Charge fluctuations in Pb--Pb collisions at $\sqrt{s_{NN}} = $2.76 TeV measured by ALICE experiment

TL;DR

This paper investigates charge fluctuations in Pb--Pb collisions at 2.76 TeV to identify signatures of the Quark Gluon Plasma, analyzing how fluctuations depend on pseudo-rapidity and comparing results with models and lower-energy data.

Contribution

It presents the first detailed measurement of charge fluctuations at LHC energies using the variable ucharged, revealing scaling behavior and providing insights into QGP signatures.

Findings

Charge fluctuations scale with pseudo-rapidity window size.

Results differ from hadron gas expectations and align with QGP models.

Comparison with lower-energy data supports the presence of QGP signatures.

Abstract

Charge fluctuations provide a possible signature for the existence of the de-confined Quark Gluon Plasma phase (QGP). Being sensitive to the square of the charges, fluctuations in QGP, with fractionally charged partons, are significantly different from those of a hadron gas with unit charged particles. Studies of charge fluctuations have been carried out using the variable, $\nu_{(+-,dyn)}$ which, by its construction, is free from collisional bias (impact parameter fluctuations and fluctuations from the finite number of charged particles within the detector acceptance). The dependence of charge fluctuations on the pseudo--rapidity windows for various centrality bins is analyzed for Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV in the ALICE experiment at CERN-LHC. A scaling behavior is observed as a function of increasing pseudo-rapidity window for the charge fluctuations, expressed in terms of \nchnudyn, where $N_{ch}$ is the number of charged particles. The results are compared to experimental measurements at lower energies and to model predictions.