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Finding true vertex position of mother particles. [message #12101]

Mon, 20 June 2011 22:49

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *dip.t-dialin.net

Hi pandausers,

I'm trying to see true vertex position for psi3770 -> D+D- ->KpipiKpipi.

I have PndMCtracks and I don't have mother vertex ID.
At gridka, the signal data didn't contain mother particle info. as I correctly understand.
Simply I have only 6 charged outgoind tarcks with true 4-momentum.
From each three outgoing tracks, I can build intermediate state D+ or D- and can find first D+ or D- vertex position via.

Quote:

PndMCTrack *mctrack=(PndMCTrack*)mc_array->At(mc);
TVector3 vertex = (TVector3)mctrack->GetStartVertex();

Then now, I want to provide the vertex position for psi3770 from 4-momentum and vertex position of D+ and D-.
How can I get true vertex position only from PndMCtrack?

I assume that I need to build a TCandidate for true D+ and D-,
then I can get further mother decay.

Is there easy way to do with Rho package?

Thank you for your teaching....

Best wishes,
Donghee

[Updated on: Mon, 20 June 2011 22:52]

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Re: Finding true vertex position of mother particles. [message #12102 is a reply to message #12101]

Tue, 21 June 2011 09:47

Ralf Kliemt
Messages: 507
Registered: May 2007
Location: GSI, Darmstadt

first-grade participant

From: *pool.mediaWays.net

Hello Donghee,

The psi3770 you are looking at is a) a neutral particle and b) decaying "instantly". This means you have a) no mc track and b) no displaced vertex.
Hence the vertex of the decaying particles is the interaction point (or a point in the beam-target distributuion).

Regards,
Ralf

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Re: Finding true vertex position of mother particles. [message #12103 is a reply to message #12102]

Tue, 21 June 2011 09:59

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *dip.t-dialin.net

Dear Ralf.

What a simple solution!
That's great Thank you.

Regards, donghee

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Re: Finding true vertex position of mother particles. [message #12268 is a reply to message #12102]

Thu, 14 July 2011 14:30

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *kph.uni-mainz.de

Hi Ralf,

If I have interaction point (0,0,0), then I can find easily the vertex for MC true event.

But we have now some vertex displacement from beam-target smearing.
What is the way to get those info only from PndMCTrack?

I have only way to get such kind of info in terms of PndMcListConverter as an extra step after building pid, that I don't want to do so.

If you know more easy way to know vertex position for instant psi3770, please let me know.

Thanks.

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Re: Finding true vertex position of mother particles. [message #12270 is a reply to message #12268]

Thu, 14 July 2011 21:10

StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino

first-grade participant

From: *40-79-r.retail.telecomitalia.it

Hi,
this information is stored inside the MCEventHeader TClonesArray,not inside MCTrack.
Inside MCTrack you can however find StartVertex which is the production vertex of your particle, and this should also work. Of course if you produce some neutrals, i.e. lambda -> p pi, the start vertex of the charged particles will be different from the reaction vertex.

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Re: Finding true vertex position of mother particles. [message #12271 is a reply to message #12270]

Fri, 15 July 2011 11:11

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *kph.uni-mainz.de

Hi stefano,

I'm nearly come to the end.... could you say where I made wrong with below code (part of analysis code)

Quote:

//Data accessing!
TFile *inFile = TFile::Open(inSimFile,"READ");
TTree *tree=(TTree *) inFile->Get("cbmsim") ;

TClonesArray* mc_array=new TClonesArray("PndMCTrack");
tree->SetBranchAddress("MCTrack",&mc_array);
TClonesArray* event=new TClonesArray("FairMCEventHeader");
tree->SetBranchAddress("MCEventHeader",&event);

//Event loop
PndEventReader evr(inPidFile);
while (evr.GetEvent() && i++<nEntries)
{
tree->GetEntry(i);

//Event info
FairMCEventHeader *mc_info = (FairMCEventHeader*)event->At(i);

//Print to check
cout<<mc_info->GetX()<<endl;
cout<<mc_info->GetY()<<endl;
cout<<mc_info->GetZ()<<endl;
}

Error message in root is

Quote:

Error: illegal pointer to class object mc_info 0x0 3481

Cheers,
Donghee

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Re: Finding true vertex position of mother particles. [message #12272 is a reply to message #12270]

Fri, 15 July 2011 11:50

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *kph.uni-mainz.de

Hi stefano,

In interactive mode with TBrowser, I can see correct info from MCEventHeader(FairMCEventHeader), but I couldn't get anything via

Quote:

FairMCEventHeader *mc_info = (FairMCEventHeader*)event->At(i);

Simply I have zero entry from mc_info->GetEntriesFast();

So I do "NOT" understanding the way for using the FairMCEventHeader object in the simulation file.

I'm waiting for your teach
Donghee

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Re: Finding true vertex position of mother particles. [message #12273 is a reply to message #12272]

Fri, 15 July 2011 12:00

asanchez
Messages: 350
Registered: March 2006

first-grade participant

From: *kph.uni-mainz.de

Dear Donghee, could you attach the entire macro to see
into more detail how you proceed?
regards
Alicia.

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Re: Finding true vertex position of mother particles. [message #12274 is a reply to message #12271]

Fri, 15 July 2011 12:10

Tobias Stockmanns
Messages: 489
Registered: May 2007

first-grade participant

From: *ep1.ruhr-uni-bochum.de

Dear Donghee,

I think your branch name is not correct. It should be:

tree->SetBranchAddress("MCEventHeader.",&event);

Have a look in the TBrowser how it is written correctly.

Cheers,

Tobias

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Re: Finding true vertex position of mother particles. [message #12275 is a reply to message #12101]

Fri, 15 July 2011 12:23

Ralf Kliemt
Messages: 507
Registered: May 2007
Location: GSI, Darmstadt

first-grade participant

From: *pool.mediaWays.net

Hello Donghee,

I have a present for you Smile

  TFile* f = new TFile(inFile.Data()); // the sim file you want to analyse
  TTree* t=(TTree*)f->Get("cbmsim");
  
  FairMCEventHeader* evthead;
  t->SetBranchAddress("MCEventHeader.", &evthead);
  
  for (Int_t j=0; j<nEvents && j<t->GetEntriesFast(); j++)
  {
    t->GetEntry(j);
    if(verbosepoints) cout<<"Event No "<<j<<endl;
    else if (!(j%100)) cout <<"Event No "<<j<<endl;
    cout<<"GetRunID() "<<evthead->GetRunID()<<endl;
    cout<<"GetEventID() "<<evthead->GetEventID()<<endl;
    cout<<"GetX() "<<evthead->GetX()    <<endl;
    cout<<"GetY() "<<evthead->GetY()  <<endl;  
    cout<<"GetZ() "<<evthead->GetZ()   <<endl; 
    cout<<"GetT() "<<evthead->GetT()   <<endl; 
    cout<<"GetNPrim() "<<evthead->GetNPrim()  <<endl; 
  }// end for j (events)

Be reminded of the Branch name (thaks Tobias) and that the Event header is an object directliy inside the tree, like all the TClonesArrays.

Kind regards,
Ralf

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Re: Finding true vertex position of mother particles. [message #12276 is a reply to message #12275]

Fri, 15 July 2011 12:41

donghee
Messages: 385
Registered: January 2009
Location: Germnay

first-grade participant

From: *kph.uni-mainz.de

Hi Tobias and Ralf,

Thanks to Tobias for finding very tiny point at the end of naming "MCEventHeader." Smile

Thanks Ralf for your kind present. That is very fancy!
After replacing TCloneArray to directly FairMCEventHeader, that works perfectly. Finally I have got the way to know the true IP for psi...

Regards,
Donghee

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