Top Quark Width in Lepton+Jets Channel Using Template Method

Summer 2007: 955 pb-1

S. Shiraishi, J. Adelman, E. Brubaker, Y.K. Kim

University of Chicago

CDF Collaboration

E-mail authors

We present the first direct experimental bound on the total decay width of the top quark, Γt, using 955 pb-1 of the Tevatron's ppbar collisions recorded by the Collider Detector at Fermilab. We identify 253 top-antitop pair candidate events. The distribution of reconstructed top quark mass from these events is fitted to templates representing different values of the top quark width. Using a confidence interval based on likelihood-ratio ordering, we extract an upper limit at 95% C.L. of Γt <13.1 GeV for an assumed top quark mass of 175 GeV/c2.

In 955 pb-1 of Run II data, for Mtop=175.0 GeV/c2, we set a limit of

Γtop < 13.1 GeV at 95% confidence level

Documentation

Tables and Plots

Click on any image to link to an .eps file

Description Figures
Feldman-Cousins confidence bands with stastical and systematic uncertainties incorporated. Feldman-Cousins confidence bands including systematics
Combined likelihood for 1-tag and 2-tag samples in the data. Combined likelihood
The reconstructed top mass distributions from the data and the results of the likelihood fits for 1-tag and 2-tag samples. Combined likelihood
The parameterized signal mtreco distributions and goodness of the parameterization are shown for the 2-tag subsample at three different values of Γt. Combined likelihood
Top mass distributions at the generator-level for the samples of Γtopinput = 1.5, 30, and 50 GeV. Generator-level distributions
Top mass distributions at the generator-level with events that passed the event selection cuts after the full detector simulation. The samples are for Γtopinput =1.5, 30, and 50 GeV. Generator-level distributions after selection
Reconstructed top mass distributions for 1-tag samples for Γtopinput =1.5, 30, and 50 GeV. Reconstructed top mass distributions (1-tag)
Reconstructed top mass distributions for 2-tag samples for Γtopinput =1.5, 30, and 50 GeV. Reconstructed top mass distributions (2-tag)
Parameterization of 1-tag reconstructed top mass for the likelihood fit. The fit function is two Gaussian and a Gamma PDF whose parameters are quadratic functions of Γtopinput. Parametrized templates (1-tag)
Parameterization of 2-tag reconstructed top mass for the likelihood fit. The fit function is two Gaussian and a Gamma PDF whose parameters are quadratic functions of Γtopinput. Parametrized templates (2-tag)
Systematic uncertainties on the likelihood. Systematic table
Top width distributions from 3000 pseudoexperiments for Γtopinput =1.5, 5, 15, 30, and 50 GeV. PEs
Coverage for all input top width samples. Coverage tests
Reconstructed top mass distribution for 1-tag sample in the data. Reconstructed mass from data (1-tag)
Reconstructed top mass distribution for 2-tag sample in the data. Reconstructed mass from data (2-tag)
Likelihood fit to 1-tag sample in the data. Likelihood fit (1-tag)
Likelihood fit to 2-tag sample in the data. Likelihood fit (2-tag)
Results of pseudoexperiments assuming the Standard Model (Γtopinput = 1.5 GeV). Roughly 25% of the time, we set an upper limit lower than 12.7 GeV. Expected limit distribution assuming Standard Model
Satomi Shiraishi

Last modified: 8/05/07