NeutNtupleAnalyzer/DoHaloPhys.cc at master · TENorbert/NeutNtupleAnalyzer · GitHub

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/*Oct 31 2013
  Script for simulating assumption of Halo + Ghost
  TEN@UMN.EDU
*/


#include "TLorentzVector.h"
#include "TGenPhaseSpace.h"
#include "TH1.h"
#include "TH2.h"
#include "TCanvas.h"
#include "TFile.h"
#include "TF1.h"


void DoHaloPhys() {

  if (!gROOT->GetClass("TGenPhaseSpace")) gSystem.Load("libPhysics");

  TLorentzVector target(0.0, 0.0, 0.0, 0.938);
  TLorentzVector beam(0.0, 0.0, .65, .65);
  TLorentzVector W = beam + target;

  //(Momentum, Energy units are Gev/C, GeV)
  Double_t masses[3] = { 0.938, 0.139, 0.139} ;

  TGenPhaseSpace event;
  event.SetDecay(W, 3, masses);

  TH2F *h2 = new TH2F("h2","h2", 50,1.1,1.8, 50,1.1,1.8);

  for (Int_t n=0;n<100000;n++) {
    Double_t weight = event.Generate();

    TLorentzVector *pProton = event.GetDecay(0);

    TLorentzVector *pPip    = event.GetDecay(1);
    TLorentzVector *pPim    = event.GetDecay(2);

    TLorentzVector pPPip = *pProton + *pPip;
    TLorentzVector pPPim = *pProton + *pPim;

    h2->Fill(pPPip.M2() ,pPPim.M2() ,weight);
  }
  h2->Draw();
}