void lv_mass()
{
    TCanvas *c1=new TCanvas();
    TCanvas *c2=new TCanvas();
    c1->Divide(2,2);
    c2->Divide(2,2);
    TH1F *histm=new TH1F("histm","mass",1000,100,2000);
    TH1F *histpx=new TH1F("histpx","px",100,0,12);
    TH1F *histpy=new TH1F("histpy","py",100,0,12);
    TH1F *histpz=new TH1F("histpz","pz",100,0,12);
    TH1F *histpt = new TH1F("histpt","pt",500,0,20);
    TRandom2 *random= new TRandom2(1);
     double_t px, py, pz,p,trans, e,m,energy;
     
     for (int i=1; i<=10000; i++){
     
      TF1 *f1 = new TF1("f1","[0]*TMath::Power(([1]/[2]),(x/[2]))*(TMath::Exp(-([1]/[2])))/TMath::Gamma((x/[2])+1)",.02,12);// use this for user defined random poisson value 
       f1->SetParameters(1,1,1);
    m = gRandom->Uniform(0,2000);
  //  m=random->Gaus(1000,40);
     px = f1->GetRandom();                       
     py = f1->GetRandom(); 
     pz = f1->GetRandom(); 
     p = sqrt(px*px+py*py+pz*pz);
     trans = sqrt(px*px+py*py);
    e = gRandom->Uniform(0,2000);   

     energy=sqrt(px*px+py*py+pz*pz+m*m);

  histm->Fill(m);
  histpx->Fill(px);
  histpy->Fill(py);
  histpz->Fill(pz);
  histpt->Fill(trans);
   }
   
   TLorentzVector v;
         v.SetPxPyPzE(px,py,pz,energy);
        cout<<"X-component of momentum using lorentz vector= "<<v.Px()<<endl; 
        cout<< "Y-component of momentum using lorentz vector= " <<v.Py()<< endl; 
        cout<<"Z-component of momentum using lorentz vector= " <<v.Pz()<<endl; 
        cout << "Energy using lorentz_vector=  " <<v.E()<<endl; 
         double mass = v.M();
         cout<<"mass="<<mass<<endl; 
         
   TLorentzVector v1;
         v1.SetPxPyPzE(px,py,pz,e);  
         double mass_1 = v1.M();
         cout<< "mass_1="<<mass_1<<endl;    
    
        mass=sqrt(e*e-p*p);
        cout<<"mass from formula   "<<mass<<endl;
          double_t mag, theta, phi, pt, eta;
          mag= v.Rho();
          theta=v.Theta()*180/TMath::Pi();  // we have  multiply this with 180/pi to convert it to degree
          phi = v.Phi();
          pt =  v.Perp();
          eta = v.PseudoRapidity();
        //   cout <<" Magnitude of selected  lorentz vector:  "<< mag << "  THETA: " << theta << "   PHI:" << phi << "   Pt By Lorentz: "<< pt << "   Pseudorapidity: " << eta<< endl;

   c1->cd(1);   
   histm->Draw();
   c2->cd(1);
   histpx->Draw();
   c2->cd(2);
   histpy->Draw();
   c2->cd(3);
   histpz->Draw();
   c2->cd(4);
   histpt->Draw();
   
    }