Energy density in small systems equal to the one in heavy-ion collisions

Abstract

The recent developments in the study of quark–gluon matter at high densities have shown that there are many similarities between the behavior of the observables in light and heavy systems, especially when the light systems are observed at high multiplicities. Contrary to what was previously thought, the small systems do exhibit collective effects that could indicate that small droplets of strongly interacting quark–gluon plasma are possible. The results infer that the energy densities can be computed in light systems in the same way as in heavy systems and hence, the energy density should be considered when comparing systems with different sizes. We review some of the aspects as well as the existing main models and the way to disentangle them using experimental data.