df102_NanoAODDimuonAnalysis.py

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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 April 2019
## \author Stefan Wunsch (KIT, CERN)

import ROOT

# Enable multi-threading
ROOT.ROOT.EnableImplicitMT()

# Create dataframe from NanoAOD files
files = ROOT.std.vector("string")(2)
files[0] = "root://eospublic.cern.ch//eos/root-eos/cms_opendata_2012_nanoaod/Run2012B_DoubleMuParked.root"
files[1] = "root://eospublic.cern.ch//eos/root-eos/cms_opendata_2012_nanoaod/Run2012C_DoubleMuParked.root"
df = ROOT.ROOT.RDataFrame("Events", files)

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

# Compute invariant mass of the dimuon system
df_mass = df_os.Define("Dimuon_mass", "InvariantMass(Muon_pt, Muon_eta, Muon_phi, Muon_mass)")

# Make histogram of dimuon mass spectrum
h = df_mass.Histo1D(("Dimuon_mass", "Dimuon_mass", 30000, 0.25, 300), "Dimuon_mass")

# Request cut-flow report
report = df_mass.Report()

# Produce plot
ROOT.gStyle.SetOptStat(0); ROOT.gStyle.SetTextFont(42)
c = ROOT.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.Draw()

label = ROOT.TLatex(); 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()