Inclusive correlations in the central region

Hadron correlations at very high energies are discussed. These correlations are discussed first from the point of view of the cluster picture. The cluster picture attempts to explain why the correlations are present in data by postulating a few simple properties for objects called clusters. Unfortunately, the clusters make no direct contact with known physical mechanisms. To attempt a remedy, the correlations are then discussed from a more fundamental viewpoint. One tries to see how people have tried to describe the data as due to resonance production and decay. The dynamics are supposed to be that of Regge exchanges. A simple Mueller-Regge exercise is described and shown to work qualitatively. The last topic considered is that of coherent interferences as a possible source of hadron correlations. It is argued that these interference phenomena are a natural consequence of resonance production. Based on available data, known resonances and their coherent interferences do not account for the observed correlations