  The formation of weakly bound clusters in the hot and dense environment at
midrapidity is one of the surprising phenomena observed experimentally in
heavy-ion collisions from a low center of mass energy of a few GeV up to a
ultra-relativistic energy of several TeV. Three approaches have been advanced
to describe the cluster formation: coalescence at kinetic freeze-out, cluster
formation during the entire heavy-ion collision by potential interaction
between nucleons and deuteron production by hadronic reactions. We identify
experimental observables, which can discriminate these production mechanisms
for deuterons.
