Among the myriad of protons and lead nuclei collisions at the LHC, other particles are colliding more quietly. These are photon-photon and photon-nucleus collisions. Between 2015 and 2018, the ALICE experiment was able to collect enough data on these very special interactions to draw up an initial portrait of them. The result is a better understanding of the role of gluons in the composition of nuclei and of quantum coherence, and perhaps, in the near future, a new probe of the primordial state of matter that existed a few microseconds after the Big-Bang.

More information in this IN2P3 news item whose work was partly carried out by the ALICE group of IP2I.