df107_SingleTopAnalysis.py File Reference

Detailed Description

A single top analysis using the ATLAS Open Data release of 2020, with RDataFrame.

This tutorial is the analysis of single top production adapted from the ATLAS Open Data release in 2020 (http://opendata.atlas.cern/release/2020/documentation/). The data was recorded with the ATLAS detector during 2016 at a center-of-mass energy of 13 TeV. Top quarks with a mass of about 172 GeV are mostly produced in pairs but also appear alone, dominantly from the decays of a W boson in association with a light jet.

The analysis is translated to a RDataFrame workflow processing up to 60 GB of simulated events and data. By default the analysis runs on a preskimmed dataset to reduce the runtime. The full dataset can be used with the –full-dataset argument and you can also run only on a fraction of the original dataset using the argument –lumi-scale.

See the corresponding spec json file.

 
import ROOT
import sys
import json
import argparse
import os
 
# Argument parsing
parser = argparse.ArgumentParser()
parser.add_argument("--lumi-scale", type=float, default=0.05,
                    help="Run only on a fraction of the total available 10 fb^-1 (only usable together with --full-dataset)")
parser.add_argument("--full-dataset", action="store_true", default=False,
                    help="Use the full dataset (use --lumi-scale to run only on a fraction of it)")
parser.add_argument("-b", action="store_true", default=False, help="Use ROOT batch mode")
parser.add_argument("-t", action="store_true", default=False, help="Use implicit multi threading (for the full dataset only possible with --lumi-scale 1.0)")
if 'df107_SingleTopAnalysis.py' in sys.argv[0]:
    # Script
    args = parser.parse_args()
else:
    # Notebook
    args = parser.parse_args(args=[])
 
if args.b: ROOT.gROOT.SetBatch(True)
if args.t: ROOT.EnableImplicitMT()
 
if not args.full_dataset: lumi_scale = 0.05 # The preskimmed dataset contains only 0.5 fb^-1
else: lumi_scale = args.lumi_scale
lumi = 10064.0
print('Run on data corresponding to {:.1f} fb^-1 ...'.format(lumi * lumi_scale / 1000.0))
 
if args.full_dataset: dataset_path = "root://eospublic.cern.ch//eos/opendata/atlas/OutreachDatasets/2020-01-22"
else: dataset_path = "root://eospublic.cern.ch//eos/root-eos/reduced_atlas_opendata/singletop"
 
# Create a ROOT dataframe for each dataset
# Note that we load the filenames from the external json file placed in the same folder than this script.
files = json.load(open(os.path.join(ROOT.gROOT.GetTutorialsDir(), "dataframe/df107_SingleTopAnalysis.json")))
processes = files.keys()
df = {}
xsecs = {}
sumws = {}
samples = []
for p in processes:
    for d in files[p]:
        # Construct the dataframes
        folder = d[0] # Folder name
        sample = d[1] # Sample name
        xsecs[sample] = d[2] # Cross-section
        sumws[sample] = d[3] # Sum of weights
        num_events = d[4] # Number of events
        samples.append(sample)
        df[sample] = ROOT.RDataFrame("mini", "{}/1lep/{}/{}.1lep.root".format(dataset_path, folder, sample))
 
        # Scale down the datasets if requested
        if args.full_dataset and lumi_scale < 1.0:
            df[sample] = df[sample].Range(int(num_events * lumi_scale))
 
# Select events for the analysis and make histograms of the top mass
 
# Just-in-time compile custom helper function performing complex computations
ROOT.gInterpreter.Declare("""
using cRVecF = const ROOT::RVecF &;
using cRVecI = const ROOT::RVecI &;
int FindGoodLepton(cRVecI goodlep, cRVecI type, cRVecF lep_pt, cRVecF lep_eta, cRVecF lep_phi, cRVecF lep_e, cRVecF trackd0pv, cRVecF tracksigd0pv, cRVecF z0)
{
    int idx = -1; // Return -1 if no good lepton is found.
    for(auto i = 0; i < type.size(); i++) {
        if(!goodlep[i]) continue;
        if (type[i] == 11 && abs(lep_eta[i]) < 2.47 && (abs(lep_eta[i]) < 1.37 || abs(lep_eta[i]) > 1.52) && abs(trackd0pv[i] / tracksigd0pv[i]) < 5) {
            const ROOT::Math::PtEtaPhiEVector p(lep_pt[i], lep_eta[i], lep_phi[i], lep_e[i]);
            if (abs(z0[i] * sin(p.Theta())) < 0.5) {
                if (idx == -1) idx = i;
                else return -1; // Accept only events with exactly one good lepton
            }
        }
        if (type[i] == 13 && abs(lep_eta[i]) < 2.5 && abs(trackd0pv[i] / tracksigd0pv[i]) < 3) {
            const ROOT::Math::PtEtaPhiEVector p(lep_pt[i], lep_eta[i], lep_phi[i], lep_e[i]);
            if (abs(z0[i] * sin(p.Theta())) < 0.5) {
                if (idx == -1) idx = i;
                else return -1; // Accept only events with exactly one good lepton
            }
        }
    }
    return idx;
}
""")
 
for s in samples:
    # Select events with electron or muon trigger and with a missing transverse energy above 30 GeV
    df[s] = df[s].Filter("trigE || trigM")\
                 .Filter("met_et > 30000")
 
    # Perform preselection of highly isolated leptons
    df[s] = df[s].Define("goodlep", "lep_isTightID && lep_pt > 35000 && lep_ptcone30 / lep_pt < 0.1 && lep_etcone20 / lep_pt < 0.1")\
                 .Filter("ROOT::VecOps::Sum(goodlep) > 0")
 
    # Find a single good lepton, otherwise return -1 as index
    df[s] = df[s].Define("idx_lep", "FindGoodLepton(goodlep, lep_type, lep_pt, lep_eta, lep_phi, lep_E, lep_trackd0pvunbiased, lep_tracksigd0pvunbiased, lep_z0)")\
                 .Filter("idx_lep != -1")
 
    # Compute transverse mass of the W boson using the missing transverse energy and the good lepton
    # Use only events with a transverse mass of the reconstructed W boson larger than 60 GeV
    df[s] = df[s].Define("mtw", "sqrt(2 * lep_pt[idx_lep] * met_et * (1 - cos(lep_phi[idx_lep] - met_phi)))")\
                 .Filter("mtw > 60000")
 
    # Perform preselection of jets
    df[s] = df[s].Filter("ROOT::VecOps::Sum(jet_pt > 30000 && abs(jet_eta) < 2.5) > 0")
 
    # Select events with two good jets and one b-jet and find the indices in the collections
    df[s] = df[s].Define("goodjet", "jet_pt > 60000 || abs(jet_eta) > 2.4 || jet_jvt > 0.59")\
                 .Filter("ROOT::VecOps::Sum(goodjet) == 2")\
                 .Define("goodbjet", "goodjet && jet_MV2c10 > 0.8244273")\
                 .Filter("ROOT::VecOps::Sum(goodbjet) == 1")\
                 .Define("idx_tagged", "ROOT::VecOps::ArgMax(goodjet && goodbjet)")\
                 .Define("idx_untagged", "ROOT::VecOps::ArgMax(goodjet && !goodbjet)")
 
    # Select events based on the jet kinematics and the scalar sum of the transverse momentum
    # from the lepton, jets and met above 195 GeV
    df[s] = df[s].Filter("abs(jet_eta[idx_untagged]) > 1.5 && abs(jet_eta[idx_tagged] - jet_eta[idx_untagged]) > 1.5")\
                 .Filter("lep_pt[idx_lep] + jet_pt[idx_tagged] + jet_pt[idx_untagged] + met_et > 195000")
 
# Compute luminosity, scale factors and MC weights for simulated events
for s in samples:
    if "data" in s:
        df[s] = df[s].Define("weight", "1.0")
    else:
        # The single top MC weights are either 1 or -1
        if "single" in s: stop_norm = "mcWeight / abs(mcWeight)"
        else: stop_norm = "mcWeight"
        df[s] = df[s].Define("weight", "scaleFactor_ELE * scaleFactor_MUON * scaleFactor_LepTRIGGER * scaleFactor_PILEUP * scaleFactor_BTAG * {} * {} / {} * {}".format(stop_norm, xsecs[s], sumws[s], lumi))
 
# Reconstruct the top mass from the lepton, the missing transverse energy and the b-jet
 
# Just-in-time compile the function to compute the top mass from the constituents
ROOT.gInterpreter.Declare("""
float ComputeTopMass(float lep_pt, float lep_eta, float lep_phi, float lep_e, float jet_pt, float jet_eta, float jet_phi, float jet_e, float met_et, float met_phi)
{
    const ROOT::Math::PtEtaPhiEVector lep(lep_pt / 1000.0, lep_eta, lep_phi, lep_e / 1000.0);
    const ROOT::Math::PtEtaPhiEVector met(met_et / 1000.0, 0, met_phi, met_et / 1000.0);
    const ROOT::Math::PtEtaPhiEVector bjet(jet_pt / 1000.0, jet_eta, jet_phi, jet_e / 1000.0);
    // Please note that we treat here the missing transverse energy as the neutrino, even though the z component is missing!
    return (lep + met + bjet).M();
}
""")
 
histos = {}
for s in samples:
    df[s] = df[s].Define("top_mass", "ComputeTopMass(lep_pt[idx_lep], lep_eta[idx_lep], lep_phi[idx_lep], lep_E[idx_lep], jet_pt[idx_tagged], jet_eta[idx_tagged], jet_phi[idx_tagged], jet_E[idx_tagged], met_et, met_phi)")
    histos[s] = df[s].Histo1D(ROOT.RDF.TH1DModel("top_mass", "", 10, 100, 400), "top_mass", "weight")
 
# Run the event loop and merge histograms of the respective processes
 
# 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([histos[s] for s in samples])
 
def merge_histos(label):
    h = None
    for i, d in enumerate(files[label]):
        t = histos[d[1]].GetValue()
        if i == 0: h = t.Clone()
        else: h.Add(t)
    h.SetNameTitle(label, label)
    return h
 
data = merge_histos("data")
twtb = merge_histos("twtb")
singletop = merge_histos("singletop")
wjets = merge_histos("wjets")
 
# Create the plot
 
# Set styles
ROOT.gROOT.SetStyle("ATLAS")
 
# Create canvas with pad
c = ROOT.TCanvas("c", "", 600, 600)
pad = ROOT.TPad("upper_pad", "", 0, 0, 1, 1)
pad.SetTickx(False)
pad.SetTicky(False)
pad.Draw()
pad.cd()
 
# Draw stack with MC contributions
stack = ROOT.THStack()
wjets.Scale(1.1) # Corrected normalization derived from a validation region
for h, color in zip(
        [wjets, twtb, singletop],
        [(222, 90, 106), (155, 152, 204), (208, 240, 193)]):
    h.SetLineWidth(1)
    h.SetLineColor(1)
    h.SetFillColor(ROOT.TColor.GetColor(*color))
    stack.Add(h)
stack.Draw("HIST")
stack.GetXaxis().SetTitle("m_{W(l#nu)+b} [GeV]")
stack.GetYaxis().SetTitle("Events")
stack.GetYaxis().SetLabelSize(0.04)
stack.GetYaxis().SetTitleSize(0.045)
stack.GetXaxis().SetLabelSize(0.04)
stack.GetXaxis().SetTitleSize(0.045)
stack.SetMinimum(0)
stack.SetMaximum(5000 * lumi_scale)
stack.GetYaxis().ChangeLabel(1, -1, 0)
 
# Draw data
data.SetMarkerStyle(20)
data.SetMarkerSize(1.2)
data.SetLineWidth(2)
data.SetLineColor(ROOT.kBlack)
data.Draw("E SAME")
 
# Add legend
legend = ROOT.TLegend(0.60, 0.65, 0.92, 0.92)
legend.SetTextFont(42)
legend.SetFillStyle(0)
legend.SetBorderSize(0)
legend.SetTextSize(0.035)
legend.SetTextAlign(32)
legend.AddEntry(data, "Data" ,"lep")
legend.AddEntry(singletop, "Single top + jet", "f")
legend.AddEntry(twtb, "t#bar{t},Wt,t#bar{b}", "f")
legend.AddEntry(wjets, "W+jets", "f")
legend.Draw("SAME")
 
# Add ATLAS label
text = ROOT.TLatex()
text.SetNDC()
text.SetTextFont(72)
text.SetTextSize(0.045)
text.DrawLatex(0.21, 0.86, "ATLAS")
text.SetTextFont(42)
text.DrawLatex(0.21 + 0.16, 0.86, "Open Data")
text.SetTextSize(0.04)
text.DrawLatex(0.21, 0.80, "#sqrt{{s}} = 13 TeV, {:.1f} fb^{{-1}}".format(lumi * lumi_scale / 1000.0))
 
# Save the plot
c.SaveAs("df107_SingleTopAnalysis.png")
print("Saved figure to df107_SingleTopAnalysis.png")

Run on data corresponding to 0.5 fb^-1 ...
Saved figure to df107_SingleTopAnalysis.png

Date

July 2020

Author

Stefan Wunsch (KIT, CERN)

Definition in file df107_SingleTopAnalysis.py.