  We explore a variant on the MT2 kinematic variable which enables dark matter
mass measurements for simple, one stage, cascade decays. This will prove useful
for constraining a subset of supersymmetric processes, or a class of
leptophilic dark matter models at the LHC. We investigate the statistical reach
of these measurements and discuss which sources of error have the largest
effects. For example, we find that using only single stage cascade decays with
initial state radiation, a measurement of a 150 GeV dark matter candidate can
be made to O(10%) for a parent mass of 300 GeV with a production cross section
of 100 fb and 100 fb^(-1) of integrated luminosity.
