# Presentation: 670349

## Update on Single top SLT analysisin the e + jets  channel

- B.Andrieu, E. Busato (LPNHE, Paris)

## Tagging efficiency for W + jets

- Method (see Emmanuel’s talk for results)
- Apply TRFs on preselected, very-tight (lkhood > 0.95), signal-free (HT<200 GeV) W+jets sample
- Compare with direct result  OK
- Determine topology correction using Monte Carlo  is it safe???
- Cross-check  use Z + jets
- QCD background under control  mass plots per jet multiplicity
- “Physical” background negligible (?)
- Flavor composition should be the same as for W + jets (why not?)
- Cross-check results
- Nb(Z + 1 jet) = 1046
-   Data  etag (Z + 1 jet) = 0.38 +-0.19 %
-   TRFs  etag (Z + 1 jet) = 0.33 +-0.18 %
- Nb(Z + 2 jets) = 344
-   Data  etag (Z + >= 2 jets) = 0.87 +-0.50 %
-   TRFs  etag (Z + >= 2 jets) = 0.80 +-0.48 %

## QCD determination

- Assumptions
- 1) W well known (from Z e+e-) and constant
- 2) QCD constant w.r.t. topology (?)
- 3) the W Monte Carlo reproduces data
- What do we learn from the Matrix Method?
- NQCD = QCD (W Nl - Nt) / (W – QCD )
- If we change QCD, only the normalisation of QCD prediction changes, not the shape  nothing to learn on QCD from that
- QCD control sample (lkhood < 0.05) follows the result of Matrix Method consistency check of both assumption 2 and likelihood universality
- NW = W (Nt – QCD Nl) / (W – QCD )
- If we change QCD, the shape of predicted W distributions changes
- Shapes comparison of data (W from Matrix Method) with Monte Carlo constraints QCD

## Effect of N(bad jets) == 0 on data

| Trigger list version | V8
 | V9 | V10
Before change in L1CAL | V10
After change in L1CAL | V11
 | V12 |
| --- | --- | --- | --- | --- | --- | --- |
| Efficiency before triangle cuts | 83 +-0.5% | 84.4 +-0.5% | 80.2 +-2.2% | 89.2 +-0.4% | 89.6 +-0.3% | 88.2 +-0.5% |
| Efficiency on tight presel | 84.5 +-1.8%
(322/381) | 84 +-1.8 %
(337 /401) | 84 +-7.3%
(21/25) | 83.1 +-2.1%
(255/307) | 86.7 +-1.1% (993/1145) | 87.3 +-1.3% (579/663) |
| Efficiency on SLT tag loose | 71.4 +-9.9%
(15/21) | 84.2 +-8.3%
(16/19) | 50% +-35%
(1/2) | 86.6 +-3.0% 
(13/15) | 90.9 +-3.8% (50/55) | 90 +-6.7%
(18/20) |
| Efficiency on SLT tag tight | 66.6+-15.7%
(6/9) | 100 %
(4/4) | Undefined
(0/0) | 100% 
(3/3) | 100%
(20/20) | 93.7 +-1.5%
(15/16) |

- Clear effect of L1CAL eta coverage change
- Efficiency on presel. tight sample: 84.3 +- 1.3 % before, 86.4 +-0.7 % after change
- Efficiency on tagged loose sample: 76.2 +-6.6% before, 90.0 +-3.2 % after change
- Efficiency on tagged tight sample: 76.9 +-11.7% before, 97.4 +-2.5% after change
-  different treatment according to L1CAL coverage?
-  or remove this cut?

## Summary of background studies

|  | preselection | SLT b-tagging | topological |
| --- | --- | --- | --- |
| QCD | Matrix Method
 494 +- 50 | Matrix Method  8+-2
Control sample (direct, TRFs)  7.9 (5.4?)
TRFs on weighted data | Matrix Method
Control sample (direct, TRFs) |
| W + jets | Matrix Method
 1896 +- 71 | Monte Carlo (direct, TRFs)
Control sample (direct, TRFs)  19+-5???
TRFs on weighted data | Monte Carlo (direct, TRFs)
Control sample (direct, TRFs) |
| Combined 
(QCD & W+ jets) | known to 2%
 ~ 2330 +-50  | TRFs on data
+ correction | TRFs on data
+ correction |
|  t-tbar | Sigma(t-tbar)
+ Monte Carlo
 40  | Monte Carlo
 7 | Monte Carlo |

## To do list (not exhaustive...)

- Solve QCD mystery
- Understand TRFs prediction discrepancy w.r.t. data
- Use Z + jet(s) (W + 1 jet?)
- Topological selection
- Trigger efficiency
- Cross-checks: event rates and all kind of distributions vs lumi, trigger list, ...