Search for direct production of supersymmetric charginos with mass splittings close to the electroweak scale in $\sqrt{s}=13$ TeV collisions with the ATLAS detector

A new search for the direct production of charginos, each decaying into a neutralino via the emission of a $W$ boson is presented. The search targets a phase space where the mass difference between the chargino and the neutralino is close to the electroweak scale. Such a signal might be hiding behind look-alike Standard Model processes but it has a relatively low production cross section and it has evaded all previous searches at the Large Hadron Collider. In this new analysis, which considers a final state with two leptons from the $W$ boson decays, missing transverse momentum and no hadronic activity, advanced machine learning techniques are adopted to enhance the supersymmetric signal from the backgrounds and achieve unprecedented sensitivity. Results obtained with 139 $\mathrm{fb^{-1}}$ of proton-proton collision data collected by the ATLAS detector at a centre-of-mass energy of 13 TeV are reported.