Dynamics of QCD hard probes in eA and pA collisions
In electron-ion collisions, hadron production receives sizable nuclear matter corrections. In the past, calculations based on a phenomenologically modified DGLAP (mDGLAP) equation well described these phenomena. To elucidate the physics contained in the mDGLAP approach, we performed a renormalization group analysis on the parton evolution in nuclear matter.
We find that in a dilute or fast-expanding medium, radiative corrections to collinear observables are enhanced by $\ln \left[E/(L\mu_D^2)\right]$. $E, L,\mu_D$ are the jet energy, medium size, and the inverse scattering length in the medium. Multiple medium-induced radiations are resummed by a set of partial differential equations with a surprising traveling-wave-like solution, encoding parton energy loss effects. Despite the apparently different form, these differential equations are equivalent to a particular version of mDGLAP, but are much simpler for practical applications and bear a clear physical picture of the mechanism of medium modifications. Applications to studying the modified fragmentation in $eA$ collisions, hadron quenching in high-energy $pA$ collisions, and future improvements are discussed at the end.