Histograms

1
Histograms
2
Objectives

• After completing this lesson, you should be able
  to
• Book and fill histograms.

3
Histograms

• One of they key tools in HEP
• Wheel not being reinvented
• Usage and function closely matching HBOOK
• book fill
• Kept in TDS in their own areas
• /stat
• managed by HistogramSvc
• Persistency
• HBOOK
• ROOT

4
Histograms - Good To Know...

• Histograms are kept in special TDS area
• unlike the event, it is not cleared with each new
  event
• same access mechanism as other objects in TDS
• If not saved - they are lost
• histograms are kept in memory
• must be registered with the TDS and saved at end
  of job

5
Booking 1-d Histograms

• Through the Histogram service
• IHistogram1D multiplicityH1D
• histoSvc()-gtbook("/stat/myhist/,1,
• "Visible chargedMultiplicty",
• 100,
• 0,
• 1000.0)

6
Booking 2-d Histograms

• Through the Histogram service
• IHistogram2D multiplicityVsEnergyH2D
• histoSvc()-gtbook(/stat/myhist/,2,
• "MultiplictyvsEnergy(GeV)",
• 100,
• 0.0,
• 1000.0,
• 50,
• 0.0,
• 500.0)

7
Filling Histograms
Calls similar to HBOOK HF1 HF2
8
Generic Histogram Access

• Its just another data store object
• const DataHandleltIHistogram1Dgt h1d
• m_sgSvc?retrieve(h1d , /stat/my1Dhist/3)
• h1d-gtfill( value, weight)
• Or book on the fly
• IHistogram1D h1d histoSvc()-gtbook(
• /stat/my1Dhist,
• lthistgt,
• Title,
• ltbinsgt,
• ltlowegdegt,
• lthighedgegt)

9
Histogram Persistency

• In jobOptions file
• Load the relevant shared library
• ApplicationMgr.DLLs HbookCnv/
  RootHistCnv
• Specify persistency (accordingly to shared lib)
• ApplicationMgr.HistogramPersistency
• HBOOK / ROOT / NONE (default)
• Specify name of output file, e.g.,
• HistogramPeristencyService.OutputFile
  atlfast.hbook / atlfast.rt

Already done in your jobOptions.txt
10
Hands On Histograms

• In AnalysisSkeleton.h
• Add forward declaration
• class IHistogram1D
• class IHistogram2D
• Add start number for histograms ID
• int m_histStart
• Declare histograms
• IHistogram1D m_hist_pT
• IHistogram1D m_hist_isolation
• IHistogram2D m_hist_cellFlow
• IHistogram2D m_hist_clusterFlow

11
Hands On Histograms

• in AnalysisSkeleton.cxx
• Include header files
• include "GaudiKernel/IHistogramSvc.h"
• include "GaudiKernel/IHistogram1D.h
• include "GaudiKernel/IHistogram2D.h"
• Declare histogram ID start number
• declareProperty(HistStart, m_histStart)
• In the jobOptions, specify it
• e.g.
• AnalysisSkeleton.HistStart 1000

12
Hands On Histograms

• In initialize( )
• Book histograms
• m_hist_pT histoSvc()-gtbook(/stat/athena/",
• m_histStart, pT, 40, 0.0, 500.0)
• m_hist_isolation histoSvc()-gtbook(/stat/athena/
  ", m_histStart, Isolation eT, 40, 0.0,
  100.0)
• m_hist_clusterFlow histoSvc()-gtbook(/stat/athen
  a/", m_histStart, Cluster E flow",40, -3.0,
  3.0,
• 40, -3.14159, 3.14159)
• m_hist_cellFlow histoSvc()-gtbook(/stat/athena/"
  , m_histStart, Cell E flow",40, -3.0, 3.0,
• 40, -3.14159, 3.14159)

13
Hands On Histograms

• In particle iteration of dumpParticles( ), fill
  pT hist
• Add plotting of pT (needless to say after double
  pT assignment)
• m_hist_pT-gtfill(pT, 1.0)
• Add new private member functions
• Include collection typedefs (in
  AnalysisSkeleton.h)
• include AtlfastCode/CellCollection.h
• include AtlfastCode/ClusterCollection.h
• void plotIsolation(MsgStream,
• ReconstructedParticleCollection,
• CellCollection)
• void plotEnergyFlow(MsgStream,
• ClusterCollection,
• CellCollection)

We might had instead const DataHandleltReconstruct
edParticleCollectiongt or const
DataHandleltObjectVectorltReconstructedParticlegt gt
14
Hands On Histograms

• In execute( ), after the call to dumpParticles( )
  
• Plot isolation from Cells
• if (particles-gtsize( ) cells-gtsize( ))
  plotIsolation(log, particles, cells)
• Plot E-flow for Clusters Cells in a single
  event
• if (clusters-gtsize( ) cells-gtsize( ))
  plotEnergyFlow(log, clusters, cells)

15
Hands On Histograms

• In plotIsolation( ), calculate energy in a cone
  around each particle, and plot it. We will use
  Atlfast machinery provided by the IKinematic
  interface.
• Inside an iteration on particles
• double esum m_kinehelp.sumETInCone(
• cells-gtbegin(),
• cells-gtend(),
• theParticle,
• m_rCellIsolation)
• Subtract the eT of the particle itself
• esum - (theParticle)-gteT()
• and fill histogram
• m_hist_isolation-gtfill(esum, 1.0)

16
Hands On Histograms

• In plotEnergyFlow( ), for one event only.
• (dumb way to select count events, set here to
  3rd)
• static int nevent nevent
• if (3 ! nevent) return
• log ltlt MSGINFO ltlt Energy flow for event ltlt
  nevent ltlt endreq
• //Plot Cell energy flow
• CellCollectioniterator cell
• for(cell cells-gtbegin( ) cell lt cells-gtend( )
  cell)
• m_hist_cellFlow-gtfill( (cell)-gteta( ),
• (cell)-gtphi( ),
• (cell)-gteT( ) )
• //Plot Cluster energy flow
• ClusterCollectioniterator cluster
• for(cluster clusters-gtbegin( )cluster lt
  clusters-gtend( ) cluster)
• m_hist_clusterFlow-gtfill( (cluster)-gteta( ),
• (cluster)-gtphi( ),
• (cluster)-gteT( ) )

17
Hands On Histograms

• Compile, link and run athena
• See histograms with PAW
• paw

PAWgt hi/file 1 atlfast.hbook PAWgt cd athena PAWgt
hi/list PAWgt hi/pl 1000 PAWgt hi/pl 1001 PAWgt
hi/pl 1002 PAWgt hi/pl 1003 PAWgt quit