Invariant Mass

[Qazi-Murad]

Question

Dear All, I am working in mass reconstruction for new physics particle. For hadronically decaying leg, I already got some good histograms using MA5. Now for leptonically decaying leg, I made some calculation and plug it into MA5. I am trying to produce histograms for the invariant mass of one lepton plus 2 b-jet plus neutrino. First I calculated the z component related to neutrino as follow; double mW = 80; then some variable related to z-component (I am putting ..... for simplicity as it represent some values present in the code ) double A = ..... double F = ...... double G = ....... then define z-component as double missing_pz = F+sqrt(pow(F,2),G); then also define the E component double missing_E = ....... then I define : MALorentzVector Neutrino(pTmiss.Px(), pTmiss.Py(), missing_pz, missing_E); and then : double mdq = (SignalMuons[0]->momentum() + SignalBJets[0]->momentum() + SIgnalBJets[1]->momentum() + Neutrino->momentum()).M(); Where mdq represent the invariant mas. After compiling it gives an error related to the Neutrino part in the above line. The error: base operand of ‘->’ has non-pointer type ‘MA5::MALorentzVector’. I belive I am missing some step but I don't know where. Any advise or suggestion, what should I do? or what type of changes should I make? So that Neutrino vector also works like other and I get the invariant mass.

[jackaraz]

Hi @Qazi-Murad, I feel like you haven't defined your neutrino as a pointer, so Neutrino.momentum() might work.

[Qazi-Murad]

Hi @jackaraz, Following your suggestion I get the error: ‘class MA5::MALorentzVector’ has no member named ‘momentum’. I attached the two files .cpp and header. Can you just look at where I have made a mistake? The code we are discussing starts from line 199 in the .cpp file. Other stuff is not related to the leptonically decaying leg, so comment on it. Files.zip

[jackaraz]

Ah, I see the issue. It's a Lorentz vector, not a particle; hence, it does not have momentum. Momentum itself is a Lorentz vector.

[Qazi-Murad]

So should I define it as a particle, like I define SignalJets or Signal Muons? But how since it is a neutrino? If possible, Can you make changes to the files?

[jackaraz]

You are dealing with four-momentum of particles. The only difference between a particle and a four-momentum is the particle's charge and identity. Since you don't need those, I don't see the reason why you would need to write it as a particle.

[Qazi-Murad]

So what should I do? I need to produce invariant mass from neutrino plus muon plus 2b-jet.

[jackaraz]

you are adding up Lorentz vectors, and your neutrino object is a Lorentz vector.