Double charmonium production in e+e− annihilation at

The observation of the processes e+e−→J/ψηc, J/ψχc0, and J/ψηc(2S) 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/ψJ/ψ is found. An angular analysis for production is performed and an upper limit on the production of J/ψJ/ψ is set. Processes of the type have been observed for the first time; their rates are found to be comparable to those of 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.