Elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity in Pb–Pb collisions at \(\sqrt{s_{\rm NN}}= 2.76\) TeV

Abstract

The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity \(|y| < 0.7\) is measured in Pb–Pb collisions at \(\sqrt{s_{\rm NN}}= 2.76\) TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient \(v_2\) represents the elliptic flow. The \(v_2\) coefficient of inclusive electrons is measured in three centrality classes (0–10%, 10–20% and 20–40%) with the event plane and the scalar product methods in the transverse momentum \(p_{\rm T}\) intervals 0.5-13 GeV/\).\) and 0.5-8 GeV/\).\). respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive \(v_2\) of electrons from heavy-flavour hadron decays is observed in all centrality classes, with a maximum significance of \(5.9\sigma\) in the interval \(2 < p_{\rm T} < 2.5\) GeV/\).\) in semicentral collisions (20–40%). The value of \(v_2\) decreases towards more central collisions at low and intermediate \(p_{\rm T}\) \(0.5 < p_{\rm T} < 3\) GeV/\).\) . The \(v_2\) of electrons from heavy-flavour hadron decays at mid-rapidity is found to be similar to the one of muons from heavy-flavour hadron decays at forward rapidity \(2.5 < y < 4\) . The results are described within uncertainties by model calculations including substantial elastic interactions of heavy quarks with an expanding strongly-interacting medium.