Search for Top Squark and Higgsino Production Using Diphoton Higgs Boson Decays

Results are presented of a search for a “natural” supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top quark (the top squark) and the Higgs boson (Higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two $b$-quark jets. In $19.7{\mathrm{fb}}^{-1}$ of proton-proton collision data at $\sqrt{s}=8\mathrm{TeV}$, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the top squark mass below 360 to 410 GeV, depending on the Higgsino mass.

Figure 1

Example Feynman diagram of strong (top) and electroweak (bottom) Higgsino production. The jets or leptons resulting from transitions between Higgsinos are extremely soft in both diagrams due to the near mass degeneracy among the Higgsinos.

Figure 2

Cross section times branching ratio $\mathrm{Br}(H\to \gamma \gamma )$ as a function of top squark and Higgsino masses.

Figure 3

$E_{\mathrm{T}}^{\text{miss}}$ distributions for the data, background predictions, and representative signals for the three event categories (i), (ii), and (iii) in frames (a), (b), and (c), respectively. For each histogram, the last bin includes the overflow.

Figure 4

Limits on SUSY production cross sections for different top squark and Higgsino masses. The regions to the left of the contours are expected (thick dashed red or gray curves) and observed (solid black curves) to be excluded at the 95% level. Black dashed curves reflect the theoretical uncertainty on the cross section. Red dotted curves correspond to 1 standard deviation in expected sensitivity.