Search for pair production of higgsinos in final states with at least three $b$-tagged jets in $\sqrt{s} = 13$ TeV $pp$ collisions using the ATLAS detector

The ATLAS collaboration
Phys.Rev. D98 (2018) 092002, 2018

Abstract (data abstract)
A search for pair production of the supersymmetric partners of the Higgs boson (higgsinos) in gauge-mediated scenarios is reported. Each higgsino is assumed to decay to a Higgs boson and a gravitino. Two complementary analyses, targeting high- and low-mass signals, are performed to maximize sensitivity. The two analyses utilize LHC $pp$ collision data at a center-of-mass energy of 13 TeV, the former with an integrated luminosity of 36.1 fb$^{-1}$ and the latter with 24.3 fb$^{-1}$, collected with the ATLAS detector in 2015 and 2016. The search is performed in events containing missing transverse momentum and several energetic jets, at least three of which must be identified as $b$-quark jets. No significant excess is found above the predicted background. Limits on the cross-section are set as a function of the mass of the higgsino in simplified models assuming production via mass-degenerate higgsinos decaying to a Higgs boson and a gravitino. Higgsinos with masses between 130 and 230 GeV and between 290 and 880 GeV are excluded at the 95% confidence level. Interpretations of the limits in terms of the branching ratio of the higgsino to a $Z$ boson or a Higgs boson are also presented, and a 45% branching ratio to a Higgs boson is excluded for m(higgsino) approximately 400 GeV.

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    Figure 2

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    Distribution of m(h1) for events passing the preselection criteria of the high-mass analysis.

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    Figure 2

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    Distribution of effective mass for events passing the preselection criteria of the high-mass analysis.

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    Figure 15

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    Exclusion limits on higgsino pair production. The results of the low-mass analysis are used below m(higgsino) = 300 GeV, while...

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    Figure 15

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    Exclusion limits on higgsino pair production divided by the theory cross-section.The results of the low-mass analysis are used below m(higgsino)...

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    Figure 15

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    Observed and expected 95% limits in the m(higgsino) vs BR(higgsino to higgs+gravitino) plane. The regions above the lines are excluded...

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    Auxiliary Figure 2

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    The observed and expected 95% upper limits on the total pair production cross section for degenerate higgsinos as a function...

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    Auxiliary Figure 2

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    The observed and expected 95% upper limits on the total pair production cross section for degenerate higgsinos as a function...

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    Auxiliary Figure 3

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    The observed and expected 95% upper limits on the total pair production cross section for degenerate higgsinos as a function...

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    Auxiliary Figure 3

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    The observed and expected 95% upper limits on the total pair production cross section for degenerate higgsinos as a function...

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    Auxiliary Figure 5

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    Particle-level acceptance for the low-mass discovery signal regions low-SR-MET0-meff440 and low-SR-MET150-meff440, shown as a function of higgsino mass. The acceptance...

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    Auxiliary Figure 6

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    The experimental efficiency of the low-mass analysis, for the two discovery signal regions low-SR-MET0-meff440 and low-SR-MET150-meff440, as a function of...

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    Auxiliary Figure 7

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    Particle-level acceptance for the high-mass discovery signal regions SR-4b-meff1-A-disc and SR-3b-meff3-A, shown as a function of higgsino mass. The acceptance...

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    Auxiliary Figure 8

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    The experimental efficiency of the high-mass analysis, for the two discovery signal regions SR-4b-meff1-A-disc and SR-3b-meff3-A, as a function of...

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    Auxiliary Table 1

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    Example cutflow for SR-3b-meff3-A.

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    Auxiliary Table 2

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    Example cutflow for SR-4b-meff1-A-disc.

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    Auxiliary Table 3

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    Cutflow for low-mass analysis for each signal mass point.

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