  The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has
measured electrons from heavy flavor (charm and bottom) decays for 0.3 < p_T <
9 GeV/c at midrapidity (|y| < 0.35) in Au+Au collisions at sqrt(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. A large azimuthal
anisotropy, v_2, with respect to the reaction plane is observed for 0.5 < p_T <
5 GeV/c indicating non-zero 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.
