Correlation of transverse momentum and multiplicity in a superposition   model of nucleus-nucleus collisions
  In p-p collisions the average transverse momentum is known to be correlated with the multiplicity of produced particles. The correlation is shown to survive in a superposition model of nucleus-nucleus collisions. When properly parameterized, the correlation strength appears to be independent of the collision centrality - it is the same in p-p and central A-A collisions. However, the correlation is strongly suppressed by the centrality fluctuations. 
Stanislaw Mrowczynski