  An improved measurement of $v_2$ for $\pi^0$ in a broad range of $p_T$ and
centrality is presented. By combining $v_2$ with the $R_{AA}$, we provide new
insights on jet-medium interactions. We show that current pQCD energy loss
models cannot describe the suppression of the $\pi^0$ as a function of the
angle with respect to the reaction plane. Our result could help to resolve the
factor of 4 differences in the predicted transport coefficients among these
models. Alternatively, it may suggest that non-perturbative effects associated
with the strongly coupled QGP are important, and new theoretical developments
are needed to fully understand the jet medium interactions.
