The role of hidden-charm pentaquark resonance Pc+(4450) in J /ψ photoproduction on nuclei near threshold

We study the J/psi photoproduction from nuclei at near-threshold incident photon energies of 5-11 GeV within the nuclear spectral function approach by considering incoherent direct (gamma N -> J/psi N) and two-step (gamma p -> P-c(+)(4450), P-c(+) (4450) -> J/psi p) photon-nucleon charmonium creation processes. We calculate the absolute and relative excitation functions within the different scenarios for in-medium modification of the directly photoproduced J/psi mesons. We show that the overall subthreshold J/psi production in gamma A reactions reveals some sensitivity to adopted in-medium modification scenarios for J/psi mesons only if branching ratio Br[P-c(+) (4450) -> J/psi p]similar to 1% and less. Our studies also demonstrate that the presence of the p(c)(+)(4450) resonance in J/psi photoproduction produces above threshold additional enhancements in the behavior of the total J/psi creation cross section on nuclei, which could be also studied in the future JLab experiments at the upgraded up to 12 GeV CEBAF facility to provide further evidence for its existence. (C) 2018 Elsevier B.V. All rights reserved.