rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

ATLAS_2018_I1707015

Measurement of normalized differential distributions in ttbar+photon production at 13 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1707015
Status: VALIDATED
Authors:
  • Yichen Li
  • Andy Buckley
  • Leah Spiedel Johnson
  • Neil Warrack
References: Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • top-quark pair production associated with a photon

Differential cross-sections for the production of a top-quark pair in association with a photon are measured with proton-proton collision data corresponding to an integrated luminosity of 36.1 fb^-1, collected by the ATLAS detector at the LHC in 2015 and 2016 at a centre-of-mass energy of 13 TeV. The measurements are performed in single-lepton and dilepton final states in a fiducial volume. Events with exactly one photon, one or two leptons, a channel-dependent minimum number of jets, and at least one b-jet are selected. Neural network algorithms are used to separate the signal from the backgrounds. The differential cross-sections are measured as a function of photon transverse momentum, photon absolute pseudorapidity, and angular distance between the photon and its closest lepton in both channels, as well asazimuthal opening angle and absolute pseudorapidity difference between the two leptons in the dilepton channel.

Source code: ATLAS_2018_I1707015.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/DressedLeptons.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

  /// @brief: ttbar + gamma at 13 TeV
  class ATLAS_2018_I1707015 : public Analysis {
  public:


    // Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(ATLAS_2018_I1707015);


    // Book histograms and initialise projections before the run
    void init() {


      // Set default running mode to 3 (all)
      _mode = 3;

      // Get running mode
      if ( getOption("LMODE") == "SINGLE" )   _mode = 1;
      if ( getOption("LMODE") == "DILEPTON" ) _mode = 2;
      if ( getOption("LMODE") == "ALL" )      _mode = 3;

      // All final state particles
      const FinalState fs;

      // Charged particles for signal photon isolation
      ChargedFinalState cfs(fs);
      declare(cfs, "CFS");

      // Signal photons
      PromptFinalState photons(Cuts::abspid == PID::PHOTON && Cuts::pT > 20*GeV && Cuts::abseta < 2.37, true);
      declare(photons, "Photons");

      // Leptons
      PromptFinalState leptons(Cuts::abspid == PID::MUON || Cuts::abspid == PID::ELECTRON, true);

      // Dress the leptons
      FinalState dressPhotons(Cuts::abspid == PID::PHOTON);
      Cut lepCuts = (Cuts::abseta < 2.5) && (Cuts::pT > 25*GeV);
      DressedLeptons dressedLeptons(dressPhotons, leptons, 0.1, lepCuts);
      declare(dressedLeptons, "Leptons");

      // Jet alg input
      VetoedFinalState vfs(fs);

      // Remove prompt invisibles from jet input
      VetoedFinalState invis_fs(fs);
      invis_fs.addVetoOnThisFinalState(VisibleFinalState(fs));
      PromptFinalState invis_pfs = PromptFinalState(invis_fs, true);
      vfs.addVetoOnThisFinalState(invis_pfs);

      // Remove prompt dressed muons (muons + associated photons) from jet input
      PromptFinalState muons(Cuts::abspid == PID::MUON, true);
      DressedLeptons dressedmuons(dressPhotons, muons, 0.1);
      vfs.addVetoOnThisFinalState(dressedmuons);

      // Jet clustering
      FastJets jets(vfs, FastJets::ANTIKT, 0.4, JetAlg::Muons::ALL, JetAlg::Invisibles::ALL);
      declare(jets, "Jets");

      // Book histograms
      if ( _mode == 1 or _mode == 3 ){  // Single lepton channel
        book(_h["sl_ph_pt"],   3,1,1);  // photon pT
        book(_h["sl_ph_eta"],  4,1,1);  // photon eta
        book(_h["sl_ph_l_dR"], 5,1,1);  // photon-lepton dR
      }
      if ( _mode == 2 or _mode == 3 ){  // Dilepton channel
        book(_h["dl_ph_pt"],   6,1,1);  // photon pT
        book(_h["dl_ph_eta"],  7,1,1);  // photon eta
        book(_h["dl_ph_l_dR"], 8,1,1);  // min photon-lepton dR
        book(_h["dl_l_dEta"],  9,1,1);  // lepton-lepton dEta
        book(_h["dl_l_dPhi"],  10,1,1); // lepton-lepton dPhi
      }
    }


    void analyze(const Event& event) {

      // Fetch objects
      const vector<DressedLepton>& leptons = apply<DressedLeptons>(event, "Leptons").dressedLeptons();
      Particles photons = applyProjection<PromptFinalState>(event, "Photons").particles();
      ChargedFinalState charged = apply<ChargedFinalState>(event, "CFS");
      Jets jets = apply<JetAlg>(event, "Jets").jetsByPt(Cuts::abseta < 2.5 && Cuts::pT > 25*GeV);

      // Immediate veto on events without one good photon
      if ( photons.size() != 1 ) vetoEvent;
      const Particle& photon = photons[0];

      // Veto event if photon too close to a lepton
      for (const DressedLepton& lep : leptons) {
        if ( deltaR(lep, photon) < 1.0 ) vetoEvent;
      }

      // Overlap removel of jets near leptons
      for (const DressedLepton& lep : leptons) {
        ifilter_discard(jets, deltaRLess(lep, 0.4));
      }

      // Overlap removel of jets near isolated photon
      double conePt = 0.0;
      Particles photSurround = charged.particles(deltaRLess(photon, 0.3));
      for (const Particle& p : photSurround) {
        conePt += p.pt();
      }
      if ( conePt / photon.pT() < 0.1 ) ifilter_discard(jets, deltaRLess(photon, 0.4) );

      // Veto event if photon too close to good jets
      for (const Jet& jet : jets) {
        if ( deltaR(jet, photon) < 0.4 ) vetoEvent;
      }

      // Require at least one bjet
      unsigned int nbjets = 0;
      for (const Jet& jet : jets) {
        if ( jet.bTagged(Cuts::pT > 5*GeV) ) nbjets += 1;
      }
      if ( nbjets == 0 ) vetoEvent;

      // Fill histos in single lepton channel
      if ( _mode == 1 || _mode == 3 ) {
        if ( jets.size() >= 4 && leptons.size() == 1 ) {
          _h["sl_ph_pt"]->fill(   photon.pT()/GeV );
          _h["sl_ph_eta"]->fill(  photon.abseta() );
          _h["sl_ph_l_dR"]->fill( deltaR(leptons[0], photon) );
        }
      }

      // Fill histos in dilepton channel
      if ( _mode == 2 || _mode == 3 ) {
        if ( jets.size() >= 2 && leptons.size() == 2 ) {
          double deltaRNew;
          double deltaRMin = 999.0;
          for (const DressedLepton& lep : leptons) {
            deltaRNew = deltaR(lep, photon);
            if ( deltaRNew < deltaRMin ) deltaRMin = deltaRNew;
          }
          _h["dl_ph_pt"]->fill( photon.pT()/GeV );
          _h["dl_ph_eta"]->fill( photon.abseta() );
          _h["dl_ph_l_dR"]->fill( deltaRMin );
          _h["dl_l_dEta"]->fill( deltaEta(leptons[0], leptons[1]) );
          _h["dl_l_dPhi"]->fill( deltaPhi(leptons[0], leptons[1]) );
        }
      }
    }


    void finalize() {

      // Normalise histograms after the run
      for (auto &hist : _h) {
        normalize(hist.second, 1.0, true);
      }
    }


  private:
    int _mode;
    map<string, Histo1DPtr> _h;

  };

  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2018_I1707015);
}