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Measurement of the near-threshold $J / ψ$ photoproduction cross section with the CLAS12 experiment

P. Chatagnon ^5,*, V. Kubarovsky⁴¹, R. Paremuzyan^29,41, S. Stepanyan⁴¹, M. Tenorio³³, R. Tyson⁴⁶, A. G. Acar⁴⁸, P. Achenbach⁶, J. S. Alvarado¹⁶ et al. (CLAS Collaboration)

J. S. Alvarado¹⁶, M. J. Amaryan³³, W. R. Armstrong¹, H. Avakian⁴¹, N. A. Baltzell⁴¹, L. Barion¹⁷, M. Bashkanov⁴⁸, M. Battaglieri¹⁹, F. Benmokhtar⁹, A. Bianconi^23,45, A. S. Biselli¹⁰, S. Boiarinov⁴¹, M. Bondi^20,22, F. Bossù⁵, K.-Th. Brinkmann³⁴, W. J. Briscoe¹⁴, S. Bueltmann³³, V. D. Burkert⁴¹, T. Cao⁴¹, D. S. Carman⁴¹, A. Celentano^13,19, H. Chinchay²⁹, G. Ciullo^11,17, P. L. Cole²⁶, A. D'Angelo^20,36, N. Dashyan⁵², M. Defurne⁵, R. De Vita^19,41, A. Deur⁴¹, S. Diehl^7,34, C. Dilks⁴¹, C. Djalali³², M. Dugger², R. Dupré¹⁶, H. Egiyan⁴¹, M. Ehrhart^1,16,†, A. El Alaoui⁴³, L. El Fassi²⁸, L. Elouadrhiri⁴¹, M. Farooq²⁹, S. Fegan⁴⁸, R. F. Ferguson⁴⁶, I. P. Fernando⁵⁰, E. Ferrand⁵, A. Filippi²¹, C. Fogler³³, K. Gates⁴⁸, G. P. Gilfoyle³⁵, D. I. Glazier⁴⁶, R. W. Gothe³⁹, Y. Gotra⁴¹, B. Gualtieri¹², K. Hafidi¹, H. Hakobyan⁴³, F. Hauenstein^33,41, T. B. Hayward²⁷, D. Heddle^6,41, M. Hoballah¹⁶, D. Holmberg⁵¹, M. Holtrop²⁹, C. E. Hyde³³, Y. Ilieva³⁹, D. G. Ireland⁴⁶, E. L. Isupov³⁸, H. S. Jo²⁵, K. Joo⁷, T. Kageya⁴¹, M. Kerr²⁷, A. Kim⁷, H. T. Klest¹, V. Klimenko¹, I. Korover⁴⁹, A. Kripko³⁴, S. E. Kuhn³³, L. Lanza^20,36, S. Lee⁴⁰, P. Lenisa^11,17, X. Li³⁷, D. Marchand¹⁶, D. Martiryan⁵², V. Mascagna^23,44,45, B. McKinnon⁴⁶, A. Mehta³⁰, R. G. Milner²⁷, T. Mineeva⁴², M. Mirazita¹⁸, V. I. Mokeev⁴¹, E. F. Molina Cardenas⁴², C. Munoz Camacho¹⁶, P. Nadel-Turonski^39,41, K. Neupane⁴¹, D. Nguyen^41,47, S. Niccolai¹⁶, G. Niculescu²⁴, M. Osipenko¹⁹, M. Ouillon²⁸, P. Pandey²⁷, M. Paolone^30,40, L. L. Pappalardo^11,17, E. Pasyuk⁴¹, C. Paudel³⁰, S. J. Paul¹², W. Phelps^6,41, N. Pilleux¹, L. Polizzi¹⁷, J. Poudel⁴¹, J. W. Price³, Y. Prok³³, A. Radic⁴³, J. Richards⁷, M. Ripani¹⁹, J. Ritman¹⁵, P. Rossi^18,41, A. A. Rusova³⁸, C. Salgado^6,31, S. Schadmand¹⁵, A. Schmidt^14,27, M. B. C. Scott¹⁴, Y. G. Sharabian⁴¹, E. V. Shirokov³⁸, S. Shrestha⁴⁰, E. Sidoretti²⁰, N. Sparveris⁴⁰, I. I. Strakovsky¹⁴, S. Strauch³⁹, F. Touchte Codjo¹⁶, M. Ungaro⁴¹, D. W. Upton³³, P. S. H. Vaishnavi¹⁷, S. Vallarino¹⁹, C. Velasquez⁴⁸, L. Venturelli^23,45, H. Voskanyan⁵², A. Vossen^8,41, E. Voutier¹⁶, Y. Wang²⁷, D. P. Watts⁴⁸, U. Weerasinghe²⁸, X. Wei⁴¹, M. H. Wood⁴, L. Xu¹⁶, Z. Xu¹, Z. W. Zhao⁸, V. Ziegler⁴¹, and M. Zurek¹ (CLAS Collaboration)

¹Argonne National Laboratory, Argonne, Illinois 60439, USA
²Arizona State University, Tempe, Arizona 85287, USA
³California State University, Dominguez Hills, Carson, California 90747, USA
⁴Canisius College, Buffalo, New York 14208, USA
⁵IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France
⁶Christopher Newport University, Newport News, Virginia 23606, USA
⁷University of Connecticut, Storrs, Connecticut 06269, USA
⁸Duke University, Durham, North Carolina 27708, USA
⁹Duquesne University, Pittsburgh, Pennsylvania 15282, USA
¹⁰Fairfield University, Fairfield, Connecticut 06824, USA
¹¹Università di Ferrara, 44121 Ferrara, Italy
¹²Florida International University, Miami, Florida 33199, USA
¹³Dipartimento di Fisica dell'Università, 16146 Genova, Italy
¹⁴The George Washington University, Washington, D.C. 20052, USA
¹⁵GSI Helmholtzzentrum fur Schwerionenforschung GmbH, D-64291 Darmstadt, Germany
¹⁶Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
¹⁷INFN, Sezione di Ferrara, 44100 Ferrara, Italy
¹⁸INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy
¹⁹INFN, Sezione di Genova, 16146 Genova, Italy
²⁰INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy
²¹INFN, Sezione di Torino, 10125 Torino, Italy
²²INFN, Sezione di Catania, 95123 Catania, Italy
²³INFN, Sezione di Pavia, 27100 Pavia, Italy
²⁴James Madison University, Harrisonburg, Virginia 22807, USA
²⁵Kyungpook National University, Daegu 41566, Republic of Korea
²⁶Lamar University, Beaumont, Texas 77710, USA
²⁷Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
²⁸Mississippi State University, Mississippi State, Mississippi 39762, USA
²⁹University of New Hampshire, Durham, New Hampshire 03824, USA
³⁰New Mexico State University, Las Cruces, New Mexico 88003, USA
³¹Norfolk State University, Norfolk, Virginia 23504, USA
³²Ohio University, Athens, Ohio 45701, USA
³³Old Dominion University, Norfolk, Virginia 23529, USA
³⁴II Physikalisches Institut der Universitaet Giessen, 35392 Giessen, Germany
³⁵University of Richmond, Richmond, Virginia 23173, USA
³⁶Università di Roma Tor Vergata, 00133 Rome, Italy
³⁷Shandong University, Qingdao, Shandong 266237, China
³⁸Skobeltsyn Institute of Nuclear Physics, Lomonosov Moscow State University, 119234 Moscow, Russia
³⁹University of South Carolina, Columbia, South Carolina 29208, USA
⁴⁰Temple University, Philadelphia, Pennsylvania 19122, USA
⁴¹Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
⁴²Universidad de La Serena, Avda Juan Cisternos 1200, La Serena, Chile
⁴³Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile
⁴⁴Università degli Studi dell'Insubria, 22100 Como, Italy
⁴⁵Università degli Studi di Brescia, 25123 Brescia, Italy
⁴⁶University of Glasgow, Glasgow G12 8QQ, United Kingdom
⁴⁷University of Tennessee, Knoxville, Tennessee 37996, USA
⁴⁸University of York, York YO10 5DD, United Kingdom
⁴⁹University of Tel Aviv, Tel Aviv 6997801, Israel
⁵⁰University of Virginia, Charlottesville, Virginia 22901, USA
⁵¹College of William and Mary, Williamsburg, Virginia 23187, USA
⁵²Yerevan Physics Institute, 375036 Yerevan, Armenia

^*Contact author: pierre.chatagnon@cea.fr
^†Present address: DOTA, ONERA, Université Paris-Saclay, 91120, Palaiseau, France.

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Phys. Rev. C 113, 065203 – Published 9 June, 2026

DOI: https://doi.org/10.1103/lqv1-kf2n

Abstract

We present measurements of the total and differential cross sections for near-threshold $J / ψ$ photoproduction obtained with the CLAS12 detector at the Thomas Jefferson National Accelerator Facility. The results are based on data collected during the fall 2018 and spring 2019 running periods, using electron beams with energies of 10.6 and 10.2 GeV, respectively, scattered off a liquid-hydrogen target. Near-threshold $J / ψ$ photoproduction offers a unique sensitivity to the strong interaction in the nonperturbative regime of quantum chromodynamics (QCD). The energy dependence of the cross section constrains the underlying $J / ψ$ production mechanisms, including multigluon exchange and potential baryonic excitations. Additionally, the $t$ dependence of the differential cross section can be related to the transverse spatial distribution of gluons in the proton, providing critical input for theoretical descriptions of the gluonic structure of the proton. An interpretation of the results in terms of the gluon content of the proton is presented, providing new experimental constraints on QCD-inspired models of the proton structure and the role of gluonic degrees of freedom in hadronic mass generation.

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References (90)

B. Gittelman et al., Photoproduction of the $ψ (3100)$ meson at 11 GeV, Phys. Rev. Lett. 35, 1616 (1975).
U. Camerini et al., Photoproduction of the $ψ$ particles, Phys. Rev. Lett. 35, 483 (1975).
S. Chekanov et al. (ZEUS Collaboration), Exclusive photoproduction of $J / ψ$ mesons at HERA, Eur. Phys. J. C 24, 345 (2002).
A. Aktas et al. (H1 Collaboration), Elastic $J / ψ$ production at HERA, Eur. Phys. J. C 46, 585 (2006).
C. Alexa et al. (H1 Collaboration), Elastic and proton-dissociative photoproduction of $J / ψ$ mesons at HERA, Eur. Phys. J. C 73, 2466 (2013).
B. B. Abelev et al. (ALICE Collaboration), Exclusive $J / ψ$ photoproduction off protons in ultraperipheral $p − Pb$ collisions at $\sqrt{s_{NN}} = 5.02 TeV$ , Phys. Rev. Lett. 113, 232504 (2014).
S. Acharya et al. (ALICE Collaboration), Energy dependence of exclusive $J / ψ$ photoproduction off protons in ultra-peripheral p–Pb collisions at $\sqrt{s_{NN}} = 5.02 TeV$ , Eur. Phys. J. C 79, 402 (2019).
R. Aaij et al. (LHCb Collaboration), Central exclusive production of $J / ψ$ and $ψ (2 S)$ mesons in pp collisions at $\sqrt{s} = 13 TeV$ , J. High Energy Phys. 10 (2018) 167.
P. A. Adderley et al., The continuous electron beam accelerator facility at 12 GeV, Phys. Rev. Accel. Beams 27, 084802 (2024).
A. Ali et al. (GlueX Collaboration), First measurement of near-threshold $J / ψ$ exclusive photoproduction off the proton, Phys. Rev. Lett. 123, 072001 (2019).
S. Adhikari et al. (GlueX Collaboration), Measurement of the $J / ψ$ photoproduction cross section over the full near-threshold kinematic region, Phys. Rev. C 108, 025201 (2023).
I. Strakovsky et al., $J / ψ p$ scattering length from GlueX threshold measurements, Phys. Rev. C 101, 042201 (2020).
B. Duran et al., Determining the gluonic gravitational form factors of the proton, Nature (London) 615, 813 (2023).
H. Pagels, Energy-momentum structure form factors of particles, Phys. Rev. 144, 1250 (1966).
X.-D. Ji, Gauge-invariant decomposition of nucleon spin, Phys. Rev. Lett. 78, 610 (1997).
V. D. Burkert et al., The pressure distribution inside the proton, Nature (London) 557, 396 (2018).
M. V. Polyakov et al., Forces inside hadrons: Pressure, surface tension, mechanical radius, and all that, Int. J. Mod. Phys. A 33, 1830025 (2018).
C. Lorcé et al., Revisiting the mechanical properties of the nucleon, Eur. Phys. J. C 79, 89 (2019).
V. D. Burkert et al., Colloquium: Gravitational form factors of the proton, Rev. Mod. Phys. 95, 041002 (2023).
S. Joosten et al., Near-threshold $J / ψ \to μ^{+} μ^{-}$ photoproduction and the gluonic gravitational form factors of the proton, arXiv:2602.14416.
Y. Hatta et al., Near threshold $J / ψ$ and $Υ$ photoproduction at JLab and RHIC, Phys. Rev. D 100, 014032 (2019).
Y. Guo et al., QCD analysis of near-threshold photon-proton production of heavy quarkonium, Phys. Rev. D 103, 096010 (2021).
D. E. Kharzeev, Mass radius of the proton, Phys. Rev. D 104, 054015 (2021).
K. A. Mamo et al., $J / ψ$ near threshold in holographic QCD: $A$ and $D$ gravitational form factors, Phys. Rev. D 106, 086004 (2022).
Y. Guo et al., Updated analysis of near-threshold heavy quarkonium production for probe of proton's gluonic gravitational form factors, Phys. Rev. D 108, 034003 (2023).
P. E. Shanahan et al., Gluon gravitational form factors of the nucleon and the pion from lattice QCD, Phys. Rev. D 99, 014511 (2019).
D. A. Pefkou et al., Gluon gravitational structure of hadrons of different spin, Phys. Rev. D 105, 054509 (2022).
D. C. Hackett et al., Gravitational form factors of the proton from lattice QCD, Phys. Rev. Lett. 132, 251904 (2024).
K. A. Mamo et al., Diffractive photoproduction of $J / ψ$ and $Υ$ using holographic QCD: Gravitational form factors and GPD of gluons in the proton, Phys. Rev. D 101, 086003 (2020).
K. A. Mamo et al., Nucleon mass radii and distribution: Holographic QCD, lattice QCD, and GlueX data, Phys. Rev. D 103, 094010 (2021).
K. A. Mamo et al., Electroproduction of heavy vector mesons using holographic QCD: From near threshold to high energy regimes, Phys. Rev. D 104, 066023 (2021).
A. V. Radyushkin, Asymmetric gluon distributions and hard diffractive electroproduction, Phys. Lett. B 385, 333 (1996).
J. C. Collins et al., Factorization for hard exclusive electroproduction of mesons in QCD, Phys. Rev. D 56, 2982 (1997).
P. Hoodbhoy, Wave function corrections and off-forward gluon distributions in diffractive $J / ψ$ electroproduction, Phys. Rev. D 56, 388 (1997).
L. Frankfurt et al., Nondiagonal parton distributions in the leading logarithmic approximation, Phys. Lett. B 418, 345 (1998).
Y. Guo et al., Bayesian inferring nucleon gravitational form factors via near-threshold $J / ψ$ photoproduction, Phys. Rev. Lett. 135, 111902 (2025).
L. Tang et al., Exclusive photoproduction of light and heavy vector mesons: Thresholds to very high energies, Eur. Phys. J. C 86, 284 (2026).
M.-L. Du et al., Deciphering the mechanism of near-threshold $J / ψ$ photoproduction, Eur. Phys. J. C 80, 1053 (2020).
D. Winney et al. (JPAC Collaboration), Dynamics in near-threshold $J / ψ$ photoproduction, Phys. Rev. D 108, 054018 (2023).
V. Kubarovsky et al., Formation of hidden-charm pentaquarks in photon-nucleon collisions, Phys. Rev. D 92, 031502 (2015).
F.-K. Guo et al., How to reveal the exotic nature of the $P_{c} (4450)$ , Phys. Rev. D 92, 071502 (2015).
M. I. Eides et al., Narrow nucleon- $ψ (2 S)$ bound state and LHCb pentaquarks, Phys. Rev. D 93, 054039 (2016).
A. N. Hiller Blin et al., Studying the $P_{c} (4450)$ resonance in $J / ψ$ photoproduction off protons, Phys. Rev. D 94, 034002 (2016).
I. Strakovsky et al., Plausibility of the LHCb $P_{c} {(4312)}^{+}$ in the GlueX $γ p \to J / ψ p$ total cross sections, Phys. Rev. C 108, 015202 (2023).
CLAS Physics Database, http://clasweb.jlab.org/physicsdb.
V. D. Burkert et al. (CLAS Collaboration), The CLAS12 spectrometer at Jefferson Laboratory, Nucl. Instrum. Methods A 959, 163419 (2020).
R. Fair et al., The CLAS12 superconducting magnets, Nucl. Instrum. Methods A 962, 163578 (2020).
M. D. Mestayer et al., The CLAS12 drift chamber system, Nucl. Instrum. Methods A 959, 163518 (2020).
Y. G. Sharabian et al., The CLAS12 high threshold Cherenkov counter, Nucl. Instrum. Methods A 968, 163824 (2020).
G. Asryan et al., The CLAS12 forward electromagnetic calorimeter, Nucl. Instrum. Methods A 959, 163425 (2020).
D. S. Carman et al., The CLAS12 forward time-of-flight system, Nucl. Instrum. Methods A 960, 163629 (2020).
B. Raydo et al., The CLAS12 trigger system, Nucl. Instrum. Methods A 960, 163529 (2020).
S. Boyarinov et al., The CLAS12 data acquisition system, Nucl. Instrum. Methods A 966, 163698 (2020).
V. Ziegler et al., The CLAS12 software framework and event reconstruction, Nucl. Instrum. Methods A 959, 163472 (2020).
P. Chatagnon et al. (CLAS Collaboration), First measurement of timelike Compton scattering, Phys. Rev. Lett. 127, 262501 (2021).
A. Hocker et al., TMVA—Toolkit for Multivariate Data Analysis, arXiv:physics/0703039.
H. Voss et al., TMVA, the Toolkit for Multivariate Data Analysis with ROOT, PoS ACAT, 040 (2007).
M. Ungaro et al., The CLAS12 Geant4 simulation, Nucl. Instrum. Methods A 959, 163422 (2020).
S. Agostinelli et al. (GEANT4 Collaboration), Geant4—A simulation toolkit, Nucl. Instrum. Methods A 506, 250 (2003).
S. Stepanyan et al., CLAS12-Note 2020-005, Tech. Rep. (2020).
T. Abe, GRAPE-Dilepton (version 1.1), Comput. Phys. Commun. 136, 126 (2001).
TCSGen (TCS Event Generator), https://github.com/JeffersonLab/TCSGen (2025).
JPsiGen ( $J / ψ$ Photoproduction Event Generator), https://github.com/JeffersonLab/JPsiGen (2025).
M. Heller et al., Soft-photon corrections to the Bethe-Heitler process in the $γ p \to l^{+} l^{-} p$ reaction, Phys. Rev. D 97, 076012 (2018).
F. Ehlotzky et al., Radiative corrections to the leptonic-decay modes of the neutral vector mesons $ρ^{0}, ω, ϕ$ , Nuovo Cim. A 55, 181 (1968).
A. Rogozhnikov, Reweighting with boosted decision trees, J. Phys.: Conf. Ser. 762, 012036 (2016).
S. Navas et al. (Particle Data Group Collaboration), Review of particle physics, Phys. Rev. D 110, 030001 (2024).
S. Frixione et al., Improving the Weizsäcker-Williams approximation in electron-proton collisions, Phys. Lett. B 319, 339 (1993).
H. D. Schulz et al., Experimental confirmation of radiative corrections to bremsstrahlung and pair production at high energies, Phys. Rev. 167, 1280 (1968).
K. Mork et al., Radiative corrections. I. High-energy bremsstrahlung and pair production, Phys. Rev. 140, B1661 (1965).
K. Gottfried et al., On the connection between production mechanism and decay of resonances at high energies, Nuovo Cim. 33, 309 (1964).
K. Schilling et al., On the analysis of vector-meson production by polarized photons, Nucl. Phys. B 15, 397 (1970).
A. I. Titov et al., Structure of the $φ$ photoproduction amplitude at a few GeV, Phys. Rev. C 60, 035205 (1999).
P. Faccioli et al., Towards the experimental clarification of quarkonium polarization, Eur. Phys. J. C 69, 657 (2010).
T. Skwarnicki, Ph.D. thesis, Institute for Nuclear Physics; DESY Report No. DESY-F31-86-02, 1986.
V. Mathieu et al. (JPAC Collaboration), Vector meson photoproduction with a linearly polarized beam, Phys. Rev. D 97, 094003 (2018).
E. Barberio et al., PHOTOS - a universal Monte Carlo for QED radiative corrections: version 2.0, Comput. Phys. Commun. 79, 291 (1994).
V. Klimenko et al. (CLAS Collaboration), Inclusive electron scattering in the resonance region off a hydrogen target with CLAS12, Phys. Rev. C 112, 025201 (2025).
D. Kharzeev et al., $J / ψ$ -photoproduction and the gluon structure of the nucleon, Nucl. Phys. A 661, 568 (1999).
L. Frankfurt et al., Two-gluon form factor of the nucleon and $J / ψ$ photoproduction, Phys. Rev. D 66, 031502 (2002).
E. Tiesinga et al., CODATA recommended values of the fundamental physical constants: 2018, Rev. Mod. Phys. 93, 025010 (2021).
T.-J. Hou et al., New CTEQ global analysis of quantum chromodynamics with high-precision data from the LHC, Phys. Rev. D 103, 014013 (2021).
K. Tanaka, Three-loop formula for quark and gluon contributions to the QCD trace anomaly, J. High Energ. Phys. 01 (2019) 120.
K. Tanaka, Twist-four gravitational form factor at NNLO QCD from trace anomaly constraints, J. High Energ. Phys. 03 (2023) 013.
Z. E. Meziani, Gluonic gravitational form factors of the proton, PoS SPIN2023, 168 (2024).
X. Ji, Proton mass decomposition: Naturalness and interpretations, Front. Phys. 16, 64601 (2021).
K. Hafidi et al., Proposal PR12-12-006 to JLab-PAC39, https://www.jlab.org/exp_prog/proposals/12/PR12-12-006.pdf (2012).
J. Arrington et al. (SoLID Collaboration), The solenoidal large intensity device (SoLID) for JLab 12 GeV, J. Phys. G 50, 110501 (2023).
J. S. Alvarado et al., Electro- and photoproduction of muon pairs with $μ CLAS 12$ : Double deeply virtual Compton scattering, timelike Compton scattering, and $J / ψ$ production, arXiv:2605.11690.
O. Gryniuk et al., $Υ$ photoproduction on the proton at the electron-ion collider, Phys. Rev. D 102, 014016 (2020).

Phys. Rev. C 113, 065203– Published 9 June, 2026

Vol. 113, Iss. 6 — June 2026

Received 26 February 2026
Accepted 20 May 2026

DOI: https://doi.org/10.1103/lqv1-kf2n

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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Measurement of the near-threshold $J / ψ$ photoproduction cross section with the CLAS12 experiment

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Measurement of the near-threshold J/ψ photoproduction cross section with the CLAS12 experiment

Abstract

Physics Subject Headings (PhySH)

Article Text

References (90)

Measurement of the near-threshold $J / ψ$ photoproduction cross section with the CLAS12 experiment