CP-violation in cascade decays at the LHC

Abstract

We study the potential to observe CP-violating effects in various supersymmetric cascade
decay chains at the LHC. Asymmetries composed by triple products of
momenta of the final state particles are sensitive to CP-violating
effects. We analytically calculate the cascade decays including the relevant spin correlations to compute the parton level asymmetry. In addition, we use Monte Carlo simulations to estimate the sensitivity of the LHC to the CP-violating observables.

Due to large boosts that dilute the asymmetries, these can be
difficult to observe at the LHC. However, if all particle masses in a cascade decay are
known, it may be possible to reconstruct all momenta in the decay chains. We can then recover the full asymmetry on an
event-by-event basis even when we have missing momentum due to a stable
lightest supersymmetric particle. After the reconstruction, the non-diluted CP-violating signal gets
significantly enhanced so that an observation may become feasible.

A fully hadronic study has also been completed to produce the best estimate of the viability of these obseravbles at the LHC. We include both standard model and SUSY backgrounds in the study. Our conclusions state that given a favourable scenario, CP-violation may be observed in SUSY at the 3-sigma level over a wide range of CP-phases with 500 1/fb of data.