High-order flow harmonics of identified hadrons in $2.76A$ TeV Pb + Pb collisions

Using the iEBE-VISHNU hybrid model with AMPT initial conditions, we study the higher order flow harmonics of identified hadrons in $2.76A$ TeV Pb+Pb collisions. Comparison with the recent ALICE measurements at 20–30% centrality shows that our calculations generally describe the data below 2 GeV, especially for the $v_2, v_3$, and $v_4$ mass orderings among pions, kaons, and protons. We also extended the calculations to other centrality bins, which presents similar mass-ordering patterns for these flow harmonics as the ones observed at 20–30% centrality. In the later part of this article, we explore the development of $v_n$ mass ordering/splitting during the hadronic evolution through comparison runs from the iEBE-VISHNU hybrid model and pure hydrodynamics with different decoupling temperatures.

Figure 1

$p_T$ spectra of pions, kaons, and protons in $2.76A$ TeV Pb+Pb collisions at $10–20\%, 20–30\%, 30–40\%$, and $40–50\%$ centralities. The experimental data are taken from the ALICE paper [65], and the theoretical curves are calculated from iEBE-VISHNU with AMPT initial conditions.

Figure 2

$v_n\left(p_T\right)$ ($n=2,3,4$) of pions, kaons, and protons in $2.76A$ TeV Pb+Pb collisions at $10–20\%, 20–30\%, 30–40\%$, and $40–50\%$ centralities. The experimental data are from ALICE [41, 46], and the theoretical curves are calculated from iEBE-VISHNU with AMPT initial conditions.

Figure 3

$p_T$ spectra of pions, kaons, and protons in $2.76A$ TeV Pb+Pb the $20–30\%$ centrality, calculated from iEBE-VISHNU and from VISH2+1 with $T_{\mathrm{dec}}=165\mathrm{MeV}$ and $T_{\mathrm{dec}}=120\mathrm{MeV}$.

Figure 4

$v_n\left(p_T\right)$ ($n=2,3,4$) of pions, kaons, and protons in $2.76A$ TeV Pb+Pb collisions at $20–30\%$ centrality. The left, middle and right panels show comparisons between different model calculations with the same AMPT initial conditions and $\eta /s$: (a) VISH2+1 with $T_{\mathrm{dec}}=165\mathrm{MeV}$ vs VISHNU; (b) VISH2+1 with $T_{\mathrm{dec}}=120\mathrm{MeV}$ vs VISHNU; (c) VISH2+1 with $T_{\mathrm{dec}}=165\mathrm{MeV}$ vs VISH2+1 with $T_{\mathrm{dec}}=120\mathrm{MeV}$.