Azimuthal anisotropy of D-meson production in Pb-Pb collisions at √sNN =2.76 TeV

Abelev, B. and Adam, J. and Adamová, D. and Aggarwal, M. M. and Agnello, M. and Agostinelli, A. and Agrawal, N. and Ahammed, Z. and Ahmad, N. and Ahmed, I. and Ahn, S. U. and Ahn, S. A. and Aimo, I. and Aiola, S. and Ajaz, M. and Akindinov, A. and Alam, S. N. and Aleksandrov, D. and Alessandro, B. and Alexandre, D. and Alici, A. and Alkin, A. and Alme, J. and Alt, T. and Altinpinar, S. and Altsybeev, I. and Alves, Garcia Prado C. and Andrei, C. and Andronic, A. and Anguelov, V. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Molnár, Levente and Oláh, László and Pochybova, Sona (2014) Azimuthal anisotropy of D-meson production in Pb-Pb collisions at √sNN =2.76 TeV. PHYSICAL REVIEW C, 90 (3). ISSN 2469-9985

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Abstract

The production of the prompt charmed mesons D 0 , D + and D ∗ + relative to the reaction plane was measured in Pb–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision of √sNN = 2.76 TeV with the ALICE detector at the LHC. D mesons were reconstructed via their hadronic decays at central rapidity in the transverse momentum (p T) interval 2–16 GeV / c. The azimuthal anisotropy is quantified in terms of the second coefficient v 2 in a Fourier expansion of the D meson azimuthal distribution, and in terms of the nuclear modification factor RAA, measured in the direction of the reaction plane and orthogonal to it. The v 2 coefficient was measured with three different methods and in three centrality classes in the interval 0–50%. A positive v 2 is observed in mid-central collisions (30–50% centrality class), with an mean value of 0 .204 + 0 .099 − 0 .036 (tot. unc.) in the interval 2 < p T < 6 GeV / c, which decreases towards more central collisions (10–30% and 0– 10% classes). The positive v 2 is also reflected in the nuclear modification factor, which shows a stronger suppression in the direction orthogonal to the reaction plane for mid-central collisions. The measurements are compared to theoretical calculations of charm quark transport and energy loss in high-density strongly-interacting matter at high temperature. The models that include substantial elastic interactions with an expanding medium provide a good description of the observed anisotropy. However, they are challenged to simultaneously describe the strong suppression of highp T yield of D mesons in central collisions and their azimuthal anisotropy in non-central collisions.

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