wiki:Korea2017-07-ATLAS-EXOT-2016-32

The first MadAnalysis 5 workshop on LHC recasting @ Korea

Analysis 7: ATLAS-EXOT-2016-32

Students Tae Hyun Jung (Analysis Webpage Editor), Kyung Sun Lee, Tae Gun Kim, Seungwon Baek
Supervisor(s) Guillaume Chalons

1. Analysis summary

Search for physics beyond the Standard Model in events containing an energetic photon and large missing transverse momentum. Exclusion limits are also placed in models where dark-matter candidates are pair-produced. Models investigated are simplified DM models, an EFT and a high mass scalar resonance.

2. Analysis global information

3. Selection description

3.1 Trigger selection

The events for the analysis were recorded using a trigger requiring at least one photon candidate above a ET_gamma threshold of 140 GeV to pass "loose" identification requirements. For events in the signal regions defined below, the efficiency of the trigger is more than 98.5%. Events are removed if they contain a bad-quality photon or jet. Events in the signal regions (SRs) are required to have the leading photon satisfying the criteria defined in Section 4 and having ET_gamma > 150 GeV.

3.2 Object definition

  • Photons: The photon identification is based on the profile of the energy deposits in the first and second layers of the electromagnetic calorimeter. Candidate photons are required tohave ET_gamma >10GeV,to satisfy the "loose" identification criteria and to be within |η| < 2.37. Photons used in the event must satisfy additionally the "tight" selection criteria, have |η| < 1.37 or 1.52 < |η| < 2.37. They must be isolated by requiring the energy in the calorimeter in a cone of size Delta R = sqrt((Delta η)2 + (Delta Phi)2) = 0.4 around the cluster barycentre, excluding the energy associated with the photon cluster, to be less than 2.45 GeV + 0.022 x ET_gamma.
  • Electrons: They must fulfil the "medium" identification requirement. Electrons are required to have pT > 7 GeV and |η| < 2.47.
  • Muons: Muon candidates must pass the "medium" identification requirement. Muons are required to have pT > 6 GeV and |η| < 2.7.
  • Taus: The tau leptons decaying to hadrons and tau neutrinos are considered as jets.
  • Jets: Jets are reconstructed with the anti-kt algorithm with a radius parameter R = 0.4. Candidate jets are required to have pT > 20 GeV. Jets used in the event selection are required to have pT > 30 GeV and |η| < 4.5.
  • Overlap removal: If any selected electron shares its ID track with a selected muon, the electron is removed and the muon is kept, in order to remove electron candidates originating from muon bremsstrahlung followed by photon conversion. If an electron lies a distance Delta R < 0.2 of a candidate jet, the jet is removed from the event, while if an electron lies a distance 0.2 < Delta R < 0.4 of a jet, the electron is removed. Muons lying a distance Delta R < 0.4 with respect to the remaining candidate jets are removed, except if the number of tracks with pT > 0.5 GeV associated with the jet is less than three. In the latter case, the muon is kept and the jet is discarded. Finally, if a jet lies a distance Delta R < 0.4 of a candidate photon, the jet is removed.
  • ETmiss: The missing transverse momentum vector Emiss is obtained from the negative vector sum of the momenta T of the candidate physics objects. Calorimeter energy deposits and tracks are matched with candidate high-pT objects in a specific order: electrons with pT > 7 GeV, photons with ET > 10 GeV, muons with pT > 6 GeV and jets with pT > 20 GeV.

3.3 Cut-flow chart

3.4 Definition of exotic observables

None

4. 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?

5. Validation material

5.1 Monte-Carlo samples

  • LO/NLO? NLO for simplified models of DM, LO for EFT
  • Model used: Models with DM pair-produced (vector/axial-vector mediator, EFT, high-mass scalar resonance), DMsimp
  • MC generator program (name + version): MG5_aMC@NLO v2.4.3 for DMsimp, MG5_aMC@NLO v2.2.3 for EFT, Powheg-Box v1 for high mass scalar resonance
  • Shower program (name + version): Pythia v8.212 for DMsimp, Pythia v8.186 for EFT, Pythia v8.210 for high mass scalar resonance
  • Tune of Pythia: A14, AZNLO for high mass scalar resonance
  • PDF set: NNPDF3.0, CT10 and CTEQ6L1 PDF for high mass scalar resonance
  • ME/PS merging????

5.2 Reference plots / cut-flows

See https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2016-32/#tables

6. Validation results

7. Reinterpretation (optional)

8. Questions / issues

9. Analysis Group Contacts

  • Guillaume Chalons:[mail:guillaume.chalons@th.u-psud.fr]
  • Tae Hyun Jung: [mail:thjung0720@gmail.com]
  • Kyung Sun Lee: [mail:kyungsun.lee@yonsei.ac.kr]
  • Tae Geun Kim: [mail:edeftg@gmail.com]
  • Seungwon Baek: [mail:swbaek@kias.re.kr]

10. Links to Relevant files of the Analysis

Last modified 3 years ago Last modified on 08/25/17 05:23:36