  Within the framework of a high-twist approach, we show the first complete
next-to-leading order calculation of transverse momentum broadening in
semi-inclusive deeply inelastic $e+A$ scattering and Drell-Yan dilepton
production in $p+A$ collisions. We demonstrate at one-loop level how QCD
factorization holds for multiple scattering in nuclear medium, and the
university of the associated quark-gluon correlation function. Our calculation
also identifies QCD evolution equation for the quark-gluon correlation
function, which determines the QCD factorization scale and energy dependence of
jet transport parameter $\hat q$.
