Rivet analyses

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

namespace Rivet {


  /// @brief Lambda in Upsilon(1S) decay and nearby continuum
  class MD1_1994_I362599 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(MD1_1994_I362599);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(), "UFS");
      // histos
      book(_weightSum_cont, "TMP/weightSumcont");
      book(_weightSum_Ups1, "TMP/weightSumUps1");
      book(_h_spect, 1, 1, 1);
      for (unsigned int ix = 0; ix < 2; ++ix) {
        for (unsigned int iy = 0; iy < 2; ++iy) {
          book(_mult[ix][iy], "/TMP/MULT_" + toString(ix) + "_" + toString(iy));
        }
      }
    }

    /// 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.abspid();
        if (id == PID::LAMBDA || id == PID::XIMINUS) unstable.push_back(p);
        if (!p.children().empty()) findDecayProducts(p, unstable);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // Find the upsilons
      // First in unstable final state
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      Particles upsilons = ufs.particles(Cuts::pid == 553);
      // continuum
      if (upsilons.empty()) {
        _weightSum_cont->fill();
        // Unstable particles
        size_t nLam = ufs.particles(Cuts::abspid == PID::LAMBDA).size();
        _mult[1][0]->fill(nLam);
      }
      else {
        for (const Particle& ups : upsilons) {
          _weightSum_Ups1->fill();
          Particles unstable;
          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
          // Find the decay products we want
          findDecayProducts(ups, unstable);
          for (const Particle& p : unstable) {
            int id = p.abspid();
            if (id == PID::LAMBDA) {
              double xp = 2. * boost.transform(p.momentum()).p3().mod() / ups.mass();
              _h_spect->fill(xp);
              _mult[0][0]->fill();
            }
            else if (id == PID::XIMINUS) {
              _mult[0][1]->fill();
            }
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      if (_weightSum_Ups1->val() > 0.) {
        scale(_h_spect, 1. / *_weightSum_Ups1);
        for (size_t iy = 0; iy < 2; ++iy) {
          BinnedEstimatePtr<string> est;
          book(est, 2 + iy * 2, 1, 1);
          if (_weightSum_Ups1->val() > 0.) {
            scale(_mult[0][iy], 1. / *_weightSum_Ups1);
            est->bin(1).set(_mult[0][iy]->val(), _mult[0][iy]->err());
          }
        }
      }
      if (_weightSum_cont->val() > 0.) {
        scale(_mult[1][0], 1. / *_weightSum_cont);
        Estimate1DPtr est;
        book(est, 3, 1, 1);
        est->bin(1).set(_mult[1][0]->val(), _mult[1][0]->err());
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_spect;
    CounterPtr _weightSum_cont, _weightSum_Ups1;
    CounterPtr _mult[2][2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(MD1_1994_I362599);

}