1.
Phys Rev Lett
; 123(7): 072001, 2019 Aug 16.
Article
in English
| MEDLINE
| ID: mdl-31491124
ABSTRACT
We report on the measurement of the γpâJ/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}^{+}âJ/ψp) and cross sections σ(γpâP_{c}^{+})×B(P_{c}^{+}âJ/ψp).