analyze_pp_elastic.C

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{
 
    //Analyze the output of pp_elastic.C
 
    TFile *f = (TFile*)gROOT->GetListOfFiles()->FindObject("pp_elastic.root");
    if (!f) {  f= new TFile("pp_elastic.root"); }
    TTree *Reaction = (TTree*)gDirectory->Get("data");
    TClonesArray *evt = new TClonesArray("PParticle", 3);
    Reaction->SetBranchAddress("Particles", &evt);
 
    const double r2d=180./3.14159265358979323846; 
    PParticle *par[3];
    TH1F *hf1=new TH1F("hf1", "#Theta_{lab} (deg.)", 20, 0, 0.9);
    TCanvas *can = new TCanvas("canvas", "pp elastic", 200, 10, 600, 400);
    can->SetLogy(1);
    Int_t nentries = Reaction->GetEntries();
    for (Int_t i=0; i<nentries; i++) {
    Reaction->GetEntry(i);
    par[0] = (PParticle*)evt->At(0);
    par[1] = (PParticle*)evt->At(1);
    par[2] = (PParticle*)evt->At(2);
    par[1]->Boost(-par[0]->BoostVector());
    par[2]->Boost(-par[0]->BoostVector());
    hf1->Fill(fabs(cos(par[1]->Theta())));
    } 
    hf1->Draw(); 
}