Studies of the Drell-Yan process at the Large Hadron Collider

High energy physics experiments are performed at the Large Hadron Collider (LHC) at CERN colliding bunches of protons at energies up to 13TeV. A fundamental input for any physics study at the LHC is the knowledge of the proton structure in high energy collisions. These quantities need to be extracted from the data; a process that furnishes important constraints is the Drell-Yan process. This consist of massive lepton pair production in hadron collisions through the creation of a vector boson. The document presents a novel benchmark of the different predictions available for the DY, focusing on the effects of fiducial cuts on the final state leptons. The thesis introduces also a novel multi-differential measurement of the DY at low invariant mass of the di-lepton pair, in the region between 7 and 60 GeV, below the the Z boson resonance mass peak. The cross section is measured in 13 TeV proton-proton collisions at the LHC, using the ATLAS detector. The measurement explores an extreme region of the phase space and is sensitive to non-perturbative contributions in the theoretical calculations. Preliminary comparison of the data with state of the art theoretical predictions are also reported.