Measurement of the ZZ production cross section in p-pbar collisions at sqrt(s)=1.96 TeV
D0 Collaboration, V. Abazov
TL;DR
This study measures ZZ production in proton-antiproton collisions at sqrt(s)=1.96 TeV using the D0 detector, focusing on the ZZ -> 4l final state (4e, 4μ, 2μ2e) with 6.4 fb^-1 of data. A MC-driven, data-informed approach estimates backgrounds and a multi-channel likelihood fit across seven subchannels extracts the Z/γ*Z/γ* cross section, which is then converted to ZZ with a 0.93 factor and combined with the ZZ->ℓℓνν channel for a final cross section. The measured Z/γ*Z/γ* cross section is 1.33^{+0.50}_{-0.40} (stat) ±0.12 (syst) ±0.09 (lumi) pb, consistent with the SM prediction of 1.4±0.1 pb, while the on-shell ZZ cross section is 1.24^{+0.47}_{-0.37} (stat) ±0.11 (syst) ±0.08 (lumi) pb and the combined result is 1.40^{+0.43}_{-0.37} (stat) ±0.14 (syst) pb. The analysis yields a highly significant observation (p-value < 10^-9), with the 10 observed events matching SM expectations and enabling differential distributions of Z/γ*Z/γ* kinematics to be studied at high precision.
Abstract
We present a new measurement of the production cross section $σ(p\bar{p} \rightarrow ZZ)$ at a center-of-mass energy $\sqrt{s}=1.96$ TeV, obtained from the analysis of the four charged lepton final state $\ell^{+}\ell^{-}\ell^{'+} \ell^{'-}$ ($\ell$, $\ell^{'}$ = $e$ or $μ$). We observe ten candidate events with an expected background of $0.37 \pm 0.13$ events. The measured cross section $σ(p\bar{p} \to ZZ)= 1.26^{+0.47}_{-0.37} \mathrm{(stat)} \pm 0.14 \mathrm{(syst)}$ pb is in agreement with NLO QCD predictions. This result is combined with a previous result from the $ZZ\to\ell^{+}\ell^{-}ν\barν$ channel resulting in a combined cross section of $σ(p\bar{p} \to ZZ)= 1.40^{+0.43}_{-0.37} \mathrm{(stat)} \pm 0.14 \mathrm{(syst)}$ pb.