| Abstract [eng] |
A lepton-antilepton pair production in proton-proton collisions is possible when a quark and an antiquark from colliding protons annihilate. This reaction is known as the Drell-Yan process. Current precision measurements of Drell-Yan differential cross section have a high impact on the improvement of proton structure description as well as provide various tests for the current theoretical models. Scientific groups measure the Drell-Yan differential cross section by analyzing the proton-proton collision data and searching for the isolated opposite-charge lepton pairs. There are several physics processes that may produce a similar footprint. These additional processes are referred to as backgrounds. Most background processes produce genuine opposite-charge lepton pairs, though, a few others include leptons produced inside hadronic jets, which were misidentified as isolated leptons and pass the selection criteria. All the most significant backgound contributions must be taken into account in order to produce an accurate measurement. This work presents an estimation of jet-related Drell-Yan backgrounds using a data-driven fake rate method. The work was performed by analyzing the proton-proton collision data collected by CERN CMS experiment in 2016. The ammount of collected data corresponds to an integrated luminosity of 35.9 1/fb (2×10^15 pp collisions). Simulated datasets provided by the CMS collaboration were used to interpret the collected detector data. A dilepton event selection was performed after applying energy and momentum scale corrections to the reconstructed electron and muon physical objects respectively. A number of other corrections were applied to simulated event distributions in order to match the observed experimental conditions. An estimation of the number of jet-related background events was carried out having defined the event selection criteria. A probability that a jet, having passed the relaxed lepton selection criteria, will also pass the stricter identification requirements was estimated. The probability was then used to extract the number of W+Jets (single jet) and QCD (multiple jets) events that pass the Drell-Yan dilepton selection. It was evaluated, that jet-related events correspond to 0.02% and 0.14% of all the selected dimuon and dielectron events respectively. |
