Energy loss and flow of heavy quarks in Au+Au collisions at sNN=200GeV

TLDR: 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 as mentioned in this paper.

Abstract: 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.

Figures

FIG. 3 (color online). (a) RAA of heavy-flavor electrons in 0%–10% central collisions compared with 0 data [6] and model calculations (curves I [30], II [31], and III [32]). The box at RAA 1 shows the uncertainty in TAA. (b) vHF2 of heavyflavor electrons in minimum bias collisions compared with 0 data [29] and the same models. Errors are shown as in Fig. 2.

FIG. 1 (color online). Invariant yields of electrons from heavyflavor decays for different Au Au centrality classes and for p p collisions, scaled by powers of 10 for clarity. The solid lines are the result of a FONLL calculation normalized to the p p data [18] and scaled with hTAAi for each Au Au centrality class. The inset shows the ratio of heavy-flavor to background electrons for minimum bias Au Au collisions. Error bars (boxes) depict statistical (systematic) uncertainties.