Catching sparks from well-forged neutralinos

Abstract

In this paper we present a new search technique for electroweakinos, the superpartners of electroweak gauge and Higgs bosons, based on final states with missing transverse energy, a photon, and a dilepton pair, ${\ell }^{+}{\ell }^{-}+\gamma +/E_T$. Unlike traditional electroweakino searches, which perform best when $m_{{\tilde{\chi }}_{2,3}^0}-m_{{\tilde{\chi }}_1^0},m_{{\tilde{\chi }}^{\pm }}-m_{{\tilde{\chi }}_1^0}>m_Z$, our search favors nearly degenerate spectra; degenerate electroweakinos typically have a larger branching ratio to photons, and the cut $m_{\ell \ell }\ll m_Z$ effectively removes on-shell Z boson backgrounds while retaining the signal. This feature makes our technique optimal for `well-tempered' scenarios, where the dark matter relic abundance is achieved with inter-electroweakino splittings of $\sim 20-70\text{GeV}$. Additionally, our strategy applies to a wider range of scenarios where the lightest neutralinos are almost degenerate, but only make up a subdominant component of the dark matter -- a spectrum we dub `well-forged'. Focusing on bino-Higgsino admixtures, we present optimal cuts and expected efficiencies for several benchmark scenarios. We find bino-Higgsino mixtures with $m_{{\tilde{\chi }}_{2,3}^0}\lesssim 190\text{GeV}$ and $m_{{\tilde{\chi }}_{2,3}^0}-m_{{\tilde{\chi }}_1^0}\cong 30\text{GeV}$ can be uncovered after roughly $600{\text{fb}}^{-1}$ of luminosity at the 14 TeV LHC. Scenarios with lighter states require less data for discovery, while scenarios with heavier states or larger mass splittings are harder to discriminate from the background and require more data. Unlike many searches for supersymmetry, electroweakino searches are one area where the high luminosity of the next LHC run, rather than the increased energy, is crucial for discovery.

Updated to published version. Reference adde, discussion of other models expanded, and typos fixed. revtex4-1, 29 pages, 9 figures, and 3 tables

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Cited by in corpus (9)

• WIMPs at the Galactic Center
• Monojet plus soft dilepton signal from light higgsino pair production at LHC14
• Accessing the core of naturalness, nearly degenerate higgsinos, at the LHC
• The Relic Neutralino Surface at a 100 TeV collider
• A new approach for detecting compressed bino/wino at the LHC
• Electroweakino constraints from LHC data
• The Not-So-Well Tempered Neutralino
• Illuminating New Electroweak States at Hadron Colliders
• Pseudo-goldstino and electroweakinos via VBF processes at LHC