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 (2021)

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 $$\sqrt{s} = 13$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> <mml:mo>=</mml:mo> <mml:mn>13</mml:mn> </mml:mrow> </mml:math> TeV pp collisions recorded with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 139 $$\hbox {fb}^{-1}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mtext>fb</mml:mtext> <mml:mrow> <mml:mo>-</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> . 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 ( $${\tilde{\chi }}^\pm _1$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>1</mml:mn> <mml:mo>±</mml:mo> </mml:msubsup> </mml:math> ) and neutralinos ( $${\tilde{\chi }}^0_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>2</mml:mn> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> ) are considered. For pure higgsino $${\tilde{\chi }}^\pm _1{\tilde{\chi }}^0_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>1</mml:mn> <mml:mo>±</mml:mo> </mml:msubsup> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>2</mml:mn> <mml:mn>0</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> pair-production scenarios, exclusion limits at 95% confidence level are set on $${\tilde{\chi }}^0_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>2</mml:mn> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> masses up to 210 GeV. Limits are also set for pure wino $${\tilde{\chi }}^\pm _1{\tilde{\chi }}^0_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>1</mml:mn> <mml:mo>±</mml:mo> </mml:msubsup> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>2</mml:mn> <mml:mn>0</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> pair production, on $${\tilde{\chi }}^0_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup> <mml:mrow> <mml:mover> <mml:mi>χ</mml:mi> <mml:mo>~</mml:mo> </mml:mover> </mml:mrow> <mml:mn>2</mml:mn> <mml:mn>0</mml:mn> </mml:msubsup> </mml:math> 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.