Azimuthal anisotropy of D meson production in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV

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2.76 TeV
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The production of the prompt charm mesons $\Dzero$, $\Dplus$ and $\Dstar$ 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 meson decays were reconstructed at central rapidity ($|y|<0.8$) in the transverse momentum ($\pt$) 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 $\RAA$ in the direction of the reaction plane and orthogonal to it.
A positive $v_2$ is observed in mid-central collisions, with a value of about 0.2 in the interval $2<\pt<6$ GeV/$c$,
which decreases towards more central collisions.
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. The models that include substantial elastic interactions with
an expanding medium provide in general a good description of the observed anisotropy.