Power-law behavior observed in $p_{T}$-distributions and its   implications in relativistic heavy-ion collisions
  Preconception-free analyses of the inclusive invariant transverse-momentum distribution data taken from the measurements of Au+Au collisions at $\sqrt{s_{NN}}=130$ GeV and $\sqrt{s_{NN}}=200$ GeV have been performed. It is observed that the distributions exhibit for $p_{T}\geq 2$ GeV/c remarkably good power-law behavior ($p_{T}$-scaling) with general regularities. This power-law behavior leads us in particular to recognize that the concept of centrality, albeit its simple appearance, is rather complex; its underlying geometrical structure has to be understood in terms of fractal dimensions. Experimental evidences and theoretical arguments are given which show that the observed striking features are mainly due to geometry and self-organized criticality. A simple model is proposed which approximately reproduces the above-mentioned data for the ``suppression'' without any adjustable parameter. Further heavy-ion collision experiments are suggested. 
Meng Ta-chung, Liu Qin