Tilted plateau in nuclear collisions: data, models and MC-s
  The linear dependence of the particle spectra on rapidity is seen in the central region for asymmetric heavy ion collision in the data and in the Monte Carlo results, similarly as in the fragmentation region for hadronic and ion collisions. The origin of such a behaviour is discussed. It is shown that the color string models produce naturally such a shape if string ends are randomly distributed in rapidity. 
K. Fialkowski, R. Wit