Problem accessing to event weigth

ROOT
1

Hi,
I am having the following problem which I didn’t manage to solve:

I have generated p p > t t~ events width madgraph (which are in the unweighted_events.root file in attach) and I am writing a Macro to analyze it.
I manage to reconstruct a variable, top PT, and to plot it but the resulting plot contains in y axis the number of events/bin instead than a cs/bin.

I read the manuals and I found that I should fill the istograms in the following way

myhistogram->Fill(PT,weight);

where weight should be in

*............................................................................* *Br 6 :Event.Weight : Double_t Weight[Event_] * *Entries : 100 : Total Size= 1869 bytes File Size = 284 * *Baskets : 1 : Basket Size= 64000 bytes Compression= 4.53 * *............................................................................* .

This part looks very similar to

*............................................................................* *Br 22 :Particle.Pz : Double_t Pz[Particle_] * *Entries : 100 : Total Size= 4270 bytes File Size = 3422 * *Baskets : 1 : Basket Size= 64000 bytes Compression= 1.08 * *............................................................................*

so I have tried to access it in the same way (see code below), but If I uncomment line 94

eventweightBranch_1->GetEntry(i_1);

I get an error " *** Break *** segmentation violation".

Does anybody know what I am doing wrong?
Thanks in advance

Daniele

[code]#include “TFile.h”
#include “TTree.h”
#include “TBranch.h”
#include “TH1F.h”

const Int_t kMaxfParticles = 500000;

// select file to analyze
const char* file1name=“unweighted_events.root”;

void Analysis_example_twofiles()
{
// List of branches (1file)
TBranch *nParticlesBranch_1;
TBranch *particlesPIDBranch_1;
TBranch *particlesStatusBranch_1;
TBranch *particlesMassBranch_1;
TBranch *particlesPXBranch_1;
TBranch *particlesPYBranch_1;
TBranch *particlesPZBranch_1;
TBranch *eventweightBranch_1;

// // // // // // // Declaration of leaf types 1 file
Int_t nParticles_1;
Int_t particlesPID_1[kMaxfParticles];
Int_t particlesStatus_1[kMaxfParticles];
Double_t particlesMass_1[kMaxfParticles];
Double_t particlesPX_1[kMaxfParticles];
Double_t particlesPY_1[kMaxfParticles];
Double_t particlesPZ_1[kMaxfParticles];
Double_t eventweight_1[kMaxfParticles];

// define canvas
TCanvas *c1 = new TCanvas(“c1”,“Histogram”,500,400);

//Defining Custom variables
Double_t PT;

// open the 1 file
TFile *f_1 = TFile::Open(file1name);
if (f_1 == 0) {
// if we cannot open the file, print an error message and return immediatly
printf(“Error: cannot open 1th file\n”);
return;
}

// get a pointer to the tree for the 1 file
TTree *tree_1 = (TTree *)f_1->Get(“LHEF”);

// To use SetBranchAddress() with simple types (e.g. double, int)
// instead of objects (e.g. std::vector).
tree_1->SetMakeClass(1);

// // // // // //
// Connect the branches with their member variables, 1 file
tree_1->SetBranchAddress(“Particle”, &nParticles_1, &nParticlesBranch_1);
tree_1->SetBranchAddress(“Particle.PID”, particlesPID_1, &particlesPIDBranch_1);
tree_1->SetBranchAddress(“Particle.Status”, particlesStatus_1, &particlesStatusBranch_1);
tree_1->SetBranchAddress(“Particle.M”, particlesMass_1, &particlesMassBranch_1);
tree_1->SetBranchAddress(“Particle.Px”, particlesPX_1, &particlesPXBranch_1);
tree_1->SetBranchAddress(“Particle.Py”, particlesPY_1, &particlesPYBranch_1);
tree_1->SetBranchAddress(“Particle.Pz”, particlesPZ_1, &particlesPZBranch_1);
tree_1->SetBranchAddress(“Event.Weight”, eventweight_1, &eventweightBranch_1);
// // // // // //
// Defining Histograms
hPT = new TH1F(“hPTtop”, “”, 50, -500, 500);
// // // // // //

// Get the number of entries
Long64_t nentries_1 = tree_1->GetEntries();

//---------------------------------------------------//
//------ ANALYSIS PART --------//
//---------------------------------------------------//
// 1 FILE

Double_t cs;

printf("#----------------------------#\n");
for (Long64_t i_1=0;i_1<nentries_1;i_1++) {
printf(“Event n. %d\n”,i_1+1);

  //event weight
   eventweightBranch_1->GetEntry(i_1);     
   
//number of particles in each event
  nParticlesBranch_1->GetEntry(i_1);
//particle PID
  particlesPIDBranch_1->GetEntry(i_1);
//status
  particlesStatusBranch_1->GetEntry(i_1);
//mass
  particlesMassBranch_1->GetEntry(i_1);
//pz
  particlesPZBranch_1->GetEntry(i_1);
  	//px
  particlesPXBranch_1->GetEntry(i_1);
  	//py
  particlesPYBranch_1->GetEntry(i_1);      

for(int iParticle_1 = 0; iParticle_1 < nParticles_1; ++iParticle_1){
  		PT=sqrt(particlesPX_1[iParticle_1]*2+particlesPY_1[iParticle_1]**2);
	if(particlesStatus_1[iParticle_1]==1){
	     		 printf("Particles number %d, PID=%d, mass=%d and status=%d and Px=%d and Py=%d and Pz=%d and PT=%d\n",iParticle_1+1,particlesPID_1[iParticle_1],particlesMass_1[iParticle_1],particlesStatus_1[iParticle_1],particlesPX_1[iParticle_1],particlesPY_1[iParticle_1],particlesPZ_1[iParticle_1],PT);
			 if(particlesPID_1[iParticle_1]==6){		
			 hPT->Fill(PT);
			 }


	}

} 
		   printf("#----------------------------#\n");

}

hPT->Draw();

c1->Update();

c1->SaveAs(“example.eps”);

}
[/code]
unweighted_events.root (34.4 KB)