Figure 3

Comparison of double ratios $R_\gamma$ measured with PCM and PHOS for the 0-20%, 20-40%, and 40-80% centrality classes. Error bars reflect the statistical and type A systematic uncertainty, the boxes represent the type B and C systematic uncertainties. The cancellation of uncertainties (energy scale, material budget) in the double ratio $R_\gamma$ is taken into account in the shown systematic uncertainties.