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CDF_2001_S4751469

Field \& Stuart Run I underlying event analysis.
Experiment: CDF (Tevatron Run 1)
Inspire ID: 564673
Status: VALIDATED
Authors:
  • Andy Buckley
References:
  • Phys.Rev.D65:092002,2002
  • FNAL-PUB 01/211-E
Beams: p- p+
Beam energies: (900.0, 900.0) GeV
Run details:
  • $p\bar{p}$ QCD interactions at 1800 GeV. The leading jet is binned from 0--49 GeV, and histos can usually can be filled with a single generator run without kinematic sub-samples.

The original CDF underlying event analysis, based on decomposing each event into a transverse structure with ``toward'', ``away'' and ``transverse'' regions defined relative to the azimuthal direction of the leading jet in the event. Since the toward region is by definition dominated by the hard process, as is the away region by momentum balance in the matrix element, the transverse region is most sensitive to multi-parton interactions. The transverse regions occupy $|\phi| \in [60^\circ, 120^\circ]$ for $|\eta| < 1$. The $p_\perp$ ranges for the leading jet are divided experimentally into the `min-bias' sample from 0--20 GeV, and the `JET20' sample from 18--49 GeV.

Source code: CDF_2001_S4751469.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/TriggerCDFRun0Run1.hh"
#include "Rivet/Projections/ConstLossyFinalState.hh"
//#include "Rivet/Projections/SmearedParticles.hh"

namespace Rivet {


  /// @brief Field-Stuart CDF Run I track-jet underlying event analysis
  ///
  /// @author Andy Buckley
  ///
  /// The "original" underlying event analysis, using a non-standard track-jet algorithm.
  ///
  /// @par Run conditions
  ///
  /// @arg \f$ \sqrt{s} = \f$ 1800 GeV
  /// @arg Run with generic QCD events.
  /// @arg Several \f$ p_\perp^\text{min} \f$ cutoffs are probably required to fill the profile histograms:
  /// @arg \f$ p_\perp^\text{min} = \f$ 0 (min bias), 10, 20 GeV
  class CDF_2001_S4751469 : public Analysis {
  public:

    /// Constructor: cuts on final state are \f$ -1 < \eta < 1 \f$
    /// and \f$ p_T > 0.5 \f$ GeV.
    CDF_2001_S4751469()
      : Analysis("CDF_2001_S4751469"),
        _totalNumTrans2(0), _totalNumTrans5(0), _totalNumTrans30(0),
        _sumWeightsPtLead2(0),_sumWeightsPtLead5(0), _sumWeightsPtLead30(0)
    {    }


    /// @name Analysis methods
    //@{

    // Book histograms
    void init() {
      declare(TriggerCDFRun0Run1(), "Trigger");
      // Randomly discard 8% of charged particles as a kind of hacky detector correction.
      const ChargedFinalState cfs(-1.0, 1.0, 0.5*GeV);
      /// @todo Replace ConstLossyFinalState with SmearedParticles
      const ConstLossyFinalState lossyfs(cfs, 0.08);
      //const SmearedParticles lossyfs(cfs, [](const Particle&){ return 0.92; });

      declare(lossyfs, "FS");
      declare(FastJets(lossyfs, FastJets::TRACKJET, 0.7), "TrackJet");

      _numvsDeltaPhi2 =  bookProfile1D(1, 1, 1);
      _numvsDeltaPhi5 =  bookProfile1D(1, 1, 2);
      _numvsDeltaPhi30 = bookProfile1D(1, 1, 3);
      _pTvsDeltaPhi2 =   bookProfile1D(2, 1, 1);
      _pTvsDeltaPhi5 =   bookProfile1D(2, 1, 2);
      _pTvsDeltaPhi30 =  bookProfile1D(2, 1, 3);

      _numTowardMB = bookProfile1D(3, 1, 1);
      _numTransMB = bookProfile1D(3, 1, 2);
      _numAwayMB = bookProfile1D(3, 1, 3);
      _numTowardJ20 = bookProfile1D(4, 1, 1);
      _numTransJ20 = bookProfile1D(4, 1, 2);
      _numAwayJ20 = bookProfile1D(4, 1, 3);

      _ptsumTowardMB = bookProfile1D(5, 1, 1);
      _ptsumTransMB = bookProfile1D(5, 1, 2);
      _ptsumAwayMB = bookProfile1D(5, 1, 3);
      _ptsumTowardJ20 = bookProfile1D(6, 1, 1);
      _ptsumTransJ20 = bookProfile1D(6, 1, 2);
      _ptsumAwayJ20 = bookProfile1D(6, 1, 3);

      _ptTrans2 = bookHisto1D(7, 1, 1);
      _ptTrans5 = bookHisto1D(7, 1, 2);
      _ptTrans30 = bookHisto1D(7, 1, 3);
    }


    /// Do the analysis
    void analyze(const Event& event) {
      // Trigger
      const bool trigger = apply<TriggerCDFRun0Run1>(event, "Trigger").minBiasDecision();
      if (!trigger) vetoEvent;

      // Get jets, sorted by pT
      const Jets jets = apply<JetAlg>(event, "TrackJet").jetsByPt();
      if (jets.empty()) vetoEvent;
      const Jet jet1 = jets.front();
      const double ptLead = jet1.pT();

      // Cut on highest pT jet: combined 0.5 GeV < pT(lead) < 50 GeV
      if (ptLead/GeV < 0.5) vetoEvent;
      if (ptLead/GeV > 50.0) vetoEvent;

      // Count sum of all event weights in three pT_lead regions
      const double weight = event.weight();
      if (ptLead/GeV > 2.0) _sumWeightsPtLead2 += weight;
      if (ptLead/GeV > 5.0) _sumWeightsPtLead5 += weight;
      if (ptLead/GeV > 30.0) _sumWeightsPtLead30 += weight;

      // Run over tracks
      double ptSumToward(0.0), ptSumAway(0.0), ptSumTrans(0.0);
      size_t numToward(0), numTrans(0), numAway(0);

      // Temporary histos that bin N and pT in dphi
      Profile1D htmp_num_dphi_2(refData(1, 1, 1)), htmp_num_dphi_5(refData(1, 1, 2)), htmp_num_dphi_30(refData(1, 1, 3));
      Profile1D htmp_pt_dphi_2(refData(2, 1, 1)), htmp_pt_dphi_5(refData(2, 1, 2)), htmp_pt_dphi_30(refData(2, 1, 3));

      // Final state charged particles
      /// @todo Non-trackjet track efficiencies are corrected?
      const Particles& tracks = apply<FinalState>(event, "FS").particles();
      for (const Particle& p : tracks) {
        const double dPhi = deltaPhi(p, jet1);
        const double pT = p.pT();

        if (dPhi < PI/3.0) {
          ptSumToward += pT;
          ++numToward;
        }
        else if (dPhi < 2*PI/3.0) {
          ptSumTrans += pT;
          ++numTrans;
          // Fill transverse pT distributions
          if (ptLead/GeV > 2.0) {
            _ptTrans2->fill(pT/GeV, weight);
            _totalNumTrans2 += weight;
          }
          if (ptLead/GeV > 5.0) {
            _ptTrans5->fill(pT/GeV, weight);
            _totalNumTrans5 += weight;
          }
          if (ptLead/GeV > 30.0) {
            _ptTrans30->fill(pT/GeV, weight);
            _totalNumTrans30 += weight;
          }
        }
        else {
          ptSumAway += pT;
          ++numAway;
        }

        // Fill tmp histos to bin event's track Nch & pT in dphi
        const double dPhideg = 180*dPhi/M_PI;
        if (ptLead/GeV > 2.0) {
          htmp_num_dphi_2.fill(dPhideg, 1);
          htmp_pt_dphi_2.fill (dPhideg, pT/GeV);
        }
        if (ptLead/GeV > 5.0) {
          htmp_num_dphi_5.fill(dPhideg, 1);
          htmp_pt_dphi_5.fill (dPhideg, pT/GeV);
        }
        if (ptLead/GeV > 30.0) {
          htmp_num_dphi_30.fill(dPhideg, 1);
          htmp_pt_dphi_30.fill (dPhideg, pT/GeV);
        }
      }

      // Update the "proper" dphi profile histograms
      for (int i = 0; i < 50; i++) { ///< @todo Should really explicitly iterate over nbins for each temp histo
        if (ptLead/GeV > 2.0) {
          const double x2 = htmp_pt_dphi_2.bin(i).xMid();
          const double num2 = (htmp_num_dphi_2.bin(i).numEntries() > 0) ? htmp_num_dphi_2.bin(i).mean() : 0.0;
          const double pt2 = (htmp_num_dphi_2.bin(i).numEntries() > 0) ? htmp_pt_dphi_2.bin(i).mean() : 0.0;
          _numvsDeltaPhi2->fill(x2, num2, weight);
          _pTvsDeltaPhi2->fill(x2, pt2, weight);
        }
        if (ptLead/GeV > 5.0) {
          const double x5 = htmp_pt_dphi_5.bin(i).xMid();
          const double num5 = (htmp_num_dphi_5.bin(i).numEntries() > 0) ? htmp_num_dphi_5.bin(i).mean() : 0.0;
          const double pt5 = (htmp_num_dphi_5.bin(i).numEntries() > 0) ? htmp_pt_dphi_5.bin(i).mean() : 0.0;
          _numvsDeltaPhi5->fill(x5, num5, weight);
          _pTvsDeltaPhi5->fill(x5, pt5, weight);
        }
        if (ptLead/GeV > 30.0) {
          const double x30 = htmp_pt_dphi_30.bin(i).xMid();
          const double num30 = (htmp_num_dphi_30.bin(i).numEntries() > 0) ? htmp_num_dphi_30.bin(i).mean() : 0.0;
          const double pt30 = (htmp_num_dphi_30.bin(i).numEntries() > 0) ? htmp_pt_dphi_30.bin(i).mean() : 0.0;
          _numvsDeltaPhi30->fill(x30, num30, weight);
          _pTvsDeltaPhi30->fill(x30, pt30, weight);
        }
      }

      // Log some event details about pT
      MSG_DEBUG("pT [lead; twd, away, trans] = [" << ptLead << "; "
                << ptSumToward << ", " << ptSumAway << ", " << ptSumTrans << "]");

      // Update the pT profile histograms
      _ptsumTowardMB->fill(ptLead/GeV, ptSumToward/GeV, weight);
      _ptsumTowardJ20->fill(ptLead/GeV, ptSumToward/GeV, weight);

      _ptsumTransMB->fill(ptLead/GeV, ptSumTrans/GeV, weight);
      _ptsumTransJ20->fill(ptLead/GeV, ptSumTrans/GeV, weight);

      _ptsumAwayMB->fill(ptLead/GeV, ptSumAway/GeV, weight);
      _ptsumAwayJ20->fill(ptLead/GeV, ptSumAway/GeV, weight);

      // Log some event details about Nch
      MSG_DEBUG("N [twd, away, trans] = [" << ptLead << "; "
                << numToward << ", " << numTrans << ", " << numAway << "]");

      // Update the N_track profile histograms
      _numTowardMB->fill(ptLead/GeV, numToward, weight);
      _numTowardJ20->fill(ptLead/GeV, numToward, weight);

      _numTransMB->fill(ptLead/GeV, numTrans, weight);
      _numTransJ20->fill(ptLead/GeV, numTrans, weight);

      _numAwayMB->fill(ptLead/GeV, numAway, weight);
      _numAwayJ20->fill(ptLead/GeV, numAway, weight);
    }


    /// Normalize histos
    void finalize() {
      normalize(_ptTrans2, _totalNumTrans2 / _sumWeightsPtLead2);
      normalize(_ptTrans5, _totalNumTrans5 / _sumWeightsPtLead5);
      normalize(_ptTrans30, _totalNumTrans30 / _sumWeightsPtLead30);
    }

    //@}


  private:

    /// Sum total number of charged particles in the trans region, in 3 \f$ p_\perp^\text{lead} \f$ bins.
    double _totalNumTrans2, _totalNumTrans5, _totalNumTrans30;

    /// Sum the total number of events in 3 \f$ p_\perp^\text{lead} \f$ bins.
    double _sumWeightsPtLead2,_sumWeightsPtLead5, _sumWeightsPtLead30;


    /// @name Histogram collections
    //@{

    // The sumpt vs. dphi and Nch vs. dphi histos
    Profile1DPtr _numvsDeltaPhi2, _numvsDeltaPhi5, _numvsDeltaPhi30;
    Profile1DPtr _pTvsDeltaPhi2, _pTvsDeltaPhi5, _pTvsDeltaPhi30;

    /// Profile histograms, binned in the \f$ p_T \f$ of the leading jet, for
    /// the \f$ p_T \f$ sum in the toward, transverse and away regions.
    Profile1DPtr _ptsumTowardMB,  _ptsumTransMB,  _ptsumAwayMB;
    Profile1DPtr _ptsumTowardJ20, _ptsumTransJ20, _ptsumAwayJ20;

    /// Profile histograms, binned in the \f$ p_T \f$ of the leading jet, for
    /// the number of charged particles per jet in the toward, transverse and
    /// away regions.
    Profile1DPtr _numTowardMB,  _numTransMB,  _numAwayMB;
    Profile1DPtr _numTowardJ20, _numTransJ20, _numAwayJ20;

    /// Histogram of \f$ p_T \f$ distribution for 3 different \f$ p_{T1} \f$ IR cutoffs.
    Histo1DPtr _ptTrans2, _ptTrans5, _ptTrans30;
    //@}

  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(CDF_2001_S4751469);

}