  We present leading hadron suppression predictions in $Pb+Pb$ and $p+Pb$
collisions from a convolved radiative and collisional energy loss model in
which partons propagate through a realistic background, and in which the
radiative energy loss receives a short pathlength correction. We find that the
short pathlength correction is small for $D$ meson $R_{AA}(p_T)$ in both
$Pb+Pb$ and $p+Pb$ collisions. However the short pathlength correction leads to
a surprisingly large reduction in suppression for $\pi$ mesons in $p+Pb$ and
even $Pb+Pb$ collisions, providing a qualitative explanation for the rapid rise
in $\pi$ meson $R_{AA}(p_T)$ at the LHC. We find that the size of the short
pathlength correction to $R_{AA}(p_T)$ is acutely sensitive to the chosen
distribution of scattering centers in the plasma. Furthermore we find that
conventional elastic energy loss models, which apply the central limit theorem
to the number of scatterings, dramatically overpredict suppression in
$\mathrm{p}+\mathrm{A}$ collisions, calling for short pathlength corrections to
elastic energy loss.
