Reinterpreting pp→W+W− searches for charginos

Abstract

The hallmark way to search for electroweakinos in natural supersymmetry at the LHC involves the trilepton plus missing energy final state. This approach assumes an electroweakino mass hierarchy that allows for cascade decays leading to a final state of $W^{\pm}Z^0$ plus missing energy. There are, however, situations when that decay pattern may not exist, such as when a chargino is the lightest electroweakino and the lightest supersymmetric particle is the gravitino. In regions of the parameter space where this ordering occurs, the production of any combination of neutralino/chargino leads to a $W^+W^- + X$ plus missing energy final state, where $X$ could be additional jets or leptons. If $X$ is soft, then all neutralino/chargino production modes fall into the same experimental final state, dileptons plus missing energy. ATLAS and CMS have leptonic $W^+W^-$ plus missing energy searches, but their interpretation assumes a spectrum consisting of an isolated charged state. In this paper, we identify the circumstances under which natural supersymmetry models can avoid $W^{\pm}Z^0$ plus missing energy bounds. For scenarios that escape $W^{\pm}Z^0$ plus missing energy, we then recast the latest ATLAS $W^+W^-$ plus missing energy search, taking into account all the states that contribute to the same signal. Assuming the lightest supersymmetric particle is massless, we find a bound of 460 GeV for a higgsino-like degenerate doublet. Finally, we extend our arguments to a non-supersymmetric simplified model containing new electroweak-scale $SU(2)_w$ doublets and singlets.