[Seminars] HEP Seminar Today - March 9

Holly Hernandez holly2 at uchicago.edu
Mon Mar 9 09:39:26 CDT 2015


Monday March 9, 2015
LASR 162

Speaker: Christopher Rogan (Harvard)

Title: Kinematic Variables for Dark Matter at the LHC

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 providing candidates for Dark Matter. 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 discuss a collection kinematic variables developed to study final states with weakly interacting particles at the LHC, focusing on the super-razor variables. 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 of the super-razor variables to more complicated decay topologies are also discussed, using fully leptonic top quark pair production as an example, along with its supersymmetric analogue of stop pair-production with subsequent decays to b-quarks and charginos.

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