$D$-Meson Azimuthal Anisotropy in Midcentral Pb-Pb Collisions at ${\sqrt{s}}_{\mathit{N}N}=5.02\mathrm{TeV}$

The azimuthal anisotropy coefficient $v_2$ of prompt $D^0$, $D^{+}$, $D^{*+}$, and $D_s^{+}$ mesons was measured in midcentral (30%–50% centrality class) Pb-Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{s_{NN}}=5.02\mathrm{TeV}$, with the ALICE detector at the LHC. The $D$ mesons were reconstructed via their hadronic decays at midrapidity, $|y|<0.8$, in the transverse momentum interval $1<p_T<24\mathrm{GeV}/c$. The measured $D$-meson $v_2$ has similar values as that of charged pions. The $D_s^{+}$ $v_2$, measured for the first time, is found to be compatible with that of nonstrange $D$ mesons. The measurements are compared with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium and have the potential to constrain medium parameters.

Figure 1

Elliptic flow coefficient as a function of $p_T$ for prompt $D^0$, $D^{+}$, $D^{*+}$, and $D_s^{+}$ mesons and their charge conjugates for Pb-Pb collisions in the centrality class 30%–50%. The bottom panel also shows the average $v_2$ of $D^0$, $D^{+}$, and $D^{*+}$. Vertical bars represent the statistical uncertainty, and empty boxes the systematic uncertainty associated with the $D$-meson anisotropy measurement and the event-plane resolution. Shaded boxes show the feed-down uncertainty.

Figure 2

Average of $D^0$, $D^{+}$, and $D^{*+}$ $v_2$ as a function of $p_T$ at $\sqrt{s_{NN}}=5.02\mathrm{TeV}$, compared with the same measurement at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$ [33] and to the ${\pi }^{\pm }$ $v_2$ measured with the EP method [63, 64] and with the scalar production (SP) method [65].

Figure 3

Average of $D^0$, $D^{+}$, and $D^{*+}$ $v_2$ as a function of $p_T$, compared with model calculations [38, 42, 43, 44, 45, 46].