Non-flow, and what flow to subtract in jet-correlation

TL;DR

This paper derives analytical formulas for non-flow contributions in elliptic flow measurements and discusses how to accurately determine the flow background in jet-correlation analyses, verified by simulations.

Contribution

It provides new analytical expressions for non-flow effects and jet-correlation flow-background, clarifying how to select the appropriate v2 parameter for jet studies.

Findings

Analytical forms for non-flow contributions from cluster correlations.

Derived jet-correlation flow-background expression using cluster approach.

Verified formulas with Monte Carlo simulations.

Abstract

We derive analytical forms for non-flow contributions from cluster correlation to two-particle elliptic flow (v2{2}) measure. We also derive an analytical form for jet-correlation flow-background with the same cluster approach. We argue that the elliptic flow v2 parameter to be used in jet-correlation background is that from two-particle method excluding non-flow correlations unrelated to the reaction plane, but including cross-terms between cluster correlation and cluster flow. We verify our result with Monte Carlo simulations. We discuss how one may obtain the v2 parameter for jet-correlation background experimentally.