Abstract
A search for chargino–neutralino pair production in three-lepton final states with missing transverse momentum is presented. The study is based on a dataset of sqrt{s} = 13 TeV pp collisions recorded with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 hbox {fb}^{-1}. No significant excess relative to the Standard Model predictions is found in data. The results are interpreted in simplified models of supersymmetry, and statistically combined with results from a previous ATLAS search for compressed spectra in two-lepton final states. Various scenarios for the production and decay of charginos ({tilde{chi }}^pm _1) and neutralinos ({tilde{chi }}^0_2) are considered. For pure higgsino {tilde{chi }}^pm _1{tilde{chi }}^0_2 pair-production scenarios, exclusion limits at 95% confidence level are set on {tilde{chi }}^0_2 masses up to 210 GeV. Limits are also set for pure wino {tilde{chi }}^pm _1{tilde{chi }}^0_2 pair production, on {tilde{chi }}^0_2 masses up to 640 GeV for decays via on-shell W and Z bosons, up to 300 GeV for decays via off-shell W and Z bosons, and up to 190 GeV for decays via W and Standard Model Higgs bosons.
Highlights
Supersymmetry (SUSY) [1,2,3,4,5,6] postulates a symmetry between bosons and fermions, and predicts the existence of new partners for each Standard Model (SM) particle. This extension offers a solution to the hierarchy problem [7,8,9,10,11] and provides a candidate for dark matter as the lightest supersymmetric particle (LSP), which will be stable in the case of conserved R-parity [12]
The significance of the difference between the observed and expected yields is calculated with the profile likelihood method from Ref. [169], adding a minus sign if the yield is below the prediction
The bottom panel shows the relative difference between the observed data and expected yields for the control regions (CRs) and the significance of the difference for the validation regions (VRs), calculated with the profile likelihood method from Ref. [169], adding a minus sign if the yield is below the prediction in the simulation in various regions of parameter space and is given by the differences between the estimated and simulated yields of events in the given region
Summary
Supersymmetry (SUSY) [1,2,3,4,5,6] postulates a symmetry between bosons and fermions, and predicts the existence of new partners for each Standard Model (SM) particle. Previous results are extended by analysing the full ATLAS Run 2 dataset, improving the signal selection strategies – for intermediately compressed mass spectra, and exploiting improved particle reconstruction performance. The new results are statistically combined with a previous ATLAS search [18] targeting compressed mass spectra and two-lepton final states. The paper reports updated results for a previous ATLAS search which observed excesses of three-lepton events in the partial, 36 fb−1, Run 2 dataset [15]. 5, 6 covers the general analysis strategy, including the definition of signal regions, background estimation techniques, and systematic uncertainties.
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