We study signals of pair produced scalar-tau's that decay
into a tau and a light bino at the LHC, for a specific MSSM
scenario which could explain the observed gamma ray spectrum
in the low-latitudes of Fermi Bubble in the Galactic center.
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.
