Event-plane flow analysis without non-flow effects

TL;DR

This paper introduces a simplified Lee-Yang-zeroes method for analyzing anisotropic flow that effectively suppresses nonflow effects, enabling more accurate flow measurements at high transverse momentum in heavy-ion collisions.

Contribution

The paper demonstrates that the Lee-Yang-zeroes method can be reformulated to resemble standard event-plane analysis, reducing nonflow biases using flow vector information.

Findings

Nonflow effects are strongly suppressed using the new method.

The approach improves elliptic flow analysis at RHIC and LHC.

The method simplifies implementation of nonflow-free flow analysis.

Abstract

The event-plane method, which is widely used to analyze anisotropic flow in nucleus-nucleus collisions, is known to be biased by nonflow effects,especially at high $p_t$. Various methods (cumulants, Lee-Yang zeroes) have been proposed to eliminate nonflow effects, but their implementation is tedious, which has limited their application so far. In this paper, we show that the Lee-Yang-zeroes method can be recast in a form similar to the standard event-plane analysis. Nonflow correlations are strongly suppressed by using the information from the length of the flow vector, in addition to the event-plane angle. This opens the way to improved analyses of elliptic flow and azimuthally-sensitive observables at RHIC and LHC.