Temperature-independent shear viscosity in a multiphase transport model for relativistic heavy ion collisions

Using a multiphase transport (AMPT) model, we study the dependence on the specific shear viscosity of the transverse momentum spectra, Hanbury Brown–Twiss parameters, and elliptic flow with a temperature-independent shear viscous approach. The shear viscosity strengthens the transverse pressure gradients, raises the transverse momentum spectra, and gives smaller values of $R_{\mathrm{o}}$, $R_{\mathrm{l}}$, and $R_{\mathrm{o}}/R_{\mathrm{s}}$, but increases value of $R_{\mathrm{s}}$. The transverse momentum dependence of $v_2$ is suppressed with increasing $\eta /s$ and can hold at finite $\eta /s$ within a partonic cascade approach in the AMPT model.

Figure 1

Partonic energy density distribution in $z\text{−}x$ plane for Au+Au central collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$ in the AMPT model: (a)–(d) correspond to $t=0.5,1.0,2.0,5.0\mathrm{fm}/c$.

Figure 2

Same as Fig. 1 but in $x\text{−}y$ plane.

Figure 3

Proper time evolution of shear viscosity to entropy density ratio for partonic phase.

Figure 4

The transverse momentum spectra of midrapidity pions for Au+Au central collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. PHENIX data from Ref. [34].

Figure 5

Two-pion HBT radii $R_{\mathrm{o}}$, $R_{\mathrm{s}}$, $R_{\mathrm{l}}$ and the ratio $R_{\mathrm{o}}/R_{\mathrm{s}}$ for Au+Au central collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. STAR data from Ref. [37].

Figure 6

The dependence of the differential elliptic flow $v_2$ on $\eta /s$ for charged pions obtained in minimum-bias Au+Au collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. PHENIX data from Ref. [38].