The authors report a measurement of the diffractive structure function of the antiproton for dijet events produced in association with a leading antiproton in {anti p}p collisions at (square root)(s) = 1800 GeV. Comparing their results with expectations based on parton densities extracted by the H1 Collaboration from diffractive deep inelastic scattering at the DESY ep collider HERA, the authors find a severe breakdown of QCD factorization.

We present new results from studies on diffractive dijet production and exclusive production of dijet and diphoton obtained by the CDF Collaboration in proton-antiproton collisions at the Fermilab Tevatron.

Experimental results in diffractive processes are summarized and a few notable characteristics described in terms of Quantum Chromodynamics. Exclusive dijet production is used to establish a benchmark for future experiments in the quest for diffractive Higgs production at the Large Hadron Collider. Using new data from the Tevatron and dedicated diffractive triggers, no excess over a smooth falling distribution for exclusive dijet events could be found. Stringent upper limits on the exclusive dijet production cross section are presented. The quark/gluon composition of dijet final states is used to provide additional hints on exclusive dijet production.

We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the D0 experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is 2 x 10−5, corresponding to a 4.1 standard deviation significance.

Proceedings of the NATO Advanced Research Workshop, Alushta, Crimea, Ukraine, from 31 August to 6 September 2002

We report on a study of diffractive dijet production in {bar p}p collisions at √s = 1.96 TeV using the CDF II detector at the Fermilab Tevatron {bar p}p collider. A data sample from 310 pb−1 of integrated luminosity collected by triggering on a high transverse energy jet, E{sub T}{sup jet}, in coincidence with a recoil antiproton detected in a Roman pot spectrometer is used to measure the ratio of single-diffractive to inclusive-dijet event rates as a function of x{sup {bar p}} of the interacting parton in the antiproton, the Bjorken-x, x{sub Bj}{sup {bar p}}, and a Q2 ≈ (E{sub T}{sup jet})2 in the ranges 10−3 x{sub Bj}{sup {bar p}}

The authors report the observation of dijet events with a Double Pomeron Exchange topology produced in {bar p}p collisions at (square root)s = 1,800 GeV. The events are characterized by a leading antiproton, two jets in the central pseudorapidity region, and a rapidity gap on the outgoing proton side. Results on kinematics, production rates, and comparisons with corresponding results from single diffractive and inclusive dijet production are presented.