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Reference Guide
PhaseSpace.C
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1 /// \file
2 /// \ingroup tutorial_physics
3 /// \notebook -js
4 /// Example of use of TGenPhaseSpace
5 ///
6 /// \macro_image
7 /// \macro_code
8 ///
9 /// \author Valerio Filippini
10 
11 void PhaseSpace() {
12 
13  TLorentzVector target(0.0, 0.0, 0.0, 0.938);
14  TLorentzVector beam(0.0, 0.0, .65, .65);
15  TLorentzVector W = beam + target;
16 
17  //(Momentum, Energy units are Gev/C, GeV)
18  Double_t masses[3] = { 0.938, 0.139, 0.139} ;
19 
20  TGenPhaseSpace event;
21  event.SetDecay(W, 3, masses);
22 
23  TH2F *h2 = new TH2F("h2","h2", 50,1.1,1.8, 50,1.1,1.8);
24 
25  for (Int_t n=0;n<100000;n++) {
26  Double_t weight = event.Generate();
27 
28  TLorentzVector *pProton = event.GetDecay(0);
29 
30  TLorentzVector *pPip = event.GetDecay(1);
31  TLorentzVector *pPim = event.GetDecay(2);
32 
33  TLorentzVector pPPip = *pProton + *pPip;
34  TLorentzVector pPPim = *pProton + *pPim;
35 
36  h2->Fill(pPPip.M2() ,pPPim.M2() ,weight);
37  }
38  h2->Draw();
39 }
Double_t M2() const
int Int_t
Definition: RtypesCore.h:41
DisclaimerTLorentzVector is a legacy class.
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition: TH1.cxx:2981
2-D histogram with a float per channel (see TH1 documentation)}
Definition: TH2.h:248
Utility class to generate n-body event, with constant cross-section (default) or with Fermi energy de...
double Double_t
Definition: RtypesCore.h:55
Bool_t SetDecay(TLorentzVector &P, Int_t nt, const Double_t *mass, Option_t *opt="")
Input:
Int_t Fill(Double_t)
Invalid Fill method.
Definition: TH2.cxx:292
const Int_t n
Definition: legend1.C:16