The first MadAnalysis 5 workshop on LHC recasting @ Korea

Analysis 2: CMS-EXO-16-012

Students Yongsoo Jho (Yonsei University), Jiwon Park (Hanyang University), An Seohyun (Hanyang University), Wenxing Zhang (CITP)
Supervisor(s) Guillaume Chalons, Jory Sonneveld

1. Analysis summary


A search for dark matter is performed using events with large missing transverse momentum and a Higgs boson decaying either to a pair of bottom quarks or to a pair of photons. We are only interested in the photon pair final state. This analysis searches for excesses over the background-only prediction in events with large pTmiss and a diphoton system that has a reconstructed invariant mass close to the mass of the SM-like Higgs boson h.

2. Analysis global information

Selections are based on:

Ref [60] arXiv:1508.07819

Ref [61] arXiv:1407.0558

Generator information

Model information:



Note that the gridpacks/LHE files are produced common for bb and gamma gamma (infact all monoH final states) without decaying the Higgs boson in Madgraph. This is due to the known ddrawback of Madgraph of wrong branching ratio of Higgs decay modes. The Higgs is instead decayed using Pythia.

3. Selection description

3.1 Trigger selection

Diphoton triggers with asymmetric transverse energy thresholds (30/18 GeV) are used to select events with the diphoton invariant mass above 95 GeV. The trigger selection uses a very loose photon identification based on the cluster shower shape and loose isolation requirements and a requirement that the ratio of hadronic-to-electromagnetic energy (H/E) of the photon candidates is less than 0.1.

3.2 Object definition

A global event reconstruction is performed using the particle-flow (PF) algorithm.

  • Jets: Jets are reconstructed from the PF candidates using the anti-kT clustering algorithm with distance parameters of 0.4 (AK4 jet) and 0.8 (AK8 jet), as implemented in the FASTJET package. A pruning algorithm is applied to AK8 jets.
  • Photons: Two categories (the barrel–endcap transition region of 1.44 < |eta| < 1.57, where photon reconstruction is not optimal is excluded)
    • Photons with |eta| < 1.44
    • Photons with 1.566 < |eta| < 2.5
    Photon reconstruction and identification seems very involved (using BDTs) but efficiency is given.
  • Electrons: The reconstructed electrons must lie within |eta| < 2.5
  • Muons: Muons candidates are required to be within the region |eta| < 2.4
  • Taus: Tau lepton candidates are required to have |eta| < 2.3

3.3 Cut-flow chart

3.4 Definition of exotic observables


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

Contact with CMS people established. Waiting for the material

5.1 Monte-Carlo samples

  • LO/NLO? LO
  • Model used: Z′-2HDM
  • MC generator program (name + version): MADGRAPH5 aMC@NLO v2.3.0
  • Shower program (name + version): PYTHIA 8.205
  • Tune of Pythia: CUETP8M1
  • PDF set: NNPDF 3.0
  • ME/PS merging???? MLM

5.2 Reference plots / cut-flows

  • List of validation material

6. Validation results

7. Reinterpretation (optional)

8. Questions / issues

9. Analysis People Contact

  • Jory Sonneveld: [mail:]
  • Guillaume Chalons: []
  • Yongsoo Jho: []
  • Jiwon Park: []
  • Seohyun An: [mail:]
  • Wenxing Zhang: [mail:]

10. Link to Relevant Files for the Analysis

Last modified 3 years ago Last modified on 08/25/17 05:19:48