  We present a parameter free postdiction of the high-$p_T$ charged-hadron
nuclear modification factor ($R_{AA}$) in two centralities, measured by the CMS
collaboration in $Pb$-$Pb$ collisions at the Large Hadron Collider (LHC). The
evolution of the bulk medium is modeled using viscous fluid dynamics, with
parameters adjusted to describe the soft hadron yields and elliptic flow.
Assuming the dominance of radiative energy loss, we compute the medium
modification of the $R_{AA}$ using a perturbative QCD based formalism, the
higher twist scheme. The transverse momentum diffusion coefficient $\hat{q}$ is
assumed to scale with the entropy density and normalized by fitting the
$R_{AA}$ in the most central $Au$-$Au$ collisions at the Relativistic Heavy-Ion
Collider (RHIC). This set up is validated in non-central $Au$-$Au$ collisions
at RHIC and then extrapolated to $Pb$-$Pb$ collisions at the LHC, keeping the
relation between $\hat{q}$ and entropy density unchanged. We obtain a
satisfactory description of the CMS $R_{AA}$ over the $p_{T}$ range from 10-100
GeV.
