$R_\mathrm{long}^2$ fitted with Eq. (10) for eight centrality classes: 0$-$5%, 5$-$10%, 10$-$20%, 20$-$30%, 30$-$40%, 40$-$50%, 50$-$70%, and 70$-$90%. Statistical uncertainties are shown as bars and systematic uncertainties are depicted as boxes. The width of the bands represents the uncertainties of the power-law fit.