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 Γγγ(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 Γγγ(ηc)<15.5 keV, Γγγ(χ0)<17.0 keV, and Γγγ(χ2)<4.2 keV. From all channels combined, we obtain the value Γγγ(ηc)=6.4-3.4+5.0 keV.