Figure 3

Combined PCM and PHOS double ratio $R_\gamma$ in Pb-Pb collisions at $\snn$=2.76 TeV for the 0-20%, 20-40%, and 40-80% centrality classes. The errors in this plot are split into fully uncorrelated errors (stat. $\oplus$ syst. A), displayed as error bars, systematic uncertainties correlated in $\pT$ (syst. B), shown as empty boxes around the points, and a normalization uncertainty (syst. C), shown as filled boxes around 1.