Particle correlations in proton-nucleus and nucleus-nucleus collisions

Experimental studies of particle correlations in proton-nucleus and nucleus-nucleus collisions at beam energies of 1-2 A GeV are reviewed. Data are categorized into two types. One is those which provide fundamental information on the basic reaction mechanism. For example, the nucleon mean free path, interaction radius, the fraction of the direct knock-out component, the pion-to-proton ratio, and the role of cluster in backward proton emission have been studied. The other is the data that have not yet been explained within the framework of orthodox theories. Hints of hydrodynamical flows are observed in these data. Finally, future experimental possibilities are discussed