NA61/SHINE shining more light on the onset of deconfinement

NA61/SHINE has recently completed data acquisition for its original programme on strong interactions. The Collaboration has gathered rich data on collisions of ions in a two-dimensional scan: varying the beam energy and the sizes of colliding nuclei. The most recent analysis of hadron production in ${}^{40}$Ar+${}^{45}$Sc and ${}^7$Be+${}^9$Be interactions deliver some puzzling results which none of the theoretical models can reproduce.