  We present a comment on the kinematic variable $m_{CT2}$ recently proposed in
"Amplification of endpoint structure for new particle mass measurement at the
LHC". The variable is designed to be applied to models such as R-parity
conserving Supersymmetry (SUSY) when there is pair production of new heavy
particles each of which decays to a single massless visible and a massive
invisible component. It was proposed in "Amplification of endpoint structure
for new particle mass measurement at the LHC" that a measurement of the peak of
the $m_{CT2}$ distribution could be used to precisely constrain the masses of
the SUSY particles. We show that when Standard Model backgrounds are included
in simulations, the sensitivity of the $m_{CT2}$ variable to the SUSY particle
masses is more seriously impacted for $m_{CT2}$ than for other previously
proposed variables.

High Energy Physics - Experiment;High Energy Physics - Phenomenology