at 95% confidence level
If the top to tau branching ratio is predicted correctly by the Standard Model then r(tau) would equal 1.0. Our result is therefore consistent with the Standard Model.
The analysis and results were blessed at the 28-APRIL-2004 top meeting.
Using W->taunu to understand tau ID:
We looked in 58 /pb of Run2 data for a pure sample of taus using the physics process W->taunu. We compared the number of W->taunu events in the data with the number predicted by Pythia W->taunu Monte Carlo. The following plot shows the track multiplicity distribution for the tau candidates. The tau signature can be seen in the 1 and 3 track bins, which correspond to 1 and 3 prong tau decays:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
We also compared the tau candidate pt spectrum in the data
with the tau candidate pt spectrum in the Monte Carlo:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Systematic Uncertainties:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Systematic Uncertainties:
Our systematic uncertainty is dominated by
the uncertainty on the tt acceptance shown below:
| Source |
Uncertainty
(%) |
| Electron/Muon ID |
5.0 |
| Tau ID |
10.5 |
| Jet Energy Scale |
5.8 |
| ISR |
7 |
| FSR |
7 |
| PDFs |
1 |
| MC Generator |
7 |
| Total |
17 |
Backgrounds:
The largest background in the analysis is due to jets faking taus. We measure the rate of jets to fake taus in several different data sample and show that they agree with each other to the level of 26%. Shown is the relative fake rate that jets matching to tau candidates passing a subset of tau ID cuts will pass all tau ID cuts:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
We show the Background Summary and Expected Signal in the e,tau channel (top table) and muon, tau channel (lower table):
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
As a check of our analysis we remove some of our final analysis cuts and look at the number of events we predict and expect as a function of the number of jets in the event (0jet, 1 jet, 2 or more jets) and the channel (electron,tau or muon,tau channel) and the charge distribution (OS = the electron or muon is the opposite charge of the tau candidate, SS = the electron or muon is the same charge as the tau candidate.):
Results:
Separating the result into the electron and muon channels we show our observed number of events:
We show one of our two events in a lego plot below, where the calorimeter energies are plotted by calorimeter tower in the CDF Detector. The objects (electron, tau and jets) are labled:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Our Probability distribution for the value r(tau) (defined above) is shown. The most likely r(tau) value is 0.8.
We exclude r(tau) > 5.0 at the 95% confidence level.
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Further details:
More information can be found at the documentation/Q&A page for this analysis (restricted to CDF), or by contacting any one of the good people listed at the top of this page.
Last updated: 06-MAY-2004
The largest background in the analysis is due to jets faking taus. We measure the rate of jets to fake taus in several different data sample and show that they agree with each other to the level of 26%. Shown is the relative fake rate that jets matching to tau candidates passing a subset of tau ID cuts will pass all tau ID cuts:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
We show the Background Summary and Expected Signal in the e,tau channel (top table) and muon, tau channel (lower table):
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
As a check of our analysis we remove some of our final analysis cuts and look at the number of events we predict and expect as a function of the number of jets in the event (0jet, 1 jet, 2 or more jets) and the channel (electron,tau or muon,tau channel) and the charge distribution (OS = the electron or muon is the opposite charge of the tau candidate, SS = the electron or muon is the same charge as the tau candidate.):
| Category |
Predicted |
Seen |
| 0jet, e, OS |
24.3 +/- 3.6 |
17 |
| 1jet, e, OS |
4.8 +/- 0.9 |
5 |
| 2jets+, e, OS |
2.7 +/- 0.4 |
8 |
| 0jet, muon, OS |
21.7 +/- 3.3 |
11 |
| 1jet, muon, OS |
2.8 +/- 0.6 |
4 |
2jets+, muon, OS |
2.2 +/- 0.5 |
1 |
| 0jet, e, SS |
7.3 +/- 1.8 |
8 |
| 1jet, e, SS |
1.9 +/- 0.6 |
3 |
| 2jets+, e, SS |
1.1 +/- 0.3 |
4 |
| 0jet, muon, SS |
5.6 +/- 1.5 |
3 |
| 1jet, muon, SS |
0.8 +/- 0.3 |
0 |
2jets+, muon, SS |
0.6 +/- 0.2 |
0 |
Results:
Separating the result into the electron and muon channels we show our observed number of events:
| Sample |
electron |
muon |
| Background |
0.77 +/-0.12 +/-0.13 |
0.53 +/-0.08 +/-0.08 |
| tt |
0.59 +/-0.05 +/-0.10 |
0.47 +/-0.04 +/-0.07 |
| Data |
2 |
0 |
We show one of our two events in a lego plot below, where the calorimeter energies are plotted by calorimeter tower in the CDF Detector. The objects (electron, tau and jets) are labled:
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Our Probability distribution for the value r(tau) (defined above) is shown. The most likely r(tau) value is 0.8.
We exclude r(tau) > 5.0 at the 95% confidence level.
(left-click to bring up the EPS version of the image)
(right-click to save the GIF version of the image)
Further details:
More information can be found at the documentation/Q&A page for this analysis (restricted to CDF), or by contacting any one of the good people listed at the top of this page.
Last updated: 06-MAY-2004