Identified Particle Spectra and Anisotropic Flow in an Event-by-Event Hybrid Approach in Pb+Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV

TL;DR

This study applies an event-by-event hybrid model to Pb+Pb collisions at 2.76 TeV, successfully describing bulk observables and making predictions for identified particle spectra and flow, testing the model's validity at higher energies.

Contribution

The paper extends a hybrid approach with ideal hydrodynamics to higher collision energies without parameter changes, providing new insights into heavy ion collision dynamics at the LHC.

Findings

Reasonable agreement with ALICE data for multiplicity, spectra, and elliptic flow.

Similar eccentricities and fluctuations compared to lower energies.

Predictions for transverse mass spectra and triangular flow.

Abstract

The first results from heavy ion collisions at the Large Hadron Collider for charged particle spectra and elliptic flow are compared to an event-by-event hybrid approach with an ideal hydrodynamic expansion. This approach has been shown to successfully describe bulk observables at RHIC. Without changing any parameters of the calculation the same approach is applied to Pb+Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. This is an important test if the established understanding of the dynamics of relativistic heavy ion collisions is also applicable at even higher energies. Specifically, we employ the hybrid approach with two different equations of state and the pure hadronic transport approach to indicate sensitivities to finite viscosity. The centrality dependence of the charged hadron multiplicity, $p_T$ spectra and differential elliptic flow are shown to be in reasonable agreement with the ALICE data. Furthermore, we make predictions for the transverse mass spectra of identified particles and triangular flow. The eccentricities and their fluctuations are found to be surprisingly similar to the ones at lower energies and therefore also the triangular flow results are very similar. Any deviations from these predictions will indicate the need for new physics mechanisms responsible for the dynamics of heavy ion collisions.