Measurement of the Ratio of the Top Pair to Z Boson Cross Section

Tom Schwarz, Andrew Ivanov
Robin Erbacher, Will Johnson

University of California - Davis


Documentation

Public Conference Note


Send mail to authors

Abstract

The ratio of the top pair cross section with the Z boson cross section has been measured in 2.7 fb-1 of collected data from the high Pt lepton triggers. The ratio is insensitive to the uncertainty on luminosity, which previously had been the leading systematic of the top pair cross section measurement. The top cross section is measured in the lepton plus jets channel using events where at least one jet has been "tagged" with a secondary vertex as evidence of a bottom quark decay (&sigmatt = 7.1 ± 0.4stat ± 0.6syst ± 0.4lumi). The Z boson cross section is measured in opposite signed dilepton events in the mass window 66 to 116 GeV (&sigmaZ = 253.5 ± 1.1stat ± 4.5syst ± 14.9lumi). The result is 1/R = 35.7 ± 2.0stat ± 3.25syst where R = &sigmatt/&sigmaZ. The top cross section can be extracted by applying the theoretical Z boson cross section. The result is &sigmatt = 7.0 ± 0.4stat ± 0.6syst ± 0.1Z theory.




Result

The measurement of the top pair cross section using 2.7 fb-1 of CDF collected data is:

&sigmatt = 7.1 ± 0.4stat ± 0.6syst ± 0.4lumi


The measurement of the Z boson cross section is:

&sigmaZ = 253.5 ± 1.1stat ± 4.5syst ± 14.9lumi


The measurement of the ratio R = &sigmatt/&sigmaZ:

1/R = 35.7 ± 2.0stat ± 3.25syst


The extracted top pair cross section:

&sigmatt = 7.0 ± 0.4stat ± 0.6syst ± 0.1Z theory


&Delta &sigma/&sigma = 10 %




Plots & Tables


pdf
Histogram of expected and observed number of events as a function of jet multiplicity for events with at least one secondary vertex "tag", and additional selection Ht > 250 GeV, and MET > 25 GeV.

tex
Table of the expected and observed number of events as a function of jet multiplicity for events with at least one secondary vertex "tag", and additional selection Ht > 250 GeV, and MET > 25 GeV.

pdf
Systematic uncertainties on the measured cross-section.

pdf
Output of the Neural Network flavor separator, used to calculate the heavy flavor fraction in data in W+1 jet events. A correction factor is derived by comparing the result of the neural network fit to the Monte Carlo prediction. The correction factor is cross-checked in the W+2 jet sample and then applied to the signal region W + >=3 jets.

pdf
Z Peak in data and Monte Carlo

pdf
Systematic uncertainties on the measured Z cross-section.

pdf
Systematic uncertainties on the measured Ratio.

pdf
Sum of the transverse energy of jets, lepton, and missing Et in top events.

pdf
Lead Jet Transverse Energy in top events ( GeV )

pdf
Lepton Pt in top events ( GeV )

pdf
Missing Transverse Energy in top events ( GeV )








Last Update on July 29th, 2008 schwarzt@fnal.gov