Improving the Drell–Yan probe of small

We show that the observation of the Drell–Yan production of low-mass lepton-pairs (M≲20 GeV) at high rapidities (Y≳3) at the LHC can make a direct measurement of parton distribution functions (PDFs) in the low x region, x≲10−4. We describe a procedure that greatly reduces the sensitivity of the predictions to the choice of the factorization scale and, in particular, show how, by imposing a cutoff on the transverse momentum of the lepton-pair, the data are able to probe PDFs in the important low scale, low x domain. We include the effects of the Sudakov suppression factor