Mixed Stops and the ATLAS on-Z Excess

Abstract

The ATLAS experiment has recently observed a 3-sigma excess in a channel with a leptonically decaying Z, jets, and ETmiss. It is tantalizing to interpret the signal as the first sign of a natural supersymmetric spectrum. We study such a possibility in a minimal model containing light stops and a neutralino LSP. The signal is characterized by a novel topology (compared to previous attempts) where the Z is emitted from a colored particle in the first step of a decay chain, namely t2 -> t1 Z which is characteristic of mixed stops. We show that the excess is compatible with a compressed stop spectrum and is not excluded by any other relevant search, finding some regions of parameter space with signal strength within 1-sigma of that measured by the ATLAS collaboration. In addition, we notice that the corresponding CMS search could be prone to background contamination in unexpected topologies of this kind.

11 pages, 5 figures. v3: final revision with minor additions, matches the version published on PRD

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Cited by in corpus (4)

• ATLAS on-Z Excess Through Vector-Like Quarks
• ATLAS on-Z Excess via gluino-Higgsino-singlino decay chains in the NMSSM
• Testing ATLAS Z+MET Excess with LHC Run 2
• Aspects of astrophysical particle production and beyond the Standard Model phenomenology