Rivet analyses

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

namespace Rivet {


  /// @brief Cross section for D0 D- pi+ +c.c
  class BELLE_2008_I759073 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2008_I759073);


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

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

      // Initialise and register projections
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_nD0, "/TMP/nD0");
    }

    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
      for (const Particle &child : p.children()) {
    if(child.children().empty()) {
      nRes[child.pid()]-=1;
      --ncount;
    }
    else
      findChildren(child,nRes,ncount);
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      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;
      }
      const FinalState& ufs = apply<FinalState>(event, "UFS");


      for(unsigned int ix=0;ix<ufs.particles().size();++ix) {
    const Particle& p1 = ufs.particles()[ix];
    if(abs(p1.pid())!=421) continue;
    map<long,int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1,nRes,ncount);
    bool matched=false;
    int id2 = p1.pid()>0 ? -411 :  411;
    int ipi = p1.pid()>0 ?  211 : -211;
    for(unsigned int iy=0;iy<ufs.particles().size();++iy) {
      if(ix==iy) continue;
      const Particle& p2 = ufs.particles()[iy];
      if(p2.pid()!=id2) continue;
      map<long,int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2,nRes2,ncount2);
      if(ncount2!=1) continue;
      matched=true;
      for(auto const & val : nRes2) {
        if(val.first==ipi) {
          if(val.second!=1) {
        matched = false;
        break;
          }
        }
        else if(val.second!=0) {
          matched = false;
          break;
        }
      }
      if(matched) break;
    }
    if(matched)
      _nD0->fill();
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double sigma = _nD0->val();
      double error = _nD0->err();
      sigma *= crossSection()/ sumOfWeights() /nanobarn;
      error *= crossSection()/ sumOfWeights() /nanobarn;
      Estimate1DPtr mult;
      book(mult, 1, 1, 1);
      for (auto& b : mult->bins()) {
        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
          b.set(sigma, error);
        }
      }
    }

    /// @}

    /// @name Histograms
    /// @{
    CounterPtr _nD0;
    /// @}

  };


  RIVET_DECLARE_PLUGIN(BELLE_2008_I759073);


}