Isolation of Flow and Nonflow by Two- and Multi-Particle Cumulant Measurements of $v_n$ in $\sqrt{s_{NN}}=200$ GeV Au+Au Collisions by STAR

We apply a data-driven method to STAR Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV to isolate $\mathrm{\Delta }\eta$-dependent and $\mathrm{\Delta }\eta$-independent correlations by using two- and four-particle Q-cumulant $v_n$ measurements. The $\mathrm{\Delta }\eta$-independent part, dominated by flow, is found to be $\eta$-independent within the STAR TPC of $\pm 1$ unit of pseudo-rapidity. The $\mathrm{\Delta }\eta$-dependent part may be associated to nonflow, and is responsible for the $\mathrm{\Delta }\eta$ drop in the measured two-particle $v_2$ cumulant. We combine our result to four- and six-particle cumulants to gain further insights on the nature of flow fluctuations.