Charmonium Production in Photon-Photon Collisions

We have searched for the two-photon production of the ηc, χ₀, and χ₂ charmonium states at the SLAC e⁺e^- collider PEP in the channels γγ→K^±KS⁰π^∓, γγ→K⁺K^-π⁺π^-, γγ→π⁺π^-π⁺π^-, and γγ→K⁺K^-K⁺K^-. We identify four ηc candidates in the K⁺K^-K⁺K^- channel on a negligible background; the one φφ event among them implies a 95%-confidence-level (C.L.) lower limit for Γ_γγ(ηc) of 1.7 keV. In the other channels we find no evidence for any of the three states. We establish 95%-C.L. upper limits Γ_γγ(ηc)<15.5 keV, Γ_γγ(χ₀)<17.0 keV, and Γ_γγ(χ₂)<4.2 keV. From all channels combined, we obtain the value Γ_γγ(ηc)=6.4_-3.4+5.0 keV.