How to save the deltaR between muon decays

FCCAnalysis
1

I am running some BSM event collisions with a Higgs and A3 particle decay with a professor of mine. Are there any suggestions on how to save the deltaR = sqrt(deltaEta^2 + deltaPhi^2) between the two generated muons from the A3 decay?
I figured it may be a similar framework to the ResonanceBuilder called in the analysis.py file but am unsure where to start with doing this.

Thanks,
Hayden Shaddix

2

Hi Hayden,

The general answer is that you should indeed implement a new function that calculates the quantity you are interested in. You can take a look at the short paragraph “Code development” here:

https://github.com/HEP-FCC/FCCeePhysicsPerformance/tree/master/General#code-development

which gives a few indications.

You can also look at example functions that already exist in analyzers/dataframe/MCParticle.cc. If you need to navigate through the history of the MC event, e.g. to check the parent of the muons, you can take a look at:

https://github.com/HEP-FCC/FCCAnalyses/blob/basicexamples/examples/basics/README.md#Navigation-through-the-history-of-the-Monte-Carlo-particles

In some particular cases, for example if your MC file always contains only one mu+ and only one mu-, that come from the a3 decay, you could get your deltaR without having to code anything, for example:

           .Define("stable",  "MCParticle::sel_genStatus(1) ( Particle )")
           .Define("Muminus",  "MCParticle::sel_pdgID( 13, false) ( stable )")
           .Define("Muplus",  "MCParticle::sel_pdgID( -13, false) ( stable )")
           .Define("Muminus_tlv", "MCParticle::get_tlv( Muminus ) ")
           .Define("Muplus_tlv", "MCParticle::get_tlv( Muplus ) ")
           .Define("deltaR", "return Muminus_tlv[0].DeltaR( Muplus_tlv[0] ) ; ")

and then you add “deltaR” to the list of output branches. If you want to protect yourself against cases where no muon was retrieved, you can do e.g.:

           .Define("deltaR", " if ( Muminus_tlv.size() > 0 && Muplus_tlv.size() > 0) return Muminus_tlv[0].DeltaR( Muplus_tlv[0] ) ; else return -9999. ;  ")

but as you see, this easily gets clumsy and C++ code may be better.

Cheers,
E.