Double polarization observables in pentaquark photoproduction

Abstract

We investigate the properties of the hidden-charm pentaquark-like resonances first observed by the LHCb Collaboration in 2015, by measuring the polarization transfer K L L between the incident photon and the outgoing proton in the exclusive photoproduction of J / ψ 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 the initial-state helicity correlation A L L , 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 A L L and K L L in J / ψ exclusive photoproduction, in order to determine the pentaquark photocouplings and branching ratios.