(r7) JetFlavourTagging < LinearCollider

LinearCollider Web>JetFlavourTagging (revision 7) (raw view)~~EditAttach~~

---++ ZZ Fusion Analysis 

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This is a detailed record on how the Marlin framework and adjacent packages are used for our analysis of the feasibility of the ZZ fusion channel with CLIC ILD at 1.4 !TeV.

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---+++ Jet Finder and Flavour Tagging 

We use the [[http://hepwww.rl.ac.uk/lcfi/][LCFI]] flavour tagging package. This package consists of a topological vertex finder ZVTOP, which reconstructs secondary interactions, and a multivariate classifier which combines several jet-related variables to tag bottom, charm, and light quark jets (see [[%ATTACHURLPATH%/LCFI_Flow_Diagram.pdf][diagram]]).

Our steering file will contain the jet finder, flavour tagging and LCFI processors, and we will write new =slcio= files containing the added collections: 
<verbatim>
  <group name="JetFinders"/>
  <group name="MyTrueAngularJetFlavourProcessorCollection"/>
  <processor name="IPRPCutProcessor"/>
  <processor name="MyPerEventIPFitterProcessor"/>
  <processor name="ZVRESRPCutProcessor"/>
  <processor name="MyZVTOP_ZVRES"/>
  <processor name="FTRPCutProcessor"/>
  <processor name="MyFlavourTagInputsProcessor"/>
  <processor name="MyLCIOOutputProcessor"/>  
</verbatim>

The *JetFinder* processor reconstructs 2 and 4 jets events from the input collection (!LooseSelectedPandoraPFANewPFOs was used). For the reconstructed 4 jets, *MyTrueAngularJetFlavourProcessor* determines MC Jet Flavour by angular matching of heavy quarks to jets, and also determines hadronic and partonic charge of the jet. 

The LCFI processors have the following functions:

   * !IPRPCut		        - selects Reconstructed Particles based on track parameters, number of hits etc.
   * !MyPerEventIPFitter	- determines IP position and error from the tracks in an event by simple fitting 
   * !ZVRESRPCut            - applies cuts on the d0 and z0 values of the track
   * !MyZVTOP_ZVRES 	- topological vertex finder 
   * !FTRPCut                   - flavour tagging reconstructed particle cuts (on d0, z0 and P<sub>T</sub>)
   * !MyFlavourTagInputs - from vertices and tracks calculates discriminating variables for the neural net

Table of [[%ATTACHURLPATH%/LCFI_Flow_Diagram.pdf][input and output collections]] for our setup (one can choose other names, of course):

   |          *Processor*           |  *Type*    |              *Input Collection name*            |         *Output Collection name*       |
   |  !JetFinder                       |   !SatoruJetFinder  | !LooseSelectedPandoraPFANewPFOs   | Durham_4Jets   |
   | !MyTrueAngularJetFlavour  |   !TrueAngularJetFlavour  | !MCParticlesSkimmed, Durham_4Jets | !TrueJetFlavour_4Jets    |
   |        !IPRPCut              |  !RPCut  | !LooseSelectedPandoraPFANewPFOs  | !IPFitSelectedParticles  |
   |         !MyPerEventIPFitter      |   !PerEventIPFitter    | !IPFitSelectedParticles      | !IPVertex  |
   |  !ZVRESRPCut            |  !RPCut    | !RecoMCTruthLink, Durham_4Jets  | !ZVRESSelectedJets   |
   |      !MyZVTOP_ZVRES      |  !ZVTOP_ZVRES    | !IPVertex, !ZVRESSelectedJets | !ZVRESDecayChains,  !ZVRESDecayChainRPTracks, !ZVRESSelectedJets  |
   |       !FTRPCut               |  !RPCut   |  !RecoMCTruthLink,  !ZVRESDecayChains  | !FTSelectedJets  |
   |   !MyFlavourTagInputs     |  !FlavourTagInputs  | !ZVRESDecayChains,  !FTSelectedJets | !FlavourTagInputs   |

Our input =slcio= files contain the collections: !LooseSelectedPandoraPFANewPFOs, !MCParticlesSkimmed, !PandoraPFANewClusters, !PandoraPFANewPFOs, !PandoraPFANewReclusterMonitoring, !ProngVertices, !RecoMCTruthLink, !SelectedLDCTracks, !SelectedPandoraPFANewPFOs, !TightSelectedPandoraPFANewPFOs  and !V0Vertices.
  
The processors listed above could be run in sequence, or split in several steps, invoking a *LCIOOutput* processor to write intermediate =slcio= outputs at every step. Here's [[%ATTACHURLPATH%/runLCFI.txt][a script]] for that. We found that the most [[%ATTACHURLPATH%/Timing-ScreenShot.png][time-consuming]] processor is *ZVTOP_ZVRES* with more than 10 s/event.

The *LCIOOutput* processor creates new =slcio= files containing the new collections added by the above processors. 

*Troubleshooting:* The =b3_D0CutValue= parameter of the !IPRPCutProcessor was set to =5O= instead of =50=, and was causing a crash. For the !ZVRESRPCut processor, =h1_MCPIDEnable= had to be set to =false=. 

---+++ Neural Network Training

The =slcio= files created at the previous step contain the collections *Durham_4Jets*, *FlavourTagInputs* and *TrueJetFlavour_4Jets*, which we will use now to train our neural nets. We use the =NeuralNetTrainer= code included in the LCFI package. Separate nets were trained for 1, 2, or 3+ vertices to identify b-jets, c-jets, and c-jets with b background. Our steering file contains only:

<verbatim>
  <processor name="MyNeuralNetTrainer" type="NeuralNetTrainer"/>
</verbatim>

The neural nets are saved as XML files in =nnets/= and will be used for flavour tagging (next step). No =slcio= output is written at this time. 

---+++ Purity and Efficiency Studies

To determine the optimal cut for our b-tagging, a purity vs. efficiency study was performed. 

---+++ Flavour Tagging

Now are ready to employ the *FlavourTag* processor, which will do flavour tagging using the neural nets trained in the previous step. Our steering file contains the following processors:
 
<verbatim>
  <processor name="MyFlavourTag"/>
  <processor name="ZZfusion"/>
</verbatim>

The *ZZfusion* processor is used in our analysis.

---+++ Acceptance Studies


---+++ Electrons from Hard Bremsstrahlung

---+++ Luminosity and Event Weights

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
png	BRTotalUncertBands_lm.png	r2 r1	manage	111.7 K	2013-07-01 - 14:41	DanProtopopescu	Higgs branching ratios (from A. Denner et al., EPJ C71, p.1753)
pdf	LCFI_Flow_Diagram.pdf	r1	manage	87.7 K	2013-07-01 - 16:10	DanProtopopescu	LCFI processors - flow diagram
png	Timing-ScreenShot.png	r1	manage	70.9 K	2013-07-01 - 16:03	DanProtopopescu	Screen shot: time used by Marlin processors
pdf	Vertexing_Howto.pdf	r1	manage	743.5 K	2013-07-01 - 16:52	DanProtopopescu	Vertexing HowTo (Ben Jeffery)
xml	jet_truth_tag-steer.xml	r1	manage	82.1 K	2013-07-01 - 17:20	DanProtopopescu	Steering file 1: jet finder and truth flavour tagging
txt	runLCFI.txt	r1	manage	1.1 K	2013-07-04 - 16:15	DanProtopopescu	Script to run LCFI sequence of processors

Topic revision: r7 - 2013-07-04 - DanProtopopescu

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