A day of xenon collisions at CERN

On Friday, the Large Hadron Collider at CERN had a day of smashing xenon nuclei together, a departure from its usual diet of protons or lead

The picture at the top shows what happened in the CMS particle detector when xenon nuclei were circulated in the LHC and brought into head-on collision. The yellow is made up of tracks of electrically-charged particles, produced in such numbers that the whole of the centre of the picture is a yellow blur, with individual tracks only visible near the edges. The blue and green blocks indicate energy deposited by both charged and neutral particles in the CMS calorimeter.

Collisions between protons look significantly less busy than this, with fewer particles produced. But both xenon and lead nuclei are packed with protons and neutrons, and though lead has more of them, by eye I don't think anyone could tell the difference between a xenon-xenon collision and a lead-lead one.