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

GlueX Collaboration

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122 Scopus citations


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 (US)
Article number072001
JournalPhysical Review Letters
Issue number7
StatePublished - Aug 13 2019

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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