I used Madgraph to create a simulation of some events. I then went on ROOT to view the tree and the branches of that event and run. (In the prompt I typed TBrowser b) When I look at the Tree and the branches I only see the Muon Branch with the Muon.PT, Muon.Eta, Muon.Phi, etc. leaves. Looking at different tutorials on plotting the histogram of the invariant mass of the Z boson, I see that the trees and branches have two different muons. For example, there are branches such as LooseMuonsEta1, LooseMuonsPhi1, LooseMuonsPt1, LooseMuonsEta2, LooseMuonsPhi2, LooseMuonsPt2 in which they can use SetPtEtaPhiM to create a TLorentzVector out of it and in turn find the invariant mass of the Z boson. How can I create these (two) different branches to plot the invariant mass of the Z boson? This is what I have attempted after reading some tutorials, but I ended up with an empty histogram. > #ifdef __CLING__ > > R__LOAD_LIBRARY(libDelphes) > > #include "classes/DelphesClasses.h" > > #include "external/ExRootAnalysis/ExRootTreeReader.h" > > #include "external/ExRootAnalysis/ExRootResult.h" > > #else > > class ExRootTreeReader; > > class ExRootResult; > > #endif > > template > > void CollectionFilter(const TClonesArray& inColl ,vector& outColl, Double_t ptMin=30, Double_t etaMax=2.5) > > { > > const TObject *object; > > for (Int_t i = 0; i < inColl.GetEntriesFast(); i++) > > { > > object = inColl.At(i); > > const T *t = static_cast(object); > > if(t->P4().Pt() < ptMin) continue; > > if(TMath::Abs(t->P4().Eta()) > etaMax) continue; > > outColl.push_back(t); > > } > > } > > //-------------------------------------Looking at Leptons ----------------------------------------- > > void numberOfMuons(const char *inputFile) > > { > > gSystem->Load("libDelphes"); > > // Create chain of root trees > > TChain chain("Delphes"); > > chain.Add(inputFile); > > // Create object of class ExRootTreeReader > > ExRootTreeReader *treeReader = new ExRootTreeReader(&chain); > > Long64_t numberOfEntries = treeReader->GetEntries(); > > // Get pointers to branches used in this analysis > TClonesArray *branchMuon = treeReader->UseBranch("Muon"); > > > > // Book histograms > > > TH1F *Zmass = new TH1F("mass", "M_{inv}(Z[1]); M_inv (GeV/c^2); Events", 50, 0.0, 150); > > TH1F *ZmassBkg = new TH1F("mass", "M_{inv}(Z[1]); M_inv (GeV/c^2); Events", 50, 0.0, 150); > > //Create NTuple > > > > TTree* tree =&chain; > > TTree* ntuple = new TTree("NTuple", "Finding Number of Particles"); > > Int_t numberOfMuons; > > Int_t numberOfParticles; > > // Create local variables for the tree's branches > > Float_t MuonPT1; > > Float_t MuonEta1; > > Float_t MuonPhi1; > > Float_t MuonM; > > Float_t MuonPT2; > > Float_t MuonEta2; > > Float_t MuonPhi2; > > > > //Set the tree's branches to the local variables > > > > tree->SetBranchAddress("MuonPT1", &MuonPT1); > > tree->SetBranchAddress("MuonEta1", &MuonEta1); > > tree->SetBranchAddress("MuonPhi1", &MuonPhi1); > > tree->SetBranchAddress("MuonPT2", &MuonPT2); > > tree->SetBranchAddress("MuonEta2", &MuonEta2); > > tree->SetBranchAddress("MuonPhi2", &MuonPhi2); > > > > // Assign each variable to its own branch > > ntuple->Branch("numberOfMuons", &numberOfMuons, "numberOfMuons/I"); > > // Loop over all events > > for(Int_t entry = 0; entry < numberOfEntries; ++entry) > > { > > // Load selected branches with data from specified event > > treeReader->ReadEntry(entry); > > > > > > //Muons > > for( Int_t i = 0; i < branchMuon->GetEntries(); ++i) > > { > > > > cout << "There are " << numberOfMuons << " muons in run" << endl; > > } > > > > if(abs(MuonPT1) < 20) continue; > > if(abs(MuonEta1) > 2.5) continue; > > if(abs(MuonPT2) < 20) continue; > > if(abs(MuonEta2) > 2.5) continue; > > TLorentzVector Muon1; > > Muon1.SetPtEtaPhiM(fabs(MuonPT1), MuonEta1, MuonPhi1, 0.1); > > TLorentzVector Muon2; > > Muon2.SetPtEtaPhiM(fabs(MuonPT2), MuonEta2, MuonPhi2, 0.1); > > > > TLorentzVector Z = Muon1 + Muon2; > > > > Zmass->Fill(Z.M()); > > > > } > > Zmass->Draw(); > > } > > ___ I would appreciate any guidance. Many thanks!

When	Who	Action	New State
2020-02-11	Olivier Mattelaer	Answer	Answered
2020-02-12	User New	Reopen	Open
2020-02-12	Olivier Mattelaer	Answer	Answered

MadGraph5_aMC@NLO

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