Near-threshold production of phi mesons in pp collisions.

The pp{yields}pp{phi} reaction has been studied at the Cooler Synchrotron COSY-Juelich, using the internal beam and ANKE facility. Total cross sections have been determined at three excess energies {epsilon} near the production threshold. The differential cross section closest to threshold at {epsilon}=18.5 MeV exhibits a clear S wave dominance as well as a noticeable effect due to the proton-proton final-state interaction. Taken together with data for pp{omega} production, a significant enhancement of the {phi}/{omega} ratio of a factor 8 is found compared to predictions based on the Okubo-Zweig-Iizuka rule.