Fourier coefficients of noninterdependent collective motions in heavy-ion collisions

TL;DR

This paper explores a scenario in heavy-ion collisions where multiple noninterdependent collective motions influence particle distributions, leading to observable effects and new experimental test proposals.

Contribution

It introduces a model where noninterdependent collective modes produce product-form azimuthal distributions, affecting the interpretation of phenomena like the CME and flow harmonics.

Findings

Nonleading cross terms significantly impact observables.

Separate development of CME and elliptic flow is possible.

Proposes experimental tests using conventional flow harmonics.

Abstract

We present a scenario in heavy-ion collisions where different modes of collective motions are noninterdependent, driven by factorized actions in the created nuclear medium. Such physics mechanisms could each dominate at a distinct evolution stage, or coexist simultaneously. If the probability of particle emission is modulated by each nondependent collective motion with a single-harmonic Fourier expansion, the particle azimuthal distribution should be the product of all these expansions. Consequently, nonleading cross terms between collectivity modes appear, and their contributions to experimental observables could be significant. In particular, we argue that the chiral magnetic effect (CME) and elliptic flow can develop separately, with their convolution affecting the observable that is sensitive to the shear-induced CME. We will use the event-by-event anomalous-viscous fluid dynamics model to illustrate the effects of this scenario. Besides giving insights into searches for the CME, we also propose feasible experimental tests based on conventional flow harmonics, and demonstrate the emergence of nonleading cross terms with a multiphase transport model.