Events at Physics
The scenario is consistent with the observation only when the dark matter is almost pure bino and the light stau of mass around 100 GeV is a maximally mixed state. The higgsino component of the dark matter is constrained by the Higgs invisible width and the direct DM search experiments, while the large stau mixing enhances the Higgs to two gamma rate and breaks lepton universality of electroweak observables.
At the LHC, both the stau pair production cross section and the produced tau polarization depends strongly on the stau mixing. We show that there is a possibility of observing the signal in tau-pair production events with large missing transverse momentum at LHC8 with 20/fb of integrated luminosity.