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First measurement of near-threshold J/$\psi $ exclusive photoproduction off the proton
- Source :
- Phys. Rev. Lett. 123, 072001 (2019)
- Publication Year :
- 2019
-
Abstract
- We report on the measurement of the $\gamma p \rightarrow J/\psi p$ cross section from $E_\gamma = 11.8$ 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 $d\sigma /dt$ has an exponential slope of $1.67 \pm 0.39$ 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 $\mathcal{B}(P_c^+ \rightarrow J/\psi p)$ and cross sections $\sigma(\gamma p \to P_c^+)\times\mathcal{B}(P_c^+ \to J/\psi p) $.<br />Comment: 12 pages, 7 figures
- Subjects :
- Nuclear Experiment
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. Lett. 123, 072001 (2019)
- Publication Type :
- Report
- Accession number :
- edsarx.1905.10811
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevLett.123.072001