750 GeV Diphoton Excess from the Goldstino Superpartner

We interpret the diphoton excess recently reported by the ATLAS and CMS Collaborations as a new resonance arising from the sgoldstino scalar, which is the superpartner of the Goldstone mode of spontaneous supersymmetry breaking, the goldstino. The sgoldstino is produced at the LHC via gluon fusion and decays to photons, with interaction strengths proportional to the corresponding gaugino masses over the supersymmetry breaking scale. Fitting the excess, while evading bounds from searches in the dijet, $Z\gamma$, $ZZ$, and $WW$ final states, selects the supersymmetry breaking scale to be a few TeV and particular ranges for the gaugino masses. The two real scalars, corresponding to the $CP$-even and $CP$-odd parts of the complex sgoldstino, both have narrow widths, but their masses can be split of the order of 10–30 GeV by electroweak mixing corrections, which could account for the preference of a wider resonance width in the current low-statistics data. In the parameter space under consideration, tree level $F$-term contributions to the Higgs mass arise, in addition to the standard $D$-term contribution proportional to the $Z$-boson mass, which can significantly enhance the tree level Higgs mass.

Figure 1

Gluon fusion production of the sgoldstino scalars $\varphi$ and $a$, which subsequently decay to two photons.

Figure 2

The green region is allowed by the Run I searches in the $Z\gamma$, $ZZ$, and $WW$ final states, while the blue region is preferred by the Run II diphoton excess. The different edges of the allowed region correspond to the exclusion limits from $ZZ$ (excluded above the solid line) and $WW$ (excluded above the dashed line) searches, while the $Z\gamma$ constraint lies outside of the upper edge of the plot.

Figure 3

The two blue regions in the ($m_3$, $m_1$) plane corresponding to two different values of $m_2$ show the viable parameter space that can fit the diphoton excess without being excluded by any other search channel.