---
# System prepended metadata

title: '$Z \rightarrow \tau\tau \rightarrow \mu e\nu_{\mu}\nu_{e}\nu_{\tau}\nu_{\tau}$  branching fraction'

---


# $Z \rightarrow \tau\tau \rightarrow \mu e\nu_{\mu}\nu_{e}\nu_{\tau}\nu_{\tau}$  branching fraction
### QAU Master students - Winter22

## References

- Official CMS Run2 recommendations:
https://twiki.cern.ch/twiki/bin/viewauth/CMS/PdmVRun2LegacyAnalysis

- List of available information on each sample:
https://raw.githubusercontent.com/CMSMUSiC/NanoMUSiC/main/docs/nano_content/nanoaod_content_MC_2018.md

- Z cross-section:
  https://twiki.cern.ch/twiki/bin/viewauth/CMS/StandardModelCrossSectionsat13TeV

- $Z \rightarrow leptons$ or $\tau\rightarrow \mu(e)\nu\nu$ Branching Fraction:
https://pdglive.lbl.gov/Viewer.action

- Reference: old  $H\rightarrow\tau\tau$ analysis:
http://cms.cern.ch/iCMS/jsp/openfile.jsp?tp=draft&files=AN2008_053_v5.pdf

## The Analysis

$\sigma_{pp \rightarrow Z(pT >\text{ 50 GeV})}$ = 180332.9 pb (from theory)
BR ($Z \rightarrow \tau\tau$) = 0.033658 (from Particle Data Group)

![](https://i.imgur.com/63v3s55.png)



BR ($\tau\tau \rightarrow \mu e\nu\nu\nu\nu$) = **HW** (from Particle Data Group)


<img src="https://i.imgur.com/1qx3mt6.png" alt="drawing" width="200"/>
  

<img src="https://i.imgur.com/EqxgEEq.png" alt="drawing" width="200"/>





### Samples

#### Data:

- Original dataset (**Total Run2: 59.83 /fb**):
`/MuonEG/Run2018D-UL2018_MiniAODv2_NanoAODv9-v1/NANOAOD`
DAS Link: https://cmsweb.cern.ch/das/request?input=dataset%3D%2FMuonEG%2FRun2018D-UL2018_MiniAODv2_NanoAODv9-v1%2FNANOAOD&instance=prod/global

- Local data (**0.004974448 /fb**):

```
/eos/cms/store/user/mthiel/Z_tautau_study/data/9939DC58-A216-E74F-B407-F40923D58931.root
```

- Run/Lumisection filter: -> I need to update 

`/afs/cern.ch/user/f/ftorresd/workSpace/public/lumi_QAU_2022/SingleMuon2018_Run_321012_JSON.txt`


- **HW**: How many events of $Z \rightarrow \tau\tau \rightarrow \mu e\nu_{\mu}\nu_{e}\nu_{\tau}\nu_{\tau}$ do you expect in this data? Do we need more data?
N = cross_section * Luminosity = 

#### MC:

##### Signal
- Original dataset:
`
/DYJetsToTauTau_TauToMuEle_M-50_TuneCP5_13TeV-amcatnloFXFX-pythia8/RunIISummer20UL18NanoAODv9-106X_upgrade2018_realistic_v16_L1v1-v1/NANOAODSIM
`
DAS Link: https://cmsweb.cern.ch/das/request?input=dataset%3D%2FDYJetsToTauTau_TauToMuEle_M-50_TuneCP5_13TeV-amcatnloFXFX-pythia8%2FRunIISummer20UL18NanoAODv9-106X_upgrade2018_realistic_v16_L1v1-v1%2FNANOAODSIM&instance=prod/global

- Local data:

```
/eos/cms/store/user/mthiel/Z_tautau_study/MC/signal/16CA4948-5784-704D-B5A0-C0AAD28DCCB8.root
```

##### Background (to be evaluated the need)
 - $WW$
 - $t\bar{t}$

### Selection

- Trigger: HLT_Mu27_Ele37_CaloIdL_MW OR HLT_Mu37_Ele27_CaloIdL_MW  (need do check)
- muon pT cut: ???
- electron pT cut: ???
- muon $\eta$ cut: standard (Official CMS Run2 recommendations) $\rightarrow$   $|\eta|<2.4$
- electron $\eta$ cut: standard (Official CMS Run2 recommendations) $\rightarrow$ $|\eta|<2.4$
- muon Identification: standard (Official CMS Run2 recommendations) $\rightarrow$ 
- electron Identification: standard (Official CMS Run2 recommendations) $\rightarrow$ 
- Opposite charge: standard
- Muon Isolation: standard (Official CMS Run2 recommendations) $\rightarrow$ 
- Electron Isolation: standard (Official CMS Run2 recommendations) $\rightarrow$ 
- MET requirements: ????
- angular cuts: ???
- 

## To Do:
- Answer the home works (HW)
- run the analyis code only for MC without selection
-- it will be used to define the selection cuts
-- produce all the plots as before
--- remember: now we dont have 2 muons, but one muon and one electron (look at the collection in the nanoAOD)
-- also produce the MET plot (look at the collection in the nanoAOD)


### Tips:
- To test your code do not run over all events, set less events (~1k) in order to check if your code is working
- 

