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

Abstract

We apply a data-driven method to STAR Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV to isolate $Δη$-dependent and $Δη$-independent correlations by using two- and four-particle Q-cumulant $v_{n}$ measurements. The $Δη$-independent part, dominated by flow, is found to be $η$-independent within the STAR TPC of $\pm1$ unit of pseudo-rapidity. The $Δη$-dependent part may be associated to nonflow, and is responsible for the $Δη$ 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.