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

Abstract Searches for electroweak production of wino-like chargino pairs, $$ {\overset{\sim }{\chi}}_1^{+}{\overset{\sim }{\chi}}_1^{-} $$ χ ~ 1 + χ ~ 1 − , and of wino-like chargino and next-to-lightest neutralino, $$ {\overset{\sim }{\chi}}_1^{\pm }{\overset{\sim }{\chi}}_2^0 $$ χ ~ 1 ± χ ~ 2 0 , are presented. The models explored assume that the charginos decay into a W boson and the lightest neutralino, $$ {\overset{\sim }{\chi}}_1^{\pm}\to {W}^{\pm }{\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 ± → W ± χ ~ 1 0 . The next-to-lightest neutralinos are degenerate in mass with the chargino and decay to $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 and either a Z or a Higgs boson, $$ {\overset{\sim }{\chi}}_2^0\to Z{\overset{\sim }{\chi}}_1^0 $$ χ ~ 2 0 → Z χ ~ 1 0 or $$ h{\overset{\sim }{\chi}}_1^0 $$ h χ ~ 1 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 $$ \sqrt{s} $$ 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 $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 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 $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 for $$ {\overset{\sim }{\chi}}_2^0\to Z{\overset{\sim }{\chi}}_1^0 $$ χ ~ 2 0 → Z χ ~ 1 0 . For decays through an on-shell Higgs boson and for mass-splitting between $$ {\overset{\sim }{\chi}}_1^{\pm }/{\overset{\sim }{\chi}}_2^0 $$ χ ~ 1 ± / χ ~ 2 0 and $$ {\overset{\sim }{\chi}}_1^0 $$ χ ~ 1 0 as small as the Higgs boson mass, mass limits are improved by up to 40 GeV in the range of 200–260

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