InDetAlignVertex

Primary Vertex Refit

Comments about the Primary Vertex Refit (as 13/Mar/07)

Originally, InDetLocalChi2AlignTools/RefitWithVertexTool uses iVertexFitter->fit(tracks) in its code. By doing this, one doesn't have a way to control where the primary vertex position is. Our proposal is to retrieve this primary vertex (VxPrimaryCandidate) from the default VxContainer where one has more control over the vertex constraints and many cuts can be applied.

Default Options for the BeamCondSvc:

  theApp.Dlls+=["InDetCondServices"] 
  BeamCondSvc=Service("BeamCondSvc")
  BeamCondSvc.useDB = True
  BeamCondSvc.posX = 0.      
  BeamCondSvc.posY = 0.      
  BeamCondSvc.posZ = 0.      
  BeamCondSvc.sigmaX = 0.015
  BeamCondSvc.sigmaY = 0.015
  BeamCondSvc.sigmaZ = 53.  

Then, from th jobOptions one can modify the following parameters:

  # To select Trk::FullVertexFitter (InDetFullVxFitterTool)
  InDetFlags.enableDefaultFullFinding()

  ToolSvc = Service("ToolSvc")
  ToolSvc.InDetPriVxFinderTool.useBeamConstraint = True
  ToolSvc.InDetPriVxFinderTool.minPt = 100.
  ToolSvc.InDetPriVxFinderTool.maxZ0 = 700.
  ToolSvc.InDetPriVxFinderTool.maxD0 = 5.
  ToolSvc.InDetPriVxFinderTool.maxD0overSigmaD0 = 100000000.
  ToolSvc.InDetPriVxFinderTool.useSiHitCut = 0
  ToolSvc.InDetPriVxFinderTool.maxChi2PerTrack = 100000.
  #ToolSvc.InDetPriVxFinderTool.OutputLevel = VERBOSE

  theApp.Dlls+=["InDetCondServices"] 
  BeamCondSvc=Service("BeamCondSvc")
  BeamCondSvc.useDB = False
  BeamCondSvc.posX = 0.      
  BeamCondSvc.posY = 0.      
  BeamCondSvc.posZ = 0.      
  BeamCondSvc.sigmaX = 0.015
  BeamCondSvc.sigmaY = 0.015
  BeamCondSvc.sigmaZ = 53.   

As one can see that the BeamConstraint can be applied or not using this those options. Futhermore, we have studied how the vertex position changes as a function of a dumping factor:

Where the dumping factor is:

  BeamCondSvc.sigmaX = 0.015 * _factor_
  BeamCondSvc.sigmaY = 0.015 * _factor_
  BeamCondSvc.sigmaZ = 53. * _factor_

Vertex Studies

One can estimate the position of the Primary Vertex removing all vertex constraints. To do that you can use the following lines:

   InDetFlags.enableDefaultFullFinding()

   ToolSvc = Service("ToolSvc")
   ToolSvc.InDetPriVxFinderTool.useBeamConstraint = False
   ToolSvc.InDetPriVxFinderTool.minPt = 100.
   ToolSvc.InDetPriVxFinderTool.maxZ0 = 700.
   ToolSvc.InDetPriVxFinderTool.maxD0 = 5.
   ToolSvc.InDetPriVxFinderTool.maxD0overSigmaD0 = 100000000.
   ToolSvc.InDetPriVxFinderTool.useSiHitCut = 0
   ToolSvc.InDetPriVxFinderTool.maxChi2PerTrack = 100000.

Using these lines one gets the following results:

Test on Multimuons

• Misalignment Know (Ideal case):
  • Vertex Candidate Position:
  • DoubleCone + 5k events:
• Misalignment Unknow (Nominal case):
  • Vertex Candidate Position:
  • DoubleCone + 5k events:

Comparations

• Reconstruction of Primary Vertex with Multimuons and MinBias events (talk):

First Comparations with/without Vertex Refit:

Comparations between Nominal Geometry with and without Vertex Refit:

• Comparation plots:
  • Hits:
  • Track Parameters:
  • Pixel Phi Residuals:
  • SCT Residuals:
• Full non-comparative analysis:
  • Nominal without Vertex Refit (40k events - 138054 tracks - 1193564 hits):
  • Nominal with Vertex Refit (40k events - 135359 tracks - 1171238 hits):

NOTE: Nominal Geometry + newTracking (GlobalChi2Fitter) + DoubleCone setup (Tracks and Hits limited to this setup)

-- CarlosEscobar - 13 Mar 2007