Saturation of elliptic flow and shear viscosity

Abstract

Effect of shear viscosity on elliptic flow is studied in causal dissipative hydrodynamics in 2+1 dimensions. Elliptic flow is reduced in viscous dynamics. Causal evolution of minimally viscous fluid ($η/s$=0.08), can explain the PHENIX data on elliptic flow in 16-23% Au+Au collisions up to $p_T\approx$3.6 GeV. In contrast, ideal hydrodynamics, can explain the same data only up to $p_T\approx$1.5 GeV. $p_T$ spectra of identified particles are also better explained in minimally viscous fluid than in ideal dynamics. However, saturation of elliptic flow at large $p_T$ is not reproduced.

Figures (4)

• Figure 1: (color online) constant energy density contours in b=0 Au+Au collisions after 8 fm of evolution.
• Figure 2: (color online) The solid and dashed lines show the $p_T$ dependence of elliptic flow in evolution with integration step lengths $dx=dy=0.2,d\tau=0.02$ and $dx=dy=0.1,d\tau=0.01$. The black lines corresponds to ideal fluid. The red and blue lines corresponds to viscous fluid with $\eta/s$=0.04 and with $\eta/s$=0.08 respectively. The filled circles are PHENIX data Adler:2004cj on elliptic flow of charged particles in 16-23% Au+Au collisions.
• Figure 3: $p_T$ dependence of elliptic flow in ideal (the black lines) and in minimal viscous (the blue lines) dynamics for $T_F$=130,140,150 and 160 MeV in a b=6.5 fm Au+Au collision. The filled circles are the PHENIX data Adler:2004cj on the elliptic flow in 16-23% Au+Au collisions.
• Figure 4: PHENIX data Adler:2003cb on the transverse momentum dependence $\pi^-$, $K^+$ and proton in 0-5% Au+Au collisions are shown. The blue and black lines are predictions from minimally viscous hydrodynamics and from ideal hydrodynamics in a b=2.3 fm Au+Au collision.