Explain the common crossing of centrality-dependent modification factors

Identify the mechanism responsible for the observation that the rescaled nuclear modification factors for proton-proton, proton-oxygen, oxygen-oxygen, and lead-lead collision systems are all approximately unity at about thirty-percent centrality.

Background

The paper compares the centrality dependence of the rescaled nuclear modification factor across collision systems of different sizes. Although the magnitude of the deviation from unity varies systematically with system size, all four systems display an approximate crossing near thirty-percent centrality.

This common behavior is reported as an empirical feature of the calculation, but the authors do not identify a dynamical or geometrical mechanism that explains it.