Rivet analyses

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief pi0 and eta at Upsilon 1 and continuum
  class CRYSTAL_BALL_1991_I297905 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CRYSTAL_BALL_1991_I297905);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      declare(UnstableParticles(), "UFS");
      // Book histograms
      book(_h_cont_pi[0], 3, 1, 1);
      book(_h_cont_pi[1], 3, 1, 2);
      book(_h_ups1_pi, 4, 1, 1);
      book(_h_cont_eta[0], 5, 1, 1);
      book(_h_cont_eta[1], 5, 1, 2);
      book(_h_ups1_eta, 6, 1, 1);
      // counters
      book(_n_Cont[0], 1, 1, 1);
      book(_n_Cont[1], 1, 1, 2);
      book(_n_Ups[0], 2, 1, 1);
      book(_n_Ups[1], 2, 1, 2);
      book(_weightSum_cont, "/TMP/weightSum_cont");
      book(_weightSum_Ups1, "/TMP/weightSum_Ups1");
    }

    /// Recursively walk the decay tree to find decay products of @a p
    void findDecayProducts(Particle mother, Particles& unstable) {
      for (const Particle& p : mother.children()) {
        const int id = p.pid();
        if (id == 111 or id == 221) {
          unstable.push_back(p);
        }
        if (!p.children().empty()) {
          findDecayProducts(p, unstable);
        }
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Find the Upsilons among the unstables
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      Particles upsilons = ufs.particles(Cuts::pid == 553);
      // Continuum
      if (upsilons.empty()) {
        MSG_DEBUG("No Upsilons found => continuum event");
        _weightSum_cont->fill();
        unsigned int npi0(0), neta(0);
        for (const Particle& p : ufs.particles(Cuts::pid == 111 or Cuts::pid == 221)) {
          const int id = p.pid();
          const double xp = 2. * p.E() / sqrtS();
          const double beta = p.p3().mod() / p.E();
          if (id == 111) {
            ++npi0;
            for (unsigned int ix = 0; ix < 2; ++ix) {
              _h_cont_pi[ix]->fill(xp, 1. / beta);
            }
          }
          else {
            ++neta;
            for (unsigned int ix = 0; ix < 2; ++ix) {
              _h_cont_eta[ix]->fill(xp, 1. / beta);
            }
          }
        }
        _n_Cont[0]->fill(sqrtS(), npi0);
        _n_Cont[1]->fill(sqrtS(), neta);
      }
      // Upsilon(s) found
      else {
        MSG_DEBUG("Upsilons found => resonance event");
        for (const Particle& ups : upsilons) {
          _weightSum_Ups1->fill();
          Particles unstable;
          // Find the decay products we want
          findDecayProducts(ups, unstable);
          LorentzTransform cms_boost;
          if (ups.p3().mod() > 1 * MeV) {
            cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
          }
          const double mass = ups.mass();
          // loop over decay products
          for (const Particle& p : unstable) {
            const int id = p.pid();
            const FourMomentum p2 = cms_boost.transform(p.momentum());
            const double xp = 2. * p2.E() / mass;
            const double beta = p2.p3().mod() / p2.E();
            if (id == 111) {
              _n_Ups[0]->fill(Ecm);
              _h_ups1_pi->fill(xp, 1. / beta);
            }
            else if (id == 221) {
              _n_Ups[1]->fill(Ecm);
              _h_ups1_eta->fill(xp, 1. / beta);
            }
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // Scale histos
      if (_weightSum_cont->val() > 0.) {
        scale(_h_cont_pi[0], 1. / *_weightSum_cont);
        scale(_h_cont_pi[1], sqr(sqrtS()) * crossSection() / microbarn / sumOfWeights());
        scale(_h_cont_eta[0], 1. / *_weightSum_cont);
        scale(_h_cont_eta[1], sqr(sqrtS()) * crossSection() / microbarn / sumOfWeights());
      }
      if (_weightSum_Ups1->val() > 0.) {
        scale(_h_ups1_pi, 1. / *_weightSum_Ups1);
        scale(_h_ups1_eta, 1. / *_weightSum_Ups1);
        scale(_n_Ups[0], 1. / *_weightSum_Ups1);
        scale(_n_Ups[1], 1. / *_weightSum_Ups1);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_cont_pi[2], _h_ups1_pi;
    Histo1DPtr _h_cont_eta[2], _h_ups1_eta;
    BinnedHistoPtr<string> _n_Ups[2];
    Profile1DPtr _n_Cont[2];
    CounterPtr _weightSum_cont, _weightSum_Ups1;
    const string Ecm = "9.8";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(CRYSTAL_BALL_1991_I297905);

}