Event shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at $\sqrt{s_\rm{NN}}=2.76$ TeV

TL;DR

This paper uses Event Shape Engineering to study how initial state fluctuations affect elliptic flow and particle spectra in Pb-Pb collisions at 2.76 TeV, revealing correlations between flow and particle hardness.

Contribution

It introduces the application of Event Shape Engineering to analyze initial state effects on flow and spectra in heavy-ion collisions at LHC energies.

Findings

Event-shape selection affects elliptic flow coefficient $v_2$ independently of transverse momentum.

Higher-than-average elliptic flow events have harder transverse momentum distributions.

Initial geometry fluctuations influence both elliptic flow and radial flow interplay.

Abstract

We report on results obtained with the Event Shape Engineering technique applied to Pb-Pb collisions at $\sqrt{s_\rm{NN}}=2.76$ TeV. By selecting events in the same centrality interval, but with very different average flow, different initial state conditions can be studied. We find the effect of the event-shape selection on the elliptic flow coefficient $v_2$ to be almost independent of transverse momentum $p_\rm{T}$, as expected if this effect is due to fluctuations in the initial geometry of the system. Charged hadron, pion, kaon, and proton transverse momentum distributions are found to be harder in events with higher-than-average elliptic flow, indicating an interplay between radial and elliptic flow.