Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"

namespace Rivet {


  /// @brief 0-lepton squark and gluino search
  ///
  /// @author Chris Wymant
  class ATLAS_2011_I930002 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2011_I930002);


    /// @name Analysis methods
    /// @{

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

      // Projection to find the electrons
      IdentifiedFinalState elecs(Cuts::abseta < 2.47 && Cuts::pT > 20 * GeV);
      elecs.acceptIdPair(PID::ELECTRON);
      declare(elecs, "elecs");

      // Projection to find the muons
      IdentifiedFinalState muons(Cuts::abseta < 2.4 && Cuts::pT > 10 * GeV);
      muons.acceptIdPair(PID::MUON);
      declare(muons, "muons");

      // Jet finder
      declare(FastJets(FinalState(), JetAlg::ANTIKT, 0.4), "AntiKtJets04");

      // All tracks (to do deltaR with leptons)
      declare(ChargedFinalState(Cuts::abseta < 3.0), "cfs");

      // Used for pTmiss (N.B. the real 'vfs' extends beyond 4.5 to |eta| = 4.9)
      declare(VisibleFinalState(Cuts::abseta < 4.5), "vfs");


      // Book histograms
      book(_count_2j, "count_2j", 1, 0., 1.);
      book(_count_3j, "count_3j", 1, 0., 1.);
      book(_count_4j5, "count_4j5", 1, 0., 1.);
      book(_count_4j10, "count_4j10", 1, 0., 1.);
      book(_count_HM, "count_HM", 1, 0., 1.);

      book(_hist_meff_2j, 1, 1, 1);
      book(_hist_meff_3j, 2, 1, 1);
      book(_hist_meff_4j, 3, 1, 1);
      book(_hist_meff_HM, 4, 1, 1);

      book(_hist_eTmiss, "Et_miss", 20, 0., 1000.);
    }


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

      const Jets& cand_jets = apply<FastJets>(event, "AntiKtJets04")
                                  .jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 4.9);

      const Particles cand_e = apply<IdentifiedFinalState>(event, "elecs").particlesByPt();

      // Muon isolation not mentioned in hep-exp 1109.6572, unlike in 1102.5290,
      // but assumed to still be applicable
      Particles cand_mu;
      const Particles chg_tracks = apply<ChargedFinalState>(event, "cfs").particles();
      const Particles muons = apply<IdentifiedFinalState>(event, "muons").particlesByPt();
      for (const Particle& mu : muons) {
        double pTinCone = -mu.pT();
        for (const Particle& track : chg_tracks) {
          if (deltaR(mu.momentum(), track.momentum()) <= 0.2) {
            pTinCone += track.pT();
          }
        }
        if (pTinCone < 1.8 * GeV) cand_mu.push_back(mu);
      }

      // Resolve jet-lepton overlap for jets with |eta| < 2.8
      Jets cand_jets_2;
      for (const Jet& jet : cand_jets) {
        if (fabs(jet.eta()) >= 2.8) {
          cand_jets_2.push_back(jet);
        }
        else {
          bool away_from_e = true;
          for (const Particle& e : cand_e) {
            if (deltaR(e.momentum(), jet.momentum()) <= 0.2) {
              away_from_e = false;
              break;
            }
          }
          if (away_from_e) cand_jets_2.push_back(jet);
        }
      }


      Particles recon_e, recon_mu;

      for (const Particle& e : cand_e) {
        bool away = true;
        for (const Jet& jet : cand_jets_2) {
          if (deltaR(e.momentum(), jet.momentum()) < 0.4) {
            away = false;
            break;
          }
        }
        if (away) recon_e.push_back(e);
      }

      for (const Particle& mu : cand_mu) {
        bool away = true;
        for (const Jet& jet : cand_jets_2) {
          if (deltaR(mu.momentum(), jet.momentum()) < 0.4) {
            away = false;
            break;
          }
        }
        if (away) recon_mu.push_back(mu);
      }


      // pTmiss
      // Based on all candidate electrons, muons and jets, plus everything else with |eta| < 4.5
      // i.e. everything in our projection "vfs" plus the jets with |eta| > 4.5
      Particles vfs_particles = apply<VisibleFinalState>(event, "vfs").particles();
      FourMomentum pTmiss;
      for (const Particle& p : vfs_particles) {
        pTmiss -= p.momentum();
      }
      for (const Jet& jet : cand_jets_2) {
        if (fabs(jet.eta()) > 4.5) pTmiss -= jet.momentum();
      }
      double eTmiss = pTmiss.pT();


      // Final jet filter
      Jets recon_jets;
      for (const Jet& jet : cand_jets_2) {
        if (fabs(jet.eta()) <= 2.8) recon_jets.push_back(jet);
      }
      // NB. It seems that jets with |eta| > 2.8 could have been thrown away at
      // the start; we don't do so, in order to follow both the structure of
      // the paper and the similar Rivet analysis ATLAS_2011_S8983313

      // 'candidate' muons needed only 10 GeV, to cause a veto they need 20 GeV
      Particles veto_mu;
      for (const Particle& mu : cand_mu) {
        if (mu.pT() >= 20.0 * GeV) veto_mu.push_back(mu);
      }

      if (!(veto_mu.empty() && recon_e.empty())) {
        MSG_DEBUG("Charged leptons left after selection");
        vetoEvent;
      }

      if (eTmiss <= 130 * GeV) {
        MSG_DEBUG("Not enough eTmiss: " << eTmiss << " < 130");
        vetoEvent;
      }

      if (recon_jets.empty() || recon_jets[0].pT() <= 130.0 * GeV) {
        MSG_DEBUG("No hard leading jet in " << recon_jets.size() << " jets");
        vetoEvent;
      }

      // ==================== observables ====================

      int Njets = 0;
      double min_dPhi = 999.999;
      double pTmiss_phi = pTmiss.phi();
      for (const Jet& jet : recon_jets) {
        if (jet.pT() > 40 * GeV) {
          if (Njets < 3) {
            min_dPhi = min(min_dPhi, deltaPhi(pTmiss_phi, jet.phi()));
          }
          ++Njets;
        }
      }

      int NjetsHighMass = 0;
      for (const Jet& jet : recon_jets) {
        if (jet.pT() > 80.0 * GeV) {
          ++NjetsHighMass;
        }
      }

      if (Njets < 2) {
        MSG_DEBUG("Only " << Njets << " >40 GeV jets left");
        vetoEvent;
      }

      if (min_dPhi <= 0.4) {
        MSG_DEBUG("dPhi too small");
        vetoEvent;
      }

      // m_eff
      double m_eff_2j = eTmiss + recon_jets[0].pT() + recon_jets[1].pT();
      double m_eff_3j = recon_jets.size() < 3 ? -999.0 : m_eff_2j + recon_jets[2].pT();
      double m_eff_4j = recon_jets.size() < 4 ? -999.0 : m_eff_3j + recon_jets[3].pT();
      double m_eff_HM = eTmiss;
      for (const Jet& jet : recon_jets) {
        if (jet.pT() > 40.0 * GeV) m_eff_HM += jet.pT();
      }

      double et_meff_2j = eTmiss / m_eff_2j;
      double et_meff_3j = eTmiss / m_eff_3j;
      double et_meff_4j = eTmiss / m_eff_4j;
      double et_meff_HM = eTmiss / m_eff_HM;


      // ==================== FILL ====================

      MSG_DEBUG("Trying to fill " << Njets << ' ' << m_eff_2j << ' ' << et_meff_2j << ' ' << m_eff_3j << ' '
                                  << et_meff_3j << ' ' << m_eff_4j << ' ' << et_meff_4j << ' ' << m_eff_HM
                                  << ' ' << et_meff_HM);


      _hist_eTmiss->fill(eTmiss);


      // 2j region
      if (et_meff_2j > 0.3) {
        _hist_meff_2j->fill(m_eff_2j);
        if (m_eff_2j > 1000 * GeV) {
          MSG_DEBUG("Hits 2j");
          _count_2j->fill(0.5);
        }
      }


      // 3j region
      if (Njets >= 3 && et_meff_3j > 0.25) {
        _hist_meff_3j->fill(m_eff_3j);
        if (m_eff_3j > 1000 * GeV) {
          MSG_DEBUG("Hits 3j");
          _count_3j->fill(0.5);
        }
      }


      // 4j5 & 4j10 regions
      if (Njets >= 4 && et_meff_4j > 0.25) {
        _hist_meff_4j->fill(m_eff_4j);
        if (m_eff_4j > 500 * GeV) {
          MSG_DEBUG("Hits 4j5");
          _count_4j5->fill(0.5);
        }
        if (m_eff_4j > 1000 * GeV) {
          MSG_DEBUG("Hits 4j10");
          _count_4j10->fill(0.5);
        }
      }


      // High mass region
      if (NjetsHighMass >= 4 && et_meff_HM > 0.2) {
        _hist_meff_HM->fill(m_eff_HM);
        if (m_eff_HM > 1100 * GeV) {
          MSG_DEBUG("Hits HM");
          _count_HM->fill(0.5);
        }
      }
    }


    void finalize() {
      // Two, three and four jet channels have bin width = 100 (GeV)
      // High mass channel has bin width = 150 (GeV)
      // Integrated luminosity = 1040 (pb)
      scale(_hist_meff_2j, 100. * 1040 * crossSection() / picobarn / sumOfWeights());
      scale(_hist_meff_3j, 100. * 1040 * crossSection() / picobarn / sumOfWeights());
      scale(_hist_meff_4j, 100. * 1040 * crossSection() / picobarn / sumOfWeights());
      scale(_hist_meff_HM, 150. * 1040 * crossSection() / picobarn / sumOfWeights());
    }

    /// @}


  private:

    Histo1DPtr _count_2j;
    Histo1DPtr _count_3j;
    Histo1DPtr _count_4j5;
    Histo1DPtr _count_4j10;
    Histo1DPtr _count_HM;
    Histo1DPtr _hist_meff_2j;
    Histo1DPtr _hist_meff_3j;
    Histo1DPtr _hist_meff_4j;
    Histo1DPtr _hist_meff_HM;
    Histo1DPtr _hist_eTmiss;
  };


  RIVET_DECLARE_ALIASED_PLUGIN(ATLAS_2011_I930002, ATLAS_2011_S9212183);

}