Top Quark Pair in Association with an Extra Jet: Phenomenological Analysis at the Tevatron
- Michigan State Univ., East Lansing, MI (United States)
The first measurement of the cross section of the top quark pair in association with an extra hard jet ($$t\bar{t}$$+jet) has been performed with 4.1 fb₋1 of data collected at CDF. The measurement is an important test of perturbative QCD, as NLO effects play an important role in the calculation of the theoretical cross section. In addition, it is also important as a preview of the LHC, for which almost half of the top quark events will be produced with extra jets. Therefore, this process will be a substan- tial background for many new physics signals. The measurement is performed using SecVtx tagged events in the lepton plus jet channel. A data-driven approach is used to predict the background content, and a 2D likelihood is formed to simultaneously measure the $$t\bar{t}$$+jet and $$t\bar{t}$$ without extra jet cross sections. The measured result is σ$$t\bar{t}$$+jet= 1.6±0.2stat±0.5syst pb which is in agreement with the recent NLO SM predic- tion σ$$t\bar{t}$$+jet = $$+0.16\atop{-3.31}$$ pb . In order to elucidate the kinematic profile of the extra jet, an isolation algorithm has been developed. The algorithm has extracted correctly the extra jet out from the final state jets more than 60% of the time. This allowed for correcting the measured distributions of the extra jet for purity/efficiency in order to compare them with the MC distributions. The differences in the kinematic of the extra jet using different SecVtx requirements and different MC models (PYTHIA & MCFM) have been studied. The agreement between data and the simulations is reasonable. The fifth and the fourth highest ET jet in the final state of $$t\bar{t}$$+jet sample are found to be equally likely the extra jet.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1334774
- Report Number(s):
- FERMILAB-THESIS-2011-66; 1502027
- Country of Publication:
- United States
- Language:
- English
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