Factorization of two-particle distributions in AMPT simulations of Pb-Pb collisions at $\mathbf{\sqrt{s_{\text{NN}}}} $ = 5.02 TeV

TL;DR

This paper investigates the factorization of two-particle distributions in heavy ion collisions using AMPT simulations at 5.02 TeV, exploring how fluctuations and non-flow effects influence the validity of the factorization assumption.

Contribution

It introduces a largely detector-independent method to analyze factorization breaking in two-particle Fourier coefficients in heavy ion collision simulations.

Findings

Identifies the minimal pseudorapidity gap for factorization validity.

Quantifies $ ext{Δ} ext{η}$-dependent decorrelation effects in AMPT data.

Compares decorrelation effects with CMS experimental results.

Abstract

The flow ansatz states that the single-particle distribution of a given event can be described in terms of the complex flow coefficients $V_n$. Multi-particle distributions can therefore be expressed as products of these single-particle coefficients; a property commonly referred to as factorization. The amplitudes and phases of the coefficients fluctuate from event to event, possibly breaking the factorization assumption for event-sample averaged multi-particle distributions. Furthermore, non-flow effects such as di-jets may also break the factorization assumption. The factorization breaking with respect to pseudorapidity $\eta$ provides insights into the fluctuations of the initial conditions of heavy ion collisions and can simultaneously be used to identify regions of the phase space which exhibit non-flow effects. These proceedings present a method to perform a factorization of the two-particle Fourier coefficients $V_{n\Delta}(\eta_a, \eta_b)$ which is largely independent of detector effects. AMPT model calculations of Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 5.02$ TeV are used to identify the smallest $|\Delta\eta|$-gap necessary for the factorization assumption to hold. Furthermore, a possible $\Delta\eta$-dependent decorrelation effect in the simulated data is quantified using the empirical parameter $F_2^\eta$. The decorrelation effect observed in the AMPT calculations is compared to results by the CMS collaboration for Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 2.76$ TeV.