The probability distribution D(epsilon) in the energy loss incurred by
incoming and outgoing hard quarks in a QCD medium is computed numerically from
the BDMPS gluon spectrum. It is shown to follow an empirical log-normal
behavior which allows us to give the quenching weight a simple analytic
parameterization. The dependence of our results under the infrared and
ultraviolet sensitivity of the gluon spectrum is investigated as well. Finally,
as an illustration, we discuss and compare estimates for the quenching of
hadron spectra in nuclear matter and in a quark-gluon plasma to HERA and RHIC
preliminary data.Comment: 29 pages, 11 figures. Typo corrected in Eq.(4.17
