Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/Sphericity.hh"
#include "Rivet/Projections/Thrust.hh"

namespace Rivet {


  /// @brief event shapes at 35 GeV
  class TASSO_1988_I263859 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1988_I263859);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      const ChargedFinalState cfs;
      declare(cfs, "CFS");

      // Thrust and sphericity
      declare(Beam(), "Beams");
      declare(Thrust(cfs), "Thrust");
      declare(Sphericity(cfs), "Sphericity");

      // Book histograms
      book(_h_sphericity, 1, 1, 1);
      book(_h_aplanarity, 2, 1, 1);
      book(_h_thrust, 3, 1, 1);
      book(_h_pTin2, 4, 1, 1);
      book(_h_pTout2, 5, 1, 1);
      book(_h_ncharged, 6, 1, 1);
      book(_h_pTin, 7, 1, 1);
      book(_h_pTout, 8, 1, 1);
      book(_h_pT, 9, 1, 1);
      book(_h_x, 10, 1, 1);
      book(_h_rap, 11, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");

      // Get beams and average beam momentum
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double meanBeamMom = (beams.first.p3().mod() + beams.second.p3().mod()) / 2.0;
      const Thrust& thrust = apply<Thrust>(event, "Thrust");
      const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");

      _h_sphericity->fill(sphericity.sphericity());
      _h_aplanarity->fill(sphericity.aplanarity());
      _h_thrust->fill(thrust.thrust());

      double pTin2sum(0.), pTout2sum(0.);
      for (const Particle& p : cfs.particles()) {
        // Get momentum and energy of each particle.
        const Vector3 mom3 = p.p3();
        const double energy = p.E();
        // Scaled momenta.
        const double mom = mom3.mod();
        const double scaledMom = mom / meanBeamMom;
        _h_x->fill(scaledMom);

        const double momS = dot(sphericity.sphericityAxis(), mom3);
        const double pTinS = dot(mom3, sphericity.sphericityMajorAxis());
        const double pToutS = dot(mom3, sphericity.sphericityMinorAxis());
        const double pT = sqrt(pow(pTinS, 2) + pow(pToutS, 2));
        const double rapidityS = 0.5 * std::log((energy + momS) / (energy - momS));

        pTin2sum += sqr(pTinS);
        pTout2sum += sqr(pToutS);

        _h_pTin->fill(abs(pTinS) / GeV);
        _h_pTout->fill(abs(pToutS) / GeV);
        _h_pT->fill(pT / GeV);
        _h_rap->fill(abs(rapidityS));
      }
      unsigned int nCharged = cfs.particles().size();
      _h_ncharged->fill(nCharged);
      if (nCharged) {
        _h_pTin2->fill(pTin2sum / nCharged);
        _h_pTout2->fill(pTout2sum / nCharged);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_sphericity, 1. / sumOfWeights());
      scale(_h_aplanarity, 1. / sumOfWeights());
      scale(_h_thrust, 1. / sumOfWeights());
      scale(_h_pTin2, 1. / sumOfWeights());
      scale(_h_pTout2, 1. / sumOfWeights());
      scale(_h_ncharged, 1000. / sumOfWeights());
      scale(_h_pTin, 1. / sumOfWeights());
      scale(_h_pTout, 1. / sumOfWeights());
      scale(_h_pT, 1. / sumOfWeights());
      scale(_h_x, 1. / sumOfWeights());
      scale(_h_rap, 1. / sumOfWeights());
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_sphericity, _h_aplanarity, _h_thrust, _h_pTin2, _h_pTout2, _h_pTin, _h_pTout, _h_pT, _h_x,
        _h_rap;
    BinnedHistoPtr<int> _h_ncharged;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(TASSO_1988_I263859);

}