Df 1 0 2_ Nano A O D Dimuon Analysis

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 and DOI: 10.7483/OPENDATA.CMS.M5AD.Y3V3). 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.

Author: Stefan Wunsch (KIT, CERN)
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, July 06, 2020 at 11:42 AM.

In [1]:
%%cpp -d
#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;

Enable multi-threading

In [2]:
ROOT::EnableImplicitMT();

Create dataframe from nanoaod files

In [3]:
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

In [4]:
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");
Plugin No such file or directory loading sec.protocol libXrdSeckrb5-4.so

Compute invariant mass of the dimuon system

In [5]:
auto df_mass = df_os.Define("Dimuon_mass", InvariantMass<float>, {"Muon_pt", "Muon_eta", "Muon_phi", "Muon_mass"});

Make histogram of dimuon mass spectrum

In [6]:
auto h = df_mass.Histo1D({"Dimuon_mass", "Dimuon_mass", 30000, 0.25, 300}, "Dimuon_mass");

Request cut-flow report

In [7]:
auto report = df_mass.Report();

Produce plot

In [8]:
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

In [9]:
report->Print();
Events with exactly two muons: pass=33370298   all=66128870   -- eff=50.46 % cumulative eff=50.46 %
Muons with opposite charge: pass=25794885   all=33370298   -- eff=77.30 % cumulative eff=39.01 %

Draw all canvases

In [10]:
%jsroot on
gROOT->GetListOfCanvases()->Draw()