ATLAS Plot: Ratio of the yield of charged particles opposite in angle to a Z boson between lead-lead collisions and proton-proton collisions.

Ratio of the yield of charged particles opposite in angle to a Z boson between lead-lead collisions and proton-proton collisions. The charged particles are the result of jet fragmentation. As a result of the jet quenching process, the ratio is below one at high transverse momentum (pTch), and above one at low transverse momentum. The data (red) are compared to theoretical predictions (purple, blue, green yellow).