  We investigate the properties of the hidden charm pentaquark-like resonances
first observed by LHCb in 2015, by measuring the polarization transfer KLL
between the incident photon and the outgoing proton in the exclusive
photoproduction of J/psi near threshold. We present a first estimate of the
sensitivity of this observable to the pentaquark photocouplings and hadronic
branching ratios, and extend our predictions to the case of initial state
helicity correlation ALL, using a polarized target. These results serve as a
benchmark for the SBS experiment at Jefferson Lab, which proposes to measure
for the first time the helicity correlations ALL and KLL in J/psi exclusive
photoproduction, in order to determine the pentaquark photocouplings and
branching ratios.
