Angular Power Spectrum and Elliptic Flow from Event Maps in Heavy Ion Collisions

TL;DR

This paper demonstrates that the HEALPix pixelization method, originally designed for cosmic microwave background analysis, can effectively analyze azimuthal and polar angle distributions in heavy ion collisions to detect elliptic flow, revealing insights into the Quark Gluon Plasma.

Contribution

It introduces the application of HEALPix to heavy ion collision data for analyzing angular distributions and detecting elliptic flow, expanding its use beyond cosmology.

Findings

HEALPix successfully detects elliptic flow in lead-lead collisions.

The angular power spectrum correlates with particle flow in heavy ion collisions.

HEALPix provides a broader application in QGP studies.

Abstract

Azimuthal and polar angle distributions of particles produced in heavy ion collisions carry important information about the early state of the system and the evolution of the Quark Gluon Plasma. The pixelization code HEALPix was created by the Jet Propulsion Laboratory to analyze the cosmic microwave background. As has been shown using public data from the ALICE experiment, its two-dimensional representation of a sphere containing pixels of equal area has a broader application to heavy ion collisions. The angular power spectrum, an application of HEALPix, is directly related to the particle flow and is calculated through the angles theta and phi on the sphere. The elliptic flow is calculated from simulated AMPT events and publicly available CMS data. We show that HEALPix can be used to detect the presence of elliptic flow for lead-lead collisions and thus has broader applications in the study of QGP in heavy ion collisions.