Central exclusive production

Central exclusive production is any process of the form

$\text{p}\text{p} \to \text{p} + \text{X} + \text{p}\;,$

where $\text{X}$ is any system in the rapidity gap between the two final-state protons, hence called central. The production of $\text{X}$ is exclusive, because the hadronic final state is fully specified: the scattering protons remain intact and there are no beam remnants due to breaking-up protons.

In hadron collisions other than proton--proton, the incoming and outgoing particles are replaced accordingly.