  The observation of jet quenching in ultra-relativistic heavy ion collisions
demonstrates significant energy loss of fast partons when passing through the
created medium. Correlations between final-state particles at intermediate
transverse momentum (1.0 $\lesssim$ $p_{T}$ $\lesssim$ 4.0 GeV/$c$) allow for
study of the medium and its response to deposited energy. Comparison of these
measurements in heavy ion collisions with measurements in proton collisions
show strong modification of the correlation shape and particle yields. Two new
structures are created, both extended in $\Delta\eta$, one centered at
$\Delta\phi=0$ (``ridge'') and the other occurring at
$\Delta\phi\approx\pi\pm1.1$ (``shoulder''). In these proceedings, we describe
the measurements of these structures that show consistency with a scenario of
parton-medium interaction and response. We discuss a new analysis which selects
on the angle of trigger particles relative to the reaction plane in Run7. New
measurements of the centrality and $p_{T}$ dependencies of the structures raise
the possibility that the same production mechanism may give rise to both
phenomena.
