Event-by-event net-charge fluctuations in pp, OO, Ne-Ne, and Pb-Pb collisions with ALICE at the LHC

Abstract

Investigations involving the event-by-event fluctuations of conserved quantities, like net charge, net baryon number, and strangeness in heavy-ion collisions, provide insights into the properties of quark-gluon plasma (QGP) and the phase diagram of strongly interacting matter. Event-by-event fluctuations of net electric charge in pp collisions at $\sqrt{s} = 13$ and $13.6$ TeV and for OO, Ne-Ne, and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.36$ TeV are studied by analysing the data collected by the ALICE detector at CERN Large Hadron Collider. The analysis is carried out in terms of the variable $ν_{\mathrm{dyn}}[+,-]$, chosen for its robustness against detector efficiency losses. The observed dependence of $ν_{\mathrm{dyn}}[+,-]$ on the charged-particle density shows a smooth, energy-independent decrease in the magnitude of $ν_{\mathrm{dyn}}[+,-]$ from smaller to larger collision systems. The negative values of $ν_{\mathrm{dyn}}[+,-]$ indicate a dominance of correlations between oppositely charged particle pairs compared with those arising from like-sign charge pairs. Since $ν_{\mathrm{dyn}}[+,-]$ is known to have an intrinsic dependence on multiplicity, an appropriate scaling is applied. The variable is therefore scaled with the mean multiplicities, $\frac{1}{\frac{1}{\langle N_+ \rangle} + \frac{1}{\langle N_- \rangle}}$. The dependence of the scaled values of $ν_{\mathrm{dyn}}[+,-]$ on charged particle density is also looked into. The results are compared with model calculations from PYTHIA, EPOS4, AMPT and HIJING.