Mother Branch in Simulations

[Savannah]

I've been working with one of the ZJETS 14 TeV no pileup samples and we had some questions about how the particle branch is filled. What exactly do the mother numbers m1 and m2 and daughter numbers d1 and d2 signify? The position of the mother/daughter particles in the particle array for that event? In that case, what do numbers like 299 for the mother mean? Additionally, I noticed in some cases, mother and daughters don't match up. For instance in the event below, particle 10 lists daughters 12 and 13 but particle 13 lists is mother as 13. What does that mean? Which is correct? Thanks!

event number 4527
array index 0 status 3 pid 1 ispu 0 m1 0 m2 -1 d1 -1 d2 -1 Pt 2.30323 eta 6.69588 phi -1.47905
array index 1 status 3 pid 2 ispu 0 m1 1 m2 -1 d1 -1 d2 -1 Pt 1.24499 eta -7.50139 phi -1.53726
array index 2 status 3 pid 1 ispu 0 m1 2 m2 -1 d1 -1 d2 -1 Pt 4.72756 eta 5.16489 phi -0.114224
array index 3 status 3 pid 2 ispu 0 m1 3 m2 -1 d1 -1 d2 -1 Pt 3.7018 eta -5.79572 phi 0.677767
array index 4 status 3 pid 2 ispu 0 m1 4 m2 5 d1 -1 d2 -1 Pt 65.4117 eta -1.64857 phi -2.6392
array index 5 status 3 pid 1 ispu 0 m1 4 m2 5 d1 -1 d2 -1 Pt 25.0672 eta 3.46605 phi 0.0826737
array index 6 status 3 pid 23 ispu 0 m1 5 m2 6 d1 -1 d2 -1 Pt 50.6781 eta -2.8397 phi 0.663457
array index 7 status 3 pid -13 ispu 0 m1 8 m2 -1 d1 -1 d2 -1 Pt 38.2605 eta -2.36596 phi -0.937544
array index 8 status 3 pid 13 ispu 0 m1 8 m2 -1 d1 -1 d2 -1 Pt 64.4146 eta -1.98521 phi 1.29911
array index 9 status 2 pid 23 ispu 0 m1 8 m2 -1 d1 12 d2 13 Pt 50.6781 eta -2.8397 phi 0.663457
array index 10 status 2 pid -13 ispu 0 m1 9 m2 -1 d1 14 d2 15 Pt 38.2605 eta -2.36596 phi -0.937544
array index 11 status 2 pid 13 ispu 0 m1 10 m2 -1 d1 16 d2 16 Pt 64.4146 eta -1.98521 phi 1.29911
array index 12 status 1 pid -13 ispu 0 m1 12 m2 -1 d1 -1 d2 -1 Pt 30.38 eta -2.36509 phi -0.935926
array index 13 status 1 pid 13 ispu 0 m1 13 m2 -1 d1 -1 d2 -1 Pt 64.4144 eta -1.98521 phi 1.29911
array index 14 status 1 pid -13 ispu 0 m1 545 m2 -1 d1 -1 d2 -1 Pt 4.42552 eta -1.93129 phi -2.55388

[Pavel Demin]

Your description of the mother/daughter numbers is correct. They are indices of the particle array.

Could you, please tell us what input file format and what detector card are you using?

A similar problem was reported in tickets #194 and #205.

In the detector card developed by the Snowmass group, the StatusPidFilter module is configured to filter out some of the MC truth particles.

As some of the MC truth particles are removed from the Particle branch, the indices are not valid anymore.

Is it possible that your detector card is also using StatusPidFilter module?

[Savannah]

The file I'm looking at used the delphes_card_Snowmass_NoPileUp.tcl detector card, so I'm guessing its because some of the particles are removed. Is there a way to reconstruct the individual decays properly in that case? Or to find the accurate mother/daughter numbers

[Pavel Demin]

I've just looked found the delphes_card_Snowmass_NoPileUp.tcl at

​http://cmssw.cvs.cern.ch/cgi-bin/cmssw.cgi/UserCode/spadhi/Snowmass/Cards/delphes_card_Snowmass_NoPileUp.tcl

This card indeed uses the StatusPidFilter module.

I'm afraid that all the mother/daughter information is lost in this case.

The only solution that I can propose is to slightly modify the card an to rerun Delphes.

To keep all the particles in the output file you should uncomment

  add Branch Delphes/allParticles Particle GenParticle

and comment

  add Branch StatusPid/filteredParticles Particle GenParticle