Modified Glauber Model and a new interpretation of collective effects in AA and pA at LHC

The Monte Carlo version of the Modified Glauber Model (MGM) [1] is updated and applied to the analysis of the total multiplicity yields of charged particles in mucleus-nucleus and proton-nucleus collisions in a broad energy range. The MGM takes into account the energy conservation and momentum loss for particle production in each nucleon-nucleon inelastic collision. This is done by introducing a mean fraction of the initial nucleon momentum which is allowed to be lost in each inelastic interaction between nucleons of colliding nuclei. Therefore, the next nucleon-nucleon inelastic collision takes place at a lower energy root s and with the relevant cross-section sigma(inel)(root s). Comparison of the MGM calculations to the available experimental data on mean total multiplicity <N-ch> in central nucleus-nucleus collisions from AGS to RHIC energies allows to fit a single model parameter k = 0.35. The same value of k is found to be valid for successful description of the scaling of <N-ch>/2N(part) with the number of nucleon-participants N-part in Pb-Pb collisions observed in ALICE at the LHC [2]. A considerable reduction of N-coll is obtained in MGM for the case of nucleus-nucleus collisions at the LHC energy in comparison with the standard Glauber approach, while the number of participants N-part is practically unchanged. In the MGM approach the nucleon stopping phenomenon is observed, that has dramatic effect in case of proton-nucleus collisions. The MGM predicts considerable decrease (by a factor of about 3 for central collisions in comparison with the standard Glauber-based estimates) of the number of participants <N-part>=<N-coll> + 1 in case of pA interactions at the LHC.