Inclusive Pomeron-Pomeron interactions at the CERN ISR

Data are presented for the first time on inclusive Pomeron-Pomeron interactions which produce a central systemX (composed mainly of multimeson states) in proton-proton collisions at\(\sqrt s \) at the CERN ISR. The systemX has a Feynman-x distribution which is sharply peaked atxf=0, is inconsistent with any significant contributions from Reggeon exchange processes, and has an invariant mass dependence in good agreement with the predicted formM x −2 . Kaon production is about 15% of pion production, nearly independent ofMx, while proton-antiproton production averages about 5% of pion production and increases withMx. The structure of the central systemX develops into a jetlike shape, asMx increases, as would be expected from a model of Pomeron fragmentation. The shape of thexf(π) distribution in the center of mass of theX system (although not proving existence) is consistent with asoft partonic substructure of the Pomeron.