Academic Commons

Theses Doctoral

Search for Heavy Down-Type Vector-Like Quarks in the Lepton-Plus-Jets Final State in 8 TeV proton-proton Collisions Using the ATLAS Detector at the LHC

Hu, Diedi

This dissertation presents a search for pair production of heavy down-type vector-like quarks (VLQ B) using the full 2012 data set of proton-proton collisions at the center of mass 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 20.3 1/fb. Events with a single charged lepton, which can be either an electron or muon, missing transverse energy, at least six jets, at least one tagged as a b-jet, and at least one reconstructed hadronically-decaying W/Z boson candidate are analyzed. No significant deviation from the Standard Model background prediction is observed. Under the assumption that only the B->Wt/Zb/Hb decay modes are allowed, 95% CL upper limits are derived in the two dimensional plane of the B->Wt branching ratio versus B->Hb branching ratio. In the specific case where the branching ratios are consistent with a SU(2) singlet scenario, the observed (expected) 95% CL lower limit on the VLQ B mass is 640 GeV (505 GeV). In the chiral B scenario with a 100% branching ratio of the decay B->Wt, the observed (expected) 95% CL lower limit on the B mass is 814 GeV (756 GeV).

Subjects

Files

  • thumnail for Hu_columbia_0054D_12505.pdf Hu_columbia_0054D_12505.pdf binary/octet-stream 9.96 MB Download File

More About This Work

Academic Units
Physics
Thesis Advisors
Parsons, John
Degree
Ph.D., Columbia University
Published Here
February 5, 2015
Academic Commons provides global access to research and scholarship produced at Columbia University, Barnard College, Teachers College, Union Theological Seminary and Jewish Theological Seminary. Academic Commons is managed by the Columbia University Libraries.