Empty muon branch in the root file

[Ozlem]

Hi,

I am trying to reconstruct an exclusive decay using delphes_card_CMS.tcl card. However, it appears that the Muon branch is empty. I am not sure if this information is being kept in somewhere else or I am failing to reconstruct muons. The version is 3.4.1.

Best, Ozlem

[Michele Selvaggi]

Are you sure you have muons with a large enough pT in your sample?
If needed you can attach a small event file and we can have a look.

[Ozlem]

Well, apparently no. I realized that muons cannot pass the cuts in the MuonEfficiency part. I have used the efficiency formula for tight muons and now I have the muons in the branch. However, I still cannot access the information for Muon.Particle which matches the reco particle to generated one. I don't have such information for the tracks too. So, I he two questions accordingly:

1) What is the way of doing a MC truth matching in Delphes?
2) What is the best way of reconstructing the decay chain from the reco tracks and muons ? Let's say I have such a B decay that in the final state, I have 2 kaons and muons, e.g, do I find a common reco vertex ?

Thanks

[Michele Selvaggi]

1) Every recoonstructed particle has a pointer to its GenParticle (MC truth) counterpart.
See examples/Example3.C for an example.
2) I would proceed at the MC truth level for that since Delphes does not reconstruct vertices as a default. You'll have to browse to the particle history and access X,Y,Z of particles in the Particle branch which correspond to the vertex. See examples/Example5.C for how to access the MC truth particle list.

[Ozlem]

Yes, I am aware of having that info is possible, e.g., as particle = (GenParticle*) muon->Particle.GetObject(); but my current problem is indeed accessing that info. The only info I am missing right now is the particle branch of my tracks and muons(so basically all my reco objects) is empty. Thus, I cannot get the MC truth info.

[Michele Selvaggi]

Well, if you want to access that information you'll have to lower the requirements on the MuonEfficiency and or the Isolation modules.

Put this parameter to 9999
​https://github.com/delphes/delphes/blob/master/cards/delphes_card_CMS.tcl#L554

And change the efficiency below 10 GeV to 1.00

​https://github.com/delphes/delphes/blob/master/cards/delphes_card_CMS.tcl#L534