Event-by-Event correlations and fluctuations with strongly intensive quantities in heavy-ion and

This paper presents a short overview of event-by-event correlations and fluctuations analysis with strongly intensive quantities measured by ALICE at LHC in pp, p--Pb, Xe--Xe, and Pb--Pb collisions in the overall energy regime ranging from $\sqrt{s_{\rm NN}}=0.9$ up to 13~TeV. The evolution of the forward-backward strongly intensive quantity $\Sigma$ is analyzed as a function of the distance between forward and backward pseudorapidity intervals ($\eta$ gap), the centrality of the collision, and the width of the centrality bin. The observable is studied by means of different centrality estimators. The net-charge fluctuations with $\nu_{\rm dyn}[+,-]$, are examined as a function of charged-particle density (d$N_{\rm ch}$/d$\eta$). Our study demonstrates that $\Sigma$ indeed exhibits the properties of a strongly intensive quantity in terms of the independent source models, providing information on the early collision dynamics which is far more direct than that obtained from $b^{n-n}_{\rm corr}$. The measured negative values of $\nu_{\rm dyn}[+,-]$ indicate the dominance of the correlation between oppositely charged particles. A smooth evolution of net-charge fluctuations is observed from small to large collision systems.