Figure 2

$< N_{\rm {ch}}>\nu^{corr}_{(+-,dyn)}$ (left axis) and $D$ (right axis) as a function of the number of participants for $\Delta \eta$=1 and 1.6 in Pb-Pb at $\sqrt{s_{\rm NN}}=2.76$ TeV and pp collisions at $\sqrt{s}=2.76$ TeV. Corresponding results from the HIJING and PYTHIA event generators are also presented. The data points are shifted minimally along $x$-axis for clear view. Both statistical (error bar) and systematic (box) errors are plotted.