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…