Event by event di-hadron correlations in Pb-Pb 2.76 TeV collisions from the ALICE experiment

TL;DR

This paper investigates event-by-event di-hadron correlations in Pb-Pb collisions at 2.76 TeV to study flow harmonic fluctuations and initial condition variability at the LHC.

Contribution

It introduces a method to extract flow harmonics from event-by-event di-hadron correlations, revealing large fluctuations in initial conditions within centrality bins.

Findings

Correlation functions vary significantly event-by-event.

Some events are dominated by specific flow harmonics.

Unfolded v2 distributions show large fluctuations.

Abstract

The large multiplicities at the LHC may permit flow harmonics to be determined on an event by event basis in Pb-Pb collisions. We extract these harmonics from event by event di-hadron correlations. Within a fine centrality bin, we find the correlation function varies substantially on an event by event basis, indicating large fluctuations in the initial conditions for a given impact parameter. Such large fluctuations lead to some events being highly triangular or highly elliptical, where the angular correlation function is completely dominated by the respective second and third Fourier harmonics. We will show unfolded $v_{2}$ distributions for various centralities, and implications for our understanding of the initial conditions.