Double J/psi production at photon colliders - art. no. 077503

The double J/psi (DJ) production in direct photon-photon collision is inves tigated. It is found that the J/psi production rate in this process is of t he same order of magnitude as those of previously discussed rates, which hi nts that the dominant J/psi inclusive production process in the direct phot on-photon collision is still not being touched. As the DJ production proces s has a clear distinction from the single J/psi inclusive processes in the final states, an experimental study of it would be helpful to clarify the v alidity of the color-singlet model.