On sgoldstino interpretation of the diphoton excess

Core claim

The paper's claim is that a scalar sgoldstino of mass 750 GeV, in a supersymmetric extension of the Standard Model with low-scale breaking, reproduces the observed diphoton excess while surviving existing collider bounds. The production is gluon-gluon fusion, dominant because the gluino is taken to be the heaviest gaugino, and the diphoton branching ratio reduces to the ratio of effective couplings, $Br(S to gammagamma) = (M_{gammagamma}/M_3)^2$ up to the appropriate phase-space factor. The authors scan $M_1$ and $M_2$ between 0.2 TeV and $M_{SUSY}$, and $M_3$ between 1.7 TeV and $M_{SUSY}$, for $M_{SUSY} = 5$ and 7 TeV, keeping only models with $3 fb < sigma_{gammagamma} < 13 fb$ at 13 TeV that also pass the 8 TeV diphoton, dijet and diboson limits. They find that the surviving models predict $ZZ$ cross sections up to about 17 fb ($M_{SUSY} = 5$ TeV) and 26 fb ($M_{SUSY} = 7$ TeV), with $WW$ and $Zgamma$ rates of comparable or larger size, all correlated because the couplings share the same gaugino masses and the same $1/F$ suppression. They also note that the resonance width in this minimal setup stays below the GeV scale, so the large width ATLAS somewhat prefers would require an extension with a light singlet scalar, such as in NMSSM-type models, where the sgoldstino can also decay into scalar pairs without disturbing the diboson branching pattern.