Investigating the cluster production mechanism with isospin triggering: Thermal models versus coalescence models

Isospin triggering allows to distinguish coalescence from thermal production of light clusters in heavy ion collisions. Triggering on Y(r-) - Y(r+) allows to select very neutron or proton rich final states. The deuteron (cluster) production with coalescence (d proportional to n center dot p) leads then to an inverse parabolic dependence of the deuteron yield on AYr. In contrast, in a thermal model, cluster production is independent on AYr. The observation of a maximum deuteron (cluster) yield as function of AYr provides confirmation of the coalescence mechanism.