Improving the Drell-Yan probe of small x partons at the LHC via a k_t   cut
  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. 
E.G. de Oliveira, A.D. Martin and M.G. Ryskin
hep-ph