The Study of Noncollectivity by the Forward-Backward Multiplicity Correlation Function

TL;DR

This paper introduces a forward-backward multiplicity correlation function to distinguish noncollective effects like jets from collective phenomena in heavy-ion collisions, revealing that particle scarcity influences observed correlations.

Contribution

The study proposes a new correlation function sensitive to noncollective contributions and demonstrates its effectiveness using AMPT simulations in Au+Au collisions.

Findings

$C^N_{FB}$ is sensitive to jet contributions in particle-rich cases.

$C^N_{FB}$ decreases with particle scarcity, not just jets.

Jet fraction increases with transverse momentum, reaching 30% at 3.5 GeV/c.

Abstract

We propose a forward-backward multiplicity correlation function $C^N_{FB}$, which is experimentally accessible, to measure the noncollectivity contribution. We find that $C^N_{FB}$ is sensitive to the jet contribution for the particle-rich case. Surprisingly, it will automatically decrease for the particle-rare case. Our study indicates that similar decreasing trend observed previously is mainly driven by particle scarcity instead of jets. The function is studied in Au+Au collision at $\sqrt{s_{NN}}=200$ GeV with a multiphase transport model (AMPT). We find that the jet fraction is about 10% at transverse momentum ($p_T$) around 2.5 GeV/$c$ and reaches up to 30% at 3.5 GeV/$c$. The implication of this study in the investigation of the noncollectivity contribution in elliptic anisotropy parameter $v_2$ is also discussed.