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On Tue, 14 Oct 2014, [log in to unmask] wrote:

Hi Matt,

and others responsible for generated/simulated data, I have a question:

I took your data from:

/mss/hallb/hps/production/readout/tritrig-beam-tri/2pt2/

tritrigv1-egsv3-triv2-g4v1_s2d6-readout20140522_[1-10000].slcio

and from description I thought this was a right mix of trident data and beam background. However, I found some difficulty interpreting these files:

1. there is no distinction between "signal" (trident) and background, if you select events produced at t=0 and having no parents they are still not distinguishable completely (usually >3 particles/event);

For tridents, the signal particles should share a parent, and the parent should have PDG ID 622. There should be exactly one such trident in every event in the files you're looking at.

There may be other tridents ("background tridents") in the event, which will not be labeled in this way; if they occur in the same beam bunch as the signal trident, they can be identified in the way you describe.

Looking
            at this file, I do see the 622 parent & daughters...

tritrigv1-egsv3-triv2-g4v1_s2d6-readout20140522-recon20140614_1.slcio 

Here is a printout

=========================================================

…lots
            of brems & conversions…

MCP
            PDG ID = 11; time = 0.0

 
                          Parent =
            622

  
                                          Daughter = 11

MCP
            PDG ID = -11; time = 0.0

 
                          Parent =
            622

MCP
            PDG ID = 22; time = 0.704967737197876

 
                          Parent = 11

MCP
            PDG ID = 11; time = 0.0

 
                          Parent =
            622

  
                                          Daughter = 22

MCP
            PDG ID = 
              622; time = 0.0

  
                                          Daughter = 11

=========================================================

…and here’s the snippet used to create it…

List<MCParticle> mcpList=event.get(MCParticle.class,"MCParticle");

for(MCParticle mcp: mcpList){

System.out.println("MCP PDG ID = "+mcp.getPDGID()+"; time = "+mcp.getProductionTime());

if(mcp.getParents().size()>0)

System.out.println( "\t\tParent = "+mcp.getParents().get(0).getPDGID());

if(mcp.getDaughters().size()>0)

System.out.println( "\t\t\t\t Daughter = "+mcp.getDaughters().get(0).getPDGID());

}

2. even if you find a combination of 3 particles with close missing mass it is >10^-2 GeV (varying), while I expected <10^-4 GeV^2 (fixed).

Since tridents are produced at random Z within the target, they are affected by multiple scattering. Since we don't use SLIC to simulate target interactions, the MS is applied outside of SLIC, and so the particles listed in SLIC have already been smeared by MS.

Matt should confirm that the mass you're seeing is consistent with this explanation.

Not sure why this is…

Any suggestion?

Best Regards,
Mikhail.

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