Transverse-momentum and event-shape dependence of D-meson flow harmonics in Pb-Pb collisions at $\sqrt{s_{NN}} = 5.02$ TeV

TL;DR

This paper measures the flow harmonics of D mesons in Pb-Pb collisions at 5.02 TeV, revealing mass hierarchy at low transverse momentum and similar behavior to pions at higher momentum, providing insights into charm quark interactions in the quark-gluon plasma.

Contribution

It presents the first detailed measurement of D-meson flow harmonics across a wide transverse momentum range in Pb-Pb collisions at 5.02 TeV, exploring charm quark coupling to the medium with event-shape engineering.

Findings

D-meson flow harmonics show mass hierarchy below 3 GeV/c

D-meson flow harmonics are similar to pions at high pT

D-meson yields are consistent across event-shape selections

Abstract

The elliptic and triangular flow coefficients $v_2$ and $v_3$ of prompt D$^{0}$, D$^{+}$, and D$^{*+}$ mesons were measured at midrapidity ($|y|<0.8$) in Pb-Pb collisions at the centre-of-mass energy per nucleon pair of $\sqrt{s_{NN}} = 5.02$ TeV with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays in the transverse momentum interval $1< p_{\rm T}<36$ GeV/$c$ in central (0-10%) and semi-central (30-50%) collisions. Compared to pions, protons, and J/$\psi$ mesons, the average D-meson $v_{n}$ harmonics are compatible within uncertainties with a mass hierarchy for $p_{\rm T} \lesssim 3$ GeV/$c$, and are similar to those of charged pions for higher $p_{\rm T}$. The coupling of the charm quark to the light quarks in the underlying medium is further investigated with the application of the event-shape engineering (ESE) technique to the D-meson $v_2$ and $p_{\rm T}$-differential yields. The D-meson $v_2$ is correlated with average bulk elliptic flow in both central and semi-central collisions. Within the current precision, the ratios of per-event D-meson yields in the ESE-selected and unbiased samples are found to be compatible with unity. All the measurements are found to be reasonably well described by theoretical calculations including the effects of charm-quark transport and the recombination of charm quarks with light quarks in a hydrodynamically expanding medium.