TestTopic11111246 < Sandbox

---+ Preparation for combination of Heavy Resonance Searches at CMS 

This is a preparatory twiki designed to organise the preparation for a combination of CMS analyses searching for heavy new resonances at predicted by BSM models such as WED or HVT models.

The goal is to outline procedures and datacard requirements that allow for a smooth combination procedure once all individual analyses have passed their approval.

Interesting thoughts to the combination and BSM models to be considered were presented here (interesting slides for combination: https://indico.cern.ch/event/881563/contributions/3730910/attachments/1981776/3301585/200205_Zucchetta.pdf).

---++++ Contacts
   * *CMS*: Daniela Schäfer
   * *ATLAS-CMS combination*: (twiki in preparation), e-group: cms-atlas-hrf@cern.ch
   

---++ Datacard requirements

---++++ General

Before pre-approval:

   * Ensure orthogonality to other CMS analyses with the same final state! 


At the approval stage:

   * Provide two sets of datacards and workspaces for the combination:
      *  As used in the analysis proper
      *  With the signal rate normalised to the cross section of the BSM model times the branching fraction of the considered channel. For example:
           rate signal = xs_BSM * BR_XtoWW * BR_SM_final_state
      *  ATTENTION: for a signal scaled to the BSM cross section an additional yield uncertainty has to be added for PDF and renormalisation scales if they are not already considered
   * The datacards should be provided in the following directory structure:
   * CADI_line* with subfolders  *datacards* and *workspaces*
   *  The datacards and workspaces for the combinatio should have names ending on "_combination.*"



  * analyzers should make sure that the datacards follow the requirements and naming schemes listed below


---++++ Processes


   * Signal process called *Signal*
   * Background processes *Background*
   * Data denoted by *data_obs*
   # The mass range of the signal? 
---++++ Yields
   * Signal yield: xs_BSM * BR_XtoVV/ll *BR_SM_final_state 
   
---++++ Systematics

The following naming scheme should be used for systematic uncertainties that are going to be correlated between analysis. 
If the systematic uncertainty is particular to the single analysis and does not need to be correlated the analyzers may choose the name by themselves under consideration of the naming scheme below:


   * Each nuisance should start with *CMS*
   * If necessary add label for different data taking years e.g. *CMS2016*
   * Add analysis specific label e.g. for an X -> VV -> 2j analysis a good label would be *VV_JJ* 
   * Custom name of the systematic uncertainty e.g. *Bin1*
    


|Systemtic |  Systematic name | type | nuisance type | 
| pdf  | pdf_accept | log-normal | signal acceptance uncertainty due to PDF variation|
| pdf  | pdf_scale | log-normal | signal efficiency uncertainty due to PDF variation|
| scale | qcd_scale | log-normal | signal yield uncertainty due to renormalisation scale | 
| lumi | CMS2016_lumi   | log-normal | yield uncertainty due to luminosity measurement |
| pileup | CMS2016_scale_pu | log-normal | yield uncertainty due to pileup |
| object tagging | CMS2016_eff_objectname | log-normal | yield uncertainty due to object tagging: V (V-tagging with tau21), deepV/H (V/H tagging with DeepJet), b (b-tagging), e/m/t (Electron/Muon/Tau-Identification), (deep)bb ((deep) double-b-tagger)  |
| tagging pT extrapolation | CMS2016_extr_objectname | log-normal | pT extrapolation uncertainties |
| lepton scale/resolution | CMS2016_scale_e/m/t, CMS2016_res_e/m/t | log-normal | yield uncertainty   | 
| lepton scale/resolution | CMS2016_sig_p1_e/m/t, CMS2016_sig_p2_e/m/t | shape | nuisance parameters for the effect on the signal shape   | 
| JES/JER | CMS2016_scale_j, CMS2016_res_j | yield | nuisance for jet energy scale/resolution uncertainties | 
| JES/JER | CMS2016_sig_p1_j, CMS2016_sig_p2_j | shape | nuisance for jet energy scale/resolution uncertainties on signal shape (mean/width) | 
| jet mass (SD) scale/resolution |  CMS2016_scale_mass, CMS2016_res_mass | yield | |
| jet mass (SD) scale/resolution |  CMS2016_sig_p1_mass, CMS2016_sig_p2_mass | signal shape | signal shape nuisance on mean (p1) and widht (p2) due to jet mass uncertainties |
| trigger uncertainties | CMS2016_trigger_name | log-normal | nusiance for trigger efficiency uncertainties  name = [MET, HT, e/m/t, etc.]   |






-- Main.DanielaSchafer - 2020-04-23
Topic revision: r1 - 2020-04-23 - DanielaSchafer
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