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

2019/05/31 by The GlueX Collaboration, M. J. Amaryan, A. Ali +152 · 207 citations
Physics and Astronomy · #Computer science #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Physics #Quantum Chromodynamics and Particle Interactions #nucl-ex

paper · pdf · doi:10.1103/physrevlett.123.072001

published in Physical Review Letters 123(7), 072001 (American Physical Society) · 12 pages, 7 figures

openalex publication_date 2019/08/13 · openalex created_date 2019/08/22 · arxiv created 2019/09/10 · arxiv updated 2019/09/12 · openalex updated_date 2026/08/05

Abstract

We report on the measurement of the γp→J/ψp cross section from E_γ=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 P_c⁺ 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(P_c⁺→J/ψp) and cross sections σ(γp→P_c⁺)×B(P_c⁺→J/ψp).

Citations

• Observation of J/ψp resonances consistent with pentaquark states in Λ_b⁰→ J/ψK^-p decays
• Soft-photon corrections to the Bethe-Heitler process in the γp→l+l−p reaction
• Review of Particle Physics