Long-lived higgsinos as probes of gravitino dark matter at the LHC
  We investigate the LHC sensitivity to supersymmetric models with light
higgsinos, small R-parity breaking and gravitino dark matter. The limits on
decaying gravitino dark matter from gamma-ray searches with the Fermi-LAT put a
lower bound on the higgsino-like neutralino NLSP decay length, giving rise to a
displaced-vertex collider signature. Using publicly available tools for
simulation of signal, background and detector response, we find that higgsinos
with masses of 100-400 GeV and R-parity violation of approximately 10^-8 to
10^-9 can show up in the 8 TeV LHC data with 10-30 fb^-1 of integrated
luminosity. We demonstrate that in the case of a signal, the higgsino mass can
be determined by reconstruction of the dimuon mass edge.
