$\epsilon\tau_{\mathrm 0}$ versus $\langle N_{\mathrm{part}} \rangle$ estimated using, $R = 7.17$ fm, and the measured $\langle $d$E_{\mathrm T}/$d$\eta \rangle$/$\langle $d$N_{\mathrm{ch}}/$d$\eta \rangle$. The boxes indicate the systematic uncertainties.