Double polarization observables in pentaquark photoproduction

Abstract

We investigate the properties of the hidden charm pentaquark-like resonances first observed by LHCb in 2015, by measuring the polarization transfer $K_{LL}$ 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 $A_{LL}$, 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 $A_{LL}$ and $K_{LL}$ in $J/psi$ exclusive photoproduction, in order to determine the pentaquark photocouplings and branching ratios.