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.
Highlights
The LHC has several searches for physics beyond the standard model (BSM) that involve large missing transverse energy (=ET)
We can rephrase our focus as allowing for the possibility of a gravitino lightest supersymmetric particle (LSP), an arbitrary hierarchy of electroweakino soft masses, and additional electroweakinos, what are the criteria for WÆZ0 þ =ET to fail in electroweakino detection while WþW− þ =ET succeeds? And in these scenarios, what are the additional experimental consequences?
In the minimal supersymmetric standard model (MSSM) suppressing the WÆZ0 þ =ET implies that the whole Higgsino doublet will be the lightest of the electroweakinos and will have neutral states contributing to the same final state in the decays to the gravitino LSP
Summary
The LHC has several searches for physics beyond the standard model (BSM) that involve large missing transverse energy (=ET). To narrow our scope further, we will look for scenarios where a different final state WþW− þ =ET takes over as the dominant discovery channel With these caveats, we can rephrase our focus as allowing for the possibility of a gravitino LSP, an arbitrary hierarchy of electroweakino soft masses (and μ term), and additional electroweakinos, what are the criteria for WÆZ0 þ =ET to fail in electroweakino detection while WþW− þ =ET succeeds? Our conclusions regarding the relative sensitivity of WÆðlþνÞZ0ðlþl−Þ and WþW− þ =ET (or lþl− þ =ET) are not restricted to supersymmetric extensions of the SM
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