Measurement of $J/\psi$ Azimuthal Anisotropy in $\mathrm{Au}\mathbf{+}\mathrm{Au}$ Collisions at $\sqrt{s_{NN}}\mathbf{=}200\mathrm{GeV}$

The measurement of $J/\psi$ azimuthal anisotropy is presented as a function of transverse momentum for different centralities in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200\mathrm{GeV}$. The measured $J/\psi$ elliptic flow is consistent with zero within errors for transverse momentum between 2 and $10\mathrm{GeV}/c$. Our measurement suggests that $J/\psi$ particles with relatively large transverse momenta are not dominantly produced by coalescence from thermalized charm quarks, when comparing to model calculations.

Figure 1

Top: $1/R$ weighted invariant mass spectrum of electron and positron pairs for $\varphi \mathrm{\text{−}}\Psi$ in $0–0.1\pi$ and $0.9\pi –\pi$, $4<p_T<6\mathrm{GeV}/c$, in 0%–80% central collisions. The points are unlike-sign pairs with the $J/\psi$ signal, fitted by a Crystal Ball plus second order polynomial function. The polynomial background component of the fit is shown by the dashed line. The solid line histogram shows the like-sign background. Bottom: $1/R$ weighted $J/\psi$ yield vs $\varphi \mathrm{\text{−}}\Psi$ with fitted $v_2$.

Figure 2

$v_2$ vs $p_T$ for $J/\psi$ particles in different centrality bins. The brackets represent systematic errors estimated from differences between different methods and cuts. The boxes show the estimated maximum possible range of $v_2$ if the nonflow influence is corrected (see text). The $p_T$ bins for $J/\psi$ particles are 0–2, 2–5, and $5–10\mathrm{GeV}/c$. The mean $p_T$ in each bin for the $J/\psi$ sample used for $v_2$ calculation is drawn, but is shifted a little for some centralities so that all points can be seen clearly.

Figure 3

$v_2$ vs $p_T$ for $J/\psi$ particles in 0%–80% central events comparing with charged hadrons [29] and the $\varphi$ meson [30] (upper panel) and theoretical calculations [31, 32, 33, 34, 35] (lower panel). The brackets represent systematic errors estimated from differences between different methods and cuts. The boxes show the estimated maximum possible range of $v_2$ if the nonflow influence is corrected. The $p_T$ bins for $J/\psi$ particles are 0–2, 2–4, 4–6, and $6–10\mathrm{GeV}/c$, and the mean $p_T$ in each bin for the $J/\psi$ sample used for $v_2$ calculation is drawn.