$\rm D^0$ meson $v_2$ as a function of $\pt$ in the 30-50% centrality class, with the reference particles from the TPC or from the VZERO detectors ($-3.7< \eta< -1.7$ and $2.8< \eta< 5.1$). (a) Event plane method. (b) Scalar product method. For visibility, the symbols for the VZERO case are slightly displaced horizontally.