The first experimental measurement of the proton-proton cross-section at 7 TeV is reported by the ATLAS collaboration at the Large Hadron Collider (LHC) this week in Nature Communications. This finding marks the highest energy collision for protons observed to date. These data are important for modelling cosmic ray showers and validating our understanding of high-energy particle interactions.

The cross-section describes the probability for two particles to collide and depends on the energy of the particles. Understanding the rate of proton interactions is fundamentally important for particle physics but it cannot be worked out from existing theories. The team at ATLAS determined this rate by measuring the subatomic products resulting from the colliding protons using the ATLAS detector.

The results confirm previous predications for the behaviour of high-energy protons.