Charge asymmetry dependence of flow and a novel correlator to detect the chiral magnetic wave in a multiphase transport model

Abstract

In a multiphase transport model with the initial electric quadrupole moment, we studied and discussed the charge asymmetry (A ch ) dependence of flow at varied kinematic windows in semicentral Au+Au collisions at √ sNN = 200 GeV. We then proposed a novel correlator W which specially focuses on the difference of elliptic flow between positively and negatively charged hadrons induced by the chiral magnetic wave and, more importantly, is irrelevant to the ambiguous A ch . We found that the distribution of the second order correlator W2 displays a convex structure in the absence of the quadrupole and a concave shape in the presence of the quadrupole. We then studied the response of Wn for both signal and resonance background in a toy model and in analytical calculation. Such a method provides a new way to detect the chiral magnetic wave.

Interpreting the charge-dependent flow and constraining the chiral magnetic wave with event shape engineering

“…The strength of the quadrupole moment is determined by the number of quarks being interchanged. Previous studies suggest that switching ≈3% of total quarks can generate a comparable slope with the experimental result in semi-central collisions [29,30].…”

“…The dependence of v 2 on A ch in AMPT has been studied in Refs. [29,30,34]. Without introducing initial quadrupole moment, AMPT fails to reproduce the A ch -v 2 relation and the contribution from the resonance decay can be either negative or positive depending on the mass.…”

An extended $R^{(2)}_{Ψ_m}(ΔS_2)$ correlator for detecting and characterizing the Chiral Magnetic Wave

“…[38,41]. For CMW-driven charge separation, R Ψm (∆S 2 ), relative to the Ψ 2 and Ψ 3 event planes, are performed with AMPT events in which varying degrees of proxy CMW-driven quadrupole charge separation were introduced [42,43]. The AMPT model is known to give a good representation of the experimentally measured particle yields, spectra, flow, etc., [44][45][46][47][48][49].…”

“…Therefore, it provides a reasonable estimate of both the magnitude and the properties of the background-driven quadrupole charge separation expected in the data collected at RHIC and the LHC. We simulated Au+Au collisions at √ s NN = 200 GeV with the same AMPT model version used in our prior studies [40][41][42]; this version incorporates both string melting and local charge conservation. In brief, the model follows four primary stages: (i) an initial-state, (ii) a parton cascade phase, (iii) a hadronization phase in which partons are converted to hadrons, and (iv) a hadronic re-scattering phase.…”

“…Here, we follow the lead of Ref. [42] by first, extending the correlator for study of the CMW-driven quadrupole charge separation, followed by detailed sensitivity tests of the correlator with the aid of AMPT model simulations.…”