Measurement of the (anti-)$^{3}$He elliptic flow in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV

The elliptic flow ( v2 ) of (anti-) 3 He is measured in Pb–Pb collisions at sNN=5.02TeV in the transverse-momentum ( pT ) range of 2–6 GeV/ c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low pT , as expected from relativistic hydrodynamics. The violation of the scaling of v2 with the number of constituent quarks at low pT , already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-) 3 He. The elliptic flow of (anti-) 3 He is underestimated by the Blast-Wave model and overestimated by a simple coalescence approach based on nucleon scaling. The elliptic flow of (anti-) 3 He measured in the centrality classes 0–20% and 20–40% is well described by a more sophisticated coalescence model where the phase-space distributions of protons and neutrons are generated using the iEBE-VISHNU hybrid model with AMPT initial conditions.