- Click here to see the plots for the single and double tag analises with JP<1%.
- Click here to see the plots for the single and double tag analises with JP<5%.
- The detector eta distributions do not have a peak at -1. Rather, there seems to be a slight asymmetry in data between positive and negative detector eta, with more jets in the negative eta region, which the MC does not reproduce. This is also observed in other analysis, like the SecVtx selection. A possible explanation might be that, since the negative eta region is the one that sees the incoming proton beam, there might be higher activity in this region due to beam halo, or it might be a residual asymmetric detector response not fully absorbed by the jet corrections. These are all untested hypothesis.
- Cross section plots:
- Single 1% tag with theoretical cross section
- Single 5% tag with theoretical cross section
- Double 1% tag with theoretical cross section
- Double 5% tag with theoretical cross section
- Single 1% tag with measured cross section
- Single 5% tag with measured cross section
- Double 1% tag with measured cross section
- Double 5% tag with measured cross section
- Cross section plots (same style as kinematic plots):
- Single 1% tag with the theoretical/measured cross section
- Double 1% tag with the theoretical/measured cross section
- Single 5% tag with the theoretical/measured cross section
- Double 5% tag with the theoretical/measured cross section
- We provide event display plots of our 30 double-tag events at 1% using the script borrowed from Harvard (thanks!). For comparison we also show 30 ttbar MC (ttopel) events which pass the same selection.
Plots are HERE.
- We use uncorrected jet Et because this way the tag rate matrices can be used by everybody independently of the level of corrections they choose to make in their particular analysis. I believe this is the way both SecVtx and JetProb matrices have been defined (and blessed). If the concern has to do with a slightly shifted Et spectrum between the uncorrected jets used to parameterize the matrix and the jets used in the analysis, the short answer is indeed that it makes little difference, and the long answer was given at the blessing of the 5.3.3 Tag Rate Matrix, in the second bullet of this link
- We have indeed performed a mistag asymmetry study which is documented in note 7696 and which was accepted at the pre-blessing by the top and the high pt B-tagging groups
- We have performed a study of the Et dependence of the mistag asymmetry. An additional uncertainty due to this Et dependence is added to the total systematic uncertainty. The mistag asymmetry changes from 1.57 ± 0.15 to 1.57 ± 0.18 for JP<1% and 1.27 ± 0.17 to 1.27 ± 0.20 for JP<5%. Note 7696 has been updated.
- The scale factors for Gen4 are 0.787±0.105 and 0.820±0.095 for 1% and 5% JP cuts, respectively.
- The scale factors for Gen5 are 0.817±0.070 and 0.852±0.072 for 1% and 5% JP cuts, respectively.
- The slopes measured in the inclusive electron and Jet50 samples are the following:
- In all cases we measure a slope which is consistent with zero. One measurement, however, is much more accurate than the other (because the Jet50 sample has much higher statistics at high Et). We could either just keep the more accurate measurement, or take the weighted average, which in this case is almost the same thing. Setting the systematics this way does not seem so aggresive. Clearly the difference between the two numbers is not a reasonable estimate of the uncertainty given the large difference in precision between them.
- The note does not have a chi^2 value for the combined slope. The combined slope would be dominated in any case by the Jet50 measurement, for which the fits are shown in the following figures (see figure 14 of note 7444):
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
(Table 13 in the note has a typo
for the weighted average at 1% which will be revised.)
Although the chi^2 is not shown, the fit is seen to be reasonably good.
- See answer to question 14. Numbers in table 1 of note 7697 were old (from Gen4). The Gen5 numbers (from 7444) are the correct ones in the updated note.
- Events lost in the data when applying this cut are events in which the vertex closet to the lepton track is farther than 5 cm (in z) from the highest sumPt vertex. This effect probably arises due to multiple interactions, for which we do not trust the MC would give an accurate description. Fortunately the efficiency of the cut is close to 100% for both data and MC so we do not worry about taking the difference between them as a systematic uncertainty.
- Plots of the number of vertices and of good quality vertices in data (high Pt lepton) vs MC (ttbar) are shown here. The MC predicts less number of vertices, i.e., it underestimates the effects of multiple interactions, and therefore has a higher efficiency than the data for the cut in vtx-z.
- We have calculated the efficiency of the vertex-z cut in two more ttbar samples with min bias: ttop7v and ttop5v. The table below summarizes the efficiencies of this cut for data and for the different MC samples.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
- The theoretical cross section for top masses near 175 GeV increases by about 0.2 pb for every GeV that the mass goes down. At mt=174 GeV the cross section is close to 6.9 pb. The plot would look slightly less scary, we would still be measuring a cross section higher than the theoretical prediction, but in both cases the excess is not statistically significant. The signal MC used to calculate the acceptance and to make the kinematic plots has Mtop=178 GeV. We do not think it is worth the effort to redo the analysis using a lower mass MC at this point.