Study of χc2 production in photon-photon collisions ☆

Abstract Two-photon production of the charmonium state χ c has been studied by the TPC/Two-Gamma experiment at the SLAC e + e − collider PEP. We observe evidence of the χ c 2 state in the channel γγ → χ c 2 , χ c 2 → γJ / ψ , J / ψ → l + l − and obtain a value of Γ γγ ( χ c 2 )=3.4±1.7±0.9 keV. This is the first observation of the two-photon production of a χ c state. Comparison is made with previous experimental results and QCD predictions for Γ γγ ( χ c 2 ).