df104.py File Reference

The Higgs to two photons analysis from the ATLAS Open Data 2020 release, with RDataFrame.

This tutorial is the Higgs to two photons analysis from the ATLAS Open Data release in 2020 (http://opendata.atlas.cern/release/2020/documentation/). The data was taken with the ATLAS detector during 2016 at a center-of-mass energy of 13 TeV. Although the Higgs to two photons decay is very rare, the contribution of the Higgs can be seen as a narrow peak around 125 GeV because of the excellent reconstruction and identification efficiency of photons at the ATLAS experiment.

The analysis is translated to a RDataFrame workflow processing 1.7 GB of simulated events and data.

This macro is replica of tutorials/analysis/dataframe/df104_HiggsToTwoPhotons.py, but with usage of ROOT7 graphics Run macro with python3 -i df104.py command to get interactive canvas

 
import ROOT
import os
from ROOT.Experimental import (
    RCanvas,
    RText,
    RAttrText,
    RAttrFont,
    RAttrFill,
    RAttrLine,
    RLegend,
    RPadPos,
    RPadExtent,
    TObjectDrawable,
)
 
# Enable multi-threading
ROOT.ROOT.EnableImplicitMT()
 
# Create a ROOT dataframe for each dataset
path = "root://eospublic.cern.ch//eos/opendata/atlas/OutreachDatasets/2020-01-22"
df = {}
df["data"] = ROOT.RDataFrame(
    "mini", (os.path.join(path, "GamGam/Data/data_{}.GamGam.root".format(x)) for x in ("A", "B", "C", "D"))
)
df["ggH"] = ROOT.RDataFrame("mini", os.path.join(path, "GamGam/MC/mc_343981.ggH125_gamgam.GamGam.root"))
df["VBF"] = ROOT.RDataFrame("mini", os.path.join(path, "GamGam/MC/mc_345041.VBFH125_gamgam.GamGam.root"))
processes = list(df.keys())
 
# Apply scale factors and MC weight for simulated events and a weight of 1 for the data
for p in ["ggH", "VBF"]:
    df[p] = df[p].Define("weight", "scaleFactor_PHOTON * scaleFactor_PhotonTRIGGER * scaleFactor_PILEUP * mcWeight")
df["data"] = df["data"].Define("weight", "1.0")
 
# Select the events for the analysis
for p in processes:
    # Apply preselection cut on photon trigger
    df[p] = df[p].Filter("trigP")
 
    # Find two good muons with tight ID, pt > 25 GeV and not in the transition region between barrel and encap
    df[p] = (
        df[p]
        .Define(
            "goodphotons",
            "photon_isTightID && (photon_pt > 25000) && (abs(photon_eta) < 2.37) && ((abs(photon_eta) < 1.37) || (abs(photon_eta) > 1.52))",
        )
        .Filter("Sum(goodphotons) == 2")
    )
 
    # Take only isolated photons
    df[p] = (
        df[p]
        .Filter("Sum(photon_ptcone30[goodphotons] / photon_pt[goodphotons] < 0.065) == 2")
        .Filter("Sum(photon_etcone20[goodphotons] / photon_pt[goodphotons] < 0.065) == 2")
    )
 
# Compile a function to compute the invariant mass of the diphoton system
ROOT.gInterpreter.Declare(
    """
using Vec_t = const ROOT::VecOps::RVec<float>;
float ComputeInvariantMass(Vec_t& pt, Vec_t& eta, Vec_t& phi, Vec_t& e) {
    ROOT::Math::PtEtaPhiEVector p1(pt[0], eta[0], phi[0], e[0]);
    ROOT::Math::PtEtaPhiEVector p2(pt[1], eta[1], phi[1], e[1]);
    return (p1 + p2).mass() / 1000.0;
}
"""
)
 
# Define a new column with the invariant mass and perform final event selection
hists = {}
for p in processes:
    # Make four vectors and compute invariant mass
    df[p] = df[p].Define(
        "m_yy",
        "ComputeInvariantMass(photon_pt[goodphotons], photon_eta[goodphotons], photon_phi[goodphotons], photon_E[goodphotons])",
    )
 
    # Make additional kinematic cuts and select mass window
    df[p] = (
        df[p]
        .Filter("photon_pt[goodphotons][0] / 1000.0 / m_yy > 0.35")
        .Filter("photon_pt[goodphotons][1] / 1000.0 / m_yy > 0.25")
        .Filter("m_yy > 105 && m_yy < 160")
    )
 
    # Book histogram of the invariant mass with this selection
    hists[p] = df[p].Histo1D(
        ROOT.RDF.TH1DModel(p, "Diphoton invariant mass; m_{#gamma#gamma} [GeV];Events", 30, 105, 160), "m_yy", "weight"
    )
 
# Run the event loop
 
# RunGraphs allows to run the event loops of the separate RDataFrame graphs
# concurrently. This results in an improved usage of the available resources
# if each separate RDataFrame can not utilize all available resources, e.g.,
# because not enough data is available.
ROOT.RDF.RunGraphs([hists[s] for s in ["ggH", "VBF", "data"]])
 
ggh = hists["ggH"].GetValue()
vbf = hists["VBF"].GetValue()
data = hists["data"].GetValue()
 
# Create the plot
 
# Set styles - not yet available for v7
# ROOT.gROOT.SetStyle("ATLAS")
 
# Create canvas with pads for main plot and data/MC ratio
c = RCanvas.Create("df104_HiggsToTwoPhotons")
 
lower_pad = c.AddPad(RPadPos(0, 0.65), RPadExtent(1, 0.35))
upper_pad = c.AddPad(RPadPos(0, 0), RPadExtent(1, 0.65))
 
upper_frame = upper_pad.AddFrame()
upper_frame.margins.bottom = 0
upper_frame.margins.left = 0.14
upper_frame.margins.right = 0.05
upper_frame.x.labels.hide = True
 
lower_frame = lower_pad.AddFrame()
lower_frame.margins.top = 0
lower_frame.margins.left = 0.14
lower_frame.margins.right = 0.05
lower_frame.margins.bottom = 0.3
 
# Fit signal + background model to data
fit = ROOT.TF1("fit", "([0]+[1]*x+[2]*x^2+[3]*x^3)+[4]*exp(-0.5*((x-[5])/[6])^2)", 105, 160)
fit.FixParameter(5, 125.0)
fit.FixParameter(4, 119.1)
fit.FixParameter(6, 2.39)
fit.SetLineColor(2)
fit.SetLineStyle(ROOT.kSolid)
fit.SetLineWidth(2)
# do not draw fit function
data.Fit("fit", "0", "", 105, 160)
 
# Draw data
data.SetMarkerStyle(20)
data.SetMarkerSize(1.2)
data.SetLineWidth(2)
data.SetLineColor("black")
data.SetMinimum(1e-3)
data.SetMaximum(8e3)
data.GetYaxis().SetLabelSize(0.045)
data.GetYaxis().SetTitleSize(0.05)
data.GetYaxis().SetTitleOffset(1.4)
data.SetStats(False)
data.SetTitle("")
 
data_drawable = upper_pad.Add[TObjectDrawable]()
data_drawable.Set(data, "E")
 
# Draw fit
fit_drawable = upper_pad.Add[TObjectDrawable]()
fit_drawable.Set(fit, "SAME")
 
# Draw background
bkg = ROOT.TF1("bkg", "([0]+[1]*x+[2]*x^2+[3]*x^3)", 105, 160)
for i in range(4):
    bkg.SetParameter(i, fit.GetParameter(i))
bkg.SetLineColor(4)
bkg.SetLineStyle(ROOT.kDashed)
bkg.SetLineWidth(2)
bkg_drawable = upper_pad.Add[TObjectDrawable]()
bkg_drawable.Set(bkg, "SAME")
 
# Scale simulated events with luminosity * cross-section / sum of weights
# and merge to single Higgs signal
lumi = 10064.0
ggh.Scale(lumi * 0.102 / 55922617.6297)
vbf.Scale(lumi * 0.008518764 / 3441426.13711)
higgs = ggh.Clone()
higgs.Add(vbf)
higgs_drawable = upper_pad.Add[TObjectDrawable]()
higgs_drawable.Set(higgs, "HIST SAME")
 
# Draw ratio
 
ratiobkg = ROOT.TH1I("zero", "", 10, 105, 160)
ratiobkg.SetLineColor(4)
ratiobkg.SetLineStyle(ROOT.kDashed)
ratiobkg.SetLineWidth(2)
ratiobkg.SetMinimum(-125)
ratiobkg.SetMaximum(250)
ratiobkg.SetStats(False)
ratiobkg.GetXaxis().SetLabelSize(0.08)
ratiobkg.GetXaxis().SetTitleSize(0.12)
ratiobkg.GetXaxis().SetTitleOffset(1.0)
ratiobkg.GetYaxis().SetLabelSize(0.08)
ratiobkg.GetYaxis().SetTitleSize(0.09)
ratiobkg.GetYaxis().SetTitle("Data - Bkg.")
ratiobkg.GetYaxis().SetTitleOffset(0.7)
ratiobkg.GetYaxis().CenterTitle()
ratiobkg.GetYaxis().SetNdivisions(503, False)
ratiobkg.GetYaxis().ChangeLabel(-1, -1, 0)
ratiobkg.GetXaxis().SetTitle("m_{#gamma#gamma} [GeV]")
lower_pad.Add[TObjectDrawable]().Set(ratiobkg, "AXIS")
 
ratiosig = ROOT.TH1F("ratiosig", "ratiosig", 5500, 105, 160)
ratiosig.Eval(fit)
ratiosig.SetLineColor(2)
ratiosig.SetLineStyle(ROOT.kSolid)
ratiosig.SetLineWidth(2)
ratiosig.Add(bkg, -1)
lower_pad.Add[TObjectDrawable]().Set(ratiosig, "SAME")
 
ratiodata = data.Clone()
ratiodata.Add(bkg, -1)
for i in range(1, data.GetNbinsX()):
    ratiodata.SetBinError(i, data.GetBinError(i))
 
lower_pad.Add[TObjectDrawable]().Set(ratiodata, "E SAME")
 
# Add RLegend
legend = upper_pad.Draw[RLegend](RPadPos(0.01, 0.01), RPadExtent(0.3, 0.4))
legend.text.size = 0.05
legend.text.align = RAttrText.kRightCenter
legend.text.font = RAttrFont.kArial
legend.border.style = RAttrLine.kNone
legend.border.width = 0
legend.fill.style = RAttrFill.kHollow
 
legend.AddEntry(data_drawable, "Data", "lme")
legend.AddEntry(bkg_drawable, "Background", "l")
legend.AddEntry(fit_drawable, "Signal + Bkg.", "l")
legend.AddEntry(higgs_drawable, "Signal", "l")
 
# Add ATLAS labels
lbl1 = upper_pad.Draw[RText](RPadPos(0.05, 0.88), "ATLAS")
lbl1.onFrame = True
lbl1.text.font = RAttrFont.kArialBoldOblique
lbl1.text.size = 0.04
lbl1.text.align = RAttrText.kLeftBottom
lbl2 = upper_pad.Draw[RText](RPadPos(0.05 + 0.16, 0.88), "Open Data")
lbl2.onFrame = True
lbl2.text.font = RAttrFont.kArial
lbl2.text.size = 0.04
lbl2.text.align = RAttrText.kLeftBottom
lbl3 = upper_pad.Draw[RText](RPadPos(0.05, 0.82), "#sqrt{s} = 13 TeV, 10 fb^{-1}")
lbl3.onFrame = True
lbl3.text.font = RAttrFont.kArial
lbl3.text.size = 0.03
lbl3.text.align = RAttrText.kLeftBottom
 
# show canvas finally
c.SetSize(700, 780)
c.Show()
 
# Save plot in PNG file
if c.SaveAs("df104.png"):
    print("Saved figure to df104.png")

Date

2021-06-15

Authors

Stefan Wunsch (KIT, CERN) Sergey Linev (GSI)

Definition in file df104.py.