df102_NanoAODDimuonAnalysis.C

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/// \file
/// \ingroup tutorial_dataframe
/// \notebook -js
/// This tutorial illustrates how NanoAOD files can be processed with ROOT
/// dataframes. The NanoAOD-like input files are filled with 66 mio. events
/// from CMS OpenData containing muon candidates part of 2012 dataset
/// ([DOI: 10.7483/OPENDATA.CMS.YLIC.86ZZ](http://opendata.cern.ch/record/6004)
/// and [DOI: 10.7483/OPENDATA.CMS.M5AD.Y3V3](http://opendata.cern.ch/record/6030)).
/// The macro matches muon pairs and produces an histogram of the dimuon mass
/// spectrum showing resonances up to the Z mass.
/// Note that the bump at 30 GeV is not a resonance but a trigger effect.
///
/// Some more details about the dataset:
///   - It contains about 66 millions events (muon and electron collections, plus some other information, e.g. about primary vertices)
///   - It spans two compressed ROOT files located on EOS for about a total size of 7.5 GB.
///
/// \macro_image
/// \macro_code
/// \macro_output
///
/// \date August 2018
/// \author Stefan Wunsch (KIT, CERN)

#include "ROOT/RDataFrame.hxx"
#include "ROOT/RVec.hxx"
#include "TCanvas.h"
#include "TH1D.h"
#include "TLatex.h"
#include "Math/Vector4D.h"
#include "TStyle.h"

using namespace ROOT::VecOps;

void df102_NanoAODDimuonAnalysis()
{
   // Enable multi-threading
   ROOT::EnableImplicitMT();

   // Create dataframe from NanoAOD files
   ROOT::RDataFrame df("Events",
                      {"root://eospublic.cern.ch//eos/root-eos/cms_opendata_2012_nanoaod/Run2012B_DoubleMuParked.root",
                       "root://eospublic.cern.ch//eos/root-eos/cms_opendata_2012_nanoaod/Run2012C_DoubleMuParked.root"});

   // For simplicity, select only events with exactly two muons and require opposite charge
   auto df_2mu = df.Filter("nMuon == 2", "Events with exactly two muons");
   auto df_os = df_2mu.Filter("Muon_charge[0] != Muon_charge[1]", "Muons with opposite charge");

   // Compute invariant mass of the dimuon system
   auto df_mass = df_os.Define("Dimuon_mass", InvariantMass<float>, {"Muon_pt", "Muon_eta", "Muon_phi", "Muon_mass"});

   // Make histogram of dimuon mass spectrum
   auto h = df_mass.Histo1D({"Dimuon_mass", "Dimuon_mass", 30000, 0.25, 300}, "Dimuon_mass");

   // Request cut-flow report
   auto report = df_mass.Report();

   // Produce plot
   gStyle->SetOptStat(0); gStyle->SetTextFont(42);
   auto c = new TCanvas("c", "", 800, 700);
   c->SetLogx(); c->SetLogy();

   h->SetTitle("");
   h->GetXaxis()->SetTitle("m_{#mu#mu} (GeV)"); h->GetXaxis()->SetTitleSize(0.04);
   h->GetYaxis()->SetTitle("N_{Events}"); h->GetYaxis()->SetTitleSize(0.04);
   h->DrawClone();

   TLatex label; label.SetNDC(true);
   label.DrawLatex(0.175, 0.740, "#eta");
   label.DrawLatex(0.205, 0.775, "#rho,#omega");
   label.DrawLatex(0.270, 0.740, "#phi");
   label.DrawLatex(0.400, 0.800, "J/#psi");
   label.DrawLatex(0.415, 0.670, "#psi'");
   label.DrawLatex(0.485, 0.700, "Y(1,2,3S)");
   label.DrawLatex(0.755, 0.680, "Z");
   label.SetTextSize(0.040); label.DrawLatex(0.100, 0.920, "#bf{CMS Open Data}");
   label.SetTextSize(0.030); label.DrawLatex(0.630, 0.920, "#sqrt{s} = 8 TeV, L_{int} = 11.6 fb^{-1}");

   c->SaveAs("dimuon_spectrum.pdf");

   // Print cut-flow report
   report->Print();
}

int main()
{
   df102_NanoAODDimuonAnalysis();
}