we need to incorporate collective flow in EV-SHGM to explain the centrality dependence of $E_{T}/N_{ch}$ at LHC energies. After comparison with data, we find that our model with flow explains the data very well over all the centrality bins within the experimental uncertainties. In ref. [@Heinz:2007in], it is argued that in a kinetic freeze-out scenario, the temperature should depend on centrality because during the kinetic freeze-out process there is a competition between local scattering and global expansion. Thus, the kinetic temperature is sensitive to the freeze-out process and hence centrality dependent. In the case of chemical freeze-out, the temperature is observed to be centrality independent [@Adams:2003xp]. This is because during this process, the chemical reactions decrease abruptly leaving behind the chemically frozen state at the freeze-out and thus the chemical freeze-out temperature is insensitive to the collective dynamics but depends on thermodynamical variables. The observation of a centrality independence of $E_{T}/N_{ch}$ at RHIC and LHC thus indicates to the chemical freeze-out scenario. This argument could be strengthened further in the subsequent section, when we make a direct comparison of $E_{T}/N_{ch}$ values with the universal freeze-out criteria.

![The variation of $\epsilon_{Bj}\tau$ with respect to $\sqrt{s_{NN}}$ for the most central collisions. Solid 