METing SUSY on the Z peak

Abstract

Recently the ATLAS experiment announced a 3 $\sigma$ excess at the Z-peak consisting of 29 pairs of leptons together with two or more jets, $E_T^{\mathrm{miss}}>225$ GeV and $H_T\ge 600$ GeV, to be compared with $10.6\pm 3.2$ expected lepton pairs in the Standard Model. No excess outside the Z-peak was observed. By trying to explain this signal with SUSY we find that only relatively light gluinos, $m_{\tilde{g}}\lesssim 1.2$ TeV, together with a heavy neutralino NLSP of $m_{\tilde{\chi }}\gtrsim 400$ GeV decaying predominantly to Z-boson plus a light gravitino, such that nearly every gluino produces at least one Z-boson in its decay chain, could reproduce the excess. We construct an explicit general gauge mediation model able to reproduce the observed signal overcoming all the experimental limits. Needless to say, more sophisticated models could also reproduce the signal, however, any model would have to exhibit the following features, light gluinos, or heavy particles with a strong production cross-section, producing at least one Z-boson in its decay chain. The implications of our findings for the Run II at LHC with the scaling on the Z peak, as well as for the direct search of gluinos and other SUSY particles, are pointed out.

24 pages, 17 figures, simulation improved, Checkmate analysis added, new benchmark point included. Typos corrected, conclusions unchanged

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• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC
• General Gauge Mediation
• Threshold resummation for squark-antisquark and gluino-pair production at the LHC
• Soft gluon resummation for the production of gluino-gluino and squark-antisquark pairs at the LHC
• Search for direct production of charginos, neutralinos and sleptons in final states with two leptons and missing transverse momentum in pp collisions at sqrt(s) = 8 TeV with the ATLAS detector
• Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using $\sqrt{s}=8$ TeV proton--proton collision data
• Search for top squark pair production in final states with one isolated lepton, jets, and missing transverse momentum in $\sqrt{s}=$ 8 TeV pp collisions with the ATLAS detector
• Higgs Physics as a Window Beyond the MSSM (BMSSM)
• Searches for electroweak neutralino and chargino production in channels with Higgs, Z, and W bosons in pp collisions at 8 TeV
• Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at $\sqrt{s}=8$ TeV with the ATLAS detector
• Search for top-squark pairs decaying into Higgs or Z bosons in pp collisions at sqrt(s) = 8 TeV
• Search for supersymmetry using razor variables in events with b-tagged jets in pp collisions at sqrt(s) = 8 TeV
• Search for supersymmetry in events containing a same-flavour opposite-sign dilepton pair, jets, and large missing transverse momentum in $\sqrt{s}=8$ TeV $pp$ collisions with the ATLAS detector
• Search for physics beyond the standard model in events with two leptons, jets, and missing transverse momentum in pp collisions at sqrt(s) = 8 TeV

Cited by in corpus (6)

• The Z boson spin observables as messengers of new physics
• ATLAS on-Z Excess Through Vector-Like Quarks
• Models of 750 GeV quarkonium and the LHC excesses
• Testing ATLAS Z+MET Excess with LHC Run 2
• Conciliating SUSY with the Z-peaked excess
• Revisiting R-invariant Direct Gauge Mediation