engleski

Evolution of the differential transverse momentum correlation function with centrality in Au + Au collisions at $\sqrt{; ; ; ; s_{; ; ; ; NN}; ; ; ; }; ; ; ; $=200 GeV

We present first measurements of the evolution of the differential transverse momentum correlation function, C, with collision centrality in Au + Au interactions at $\sqrt{; ; ; ; s}; ; ; ; $=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.

azimuthal correlations; QGP; heavy ion collisions

STAR Collaboration