First measurement of near-threshold J/ψ exclusive photoproduction off the proton
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Publication Information
- Submitted to Physical Review Letters
- arXiv:1905.10811 [nucl-ex] (2017).
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 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 (P+c→J/ψp).
Figures and captions
| Caption | Figures |
|---|---|
| (a) Photon beam intensity versus energy as measured by the pair spectrometer (not corrected for instrumental acceptance). (b) Photon beam polarization as a function of beam energy, as measured by the triplet polarimeter, with data points offset horizontally by ±0.015 GeV for clarity. |
