  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.
