WorkBookOfflinePrimaryVertexFinding < CMSPublic

CMSPublic Web>SWGuide>WorkBook>WorkBookVertexReco>WorkBookOfflinePrimaryVertexFinding (2010-08-06, SudhirMalik) (raw view)

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---+ 7.3.1 Offline Primary Vertex Finding
%COMPLETE5%
%BR%
[[#ReviewStatus][Detailed Review status]]

---++Contents

   * [[#PrimVtxReco][Primary Vertex reconstruction]]
   * [[#PrimVtxAnalysis][Vertex reconstruction analysis]]
   * [[#ReviewStatus][Review status]]

#PrimVtxReco
---++ Primary Vertex reconstruction

The reconstruction of Primary vertices using the full tracks is part of the default reconstruction sequence. It is done using the ==generalTracks== track collection.
The vertices are stored in the event as reco::Vertex collections.
Two collections are stored in the event:
   * ==offlinePrimaryVertices== : The standard vertex collection, where the ==offlineBeamSpot== is used to filter the tracks. This is the collection which we advise to use.
   * ==offlinePrimaryVerticesWithBS== : For this collection, the ==offlineBeamSpot== is used not only to filter the tracks, but also as an additional constraint in the fit. It improves the resolution of the vertices, but we do not yet advise to use it until further robustness studies are done, especially for the initial conditions.

Opening a data file in root, the data of the primary vertices (such as the coordinates, chi-squared, degrees of freedom) can be viewed direclty.
More information on how to redo the primary vertex reconstruction is given [[SWGuideOfflinePrimaryVertexProduction][in the offline guide]].

From CMSSW 1.8.0 onwards, if no reconstructed vertex is found in an event using the tracks, a vertex based on the [[SWGuideFindingBeamSpot][beam-spot] is put into the event. In this case, the vertex contains no tracks (as non have been used) , the chi^2 and the ndof are 0, and the flag ==isFake()== is set to true.


#PrimVtxAnalysis
---++ Vertex reconstruction analysis

In cmsRun mode, the primary vertices can be analyzed with the !CMS.PrimaryVertexAnalyzer module by running
[[http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/CMSSW/Validation/RecoVertex/test/demoAnalyzePrimaryVertex_cfg.py?view=log][demoAnalyzePrimaryVertex_cfg.py]]:</noautolink>

==cmsRun demoAnalyzePrimaryVertex_cfg.py==

in the same directory. A root histogram file =simpleVertexAnalyzer.root= is produced, that, in addition to histograms of the fitted position, covariance, chi2 and degrees of freedom, also contains results of sanity checks of the number of valid track links and invalid fit parameters. 

==root simpleVertexAnalyzer.root== %BR%
==pullx->Draw()== %BR%
==eff->Draw()== %BR%
==nans->Draw()== %BR%


A simple test of the input track parameters is done by 

==cmsRun demoAnalyzeTracks_cfg.py==

which produces histograms of track parameter pulls. For instance, to look at curvature and z0:

==root simpleTrackAnalyzer.root== %BR%
==pull0->Draw()== %BR%
==pull4->Draw()== %BR%

#ReviewStatus
---++ Review status

| *Reviewer/Editor and Date (copy from screen)* | *Comments* |
| Main.werdmann - 04 Dec 2006 | update |
| Main.ThomasSpeer - 11 Feb 2008 | update |
| Main.ThomasSpeer - 16 Sep 2008 | update for 2.1.X |

%RESPONSIBLE% !ThomasSpeer %BR%
%REVIEW% !ThomasSpeer - 16 Sep 2008

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who	Comment
cff	OfflinePrimaryVerticesFromCTFTracks.cff	r1	manage	0.2 K	2006-07-19 - 10:58	UnknownUser	.cff for vertices from CTF tks
txt	OfflinePrimaryVerticesFromCTFTracks_cff.txt	r1	manage	0.2 K	2006-07-27 - 22:32	AnneHeavey	.cff for vertices from CTF tks
cff	OfflinePrimaryVerticesFromRSTracks.cff	r1	manage	0.2 K	2006-07-19 - 10:57	UnknownUser	.cff for vertices from RS tks
txt	OfflinePrimaryVerticesFromRSTracks.cff.txt	r1	manage	0.2 K	2006-07-27 - 22:31	AnneHeavey	.cff for vertices from RS tks
txt	analyzePrimaryVertex_cfg.txt	r1	manage	0.4 K	2006-07-28 - 17:44	AnneHeavey
txt	analyzeTracks_cfg.txt	r1	manage	0.4 K	2006-07-28 - 17:46	AnneHeavey
txt	demoAnalyzePrimaryVertex.cfg.txt	r1	manage	0.8 K	2006-11-17 - 12:05	UnknownUser
txt	demoProducePrimaryVertex.cfg.txt	r1	manage	1.2 K	2006-11-17 - 11:25	UnknownUser
jpg	dx.jpg	r1	manage	17.3 K	2006-06-07 - 16:59	VanlaerPascal
jpg	dz.jpg	r1	manage	16.8 K	2006-06-07 - 16:56	VanlaerPascal
jpg	ndf.jpg	r1	manage	16.1 K	2006-06-07 - 17:01	VanlaerPascal
cfg	producePV.cfg	r1	manage	0.6 K	2006-07-19 - 09:50	UnknownUser	.cfg file for offline p.v. production from already produced tracks
txt	producePV_cfg.txt	r1	manage	0.6 K	2006-07-27 - 22:29	AnneHeavey	.cfg file for offline p.v. production from already produced tracks
c	pv.C	r1	manage	0.4 K	2006-06-16 - 18:29	VanlaerPascal
c	pv080.C	r1	manage	0.6 K	2006-07-10 - 14:39	UnknownUser	pv inspection in FWLITE, cmssw 080_pre3
c	pv111.C	r2 r1	manage	0.4 K	2006-11-15 - 12:21	UnknownUser
gif	pvx.gif	r2 r1	manage	7.8 K	2006-07-18 - 10:00	UnknownUser	x-residuals, cmssw_080_pre5
gif	pvz.gif	r2 r1	manage	8.0 K	2006-07-18 - 10:01	UnknownUser	z-residuals, cmssw_080_pre5
c	tracks.C	r1	manage	0.5 K	2006-06-07 - 14:18	VanlaerPascal
c	tracks080.C	r1	manage	0.8 K	2006-07-10 - 14:18	UnknownUser	track inspect in FWLITE, cmssw080_pre3