Supersoft SUSY models and the 750 GeV diphoton excess, beyond effective operators

We propose that the sbino, the scalar partner of a Dirac bino, can explain the 750 GeV diphoton excess observed by the ATLAS and CMS Collaborations. We first argue for the existence of couplings between sbino to pairs of Standard Model gauge bosons using effective operator analysis. We then analyze the minimal completion of the effective operator model in which the sbino couples to pairs of gauge bosons through loops of heavy sfermions, with the sfermion-bino coupling originating from scalar potential D-terms. We find that the sbino model may be fit the 750 GeV excess by considering gluon fusion processes with decay to diphotons.

Figure 1

One-loop diagrams contributing to singlet coupling to pairs of gluons and electroweak gauge bosons.

Figure 2

SM singlet coupling to pairs of the lightest Higgs.

Figure 3

$gg\to S$ rate in pb for squark mass vs Dirac mass plane in $p\text{−}p$ collisions at 8 TeV and 13 TeV.

Figure 4

Partial width (GeV) of S to gluon gluon in $m_D\text{−}{m}_s$ plane.

Figure 5

Ratio of diphoton to digluon partial widths in the squark mass vs slepton mass plane.

Figure 6

Scalar potential as a function of slepton VEV and S VEV.