  We consider supersymmetric (SUSY) models in which a very light gravitino is
the lightest SUSY particle. Assuming that a neutralino is the next-to-lightest
SUSY particle, we present a measurement of the neutralino mass at the LHC in
two photons + missing energy events, which is based on the MT2 method. It is a
direct measurement of the neutralino mass itself, independent of other SUSY
particle masses and patterns of cascade decays before the neutralino is
produced.
