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CMS_2012_I1111014

Shape, Transverse Size, and Charged Hadron Multiplicity of Jets in pp Collisions at $\sqrt{s}=7$ TeV
Experiment: CMS (LHC)
Inspire ID: 1111014
Status: VALIDATED
Authors:
  • Andreas Hinzmann
References:
  • hep-ex arXiv:1204.3170
  • inspirehep 1111014
  • http://cms-results.web.cern.ch/cms-results/public-results/publications/QCD-10-029/
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • pp QCD interactions at $\sqrt{s} = 7$ TeV. Data collected by CMS during the year 2010.

Measurements of jet characteristics from inclusive jet production in proton-proton collisions at a centre-of-mass energy of 7 TeV are presented. The data sample was collected with the CMS detector at the LHC during 2010 and corresponds to an integrated luminosity of 36 inverse picobarns. The mean charged hadron multiplicity, the differential and integral jet shape distributions, and two independent moments of the shape distributions are measured as functions of the jet transverse momentum for jets reconstructed with the anti-kT algorithm. The measured observables are corrected to the particle level and compared with predictions from various QCD Monte Carlo generators.

Source code: CMS_2012_I1111014.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/VisibleFinalState.hh"
#include "Rivet/Projections/JetShape.hh"

namespace Rivet {


  /// @brief CMS jet shape analysis
  /// @author Andreas Hinzmann
  class CMS_2012_I1111014 : public Analysis {
  public:

    /// Constructor
    CMS_2012_I1111014()
      : Analysis("CMS_2012_I1111014")
    {    }


    /// @name Analysis methods
    //@{

    void init() {
      // Set up projections
      const FinalState fs((Cuts::etaIn(-5.0, 5.0)));
      declare(fs, "FS");
      FastJets fj5(fs, FastJets::ANTIKT, 0.5);
      declare(fj5, "Jets5");
      FastJets fj7(fs, FastJets::ANTIKT, 0.7);
      declare(fj7, "Jets7");

      // Specify pT bins
      _ptedges = {{ 20.,25.,30.,40.,50.,60.,70.,80.,90.,100.,110.,125.,140.,160.,180.,200.,225.,250.,300.,400.,500.,600.,1000. }};
      _yedges  = {{ 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 }};

      // Register a jet shape projection and histogram for each pT bin
      unsigned int histo_counter=1;
      for (size_t j = 0; j < 6; ++j) {
        for (size_t i = 0; i < 22; ++i) {
          if (i > 20 && j == 3) continue;
          if (i > 18 && j >= 4) continue;

          // Set up projections for each (pT,y) bin
          _jsnames_pT[i][j] = "JetShape" + to_str(i) + "_" + to_str(j);
          const JetShape jsp(fj7, 0.0, 0.7, 7, _ptedges[i], _ptedges[i+1], _yedges[j], _yedges[j+1], RAPIDITY);
          declare(jsp, _jsnames_pT[i][j]);

          // Book profile histograms for each (pT,y) bin
          book(_profhistRho_pT[i][j], histo_counter, 1, 1);
          histo_counter+=1;
        }
      }
      book(_profhistNch[0], 126, 1, 1);
      book(_profhistNch[1], 126, 1, 2);
      book(_profhistDr[0], 127, 1, 1);
      book(_profhistDr[1], 127, 1, 2);
      book(_profhistDeta, "TMP/Deta", refData(127,1,1));
      book(_profhistDphi, "TMP/Dphi", refData(127,1,1));
      book(_profhistAsym, "d128-x01-y01", true);

    }



    /// Do the analysis
    void analyze(const Event& evt) {

      // Get jets and require at least one to pass pT and y cuts
      Jets jets7 = apply<FastJets>(evt, "Jets7")
        .jetsByPt(Cuts::ptIn(_ptedges.front()*GeV, _ptedges.back()*GeV) && Cuts::absrap < 3.0);
      if(jets7.size()>2) jets7.resize(2); // Use only the first two jets
      MSG_DEBUG("Jet (R=0.7) multiplicity before cuts = " << jets7.size());
      if (jets7.size() == 0) {
        MSG_DEBUG("No jets (R=0.7) found in required pT and rapidity range");
        vetoEvent;
      }
      // Calculate and histogram jet shapes
      for (size_t jy = 0; jy < 6; ++jy) {
        for (size_t ipt = 0; ipt < 22; ++ipt) {
          if (ipt > 20 && jy == 3) continue;
          if (ipt > 18 && jy >= 4) continue;
          JetShape jsipt = apply<JetShape>(evt, _jsnames_pT[ipt][jy]);
          jsipt.calc(jets7);
          for (size_t ijet = 0; ijet < jsipt.numJets(); ++ijet) {
            for (size_t rbin = 0; rbin < jsipt.numBins(); ++rbin) {
              const double r_rho = jsipt.rBinMid(rbin);
              _profhistRho_pT[ipt][jy]->fill(r_rho, (1./0.1)*jsipt.diffJetShape(ijet, rbin));
            }
          }
        }
      }
      
      // Get jets and require at least one to pass pT and y cuts
      Jets jets5 = apply<FastJets>(evt, "Jets5")
        .jetsByPt(Cuts::ptIn(50*GeV, 1000*GeV) && Cuts::absrap < 2.0);
      // Calculate and histogram charged jet shapes
      for (const Jet& jet : jets5) {
        double ncharge = 0;
        double eta=0;
        double phi=0;
        double sumpt=0;
        for (const Particle& p : jet.particles()) {
          if ((p.pT() < 0.5) || (p.charge3()==0) || (abs(p.pid())==11) || (abs(p.pid())==13)) continue;
          ncharge++;
          sumpt+=p.pT();
          eta+=p.pT()*p.eta();
          phi+=p.pT()*mapAngleMPiToPi(p.phi()-jet.phi());
        }
        if (jet.absrap()<1.0) {
          _profhistNch[0]->fill(jet.pT(), ncharge );
        } else if (jet.absrap()<2.0) {
          _profhistNch[1]->fill(jet.pT(), ncharge );
        }
        if (sumpt==0) continue;
        eta/=sumpt;
        phi/=sumpt;
        double deta=0;
        double dphi=0;
        for (const Particle& p : jet.particles()) {
          if ((p.pT() < 0.5) || (p.charge3()==0) || (abs(p.pid())==11) || (abs(p.pid())==13)) continue;
          deta+=p.pT()*pow(p.eta()-eta,2);
          dphi+=p.pT()*pow(mapAngleMPiToPi(p.phi()-phi-jet.phi()),2);
        }
        deta/=sumpt;
        dphi/=sumpt;
        if ((dphi==0)||(deta==0)) continue;
        if (jet.absrap()<1.0) {
          _profhistDr[0]->fill(jet.pT(), deta+dphi );
          _profhistDeta->fill(jet.pT(), deta );
          _profhistDphi->fill(jet.pT(), dphi );
        } else if (jet.absrap()<2.0) {
          _profhistDr[1]->fill(jet.pT(), deta+dphi );
        }
      }
    }


    // Finalize
    void finalize() {
      for (unsigned int i = 0; i < _profhistAsym->numPoints(); ++i) {
        if((_profhistDeta->bin(i).effNumEntries()<2)||(_profhistDphi->bin(i).effNumEntries()<2)) continue;
        if((_profhistDeta->bin(i).mean()==0)||(_profhistDphi->bin(i).mean()==0)) continue;
        double mean_ratio=_profhistDeta->bin(i).mean() / _profhistDphi->bin(i).mean();
        double mean_error=mean_ratio*sqrt(pow(_profhistDeta->bin(i).stdErr()/_profhistDeta->bin(i).mean(),2)+pow(_profhistDphi->bin(i).stdErr()/_profhistDphi->bin(i).mean(),2));
        _profhistAsym->point(i).setY(mean_ratio,mean_error);
      }
    }

    //@}


  private:

    /// @name Analysis data
    //@{

    /// Jet \f$ p_\perp\f$ bins.
    vector<double> _ptedges; // This can't be a raw array if we want to initialise it non-painfully
    vector<double> _yedges;

    /// JetShape projection name for each \f$p_\perp\f$ bin.
    string _jsnames_pT[22][6];

    //@}

    /// @name Histograms
    //@{
    Profile1DPtr _profhistRho_pT[22][6];
    Profile1DPtr _profhistNch[2];
    Profile1DPtr _profhistDr[2];
    Profile1DPtr _profhistDeta;
    Profile1DPtr _profhistDphi;
    Scatter2DPtr _profhistAsym;
    //@}

  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CMS_2012_I1111014);

}