Physics and Astronomy
Journal or Book Title
Physical Review Letters
The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (\y\ < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.
American Physical Society
Adare, Andrew; Belikov, Sergey; Constantin, Paul; Grau, Nathan C.; Hill, John C.; Lajoie, John G.; Lebedev, Alexandre; Ogilvie, Craig; Pei, H.; Rak, Jan; Rosati, Marzia; Skutnik, S.; Vale, Carla; et al.; and PHENIX Collaboration, "Energy loss and flow of heavy quarks in Au+Au collisions at root s(NN) = 200 GeV" (2007). Physics and Astronomy Publications. 326.