Search for direct production of electroweakinos in final states with one lepton, jets and missing transverse momentum in pp collisions at √s = 13 TeV with the ATLAS detector

Searches for electroweak production of wino-like chargino pairs, X₁^∼+X₁^∼-, and of wino-like chargino and next-to-lightest neutralino, X₁^∼±X₂^∼0, are presented. The models explored assume that the charginos decay into a W boson and the lightest neutralino, X₁^∼± → W^±X₁^∼0. The next-to-lightest neutralinos are degenerate in mass with the chargino and decay to X₁^∼0 and either a Z or a Higgs boson, X₁^∼0 → Z_X1^∼0 or h_X1^∼0. The searches exploit the presence of a single isolated lepton and missing transverse momentum from the W boson decay products and the lightest neutralinos, and the presence of jets from hadronically decaying Z or W bosons or from the Higgs boson decaying into a pair of b-quarks. The searches use 139 fb⁻¹ of √s = 13 TeV proton-proton collisions data collected by the ATLAS detector at the Large Hadron Collider between 2015 and 2018. No deviations from the Standard Model expectations are found, and 95% confidence level exclusion limits are set. Chargino masses ranging from 260 to 520 GeV are excluded for a massless X₁^∼0 in chargino pair production models. Degenerate chargino and next-to-lightest neutralino masses ranging from 260 to 420 GeV are excluded for a massless
for X2^∼0 → Z_X1 ^∼0. For decays through an on-shell Higgs boson and for mass-splitting between X₁^∼±/X1^∼0 and X₁^∼0as small as the Higgs boson mass, mass limits are improved by up to 40 GeV in the range of 200–260 GeV and 280–470 GeV compared to previous ATLAS constraints.