Measurements of mixed harmonic cumulants in Pb-Pb collisions at $\mathbf{\sqrt{{\textit s}_{\rm NN}}}=5.02$ TeV

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Correlations between moments of different flow coefficients are measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded with the ALICE detector. These new measurements are based on multiparticle mixed harmonic cumulants calculated using charged particles in the pseudorapidity region $|\eta|<~0.8$ with the transverse momentum range $0.2 <~ p_{\rm T} <~ 5.0$ GeV/$c$. The centrality dependence of correlations between two flow coefficients as well as the correlations between three flow coefficients, both in terms of their second moments, are shown. In addition, a collection of mixed harmonic cumulants involving higher moments of $v_2$ and $v_3$ is measured for the first time, where the characteristic signature of negative, positive and negative signs of four-, six- and eight-particle cumulants are observed, respectively. The measurements are compared to the hydrodynamic calculations using iEBE-VISHNU with AMPT and TRENTo initial conditions. It is shown that the measurements carried out using the LHC Run 2 data in 2015 have the precision to explore the details of initial-state fluctuations and probe the nonlinear hydrodynamic response of $v_2$ and $v_3$ to their corresponding initial anisotropy coefficients $\varepsilon_2$ and $\varepsilon_3$. These new studies on correlations between three flow coefficients as well as correlations between higher moments of two different flow coefficients will pave the way to tighten constraints on initial-state models and help to extract precise information on the dynamic evolution of the hot and dense matter created in heavy-ion collisions at the LHC.

 

Submitted to: PLB
e-Print: arXiv:2102.12180 | PDF | inSPIRE

Figure 1

< p>Centrality dependence of $nMHC(v_{2}^{2}, v_{3}^{2})$, $nMHC(v_{2}^{2}, v_{4}^{2})$, $nMHC(v_{3}^{2}, v_{4}^{2})$ and $nMHC(v_{2}^{2}, v_{3}^{2}, v_{4}^{2})$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV, shown by the solid markers. The statistical (systematic) errors are shown with vertical bars (filled boxes). Comparisons to the previous measurements at 2.76 TeV from Refs.~, shown by the open markers, are also presented. Data points are shifted for visibility.< /p>

Figure 2

< p>Centrality dependence of $nMHC(v_{2}^{2}, v_{3}^{2})$ and $nMHC(v_{2}^{2}, v_{4}^{2})$ in \PbPb\ collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV (solid markers) and 2.76 TeV (open markers). Statistical uncertainties are shown as vertical bars and systematic uncertainties as filled boxes. The iEBE-VISHNU calculations~ for Pb--Pb collisions at 5.02 TeV with TRENTo initial conditions (red shadowed bands) and AMPT initial conditions (blue shadowed bands) are presented, together with the corresponding initial state calculations $nMHC(\varepsilon_{2}^{2}, \varepsilon_{3}^{2})$, $nMHC(\varepsilon_{2}^{2}, \varepsilon_{4}^{2})$ from the TRENTo (red dot-dash lines) and AMPT model (blue long-dash lines). The same marker (line) styles and colors are used in later figures. Data points are shifted for visibility.< /p>

Figure 3

< p>Centrality dependence of $nMHC(v_{3}^{2}, v_{4}^{2})$ and $nMHC(v_{2}^{2}, v_{3}^{2}, v_{4}^{2})$ in \PbPb\ collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV (solid markers) and 2.76 TeV (open markers). Statistical uncertainties are shown as vertical bars and systematic uncertainties as filled boxes. Data points are shifted for visibility.< /p>

Figure 4

< p>Centrality dependence of $nMHC$ for \PbPb\ collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV. Statistical uncertainties are shown as vertical bars and systematic uncertainties as filled boxes. Data points are shifted for visibility.< /p>

Figure 5

< p>Centrality dependence of $nMHC(v_{2}^{4}, v_{3}^{2})$ and $nMHC(v_{2}^{2}, v_{3}^{4})$ in \PbPb\ collision at $\sqrt{s_{\rm NN}} = 5.02$~TeV. Statistical uncertainties are shown as vertical bars and systematic uncertainties as filled boxes. < /p>

Figure 7

< p>Centrality dependence of $nMHC(v_{2}^{2}, v_{3}^{6})$ in \PbPb\ collisions at $\sqrt{s_{\rm NN}} = 5.02$~TeV. Statistical uncertainties are shown as vertical bars and systematic uncertainties as filled boxes. < /p>