  We demonstrate that the investigations of the forward-backward correlations
between intensive observables enable to obtain more clear signal about the
initial stage of hadronic interaction, e.g. about the process of string fusion,
compared to usual forward-backward multiplicity correlations. As an example,
the correlation between mean-event transverse momenta of charged particles in
separated rapidity intervals is considered. We performed calculations in the
framework of dipole-based Monte Carlo string fusion model. We obtained the
dependence of the correlation strength on the collision centrality for
different initial energies and colliding systems. It is shown that the
dependence reveals the decline of the correlation coefficient for most central
Pb-Pb collisions at LHC energy. We compare the results both with the ones
obtained in alternative models and with the ones obtained by us using various
MC generators.
