Model of pp and AA collisions for the description of long-range correlations
Soft processes in pp and AA interactions are considered in the framework of phenomenological model with color strings formation and fusion. Elementary parton collisions are realized in the model as the interaction of two colour dipoles from projectile and target nucleons. Modeling of the exclusive distributions of parton momentum fractions and transverse coordinates is performed. The interaction of colour strings in transverse plane is carried out in the framework of local string fusion model with the introduction of the lattice in the impact parameter plane and taking into account the finite rapidity length of strings. The parameters were fixed with experimental data on pp total inelastic cross section and charged multiplicity. The model was used for the calculation of long-range correlations between the multiplicities (n) and the mean transverse momenta (pt) of charged particles. The dependence of n-n, pt-n, pt-pt correlations on the width and position of the backward and forward rapidity windows was studied. Note that the model enables to describe the AA interactions without referring to the Glauber picture based on the concept of elementary nucleon-nucleon collisions. In this connection the charged multiplicity, the mean numbers of participant nucleons and binary collisions and their variances in the case of PbPb collisions were calculated and compared with the predictions of alternative models and the experimental data. The influence of different ways of centrality determination on the multiplicity fluctuations and long-range correlations was also discussed.