Parton energy loss in cold nuclei

Within the generalized high-twist factorization formalism, we express the contribution from multiple parton scattering and induced gluon radiation to the DY dilepton spectra in terms of nuclear modified effective beam quark distribution function. We show that beam quark energy loss is characterized by jet transport parameter qˆ, which is related to the local gluon density of the medium. Using the value of qˆ determined from the deeply inelastic scattering (DIS) data, we evaluate the nuclear modification factor in the Drell-Yan process in p+A collisions. Effects of parton energy loss in the DY spectra are found negligible in the Fermilab experimental data at Elab=800GeV relative to parton shadowing while the predicted suppression of the DY spectra are significant at Elab=120GeV.