production at threshold

Igor I. Strakovsky ^* and William J. Briscoe ^†

Jung Keun Ahn ^‡

Misha G. Ryskin ^§

Axel Schmidt ^∥

Institute for Nuclear Studies, Department of Physics, The George Washington University, Washington, District of Columbia 20052, USA

Department of Physics, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea

NRC “Kurchatov Institute,” Petersburg Nuclear Physics Institute, Gatchina, 188300, Russia

Institute for Nuclear Studies, Department of Physics, The George Washington University, Washington, District of Columbia 20052, USA

^*Contact author: igor@gwu.edu
^†Contact author: briscoe@gwu.edu
^‡Contact author: ahnjk@korea.ac.kr
^§Contact author: ryskinmg@airnet.ru
^∥Contact author: axelschmidt@gwu.edu

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Phys. Rev. D 113, 114023 – Published 12 June, 2026

DOI: https://doi.org/10.1103/3g18-qv5t

Abstract

New threshold measurements for $γ p \to p J / ψ \to p (μ^{+} μ^{-})$ by 007 and $γ^{*} p \to p J / ψ \to p (e^{+} e^{-})$ by CLAS12 allow us to extend the previous phenomenological determination of the $J / ψ$ -proton scattering length, $α_{J / ψ p}$ , using GlueX threshold data for $γ p \to p J / ψ \to p (e^{+} e^{-})$ . The agreement between all three $J / ψ$ datasets shows no indication of systematic differences between methodologies. Furthermore, perturbative QCD predictions support the phenomenological determination of heavy vector meson-nucleon scattering lengths. The role of the nucleon form factor, $F_{N}$ , is discussed, and a possible correction to the phenomenological scattering length for heavy vector meson photoproduction is calculated using the pole form of $F_{N}$ . Upcoming J-PARC threshold measurements of the reaction $π^{-} p \to n J / ψ \to n (l^{+} l^{-})$ will help to evaluate the possible role of heavy pentaquark, $P_{c}$ , states in low-energy $J / ψ$ production and the effects caused by the nucleon form factors.

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Phys. Rev. D 113, 114023– Published 12 June, 2026

Vol. 113, Iss. 11 — 1 June 2026

Received 12 March 2026
Accepted 19 May 2026

DOI: https://doi.org/10.1103/3g18-qv5t

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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JLab and J-PARC measurements for $J / ψ$ production at threshold

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JLab and J-PARC measurements for J/ψ production at threshold

Abstract

Physics Subject Headings (PhySH)

Article Text

References (52)

JLab and J-PARC measurements for $J / ψ$ production at threshold