Double_t distance=1000; //Flight path (cm)

Double_t * GetPositions(Int_t index){
Double_t vec[2];
vec[0]=-Pixel::GetDetSizeX()/2+(index%100+0.5)*Pixel::GetPixelSizeX();
vec[1]= Pixel::GetDetSizeX()/2-(index/100+0.5)*Pixel::GetPixelSizeX();
return vec;
}

//main macro
void makePixelTree( Float_t beam_momentum) {

gROOT->LoadMacro("Pixel.cxx++g");
gROOT->LoadMacro("PixelTimeInfo.cxx++g");


// Create some histograms.
  TH2F *hXvsY  = new TH2F("hXvsY","X-Y distribution of Pixels",100,5,-5, 100,-5,5);
  TH1F *hTime  = new TH1F("hTime","Time distribution of Pixels",1000,30,50);
//opzioni grafiche istogrammi
  hXvsY->SetMarkerStyle(21);
  hXvsY->SetMarkerSize(0.3);
  hXvsY->SetMarkerColor(2);
  hXvsY->GetYaxis()->SetTitle("Position Y (cm)");
  hXvsY->GetXaxis()->SetTitle("Position X (cm)");
  hTime->GetXaxis()->SetTitle("Time (ns)");
//open a root file
  
  TTree *T = new TTree("T","Pixel tree"); //create a tree
  Double_t mass, time,x,y;
  Int_t index;
  T->Branch("mass",&mass,"mass/D");
  T->Branch("time",&time,"time/D");
  T->Branch("x",&x,"x/D");
  T->Branch("y",&y,"y/D");
  T->Branch("index",&index,"index/I");

PixelTimeInfo::OpenCalibFile();

// Create Pixels from tracks hitting randomly on the detector randomly
gBenchmark->Reset();
gBenchmark->Start("makeHistos");

 gRandom->SetSeed(); // setting the initial seed 
 Int_t iParticle=0; 
 Double_t particle_Mass[]={0.149,0.498,0.938};  
 PixelTimeInfo myPixel; 
  for ( Int_t i=0; i<100000; i++) {
    iParticle= gRandom->Rndm()*3; //random extraction of species  
    index = gRandom->Rndm()*10000; //random extraction of pixel position
    Double_t *vec=GetPositions(index);
    x=vec[0], y=vec[1];
    mass=particle_Mass[iParticle];
    Float_t path=TMath::Sqrt(x*x +y*y+distance*distance);
    time=path*TMath::Sqrt(beam_momentum*beam_momentum+particle_Mass[iParticle]*particle_Mass[iParticle])/(beam_momentum*2.99E1); // this is the flight time, t=path/(beta*c), in ns
    time=gRandom->Gaus(time,0.1);
    myPixel=PixelTimeInfo(index,time);      
    hXvsY->Fill(myPixel.GetPosX(),myPixel.GetPosY()); 
    hTime->Fill(myPixel.GetTime());     
    T->Fill();
  }

  //stop benchmarking execution time
  gBenchmark->Stop("makeHistos");
  gBenchmark->Show("makeHistos");
  PixelTimeInfo::CloseCalibFile();
// draw the histogram
   TCanvas *cHist=new TCanvas("cHist","test histograms",50,50,700,300);
   cHist->Divide(2,1);
   cHist->cd(1);
   hXvsY->Draw();
   cHist->cd(2);
   hTime->Draw();
   TFile *file = new TFile("pixelTree.root","recreate"); //apro il file root
   hXvsY->Write();
   hTime->Write();
   T->Write(); //scrive il tree su file
   file->Close();//chiudo il file
}