Rivet analyses

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

namespace Rivet {


  /// @brief kaon production at low energies
  class PLUTO_1981_I165122 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(PLUTO_1981_I165122);


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

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

      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      // // Book histograms
      book(_c_hadrons, "/TMP/sigma_hadrons", refData<YODA::BinnedEstimate<string>>(1, 1, 1));
      for (size_t ix = 0; ix < 2; ++ix) {
        book(_c_muons[ix], "/TMP/sigma_muons_" + toString(ix),
             refData<YODA::BinnedEstimate<string>>(1 + 2 * ix, 1, 1));
        book(_c_kaons[ix], "/TMP/sigma_kaons_" + toString(ix),
             refData<YODA::BinnedEstimate<string>>(1 + 2 * ix, 1, 1));
        for (const string& en : _c_muons[ix].binning().edges<0>()) {
          const size_t idx = en.find("-");
          if (idx != string::npos) {
            const double emin = stod(en.substr(0, idx));
            const double emax = stod(en.substr(idx + 1, string::npos));
            if (inRange(sqrtS() / GeV, emin, emax)) {
              _sqs[ix] = en;
              break;
            }
          }
          else {
            const double eval = stod(en) * GeV;
            if (isCompatibleWithSqrtS(eval)) {
              _sqs[ix] = en;
              break;
            }
          }
        }
      }
      raiseBeamErrorIf(_sqs[0].empty() && _sqs[1].empty());
      size_t ih = 3;
      for (const double eval : {30.0, 9.4, 9.456}) {
        const string label = toString(round(eval / MeV));
        if (isCompatibleWithSqrtS(eval)) _sqs[2] = label;
        book(_h[label], ++ih, 1, 1);
      }
      book(_c_hadronsY, "TMP/nUps");
    }

    /// Recursively walk the decay tree to find decay products of @a p
    void findDecayProducts(const Particle& mother, Particles& kaons, Particles& stable) const {
      for (const Particle& p : mother.children()) {
        const int id = p.pid();
        if (id == 130 || id == 310) {
          kaons += p;
        }
        if (id == 111 or p.children().empty())
          stable += p;
        else {
          findDecayProducts(p, kaons, stable);
        }
      }
    }


    /// 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 = 0.5 * (beams.first.p3().mod() + beams.second.p3().mod());
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
      // 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");
        // final state particles
        const FinalState& fs = apply<FinalState>(event, "FS");
        map<long, int> nCount;
        int ntotal(0);
        for (const Particle& p : fs.particles()) {
          nCount[p.pid()] += 1;
          ++ntotal;
        }
        if (nCount[-13] == 1 and nCount[13] == 1 && ntotal == 2 + nCount[22]) {
          // mu+mu- + photons
          for (size_t ix = 0; ix < 2; ++ix) {
            if (!_sqs[ix].empty()) _c_muons[ix]->fill(_sqs[ix]);
          }
        }
        else { // everything else
          if (!_sqs[0].empty()) _c_hadrons->fill(_sqs[0]);
        }
        // unstable particles
        for (const Particle& p : ufs.particles(Cuts::pid == 130 or Cuts::pid == 310)) {
          if (!_sqs[2].empty()) {
            const double xp = p.p3().mod() / meanBeamMom;
            _h[_sqs[2]]->fill(xp);
          }
          for (size_t ix = 0; ix < 2; ++ix) {
            if (!_sqs[ix].empty()) _c_kaons[ix]->fill(_sqs[ix]);
          }
        }
      }
      else {
        MSG_DEBUG("Upsilons found => resonance event");
        for (const Particle& ups : upsilons) {
          _c_hadronsY->fill();
          Particles kaons, stable;
          // Find the decay products we want
          findDecayProducts(ups, kaons, stable);
          // boost to rest frame (if required)
          LorentzTransform cms_boost;
          if (ups.p3().mod() > 1 * MeV) {
            cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.mom().betaVec());
          }
          const double mass = ups.mass();

          map<long, int> nCount;
          int ntotal(0);
          for (const Particle& p : stable) {
            nCount[p.pid()] += 1;
            ++ntotal;
          }
          for (const Particle& kaon : kaons) {
            const FourMomentum p2 = cms_boost.transform(kaon.mom());
            const double xp = 2. * p2.p3().mod() / mass;
            _h["9456"s]->fill(xp);
            _c_kaons[0]->fill("9.45 - 9.466"s);
            _c_kaons[1]->fill("9.45 - 9.456"s);
          }
          // mu+mu- + photons
          if (nCount[-13] == 1 and nCount[13] == 1 && ntotal == 2 + nCount[22]) {
            for (size_t ix = 0; ix < 2; ++ix) {
              _c_muons[ix]->fill("9.45 - 9.466"s);
            }
          }
          // everything else
          else {
            _c_hadrons->fill("9.45 - 9.466"s);
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      BinnedEstimatePtr<string> ratio;
      book(ratio, 1, 1, 1);
      divide(_c_kaons[0], _c_muons[0], ratio);
      book(ratio, 2, 1, 1);
      divide(_c_kaons[0], _c_hadrons, ratio);
      book(ratio, 3, 1, 1);
      divide(_c_kaons[1], _c_muons[1], ratio);
      // normalize the spectra if required
      for (auto& item : _h) {
        if (item.first == "9456"s) {
          if (_c_hadronsY->val()) scale(item.second, 1.0 / *_c_hadronsY);
        }
        else {
          // beam energy not well defined during merging!
          scale(item.second, sqr(sqrtS()) * crossSection() / microbarn / sumOfWeights());
        }
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _c_hadrons, _c_muons[2], _c_kaons[2];
    map<string, Histo1DPtr> _h;
    CounterPtr _c_hadronsY;
    string _sqs[3];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(PLUTO_1981_I165122);


}