  We investigate multi-lepton LHC signals arising from an extension at the
grand unification scale of the standard minimal supersymmetric model (MSSM)
involving right-handed neutrino superfields. In this framework neutrinos have
Dirac masses and the mixed sneutrinos are the lightest supersymmetric particles
and hence the dark matter candidates. We analyze the model parameter space in
which the sneutrino is a good dark matter particle and has a direct detection
cross-section compatible with the LUX bound. Studying the supersymmetric mass
spectrum of this region, we find several signatures relevant for LHC, which are
distinct from the predictions of the MSSM with neutralino dark matter. For
instance two opposite sign and different flavor leptons, three uncorrelated
leptons and long-lived staus are the most representative. Simulating both the
signal and expected background, we find that the multi-lepton signatures and
the long-lived stau are in the reach of the future run of LHC with a luminosity
of 100/fb. We point out that if one of these signatures is detected, it might
be an indication of sneutrino dark matter.
