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ATLAS_2016_I1492320

WWW production at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1492320
Status: VALIDATED
Authors:
  • Alex Long
  • Ismet Siral
  • Louis Helary
  • Christian Gutschow
References: Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
Run details:
  • pp -> WWW production at 8 TeV

This paper reports a search for triboson $W^\pm W^\pm W^\mp$ production in two decay channels ($W^\pm W^\pm W^\mp \to \ell^\pm\nu \ell^\pm\nu \ell^\mp\nu$) and ($W^\pm W^\pm W^\mp \to \ell^\pm\nu \ell^\pm\nu jj$ with $\ell = e,\mu$) in proton-proton collision data corresponding to an integrated luminosity of 20.3 fb${}^{-1}$ at a centre-of-mass energy of 8 TeV with the ATLAS detector at the Large Hadron Collider. Events with exactly three charged leptons, or two leptons with the same electric charge in association with two jets, are selected. The total number of events observed in data is consistent with the Standard Model (SM) predictions. The observed 95 % confidence level upper limit on the SM $W^\pm W^\pm W^\mp$ production cross section is found to be 730 fb with an expected limit of 560 fb in the absence of SM $W^\pm W^\pm W^\mp$ production. Limits are also set on $WWWW$ anomalous quartic gauge couplings. Default will make both plots. Use options 2L2J or 3J to make just one.

Source code: ATLAS_2016_I1492320.cc
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// -*- C++ -*
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/MissingMomentum.hh"
#include "Rivet/Projections/DressedLeptons.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/HeavyHadrons.hh"

namespace Rivet {


  /// @brief WWW cross-section at 8 TeV, 3L mode
  class ATLAS_2016_I1492320 : public Analysis {
  public:

    // Default constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(ATLAS_2016_I1492320);

    /// @name Analysis methods
    //@{

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

      // Get options from the new option system
      _mode = 0;
      if ( getOption("LMODE") == "3L" ) _mode = 1;
      if ( getOption("LMODE") == "2L2J" ) _mode = 2;


      // Charged leptons within acceptance
      const PromptFinalState chLep_fid = PromptFinalState(Cuts::abspid == PID::ELECTRON || Cuts::abspid == PID::MUON);
      const PromptFinalState photon_fs = PromptFinalState(Cuts::abspid == PID::PHOTON);
      const DressedLeptons dressed_leps(photon_fs, chLep_fid, 0.1, Cuts::pT > 20*GeV && Cuts::abseta < 2.5);
      declare(dressed_leps, "DressedLeptons");

      const DressedLeptons dressed_leps2(photon_fs, chLep_fid, 0.1, Cuts::pT > 10*GeV);
      declare(dressed_leps2, "DressedLeptons2");


      // Jets, anti-kt 0.4
      VetoedFinalState fsJets(FinalState(Cuts::abseta < 7.0)); //final state for jet finding: veto leptons and neutrinos
      fsJets.vetoNeutrinos();
      fsJets.addVetoOnThisFinalState(photon_fs);
      fsJets.addVetoOnThisFinalState(chLep_fid);
      declare(FastJets(fsJets, FastJets::ANTIKT, 0.4), "Jets");

      // b hadrons for b-tagging
      declare(HeavyHadrons(Cuts::abseta < 2.5 && Cuts::pT > 5*GeV), "Bhadrons");

      // Missing momentum
      declare(MissingMomentum(), "MET");

      // Histograms
      if (_mode != 2){
	_h_fiducial_3l = bookCounter("d01-x01-y01");
      }
      if (_mode != 1){
	_h_2l2j = bookCounter("d01-x01-y02");
      }
    }


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

      // Get the dressed leptons, sorted by pT of their constituent bare lepton (!!)
      vector<DressedLepton> _vbs_lep = apply<DressedLeptons>(event, "DressedLeptons").dressedLeptons();
      if (_vbs_lep.size() == 3 && _mode != 2) {
	std::sort(_vbs_lep.begin(), _vbs_lep.end(), [](const DressedLepton& l1, const DressedLepton& l2) {
	    return (l1.constituentLepton().pT() > l2.constituentLepton().pT());
	  });

	// Get the jets
	const Jets& _vbs_jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 25*GeV && Cuts::abseta < 4.5);
	if (_vbs_jets.size() <= 1) {

	  // Determine nsfos pairs for channel classification
	  int nSFOS = 0;
	  for (size_t i = 0; i < _vbs_lep.size(); ++i) {
	    const double ch_l0 = _vbs_lep[i].charge();
	    for (size_t j = i + 1; j < _vbs_lep.size(); ++j) {
	      const double ch_l1 = _vbs_lep[j].charge();
	      if (_vbs_lep[i].abspid() == _vbs_lep[j].abspid() && ch_l0*ch_l1 < 0) ++nSFOS;
	    }
	  }

	  double minDRll = DBL_MAX, mSFOS_MinDiff = DBL_MAX, meeSS_MinDiff = DBL_MAX, mSF_min = DBL_MAX;
	  for (size_t i = 0; i < _vbs_lep.size(); ++i) {
	    const double ch_l0 = _vbs_lep[i].charge();
	    for (size_t j = i + 1; j < _vbs_lep.size(); ++j) {
	      const double ch_l1 = _vbs_lep[j].charge();
	      const bool samesign = ch_l0*ch_l1 > 0;

	      // Update min dR between leptons
	      minDRll = min(minDRll, deltaR(_vbs_lep[i], _vbs_lep[j]));

	      // Require same flavour
	      if (_vbs_lep[i].abspid() != _vbs_lep[j].abspid()) continue;

	      // SF dilepton mass (used several times)
	      const double mSF = (_vbs_lep[i].momentum() + _vbs_lep[j].momentum()).mass();

	      // Determine min for all same-flavor pairs
	      mSF_min = min(mSF, mSF_min);

	      // Determine min for all m_ee same-sign pairs
	      if (_vbs_lep[i].abspid() == PID::ELECTRON && samesign) {
		if (fabs(mSF-ZMASS) < fabs(meeSS_MinDiff-ZMASS)) meeSS_MinDiff = mSF;
	      }

	      // Determine min for all mSFOS pairs
	      if (!samesign && fabs(mSF-ZMASS) < abs(mSFOS_MinDiff-ZMASS)) mSFOS_MinDiff = mSF;
	    }
	  }

	  bool setVeto = false;
	  if (minDRll < 0.1) setVeto = true;
	  if (nSFOS == 0 && mSF_min < 20*GeV) setVeto = true;
	  if (nSFOS == 0 && fabs(meeSS_MinDiff - ZMASS) < 15*GeV) setVeto = true;
	  if (nSFOS == 1 && ((ZMASS - mSFOS_MinDiff) < 35*GeV && (mSFOS_MinDiff - ZMASS) < 20*GeV)) setVeto = true;
	  if (nSFOS == 2 && fabs(mSFOS_MinDiff - ZMASS) < 20*GeV) setVeto = true;

	  if (!setVeto) {
	    const Vector3& met = -1.0 * apply<MissingMomentum>(event, "MET").vectorEt();
	    if (nSFOS == 1 && met.mod() < 45*GeV) setVeto = true;
	    if (nSFOS == 2 && met.mod() < 55*GeV) setVeto = true;

	    if (!setVeto) {
	      const double dPhi = deltaPhi((_vbs_lep[0].momentum() + _vbs_lep[1].momentum() + _vbs_lep[2].momentum()), met);
	      if (dPhi < 2.5) setVeto = true;
	    }
	    // Fill histo
	    if (!setVeto) {
	      _h_fiducial_3l->fill(event.weight());
	    }
	  }
	}
      }

      if (_mode != 1){
	// Get leptons
	vector<DressedLepton> leps = apply<DressedLeptons>(event, "DressedLeptons").dressedLeptons();
	if (leps.size() >= 2) {
	  // Sort the dressed leptons by pt of their constituent lepton (bare lepton pt)
	  std::sort(leps.begin(), leps.end() ,
		    [](const DressedLepton& l1, const DressedLepton& l2) {
		      return (l1.constituentLepton().pT() > l2.constituentLepton().pT()); });
	  if (leps[0].pT() < 30*GeV || leps[0].abseta() > 2.5)  vetoEvent;
	  if (leps[1].pT() < 30*GeV || leps[1].abseta() > 2.5)  vetoEvent;

	  // Get jets
	  const Jets& jets = apply<FastJets>(event, "Jets").jetsByPt(Cuts::pT > 15*GeV);

	  // Find min dilepton DR and mass
	  double minDRll = DBL_MAX, mll = DBL_MAX;
	  for (size_t i = 0; i < leps.size(); ++i) {
	    for (size_t j = i + 1; j < leps.size(); ++j) {
	      minDRll = min(minDRll, deltaR(leps[i], leps[j]));
	      mll = min(mll, (leps[i].momentum() + leps[j].momentum()).mass());
	    }
	  }
	  if (minDRll < 0.1) vetoEvent;
	  if (mll < 40*GeV) vetoEvent;

	  // Require same-sign leading leptons
	  if (leps[0].charge()*leps[0].charge() < 0) vetoEvent;

	  // Veto di-electron combinations within 10 GeV of the Z mass
	  if (fabs(mll - 91.188*GeV) < 10*GeV && leps[0].abspid() == PID::ELECTRON && leps[1].abspid() == PID::ELECTRON) vetoEvent;

	  // Now jet cuts
	  if (jets.size() < 2) vetoEvent;
	  if (jets[0].pT() < 30*GeV || jets[0].abseta() > 2.5) vetoEvent;
	  if (jets[1].pT() < 20*GeV || jets[1].abseta() > 2.5) vetoEvent;

	  // Find closest jet/lepton pair and veto if too close in phi or too far in eta
	  double minDRLepJets = DBL_MAX;
	  for (const Jet& jet : jets) {
	    for (const Particle& lep : leps) minDRLepJets = min(minDRLepJets, deltaR(lep, jet));
	  }
	  if (minDRLepJets < 0.3) vetoEvent;
	  if (fabs(deltaEta(jets[0], jets[1])) > 1.5) vetoEvent;

	  // Dijet mass requirement
	  double mjj = (jets[0].momentum() + jets[1].momentum()).mass();
	  if (mjj < 65 || mjj > 105)  vetoEvent;
	  if (!inRange(mjj, 65*GeV, 105*GeV)) vetoEvent;

	  // Veto if any good jets are b-jets
	  const Particles& bhadrons = apply<HeavyHadrons>(event, "Bhadrons").bHadrons();
	  for (const Jet& j : jets) {
	    if (j.abseta() > 2.5) continue; // outside acceptance of b-tagging
	    const bool isbJet = any(bhadrons, deltaRLess(j, 0.3));
	    if (isbJet) vetoEvent;
	  }

	  // MET vetoing for non-muon events
	  const MissingMomentum& met = apply<MissingMomentum>(event, "MET");
	  if (met.vectorEt().mod() < 55*GeV && (leps[0].abspid() != PID::MUON || leps[1].abspid() != PID::MUON)) vetoEvent;

	  // Fill counter
	  _h_2l2j->fill(event.weight());
	}
      }
    }



    /// Normalise histograms etc., after the run
    void finalize() {
      if (_mode != 2){
	scale(_h_fiducial_3l, crossSection()/sumOfWeights()/femtobarn);
      }
      if (_mode != 1){
	scale(_h_2l2j, crossSection()/sumOfWeights()/femtobarn);
      }
    }

    //@}

  protected:

    size_t _mode;


  private:

    /// @name Histograms
    //@{
    const double ZMASS = 91.1876*GeV;
    CounterPtr _h_fiducial_3l;
    CounterPtr _h_2l2j;
    //@}

  };


  // Hook for the plugin system
  DECLARE_RIVET_PLUGIN(ATLAS_2016_I1492320);

}