Probing the hidden-bottom pentaquark resonances in photonuclear bottomonium production near threshold: Differential observables

Abstract

We study the near-threshold ϒ(1S) meson photoproduction from protons and nuclei by considering incoherent direct non-resonant (γp→ϒ(1S)p, γn→ϒ(1S)n) and two-step resonant (γp→Pbi+→ϒ(1S)p, γn→Pbi0→ϒ(1S)n, i=1, 2, 3; Pb1+,0=Pb+,0(11080), Pb2+,0=Pb+,0(11125), Pb3+,0=Pb+,0(11130)) bottomonium production processes with the main goal of clarifying the possibility to observe the non-strange hidden-bottom pentaquark states Pbi+,0 in this production via differential observables. We calculate the absolute excitation functions, energy and momentum distributions for the non-resonant, resonant and for the combined (non-resonant plus resonant) production of ϒ(1S) mesons on protons, on carbon and tungsten target nuclei at near-threshold incident photon beam energies by assuming the spin-parity assignments of the hypothetical hidden-bottom resonances Pb+,0(11080), Pb+,0(11125) and Pb+,0(11130) as JP=(1/2)−, JP=(1/2)− and JP=(3/2)− within four different realistic choices for the branching ratios of their decays to the ϒ(1S)p and ϒ(1S)n modes (0.125, 0.25, 0.5 and 1%) as well as for two options for the background contribution. We demonstrate that the measurements of these combined observables on proton and nuclear targets in the near-threshold energy region in future experiments at the planned high-luminosity electron-ion colliders EIC and EicC in the US and China should provide evidence for the existence of the above hidden-bottom pentaquark resonances as well as clarify their decay rates.