Evolution of the differential transverse momentum correlation function with centrality in Au + Au collisions at s N N = 200 GeV
G. Agakishiev, M. M. Aggarwal, Z. Ahammed, A. V. Alakhverdyants, I. Alekseev, J. Alford, B. D. Anderson, C. D. Anson, D. Arkhipkin, G. S. Averichev, J. Balewski, D. R. Beavishttp://academic.research.microsoft.com/io.ashx?type=5&id=49359463&selfId1=0&selfId2=0&maxNumber=12&query=
We present first measurements of the evolution of the differential transverse momentum correlation function, C, with collision centrality in Au+Au interactions at sNN=200 GeV. This observable exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of C with increasing centrality to estimate the ratio of the shear viscosity to entropy density, η/s, of the matter formed in central Au+Au interactions. We obtain an upper limit estimate of η/s that suggests that the produced medium has a small viscosity per unit entropy.