We present two independent estimates of the number of nucleon-nucleon collisions (N coll ) and the number of participant nucleons (N part ) in AA and pA interactions at the LHC energies, obtained using Monte Carlo calculations: the Modified Glauber model (MGM) and more detailed "non-Glauber Model", based on the color dipoles approach. Contrary to generally used standard Glauber model, the MGM takes into account in an effective way the energymomentum conservation in soft particles production.

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... s it provides with only one parameter the quantitative description of scaling of the charged particle yields with N part , describing observed in experiment in a wide energy region from SPS to LHC. The second model provides parton-string description of pp, pA and AA interaction considering the energy conservation in nucleon-nucleon collisions and string interaction (string fusion). These estimates are confirmed by calculations using the MC event generators (AMPT and HIJING). The results are pointing at the effect of noticeable stopping of nucleons in pA and AA collisions. Taking into account the obtained considerable decrease of N coll and N part in pA collisions, compared to Glauber values, we suggest reconsidering the use of Glauber normalization in determination of charged-particles pseudorapidity densities in p-Pb collisions at LHC energies.