  Once new particles are discovered at the LHC and their masses are measured,
it will be of crucial importance to determine their spin, in order to identify
the underlying new physics model. We investigate the method first suggested by
Barr and later extended by others to distinguish between Supersymmetry and
alternative models, e.g. Universal Extra Dimensions, in a certain cascade
decay. This method uses invariant mass distributions of the outgoing Standard
Model particles to measure the spin of intermediate particles, by exploiting
the quark/anti-quark asymmetry of the LHC as a pp collider, which is limited
for first generation quarks. In this work, we suggest instead to measure the
charge of the outgoing quark, in case it is a third generation quark. The
resulting asymmetry for a bottom quark is similar to the previous method, while
it is independent of hadronic uncertainties. Furthermore, for a top quark, the
asymmetry allows better distinction between the models, as demonstrated by a
quantitative analysis of model discrimination. We also show that the top's
decay products can be used instead of the top itself, when the reconstruction
of the top momentum is difficult to accomplish, and still provide information
about the spin.
