learning/tof_resolution/htree.cpp

#define htree_cxx
#include "htree.h"
#include <TH2.h>
#include <TStyle.h>
#include <TCanvas.h>
#include <math.h>
#include <cstdio>

void htree::Loop()
{
//   In a ROOT session, you can do:
//      Root > .L htree.C
//      Root > htree t
//      Root > t.GetEntry(12); // Fill t data members with entry number 12
//      Root > t.Show();       // Show values of entry 12
//      Root > t.Show(16);     // Read and show values of entry 16
//      Root > t.Loop();       // Loop on all entries
//

//     This is the loop skeleton where:
//    jentry is the global entry number in the chain
//    ientry is the entry number in the current Tree
//  Note that the argument to GetEntry must be:
//    jentry for TChain::GetEntry
//    ientry for TTree::GetEntry and TBranch::GetEntry
//
//       To read only selected branches, Insert statements like:
// METHOD1:
//    fChain->SetBranchStatus("*",0);  // disable all branches
//    fChain->SetBranchStatus("branchname",1);  // activate branchname
// METHOD2: replace line
//    fChain->GetEntry(jentry);       //read all branches
//by  b_branchname->GetEntry(ientry); //read only this branch
    if (fChain == 0) return;

    TH1F *dtof[2];   // east, west
    dtof[0] = new TH1F("tof_east", "TOF resolution uncorrected EAST;#Delta t, ns;dN/dt", 300,-3,3);
    dtof[1] = new TH1F("tof_west", "TOF resolution uncorrected WEST;#Delta t, ns;dN/dt", 300,-3,3);

    TH2F *dtof_slat[2];   // east, west per slat
    dtof_slat[0] = new TH2F("tofslat_east", "TOF resolution uncorrected EAST;slat number;#Delta t, ns;dN/dt", 1000,0,999, 300,-3,3);
    dtof_slat[1] = new TH2F("tofslat_west", "TOF resolution uncorrected WEST;slat number;#Delta t, ns;dN/dt", 1000,0,999, 300,-3,3);

    float t_exp, beta, pt, dt;    // expected time

    Long64_t nentries = fChain->GetEntriesFast();

    // activate only required branches
    fChain->SetBranchStatus("*",0);
    fChain->SetBranchStatus("nh",1);
    fChain->SetBranchStatus("tofdz",1);
    fChain->SetBranchStatus("tofdphi",1);
    fChain->SetBranchStatus("p",1);
    fChain->SetBranchStatus("pltof",1);
    fChain->SetBranchStatus("dcarm",1);
    fChain->SetBranchStatus("ttof",1);
    fChain->SetBranchStatus("slat",1);
    fChain->SetBranchStatus("the0",1);

    for (Long64_t jentry=0; jentry<nentries;jentry++)
    {
        // skip entry if read failed
        if (fChain->GetEntry(jentry) == -1)
            break;
        
        // loop through all tracks
        for (int i=0; i<nh; i++)
        {
            if (fabs(tofdz[i])>1.0 || fabs(tofdphi[i])>1.0 ||
                dcarm[i]<0 || dcarm[i]>1)
                continue;

            pt = p[i] * sin(the0[i]);
            if (pt < 1.1 || pt > 1.9)
                continue;

            beta = p[i] / sqrt(0.0194795 + p[i]*p[i]);
            t_exp = pltof[i] / (29.9792458 * beta);
            
            dt = ttof[i] - t_exp;
            dtof[dcarm[i]] -> Fill(dt);
            dtof_slat[dcarm[i]] -> Fill(slat[i], dt);
        }
    }

    output->Write();
    puts("Processing finished.");
}