Analysis of Drell-Yan lepton pair production in the p -p (p ¯) colliders using different angular ordering constraints and the kt-factorization approach

In this work, the p -p (p ¯) Drell-Yan lepton pair production (DY) differential cross sections at hadron colliders, such as LHC and TEVATRON, are studied in the k_t-factorization framework. In order to take into account the transverse momenta of incoming partons, we use the unintegrated parton distribution functions of Kimber et al. (KMR) and Martin et al. (MRW) in the leading order (LO), and next-to-leading-order (NLO) levels with the input MMHT2014 PDF libraries. Based on the different off shell partonic matrix elements, we analyze the behaviors of DY differential cross sections with respect to the invariant mass, the transverse momentum and the rapidity as well as the specific angular correlation between the produced leptons. The numerical results are compared with the experimental data, in different energies, which are reported by various collaborations, such as CDF, CMS, ATLAS, and LHCb. It is shown that the NLO-MRW and KMR schemes predict closer results to the data compared to the LO-MRW, since we do not have fragmentation. It is demonstrated that while the q^*+q^¯*→γ^*/Z +g →l⁺+l^- +g subprocess has a negligible contribution, it has a sizable effect in the low dilepton transverse momentum. In agreement with the NNLO, perturbative quantum chromodynamics (pQCD), report (PYTHIA, SHERPA, etc.) by including the higher-order perturbative contributions the better results are archived. On the other hand as the scale of energy increases, for the LHC energies, the Compton subprocess, i.e., q^*+g^*→γ^*/Z →l⁺+l^-+q , has the largest contribution to the differential cross section in the most intervals of some observables, as is expected. The variation of the differential cross section with respect to the various variables such as the invariant mass, the center of mass energy, etc. are discussed. In order to validate our results, we also consider the strong ordering constraint and the KaTie parton-level event generator.