Rivet analyses

Measurement of R and DD̄ cross section between 3.67 and 3.872 GeV

Experiment: MARKII (SPEAR)

Inspire ID: 143939

Status: VALIDATED

Authors: - Peter Richardson

References: - Schindler, R.H. PhD Thesis, 1979

Beams: e- e+

Beam energies: (1.8, 1.8); (1.8, 1.8); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9); (1.9, 1.9)GeV

Run details: - e+ e- to hadrons and e+ e- to mu+ mu- (for normalization)

Measurement of R and the DD̄ cross section in e+e− collisions between 3.67 and 3.872 GeV The individual hadronic and muonic cross sections are also outputted to the yoda file so that ratio R can be recalcuated if runs are combined.

Source code:MARKII_1979_I143939.cc

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

namespace Rivet {


  /// @brief Add a short analysis description here
  class MARKII_1979_I143939 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1979_I143939);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(FinalState(), "FS");
      declare(UnstableParticles(), "UFS");
      book(_c_hadrons, "/TMP/sigma_hadrons", refData<YODA::BinnedEstimate<string>>(2,1,1));
      book(_c_muons,   "/TMP/sigma_muons"  , refData<YODA::BinnedEstimate<string>>(2,1,1));
      book(_c_DD, 3, 1, 1);
      for (const string& en : _c_hadrons.binning().edges<0>()) {
        double eval = stod(en)*GeV;
        if (isCompatibleWithSqrtS(eval)) {
          _sqs = en; break;
        }
      }
      raiseBeamErrorIf(_sqs.empty());
    }

    void findChildren(const Particle& p, map<long,int>& nRes, int &ncount) const {
      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");
      // total hadronic and muonic cross sections
      map<long,int> nCount;
      int ntotal(0);
      for (const Particle& p : fs.particles()) {
        nCount[p.pid()] += 1;
        ++ntotal;
      }
      if (nCount[-13]==1 && nCount[13]==1 && ntotal==2+nCount[22]) {
        // mu+mu- + photons
        _c_muons->fill(_sqs);
      }
      else  _c_hadrons->fill(_sqs); // everything else
      // identified final state with D mesons
      const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
      for (unsigned int ix=0; ix<ufs.particles().size(); ++ix) {
        bool matched = false;
        const Particle& p1 = ufs.particles()[ix];
        int id1 = abs(p1.pid());
        if (id1 != 411 && id1 != 421) continue;
        // check fs
        bool fs = true;
        for (const Particle & child : p1.children()) {
          if (child.pid()==p1.pid()) {
            fs = false; break;
          }
        }
        if (!fs) continue;
        // find the children
        map<long,int> nRes = nCount;
        int ncount = ntotal;
        findChildren(p1,nRes,ncount);
        // loop over the other fs particles
        for (size_t iy=ix+1; iy<ufs.particles().size(); ++iy) {
          const Particle& p2 = ufs.particles()[iy];
          fs = true;
          for (const Particle& child : p2.children()) {
            if (child.pid()==p2.pid()) {
              fs = false; break;
            }
          }
          if (!fs) continue;
          if (p2.pid()/abs(p2.pid())==p1.pid()/abs(p1.pid())) continue;
          int id2 = abs(p2.pid());
          if (id2 != 411 && id2 != 421) continue;
          if (!p2.parents().empty() && p2.parents()[0].pid()==p1.pid()) continue;
          map<long,int> nRes2 = nRes;
          int ncount2 = ncount;
          findChildren(p2,nRes2,ncount2);
          if (ncount2!=0) continue;
          matched=true;
          for (const auto& val : nRes2) {
            if (val.second!=0) {
              matched = false;
              break;
            }
          }
          if (matched) {
            _c_DD->fill(_sqs); break;
          }
        }
        if (matched) break;
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double fact = crossSection()/ sumOfWeights() /nanobarn;
      BinnedEstimatePtr<string> mult;
      book(mult, 2, 1, 1);
      divide(_c_hadrons, _c_muons, mult);
      scale(_c_DD, fact);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _c_hadrons, _c_muons, _c_DD;
    string _sqs = "";
    /// @}


  };


  RIVET_DECLARE_PLUGIN(MARKII_1979_I143939);


}