  In nucleus-nucleus collisions at RHIC and LHC, partons produced at high
transverse momentum can undergo multiple scattering within the collision region
prior to fragmenting into hadrons. We have studied the resulting
medium-modified fragmentation function based on a calculation of the BDMPS-Z
medium-induced gluon radiation for a dense, expanding medium of small finite
extension. Here we explain how the BDMPS transport coefficient which measures
the energy density attained in the collision, can be extracted from the
observed modification of high-pt hadroproduction. We also comment on the
significant remaining uncertainties in extracting the transport coefficient
from data.
