  We perform a renormalization group (RG) analysis of collinear hadron
production in deep inelastic scattering on nuclei. We consider the limit where
the parent parton energy $E$ is large, while the medium opacity $L/\lambda_g$
remains small. We identify the fixed order and leading $\ln(E/\xi^2 L)$
enhanced medium contributions to the semi-inclusive cross sections and derive
RG equations that resum multiple emissions near the endpoints of the splitting
functions at first order in opacity. These evolution equations treat the same
type of radiation enhancement in matter as the modified
Dokshitzer-Gribov-Lipatov-Altarelli-Parisi approach, but differ in the way one
regulates the collinear divergences. They provide a unique analytic insight
into the problem of resummation and a faster and more efficient path to
phenomenology. The new RG evolution framework is applied to study fragmentation
in $e$A reactions.
