Survival rate of initial azimuthal anisotropy in a multiphase transport model

We investigate the survival rate of an initial momentum anisotropy $\left(v_2^{\mathrm{ini}}\right)$, not spatial anisotropy, to the final state in a multiphase transport (AMPT) model in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV. It is found that both the final-state parton and charged hadron $v_2$ show a linear dependence versus $v_2^{\mathrm{ini}}\left\{\mathrm{PP}\right\}$ with respect to the participant plane (PP). It is found that the slope of this linear dependence (referred to as the survival rate) increases with transverse momentum $p_T$, reaching $\sim 100\%$ at $p_T\sim 2.5$ GeV/$c$ for both parton and charged hadron. The survival rate decreases with collision centrality and energy, indicating decreasing survival rate with increasing interactions. It is further found that a $v_2^{\mathrm{ini}}\left\{\mathrm{Rnd}\right\}$ with respect to a random direction does not survive in $v_2\left\{\mathrm{PP}\right\}$ but in the two-particle cumulant $v_2\left\{2\right\}$. The dependence of $v_2\left\{2\right\}$ on $v_2^{\mathrm{ini}}\left\{\mathrm{Rnd}\right\}$ is quadratic rather than linear.

Figure 1

Midrapidity $\left(\left|\eta \right|<1\right)$ hadrons $v_2\left\{\mathrm{PP}\right\}$ vs $p_T$ with $v_2^{\mathrm{ini}}\left\{\mathrm{PP}\right\}=0\%$ and $v_2^{\mathrm{ini}}\left\{\mathrm{PP}\right\}=8\%$ for $b=8$ fm Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by AMPT (string melting).

Figure 2

Midrapidity $\left(\left|\eta \right|<1\right)$ final-state partons and hadrons $v_2\left\{\mathrm{PP}\right\}$ at $1.5<p_T<2$ GeV/$c$ vs $v_2^{\mathrm{ini}}\left\{\mathrm{PP}\right\}$ for $b=8$ fm Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by AMPT (string melting).

Figure 3

Survival rate of initial momentum anisotropy to final-state partons and charged hadrons at midrapidity $\left(|\eta <1|\right)$ as a function of $p_T$ for $b=8$ fm Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by AMPT (string melting).

Figure 4

Survival rate as a function of (a) collision energy and (b) impact parameter for midrapidity $\left(\left|\eta \right|<1\right)$ final-state partons and charged hadrons in $0<p_T<2$ GeV/$c$ for Au+Au collisions by AMPT (string melting).

Figure 5

Midrapidity $\left(\left|\eta \right|<1\right)$ hadrons (a) $v_2\left\{\mathrm{PP}\right\}$ and (b) $v_2\left\{2\right\}$ vs $p_T$ with $v_2^{\mathrm{ini}}\left\{\text{Rnd}\right\}=0\%$, 8%, and 20% for $b=8$ fm Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by AMPT (string melting).

Figure 6

Midrapidity $\left(\left|\eta \right|<1\right)$ hadrons $v_2\left\{2\right\}$ and $v_2\left\{\mathrm{PP}\right\}$ vs $v_2^{\mathrm{ini}}\left\{\text{Rnd}\right\}$ for $b=8$ fm Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by AMPT (string melting). The solid lines are fitting results. The dashed lines are horizontal and through the point of $v_2^{\mathrm{ini}}\left\{\text{Rnd}\right\}=0$.