Transverse momentum distributions and their forward- backward   correlations in the percolating colour string approach
  The forward-backward correlations in the $p_T$ distributions, which present a clear signature of non-linear effects in particle production, are studied in the model of percolating colour strings. Quantitative predictions are given for these correlations at SPS, RHIC and LHC energies. Interaction of strings also naturally explains the flattening of $p_T$ distributions and increase of $<p_T>$ with energy and atomic number for nuclear collisions 
M.A.Braun and C.Pajares