Probing QGP using local charge fluctuations in heavy-ion collisions

Abstract

We revisit the D-measure of event-by-event net-electric charge fluctuations, an idea first introduced over 20 years ago as a potential signature for the presence of quark-gluon plasma (QGP) in heavy-ion collisions. We developed a quantitative framework that incorporates resonance-decay effects, global and local charge conservation, and experimental kinematic cuts. Folding these effects into a formalism of density correlations yields an improved expression for the $D$-measure inside acceptance. We make comparisons with ALICE data for Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$~TeV. We find that a hadron-gas scenario can describe the data only for a very short charge conservation range, while a QGP scenario is in good agreement with the measurement and is relatively insensitive to the charge conservation range. A Bayesian comparison of both scenarios shows moderate evidence for freeze-out of charge fluctuations in the QGP phase.