Decoherence between the initial and final state radiation in a dense QCD medium

We study medium modifications to the interference pattern between initial and final state radiation. We compute single gluon production off a highly energetic parton that undergoes a hard scattering and subsequently crosses a dense QCD medium of finite size. Multiple soft scatterings with the medium are resumed within the harmonic oscillator approximation. We find the decoherence of correlated partons traversing the medium depends on two scales: the medium length L and the decorrelation time of the gluon due to the medium τf. This interplay gives origin to two different asymptotic limits of the gluon spectrum: the coherent (τf≫L) and incoherent regime (τf≪L). We discuss the main characteristics of each regime. We show that in both cases there is a gradual onset of decoherence between the initial and final state radiation due to multiple scatterings, that opens the phase space for large angle emissions. We comment on the phenomenological consequences (such as radiative energy loss) of this setup in pA collisions.