# The Angular Power Spectrum of Heavy Ion Collisions

## TL;DR

This paper analyzes the angular power spectrum of particle multiplicities in heavy ion collisions to understand early state anisotropies and extract flow coefficients, providing new insights into Quark Gluon Plasma dynamics.

## Contribution

It introduces the use of angular power spectrum analysis to study fluctuations and flow coefficients in heavy ion collision data, a novel approach in this context.

## Key findings

- Odd modes follow a power-law with index close to one
- Angular power spectrum accurately extracts flow coefficients
- Results based on Pb-Pb collision data at 2.76 TeV

## Abstract

Particles produced in heavy ion collisions carry information about anisotropies present already in the early state of the system and play a crucial role in understanding the Quark Gluon Plasma and its evolution. We explore the angular power spectrum of particle multiplicities in such heavy ion collisions to extract fluctuations in particle multiplicities on the surface a sphere. Results are presented for Pb-Pb data at $\sqrt{s_{NN}} = 2.76\mathrm{TeV}$, extracted from the ALICE open data portal. We find that odd modes of the power spectrum display a power-law behavior with corresponding index $\beta$, which is found to be close to unity. We also demonstrate that the angular power spectrum allows us to extract accurately the flow coefficients of non-central collisions.