# Presentation: 799446

## Status of the Top cross section analyses

*Elizaveta Shabalina (UIC) *
*(with J.Kozminski, P.Mal, S.Anderson, J.Leveque, T.Golling, M-A.Pleier, J-R.Vlimant, G.Otero, S.Khanov, J.Strandberg) *
***All D0 meeting***
***01 October 2004***** **

## On the way to publication

- Dilepton/topological
**ee, e****μ**** – note submitted to the Top group review**
**μμ**** – analysis complete**
- Lepton+jets/topological
**μ****+jets – analysis complete, note is ready**
**e+jets – analysis is not ready yet**
- Lepton+jets/lifetime b-tagging
**Work in progress on systematics    **

## Summary of changes: topological analyses

- All
- More luminosity (~80 pb-1)
- New cut order common for all channels
- New channel orthogonality requirements
- New vertex cut (d0reco,d0root)
- Event quality variable
- EMID: hmx8->hmx7
- MuonID: correction of pT’s for CFT-only ’s
- Full optimization

- Dilepton
- MET oversmearing in MC (ee, eμ channels)
- Additional (previously disregarded backgrounds) are considered in dilepton channels
- Substantially higher statistics for major background (Z->  in particular)
- new Zj, Zjj MC samples, W+jets

## Dielectron channel: efficiency

**7.6%**

## Dielectron channel: summary table I

- Good agreement between predicted background and signal and observed number of events in data at all cut levels

## Dielectron channel: summary table II

## Dielectron channel: Lepton distributions

## Dielectron channel: Topological variables

## Electron-muon channel: efficiency

**10.9%**

## Electron-muon channel: summary table I

**8**

## Electron-muon channel: summary table II

## Electron-muon channel: kinematic variables

## Summary of changes: ee, eμ

-      ee
- New optimized cuts
**P_T(e): 20->15 GeV**
**Z window: 75-105->80-100 GeV**
**MET: 35->40 GeV (M_ee<80 GeV)**
**Sphericity> 0.15**
- New estimate of MET fake rate using single photon+2 jets sample

- eμ
- New optimized cuts:
**Change of ********R definition -> 25% less Z->****μμ**
**Addition of ******** (****μ****,MET) -> 30% less background**
- Use W, Z, W, Z samples to estimate photon backgrounds
- Many data and MC based cross checks to understand photon backgrounds
- Inclusion of W->e background
- New 4-component matrix method to cross check fake electron background

## Dimuon channel: Moriond ‘04

- Expected S:B ~0.3
- Zμμ background is the big problem
**Poorly reconstructed muons**
**Large variation in dimuon mass**
**Large MET**

- New:
- Correction of pT’s for CFT-only ’s
**caused background to drop by factor of ~3**
- MET - (,MET) contour
**Misreconstructed muons lead to correlations**
-  2 of Constrained fit to Z mass
**Account for pT and ******** dependence of ******** resolution**

## Dimuon channel: optimization

- Optimization for zFitter 2 and (,MET) contour cuts

**Best Cuts**

**S/B = 1.0**

**0.9**

**1.0**

**1.1**

**1.2**

**1.3**

**1.4**

- Total efficiency = 6.1%

## Dimuon channel: Efficiency

| Category | Cut | Eff | Stat Err |
| --- | --- | --- | --- |
| Muons | Muon ID (>= 2 med, nseg=3, !cosmic) | 0.512 | 0.006 |
|   | Data/MC Muon ID | 1.057 | 0.004 |
|   | Central Track c2 < 4 | 0.995 | 0.001 |
|   | Data/MC Track Match | 0.970 | 0.002 |
|   | Opposite Charge Tracks | 0.885 | 0.005 |
|   | >= 2 Mus (pt > 15 GeV) | 0.701 | 0.008 |
| Orthogonality | Electron Veto | 0.997 | 0.001 |
| Trigger | Dimuon Trigger | 0.934 | 0.005 |
| Jet ID | Fid*Algrthm*Qual (>=2Jets) | 0.812 | 0.008 |
|   | >= 2 Jets (pt > 20 GeV) | 0.928 | 0.006 |
| Vertex Quality | |z|<60 & Ntrk>=3 | 0.974 | 0.004 |
|   | Data/MC PV Quality | 0.997 | 0.002 |
|   | |z_d0reco - z_d0root| < 5cm | 1.000 | 0.001 |
|   | DeltaZ(mu,PV) | 0.993 | 0.001 |
|   | DCA cut | 0.864 | 0.008 |
|   | Data/MC DCA | 0.933 | 0.016 |
|   | Isolation | 0.728 | 0.012 |
|   | Data/MC isolation | 1.002 | 0.004 |
| Topological | zFitter c2 cut | 0.787 | 0.013 |
|   | MET - dPhi(mu,MET) Contour | 0.606 | 0.017 |
|   | Total | 0.061 | 0.001 |

## Dimuon channel: yields

|  | Data | Expected
S+B | Signal | Zjj mass1 | Zjj mass2 | Zjj mass3 | WWjj | WQCD |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Preselection | 218 | 232.0 +/- 2.3 | 3.4 +/- 0.1 | 17.3 +/- 0.8 | 202.6 +/- 2.1 | 2.4 +/- 0.04 | 0.4 +/- 0.04 | 6.8 +/- 0.4 |
| Presel + Z-Fitter  | 57 | 72.7 +/- 1.3 | 2.7 +/- 0.1 | 17.2 +/- 0.8 | 44.4 +/- 1.0 | 2.3 +/- 0.04 | 0.3 +/- 0.03 | 5.7 +/- 0.4 |
| Presel + Contour | 1 | 4.6 +/- 0.2 | 2.1 +/- 0.08 | 0.07 +/-  0.05 | 2.0 +/- 0.2 | 0.1 +/- 0.01 | 0.2 +/- 0.03 | 0.1 +/- 0.05 |
| All cuts | 0 | 2.8 +/- 0.2 | 1.7 +/- 0.07 | 0.07 +/- 0.05 | 0.7 +/- 0.1 | 0.1 +/- 0.01 | 0.2 +/- 0.02 | 0.1 +/- 0.05 |

**Preselection :**** **
** ****Vertex cuts, electron veto **
** ****2 muons, all quality cuts applied**
** ****2 jets with P****T**** > 20 GeV/c**

-  Excess of MC prediction after preselection : + 6%
-  Excess of MC prediction after Zfitter : + 25 %
-  Suspect an overestimate of the Zjj MC, cross check did not reveal any problem

-  Data:  224 pb-1
-  Zjj mass 2 sample statistics up by factor of 2 (~200k)
-  **Only statistical errors are shown**

## Dimuon channel: “to do”

- Assemble final yields and background estimates into the final tables
- Work on the dimuon section of the note (to be integrated with the other two channels)
- Consider alternative method of Z/DY background estimate to evaluate systematics

## Dilepton channels: “to do”

- Evaluate missing systematic uncertainties (EM reco, muon isolation, muon DCA)
- Note update
- Favorite CDF-like plot

## Almost there...

- ee

## Muon+jets channel: optimal choice of topological variables

## Muon+jets channel: likelihood fit result

**Fit linear combination of QCD (inverted tight selection in data), W+4jet and ttbar to data**

## Muon+jets channel: likelihood inputs

## Muon+jets channel: kinematic distributions

**Njet ≥ 4**

## Muon+jets channel: status and “to do”

- Analysis is complete (including most of the systematic) uncertainties
- Note is in internal (convener’s) review

- Use MLM matched W+jets MC samples for data-MC comparison
- Cross checks:
**Use W M_T mass fitting to estimate QCD background**
**Estimate W contamination in QCD sample with reversed isolation and subtract W from QCD template **

**Large improvement in statistical and systematical uncertainties**

## Electron+jets channel: work in progress

- Optimization

## EM reco efficiency in data and MC

- NO sideband subtraction

- sideband subtraction

- (jet-track removal**, | eta****jet ****| < 2**)

**SF = 0.97****±****0.01**

**SF = 0.98****±****0.01**

**More data is needed**