  Azimuthal correlation functions are used to study jet- and di-jet properties
as a function of centrality in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$=200
GeV. Utilizing a novel technique to decompose the correlation function into a
(di-)jet and an underlying event, the jet-pair distribution is extracted and
compared to similar results for d+Au collisions obtained at the same collision
energy. A striking similarity is observed between the widths and associated
yields of the (di-)jet distributions for d+Au and peripheral Au+Au collisions.
By contrast, the distributions for mid-central Au+Au collisions indicate an
increase in the di-jet yield with centrality, and a very broad away-side jet
having a possible minimum at $\Delta\phi \approx \pi$. These features point to
significant medium induced modification to the away-side jet and are compatible
with recent predictions of jet-induced "conical flow".
