Abstract
A search for charginos and neutralinos at the Large Hadron Collider is reported using fully hadronic final states and missing transverse momentum. Pair-produced charginos or neutralinos are explored, each decaying into a high-$p_{\text{T}}$ Standard Model weak boson. Fully-hadronic final states are studied to exploit the advantage of the large branching ratio, and the efficient background rejection by identifying the high-$p_{\text{T}}$ bosons using large-radius jets and jet substructure information. An integrated luminosity of 139 fb$^{-1}$ of proton-proton collision data collected by the ATLAS detector at a center-of-mass energy of 13 TeV is used. No significant excess is found beyond the Standard Model expectation. The 95% confidence level exclusion limits are set on wino or higgsino production with varying assumptions in the decay branching ratios and the type of the lightest supersymmetric particle. A wino (higgsino) mass up to 1060 (900) GeV is excluded when the lightest SUSY particle mass is below 400 (240) GeV and the mass splitting is larger than 400 (450) GeV. The sensitivity to high-mass wino and higgsino is significantly extended compared with the previous LHC searches using the other final states.
Highlights
Supersymmetry (SUSY) [1,2,3,4,5,6] is a theoretical framework that extends the Standard Model (SM) by introducing new particles (“superpartners”) that have the same quantum numbers as the SM particles except for their spins
The analysis focuses on the hadronic decay modes of the W, Z, and h bosons, namely W → qq, Z → qq =bband h → bb, where q (q ) represents light-flavorquarks u, d, s, c (u ; d ; s; c)
Three physics scenarios are considered in the analysis: (i) a baseline Minimal Supersymmetric Standard Model (MSSM) scenario where bino, wino and higgsino are considered as χheavy or χlight; (ii) a scenario with a gravitino lightest SUSY particle (LSP) and light higgsinos inspired by the general gauge mediation (GGM) [43,44,45,46,47] models and naturalness; (iii) a scenario with an axino LSP assuming the SM extension with a QCD axion and light higgsinos driven by naturalness
Summary
Supersymmetry (SUSY) [1,2,3,4,5,6] is a theoretical framework that extends the Standard Model (SM) by introducing new particles (“superpartners”) that have the same quantum numbers as the SM particles except for their spins. Mass of the neutralino LSP dark matter candidate is constrained to be less than a few TeV by the observed relic density [12,13]; (2) the higgsino mass is motivated to be of the same order as the Z boson mass by naturalness arguments [14,15,16,17]; (3) the MSSM parameter space explaining the discrepancy between the measured muon anomalous magnetic moment [18] and its SM predictions [19] tends to include electroweakinos with masses from 200 GeV to 1 TeV [20,21,22] This search targets the pair production of electroweakinos (χheavy), where each of them decays into a lighter one (χlight) and an on-shell W, Z or SM Higgs boson (h). While each model predicts different electroweakino branching ratios into W, Z, or h, the search combines the dedicated event selections for each decay to achieve only a small model dependency
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