Collisional jet quenching becomes probable

In the calculation of the collisional energy loss of hard partons in the hot quark gluon plasma, loop corrections to the tree-level amplitudes are essential: Not only do they provide the necessary screening of long-range interactions, but they also induce the momentum dependence of the coupling {α}. The latter fact, as we argued recently, leads to a crucial modification of the hitherto existing theory of this observable. Instead of dEcollB/dx~α²T²ln(ET/mD²), as first derived by Bjorken, the mean energy loss actually reads dEcoll/dx~α(mD²)T² for ET. Here we evaluate, within this mended framework, a less ``inclusive'' quantity, namely the probability distribution (``quenching weights'') of the collisional energy loss, which is necessary to describe jet quenching in heavy-ion collisions. The result is unambiguously determined by ΛQCD (whereas previous approaches involved ``guessing'' a value for the coupling). Representative Monte Carlo simulations then suggest a substantial collisional component of jet quenching---which hints at a natural explanation of the ``single electron puzzle.''