Central exclusive quarkonium production with tagged forward protons at RHIC

Understand

We study the Central Exclusive Production (CEP) of chi_cJ and eta_c mesons at RHIC in proton-proton collisions.

• We consider the chi_cJ --> J/psi + gamma decay channels and, recalling that the J_z=0 suppression of the J=1,2 states can be compensated by their larger branchings to J/psi + gamma, present predictions of rates and distributions for chi_c(0,1,2) production.
• Particular attention is paid to the impact of p_t cuts applied to the outgoing protons, which can influence the relative rates significantly.
• The distribution in the azimuthal angle difference between the outgoing protons and the proton p_t^2 is also studied, and shown to depend sensitively on the spin and parity of the centrally produced meson, as well as being affected by the soft survival factors, S^2.