Determining the BDMPS transport coefficient via medium-modified fragmentation functions

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 q̂ which measures the energy density attained in the collision, can be extracted from the observed modification of high-p⊥ hadroproduction. We also comment on the significant remaining uncertainties in extracting q̂ from data.