  We investigate the method for constructing the invariant mass using the
M_T2-assisted on-shell (MAOS) approximation to the invisible particle momenta
in the cascade decays of a new particle resonance produced at hadron colliders.
We note that the MAOS reconstruction can be defined in several different ways,
while keeping the efficiency of approximation at a similar level, and one of
them provides a unique solution for each event. It is shown that the invariant
mass distribution constructed with the MAOS momenta exhibits a peak at the
heavy resonance mass, regardless of the chosen MAOS scheme and the detailed
mass spectrum of the particles in the cascade. We stress that the MAOS
invariant mass can be used as a clean signal of new particle resonance produced
at the LHC, as well as a model-independent method to measure the masses of new
particles involved in the event.
