Double charmonium production in annihilation at

Abstract

The observation of the processes e + e − → J / ψ η c , J / ψ χ c 0 , and J / ψ η c ( 2 S ) is confirmed using a dataset more than three times larger than that of Belle's previous report, and no evidence for the process e + e − → J / ψ J / ψ is found. An angular analysis for J / ψ ( c c ¯ ) res production is performed and an upper limit on the production of J / ψ J / ψ is set. Processes of the type e + e − → ψ ( 2 S ) ( c c ¯ ) res have been observed for the first time; their rates are found to be comparable to those of e + e − → J / ψ ( c c ¯ ) res processes. The first observation of a new charmonium-like state at a mass of (3.943 ± 0.006 ± 0.006) GeV/c2is reported. This state, denoted as X(3940), is observed in the spectrum of masses recoiling from the J / ψ in the inclusive process e + e − → J / ψ + anything.