H1_1994_S2919893.cc

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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Math/Constants.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/DISKinematics.hh"

namespace Rivet {


  /// @brief H1 energy flow and charged particle spectra
  /// @author Peter Richardson
  /// Based on the equivalent HZTool analysis
  class H1_1994_S2919893 : public Analysis {
  public:

    /// Constructor
    H1_1994_S2919893()
      : Analysis("H1_1994_S2919893")
    {

      // Initialise member variables
      _w77  = make_pair(0.0, 0.0);
      _w122 = make_pair(0.0, 0.0);
      _w169 = make_pair(0.0, 0.0);
      _w117 = make_pair(0.0, 0.0);
      _wEnergy = make_pair(0.0, 0.0);
    }



    /// @name Analysis methods
    //@{

    void analyze(const Event& event) {
      const FinalState& fs = applyProjection<FinalState>(event, "FS");
      const DISKinematics& dk = applyProjection<DISKinematics>(event, "Kinematics");
      const DISLepton& dl = applyProjection<DISLepton>(event,"Lepton");

      // Get the DIS kinematics
      double x  = dk.x();
      double w2 = dk.W2();
      double w = sqrt(w2);

      // Momentum of the scattered lepton
      FourMomentum leptonMom = dl.out().momentum();
      double ptel = pT(leptonMom);
      double enel = leptonMom.E();
      double thel = leptonMom.angle(dk.beamHadron().momentum())/degree;

      // Extract the particles other than the lepton
      Particles particles;
      particles.reserve(fs.particles().size());
      const GenParticle* dislepGP = dl.out().genParticle();
      foreach (const Particle& p, fs.particles()) {
        const GenParticle* loopGP = p.genParticle();
        if (loopGP == dislepGP) continue;
        particles.push_back(p);
      }

      // Cut on the forward energy
      double efwd = 0.0;
      foreach (const Particle& p, particles) {
        double th = p.momentum().angle(dk.beamHadron().momentum())/degree;
        if (th > 4.4 && th < 15.) {
          efwd += p.momentum().E();
        }
      }

      // Apply the cuts
      // Lepton energy and angle, w2 and forward energy
      MSG_DEBUG("enel/GeV = " << enel/GeV << ", thel = " << thel
                << ", w2 = " << w2 << ", efwd/GeV = " << efwd/GeV);
      bool cut = enel/GeV > 14. && thel > 157. && thel < 172.5 && w2 >= 3000. && efwd/GeV > 0.5;
      if (!cut) vetoEvent;

      // Weight of the event
      const double weight = event.weight();
      // weights for x<1e-3 and x>1e-3
      if (x < 1e-3) {
        _wEnergy.first  += weight;
      } else {
        _wEnergy.second += weight;
      }

      // Boost to hadronic CM
      const LorentzTransform hcmboost = dk.boostHCM();
      // Loop over the particles
      long ncharged(0);
      for (size_t ip1 = 0; ip1 < particles.size(); ++ip1) {
        const Particle& p = particles[ip1];

        double th = p.momentum().angle(dk.beamHadron().momentum()) / degree;
        // Boost momentum to lab
        const FourMomentum hcmMom = hcmboost.transform(p.momentum());
        // Angular cut
        if (th <= 4.4) continue;

        // Energy flow histogram
        double et = fabs(Et(hcmMom));
        double eta = hcmMom.pseudorapidity();
        if (x < 1e-3) {
          _histEnergyFlowLowX ->fill(eta, et*weight);
        } else {
          _histEnergyFlowHighX->fill(eta, et*weight);
        }
        if (PID::threeCharge(p.pdgId()) != 0) {
          /// @todo Use units in w comparisons... what are the units?
          if (w > 50. && w <= 200.) {
            double xf= 2 * hcmMom.z() / w;
            double pt2 = pT2(hcmMom);
            if (w > 50. && w <= 100.) {
              _histSpectraW77 ->fill(xf, weight);
            } else if (w > 100. && w <= 150.) {
              _histSpectraW122->fill(xf, weight);
            } else if (w > 150. && w <= 200.) {
              _histSpectraW169->fill(xf, weight);
            }
            _histSpectraW117->fill(xf, weight);
            /// @todo Is this profile meant to be filled with 2 weight factors?
            _histPT2->fill(xf, pt2*weight/GeV2, weight);
            ++ncharged;
          }
        }


        // Energy-energy correlation
        if (th <= 8.) continue;
        double phi1 = p.momentum().azimuthalAngle(ZERO_2PI);
        double eta1 = p.momentum().pseudorapidity();
        double et1 = fabs(Et(p.momentum()));
        for (size_t ip2 = ip1+1; ip2 < particles.size(); ++ip2) {
          const Particle& p2 = particles[ip2];

          //double th2 = beamAngle(p2.momentum(), order);
          double th2 = p2.momentum().angle(dk.beamHadron().momentum()) / degree;
          if (th2 <= 8.) continue;
          double phi2 = p2.momentum().azimuthalAngle(ZERO_2PI);

          /// @todo Use angle function
          double deltaphi = phi1 - phi2;
          if (fabs(deltaphi) > PI)
            deltaphi = fabs(fabs(deltaphi) - TWOPI);
          double eta2 = p2.momentum().pseudorapidity();
          double omega = sqrt(sqr(eta1-eta2) + sqr(deltaphi));
          double et2 = fabs(Et(p2.momentum()));
          double wt = et1*et2 / sqr(ptel) * weight;
          if(x < 1e-3) {
            _histEECLowX ->fill(omega, wt);
          } else {
            _histEECHighX->fill(omega,wt);
          }
        }
      }

      // Factors for normalization
      if (w > 50. && w <= 200.) {
        if (w <= 100.) {
          _w77.first  += ncharged*weight;
          _w77.second += weight;
        } else if (w <= 150.) {
          _w122.first  += ncharged*weight;
          _w122.second += weight;
        } else {
          _w169.first  += ncharged*weight;
          _w169.second += weight;
        }
        _w117.first  += ncharged*weight;
        _w117.second += weight;
      }
    }



    void init() {
      // Projections
      addProjection(DISLepton(), "Lepton");
      addProjection(DISKinematics(), "Kinematics");
      addProjection(FinalState(), "FS");

      // Histos
      _histEnergyFlowLowX =  bookHisto1D(1, 1, 1);
      _histEnergyFlowHighX = bookHisto1D(1, 1, 2);

      _histEECLowX = bookHisto1D(2, 1, 1);
      _histEECHighX = bookHisto1D(2, 1, 2);

      _histSpectraW77 = bookHisto1D(3, 1, 1);
      _histSpectraW122 = bookHisto1D(3, 1, 2);
      _histSpectraW169 = bookHisto1D(3, 1, 3);
      _histSpectraW117 = bookHisto1D(3, 1, 4);

      _histPT2 = bookProfile1D(4, 1, 1);
    }


    /// Finalize
    void finalize() {
      // Normalize inclusive single particle distributions to the average number
      // of charged particles per event.
      double avgNumParts = _w77.first/_w77.second;
      normalize(_histSpectraW77, avgNumParts);

      avgNumParts = _w122.first/_w122.second;
      normalize(_histSpectraW122, avgNumParts);

      avgNumParts = _w169.first/_w169.second;
      normalize(_histSpectraW169, avgNumParts);

      avgNumParts = _w117.first/_w117.second;
      normalize(_histSpectraW117, avgNumParts);

      scale(_histEnergyFlowLowX , 1./_wEnergy.first );
      scale(_histEnergyFlowHighX, 1./_wEnergy.second);

      scale(_histEECLowX , 1./_wEnergy.first );
      scale(_histEECHighX, 1./_wEnergy.second);
    }


    //@}


  private:

    /**
     *  Polar angle with right direction of the beam
     */
    inline double beamAngle(const FourVector& v, const bool & order) {
      double thel = v.polarAngle()/degree;
      if(thel<0.) thel+=180.;
      if(!order) thel = 180.-thel;
      return thel;
    }

    /// @name Histograms
    //@{
    Histo1DPtr _histEnergyFlowLowX;
    Histo1DPtr _histEnergyFlowHighX;
    Histo1DPtr _histEECLowX;
    Histo1DPtr _histEECHighX;
    Histo1DPtr _histSpectraW77;
    Histo1DPtr _histSpectraW122;
    Histo1DPtr _histSpectraW169;
    Histo1DPtr _histSpectraW117;
    Profile1DPtr _histPT2;
    //@}

    /// @name storage of weight to calculate averages for normalisation
    //@{
    pair<double,double> _w77,_w122,_w169,_w117,_wEnergy;
    //@}
  };



  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(H1_1994_S2919893);

}