The first MadAnalysis 5 workshop on LHC recasting @ Korea

Analysis 8: ATL-PHYS-PROC-2O16-117

Students
Supervisor(s)	Eric Conte	Benjamin Fuks

1. Analysis summary

A measurement of the tt¯Z and tt¯W production cross sections in final states with:

• two same-charge muons: one muon coming from Z/W and one from the top decay.
• or three leptons (electrons or muons),
• or four leptons (electrons or muons): only ttZ case where Z and the 2 top quarks are decaying leptonically.

The analysis uses a data sample of proton-proton collisions at s√=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb−1. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in σtt¯Z=0.9±0.3 pb and σtt¯W=1.5±0.8 pb, in agreement with the Standard Model predictions.

2. Analysis global information

• ATLAS contact person: nobody
• Center of mass energy: 13 TeV
• Integrated luminosity: 3.2 fb−1
• Link to arXiv: ​https://arxiv.org/abs/1609.01599
• Link to the collaboration page: ​https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2015-22/
• Link to CDS: ​https://cds.cern.ch/record/2211022?ln=fr
• Link to Inspire: ​http://inspirehep.net/record/1485353
• Link to Rivet analyses: ​https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PUBNOTES/ATL-PHYS-PUB-2016-005/

3. Selection description

3.1 Trigger selection

Only events using single-electron OR single-muon triggers are accepted:

• single-electron: one electron with pT > 24 GeV
• single-muon: one muon with pT > 20 GeV

PS: This part cannot usually be described by the fast-simulation of detector.

3.2 Object definition

• electron:
  • pT > 7 GeV,
  • |eta|<2.47. Are excluded electrons in the end-cap, i.e. 1.37 < |eta| < 1.52.
  • 'medium' likelihood identification.
  • transverse impact parameter: |d0|/err(d0) < 5.
  • longitudinal impact parameter: |z_0 x sin\theta | < 0.5 mm
  • isolation criterion:
    • sum PT of tracks in a cone around the electron (the electron track is subtracted) of size = min(10 GeV/PT,0.2) < 6% electron PT.
    • sum ET of clusters in a cone around the electron (the electron cluster is subtracted) of size DR=0.2 < 6% electron PT.

• muon:
  • pT > 7 GeV
  • |eta|<2.4
  • 'medium' identification.
  • transverse impact parameter: |d0|/err(d0) < 3.
  • longitudinal impact parameter: |z_0 x sin\theta | < 0.5 mm
  • isolation criterion: sum PT of tracks in a cone around the muon (the muon track is subtracted) of size = min(10 GeV/PT,0.3) < 6% muon PT.

• common to electron and muon:

Explained here how the objects are defined.

3.3 Cut-flow chart

3.4 Definition of exotic observables

Like SUSY transverse observable. Notice that classical MT2 & MT2W are encoded within the MadAnalysis framework.

3. Detector simulation

Can we use the last release of the Delphes package with the CMS/ATLAS MA5tune-card? or do need to improve the simulation?

4. Validation material

4.1 Monte-Carlo samples

• LO/NLO?
• Model used:
• MC generator program (name + version):
• Shower program (name + version):
• Tune of Pythia:
• PDF set:
• ME/PS merging????

4.2 Reference plots / cut-flows

• List of validation material

4. Validation results

5. Reinterpretation (optional)

6. Questions / issues