The universal ψ″/ψ′ ratio as unambiguous signature for hard physics in nuclear reactions and in decays of beauty hadrons

Abstract We suggest the ratio of the ψ ″(3770)/ ψ ′(3686) production cross sections as an unambiguous probe of the dominance of hard, point-like physics in charmonium production. If hard physics dominates the charmonium production the ratio: σ(ψ″) σ(ψ′) ≈ Γ(ψ″→l + l − ) Γ(ψ′→l + l − ) ≈0.1 is independent of the process. We argue that since the dominant D D decay mode of the ψ ″-meson can be detected with a high efficiency at the current facilities the effective counting rate for the ψ ″ production should be comparable to that of the ψ ′ and hence it could be observed at the B -factories. Even in hadron induced processes the ratio will not be changed significantly by final state interactions due to the similar mass and size of these two charmonium states. A possible exception are the charmonium state interactions with low energy particles—comovers—which are especially relevant for heavy ion collisions.