Drell-Yan lepton pair production at LHC and TMD quark densities of the proton

We use the TMD quark densities of the proton to investigate unpolarized Drell-Yan lepton pair production in proton-proton collisions at the LHC energies. We investigate the case where the gluon-to-quark splitting occurs at the last evolution step and calculate the TMD sea quark density as a convolution of the CCFM-evolved gluon distribution and the TMD gluon-to-quark splitting function which contains all single logarithmic small-x corrections to the sea quark evolution for any order of perturbation theory. Based on the O(alpha) production amplitude of quark-antiquark annihilation calculated according to the reggeized quark approach, we analyze the distributions on the dilepton invariant mass, transverse momentum and rapidity as well as the specific angular correlations between the produced leptons as measured by the CMS, ATLAS and LHCb collaborations. We argue that these measurements impose stringent constraints on the TMD quark distributions of the proton.