Medium-induced gluon radiation: an update

International audienceWe revisit the medium-induced coherent radiation associated to hard andforward (small angle) scattering of an energetic parton through a nuclearmedium. We consider all $1\to 1$ hard forward processes ($g \to g$, $q \to q$,$q \to g$ and $g \to q$), and derive the energy spectrum of induced coherentradiation rigorously to all orders in the opacity expansion and for thespecific case of a Coulomb scattering potential. We obtain a simple generalformula for the induced coherent spectrum, which encompasses the resultscorresponding to previously known special cases