  We implement a Langevin approach for the transport of charm quarks in the
UrQMD (hydrodynamics + Boltzmann) hybrid model. Due to the inclusion of
event-by-event fluctuations and a full (3+1) dimensional hydrodynamic
evolution, this approach provides a more realistic model for the evolution of
the matter produced in heavy ion collisions as compared to simple homogeneous
fireball expansions usually employed. As drag and diffusion coefficients we use
a resonance approach for elastic heavy-quark scattering and assume a decoupling
temperature of the charm quarks from the hot medium of 130 MeV. A coalescence
approach at the decoupling temperature for the hadronization of the charm
quarks to D-mesons is also included. We present calculations of the nuclear
modification factor R_AA as well as the elliptic flow v_2 in Pb+Pb collisions
at sqrt s_NN=2.76 TeV. The comparison to ALICE measurements shows a very good
agreement with our calculations.
