Document Type

Article

Publication Date

2019

DOI

10.1103/PhysRevLett.123.072001

Publication Title

Physical Review Letters

Volume

123

Issue

7

Pages

072001 (1-6)

Abstract

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 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 β(P+c → J/ψp) and cross sections σ(γp → P+c ) x β(P+c → J/ψp).

Comments

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Original Publication Citation

Ali, A., Amaryan, M., Anassontzis, E. G., Austregesilo, A., Baalouch, M., Barbos, F., . . . Zihlmann, B. (2019). First measurement of near-threshold J/ᴪ exclusive photoproduction off the proton. Physical Review Letters, 123(7), 072001. doi:10.1103/PhysRevLett.123.072001

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