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be available. Especially data for protons for which f i core and f i corona differ much less than for the multi-strange hadrons would be of help. Such an analysis will not be easy as can be seen from fig. 8 which shows v$_{2}$ of π ’s as a function of p$_{T}$ for semi-central reactions (20%-60% centrality) (top panel) and that of charged particles as a function of N$_{part}$ (bottom panel). We compare results of EPOS calculations with the experimental data. The top panel shows that the v$_{2}$ ( p$_{T}$ ) spectra is qualitatively described up to p$_{T}$ ≈ 1 GeV/c , the range where almost all particles are located. Nevertheless, after integration over p$_{T}$ , bottom panel, we see differences of v$_{2}$ of the order of 10% between theory and experiment, although v$_{2}$ of π ’s and of charged particles should be very similar. This is due to the extrapolation of the experimentally measured curve toward p$_{T}$ → 0, necessary to determine a p$_{T}$ integrated v$_{2}$ value. 

Summarizing, the centrality dependence of all observ- ables for identified particles, their multiplicity, their av- erage transverse momentum and their elliptical flow, as well as the elliptical flow of charged hadrons can be quan- titatively described from SPS to RHIC energies in the very simple core - corona model. It would be interesting to compare these results in detail with the predictions of (viscous) hydrodynamical calculations, the alternative approach to describe non central heavy ion collisions. 

