Disentangling shadowing from coherent energy loss using the Drell-Yan process

We propose the measurement of Drell-Yan (DY) lepton pairs in p-Pb collisions at the LHC in order to disentangle the relative contributions of leading-twist shadowing and coherent energy loss in quarkonium production off nuclei. The nuclear modification of low-mass DY production is computed at next-to-leading order using various sets of nuclear parton densities. It is then observed that shadowing effects strongly cancel out in the J/psi over DY suppression ratio R-pA(psi)(y)/R-pA(DY)(y), unlike the effect of coherent energy loss. Such a measurement can be performed at forward rapidity by the ALICE and LHCb Collaborations at the LHC.