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pythia8.C
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1/// \file
2/// \ingroup tutorial_pythia
3/// pythia8 basic example
4///
5/// to run, do:
6///
7/// ~~~{.cpp}
8/// root > .x pythia8.C
9/// ~~~
10///
11/// \macro_code
12///
13/// \author Andreas Morsch
14
15#include "TSystem.h"
16#include "TH1F.h"
17#include "TClonesArray.h"
18#include "TPythia8.h"
19#include "TParticle.h"
20#include "TDatabasePDG.h"
21#include "TCanvas.h"
22
23void pythia8(Int_t nev = 100, Int_t ndeb = 1)
24{
25// Load libraries
26 gSystem->Load("libEG");
27 gSystem->Load("libEGPythia8");
28// Histograms
29 TH1F* etaH = new TH1F("etaH", "Pseudorapidity", 120, -12., 12.);
30 TH1F* ptH = new TH1F("ptH", "pt", 50, 0., 10.);
31
32
33// Array of particles
34 TClonesArray* particles = new TClonesArray("TParticle", 1000);
35// Create pythia8 object
36 TPythia8* pythia8 = new TPythia8();
37
38#if PYTHIA_VERSION_INTEGER == 8235
39 // Pythia 8.235 is known to cause crashes:
40 printf("ABORTING PYTHIA8 TUTORIAL!\n");
41 printf("The version of Pythia you use is known to case crashes due to memory errors.\n");
42 printf("They have been reported to the authors; the Pythia versions 8.1... are known to work.\n");
43 return;
44#endif
45
46// Configure
47 pythia8->ReadString("HardQCD:all = on");
48 pythia8->ReadString("Random:setSeed = on");
49 // use a reproducible seed: always the same results for the tutorial.
50 pythia8->ReadString("Random:seed = 42");
51
52
53// Initialize
54
55 pythia8->Initialize(2212 /* p */, 2212 /* p */, 14000. /* TeV */);
56
57// Event loop
58 for (Int_t iev = 0; iev < nev; iev++) {
59 pythia8->GenerateEvent();
60 if (iev < ndeb) pythia8->EventListing();
61 pythia8->ImportParticles(particles,"All");
62 Int_t np = particles->GetEntriesFast();
63// Particle loop
64 for (Int_t ip = 0; ip < np; ip++) {
65 TParticle* part = (TParticle*) particles->At(ip);
66 Int_t ist = part->GetStatusCode();
67 // Positive codes are final particles.
68 if (ist <= 0) continue;
69 Int_t pdg = part->GetPdgCode();
71 if (charge == 0.) continue;
72 Float_t eta = part->Eta();
73 Float_t pt = part->Pt();
74
75 etaH->Fill(eta);
76 if (pt > 0.) ptH->Fill(pt, 1./(2. * pt));
77 }
78 }
79
80 pythia8->PrintStatistics();
81
82 TCanvas* c1 = new TCanvas("c1","Pythia8 test example",800,800);
83 c1->Divide(1, 2);
84 c1->cd(1);
85 etaH->Scale(5./Float_t(nev));
86 etaH->Draw();
87 etaH->SetXTitle("#eta");
88 etaH->SetYTitle("dN/d#eta");
89
90 c1->cd(2);
91 gPad->SetLogy();
92 ptH->Scale(5./Float_t(nev));
93 ptH->Draw();
94 ptH->SetXTitle("p_{t} [GeV/c]");
95 ptH->SetYTitle("dN/dp_{t}^{2} [GeV/c]^{-2}");
96 }
int Int_t
Definition: CPyCppyy.h:43
float Float_t
Definition: RtypesCore.h:57
R__EXTERN TSystem * gSystem
Definition: TSystem.h:559
#define gPad
Definition: TVirtualPad.h:287
The Canvas class.
Definition: TCanvas.h:23
An array of clone (identical) objects.
Definition: TClonesArray.h:29
static TDatabasePDG * Instance()
static function
TParticlePDG * GetParticle(Int_t pdgCode) const
Get a pointer to the particle object according to the MC code number.
1-D histogram with a float per channel (see TH1 documentation)}
Definition: TH1.h:575
virtual void SetXTitle(const char *title)
Definition: TH1.h:413
virtual Int_t Fill(Double_t x)
Increment bin with abscissa X by 1.
Definition: TH1.cxx:3350
virtual void Draw(Option_t *option="")
Draw this histogram with options.
Definition: TH1.cxx:3073
virtual void SetYTitle(const char *title)
Definition: TH1.h:414
virtual void Scale(Double_t c1=1, Option_t *option="")
Multiply this histogram by a constant c1.
Definition: TH1.cxx:6565
Int_t GetEntriesFast() const
Definition: TObjArray.h:64
TObject * At(Int_t idx) const
Definition: TObjArray.h:166
Double_t Charge() const
Definition: TParticlePDG.h:68
Description of the dynamic properties of a particle.
Definition: TParticle.h:26
Int_t GetStatusCode() const
Definition: TParticle.h:82
Int_t GetPdgCode() const
Definition: TParticle.h:83
Double_t Pt() const
Definition: TParticle.h:135
Double_t Eta() const
Definition: TParticle.h:137
TPythia8 is an interface class to C++ version of Pythia 8.1 event generators, written by T....
Definition: TPythia8.h:77
void ReadString(const char *string) const
Configuration.
Definition: TPythia8.cxx:300
Bool_t Initialize(Int_t idAin, Int_t idBin, Double_t ecms)
Initialization.
Definition: TPythia8.cxx:147
void EventListing() const
Event listing.
Definition: TPythia8.cxx:364
void PrintStatistics() const
Print end of run statistics.
Definition: TPythia8.cxx:356
virtual void GenerateEvent()
Generate the next event.
Definition: TPythia8.cxx:185
virtual Int_t ImportParticles(TClonesArray *particles, Option_t *option="")
Import particles from Pythia stack.
Definition: TPythia8.cxx:194
virtual int Load(const char *module, const char *entry="", Bool_t system=kFALSE)
Load a shared library.
Definition: TSystem.cxx:1855
TPaveText * pt
return c1
Definition: legend1.C:41