Fourier coefficients $v_{n}$, with $n=2,3,4$,extracted from US and LS $R_{2}$ correlation functions in the range$0.2 \leq |\Delta\eta| \leq 0.9$ and $0.9 \leq |\Delta\eta| \leq 1.9$ in panels(a) and (b), respectively. The ratios between US and LS $v_{n}$coefficients are shown in panels (c) and (d). Vertical bars and shaded areas represent statistical and systematic uncertainties, respectively.