Search for chargino--neutralino pair production in final states with three leptons and missing transverse momentum in $\sqrt{s} = 13$ TeV $pp$ collisions with the ATLAS detector

TL;DR

This paper reports a search for chargino-neutralino pair production in three-lepton final states at 13 TeV with the ATLAS detector, setting exclusion limits on their masses based on the absence of significant excess over the Standard Model.

Contribution

The study provides new exclusion limits on chargino and neutralino masses in supersymmetry models using the full Run 2 dataset and combines results with previous searches for compressed spectra.

Findings

No significant excess observed over Standard Model predictions.

Exclusion limits on neutralino masses up to 640 GeV for wino scenarios.

Limits on chargino-neutralino production vary depending on decay modes and spectra.

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 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.