First Measurement of Near-Threshold J /ψ Exclusive Photoproduction off the Proton

A. Ali, M. Amaryan, E. G. Anassontzis, A. Austregesilo, M. Baalouch, F. Barbosa, J. Barlow, A. Barnes, E. Barriga, T. D. Beattie, V. V. Berdnikov, T. Black, W. Boeglin, M. Boer, W. J. Briscoe, T. Britton, W. K. Brooks, B. E. Cannon, N. Cao, E. ChudakovS. Cole, O. Cortes, V. Crede, M. M. Dalton, T. Daniels, A. Deur, S. Dobbs, A. Dolgolenko, R. Dotel, M. Dugger, R. Dzhygadlo, H. Egiyan, A. Ernst, P. Eugenio, C. Fanelli, S. Fegan, A. M. Foda, J. Foote, J. Frye, S. Furletov, L. Gan, A. Gasparian, V. Gauzshtein, N. Gevorgyan, C. Gleason, K. Goetzen, A. Goncalves, V. S. Goryachev, L. Guo, H. Hakobyan, A. Hamdi, S. Han, J. Hardin, G. M. Huber, A. Hurley, D. G. Ireland, M. M. Ito, N. S. Jarvis, R. T. Jones, V. Kakoyan, G. Kalicy, M. Kamel, C. Kourkoumelis, S. Kuleshov, I. Kuznetsov, I. Larin, D. Lawrence, D. I. Lersch, H. Li, W. Li, B. Liu, K. Livingston, G. J. Lolos, V. Lyubovitskij, D. Mack, H. Marukyan, V. Matveev, M. McCaughan, M. McCracken, W. McGinley, J. McIntyre, C. A. Meyer, R. Miskimen, R. E. Mitchell, F. Mokaya, F. Nerling, L. Ng, A. I. Ostrovidov, Z. Papandreou, M. Patsyuk, P. Pauli, R. Pedroni, L. Pentchev, K. J. Peters, W. Phelps, E. Pooser, N. Qin, J. Reinhold, B. G. Ritchie, L. Robison

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24 Citations (Scopus)


© 2019 American Physical Society. We report on the measurement of the γp→J/ψp cross section from Eγ=11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67±0.39 GeV-2 at 10.7 GeV average energy. The LHCb pentaquark candidates Pc+ can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(Pc+→J/ψp) and cross sections σ(γp→Pc+)×B(Pc+→J/ψp).
Original languageEnglish
JournalPhysical Review Letters
Publication statusPublished - 13 Aug 2019

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    Ali, A., Amaryan, M., Anassontzis, E. G., Austregesilo, A., Baalouch, M., Barbosa, F., Barlow, J., Barnes, A., Barriga, E., Beattie, T. D., Berdnikov, V. V., Black, T., Boeglin, W., Boer, M., Briscoe, W. J., Britton, T., Brooks, W. K., Cannon, B. E., Cao, N., ... Robison, L. (2019). First Measurement of Near-Threshold J /ψ Exclusive Photoproduction off the Proton. Physical Review Letters.