Exclusive Central Meson Production in Proton Antiproton Collisions at the Tevatron

It has been known since the days of the Intersecting Storage Rings, ISR, at CERN, that one can have pp interactions with more than one pomeron, ℙ, exchanged, known as double pomeron exchange. Exclusive hadronic systems, produced by double pomeron exchange, DℙE, have the potential of opening a rich new window on hadron spectroscopy and the diffraction mechanism. We have studied events of the type p + → p + X + where X is a hadron pair (mostly π + π − ) at √ s = 900 GeV and 1960 GeV in the Collider Detector at Fermilab (CDF). The hadron pair is central, y ≈ 0, and between two rapidity gaps Δy ≈ 4. The dominant process is double pomeron exchange, DℙE, with restrictions on the quantum numbers of X: Q = S = 0, C = +1, J = 0 or 2. The mass spectra, with about 300K candidate events assumed to be π + π − , shows strong resonant structures attributed to f 0 and f 2 states. We give the ratio of cross sections at √ s = 900 GeV and 1960 GeV, and compare with Regge expectations.