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T: Fachverband Teilchenphysik
T 27: Supersymmetrie 2
T 27.1: Vortrag
Montag, 24. März 2014, 16:45–17:00, P4
Direct stop searches in 1 lepton final states in compressed scenarios with the ATLAS detector — •Vakhtang Tsiskaridze — Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
Traditional scenarios of Supersymmetry (SUSY) are under considerable strain from tightening bounds of direct searches as well as the mass of the Higgs boson and electroweak precision data, especially when considering naturalness arguments. One way out are compressed scenarios with a small mass difference between stop (t1) and chargino (.4exχ1±.4exχ1±.3exχ1±.3exχ1±) which could have escaped detection so far at low stop masses.
This analysis searches for direct stop pair production in final states with one lepton, jets and missing transverse energy in 20.3 fb−1of data at √s = 8 Te −0.1em V pp collisions recorded by the ATLAS experiment. The neutralino (.4exχ10.4exχ10.3exχ10.3exχ10) is considered to be the lightest supersymmetric particle (LSP). The stop is assumed decaying to t1 → b+.4exχ1±.4exχ1±.3exχ1±.3exχ1±, while the chargino to .4exχ1±.4exχ1±.3exχ1±.3exχ1± → W±+.4exχ10.4exχ10.3exχ10.3exχ10 with 100% branching ratio. The produced b-jets are very soft and mainly below the pT acceptance of the detector due to the small m(t1) − m(.4exχ1±.4exχ1±.3exχ1±.3exχ1±) mass difference.
To increase the acceptance compared to current ATLAS SUSY results in the 1-lepton channel, a b-jet veto is used which significantly changes the background composition. In the talk the optimization of the analysis for signals assuming gaugino universality, i.e. for m(.4exχ1±.4exχ1±.3exχ1±.3exχ1±) = 2× m(.4exχ10.4exχ10.3exχ10.3exχ10) are presented, together with a discussion of systematic uncertainties.