  It has been shown through the AdS/CFT correspondence that the energy loss of
a fast quark in a strongly coupled ${\cal N}=4$ SUSY Yang--Mills matter in the
large N limit is given by the classical Lienard formula. I demonstrate that
under quite natural assumptions about the dynamics of heavy ion collisions this
leads to a universal (i.e. independent of the initial parton energy, but
dependent on flavor and centrality) upper bound on the energy of the partons
escaping from the plasma. This bound is a Yang--Mills analog of the Pomeranchuk
bound in classical electrodynamics, where it is a consequence of radiation in a
strong external field acting on a relativistic charge. Since as a result the
massive constituent partons are slowed down to a velocity v < c, the angular
distribution of the emitted radiation exhibits a broad "dead cone". If the
properties of conformal and QCD matter at strong coupling are qualitatively
similar, the existence of this universal upper bound would have dramatic
implications for heavy ion experiments.
