1110.6185 (Tom Melia)

Spin before mass at the LHC    [PDF]

Tom Melia

What can be said about the spin of new particles without knowing their mass
during an initial discovery phase at CERN? We consider this question in a
topology where mass measurement is particularly difficult, $pp\to Y\bar{Y}\to
lX\bar{l}\,\bar{X}$, and introduce two new variables $\ctv$ and $\Av$ which we
prove are both independent of the mass of $X$. The variable $\ctv$ approximates
the polar production angle of $Y$, and we find that it possesses greater
statistical power in determining the spin of this particle than a previous,
related variable, $\ctll$ \cite{Barr:2005dz}. $\Av$ is an asymmetry which can
provide information about the couplings of a spin half $Y$. Because these
variables can be used from the outset, without any knowledge of the masses of
the new particles, we find here that it is possible to reverse the usual `mass
before spin' determination timeline.

View original: http://arxiv.org/abs/1110.6185