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Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at ffiffiffiffiffiffiffiffi s NN p ¼ 2:76 TeV. Two-and three-particle charge-dependent azimuthal correlations in the pseudorapidity range j j < 0:8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a chargedependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.

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The production of the prompt charm mesons D 0 , D + , D * + , and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the LHC, at a centre-of-mass energy √ s NN = 2.76 TeV per nucleon-nucleon collision. The p t -differential production yields in the range 2 < p t < 16 GeV/c at central rapidity, |y| < 0.5, were used to calculate the nuclear modification factor R AA with respect to a proton-proton reference obtained from the cross section measured at √ s = 7 TeV and scaled to √ s = 2.76 TeV. For the three meson species, R AA shows a suppression by a factor 3-4, for transverse momenta larger than 5 GeV/c in the 20% most central collisions. The suppression is reduced for peripheral collisions. The ALICE Collaboration 29 Keywords: Heavy Ions IntroductionA high-density colour-deconfined state of strongly-interacting matter is expected to be formed in high-energy collisions of heavy nuclei. According to calculations of Quantum Chromodynamics (QCD) on the lattice, under the conditions of high energy density and temperature reached in these collisions, a phase transition to a Quark-Gluon Plasma (QGP) occurs. In such conditions, the confinement of quarks and gluons into hadrons vanishes, and chiral symmetry is restored (see e.g. [1][2][3][4]). Heavy-flavour hadrons, containing charm and beauty, are effective probes of the conditions of the medium formed in nucleus-nucleus collisions at high energy. Hard partons, including gluons, light-flavour quarks, and heavy quarks, are produced at the initial stage of the collision in high-virtuality scattering processes. They interact with the medium, and are expected to be sensitive to its energy density, through the mechanism of parton energy loss. This QCD energy loss is expected to occur via both inelastic (medium-induced gluon radiation, or radiative energy loss) [5,6] and elastic (collisional energy loss) [7][8][9] processes. In QCD, quarks have a smaller colour coupling factor with respect to gluons, so that the energy loss for quarks is expected to be smaller than for gluons. In addition, the 'dead-cone effect' should reduce small-angle gluon radiation for heavy quarks with moderate energy-over-mass values [10][11][12][13][14], thus further attenuating the effect of the medium. Instead, other mechanisms, such as in-medium hadron -1 -