Resonance Builder

ymahmoud · July 17, 2024, 11:32am

Hello everyone,

I am trying to reconstruct the HZZ to 4l. I know the “resonanceBuilder” function found in:

HEP-FCC/FCCAnalyses/blob/090542047ed93cad6eb62f45ee90c9fd7d7a715f/examples/FCCee/higgs/mH-recoil/mumu/analysis_stage1.py#L94C10-L96C79


      
          .Define(
              'zed_leptonic',
              'ReconstructedParticle::resonanceBuilder(91)(selected_muons)')

can get the 2 leptons that make the resonant Z.

What would I do if I want to get the rest of the reconstructed particles by removing the ones outputed “resonanceBuilder” so I can reconstruct the off-shell Z?

I tried 'ReconstructedParticle::remove() but it didn’t work.

jaeyserm · July 17, 2024, 12:37pm

Hi,

You need to know which leptons are selected by the resonanceBuilder algorithm. Unfortunately this function does not return it.

For the Higgs mass analysis I wrote a similar function that returns the selected leptons from the resonance builder. Have a look at:

github.com

HEP-FCC/FCCAnalyses/blob/master/examples/FCCee/higgs/mass_xsec/histmaker_recoil.py#L130


      
          ### CUT 2 :at least 2 opposite-sign (OS) leptons
          #########
          df = df.Filter("muons_no >= 2 && abs(Sum(muons_q)) < muons_q.size()")
          df = df.Define("cut2", "2")
          results.append(df.Histo1D(("cutFlow", "", *bins_count), "cut2"))
          
          # now we build the Z resonance based on the available leptons.
          # the function resonanceBuilder_mass_recoil returns the best lepton pair compatible with the Z mass (91.2 GeV) and recoil at 125 GeV
          # the argument 0.4 gives a weight to the Z mass and the recoil mass in the chi2 minimization
          # technically, it returns a ReconstructedParticleData object with index 0 the di-lepton system, index and 2 the leptons of the pair
          df = df.Define("zbuilder_result", "FCCAnalyses::ZHfunctions::resonanceBuilder_mass_recoil(91.2, 125, 0.4, 240, false)(muons, MCRecoAssociations0, MCRecoAssociations1, ReconstructedParticles, Particle, Particle0, Particle1)")
          df = df.Define("zll", "Vec_rp{zbuilder_result[0]}") # the Z
          df = df.Define("zll_muons", "Vec_rp{zbuilder_result[1],zbuilder_result[2]}") # the leptons 
          df = df.Define("zll_m", "FCCAnalyses::ReconstructedParticle::get_mass(zll)[0]") # Z mass
          df = df.Define("zll_p", "FCCAnalyses::ReconstructedParticle::get_p(zll)[0]") # momentum of the Z
          df = df.Define("zll_recoil", "FCCAnalyses::ReconstructedParticle::recoilBuilder(240)(zll)") # compute the recoil based on the reconstructed Z
          df = df.Define("zll_recoil_m", "FCCAnalyses::ReconstructedParticle::get_mass(zll_recoil)[0]") # recoil mass
          df = df.Define("zll_muons_p", "FCCAnalyses::ReconstructedParticle::get_p(zll_muons)") # get the momentum of the 2 muons from the Z resonance
          
          
          #########

It returns 3 ReconstructerdParticle objects: the Z resonance, the first and second selected lepton. You can use then these two leptons with the remove() function.

The resonanceBuilder_mass_recoil a more advanced resonance builder where you also have the constraint on the recoil in the second argument (125). To mimic the simple resonance builder, you can do:

resonanceBuilder_mass_recoil(91, 0, 0, 240, false)

Best,
Jan

ymahmoud · July 17, 2024, 2:20pm

Thank you @jaeyserm !

I think what I need is just part of this code.

Best regards,
Yehia