Mainz 2014 – scientific programme

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T: Fachverband Teilchenphysik

T 75: Supersymmetrie 4

T 75.7: Talk

Wednesday, March 26, 2014, 18:20–18:35, P4

All-hadronic direct stop pair production searches with the ATLAS detector — •Francesca C. Ungaro and Claudia Giuliani — Albert-Ludwigs-Universitaet, Freiburg, Deutschland

Since the beginning of LHC data taking, many efforts have been dedicated to Supersymmetry (SUSY) searches, one of the most promising theories extending the Standard Model.

Tightening constraints from direct searches together with electroweak precision measurements and the mass of the Higgs candidate create tension to traditionally explored SUSY scenarios. On the other hand, the possibility that the third generation of squarks (stop and sbottom) are the lightest remains theoretically promising, especially in the context of naturalness.

This contribution presents an ongoing search for direct stop pair production, performed on the data collected by ATLAS during 2012 at a center-of-mass energy of the proton-proton collisions of √s = 8 TeV. The search has the double target of extending the reach of the stop search assuming a 100% branching ratio (BR) into top and neutralino, as well as exploring the scenario in which the competing decay into a b-quark and chargino is present with varying BRs.

The final state is characterized by large missing transverse energy, due to the presence of the lightest SUSY particle, no leptons and b-tagged jets. In particular the definition of the signal regions in which both stop decay scenarios outlined above are considered will be discussed, and the estimation of the irreducible background of Z decaying into neutrinos, produced in association with heavy flavour jets.