Rivet analyses

title: ATLAS_2012_I943401

Search for supersymmetry with 2 leptons and missing transverse energy

Experiment: ATLAS (LHC)

Inspire ID: 943401

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 1110.6189

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - BSM signal events at 7000 GeV.

Results of three searches for the production of supersymmetric particles decaying into final states with missing transverse momentum and exactly two isolated leptons, electrons or muons. The analysis uses a data sample collected during the first half of 2011 that corresponds to a total integrated luminosity of 1 $\text{fb}^{-1}$ of $\sqrt{s} = 7$\,TeV proton-proton collisions recorded with the ATLAS detector at the Large Hadron Collider. Opposite-sign and same-sign dilepton events are studied separately. Additionally, in opposite- sign events, a search is made for an excess of same-flavour over different-flavour lepton pairs.

Source code:ATLAS_2012_I943401.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"

include "Rivet/Tools/Random.hh"

namespace Rivet {

class ATLAS_2012_I943401 : public Analysis { public:

/// @name Constructors etc.
/// @{

/// Constructor

RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2012_I943401);

/// @}

public:

/// @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
  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 < 4.5), "vfs");

  // book histograms

  // counts in signal regions
  book(_count_OS_SR1, "count_OS_SR1", 1, 0., 1.);
  book(_count_OS_SR2, "count_OS_SR2", 1, 0., 1.);
  book(_count_OS_SR3, "count_OS_SR3", 1, 0., 1.);
  book(_count_SS_SR1, "count_SS_SR1", 1, 0., 1.);
  book(_count_SS_SR2, "count_SS_SR2", 1, 0., 1.);
  book(_count_FS_SR1, "count_FS_SR1", 1, 0., 1.);
  book(_count_FS_SR2, "count_FS_SR2", 1, 0., 1.);
  book(_count_FS_SR3, "count_FS_SR3", 1, 0., 1.);

  // histograms from paper

  book(_hist_mll_SS_D, 1, 1, 1);
  book(_hist_mll_SS_B, 1, 1, 2);
  book(_hist_eTmiss_SS_D, 2, 1, 1);
  book(_hist_eTmiss_SS_B, 2, 1, 2);
  book(_hist_mll_SS_2Jet_D, 3, 1, 1);
  book(_hist_mll_SS_2Jet_B, 3, 1, 2);
  book(_hist_njet_SS_D, 5, 1, 1);
  book(_hist_njet_SS_B, 5, 1, 2);
  book(_hist_pT_j1_SS_D, 6, 1, 1);
  book(_hist_pT_j1_SS_B, 6, 1, 2);
  book(_hist_pT_j2_SS_D, 7, 1, 1);
  book(_hist_pT_j2_SS_B, 7, 1, 2);
  book(_hist_pT_l1_SS_D, 8, 1, 1);
  book(_hist_pT_l1_SS_B, 8, 1, 2);
  book(_hist_pT_l2_SS_D, 9, 1, 1);
  book(_hist_pT_l2_SS_B, 9, 1, 2);
  book(_hist_mll_OS_D, 10, 1, 1);
  book(_hist_mll_OS_B, 10, 1, 2);
  book(_hist_eTmiss_OS_D, 11, 1, 1);
  book(_hist_eTmiss_OS_B, 11, 1, 2);
  book(_hist_eTmiss_3Jet_OS_D, 12, 1, 1);
  book(_hist_eTmiss_3Jet_OS_B, 12, 1, 2);
  book(_hist_eTmiss_4Jet_OS_D, 13, 1, 1);
  book(_hist_eTmiss_4Jet_OS_B, 13, 1, 2);
  book(_hist_njet_OS_D, 14, 1, 1);
  book(_hist_njet_OS_B, 14, 1, 2);
  book(_hist_pT_j1_OS_D, 15, 1, 1);
  book(_hist_pT_j1_OS_B, 15, 1, 2);
  book(_hist_pT_j2_OS_D, 16, 1, 1);
  book(_hist_pT_j2_OS_B, 16, 1, 2);
  book(_hist_pT_l1_OS_D, 17, 1, 1);
  book(_hist_pT_l1_OS_B, 17, 1, 2);
  book(_hist_pT_l2_OS_D, 18, 1, 1);
  book(_hist_pT_l2_OS_B, 18, 1, 2);
  //????
  //   <dataPointSet name="d04-x01-y01" dimension="2" path="/REF/ATLAS_2011_I943401" title="EVENTS/10 GEV" >
  //   <dataPointSet name="d04-x01-y02" dimension="2" path="/REF/ATLAS_2011_I943401" title="EVENTS/10 GEV" >
}

/// Perform the event analysis
void analyze(const Event& event) {
  // get the jet candidates
  Jets cand_jets = apply<FastJets>(event, "AntiKtJets04")
                       .jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 2.8);

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

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

  // Reconstructed electrons
  Particles recon_e;
  for (const Particle& e : cand_e) {
    // check not near a jet
    bool e_near_jet = false;
    for (const Jet& jet : recon_jets) {
      if (deltaR(e.momentum(), jet.momentum()) < 0.4) {
        e_near_jet = true;
        break;
      }
    }
    if (e_near_jet) continue;
    // check the isolation
    double pTinCone = -e.pT();
    for (const Particle& track : chg_tracks) {
      if (deltaR(e.momentum(), track.momentum()) < 0.2) pTinCone += track.pT();
    }
    if (pTinCone < 0.1 * e.perp()) recon_e.push_back(e);
  }

  // Reconstructed Muons
  Particles recon_mu;
  Particles cand_mu = apply<IdentifiedFinalState>(event, "muons").particlesByPt();
  for (const Particle& mu : cand_mu) {
    // check not near a jet
    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) continue;
    // isolation
    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) 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();

  // ATLAS calo problem
  if (rand01() <= 0.42) {
    for (const Particle& e : recon_e) {
      double eta = e.eta();
      double phi = e.azimuthalAngle(MINUSPI_PLUSPI);
      if (inRange(eta, -0.1, 1.5) && inRange(phi, -0.9, -0.5)) vetoEvent;
    }
    for (const Jet& jet : recon_jets) {
      double eta = jet.rapidity();
      double phi = jet.azimuthalAngle(MINUSPI_PLUSPI);
      if (jet.pT() > 40 * GeV && inRange(eta, -0.1, 1.5) && inRange(phi, -0.9, -0.5)) vetoEvent;
    }
  }

  // Exactly two leptons for each event
  if (recon_mu.size() + recon_e.size() != 2) vetoEvent;
  // two electrons highest pT > 25
  Particles recon_leptons;
  if (recon_e.size() == 2 && recon_e[0].pT() > 25 * GeV) {
    recon_leptons = recon_e;
  }
  // two muons highest pT > 20
  else if (recon_mu.size() == 2 && recon_mu[0].pT() > 20 * GeV) {
    recon_leptons = recon_mu;
  }
  else if (recon_e.size() == 1 && recon_mu.size() == 1
           && (recon_e[0].pT() > 25 * GeV || recon_mu[0].pT() > 20 * GeV)) {
    if (recon_mu[0].pT() < recon_e[0].pT()) {
      recon_leptons.push_back(recon_e[0]);
      recon_leptons.push_back(recon_mu[0]);
    }
    else {
      recon_leptons.push_back(recon_mu[0]);
      recon_leptons.push_back(recon_e[0]);
    }
  }
  // fails trigger
  else
    vetoEvent;

  double mll = (recon_leptons[0].momentum() + recon_leptons[1].momentum()).mass();
  // lepton pair mass > 12.
  if (mll < 12 * GeV) vetoEvent;

  // same sign or opposite sign event
  int sign = recon_leptons[0].pid() * recon_leptons[1].pid();

  // same sign leptons
  if (sign > 0) {
    _hist_mll_SS_D->fill(mll);
    _hist_mll_SS_B->fill(mll);
    _hist_eTmiss_SS_D->fill(eTmiss);
    _hist_eTmiss_SS_B->fill(eTmiss);
    if (recon_jets.size() >= 2) {
      _hist_mll_SS_2Jet_D->fill(mll);
      _hist_mll_SS_2Jet_B->fill(mll);
    }
    _hist_njet_SS_D->fill(recon_jets.size());
    _hist_njet_SS_B->fill(recon_jets.size());
    if (!recon_jets.empty()) {
      _hist_pT_j1_SS_D->fill(recon_jets[0].perp());
      _hist_pT_j1_SS_B->fill(recon_jets[0].perp());
    }
    if (recon_jets.size() > 2) {
      _hist_pT_j2_SS_D->fill(recon_jets[1].perp());
      _hist_pT_j2_SS_B->fill(recon_jets[1].perp());
    }
    _hist_pT_l1_SS_D->fill(recon_leptons[0].perp());
    _hist_pT_l1_SS_B->fill(recon_leptons[0].perp());
    _hist_pT_l2_SS_D->fill(recon_leptons[1].perp());
    _hist_pT_l2_SS_B->fill(recon_leptons[1].perp());
    // SS-SR1
    if (eTmiss > 100.) {
      _count_SS_SR1->fill(0.5);
    }
    // SS-SR2
    if (eTmiss > 80. && recon_jets.size() >= 2 && recon_jets[1].perp() > 50.) {
      _count_SS_SR2->fill(0.5);
    }
  }
  // opposite sign
  else {
    _hist_mll_OS_D->fill(mll);
    _hist_mll_OS_B->fill(mll);
    _hist_eTmiss_OS_D->fill(eTmiss);
    _hist_eTmiss_OS_B->fill(eTmiss);
    if (recon_jets.size() >= 3) {
      _hist_eTmiss_3Jet_OS_D->fill(eTmiss);
      _hist_eTmiss_3Jet_OS_B->fill(eTmiss);
    }
    if (recon_jets.size() >= 4) {
      _hist_eTmiss_4Jet_OS_D->fill(eTmiss);
      _hist_eTmiss_4Jet_OS_B->fill(eTmiss);
    }
    _hist_njet_OS_D->fill(recon_jets.size());
    _hist_njet_OS_B->fill(recon_jets.size());
    if (!recon_jets.empty()) {
      _hist_pT_j1_OS_D->fill(recon_jets[0].perp());
      _hist_pT_j1_OS_B->fill(recon_jets[0].perp());
    }
    if (recon_jets.size() > 2) {
      _hist_pT_j2_OS_D->fill(recon_jets[1].perp());
      _hist_pT_j2_OS_B->fill(recon_jets[1].perp());
    }
    _hist_pT_l1_OS_D->fill(recon_leptons[0].perp());
    _hist_pT_l1_OS_B->fill(recon_leptons[0].perp());
    _hist_pT_l2_OS_D->fill(recon_leptons[1].perp());
    _hist_pT_l2_OS_B->fill(recon_leptons[1].perp());
    // different signal regions
    // OS-SR1
    if (eTmiss > 250.) {
      _count_OS_SR1->fill(0.5);
    }
    // OS-SR2
    if (eTmiss > 220. && recon_jets.size() >= 3 && recon_jets[0].perp() > 80.
        && recon_jets[2].perp() > 40.) {
      _count_OS_SR2->fill(0.5);
    }
    // OS-SR3
    if (eTmiss > 100. && recon_jets.size() >= 4 && recon_jets[0].perp() > 100.
        && recon_jets[3].perp() > 70.) {
      _count_OS_SR3->fill(0.5);
    }
    // same flavour analysis
    static const double beta = 0.75;
    static const double tau_e = 0.96;
    static const double tau_mu = 0.816;
    double fs_weight = 1.0;
    if (recon_leptons[0].abspid() == PID::ELECTRON && recon_leptons[1].abspid() == PID::ELECTRON) {
      fs_weight /= beta * (1. - sqr(1. - tau_e));
    }
    else if (recon_leptons[0].abspid() == PID::MUON && recon_leptons[1].abspid() == PID::MUON) {
      fs_weight *= beta / (1. - sqr(1. - tau_mu));
    }
    else {
      fs_weight /= -(1. - (1. - tau_e) * (1. - tau_mu));
    }
    // FS-SR1
    if (eTmiss > 80. && (mll < 80. || mll > 100.)) {
      _count_FS_SR1->fill(0.5, fs_weight);
    }
    // FS-SR2
    if (eTmiss > 80. && recon_jets.size() >= 2) {
      _count_FS_SR2->fill(0.5, fs_weight);
    }
    // FS-SR3
    if (eTmiss > 250.) {
      _count_FS_SR3->fill(0.5, fs_weight);
    }
  }
}

/// @}


void finalize() {

  double norm = crossSection() / femtobarn * 1.04 / sumOfWeights();
  // event counts
  scale(_count_OS_SR1, norm);
  scale(_count_OS_SR2, norm);
  scale(_count_OS_SR3, norm);
  scale(_count_SS_SR1, norm);
  scale(_count_SS_SR2, norm);
  scale(_count_FS_SR1, norm);
  scale(_count_FS_SR2, norm);
  scale(_count_FS_SR3, norm);
  // histograms
  scale(_hist_mll_SS_D, norm * 20.);
  scale(_hist_mll_SS_B, norm * 20.);
  scale(_hist_eTmiss_SS_D, norm * 20.);
  scale(_hist_eTmiss_SS_B, norm * 20.);
  scale(_hist_mll_SS_2Jet_D, norm * 50.);
  scale(_hist_mll_SS_2Jet_B, norm * 50.);
  scale(_hist_njet_SS_D, norm);
  scale(_hist_njet_SS_B, norm);
  scale(_hist_pT_j1_SS_D, norm * 20.);
  scale(_hist_pT_j1_SS_B, norm * 20.);
  scale(_hist_pT_j2_SS_D, norm * 20.);
  scale(_hist_pT_j2_SS_B, norm * 20.);
  scale(_hist_pT_l1_SS_D, norm * 5.);
  scale(_hist_pT_l1_SS_B, norm * 5.);
  scale(_hist_pT_l2_SS_D, norm * 5.);
  scale(_hist_pT_l2_SS_B, norm * 5.);

  scale(_hist_mll_OS_D, norm * 10.);
  scale(_hist_mll_OS_B, norm * 10.);
  scale(_hist_eTmiss_OS_D, norm * 10.);
  scale(_hist_eTmiss_OS_B, norm * 10.);
  scale(_hist_eTmiss_3Jet_OS_D, norm * 10.);
  scale(_hist_eTmiss_3Jet_OS_B, norm * 10.);
  scale(_hist_eTmiss_4Jet_OS_D, norm * 10.);
  scale(_hist_eTmiss_4Jet_OS_B, norm * 10.);
  scale(_hist_njet_OS_D, norm);
  scale(_hist_njet_OS_B, norm);
  scale(_hist_pT_j1_OS_D, norm * 20.);
  scale(_hist_pT_j1_OS_B, norm * 20.);
  scale(_hist_pT_j2_OS_D, norm * 20.);
  scale(_hist_pT_j2_OS_B, norm * 20.);
  scale(_hist_pT_l1_OS_D, norm * 20.);
  scale(_hist_pT_l1_OS_B, norm * 20.);
  scale(_hist_pT_l2_OS_D, norm * 20.);
  scale(_hist_pT_l2_OS_B, norm * 20.);
}

private:

/// @name Histograms
/// @{
Histo1DPtr _count_OS_SR1;
Histo1DPtr _count_OS_SR2;
Histo1DPtr _count_OS_SR3;
Histo1DPtr _count_SS_SR1;
Histo1DPtr _count_SS_SR2;
Histo1DPtr _count_FS_SR1;
Histo1DPtr _count_FS_SR2;
Histo1DPtr _count_FS_SR3;

Histo1DPtr _hist_mll_SS_D;
Histo1DPtr _hist_mll_SS_B;
Histo1DPtr _hist_eTmiss_SS_D;
Histo1DPtr _hist_eTmiss_SS_B;
Histo1DPtr _hist_mll_SS_2Jet_D;
Histo1DPtr _hist_mll_SS_2Jet_B;
Histo1DPtr _hist_njet_SS_D;
Histo1DPtr _hist_njet_SS_B;
Histo1DPtr _hist_pT_j1_SS_D;
Histo1DPtr _hist_pT_j1_SS_B;
Histo1DPtr _hist_pT_j2_SS_D;
Histo1DPtr _hist_pT_j2_SS_B;
Histo1DPtr _hist_pT_l1_SS_D;
Histo1DPtr _hist_pT_l1_SS_B;
Histo1DPtr _hist_pT_l2_SS_D;
Histo1DPtr _hist_pT_l2_SS_B;

Histo1DPtr _hist_mll_OS_D;
Histo1DPtr _hist_mll_OS_B;
Histo1DPtr _hist_eTmiss_OS_D;
Histo1DPtr _hist_eTmiss_OS_B;
Histo1DPtr _hist_eTmiss_3Jet_OS_D;
Histo1DPtr _hist_eTmiss_3Jet_OS_B;
Histo1DPtr _hist_eTmiss_4Jet_OS_D;
Histo1DPtr _hist_eTmiss_4Jet_OS_B;
Histo1DPtr _hist_njet_OS_D;
Histo1DPtr _hist_njet_OS_B;
Histo1DPtr _hist_pT_j1_OS_D;
Histo1DPtr _hist_pT_j1_OS_B;
Histo1DPtr _hist_pT_j2_OS_D;
Histo1DPtr _hist_pT_j2_OS_B;
Histo1DPtr _hist_pT_l1_OS_D;
Histo1DPtr _hist_pT_l1_OS_B;
Histo1DPtr _hist_pT_l2_OS_D;
Histo1DPtr _hist_pT_l2_OS_B;
/// @}

};

RIVET_DECLARE_PLUGIN(ATLAS_2012_I943401);

} ```