Searches for transverse momentum dependent flow vector fluctuations in Pb-Pb and p-Pb collisions at the LHC

TL;DR

This study investigates transverse momentum dependent flow vector fluctuations in Pb-Pb and p-Pb collisions at the LHC, revealing that such fluctuations are only present for the second order flow vector and comparing results with hydrodynamic models.

Contribution

It provides the first detailed measurement of $p_{T}$-dependent flow vector fluctuations in both Pb-Pb and p-Pb collisions at the LHC, enhancing understanding of initial state fluctuations.

Findings

$p_{T}$-dependent fluctuations are only observed for the second order flow vector.

Results are consistent across Pb-Pb and p-Pb collision systems.

Data constrains hydrodynamic models of initial conditions.

Abstract

The measurement of azimuthal correlations of charged particles is presented for Pb-Pb collisions at $\sqrt{s_{\rm NN}}=$ 2.76 TeV and p-Pb collisions at $\sqrt{s_{\rm NN}}=$ 5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. These correlations are measured for the second, third and fourth order flow vector in the pseudorapidity region $|\eta|<0.8$ as a function of centrality and transverse momentum $p_{\rm T}$ using two observables, to search for evidence of $p_{\rm T}$-dependent flow vector fluctuations. For Pb-Pb collisions at 2.76 TeV, the measurements indicate that $p_{\rm T}$-dependent fluctuations are only present for the second order flow vector. Similar results have been found for p-Pb collisions at 5.02 TeV. These measurements are compared to hydrodynamic model calculations with event-by-event geometry fluctuations in the initial state to constrain the initial conditions and transport properties of the matter created in Pb-Pb and p-Pb collisions.