Model of pp and AA collisions for the description of long-range correlations

TL;DR

This paper presents a phenomenological model for soft processes in pp and AA collisions, focusing on long-range correlations, string fusion, and impact parameter effects, without relying on the Glauber model.

Contribution

It introduces a novel approach to describe AA interactions through color string fusion and impact parameter lattice, bypassing the traditional Glauber model framework.

Findings

Successfully describes long-range correlations in pp and AA collisions

Predicts multiplicity and transverse momentum fluctuations consistent with experimental data

Analyzes the impact of centrality determination methods on correlation measurements

Abstract

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.