Physics and Astronomy, Department of


First Advisor

Daniel Claes

Date of this Version

Summer 7-25-2013


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Physics & Astronomy, Under the Supervision of Professor Daniel Claes. Lincoln, Nebraska: August, 2013

Copyright (c) 2013 Jason Keller


A measurement is made of the top quark pair production cross section through the decay channel ttbar -> mu nu + jets, carried out using the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC), located at CERN in Geneva, Switzerland. The top quark pair events were produced in proton-proton collisions at a center-of-mass energy of 8 TeV. To facilitate the detection of ttbar events, jets produced from bottom quarks, which are decay products of the top quarks, are identified using electrons with low transverse momentum with respect to the beam axis (soft electrons). The dominant background, W + jets production, is estimated using the preferential production of W+ over W- at the LHC. Techniques to measure or estimate the remaining backgrounds, and the identification efficiency of the soft electron technique are also discussed. The final result of this study is sigma = 228.9 +/- 4.8 (stat) +27.7 -27.8 (syst.) +/- 10.1 (lumi) pb.

Adviser: Daniel Claes