rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

ATLAS_2016_I1426515

WW production at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1426515
Status: VALIDATED
Authors:
  • Kristin Lohwasser
  • Christian Gutschow
References: Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • pp -> WW production at 8 TeV

The production of $W$ boson pairs in proton--proton collisions at $\sqrt{s} = 8$ TeV is studied using data corresponding to 20.3 fb${}^{-1}$ of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The $W$ bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 $WW$ candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the $W$ branching fractions to leptons in order to obtain the total $WW$ production cross section, which is found to be $71.1 \pm 1.1$ (stat) ${}^{+5.7}_{-5.0}$ (syst) $\pm 1.4$ (lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of $63.2 {}^{+1.6}_{-1.4}$ (scale) $\pm 1.2$ (PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings.

Source code: ATLAS_2016_I1426515.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
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/DressedLeptons.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"

namespace Rivet {


  /// WW production at 8 TeV
  class ATLAS_2016_I1426515 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(ATLAS_2016_I1426515);


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

      const FinalState fs(Cuts::abseta < 4.5);

      // Project photons for dressing
      IdentifiedFinalState photon_id(fs);
      photon_id.acceptIdPair(PID::PHOTON);

      // Project dressed electrons with pT > 15 GeV and |eta| < 2.47
      PromptFinalState el_bare(FinalState(Cuts::abspid == PID::ELECTRON));
      Cut cuts = (Cuts::abseta < 2.47) && ( (Cuts::abseta <= 1.37) || (Cuts::abseta >= 1.52) ) && (Cuts::pT > 10*GeV);
      DressedLeptons el_dressed_FS(photon_id, el_bare, 0.1, cuts, true);
      declare(el_dressed_FS, "EL_DRESSED_FS");

      // Project dressed muons with pT > 15 GeV and |eta| < 2.5
      PromptFinalState mu_bare(FinalState(Cuts::abspid == PID::MUON));
      DressedLeptons mu_dressed_FS(photon_id, mu_bare, 0.1, Cuts::abseta < 2.4 && Cuts::pT > 15*GeV, true);
      declare(mu_dressed_FS, "MU_DRESSED_FS");

      Cut cuts_WW = (Cuts::abseta < 2.5) && (Cuts::pT > 20*GeV);
      IdentifiedFinalState lep_id(fs);
      lep_id.acceptIdPair(PID::MUON);
      lep_id.acceptIdPair(PID::ELECTRON);
      PromptFinalState lep_bare(lep_id);
      DressedLeptons leptons(photon_id, lep_bare, 0.1, cuts_WW, true);
      declare(leptons,"leptons");

      declare(FinalState(Cuts::abspid == PID::TAU || Cuts::abspid == PID::NU_TAU), "tau_id");

      // Get MET from generic invisibles
      VetoedFinalState ivfs(fs);
      ivfs.addVetoOnThisFinalState(VisibleFinalState(fs));
      addProjection(ivfs, "InvisibleFS");

      // Project jets
      FastJets jets(fs, FastJets::ANTIKT, 0.4, JetAlg::NO_MUONS, JetAlg::NO_INVISIBLES);
      addProjection(jets, "jets");


      // Integrated cross sections
      // d01 ee/mm fiducial integrated cross sections
      _hist_mm_fid_intxsec = bookHisto1D(1, 1, 1);
      _hist_ee_fid_intxsec = bookHisto1D(1, 1, 2);

      // d02 emme fiducial integrated cross sections
      _hist_emme_fid_intxsec = bookHisto1D(2, 1, 1);

      // d10  emme fiducial differential cross section (leading lepton ptlead + ptlead normalized)
      _hist_emme_fid_ptlead = bookHisto1D(10, 1, 1);
      _hist_emme_fid_ptleadnorm = bookHisto1D(10, 1, 2);

      // d11  emme fiducial differential cross section (dilepton-system ptll + ptll normalized)
      _hist_emme_fid_ptll = bookHisto1D(11, 1, 1);
      _hist_emme_fid_ptllnorm = bookHisto1D(11, 1, 2);

      // d12  emme fiducial differential cross section (dilepton-system mll + mll normalized)
      _hist_emme_fid_mll = bookHisto1D(12, 1, 1);
      _hist_emme_fid_mllnorm = bookHisto1D(12, 1, 2);

      // d13  emme fiducial differential cross section (dilepton-system delta_phi_ll + dphill normalized)
      _hist_emme_fid_dphill = bookHisto1D(13, 1, 1);
      _hist_emme_fid_dphillnorm = bookHisto1D(13, 1, 2);

      // d14  emme fiducial differential cross section (absolute rapidity of dilepton-system y_ll + y_ll normalized)
      _hist_emme_fid_yll = bookHisto1D(14, 1, 1);
      _hist_emme_fid_yllnorm = bookHisto1D(14, 1, 2);

      // d15  emme fiducial differential cross section (absolute costheta* of dilepton-system costhetastar_ll + costhetastar_ll normalized)
      _hist_emme_fid_costhetastarll = bookHisto1D(15, 1, 1);
      _hist_emme_fid_costhetastarllnorm = bookHisto1D(15, 1, 2);

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // Find leptons
      const FinalState& ifs = apply<VetoedFinalState>(event, "InvisibleFS");
      const vector<DressedLepton>& leptons = apply<DressedLeptons>(event, "leptons").dressedLeptons();
      const vector<DressedLepton>& good_mu = apply<DressedLeptons>(event, "MU_DRESSED_FS").dressedLeptons();
      const vector<DressedLepton>& good_el = apply<DressedLeptons>(event, "EL_DRESSED_FS").dressedLeptons();
      const Jets& jets = applyProjection<FastJets>(event, "jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 4.5);

      // Taus are excluded from the fiducial cross section
      const Particles taus = applyProjection<FinalState>(event, "tau_id").particlesByPt(Cuts::pT>12.*GeV && Cuts::abseta < 3.0);
      if (!taus.empty()) vetoEvent;

      // Remove events that do not contain 2 good leptons (either muons or electrons)
      if (leptons.size() != 2 && (good_el.size() != 1 || good_mu.size() != 1)) vetoEvent;

      // Split into channels
      int channel = -1; // 1=mm, 2=ee;  3=emu; 4=mue
      if (good_mu.size() == 2)  channel = 1; //mm
      else if (good_el.size() == 2)  channel = 2; //ee
      else if (good_mu.size() == 1 && good_el.size() == 1 && good_el[0].pT() > good_mu[0].pT())  channel = 3; //emu
      else if (good_mu.size() == 1 && good_el.size() == 1 && good_el[0].pT() < good_mu[0].pT())  channel = 4; //mue
      if (channel == -1) vetoEvent;

      // Assign leptons
      const DressedLepton *lep1, *lep2;
      if (channel == 1) { //mm
        if (good_mu[0].pT() > good_mu[1].pT()) {
          lep1 = &good_mu[0];
          lep2 = &good_mu[1];
        } else {
          lep1 = &good_mu[1];
          lep2 = &good_mu[0];
        }
      }
      else if (channel == 2) { //ee
        if (good_el[0].pT() > good_el[1].pT()) {
          lep1 = &good_el[0];
          lep2 = &good_el[1];
        } else {
          lep1 = &good_el[1];
          lep2 = &good_el[0];
        }
      }
      else if (channel == 3) { //emu
        lep1 = &good_el[0];
        lep2 = &good_mu[0];
      }
      else { // if (channel == 4) { //mue
        lep1 = &good_mu[0];
        lep2 = &good_el[0];
      }

      // Cut on leptons
      if (lep1->pT() < 25*GeV || lep2->pT() < 20*GeV)  vetoEvent;

      // Select jets isolated from electrons
      const Jets jets_selected = filter_select(jets, [&](const Jet& j){ return all(good_el, deltaRGtr(j, 0.3)); });

      // Define variables
      const FourMomentum met = sum(ifs.particles(), FourMomentum());
      const FourMomentum dilep = lep1->momentum() + lep2->momentum();
      const double ptll = dilep.pT()/GeV;
      const double Mll = dilep.mass()/GeV;
      const double Yll = dilep.absrap();
      const double DPhill = fabs(deltaPhi(*lep1, *lep2));
      const double costhetastar = fabs(tanh((lep1->eta() - lep2->eta()) / 2));

      // Calculate dphi to MET
      double DPhi_met = fabs(deltaPhi((*lep1), met));
      if (fabs(deltaPhi( (*lep2), met)) < DPhi_met)  DPhi_met = fabs(deltaPhi((*lep2), met));
      if (DPhi_met > M_PI/2) DPhi_met = 1.; else DPhi_met = fabs(sin(DPhi_met));

      // Apply selections
      // mll lower cut (reject quarkonia)
      if ((channel == 1 || channel == 2) && Mll < 15.)  vetoEvent;
      else if (Mll < 10.)  vetoEvent;

      // Z veto (reject Z -- only dilepton channels)
      if ((channel == 1 || channel == 2) && abs(Mll - 91.1876) < 15.)  vetoEvent;

      // Met rel cut
      if ((channel == 1 || channel == 2) && met.pT()*DPhi_met < 45*GeV)  vetoEvent;
      else if (met.pT()*DPhi_met < 15*GeV)  vetoEvent;

      // MET (pt-MET) cut
      if ((channel == 1 || channel == 2) && met.pT() <= 45*GeV)  vetoEvent; // begin MET cut
      else if (met.pT() <= 20*GeV)  vetoEvent;

      // Require 0 jets
      if (!jets_selected.empty()) vetoEvent;

      // Fill histograms
      const double weight = event.weight();
      if (channel == 1) {
        _hist_mm_fid_intxsec->fill(1.0, weight);

      } else if (channel == 2) {
        _hist_ee_fid_intxsec->fill(1.0, weight);

      } else if (channel == 3 || channel == 4) {
        _hist_emme_fid_intxsec->fill(1.0, weight);

        _hist_emme_fid_ptlead->fill(lep1->pT()/GeV, weight);
        _hist_emme_fid_ptleadnorm->fill(lep1->pT()/GeV, weight);

        _hist_emme_fid_ptll->fill(ptll, weight);
        _hist_emme_fid_ptllnorm->fill(ptll, weight);

        _hist_emme_fid_mll->fill(Mll, weight);
        _hist_emme_fid_mllnorm->fill(Mll, weight);

        _hist_emme_fid_dphill->fill(DPhill, weight);
        _hist_emme_fid_dphillnorm->fill(DPhill, weight);

        _hist_emme_fid_yll->fill(Yll, weight);
        _hist_emme_fid_yllnorm->fill(Yll, weight);

        _hist_emme_fid_costhetastarll->fill(costhetastar, weight);
        _hist_emme_fid_costhetastarllnorm->fill(costhetastar, weight);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      const double sf(crossSection()/femtobarn/sumOfWeights());
      scale({_hist_mm_fid_intxsec, _hist_ee_fid_intxsec, _hist_emme_fid_intxsec}, sf);
      scale({_hist_emme_fid_ptlead, _hist_emme_fid_ptll, _hist_emme_fid_mll,
            _hist_emme_fid_dphill, _hist_emme_fid_yll, _hist_emme_fid_costhetastarll}, sf);
      normalize({_hist_emme_fid_ptleadnorm, _hist_emme_fid_ptllnorm, _hist_emme_fid_mllnorm,
            _hist_emme_fid_dphillnorm, _hist_emme_fid_yllnorm, _hist_emme_fid_costhetastarllnorm});
    }


  private:

    /// @name Histograms
    //@{

    // d01 ee/mm fiducial integrated cross sections
    Histo1DPtr _hist_mm_fid_intxsec, _hist_ee_fid_intxsec;

    // d02 emme fiducial integrated cross sections
    Histo1DPtr _hist_emme_fid_intxsec;

    // d10  emme fiducial differential cross section (leading lepton ptlead + ptlead normalized)
    Histo1DPtr _hist_emme_fid_ptlead, _hist_emme_fid_ptleadnorm;

    // d11  emme fiducial differential cross section (dilepton-system ptll + ptll normalized)
    Histo1DPtr _hist_emme_fid_ptll, _hist_emme_fid_ptllnorm;

    // d12  emme fiducial differential cross section (dilepton-system mll + mll normalized)
    Histo1DPtr _hist_emme_fid_mll, _hist_emme_fid_mllnorm;

    // d13  emme fiducial differential cross section (dilepton-system delta_phi_ll + dphill normalized)
    Histo1DPtr _hist_emme_fid_dphill, _hist_emme_fid_dphillnorm;

    // d14  emme fiducial differential cross section (absolute rapidity of dilepton-system y_ll + y_ll normalized)
    Histo1DPtr _hist_emme_fid_yll, _hist_emme_fid_yllnorm;

    // d15  emme fiducial differential cross section (absolute costheta* of dilepton-system costhetastar_ll + costhetastar_ll normalized)
    Histo1DPtr _hist_emme_fid_costhetastarll, _hist_emme_fid_costhetastarllnorm;
    //@}

  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2016_I1426515);

}