Initial eccentricity and constituent quark number scaling of elliptic flow in ideal and viscous dynamics

Understand

In the Israel-Stewart's theory of dissipative hydrodynamics, we study the scaling properties elliptic flow in Au+Au collisions.

• Initial energy density of the fluid was fixed to reproduce STAR data on $\phi$ meson multiplicity in 0-5% Au+Au collisions, such that irrespective of fluid viscosity, entropy at the freeze-out is similar in ideal or in viscous evolution.
• Initial eccentricity or constituent quark number scaling is only approximate in ideal or minimally viscous ($\eta/s=1/4\pi$) fluid.
• Eccentricity scaling become nearly exact in more viscous fluid ($\eta/s \geq$0.12).