Angular dependence of the radiative gluon spectrum and the energy loss of hard jets in QCD media

The induced momentum spectrum of soft gluons radiated from a high energy quark propagating through a QCD medium is derived in the Baier-Dokshitzer-Mueller-Peigne-Schiff formalism. A calorimetric measurement for the medium-dependent energy lost by a jet with opening angle theta(cone) is proposed. The fraction of this energy loss with respect to the integrated one appears to be the relevant observable. It exhibits a universal behavior in terms of the variable theta(cone)(2)L(3)(q) over cap where L is the size of the medium and (q) over cap the transport coefficient. Phenomenological implications for the differences between cold and hot QCD matter are discussed. [S0556-2813(99)06211-1].