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Autori principali: Pybus, J. R., Ehinger, L., Kolar, T., Devkota, B., Sharp, P., Yu, B., Dalton, M. M., Dutta, D., Gao, H., Hen, O., Piasetzky, E., Santiesteban, S. N., Schmidt, A., Somov, A., Szumila-Vance, H., Adhikari, S., Asaturyan, A., Austregesilo, A., Gayoso, C. Ayerbe, Barlow, J., Berdnikov, V. V., Bhatt, H. D., Bhetuwal, Deepak, Black, T., Briscoe, W. J., Chung, G., Cole, P. L., Deur, A., Dotel, R., Egiyan, H., Eugenio, P., Fanelli, C., Gan, L., Gasparian, A., Guo, J., Hernandez, K., Higinbotham, D. W., Hurck, P., Jaegle, I., Jones, R. T., Kakoyan, V., Karki, A., Li, H., Li, W. B., Linera, G. R., Lyubovitskij, V., Marukyan, H., McCaughan, M. D., McCracken, M., Mizutani, K., Nguyen, D., Oresic, S., Ostrovidov, A. I., Papandreou, Z., Paudel, C., Peters, K., Ritman, J., Schick, A., Schwiening, J., Smith, A., Somov, S., Strakovsky, I., Suresh, K., Tarasov, V. V., Taylor, S., Xiao, T., Zhang, Z., Zhou, X.
Natura: Preprint
Pubblicazione: 2024
Soggetti:
Nuclear Experiment
Accesso online:https://arxiv.org/abs/2409.18463
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Sommario:
  • We report on the first measurement of $J/ψ$ photoproduction from nuclei in the photon energy range of $7$ to $10.8$ GeV, extending above and below the photoproduction threshold in the free proton of $\sim8.2$ GeV. The experiment used a tagged photon beam incident on deuterium, helium, and carbon, and the GlueX detector at Jefferson Lab to measure the semi-inclusive $A(γ,e^+e^-p)$ reaction with a dilepton invariant mass $M(e^+e^-)\sim m_{J/ψ}=3.1$ GeV. The incoherent $J/ψ$ photoproduction cross sections in the measured nuclei are extracted as a function of the incident photon energy, momentum transfer, and proton reconstructed missing light-cone momentum fraction. Comparisons with theoretical predictions assuming a dipole form factor allow extracting a gluonic radius for bound protons of $\sqrt{\langle r^2\rangle}=0.85\pm0.14$ fm. The data also suggest an excess of the measured cross section for sub-threshold production and for interactions with high missing light-cone momentum fraction protons. The measured enhancement can be explained by modified gluon structure for high-virtuality bound-protons.

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