Rivet analyses

title: ATLAS_2011_I894578

Two-lepton supersymmetry search

Experiment: ATLAS (LHC)

Inspire ID: 894578

Status: VALIDATED

Authors: - Angela Chen

References: - Expt page: ATLAS-SUSY-2011-05 - arXiv: 1103.6214

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - BSM signal events at 7000 GeV.

2-lepton search for supersymmetric particles by ATLAS at 7 TeV. Event counts in signal regions (3 same sign and 3 opposite sign) are implemented as one bin histograms. Histograms for missing transverse energy are implemented.

Source code:ATLAS_2011_I894578.cc

```c++ // -- 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/VetoedFinalState.hh"

include "Rivet/Projections/VisibleFinalState.hh"

namespace Rivet {

/// Two-lepton supersymmetry search class ATLAS_2011_I894578 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2011_I894578);


/// @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");


  // veto region electrons
  Cut vetocut = Cuts::absetaIn(1.37, 1.52);
  IdentifiedFinalState veto_elecs(vetocut && Cuts::pT > 10 * GeV);
  veto_elecs.acceptIdPair(PID::ELECTRON);
  declare(veto_elecs, "veto_elecs");


  // projection to find the muons
  IdentifiedFinalState muons(Cuts::abseta < 2.4 && Cuts::pT > 20 * GeV);
  muons.acceptIdPair(PID::MUON);
  declare(muons, "muons");


  // jet finder
  VetoedFinalState vfs;
  vfs.addVetoPairId(PID::MUON);
  declare(FastJets(vfs, JetAlg::ANTIKT, 0.4), "AntiKtJets04");


  // all tracks (to do deltaR with leptons)
  declare(ChargedFinalState(Cuts::abseta < 3 && Cuts::pT > 0.5 * GeV), "cfs");


  // for pTmiss
  declare(VisibleFinalState(Cuts::abseta < 4.9), "vfs");


  /// book histograms
  book(_count_OS_e_mu, "count_OS_e+-mu-+", 1, 0., 1.);
  book(_count_OS_e_e, "count_OS_e+e-", 1, 0., 1.);
  book(_count_OS_mu_mu, "count_OS_mu+mu-", 1, 0., 1.);
  book(_count_SS_e_mu, "count_SS_e+-mu+-", 1, 0., 1.);
  book(_count_SS_e_e, "count_SS_e+-e+-", 1, 0., 1.);
  book(_count_SS_mu_mu, "count_SS_mu+-mu+-", 1, 0., 1.);

  book(_hist_eTmiss_OS, "Et_miss_OS", 20, 0., 400.);
  book(_hist_eTmiss_SS, "Et_miss_SS", 20, 0., 400.);
}


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


  Particles veto_e = apply<IdentifiedFinalState>(event, "veto_elecs").particles();
  if (!veto_e.empty()) {
    MSG_DEBUG("electrons in veto region");
    vetoEvent;
  }

  Jets cand_jets = apply<FastJets>(event, "AntiKtJets04")
                       .jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 2.5);

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

  // charged particle for isolation
  Particles chg_tracks = apply<ChargedFinalState>(event, "cfs").particles();

  // apply muon isolation
  Particles cand_mu;
  // pTcone around muon track
  for (const Particle& mu : apply<IdentifiedFinalState>(event, "muons").particlesByPt()) {
    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);
  }

  // Discard jets that overlap with electrons
  Jets recon_jets;
  for (const Jet& jet : cand_jets) {
    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) recon_jets.push_back(jet);
  }

  // Leptons far from jet
  Particles recon_e;
  for (const Particle& e : cand_e) {
    bool e_near_jet = false;
    for (const Jet& jet : recon_jets) {
      if (deltaR(e.momentum(), jet.momentum()) < 0.4) {
        e_near_jet = true;
        break;
      }
    }
    // Electron isolation criterion
    if (!e_near_jet) {
      double EtinCone = -e.Et();
      for (const Particle& track : chg_tracks) {
        if (deltaR(e.momentum(), track.momentum()) <= 0.2) EtinCone += track.Et();
      }
      if (EtinCone / e.pT() <= 0.15) recon_e.push_back(e);
    }
  }

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


  // pTmiss
  Particles vfs_particles = apply<VisibleFinalState>(event, "vfs").particles();
  FourMomentum pTmiss;
  for (const Particle& p : vfs_particles) {
    pTmiss -= p.momentum();
  }
  double eTmiss = pTmiss.pT();

  // Exactly two leptons for each event
  if (recon_mu.size() + recon_e.size() != 2) vetoEvent;

  // Lepton pair mass
  FourMomentum p_leptons;
  for (Particle e : recon_e) {
    p_leptons += e.momentum();
  }
  for (Particle mu : recon_mu) {
    p_leptons += mu.momentum();
  }

  if (p_leptons.mass() <= 5.0 * GeV) vetoEvent;

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


  // electron, electron
  if (recon_e.size() == 2) {

    // SS ee
    if (recon_e[0].pid() * recon_e[1].pid() > 0) {
      _hist_eTmiss_SS->fill(eTmiss);
      if (eTmiss > 100) {
        MSG_DEBUG("Hits SS e+/-e+/-");
        _count_SS_e_e->fill(0.5);
      }
    }

    // OS ee
    else if (recon_e[0].pid() * recon_e[1].pid() < 0) {
      _hist_eTmiss_OS->fill(eTmiss);
      if (eTmiss > 150) {
        MSG_DEBUG("Hits OS e+e-");
        _count_OS_e_e->fill(0.5);
      }
    }
  }


  // muon, electron
  else if (recon_e.size() == 1) {

    // SS mu_e
    if (recon_e[0].pid() * recon_mu[0].pid() > 0) {
      _hist_eTmiss_SS->fill(eTmiss);
      if (eTmiss > 100) {
        MSG_DEBUG("Hits SS e+/-mu+/-");
        _count_SS_e_mu->fill(0.5);
      }
    }

    // OS mu_e
    else if (recon_e[0].pid() * recon_mu[0].pid() < 0) {
      _hist_eTmiss_OS->fill(eTmiss);
      if (eTmiss > 150) {
        MSG_DEBUG("Hits OS e+mu-");
        _count_OS_e_mu->fill(0.5);
      }
    }
  }


  // muon, muon
  else if (recon_mu.size() == 2) {

    // SS mu_mu
    if (recon_mu[0].pid() * recon_mu[1].pid() > 0) {
      _hist_eTmiss_SS->fill(eTmiss);
      if (eTmiss > 100) {
        MSG_DEBUG("Hits SS mu+/-mu+/-");
        _count_SS_mu_mu->fill(0.5);
      }
    }

    // OS mu_mu
    else if (recon_mu[0].pid() * recon_mu[1].pid() < 0) {
      _hist_eTmiss_OS->fill(eTmiss);
      if (eTmiss > 150) {
        MSG_DEBUG("Hits OS mu+mu-");
        _count_OS_mu_mu->fill(0.5);
      }
    }
  }
}

/// @}


void finalize() {
  double norm = crossSection() / picobarn * 35. / sumOfWeights();
  // event counts
  scale(_count_OS_e_mu, norm);
  scale(_count_OS_e_e, norm);
  scale(_count_OS_mu_mu, norm);
  scale(_count_SS_e_mu, norm);
  scale(_count_SS_e_e, norm);
  scale(_count_SS_mu_mu, norm);
  scale(_hist_eTmiss_OS, 10. * norm);
  scale(_hist_eTmiss_SS, 10. * norm);
}

private:

/// @name Histograms
/// @{
Histo1DPtr _count_OS_e_mu;
Histo1DPtr _count_OS_e_e;
Histo1DPtr _count_OS_mu_mu;
Histo1DPtr _count_SS_e_mu;
Histo1DPtr _count_SS_e_e;
Histo1DPtr _count_SS_mu_mu;
Histo1DPtr _hist_eTmiss_OS;
Histo1DPtr _hist_eTmiss_SS;
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(ATLAS_2011_I894578, ATLAS_2011_S9019561);

} ```

Aliases: - ATLAS_2011_S9019561