Testing color evaporation in photon-photon production of [Formula Presented] at CERN LEP II

The DELPHI Collaboration has recently reported the measurement of [Formula Presented] production in photon-photon collisions at CERN LEP II. These newly available data provide additional proof of the importance of colored [Formula Presented] pairs for the production of charmonium, because these data can be explained only by considering resolved photon processes. We show here that the inclusion of color octet contributions to [Formula Presented] production in the framework of the color evaporation model is able to reproduce these data. In particular, the transverse-momentum distribution of the [Formula Presented] mesons is well described by this model. © 2003 The American Physical Society.