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

Abstract: Searches for electroweak production of wino-like chargino pairs, ˜χ+
1 ˜χ−1 , and of wino-like chargino and next-to-lightest neutralino, ˜χ±1 ˜χ0
2, are presented. The models explored assume that the charginos decay into a W boson and the lightest neutralino, ˜χ±1 → W ± ˜χ01. The next-to-lightest neutralinos are degenerate in mass with the chargino and decay to ˜χ01 and
either a Z or a Higgs boson, ˜χ02 → Z ˜χ01 or h ˜χ01. 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 ˜χ01 in chargino pair production models. Degenerate chargino and next-to-lightest neutralino masses ranging from 260 to 420 GeV are excluded for a massless ˜χ01 for ˜χ02 → Z ˜χ01. For decays through an on-shell Higgs boson and for mass-splitting between ˜χ±1 / ˜χ02 and ˜χ01 as 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.