Rivet analyses

title: ATLAS_2011_CONF_2011_098

b-jets search for supersymmetry with 0-leptons

Experiment: ATLAS (LHC)

Inspire ID: 1204184

Status: OBSOLETE

Authors: - Angela Chen

References: - ATLAS_2011_CONF_2011_098

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - BSM signal events at 7000 GeV.

Search for supersymmmetric particles by ATLAS at 7 TeV in events with b-jets, large missing energy, and no leptons. Event counts in four signal regions (1 b-jet, $m_eff>500$\,GeV; 1 b-jet, $m_eff>700$\,GeV; 2 b-jets, $m_eff>500$\,GeV; 2 b-jets, $m_eff>700$\,GeV) are implemented as one-bin histograms. Histograms for missing transverse energy, effective mass, and pT of the leading jet are implemented for the 1 b-tag and 2 b-tag signal regions.

Source code:ATLAS_2011_CONF_2011_098.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/VisibleFinalState.hh"

include "Rivet/Tools/Random.hh"

namespace Rivet {

class ATLAS_2011_CONF_2011_098 : public Analysis { public:

/// Constructor
ATLAS_2011_CONF_2011_098()
    : Analysis("ATLAS_2011_CONF_2011_098"),
      //debug variables
      threeJA(0),
      threeJB(0),
      threeJC(0),
      threeJD(0),
      bj(0),
      jets(0),
      zerolept(0),
      eTmisscut(0) { }


/// @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");

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


  /// Book histograms
  book(_count_threeJA, "count_threeJA", 1, 0., 1.);
  book(_count_threeJB, "count_threeJB", 1, 0., 1.);
  book(_count_threeJC, "count_threeJC", 1, 0., 1.);
  book(_count_threeJD, "count_threeJD", 1, 0., 1.);
  book(_hist_meff_1bjet, "meff_1bjet", 32, 0., 1600.);
  book(_hist_eTmiss_1bjet, "eTmiss_1bjet", 6, 0., 600.);
  book(_hist_pTj_1bjet, "pTjet_1bjet", 20, 0., 800.);
  book(_hist_meff_2bjet, "meff_2bjet", 32, 0., 1600.);
  book(_hist_eTmiss_2bjet, "eTmiss_2bjet", 6, 0., 600.);
  book(_hist_pTj_2bjet, "pTjet_2bjet", 20, 0., 800.);
}


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


  // Temp: calorimeter module failure with 10% acceptance loss;
  // region unknown ==> randomly choose 10% of events to be vetoed

  if (rand01() < 0.1) vetoEvent;

  Jets tmp_cand_jets = apply<FastJets>(event, "AntiKtJets04")
                           .jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 2.8);

  Particles cand_e = apply<IdentifiedFinalState>(event, "elecs").particlesByPt();
  Particles cand_mu = apply<IdentifiedFinalState>(event, "muons").particlesByPt();
  Particles chg_tracks = apply<ChargedFinalState>(event, "cfs").particles();

  //cerr << "cand_e.size(): " << cand_e.size() << "   cand_mu.size(): " << cand_mu.size() << '\n';


  Jets cand_jets;
  for (const Jet& jet : tmp_cand_jets) {
    if (fabs(jet.eta()) >= 2.8)
      cand_jets.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.push_back(jet);
    }
  }

  Particles cand_lept;

  bool isolated_e;
  for (const Particle& e : cand_e) {
    isolated_e = true;
    for (const Jet& jet : cand_jets) {
      if (deltaR(e.momentum(), jet.momentum()) < 0.4) isolated_e = false;
    }
    if (isolated_e == true) cand_lept.push_back(e);
  }


  bool isolated_mu;
  for (const Particle& mu : cand_mu) {
    isolated_mu = true;
    for (const Jet& jet : cand_jets) {
      if (deltaR(mu.momentum(), jet.momentum()) < 0.4) isolated_mu = false;
    }
    if (isolated_mu == true) cand_lept.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();


  // bjets
  Jets bjets, recon_jets;
  for (const Jet& j : cand_jets) {
    if (fabs(j.eta()) <= 2.8) {
      recon_jets.push_back(j);
      if (fabs(j.eta()) <= 2.5 && j.perp() > 50. && j.bTagged() && rand01() < 0.5) bjets.push_back(j);
    }
  }

  if (bjets.empty()) {
    MSG_DEBUG("No b-jet axes in acceptance");
    vetoEvent;
  }

  ++bj;


  // Jets event selection
  if (recon_jets.size() < 3) vetoEvent;
  if (recon_jets[0].pT() <= 130 * GeV) vetoEvent;
  if (recon_jets[1].pT() <= 50 * GeV || recon_jets[2].pT() <= 50 * GeV) vetoEvent;
  ++jets;

  // eTmiss cut
  if (eTmiss <= 130 * GeV) vetoEvent;

  ++eTmisscut;

  // 0-lepton requirement
  if (!cand_lept.empty()) vetoEvent;
  ++zerolept;

  // m_eff cut
  double m_eff = eTmiss + recon_jets[0].pT() + recon_jets[1].pT() + recon_jets[2].pT();

  if (eTmiss / m_eff <= 0.25) vetoEvent;


  // min_dPhi
  double min_dPhi = 999.999;
  for (int i = 0; i < 3; ++i) {
    double dPhi = deltaPhi(pTmiss.phi(), recon_jets[i].phi());
    min_dPhi = min(min_dPhi, dPhi);
  }

  if (min_dPhi <= 0.4) vetoEvent;


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


  // 1 bjet
  if (bjets.size() >= 1) {

    _hist_meff_1bjet->fill(m_eff);
    _hist_eTmiss_1bjet->fill(eTmiss);
    _hist_pTj_1bjet->fill(recon_jets[0].pT());

    // 3JA region
    if (m_eff > 200 * GeV) {
      ++threeJA;
      _count_threeJA->fill(0.5);
    }

    // 3JB region
    if (m_eff > 700 * GeV) {
      ++threeJB;
      _count_threeJB->fill(0.5);
    }
  }

  // 2 bjets
  if (bjets.size() >= 2) {

    _hist_meff_2bjet->fill(m_eff);
    _hist_eTmiss_2bjet->fill(eTmiss);
    _hist_pTj_2bjet->fill(recon_jets[0].pT());

    // 3JC region
    if (m_eff > 500 * GeV) {
      ++threeJC;
      _count_threeJC->fill(0.5);
    }

    // 3JD region
    if (m_eff > 700 * GeV) {
      ++threeJD;
      _count_threeJD->fill(0.5);
    }
  }
}

/// @}


void finalize() {
  scale(_hist_meff_1bjet, 50. * 830. * crossSection() / picobarn / sumOfWeights());
  scale(_hist_eTmiss_1bjet, 100. * 830. * crossSection() / picobarn / sumOfWeights());
  scale(_hist_pTj_1bjet, 40. * 830. * crossSection() / picobarn / sumOfWeights());
  scale(_hist_meff_2bjet, 50. * 830. * crossSection() / picobarn / sumOfWeights());
  scale(_hist_eTmiss_2bjet, 100. * 830. * crossSection() / picobarn / sumOfWeights());
  scale(_hist_pTj_2bjet, 40. * 830. * crossSection() / picobarn / sumOfWeights());

  // cerr<< '\n'<<'\n'
  // << "Saw "
  // << bj << " events aft bjets cut, "
  // << jets << " events aft jet cuts, "
  // << eTmisscut << " events aft eTmiss cut, "
  // << zerolept << " events after 0-lept cut. "
  // << '\n'
  // << threeJA << " 3JA events, "
  // << threeJB << " 3JB events, "
  // << threeJC << " 3JC events, "
  // << threeJD << " 3JD events. "
  // << '\n'
  // ;
}

private:

/// @name Histograms
/// @{
Histo1DPtr _count_threeJA;
Histo1DPtr _count_threeJB;
Histo1DPtr _count_threeJC;
Histo1DPtr _count_threeJD;
Histo1DPtr _hist_meff_1bjet;
Histo1DPtr _hist_eTmiss_1bjet;
Histo1DPtr _hist_pTj_1bjet;
Histo1DPtr _hist_meff_2bjet;
Histo1DPtr _hist_eTmiss_2bjet;
Histo1DPtr _hist_pTj_2bjet;

/// @}


// debug variables
int threeJA;
int threeJB;
int threeJC;
int threeJD;
int bj;
int jets;
int zerolept;
int eTmisscut;

};

RIVET_DECLARE_PLUGIN(ATLAS_2011_CONF_2011_098);

} ```