Non-linear flow modes of identified particles in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with the ALICE detector

Abstract

The non-linear flow modes, $v_{4,22}$, $v_{5,32}$ and $v_{6,33}$ as a function of transverse momentum ($p_{\mathrm{T}}$) have been measured for the first time in Pb--Pb collisions at $\sqrt{s_{\rm{NN}}} = 5.02$ TeV for identified particles, i.e. charged pions, kaons and (anti-)protons. These observables probe the contribution of the second and third initial anisotropy coefficients to the higher order flow harmonics. Interestingly, all the characteristic features observed in previous $p_{\mathrm{T}}$-differential as well as $p_{\mathrm{T}}$-integrated measurements (e.g. $v_{2}$ and $v_{3}$) for various particle species are present in these measurements, i.e. increase of magnitude with increasing centrality percentile, a mass ordering in the low $p_{\mathrm{T}}$ region and a particle type grouping in the intermediate $p_{\mathrm{T}}$ region. The results cover 0--1\% (ultra-central collisions), 10--20\% (mid-central collisions) and 40--50\% (mid-peripheral collisions) centrality intervals and allow to test models that attempt to describe initial conditions and the mode-coupling of different harmonics.