Study of ZZ+jets and Electroweak ZZ+2jets Production in Proton-Proton Collisions at √s = 13 TeV in Four-Lepton Events Using the CMS Detector at the LHC
Abstract: Two studies are presented on di-boson production in association with jets in the fully leptonic final states, pp → (Z/γ∗)(Z/γ∗) + jets → 2ℓ2ℓ′ + jets, (ℓ, ℓ′ = e or μ) in proton-proton collisions at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb−1 collected with the CMS detector at the LHC. In the first study, search is performed for the electroweak (EW) production of two Z bosons in association with two jets (EW ZZ+2jets) using a deep neural network (DNN) approach, and the production is measured with an observed (expected) significance of 4.4 (3.4) standard deviations, consistent with the published CMS results based on a matrix element likelihood approach (MELA). In the second study, differential distributions and normalized differential cross sections of di-boson ZZ production associated with different numbers of jets (ZZ+jets) are measured as a function of jet multiplicity, transverse momentum pT, pseudorapidity η, invariant mass and ∆η of the highest-pT and second-highest-pT jets, and as a function of invariant mass of the four-lepton system for events with various jet multiplicities. These differential cross sections are compared with theoretical predictions that mostly agree with the experimental data. However, in a few regions we observe discrepancies between the predicted and measured values. Further improvement of the predictions is required to describe the ZZ+jets production in the whole phase space.