void Trans_mass()
{
TCanvas *c1 = new TCanvas("c1","transverse mass",800,600);
c1->Divide(1,1);
TFile *F = new TFile("May26_2.root");
TTree *AnaTree1 = (TTree*)F->Get("demo/AnaTree");
TH1F *h1 = new TH1F("h1","transverse mass",500,0,1000);
Float_t mt, met_pt, met_phi;
TLorentzVector met(0,0,0,0), mu_neutrino(0,0,0,0);
TLorentzVector mu_neutrinoPz;
//met.SetPtEtaPhiM(ev.met_pt,0,ev.met_phi,0.);
//met.SetPz(0.); met.SetE(met.Pt());
//met_pt = ev.met_pt;
AnaTree1->SetBranchAddress("mt",&mt);
AnaTree1->SetBranchAddress("met_phi",&met_phi);
AnaTree1->SetBranchAddress("met_pt",&met_pt);
Long64_t nentries = AnaTree1->GetEntries();
for (int i=0;i<233428;i++)  {
AnaTree1->GetEntry(i);
met.SetPtEtaPhiM(met_pt,0,met_phi,0);
met.SetPz(0);
met.SetE(met.Pt());
met_pt = met_pt[0];
//mu_neutrino.SetPtEtaPhiM(
//TLorentzVector mu_neutrinoPz;
//mu_neutrinoPz.SetMET(met);
//mu_neutrinoPz.SetLepton(mup4_w);
float mu_nupz; //=mu_neutrinoPz.Calculate();
float mu_nuE = sqrt( met.Px()*met.Px() + met.Py()*met.Py() + mu_nupz*mu_nupz);
mu_neutrino =  TLorentzVector(met.Px(), met.Py(), mu_nupz, mu_nuE );

double transverse = (mu_neutrino+met).Mt();
h1->Fill(transverse);
}
h1->Draw();
}