Rivet analyses

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

namespace Rivet {


  /// @brief ARGUS D0, D+, D*+ production
  class ARGUS_1991_I315059 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1991_I315059);


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

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(), "UFS");
      declare(Beam(), "Beams");

      // Book histograms
      book(_n_D0, 1, 1, 1);
      book(_n_Dp, 1, 1, 2);
      book(_n_DStar, 1, 1, 3);

      book(_h_x_D0, 2, 1, 1);
      book(_h_x_Dp, 3, 1, 1);
      book(_h_x_DStar, 4, 1, 1);

      book(_h_p_D0, 5, 1, 1);
      book(_h_p_Dp, 6, 1, 1);
      book(_h_p_DStar, 7, 1, 1);

      book(_c_cont, "/TMP/c_cont");
      book(_c_ups, "/TMP/c_ups");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // 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;
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
      // Find the Upsilon(4S) among the unstables
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      Particles upsilons = ufs.particles(Cuts::pid == 300553);
      // Continuum
      if (upsilons.empty()) {
        _c_cont->fill();
        MSG_DEBUG("No Upsilons found => continuum event");
        for (const Particle& p :
             ufs.particles(Cuts::abspid == 411 or Cuts::abspid == 421 or Cuts::abspid == 413)) {
          double xp = p.p3().mod() / sqrt(sqr(meanBeamMom) - sqr(p.mass()));
          if (p.abspid() == 421) {
            _h_x_D0->fill(xp);
            _n_D0->fill(Ecms);
          }
          else if (p.abspid() == 411) {
            _h_x_Dp->fill(xp);
            _n_Dp->fill(Ecms);
          }
          else if (p.abspid() == 413) {
            _h_x_DStar->fill(xp);
            _n_DStar->fill(Ecms);
          }
        }
      }
      // upsilon decay
      else {
        for (const Particle& ups : upsilons) {
          _c_ups->fill();
          Particles unstable;
          // Find the decay products we want
          findDecayProducts(ups, unstable);
          // boost to rest frame (if required)
          LorentzTransform cms_boost;
          if (ups.p3().mod() > 1 * MeV) {
            cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
          }
          for (const Particle& p : unstable) {
            const FourMomentum p2 = cms_boost.transform(p.momentum());
            double modp = p2.p3().mod();
            if (p.abspid() == 421) {
              _h_p_D0->fill(modp);
            }
            else if (p.abspid() == 411) {
              _h_p_Dp->fill(modp);
            }
            else if (p.abspid() == 413) {
              _h_p_DStar->fill(modp);
            }
          }
        }
      }
    }

    /// 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 == 411 || id == 421) {
          unstable.push_back(p);
        }
        else if (id == 413) {
          unstable.push_back(p);
          findDecayProducts(p, unstable);
        }
        else if (!p.children().empty()) {
          findDecayProducts(p, unstable);
        }
      }
    }

    /// Normalise histograms etc., after the run
    void finalize() {
      // brs for the decays used (PDG 2018)
      double brD0 = 0.0389;
      double brDp = 0.0898;
      double brDStar = 0.677;
      if (_c_cont->numEntries() != 0) {
        scale(_n_D0, 1. / sumOfWeights() * crossSection() / nanobarn);
        scale(_n_Dp, 1. / sumOfWeights() * crossSection() / nanobarn);
        scale(_n_DStar, 1. / sumOfWeights() * crossSection() / nanobarn);
        scale(_h_x_D0, brD0 / sumOfWeights() * crossSection() / nanobarn * sqr(sqrtS()));
        scale(_h_x_Dp, brDp / sumOfWeights() * crossSection() / nanobarn * sqr(sqrtS()));
        scale(_h_x_DStar, brD0 * brDStar / sumOfWeights() * crossSection() / nanobarn * sqr(sqrtS()));
      }
      if (_c_ups->numEntries() != 0) {
        scale(_h_p_D0, 1e3 * 0.5 * brD0 / *_c_ups);
        scale(_h_p_Dp, 1e3 * 0.5 * brDp / *_c_ups);
        scale(_h_p_DStar, 1e3 * 0.5 * brD0 * brDStar / *_c_ups);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _n_D0, _n_Dp, _n_DStar;
    Histo1DPtr _h_x_D0, _h_x_Dp, _h_x_DStar;
    Histo1DPtr _h_p_D0, _h_p_Dp, _h_p_DStar;
    CounterPtr _c_cont, _c_ups;
    const string Ecms = "10.6";
    /// @}
  };


  RIVET_DECLARE_PLUGIN(ARGUS_1991_I315059);


}