  Color flux tubes (quark-gluon strings), formed at early stages of
hadron-hadron collisions, may overlap in case of sufficiently high densities
and interact, producing long-range azimuthal correlations. In the hypothesis of
repulsive interaction, each string may acquire, before the hadronization, the
additional transverse boost, which is an efficient sum of all accounted
string-string interactions. This modifies transverse momenta to the particles
formed in string decay, leading to modification of event-wise observables, like
azimuthal asymmetry of two-particle correlations, over a wide range of
rapidity.
  In this article we discuss results of Monte Carlo model with string
repulsion, where efficient string-string interaction radius is introduced. We
show that the effect of string repulsion can be the main dynamic origin of the
elliptic flow and of the higher harmonics, which are reflected in the
complicated structures observed in two-particle long-range correlation topology
in nucleus-nucleus collisions at RHIC and at LHC.
