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Rivet analyses reference

ATLAS_2011_I945498

Z+jets in pp at 7 TeV
Experiment: ATLAS (LHC)
Inspire ID: 945498
Status: VALIDATED
Authors:
  • Evelin Meoni
  • Holger Schulz
  • Roman Lysak
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Z+jets, electronic and/or muonic Z-decays. Jets with transverse momentum pT>30 GeV and jet rapidity |y|<4.4.

Production of jets in association with a Z/γ boson in proton--proton collisions at s=7 TeV with the ATLAS detector. The analysis includes the full 2010 data set, collected with a low rate of multiple proton--proton collisions in the accelerator, corresponding to an integrated luminosity of 36 pb1. Inclusive jet cross sections in Z/γ events, with Z/γ decaying into electron or muon pairs, are measured for jets with transverse momentum pT>30 GeV and jet rapidity |y|<4.4.

Source code: ATLAS_2011_I945498.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/DileptonFinder.hh"
  4#include "Rivet/Projections/FastJets.hh"
  5#include "Rivet/Projections/FinalState.hh"
  6#include "Rivet/Projections/VetoedFinalState.hh"
  7#include "Rivet/Projections/IdentifiedFinalState.hh"
  8#include "Rivet/Projections/LeadingParticlesFinalState.hh"
  9
 10namespace Rivet {
 11
 12
 13  /// ATLAS Z+jets in pp at 7 TeV
 14  class ATLAS_2011_I945498 : public Analysis {
 15  public:
 16
 17    /// Constructor
 18    ATLAS_2011_I945498()
 19      : Analysis("ATLAS_2011_I945498")
 20    {    }
 21
 22
 23    /// Book histograms and initialise projections before the run
 24    void init() {
 25
 26      // Variable initialisation
 27      _isZeeSample = false;
 28      _isZmmSample = false;
 29      for (size_t chn = 0; chn < 3; ++chn) {
 30        book(weights_nj0[chn], "weights_nj0_" + to_str(chn));
 31        book(weights_nj1[chn], "weights_nj1_" + to_str(chn));
 32        book(weights_nj2[chn], "weights_nj2_" + to_str(chn));
 33        book(weights_nj3[chn], "weights_nj3_" + to_str(chn));
 34        book(weights_nj4[chn], "weights_nj4_" + to_str(chn));
 35      }
 36
 37      // Set up projections
 38      Cut cuts_mu = Cuts::abseta < 2.4 && Cuts::pT > 20*GeV;
 39      DileptonFinder zfinder_mu(91.2*GeV, 0.1, cuts_mu && Cuts::abspid == PID::MUON, Cuts::massIn(66*GeV, 116*GeV));
 40      declare(zfinder_mu, "DileptonFinder_mu");
 41
 42      Cut cuts_e = (Cuts::abseta < 1.37 || Cuts::absetaIn(1.52, 2.47)) && Cuts::pT > 20*GeV;
 43      DileptonFinder zfinder_el(91.2*GeV, 0.1, cuts_e && Cuts::abspid == PID::ELECTRON, Cuts::massIn(66*GeV, 116*GeV));
 44      declare(zfinder_el, "DileptonFinder_el");
 45
 46      // For combined cross-sections (combined phase space + dressed level)
 47      Cut cuts25_20 = Cuts::abseta < 2.5 && Cuts::pT > 20*GeV;
 48      DileptonFinder zfinder_comb_mu(91.2*GeV, 0.1, cuts25_20 && Cuts::abspid == PID::MUON, Cuts::massIn(66.0*GeV, 116.0*GeV));
 49      declare(zfinder_comb_mu, "DileptonFinder_comb_mu");
 50      DileptonFinder zfinder_comb_el(91.2*GeV, 0.1, cuts25_20 && Cuts::abspid == PID::ELECTRON, Cuts::massIn(66.0*GeV, 116.0*GeV));
 51      declare(zfinder_comb_el, "DileptonFinder_comb_el");
 52
 53      // Define veto FS in order to prevent Z-decay products entering the jet algorithm
 54      VetoedFinalState remfs;
 55      remfs.addVetoOnThisFinalState(zfinder_el);
 56      remfs.addVetoOnThisFinalState(zfinder_mu);
 57      VetoedFinalState remfs_comb;
 58      remfs_comb.addVetoOnThisFinalState(zfinder_comb_el);
 59      remfs_comb.addVetoOnThisFinalState(zfinder_comb_mu);
 60
 61      FastJets jets(remfs, JetAlg::ANTIKT, 0.4);
 62      jets.useInvisibles();
 63      declare(jets, "jets");
 64      FastJets jets_comb(remfs_comb, JetAlg::ANTIKT, 0.4);
 65      jets_comb.useInvisibles();
 66      declare(jets_comb, "jets_comb");
 67
 68      // 0=el, 1=mu, 2=comb
 69      for (size_t chn = 0; chn < 3; ++chn) {
 70        book(_h_njet_incl[chn]  ,1, 1, chn+1);
 71        book(_h_njet_ratio[chn] ,2, 1, chn+1);
 72        book(_h_ptjet[chn]      ,3, 1, chn+1);
 73        book(_h_ptlead[chn]     ,4, 1, chn+1);
 74        book(_h_ptseclead[chn]  ,5, 1, chn+1);
 75        book(_h_yjet[chn]       ,6, 1, chn+1);
 76        book(_h_ylead[chn]      ,7, 1, chn+1);
 77        book(_h_yseclead[chn]   ,8, 1, chn+1);
 78        book(_h_mass[chn]       ,9, 1, chn+1);
 79        book(_h_deltay[chn]     ,10, 1, chn+1);
 80        book(_h_deltaphi[chn]   ,11, 1, chn+1);
 81        book(_h_deltaR[chn]     ,12, 1, chn+1);
 82      }
 83    }
 84
 85
 86    // Jet selection criteria universal for electron and muon channel
 87    /// @todo Replace with a Cut passed to jetsByPt
 88    Jets selectJets(const DileptonFinder* zf, const FastJets* allJets) {
 89      const FourMomentum l1 = zf->constituents()[0].momentum();
 90      const FourMomentum l2 = zf->constituents()[1].momentum();
 91      Jets jets;
 92      for (const Jet& jet : allJets->jetsByPt(Cuts::pT > 30*GeV)) {
 93        const FourMomentum jmom = jet.momentum();
 94        if (jmom.absrap() < 4.4 &&
 95            deltaR(l1, jmom) > 0.5  && deltaR(l2, jmom) > 0.5) {
 96          jets.push_back(jet);
 97        }
 98      }
 99      return jets;
100    }
101
102
103    /// Perform the per-event analysis
104    void analyze(const Event& event) {
105      vector<const DileptonFinder*> zfs;
106      zfs.push_back(& (apply<DileptonFinder>(event, "DileptonFinder_el")));
107      zfs.push_back(& (apply<DileptonFinder>(event, "DileptonFinder_mu")));
108      zfs.push_back(& (apply<DileptonFinder>(event, "DileptonFinder_comb_el")));
109      zfs.push_back(& (apply<DileptonFinder>(event, "DileptonFinder_comb_mu")));
110
111      vector<const FastJets*> fjs;
112      fjs.push_back(& (apply<FastJets>(event, "jets")));
113      fjs.push_back(& (apply<FastJets>(event, "jets_comb")));
114
115      // Determine what kind of MC sample this is
116      const bool isZee = (zfs[0]->bosons().size() == 1) || (zfs[2]->bosons().size() == 1);
117      const bool isZmm = (zfs[1]->bosons().size() == 1) || (zfs[3]->bosons().size() == 1);
118      if (isZee) _isZeeSample = true;
119      if (isZmm) _isZmmSample = true;
120
121      // Require exactly one electronic or muonic Z-decay in the event
122      bool isZeemm = ( (zfs[0]->bosons().size() == 1 && zfs[1]->bosons().size() != 1) ||
123                       (zfs[1]->bosons().size() == 1 && zfs[0]->bosons().size() != 1) );
124      bool isZcomb = ( (zfs[2]->bosons().size() == 1 && zfs[3]->bosons().size() != 1) ||
125                       (zfs[3]->bosons().size() == 1 && zfs[2]->bosons().size() != 1) );
126      if (!isZeemm && !isZcomb) vetoEvent;
127
128      vector<int> zfIDs;
129      vector<int> fjIDs;
130      if (isZeemm) {
131        int chn = zfs[0]->bosons().size() == 1 ? 0 : 1;
132        zfIDs.push_back(chn);
133        fjIDs.push_back(0);
134      }
135      if (isZcomb) {
136        int chn = zfs[2]->bosons().size() == 1 ? 2 : 3;
137        zfIDs.push_back(chn);
138        fjIDs.push_back(1);
139      }
140
141      for (size_t izf = 0; izf < zfIDs.size(); ++izf) {
142        int zfID = zfIDs[izf];
143        int fjID = fjIDs[izf];
144
145        int chn = zfID;
146        if (zfID == 2 || zfID == 3) chn = 2;
147
148        Jets jets = selectJets(zfs[zfID], fjs[fjID]);
149
150        switch (jets.size()) {
151        case 0:
152          weights_nj0[chn]->fill();
153          break;
154        case 1:
155          weights_nj0[chn]->fill();
156          weights_nj1[chn]->fill();
157          break;
158        case 2:
159          weights_nj0[chn]->fill();
160          weights_nj1[chn]->fill();
161          weights_nj2[chn]->fill();
162          break;
163        case 3:
164          weights_nj0[chn]->fill();
165          weights_nj1[chn]->fill();
166          weights_nj2[chn]->fill();
167          weights_nj3[chn]->fill();
168          break;
169        default: // >= 4
170          weights_nj0[chn]->fill();
171          weights_nj1[chn]->fill();
172          weights_nj2[chn]->fill();
173          weights_nj3[chn]->fill();
174          weights_nj4[chn]->fill();
175        }
176
177        // Require at least one jet
178        if (jets.empty()) continue;
179
180        // Fill jet multiplicities
181        for (size_t ijet = 1; ijet <= jets.size(); ++ijet) {
182          _h_njet_incl[chn]->fill(ijet);
183        }
184
185        // Loop over selected jets, fill inclusive jet distributions
186        for (size_t ijet = 0; ijet < jets.size(); ++ijet) {
187          _h_ptjet[chn]->fill(jets[ijet].pT()/GeV);
188          _h_yjet [chn]->fill(fabs(jets[ijet].rapidity()));
189        }
190
191        // Leading jet histos
192        const double ptlead   = jets[0].pT()/GeV;
193        const double yabslead = fabs(jets[0].rapidity());
194        _h_ptlead[chn]->fill(ptlead);
195        _h_ylead [chn]->fill(yabslead);
196
197        if (jets.size() >= 2) {
198          // Second jet histos
199          const double pt2ndlead   = jets[1].pT()/GeV;
200          const double yabs2ndlead = fabs(jets[1].rapidity());
201          _h_ptseclead[chn] ->fill(pt2ndlead);
202          _h_yseclead [chn] ->fill(yabs2ndlead);
203
204          // Dijet histos
205          const double deltaphi = fabs(deltaPhi(jets[1], jets[0]));
206          const double deltarap = fabs(jets[0].rapidity() - jets[1].rapidity()) ;
207          const double deltar   = fabs(deltaR(jets[0], jets[1], RAPIDITY));
208          const double mass     = (jets[0].momentum() + jets[1].momentum()).mass();
209          _h_mass    [chn] ->fill(mass/GeV);
210          _h_deltay  [chn] ->fill(deltarap);
211          _h_deltaphi[chn] ->fill(deltaphi);
212          _h_deltaR  [chn] ->fill(deltar);
213        }
214      }
215    }
216
217
218    /// @name Ratio calculator util functions
219    /// @{
220
221    /// Calculate the ratio, being careful about div-by-zero
222    double ratio(double a, double b) {
223      return (b != 0) ? a/b : 0;
224    }
225
226    /// Calculate the ratio error, being careful about div-by-zero
227    double ratio_err(double a, double b) {
228      return (b != 0) ? sqrt(a/sqr(b) + sqr(a)/(b*b*b)) : 0;
229    }
230
231    /// @}
232
233
234    void finalize() {
235      // Fill ratio histograms
236      for (size_t chn = 0; chn < 3; ++chn) {
237        _h_njet_ratio[chn]->bin(1).set(ratio(weights_nj1[chn]->val(), weights_nj0[chn]->val()),
238                                       ratio_err(weights_nj1[chn]->val(), weights_nj0[chn]->val()));
239        _h_njet_ratio[chn]->bin(2).set(ratio(weights_nj2[chn]->val(), weights_nj1[chn]->val()),
240                                       ratio_err(weights_nj2[chn]->val(), weights_nj1[chn]->val()));
241        _h_njet_ratio[chn]->bin(3).set(ratio(weights_nj3[chn]->val(), weights_nj2[chn]->val()),
242                                       ratio_err(weights_nj3[chn]->val(), weights_nj2[chn]->val()));
243        _h_njet_ratio[chn]->bin(4).set(ratio(weights_nj4[chn]->val(), weights_nj3[chn]->val()),
244                                       ratio_err(weights_nj4[chn]->val(), weights_nj3[chn]->val()));
245      }
246
247      // Scale other histos
248      for (size_t chn = 0; chn < 3; ++chn) {
249        // For ee and mumu channels: normalize to Njet inclusive cross-section
250        double xs = crossSectionPerEvent()/picobarn;
251        if (chn != 2 && weights_nj0[chn]->val() != 0.)  xs = 1.0 / weights_nj0[chn]->val();
252        // For inclusive MC sample(ee/mmu channels together) we want the single-lepton-flavor xsec
253        if (_isZeeSample && _isZmmSample) xs *= 0.5;
254
255        // Special case histogram: always not normalized
256        scale(_h_njet_incl[chn], (chn < 2) ? crossSectionPerEvent()/picobarn : xs);
257
258        scale(_h_ptjet[chn]    , xs);
259        scale(_h_ptlead[chn]   , xs);
260        scale(_h_ptseclead[chn], xs);
261        scale(_h_yjet[chn]     , xs);
262        scale(_h_ylead[chn]    , xs);
263        scale(_h_yseclead[chn] , xs);
264        scale(_h_deltaphi[chn] , xs);
265        scale(_h_deltay[chn]   , xs);
266        scale(_h_deltaR[chn]   , xs);
267        scale(_h_mass[chn]     , xs);
268      }
269
270    }
271
272    /// @}
273
274
275  private:
276
277    bool _isZeeSample;
278    bool _isZmmSample;
279
280    CounterPtr weights_nj0[3];
281    CounterPtr weights_nj1[3];
282    CounterPtr weights_nj2[3];
283    CounterPtr weights_nj3[3];
284    CounterPtr weights_nj4[3];
285
286    Estimate1DPtr _h_njet_ratio[3];
287    Histo1DPtr _h_njet_incl[3];
288    Histo1DPtr _h_ptjet[3];
289    Histo1DPtr _h_ptlead[3];
290    Histo1DPtr _h_ptseclead[3];
291    Histo1DPtr _h_yjet[3];
292    Histo1DPtr _h_ylead[3];
293    Histo1DPtr _h_yseclead[3];
294    Histo1DPtr _h_deltaphi[3];
295    Histo1DPtr _h_deltay[3];
296    Histo1DPtr _h_deltaR[3];
297    Histo1DPtr _h_mass[3];
298
299  };
300
301
302  RIVET_DECLARE_PLUGIN(ATLAS_2011_I945498);
303
304
305}