On the pp → ppη(η′) reactions near threshold

The production rate for η′ in pp → ppη′ at rest is calculated in a covariant one boson exchange model, previously applied to study π0 and η production in NN collisions. The transition amplitudes for the elementary BN → η′N processes with B being the meson exchanged (B = π, σ, η, ρ, ω and α0) are taken to be the sum of s- and w-channels with a nucleon in the intermediate states, and an α0 meson pole in a t-channel. The couplings of the η′ to hadrons are a factor 0.4 weaker than the respective η-hadron couplings, as suggested by a quark model and a singlet-octet mixing angle θ = -23°. The model reproduces near threshold cross sections for the quasielastic processes π- p → nη(η′) and pp → ppη(η′) reactions.