Gottfried-Jackson polarization filters for holographic dilaton and transverse-traceless gluon responses in near-threshold $J/ψ$ photoproduction

Abstract

Within the Hatta-Yang holographic graviton-dilaton amplitude for near-threshold $J/ψ$ photoproduction, we identify exact dilaton-null spin-projection channels in the Gottfried-Jackson basis. The $m=0$ and $m=-λ_γ$ amplitudes receive no dilaton contribution; for photon polarization normal to the reaction plane the $m=0$ channel further isolates $A_g(t)+B_g(t)$ and requires nucleon spin transfer. Standard beam-polarization spin-density-matrix elements then furnish TT-only controls and a bilinear containing linear dilaton-TT interference. A comparison with modern GlueX and CLAS12 cross sections shows that the original fixed-shape holographic amplitude cannot describe the full near-threshold data with one overall normalization, making the polarization filters tests of the production tensor rather than predictions of a globally validated reaction model.