  In compressed supersymmetry, a light top squark naturally mediates efficient
neutralino pair annihilation to govern the thermal relic abundance of dark
matter. I study the LHC signal of same-sign leptonic top-quark decays from
gluino and squark production, which follows from gluino decays to top plus stop
followed by the stop decaying to a charm quark and the LSP in these models.
Measurements of the numbers of jets with heavy-flavor tags in the same-sign
lepton events can be used to confirm the origin of the signal. Summed
transverse momentum observables provide an estimate of an effective
superpartner mass, which is correlated with the gluino mass. Measurements of
invariant mass endpoints from the visible products of gluino decays do not
allow direct determination of superpartner masses, but can place constraints on
them, including lower bounds on the gluino mass as a function of the top-squark
mass.
