Phd Thesis: Search for Pair-Produced Supersymmetric Top Quark Partners with the ATLAS Experiment
by
yiming abulaiti(PhD)
→
Europe/Stockholm
FB42
FB42
Description
Searches for the supersymmetric partner of the top quark (stop) are motivated by natural supersymmetry, where the stop
has to be light to cancel the large radiative corrections to the Higgs boson mass. This thesis presents three different searches
for the stop at √s = 8 TeV and √s = 13 TeV using data from the ATLAS experiment at CERN’s Large Hadron Collider. The
thesis also includes a study of the primary vertex reconstruction performance in data and simulation at √s = 7 TeV using
tt and Z events. All stop searches presented are carried out in final states with a single lepton, four or more jets and large
missing transverse energy. A search for direct stop pair production is conducted with 20.3 fb−1 of data at a center-of-mass
energy of √s = 8 TeV. Several stop decay scenarios are considered, including those to a top quark and the lightest neutralino
and to a bottom quark and the lightest chargino. The sensitivity of the analysis is also studied in the context of various
phenomenological MSSM models in which more complex decay scenarios can be present. Two different analyses are
carried out at √s = 13 TeV. The first one is a search for both gluino-mediated and direct stop pair production with 3.2 fb−1 of
data while the second one is a search for direct stop pair production with 13.2 fb−1 of data in the decay scenario to a bottom
quark and the lightest chargino. The results of the analyses show no significant excess over the Standard Model predictions
in the observed data. Consequently, exclusion limits are set at 95% CL on the masses of the stop and the lightest neutralino.