High Energy Physics Seminar

At the Large Hadron Collider (LHC), many new physics signatures feature pair-production of massive particles with subsequent direct or cascading decays to weakly interacting particles, such as SUSY scenarios with conserved R-parity or Higgs decaying to two leptons and two neutrinos through W bosons, often motivated by models of new physics which attempt to mitigate the hierarchy problem in the Standard Model. While final states containing multiple weakly interacting particles represent an opportunity for discovery of new physics phenomena, they also present a unique experimental challenge; the kinematic information lost through particles escaping detection makes fully reconstructing these collision events impossible. In order to address this shortcoming special kinematic variables are used to partially reconstruct these events, providing sensitivity to properties of the particles appearing in them, including masses and even their spin correlations.

We introduce a systematic prescription, Recursive Jigsaw Reconstruction, for generating a preferred kinematic basis of kinematic variables developed to study final states with weakly interacting particles at HEP experiments, specifically catered to each case of interest. Using the examples of slepton pair-production at the LHC, the motivation and derivation of these observables are described along with comparisons to previously existing approaches. Generalizations to more complicated decay topologies are also discussed, including fully leptonic top quark pair production as an example, along with its supersymmetric analogue of stop pair-production with subsequent decays to b-quarks, leptons, and neutrinos.