Top Quark Width in Lepton+Jets Channel Using Template Method

Summer 2007: 1 fb^-1

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

University of Chicago

CDF Collaboration

We present an upper limit of the top quark width from ppbar collisions at a center-of-mass of 1.96 TeV collected by the CDF detector. We select ttbar events where one W boson from the top decays leptonically and the other W decays hadronically. Reconstructed top mass distributions of the data are compared to those of Monte Carlo samples with various input top widths using a maximum likelihood fit. Feldman-Cousins prescription is employed to set a limit.

Description	Figures
Top mass distributions at the generator-level for the samples of Γ_top^input = 1.5, 30, and 50 GeV.
Top mass distributions at the generator-level with events that passed the event selection cuts after the full detector simulation. The samples are for Γ_top^input =1.5, 30, and 50 GeV.
Reconstructed top mass distributions for 1-tag samples for Γ_top^input =1.5, 30, and 50 GeV.
Reconstructed top mass distributions for 2-tag samples for Γ_top^input =1.5, 30, and 50 GeV.
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 Γ_top^input.
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 Γ_top^input.
Top width distributions from 3000 pseudoexperiments for Γ_top^input =1.5, 5, 15, 30, and 50 GeV.
Systematic uncertainties on the likelihood.
Coverage for all input top width samples.
Reconstructed top mass distribution for 1-tag sample in the data.
Reconstructed top mass distribution for 2-tag sample in the data.
Likelihood fit to 1-tag sample in the data.
Likelihood fit to 2-tag sample in the data.
Combined likelihood for 1-tag and 2-tag samples in the data.
Feldman-Cousins confidence bands with stastical and systematic uncertainties incorporated.
Results of pseudoexperiments assuming the Standard Model (Γ_top^input = 1.5 GeV). Roughly 25% of the time, we set an upper limit lower than 12.7 GeV.

Description

Figures

Top mass distributions at the generator-level for the samples of Γ_top^input = 1.5, 30, and 50 GeV.

Top mass distributions at the generator-level with events that passed the event selection cuts after the full detector simulation. The samples are for Γ_top^input =1.5, 30, and 50 GeV.

Generator-level distributions after selection

Reconstructed top mass distributions for 1-tag samples for Γ_top^input =1.5, 30, and 50 GeV.

Reconstructed top mass distributions (1-tag)

Reconstructed top mass distributions for 2-tag samples for Γ_top^input =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 Γ_top^input.

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 Γ_top^input.