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CMS_2016_PAS_SUS_16_14

Search for supersymmetry in events with jets and missing transverse momentum at 13 \text{TeV}
Experiment: CMS (LHC)
Status: VALIDATED
Authors:
  • Andy Buckley
No references listed
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • BSM physics signal events

A search for supersymmetry in all-hadronic events with large missing transverse momentum, produced in proton--proton collisions at $\sqrt{s} = 13 \text{TeV}$. The data sample, corresponding to an integrated luminosity of 12.9/fb, was collected with the CMS detector at the CERN LHC in 2016. The data are examined in search regions of jet multiplicity, tagged bottom quark jet multiplicity, missing transverse momentum, and the scalar sum of jet transverse momenta. The observed numbers of events in all search regions are found to be consistent with the expectations from Standard Model processes.

Source code: CMS_2016_PAS_SUS_16_14.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/PromptFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/Sphericity.hh"
#include "Rivet/Projections/SmearedParticles.hh"
#include "Rivet/Projections/SmearedJets.hh"
#include "Rivet/Projections/SmearedMET.hh"
#include "Rivet/Tools/Cutflow.hh"

namespace Rivet {


  /// @brief CMS 2016 0-lepton SUSY search, from 13/fb PAS note
  class CMS_2016_PAS_SUS_16_14 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(CMS_2016_PAS_SUS_16_14);


    /// @name Analysis methods
    //@{

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

      // Initialise and register projections
      FinalState calofs(Cuts::abseta < 5.0);
      FastJets fj(calofs, FastJets::ANTIKT, 0.4);
      declare(fj, "TruthJets");
      declare(SmearedJets(fj, JET_SMEAR_CMS_RUN2, [](const Jet& j) {
            if (j.abseta() > 2.5) return 0.;
            return j.bTagged() ? 0.55 : j.cTagged() ? 0.12 : 0.016; }), "Jets");

      FinalState es(Cuts::abspid == PID::ELECTRON && Cuts::abseta < 2.5);
      declare(es, "TruthElectrons");
      declare(SmearedParticles(es, ELECTRON_EFF_CMS_RUN2, ELECTRON_SMEAR_CMS_RUN2), "Electrons");

      FinalState mus(Cuts::abspid == PID::MUON && Cuts::abseta < 2.4);
      declare(mus, "TruthMuons");
      declare(SmearedParticles(mus, MUON_EFF_CMS_RUN2, MUON_SMEAR_CMS_RUN2), "Muons");

      FinalState isofs(Cuts::abseta < 3.0 && Cuts::abspid != PID::ELECTRON && Cuts::abspid != PID::MUON);
      declare(isofs, "IsoFS");
      FinalState cfs(Cuts::abseta < 2.5 && Cuts::abscharge != 0);
      declare(cfs, "TruthTracks");
      declare(SmearedParticles(cfs, TRK_EFF_CMS_RUN2), "Tracks");

      // Book histograms/counters
      _h_srcounts.resize(160);
      for (size_t ij = 0; ij < 4; ++ij) {
        for (size_t ib = 0; ib < 4; ++ib) {
          for (size_t ih = 0; ih < 10; ++ih) {
            const size_t i = 40*ij + 10*ib + ih;
            _h_srcounts[i] = bookCounter(toString(2*ij+3) + "j-" + toString(ib) + "b-" + toString(ih));
          }
        }
      }
      _h_srcountsagg.resize(12);
      for (size_t ia = 0; ia < 12; ++ia) {
        _h_srcountsagg[ia] = bookCounter("agg-" + toString(ia));
      }

    }


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

      // Get jets and require Nj >= 3
      const Jets jets24 = apply<JetAlg>(event, "Jets").jetsByPt(Cuts::pT > 30*GeV && Cuts::abseta < 2.4);
      if (jets24.size() < 3) vetoEvent;

      // HT cut
      vector<double> jetpts24; transform(jets24, jetpts24, pT);
      const double ht = sum(jetpts24, 0.0);
      if (ht < 300*GeV) vetoEvent;

      // HTmiss cut
      const Jets jets50 = apply<JetAlg>(event, "Jets").jetsByPt(Cuts::pT > 30*GeV && Cuts::abseta < 5.0);
      const FourMomentum htmissvec = -sum(jets24, mom, FourMomentum());
      const double htmiss = htmissvec.pT();
      if (htmissvec.pT() < 300*GeV) vetoEvent;


      // Get baseline electrons & muons
      Particles elecs = apply<ParticleFinder>(event, "Electrons").particles(Cuts::pT > 10*GeV);
      Particles muons = apply<ParticleFinder>(event, "Muons").particles(Cuts::pT > 10*GeV);

      // Electron/muon isolation
      const Particles calofs = apply<ParticleFinder>(event, "IsoFS").particles();
      ifilter_discard(elecs, [&](const Particle& e) {
          const double R = max(0.05, min(0.2, 10*GeV/e.pT()));
          double ptsum = -e.pT();
          for (const Particle& p : calofs)
            if (deltaR(p,e) < R) ptsum += p.pT();
          return ptsum / e.pT() > 0.1;
        });
      ifilter_discard(muons, [&](const Particle& m) {
          const double R = max(0.05, min(0.2, 10*GeV/m.pT()));
          double ptsum = -m.pT();
          for (const Particle& p : calofs)
            if (deltaR(p,m) < R) ptsum += p.pT();
          return ptsum / m.pT() > 0.2;
        });

      // Veto the event if there are any remaining baseline leptons
      if (!elecs.empty()) vetoEvent;
      if (!muons.empty()) vetoEvent;


      // Get isolated tracks
      Particles trks25 = apply<ParticleFinder>(event, "Tracks").particles();
      ifilter_discard(trks25, [&](const Particle& t) {
          double ptsum = -t.pT();
          for (const Particle& p : trks25)
            if (deltaR(p,t) < 0.3) ptsum += p.pT();
          return ptsum/t.pT() > ((t.abspid() == PID::ELECTRON || t.abspid() == PID::MUON) ? 0.2 : 0.1);
        });
      const Particles trks = filter_select(trks25, Cuts::abseta < 2.4);

      // Isolated track pT, pTmiss and mT cut
      // mT^2 = m1^2 + m2^2 + 2(ET1 ET2 - pT1 . pT2))
      // => mT0^2 = 2(ET1 |pT2| - pT1 . pT2)) for m1, m2 -> 0
      FourMomentum ptmissvec = htmissvec; ///< @todo Can we do better? No e,mu left...
      const double ptmiss = ptmissvec.pT();
      for (const Particle& t : trks) {
        const double ptcut = (t.abspid() == PID::ELECTRON || t.abspid() == PID::MUON) ? 5*GeV : 10*GeV;
        const double mT = sqrt( t.mass2() + 2*(t.Et()*ptmiss - t.pT()*ptmiss*cos(deltaPhi(t,ptmissvec))) );
        if (mT < 100*GeV && t.pT() < ptcut) vetoEvent;
      }

      // Lead jets isolation from Htmiss
      if (deltaPhi(htmissvec, jets24[0]) < 0.5) vetoEvent;
      if (deltaPhi(htmissvec, jets24[1]) < 0.5) vetoEvent;
      if (deltaPhi(htmissvec, jets24[2]) < 0.3) vetoEvent;
      if (jets24.size() >= 4 && deltaPhi(htmissvec, jets24[3]) < 0.3) vetoEvent;

      // Count jet and b-jet multiplicities
      const size_t nj = jets24.size();
      size_t nbj = 0;
      for (const Jet& j : jets24)
        if (j.bTagged()) nbj += 1;


      ////////


      // Fill the aggregate signal regions first
      if (nj >= 3 && nbj == 0 && ht >  500*GeV && htmiss > 500*GeV) _h_srcountsagg[ 0]->fill(event.weight());
      if (nj >= 3 && nbj == 0 && ht > 1500*GeV && htmiss > 750*GeV) _h_srcountsagg[ 1]->fill(event.weight());
      if (nj >= 5 && nbj == 0 && ht >  500*GeV && htmiss > 500*GeV) _h_srcountsagg[ 2]->fill(event.weight());
      if (nj >= 5 && nbj == 0 && ht > 1500*GeV && htmiss > 750*GeV) _h_srcountsagg[ 3]->fill(event.weight());
      if (nj >= 9 && nbj == 0 && ht > 1500*GeV && htmiss > 750*GeV) _h_srcountsagg[ 4]->fill(event.weight());
      if (nj >= 3 && nbj >= 2 && ht >  500*GeV && htmiss > 500*GeV) _h_srcountsagg[ 5]->fill(event.weight());
      if (nj >= 3 && nbj >= 1 && ht >  750*GeV && htmiss > 750*GeV) _h_srcountsagg[ 6]->fill(event.weight());
      if (nj >= 5 && nbj >= 3 && ht >  500*GeV && htmiss > 500*GeV) _h_srcountsagg[ 7]->fill(event.weight());
      if (nj >= 5 && nbj >= 2 && ht > 1500*GeV && htmiss > 750*GeV) _h_srcountsagg[ 8]->fill(event.weight());
      if (nj >= 9 && nbj >= 3 && ht >  750*GeV && htmiss > 750*GeV) _h_srcountsagg[ 9]->fill(event.weight());
      if (nj >= 7 && nbj >= 1 && ht >  300*GeV && htmiss > 300*GeV) _h_srcountsagg[10]->fill(event.weight());
      if (nj >= 5 && nbj >= 1 && ht >  750*GeV && htmiss > 750*GeV) _h_srcountsagg[11]->fill(event.weight());


      // Nj bin and Nbj bins
      static const vector<double> njedges = {3., 5., 7., 9.};
      const size_t inj = binIndex(nj, njedges, true);
      static const vector<double> njbedges = {0., 1., 2., 3.};
      const size_t inbj = binIndex(nbj, njbedges, true);
      // HTmiss vs HT 2D bin
      int iht = 0;
      if (htmiss < 350*GeV) {
        iht = ht < 500 ? 1 : ht < 1000 ? 2 : 3;
      } else if (htmiss < 500*GeV && ht > 350*GeV) {
        iht = ht < 500 ? 4 : ht < 1000 ? 5 : 6;
      } else if (htmiss < 750*GeV && ht > 500*GeV) {
        iht = ht < 1000 ? 7 : 8;
      } else if (ht > 750*GeV) {
        iht = ht < 1500 ? 9 : 10;
      }
      if (iht == 0) vetoEvent;
      iht -= 1; //< change from the paper's indexing scheme to C++ zero-indexed
      // Total bin number
      const size_t ibin = 40*inj + 10*inbj + (size_t)iht;

      // Fill SR counter
      _h_srcounts[ibin]->fill(event.weight());

    }


    /// Normalise counters after the run
    void finalize() {

      const double sf = 12.9*crossSection()/femtobarn/sumOfWeights();
      scale(_h_srcounts, sf);
      scale(_h_srcountsagg, sf);

    }

    //@}


  private:

    /// @name Histograms
    //@{
    vector<CounterPtr> _h_srcounts, _h_srcountsagg;
    //@}


  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CMS_2016_PAS_SUS_16_14);


}