Elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity in Pb-Pb collisions at $\mathbf{\sqrt{s_\mathrm{NN}}}$ = 2.76 TeV

J. Adam , Laurent Aphecetche (1) , B. Audurier (1) , A. Baldisseri (2) , Guillaume Batigne (1) , I. Belikov (3) , H. Borel (2) , J. Castillo Castellanos (2) , J.L. Charvet (2) , C. Cheshkov (4) , B. Cheynis (4) , L. Ducroux (4) , B. Erazmus (1) , Magali Estienne (1) , V.J.G. Feuillard (2, 5) , A. Francisco (1) , Marie Germain (1) , J.C. Hamon (3) , B. Hippolyte (3) , C. Kuhn (3) , A. Lardeux (2) , Gines Martinez Garcia (1) , L. Molnar (3) , A. Morreale (1) , H. Pereira Da Costa (2) , Philippe Pillot (1) , A. Rakotozafindrabe (2) , F. Rami (3) , L. Ronflette (1) , C. Roy (3) , Alexandre Shabetai (1) , Diego Stocco (1) , B. Teyssier (4) , R. Tieulent (4) , A. Uras (4) , R. Verney (6) , V. Barret (5) , N. Bastid (5) , A. Batista Camejo (5) , P. Crochet (5) , P. Dupieux (5) , S. Li (5) , X. Lopez (5) , F. Manso (5) , S. Porteboeuf-Houssais (5) , P. Rosnet (5) , B. Vulpescu (5) , Z. Conesa Del Valle (7) , I. Das (7) , B. Espagnon (7) , C. Hadjidakis (7) , I. Lakomov (7) , C. Suire (7) , J. D. Tapia Takaki (7) , M. Tarhini (7) , L. Valencia Palomo (7) , G. Conesa Balbastre (8) , J. Faivre (8) , C. Furget (8) , R. Guernane (8) , C. Silvestre (8) , A. Vauthier (8)

1 SUBATECH - Laboratoire SUBATECH Nantes
2 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
3 DRS-IPHC - Département Recherches Subatomiques
4 IPNL - Institut de Physique Nucléaire de Lyon
5 LPC - Laboratoire de Physique Corpusculaire - Clermont-Ferrand
6 CC-IN2P3 - Centre de Calcul de l'IN2P3
7 IPNO - Institut de Physique Nucléaire d'Orsay
8 LPSC - Laboratoire de Physique Subatomique et de Cosmologie

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 ($v_{\rm 2}$) represents the elliptic flow. The $v_{\rm 2}$ 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/$c$ and 0.5-8 GeV/$c$, respectively. After subtracting the background, mainly from photon conversions and Dalitz decays of neutral mesons, a positive $v_{\rm 2}$ 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/$c$ in semi-central collisions (20-40%). The value of $v_{\rm 2}$ decreases towards more central collisions at low and intermediate $p_{\rm T}$ (0.5 $<$ $p_{\rm T}$ $<$ 3 GeV/$c$). The $v_{\rm 2}$ 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.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique des Hautes Energies - Expérience [hep-ex]

J. Adam, Laurent Aphecetche, B. Audurier, A. Baldisseri, Guillaume Batigne, et al.. Elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity in Pb-Pb collisions at $\mathbf{\sqrt{s_\mathrm{NN}}}$ = 2.76 TeV. Journal of High Energy Physics, 2016, 09(2016), pp.028. ⟨10.1007/JHEP09(2016)028⟩. ⟨in2p3-01325249⟩