Pair separation, $|\Delta\eta|$, dependence of Fourier coefficients$v_{n}[R_2^{\rm (CI)}]$ (panel a) and $v_{n}[P_2^{\rm (CI)}]$ (panel b), with $n=2,3,4$,obtained from $R_2^{\rm (CI)}$ and $P_2^{\rm (CI)}$ correlation functions in \PbPb\ 5\% most central collisions. Panels (c,d) display ratios of the coefficients to $v_n(|\Delta\eta|)$ to their respective values at $|\Delta\eta|=0.3$. Vertical bars and shaded areas indicate statistical and systematic uncertainties, respectively. Reproduced from .